Merge pull request #123 from AeneasVerif/son/clean

Cleanup the code in preparation of the nested loops

80 files changed, 1989 insertions, 1997 deletions

diff --git a/backends/coq/Primitives.v b/backends/coq/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/backends/coq/Primitives.v
+++ b/backends/coq/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/backends/fstar/Primitives.fst b/backends/fstar/Primitives.fst
index fca80829..acdb09dc 100644
--- a/backends/fstar/Primitives.fst
+++ b/backends/fstar/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/backends/lean/Base/Diverge/Base.lean b/backends/lean/Base/Diverge/Base.lean
index 7521eecc..0f20125f 100644
--- a/backends/lean/Base/Diverge/Base.lean
+++ b/backends/lean/Base/Diverge/Base.lean
@@ -167,7 +167,7 @@ namespace Fix
     match x1 with
     | div => True
     | fail _ => x2 = x1
-    | ret _ => x2 = x1 -- TODO: generalize
+    | ok _ => x2 = x1 -- TODO: generalize
 
   -- Monotonicity relation over monadic arrows (i.e., Kleisli arrows)
   def karrow_rel (k1 k2 : (x:a) → Result (b x)) : Prop :=
@@ -386,7 +386,7 @@ namespace Fix
       have Hgeq := Hgmono Hffmono
       simp [result_rel] at Hgeq
       cases Heq: g (fix_fuel n k) <;> rename_i y <;> simp_all
-      -- Remains the .ret case
+      -- Remains the .ok case
       -- Use Hdiv to prove that: ∀ n, h y (fix_fuel n f) = div
       -- We do this in two steps: first we prove it for m ≥ n
       have Hhdiv: ∀ m, h y (fix_fuel m k) = .div := by
@@ -507,7 +507,7 @@ namespace FixI
      specific case.
 
      Remark: the index designates the function in the mutually recursive group
-     (it should be a finite type). We make the return type depend on the input
+     (it should be a finite type). We make the output type depend on the input
      type because we group the type parameters in the input type.
    -/
   open Primitives Fix
@@ -943,7 +943,7 @@ namespace Ex1
     match ls with
     | [] => .fail .panic
     | hd :: tl =>
-      if i = 0 then .ret hd
+      if i = 0 then .ok hd
       else k (tl, i - 1)
 
   theorem list_nth_body_is_valid: ∀ k x, is_valid_p k (λ k => @list_nth_body a k x) := by
@@ -960,7 +960,7 @@ namespace Ex1
       match ls with
       | [] => .fail .panic
       | hd :: tl =>
-        if i = 0 then .ret hd
+        if i = 0 then .ok hd
         else list_nth tl (i - 1)
     := by
     have Heq := is_valid_fix_fixed_eq (@list_nth_body_is_valid a)
@@ -981,11 +981,11 @@ namespace Ex2
     match ls with
     | [] => .fail .panic
     | hd :: tl =>
-      if i = 0 then .ret hd
+      if i = 0 then .ok hd
       else
         do
           let y ← k (tl, i - 1)
-          .ret y
+          .ok y
 
   theorem list_nth_body_is_valid: ∀ k x, is_valid_p k (λ k => @list_nth_body a k x) := by
     intro k x
@@ -1002,11 +1002,11 @@ namespace Ex2
        match ls with
        | [] => .fail .panic
        | hd :: tl =>
-         if i = 0 then .ret hd
+         if i = 0 then .ok hd
          else
            do
              let y ← list_nth tl (i - 1)
-             .ret y)
+             .ok y)
     := by
     have Heq := is_valid_fix_fixed_eq (@list_nth_body_is_valid a)
     simp [list_nth]
@@ -1023,9 +1023,9 @@ namespace Ex3
      - inputs: the sum allows to select the function to call in the recursive
        calls (and the functions may not have the same input types)
      - outputs: this case is degenerate because `even` and `odd` have the same
-       return type `Bool`, but generally speaking we need a sum type because
+       output type `Bool`, but generally speaking we need a sum type because
        the functions in the mutually recursive group may have different
-       return types.
+       output types.
    -/
   variable (k : (Int ⊕ Int) → Result (Bool ⊕ Bool))
 
@@ -1034,7 +1034,7 @@ namespace Ex3
     | .inl i =>
       -- Body of `is_even`
       if i = 0
-      then .ret (.inl true) -- We use .inl because this is `is_even`
+      then .ok (.inl true) -- We use .inl because this is `is_even`
       else
         do
           let b ←
@@ -1044,13 +1044,13 @@ namespace Ex3
               let r ← k (.inr (i- 1))
               match r with
               | .inl _ => .fail .panic -- Invalid output
-              | .inr b => .ret b
-          -- Wrap the return value
-          .ret (.inl b)
+              | .inr b => .ok b
+          -- Wrap the output value
+          .ok (.inl b)
     | .inr i =>
       -- Body of `is_odd`
       if i = 0
-      then .ret (.inr false) -- We use .inr because this is `is_odd`
+      then .ok (.inr false) -- We use .inr because this is `is_odd`
       else
         do
           let b ←
@@ -1059,10 +1059,10 @@ namespace Ex3
               -- extract the output value
               let r ← k (.inl (i- 1))
               match r with
-              | .inl b => .ret b
+              | .inl b => .ok b
               | .inr _ => .fail .panic -- Invalid output
-          -- Wrap the return value
-          .ret (.inr b)
+          -- Wrap the output value
+          .ok (.inr b)
 
   theorem is_even_is_odd_body_is_valid:
     ∀ k x, is_valid_p k (λ k => is_even_is_odd_body k x) := by
@@ -1078,7 +1078,7 @@ namespace Ex3
     do
       let r ← fix is_even_is_odd_body (.inl i)
       match r with
-      | .inl b => .ret b
+      | .inl b => .ok b
       | .inr _ => .fail .panic
 
   def is_odd (i : Int): Result Bool :=
@@ -1086,11 +1086,11 @@ namespace Ex3
       let r ← fix is_even_is_odd_body (.inr i)
       match r with
       | .inl _ => .fail .panic
-      | .inr b => .ret b
+      | .inr b => .ok b
 
   -- The unfolding equation for `is_even` - diverges if `i < 0`
   theorem is_even_eq (i : Int) :
-    is_even i = (if i = 0 then .ret true else is_odd (i - 1))
+    is_even i = (if i = 0 then .ok true else is_odd (i - 1))
     := by
     have Heq := is_valid_fix_fixed_eq is_even_is_odd_body_is_valid
     simp [is_even, is_odd]
@@ -1108,7 +1108,7 @@ namespace Ex3
 
   -- The unfolding equation for `is_odd` - diverges if `i < 0`
   theorem is_odd_eq (i : Int) :
-    is_odd i = (if i = 0 then .ret false else is_even (i - 1))
+    is_odd i = (if i = 0 then .ok false else is_even (i - 1))
     := by
     have Heq := is_valid_fix_fixed_eq is_even_is_odd_body_is_valid
     simp [is_even, is_odd]
@@ -1134,17 +1134,17 @@ namespace Ex4
   /- The bodies are more natural -/
   def is_even_body (k : (i : Fin 2) → (x : input_ty i) → Result (output_ty i x)) (i : Int) : Result Bool :=
     if i = 0
-      then .ret true
+      then .ok true
     else do
       let b ← k 1 (i - 1)
-      .ret b
+      .ok b
 
   def is_odd_body (k : (i : Fin 2) → (x : input_ty i) → Result (output_ty i x)) (i : Int) : Result Bool :=
     if i = 0
-      then .ret false
+      then .ok false
     else do
       let b ← k 0 (i - 1)
-      .ret b
+      .ok b
 
   @[simp] def bodies :
     Funs (Fin 2) input_ty output_ty
@@ -1177,19 +1177,19 @@ namespace Ex4
 
   theorem is_even_eq (i : Int) : is_even i =
     (if i = 0
-       then .ret true
+       then .ok true
      else do
        let b ← is_odd (i - 1)
-       .ret b) := by
+       .ok b) := by
     simp [is_even, is_odd];
     conv => lhs; rw [body_fix_eq]
 
   theorem is_odd_eq (i : Int) : is_odd i =
     (if i = 0
-       then .ret false
+       then .ok false
      else do
        let b ← is_even (i - 1)
-       .ret b) := by
+       .ok b) := by
     simp [is_even, is_odd];
     conv => lhs; rw [body_fix_eq]
 end Ex4
@@ -1203,12 +1203,12 @@ namespace Ex5
   /- An auxiliary function, which doesn't require the fixed-point -/
   def map (f : a → Result b) (ls : List a) : Result (List b) :=
     match ls with
-    | [] => .ret []
+    | [] => .ok []
     | hd :: tl =>
       do
         let hd ← f hd
         let tl ← map f tl
-        .ret (hd :: tl)
+        .ok (hd :: tl)
 
   /- The validity theorem for `map`, generic in `f` -/
   theorem map_is_valid
@@ -1229,11 +1229,11 @@ namespace Ex5
 
   def id_body (k : Tree a → Result (Tree a)) (t : Tree a) : Result (Tree a) :=
     match t with
-    | .leaf x => .ret (.leaf x)
+    | .leaf x => .ok (.leaf x)
     | .node tl =>
       do
         let tl ← map k tl
-        .ret (.node tl)
+        .ok (.node tl)
 
   theorem id_body_is_valid :
     ∀ k x, is_valid_p k (λ k => @id_body a k x) := by
@@ -1254,11 +1254,11 @@ namespace Ex5
   theorem id_eq (t : Tree a) :
     (id t =
        match t with
-       | .leaf x => .ret (.leaf x)
+       | .leaf x => .ok (.leaf x)
        | .node tl =>
        do
          let tl ← map id tl
-         .ret (.node tl))
+         .ok (.node tl))
     := by
     have Heq := is_valid_fix_fixed_eq (@id_body_is_valid a)
     simp [id]
@@ -1283,7 +1283,7 @@ namespace Ex6
     match ls with
     | [] => .fail .panic
     | hd :: tl =>
-      if i = 0 then .ret hd
+      if i = 0 then .ok hd
       else k 0 ⟨ a, tl, i - 1 ⟩
 
   @[simp] def bodies :
@@ -1314,7 +1314,7 @@ namespace Ex6
     match ls with
     | [] => is_valid_p_same k (.fail .panic)
     | hd :: tl =>
-      is_valid_p_ite k (Eq i 0) (is_valid_p_same k (.ret hd)) (is_valid_p_rec k 0 ⟨a, tl, i-1⟩)
+      is_valid_p_ite k (Eq i 0) (is_valid_p_same k (.ok hd)) (is_valid_p_rec k 0 ⟨a, tl, i-1⟩)
 
   theorem body_is_valid' : is_valid body :=
     fun k =>
@@ -1330,7 +1330,7 @@ namespace Ex6
       match ls with
       | [] => .fail .panic
       | hd :: tl =>
-        if i = 0 then .ret hd
+        if i = 0 then .ok hd
         else list_nth tl (i - 1)
     := by
     have Heq := is_valid_fix_fixed_eq body_is_valid
@@ -1345,7 +1345,7 @@ namespace Ex6
       match ls with
       | [] => .fail .panic
       | hd :: tl =>
-        if i = 0 then .ret hd
+        if i = 0 then .ok hd
         else list_nth tl (i - 1)
     :=
     -- Use the fixed-point equation
@@ -1376,7 +1376,7 @@ namespace Ex7
     match ls with
     | [] => .fail .panic
     | hd :: tl =>
-      if i = 0 then .ret hd
+      if i = 0 then .ok hd
       else k 0 a ⟨ tl, i - 1 ⟩
 
   @[simp] def bodies :
@@ -1407,7 +1407,7 @@ namespace Ex7
     match ls with
     | [] => is_valid_p_same k (.fail .panic)
     | hd :: tl =>
-      is_valid_p_ite k (Eq i 0) (is_valid_p_same k (.ret hd)) (is_valid_p_rec k 0 a ⟨tl, i-1⟩)
+      is_valid_p_ite k (Eq i 0) (is_valid_p_same k (.ok hd)) (is_valid_p_rec k 0 a ⟨tl, i-1⟩)
 
   theorem body_is_valid' : is_valid body :=
     fun k =>
@@ -1423,7 +1423,7 @@ namespace Ex7
       match ls with
       | [] => .fail .panic
       | hd :: tl =>
-        if i = 0 then .ret hd
+        if i = 0 then .ok hd
         else list_nth tl (i - 1)
     := by
     have Heq := is_valid_fix_fixed_eq body_is_valid
@@ -1438,7 +1438,7 @@ namespace Ex7
       match ls with
       | [] => .fail .panic
       | hd :: tl =>
-        if i = 0 then .ret hd
+        if i = 0 then .ok hd
         else list_nth tl (i - 1)
     :=
     -- Use the fixed-point equation
@@ -1464,12 +1464,12 @@ namespace Ex8
   /- An auxiliary function, which doesn't require the fixed-point -/
   def map {a : Type y} {b : Type z} (f : a → Result b) (ls : List a) : Result (List b) :=
     match ls with
-    | [] => .ret []
+    | [] => .ok []
     | hd :: tl =>
       do
         let hd ← f hd
         let tl ← map f tl
-        .ret (hd :: tl)
+        .ok (hd :: tl)
 
   /- The validity theorems for `map`, generic in `f` -/
 
@@ -1518,11 +1518,11 @@ namespace Ex9
   def id_body.{u} (k : (i:Fin 1) → (t:ty i) →  input_ty i t → Result (output_ty i t))
     (a : Type u) (t : Tree a) : Result (Tree a) :=
     match t with
-    | .leaf x => .ret (.leaf x)
+    | .leaf x => .ok (.leaf x)
     | .node tl =>
       do
         let tl ← map (k 0 a) tl
-        .ret (.node tl)
+        .ok (.node tl)
 
   @[simp] def bodies :
     Funs (Fin 1) ty input_ty output_ty tys :=
@@ -1556,11 +1556,11 @@ namespace Ex9
   theorem id_eq' {a : Type u} (t : Tree a) :
     id t =
       (match t with
-       | .leaf x => .ret (.leaf x)
+       | .leaf x => .ok (.leaf x)
        | .node tl =>
          do
            let tl ← map id tl
-           .ret (.node tl))
+           .ok (.node tl))
     :=
     -- The unfolding equation
     have Heq := is_valid_fix_fixed_eq body_is_valid.{u}
diff --git a/backends/lean/Base/Diverge/Elab.lean b/backends/lean/Base/Diverge/Elab.lean
index 71eaba10..5db8ffed 100644
--- a/backends/lean/Base/Diverge/Elab.lean
+++ b/backends/lean/Base/Diverge/Elab.lean
@@ -35,7 +35,7 @@ def mkProd (x y : Expr) : MetaM Expr :=
 def mkInOutTy (x y z : Expr) : MetaM Expr := do
   mkAppM ``FixII.mk_in_out_ty #[x, y, z]
 
--- Return the `a` in `Return a`
+-- Return the `a` in `Result a`
 def getResultTy (ty : Expr) : MetaM Expr :=
   ty.withApp fun f args => do
   if ¬ f.isConstOf ``Result ∨ args.size ≠ 1 then
@@ -411,7 +411,7 @@ structure TypeInfo where
      For `list_nth`: `λ a => List a × Int`
    -/
   in_ty : Expr
-  /- The output type, without the `Return`. This is a function taking
+  /- The output type, without the `Result`. This is a function taking
      as input a value of type `params_ty`.
 
      For `list_nth`: `λ a => a`
@@ -1479,9 +1479,9 @@ namespace Tests
   divergent def list_nth {a: Type u} (ls : List a) (i : Int) : Result a :=
     match ls with
     | [] => .fail .panic
-    | x :: ls =>
-      if i = 0 then return x
-      else return (← list_nth ls (i - 1))
+    | x :: ls => do
+      if i = 0 then pure x
+      else pure (← list_nth ls (i - 1))
 
   --set_option trace.Diverge false
 
@@ -1490,7 +1490,7 @@ namespace Tests
   example {a: Type} (ls : List a) :
     ∀ (i : Int),
     0 ≤ i → i < ls.length →
-    ∃ x, list_nth ls i = .ret x := by
+    ∃ x, list_nth ls i = .ok x := by
     induction ls
     . intro i hpos h; simp at h; linarith
     . rename_i hd tl ih
@@ -1538,7 +1538,7 @@ namespace Tests
       if i > 10 then return (← foo (i / 10)) + (← bar i) else bar 10
 
     divergent def bar (i : Int) : Result Nat :=
-      if i > 20 then foo (i / 20) else .ret 42
+      if i > 20 then foo (i / 20) else .ok 42
   end
 
   #check foo.unfold
@@ -1557,8 +1557,8 @@ namespace Tests
   divergent def iInBounds {a : Type} (ls : List a) (i : Int) : Result Bool :=
     let i0 := ls.length
     if i < i0
-    then Result.ret True
-    else Result.ret False
+    then Result.ok True
+    else Result.ok False
 
   #check iInBounds.unfold
 
@@ -1566,8 +1566,8 @@ namespace Tests
     {a : Type} (ls : List a) : Result Bool :=
     let ls1 := ls
     match ls1 with
-    | [] => Result.ret False
-    | _ :: _ => Result.ret True
+    | [] => Result.ok False
+    | _ :: _ => Result.ok True
 
   #check isCons.unfold
 
@@ -1584,7 +1584,7 @@ namespace Tests
   divergent def infinite_loop : Result Unit :=
     do
     let _ ← infinite_loop
-    Result.ret ()
+    Result.ok ()
 
   #check infinite_loop.unfold
 
@@ -1604,51 +1604,51 @@ namespace Tests
 
     divergent def id {a : Type u} (t : Tree a) : Result (Tree a) :=
       match t with
-      | .leaf x => .ret (.leaf x)
+      | .leaf x => .ok (.leaf x)
       | .node tl =>
         do
           let tl ← map id tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     #check id.unfold
 
     divergent def id1 {a : Type u} (t : Tree a) : Result (Tree a) :=
       match t with
-      | .leaf x => .ret (.leaf x)
+      | .leaf x => .ok (.leaf x)
       | .node tl =>
         do
           let tl ← map (fun x => id1 x) tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     #check id1.unfold
 
     divergent def id2 {a : Type u} (t : Tree a) : Result (Tree a) :=
       match t with
-      | .leaf x => .ret (.leaf x)
+      | .leaf x => .ok (.leaf x)
       | .node tl =>
         do
           let tl ← map (fun x => do let _ ← id2 x; id2 x) tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     #check id2.unfold
 
     divergent def incr (t : Tree Nat) : Result (Tree Nat) :=
       match t with
-      | .leaf x => .ret (.leaf (x + 1))
+      | .leaf x => .ok (.leaf (x + 1))
       | .node tl =>
         do
           let tl ← map incr tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     -- We handle this by inlining the let-binding
     divergent def id3 (t : Tree Nat) : Result (Tree Nat) :=
       match t with
-      | .leaf x => .ret (.leaf (x + 1))
+      | .leaf x => .ok (.leaf (x + 1))
       | .node tl =>
         do
           let f := id3
           let tl ← map f tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     #check id3.unfold
 
@@ -1658,12 +1658,12 @@ namespace Tests
     -- be parameterized by something).
     divergent def id4 (t : Tree Nat) : Result (Tree Nat) :=
       match t with
-      | .leaf x => .ret (.leaf (x + 1))
+      | .leaf x => .ok (.leaf (x + 1))
       | .node tl =>
         do
-          let f ← .ret id4
+          let f ← .ok id4
           let tl ← map f tl
-          .ret (.node tl)
+          .ok (.node tl)
 
     #check id4.unfold
     -/
diff --git a/backends/lean/Base/Primitives/Alloc.lean b/backends/lean/Base/Primitives/Alloc.lean
index 1f470fe1..15fe1ff9 100644
--- a/backends/lean/Base/Primitives/Alloc.lean
+++ b/backends/lean/Base/Primitives/Alloc.lean
@@ -11,8 +11,8 @@ namespace boxed -- alloc.boxed
 
 namespace Box -- alloc.boxed.Box
 
-def deref (T : Type) (x : T) : Result T := ret x
-def deref_mut (T : Type) (x : T) : Result (T × (T → Result T)) := ret (x, λ x => ret x)
+def deref (T : Type) (x : T) : Result T := ok x
+def deref_mut (T : Type) (x : T) : Result (T × (T → Result T)) := ok (x, λ x => ok x)
 
 /-- Trait instance -/
 def coreopsDerefInst (Self : Type) :
diff --git a/backends/lean/Base/Primitives/ArraySlice.lean b/backends/lean/Base/Primitives/ArraySlice.lean
index 3bd2aebb..91ca7284 100644
--- a/backends/lean/Base/Primitives/ArraySlice.lean
+++ b/backends/lean/Base/Primitives/ArraySlice.lean
@@ -49,7 +49,7 @@ abbrev Array.slice {α : Type u} {n : Usize} [Inhabited α] (v : Array α n) (i
 def Array.index_usize (α : Type u) (n : Usize) (v: Array α n) (i: Usize) : Result α :=
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
-  | some x => ret x
+  | some x => ok x
 
 -- For initialization
 def Array.repeat (α : Type u) (n : Usize) (x : α) : Array α n :=
@@ -68,7 +68,7 @@ theorem Array.repeat_spec {α : Type u} (n : Usize) (x : α) :
 @[pspec]
 theorem Array.index_usize_spec {α : Type u} {n : Usize} [Inhabited α] (v: Array α n) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x, v.index_usize α n i = ret x ∧ x = v.val.index i.val := by
+  ∃ x, v.index_usize α n i = ok x ∧ x = v.val.index i.val := by
   simp only [index_usize]
   -- TODO: dependent rewrite
   have h := List.indexOpt_eq_index v.val i.val (by scalar_tac) (by simp [*])
@@ -78,12 +78,12 @@ def Array.update_usize (α : Type u) (n : Usize) (v: Array α n) (i: Usize) (x:
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
   | some _ =>
-    .ret ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
+    ok ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
 
 @[pspec]
 theorem Array.update_usize_spec {α : Type u} {n : Usize} (v: Array α n) (i: Usize) (x : α)
   (hbound : i.val < v.length) :
-  ∃ nv, v.update_usize α n i x = ret nv ∧
+  ∃ nv, v.update_usize α n i x = ok nv ∧
   nv.val = v.val.update i.val x
   := by
   simp only [update_usize]
@@ -95,12 +95,12 @@ theorem Array.update_usize_spec {α : Type u} {n : Usize} (v: Array α n) (i: Us
 def Array.index_mut_usize (α : Type u) (n : Usize) (v: Array α n) (i: Usize) :
   Result (α × (α -> Result (Array α n))) := do
   let x ← index_usize α n v i
-  ret (x, update_usize α n v i)
+  ok (x, update_usize α n v i)
 
 @[pspec]
 theorem Array.index_mut_usize_spec {α : Type u} {n : Usize} [Inhabited α] (v: Array α n) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x back, v.index_mut_usize α n i = ret (x, back) ∧
+  ∃ x back, v.index_mut_usize α n i = ok (x, back) ∧
   x = v.val.index i.val ∧
   back = update_usize α n v i := by
   simp only [index_mut_usize, Bind.bind, bind]
@@ -147,7 +147,7 @@ abbrev Slice.slice {α : Type u} [Inhabited α] (s : Slice α) (i j : Int) : Lis
 def Slice.index_usize (α : Type u) (v: Slice α) (i: Usize) : Result α :=
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
-  | some x => ret x
+  | some x => ok x
 
 /- In the theorems below: we don't always need the `∃ ..`, but we use one
    so that `progress` introduces an opaque variable and an equality. This
@@ -157,7 +157,7 @@ def Slice.index_usize (α : Type u) (v: Slice α) (i: Usize) : Result α :=
 @[pspec]
 theorem Slice.index_usize_spec {α : Type u} [Inhabited α] (v: Slice α) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x, v.index_usize α i = ret x ∧ x = v.val.index i.val := by
+  ∃ x, v.index_usize α i = ok x ∧ x = v.val.index i.val := by
   simp only [index_usize]
   -- TODO: dependent rewrite
   have h := List.indexOpt_eq_index v.val i.val (by scalar_tac) (by simp [*])
@@ -167,12 +167,12 @@ def Slice.update_usize (α : Type u) (v: Slice α) (i: Usize) (x: α) : Result (
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
   | some _ =>
-    .ret ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
+    ok ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
 
 @[pspec]
 theorem Slice.update_usize_spec {α : Type u} (v: Slice α) (i: Usize) (x : α)
   (hbound : i.val < v.length) :
-  ∃ nv, v.update_usize α i x = ret nv ∧
+  ∃ nv, v.update_usize α i x = ok nv ∧
   nv.val = v.val.update i.val x
   := by
   simp only [update_usize]
@@ -184,12 +184,12 @@ theorem Slice.update_usize_spec {α : Type u} (v: Slice α) (i: Usize) (x : α)
 def Slice.index_mut_usize (α : Type u) (v: Slice α) (i: Usize) :
   Result (α × (α → Result (Slice α))) := do
   let x ← Slice.index_usize α v i
-  ret (x, Slice.update_usize α v i)
+  ok (x, Slice.update_usize α v i)
 
 @[pspec]
 theorem Slice.index_mut_usize_spec {α : Type u} [Inhabited α] (v: Slice α) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x back, v.index_mut_usize α i = ret (x, back) ∧
+  ∃ x back, v.index_mut_usize α i = ok (x, back) ∧
   x = v.val.index i.val ∧
   back = Slice.update_usize α v i := by
   simp only [index_mut_usize, Bind.bind, bind]
@@ -203,30 +203,30 @@ theorem Slice.index_mut_usize_spec {α : Type u} [Inhabited α] (v: Slice α) (i
    `progress` tactic), meaning `Array.to_slice` should be considered as opaque.
    All what the spec theorem reveals is that the "representative" lists are the same. -/
 def Array.to_slice (α : Type u) (n : Usize) (v : Array α n) : Result (Slice α) :=
-  ret ⟨ v.val, by simp [← List.len_eq_length]; scalar_tac ⟩
+  ok ⟨ v.val, by simp [← List.len_eq_length]; scalar_tac ⟩
 
 @[pspec]
 theorem Array.to_slice_spec {α : Type u} {n : Usize} (v : Array α n) :
-  ∃ s, to_slice α n v = ret s ∧ v.val = s.val := by simp [to_slice]
+  ∃ s, to_slice α n v = ok s ∧ v.val = s.val := by simp [to_slice]
 
 def Array.from_slice (α : Type u) (n : Usize) (_ : Array α n) (s : Slice α) : Result (Array α n) :=
   if h: s.val.len = n.val then
-    ret ⟨ s.val, by simp [← List.len_eq_length, *] ⟩
+    ok ⟨ s.val, by simp [← List.len_eq_length, *] ⟩
   else fail panic
 
 @[pspec]
 theorem Array.from_slice_spec {α : Type u} {n : Usize} (a : Array α n) (ns : Slice α) (h : ns.val.len = n.val) :
-  ∃ na, from_slice α n a ns = ret na ∧ na.val = ns.val
+  ∃ na, from_slice α n a ns = ok na ∧ na.val = ns.val
   := by simp [from_slice, *]
 
 def Array.to_slice_mut (α : Type u) (n : Usize) (a : Array α n) :
   Result (Slice α × (Slice α → Result (Array α n))) := do
   let s ← Array.to_slice α n a
-  ret (s, Array.from_slice α n a)
+  ok (s, Array.from_slice α n a)
 
 @[pspec]
 theorem Array.to_slice_mut_spec {α : Type u} {n : Usize} (v : Array α n) :
-  ∃ s back, to_slice_mut α n v = ret (s, back) ∧
+  ∃ s back, to_slice_mut α n v = ok (s, back) ∧
   v.val = s.val ∧
   back = Array.from_slice α n v
   := by simp [to_slice_mut, to_slice]
@@ -234,7 +234,7 @@ theorem Array.to_slice_mut_spec {α : Type u} {n : Usize} (v : Array α n) :
 def Array.subslice (α : Type u) (n : Usize) (a : Array α n) (r : Range Usize) : Result (Slice α) :=
   -- TODO: not completely sure here
   if r.start.val < r.end_.val ∧ r.end_.val ≤ a.val.len then
-    ret ⟨ a.val.slice r.start.val r.end_.val,
+    ok ⟨ a.val.slice r.start.val r.end_.val,
           by
             simp [← List.len_eq_length]
             have := a.val.slice_len_le r.start.val r.end_.val
@@ -245,7 +245,7 @@ def Array.subslice (α : Type u) (n : Usize) (a : Array α n) (r : Range Usize)
 @[pspec]
 theorem Array.subslice_spec {α : Type u} {n : Usize} [Inhabited α] (a : Array α n) (r : Range Usize)
   (h0 : r.start.val < r.end_.val) (h1 : r.end_.val ≤ a.val.len) :
-  ∃ s, subslice α n a r = ret s ∧
+  ∃ s, subslice α n a r = ok s ∧
   s.val = a.val.slice r.start.val r.end_.val ∧
   (∀ i, 0 ≤ i → i + r.start.val < r.end_.val → s.val.index i = a.val.index (r.start.val + i))
   := by
@@ -269,7 +269,7 @@ def Array.update_subslice (α : Type u) (n : Usize) (a : Array α n) (r : Range
       . scalar_tac
     let na := s_beg.append (s.val.append s_end)
     have : na.len = a.val.len := by simp [na, *]
-    ret ⟨ na, by simp_all [← List.len_eq_length]; scalar_tac ⟩
+    ok ⟨ na, by simp_all [← List.len_eq_length]; scalar_tac ⟩
   else
     fail panic
 
@@ -281,7 +281,7 @@ def Array.update_subslice (α : Type u) (n : Usize) (a : Array α n) (r : Range
 @[pspec]
 theorem Array.update_subslice_spec {α : Type u} {n : Usize} [Inhabited α] (a : Array α n) (r : Range Usize) (s : Slice α)
   (_ : r.start.val < r.end_.val) (_ : r.end_.val ≤ a.length) (_ : s.length = r.end_.val - r.start.val) :
-  ∃ na, update_subslice α n a r s = ret na ∧
+  ∃ na, update_subslice α n a r s = ok na ∧
   (∀ i, 0 ≤ i → i < r.start.val → na.index_s i = a.index_s i) ∧
   (∀ i, r.start.val ≤ i → i < r.end_.val → na.index_s i = s.index_s (i - r.start.val)) ∧
   (∀ i, r.end_.val ≤ i → i < n.val → na.index_s i = a.index_s i) := by
@@ -305,7 +305,7 @@ theorem Array.update_subslice_spec {α : Type u} {n : Usize} [Inhabited α] (a :
 def Slice.subslice (α : Type u) (s : Slice α) (r : Range Usize) : Result (Slice α) :=
   -- TODO: not completely sure here
   if r.start.val < r.end_.val ∧ r.end_.val ≤ s.length then
-    ret ⟨ s.val.slice r.start.val r.end_.val,
+    ok ⟨ s.val.slice r.start.val r.end_.val,
           by
             simp [← List.len_eq_length]
             have := s.val.slice_len_le r.start.val r.end_.val
@@ -316,7 +316,7 @@ def Slice.subslice (α : Type u) (s : Slice α) (r : Range Usize) : Result (Slic
 @[pspec]
 theorem Slice.subslice_spec {α : Type u} [Inhabited α] (s : Slice α) (r : Range Usize)
   (h0 : r.start.val < r.end_.val) (h1 : r.end_.val ≤ s.val.len) :
-  ∃ ns, subslice α s r = ret ns ∧
+  ∃ ns, subslice α s r = ok ns ∧
   ns.val = s.slice r.start.val r.end_.val ∧
   (∀ i, 0 ≤ i → i + r.start.val < r.end_.val → ns.index_s i = s.index_s (r.start.val + i))
   := by
@@ -343,14 +343,14 @@ def Slice.update_subslice (α : Type u) (s : Slice α) (r : Range Usize) (ss : S
       . scalar_tac
     let ns := s_beg.append (ss.val.append s_end)
     have : ns.len = s.val.len := by simp [ns, *]
-    ret ⟨ ns, by simp_all [← List.len_eq_length]; scalar_tac ⟩
+    ok ⟨ ns, by simp_all [← List.len_eq_length]; scalar_tac ⟩
   else
     fail panic
 
 @[pspec]
 theorem Slice.update_subslice_spec {α : Type u} [Inhabited α] (a : Slice α) (r : Range Usize) (ss : Slice α)
   (_ : r.start.val < r.end_.val) (_ : r.end_.val ≤ a.length) (_ : ss.length = r.end_.val - r.start.val) :
-  ∃ na, update_subslice α a r ss = ret na ∧
+  ∃ na, update_subslice α a r ss = ok na ∧
   (∀ i, 0 ≤ i → i < r.start.val → na.index_s i = a.index_s i) ∧
   (∀ i, r.start.val ≤ i → i < r.end_.val → na.index_s i = ss.index_s (i - r.start.val)) ∧
   (∀ i, r.end_.val ≤ i → i < a.length → na.index_s i = a.index_s i) := by
@@ -392,7 +392,7 @@ def core.slice.index.Slice.index
   let x ← inst.get i slice
   match x with
   | none => fail panic
-  | some x => ret x
+  | some x => ok x
 
 /- [core::slice::index::Range:::get]: forward function -/
 def core.slice.index.RangeUsize.get (T : Type) (i : Range Usize) (slice : Slice T) :
diff --git a/backends/lean/Base/Primitives/Base.lean b/backends/lean/Base/Primitives/Base.lean
index 0c64eca1..4c5b2795 100644
--- a/backends/lean/Base/Primitives/Base.lean
+++ b/backends/lean/Base/Primitives/Base.lean
@@ -41,7 +41,7 @@ deriving Repr, BEq
 open Error
 
 inductive Result (α : Type u) where
-  | ret (v: α): Result α
+  | ok (v: α): Result α
   | fail (e: Error): Result α
   | div
 deriving Repr, BEq
@@ -56,31 +56,31 @@ instance Result_Nonempty (α : Type u) : Nonempty (Result α) :=
 
 /- HELPERS -/
 
-def ret? {α: Type u} (r: Result α): Bool :=
+def ok? {α: Type u} (r: Result α): Bool :=
   match r with
-  | ret _ => true
+  | ok _ => true
   | fail _ | div => false
 
 def div? {α: Type u} (r: Result α): Bool :=
   match r with
   | div => true
-  | ret _ | fail _ => false
+  | ok _ | fail _ => false
 
 def massert (b:Bool) : Result Unit :=
-  if b then ret () else fail assertionFailure
+  if b then ok () else fail assertionFailure
 
 macro "prove_eval_global" : tactic => `(tactic| first | apply Eq.refl | decide)
 
-def eval_global {α: Type u} (x: Result α) (_: ret? x := by prove_eval_global) : α :=
+def eval_global {α: Type u} (x: Result α) (_: ok? x := by prove_eval_global) : α :=
   match x with
   | fail _ | div => by contradiction
-  | ret x => x
+  | ok x => x
 
 /- DO-DSL SUPPORT -/
 
 def bind {α : Type u} {β : Type v} (x: Result α) (f: α → Result β) : Result β :=
   match x with
-  | ret v  => f v
+  | ok v  => f v
   | fail v => fail v
   | div => div
 
@@ -88,11 +88,11 @@ def bind {α : Type u} {β : Type v} (x: Result α) (f: α → Result β) : Resu
 instance : Bind Result where
   bind := bind
 
--- Allows using return x in do-blocks
+-- Allows using pure x in do-blocks
 instance : Pure Result where
-  pure := fun x => ret x
+  pure := fun x => ok x
 
-@[simp] theorem bind_ret (x : α) (f : α → Result β) : bind (.ret x) f = f x := by simp [bind]
+@[simp] theorem bind_ok (x : α) (f : α → Result β) : bind (.ok x) f = f x := by simp [bind]
 @[simp] theorem bind_fail (x : Error) (f : α → Result β) : bind (.fail x) f = .fail x := by simp [bind]
 @[simp] theorem bind_div (f : α → Result β) : bind .div f = .div := by simp [bind]
 
@@ -103,14 +103,14 @@ instance : Pure Result where
 -- rely on subtype, and a custom let-binding operator, in effect recreating our
 -- own variant of the do-dsl
 
-def Result.attach {α: Type} (o : Result α): Result { x : α // o = ret x } :=
+def Result.attach {α: Type} (o : Result α): Result { x : α // o = ok x } :=
   match o with
-  | ret x => ret ⟨x, rfl⟩
+  | ok x => ok ⟨x, rfl⟩
   | fail e => fail e
   | div => div
 
-@[simp] theorem bind_tc_ret (x : α) (f : α → Result β) :
-  (do let y ← .ret x; f y) = f x := by simp [Bind.bind, bind]
+@[simp] theorem bind_tc_ok (x : α) (f : α → Result β) :
+  (do let y ← .ok x; f y) = f x := by simp [Bind.bind, bind]
 
 @[simp] theorem bind_tc_fail (x : Error) (f : α → Result β) :
   (do let y ← fail x; f y) = fail x := by simp [Bind.bind, bind]
diff --git a/backends/lean/Base/Primitives/Scalar.lean b/backends/lean/Base/Primitives/Scalar.lean
index 7668bc59..98d695a4 100644
--- a/backends/lean/Base/Primitives/Scalar.lean
+++ b/backends/lean/Base/Primitives/Scalar.lean
@@ -350,7 +350,7 @@ def Scalar.tryMk (ty : ScalarTy) (x : Int) : Result (Scalar ty) :=
     -- ```
     -- then normalization blocks (for instance, some proofs which use reflexivity fail).
     -- However, the version below doesn't block reduction (TODO: investigate):
-    return Scalar.ofIntCore x (Scalar.check_bounds_prop h)
+    ok (Scalar.ofIntCore x (Scalar.check_bounds_prop h))
   else fail integerOverflow
 
 def Scalar.neg {ty : ScalarTy} (x : Scalar ty) : Result (Scalar ty) := Scalar.tryMk ty (- x.val)
@@ -584,7 +584,7 @@ instance {ty} : HAnd (Scalar ty) (Scalar ty) (Scalar ty) where
 theorem Scalar.add_spec {ty} {x y : Scalar ty}
   (hmin : Scalar.min ty ≤ ↑x + y.val)
   (hmax : ↑x + ↑y ≤ Scalar.max ty) :
-  (∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y) := by
+  (∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y) := by
   -- Applying the unfoldings only on the left
   conv => congr; ext; lhs; unfold HAdd.hAdd instHAddScalarResult; simp [add, tryMk]
   split
@@ -593,7 +593,7 @@ theorem Scalar.add_spec {ty} {x y : Scalar ty}
 
 theorem Scalar.add_unsigned_spec {ty} (s: ¬ ty.isSigned) {x y : Scalar ty}
   (hmax : ↑x + ↑y ≤ Scalar.max ty) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   have hmin : Scalar.min ty ≤ ↑x + ↑y := by
     have hx := x.hmin
     have hy := y.hmin
@@ -602,57 +602,57 @@ theorem Scalar.add_unsigned_spec {ty} (s: ¬ ty.isSigned) {x y : Scalar ty}
 
 /- Fine-grained theorems -/
 @[pspec] theorem Usize.add_spec {x y : Usize} (hmax : ↑x + ↑y ≤ Usize.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem U8.add_spec {x y : U8} (hmax : ↑x + ↑y ≤ U8.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem U16.add_spec {x y : U16} (hmax : ↑x + ↑y ≤ U16.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem U32.add_spec {x y : U32} (hmax : ↑x + ↑y ≤ U32.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem U64.add_spec {x y : U64} (hmax : ↑x + ↑y ≤ U64.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem U128.add_spec {x y : U128} (hmax : ↑x + ↑y ≤ U128.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y := by
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y := by
   apply Scalar.add_unsigned_spec <;> simp [ScalarTy.isSigned, Scalar.max, *]
 
 @[pspec] theorem Isize.add_spec {x y : Isize}
   (hmin : Isize.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ Isize.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 @[pspec] theorem I8.add_spec {x y : I8}
   (hmin : I8.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ I8.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 @[pspec] theorem I16.add_spec {x y : I16}
   (hmin : I16.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ I16.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 @[pspec] theorem I32.add_spec {x y : I32}
   (hmin : I32.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ I32.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 @[pspec] theorem I64.add_spec {x y : I64}
   (hmin : I64.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ I64.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 @[pspec] theorem I128.add_spec {x y : I128}
   (hmin : I128.min ≤ ↑x + ↑y) (hmax : ↑x + ↑y ≤ I128.max) :
-  ∃ z, x + y = ret z ∧ (↑z : Int) = ↑x + ↑y :=
+  ∃ z, x + y = ok z ∧ (↑z : Int) = ↑x + ↑y :=
   Scalar.add_spec hmin hmax
 
 -- Generic theorem - shouldn't be used much
@@ -660,7 +660,7 @@ theorem Scalar.add_unsigned_spec {ty} (s: ¬ ty.isSigned) {x y : Scalar ty}
 theorem Scalar.sub_spec {ty} {x y : Scalar ty}
   (hmin : Scalar.min ty ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ Scalar.max ty) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   conv => congr; ext; lhs; simp [HSub.hSub, sub, tryMk, Sub.sub]
   split
   . simp [pure]
@@ -669,7 +669,7 @@ theorem Scalar.sub_spec {ty} {x y : Scalar ty}
 
 theorem Scalar.sub_unsigned_spec {ty : ScalarTy} (s : ¬ ty.isSigned)
   {x y : Scalar ty} (hmin : Scalar.min ty ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   have : ↑x - ↑y ≤ Scalar.max ty := by
     have hx := x.hmin
     have hxm := x.hmax
@@ -680,64 +680,64 @@ theorem Scalar.sub_unsigned_spec {ty : ScalarTy} (s : ¬ ty.isSigned)
 
 /- Fine-grained theorems -/
 @[pspec] theorem Usize.sub_spec {x y : Usize} (hmin : Usize.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem U8.sub_spec {x y : U8} (hmin : U8.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem U16.sub_spec {x y : U16} (hmin : U16.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem U32.sub_spec {x y : U32} (hmin : U32.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem U64.sub_spec {x y : U64} (hmin : U64.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem U128.sub_spec {x y : U128} (hmin : U128.min ≤ ↑x - ↑y) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y := by
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y := by
   apply Scalar.sub_unsigned_spec <;> simp_all [Scalar.min, ScalarTy.isSigned]
 
 @[pspec] theorem Isize.sub_spec {x y : Isize} (hmin : Isize.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ Isize.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 @[pspec] theorem I8.sub_spec {x y : I8} (hmin : I8.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ I8.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 @[pspec] theorem I16.sub_spec {x y : I16} (hmin : I16.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ I16.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 @[pspec] theorem I32.sub_spec {x y : I32} (hmin : I32.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ I32.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 @[pspec] theorem I64.sub_spec {x y : I64} (hmin : I64.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ I64.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 @[pspec] theorem I128.sub_spec {x y : I128} (hmin : I128.min ≤ ↑x - ↑y)
   (hmax : ↑x - ↑y ≤ I128.max) :
-  ∃ z, x - y = ret z ∧ (↑z : Int) = ↑x - ↑y :=
+  ∃ z, x - y = ok z ∧ (↑z : Int) = ↑x - ↑y :=
   Scalar.sub_spec hmin hmax
 
 -- Generic theorem - shouldn't be used much
 theorem Scalar.mul_spec {ty} {x y : Scalar ty}
   (hmin : Scalar.min ty ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ Scalar.max ty) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   conv => congr; ext; lhs; simp [HMul.hMul]
   simp [mul, tryMk]
   split
@@ -747,7 +747,7 @@ theorem Scalar.mul_spec {ty} {x y : Scalar ty}
 
 theorem Scalar.mul_unsigned_spec {ty} (s: ¬ ty.isSigned) {x y : Scalar ty}
   (hmax : ↑x * ↑y ≤ Scalar.max ty) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   have : Scalar.min ty ≤ ↑x * ↑y := by
     have hx := x.hmin
     have hy := y.hmin
@@ -756,57 +756,57 @@ theorem Scalar.mul_unsigned_spec {ty} (s: ¬ ty.isSigned) {x y : Scalar ty}
 
 /- Fine-grained theorems -/
 @[pspec] theorem Usize.mul_spec {x y : Usize} (hmax : ↑x * ↑y ≤ Usize.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem U8.mul_spec {x y : U8} (hmax : ↑x * ↑y ≤ U8.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem U16.mul_spec {x y : U16} (hmax : ↑x * ↑y ≤ U16.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem U32.mul_spec {x y : U32} (hmax : ↑x * ↑y ≤ U32.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem U64.mul_spec {x y : U64} (hmax : ↑x * ↑y ≤ U64.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem U128.mul_spec {x y : U128} (hmax : ↑x * ↑y ≤ U128.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y := by
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y := by
   apply Scalar.mul_unsigned_spec <;> simp_all [Scalar.max, ScalarTy.isSigned]
 
 @[pspec] theorem Isize.mul_spec {x y : Isize} (hmin : Isize.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ Isize.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 @[pspec] theorem I8.mul_spec {x y : I8} (hmin : I8.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ I8.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 @[pspec] theorem I16.mul_spec {x y : I16} (hmin : I16.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ I16.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 @[pspec] theorem I32.mul_spec {x y : I32} (hmin : I32.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ I32.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 @[pspec] theorem I64.mul_spec {x y : I64} (hmin : I64.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ I64.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 @[pspec] theorem I128.mul_spec {x y : I128} (hmin : I128.min ≤ ↑x * ↑y)
   (hmax : ↑x * ↑y ≤ I128.max) :
-  ∃ z, x * y = ret z ∧ (↑z : Int) = ↑x * ↑y :=
+  ∃ z, x * y = ok z ∧ (↑z : Int) = ↑x * ↑y :=
   Scalar.mul_spec hmin hmax
 
 -- Generic theorem - shouldn't be used much
@@ -815,15 +815,14 @@ theorem Scalar.div_spec {ty} {x y : Scalar ty}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : Scalar.min ty ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ Scalar.max ty) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y := by
   simp [HDiv.hDiv, div, Div.div]
   simp [tryMk, *]
-  simp [pure]
   rfl
 
 theorem Scalar.div_unsigned_spec {ty} (s: ¬ ty.isSigned) (x : Scalar ty) {y : Scalar ty}
   (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   have h : Scalar.min ty = 0 := by cases ty <;> simp [ScalarTy.isSigned, min] at *
   have hx := x.hmin
   have hy := y.hmin
@@ -839,69 +838,69 @@ theorem Scalar.div_unsigned_spec {ty} (s: ¬ ty.isSigned) (x : Scalar ty) {y : S
 
 /- Fine-grained theorems -/
 @[pspec] theorem Usize.div_spec (x : Usize) {y : Usize} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U8.div_spec (x : U8) {y : U8} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U16.div_spec (x : U16) {y : U16} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U32.div_spec (x : U32) {y : U32} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U64.div_spec (x : U64) {y : U64} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U128.div_spec (x : U128) {y : U128} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x / y = ret z ∧ (↑z : Int) = ↑x / ↑y := by
+  ∃ z, x / y = ok z ∧ (↑z : Int) = ↑x / ↑y := by
   apply Scalar.div_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem Isize.div_spec (x : Isize) {y : Isize}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : Isize.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ Isize.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 @[pspec] theorem I8.div_spec (x : I8) {y : I8}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I8.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ I8.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 @[pspec] theorem I16.div_spec (x : I16) {y : I16}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I16.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ I16.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 @[pspec] theorem I32.div_spec (x : I32) {y : I32}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I32.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ I32.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 @[pspec] theorem I64.div_spec (x : I64) {y : I64}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I64.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ I64.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 @[pspec] theorem I128.div_spec (x : I128) {y : I128}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I128.min ≤ scalar_div ↑x ↑y)
   (hmax : scalar_div ↑x ↑y ≤ I128.max):
-  ∃ z, x / y = ret z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
+  ∃ z, x / y = ok z ∧ (↑z : Int) = scalar_div ↑x ↑y :=
   Scalar.div_spec hnz hmin hmax
 
 -- Generic theorem - shouldn't be used much
@@ -910,15 +909,14 @@ theorem Scalar.rem_spec {ty} {x y : Scalar ty}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : Scalar.min ty ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ Scalar.max ty) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y := by
   simp [HMod.hMod, rem]
   simp [tryMk, *]
-  simp [pure]
   rfl
 
 theorem Scalar.rem_unsigned_spec {ty} (s: ¬ ty.isSigned) (x : Scalar ty) {y : Scalar ty}
   (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   have h : Scalar.min ty = 0 := by cases ty <;> simp [ScalarTy.isSigned, min] at *
   have hx := x.hmin
   have hy := y.hmin
@@ -934,62 +932,62 @@ theorem Scalar.rem_unsigned_spec {ty} (s: ¬ ty.isSigned) (x : Scalar ty) {y : S
   simp [*]
 
 @[pspec] theorem Usize.rem_spec (x : Usize) {y : Usize} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U8.rem_spec (x : U8) {y : U8} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U16.rem_spec (x : U16) {y : U16} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U32.rem_spec (x : U32) {y : U32} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U64.rem_spec (x : U64) {y : U64} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem U128.rem_spec (x : U128) {y : U128} (hnz : ↑y ≠ (0 : Int)) :
-  ∃ z, x % y = ret z ∧ (↑z : Int) = ↑x % ↑y := by
+  ∃ z, x % y = ok z ∧ (↑z : Int) = ↑x % ↑y := by
   apply Scalar.rem_unsigned_spec <;> simp [ScalarTy.isSigned, *]
 
 @[pspec] theorem I8.rem_spec (x : I8) {y : I8}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I8.min ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ I8.max):
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
   Scalar.rem_spec hnz hmin hmax
 
 @[pspec] theorem I16.rem_spec (x : I16) {y : I16}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I16.min ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ I16.max):
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
   Scalar.rem_spec hnz hmin hmax
 
 @[pspec] theorem I32.rem_spec (x : I32) {y : I32}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I32.min ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ I32.max):
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
   Scalar.rem_spec hnz hmin hmax
 
 @[pspec] theorem I64.rem_spec (x : I64) {y : I64}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I64.min ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ I64.max):
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
   Scalar.rem_spec hnz hmin hmax
 
 @[pspec] theorem I128.rem_spec (x : I128) {y : I128}
   (hnz : ↑y ≠ (0 : Int))
   (hmin : I128.min ≤ scalar_rem ↑x ↑y)
   (hmax : scalar_rem ↑x ↑y ≤ I128.max):
-  ∃ z, x % y = ret z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
+  ∃ z, x % y = ok z ∧ (↑z : Int) = scalar_rem ↑x ↑y :=
   Scalar.rem_spec hnz hmin hmax
 
 -- ofIntCore
diff --git a/backends/lean/Base/Primitives/Vec.lean b/backends/lean/Base/Primitives/Vec.lean
index 2b8425d8..8e2d65a8 100644
--- a/backends/lean/Base/Primitives/Vec.lean
+++ b/backends/lean/Base/Primitives/Vec.lean
@@ -60,34 +60,34 @@ def Vec.push (α : Type u) (v : Vec α) (x : α) : Result (Vec α)
       simp [Usize.max] at *
       have hm := Usize.refined_max.property
       cases h <;> cases hm <;> simp [U32.max, U64.max] at * <;> try linarith
-    return ⟨ List.concat v.val x, by simp at *; assumption ⟩
+    ok ⟨ List.concat v.val x, by simp at *; assumption ⟩
   else
     fail maximumSizeExceeded
 
 -- This shouldn't be used
 def Vec.insert_fwd (α : Type u) (v: Vec α) (i: Usize) (_: α) : Result Unit :=
   if i.val < v.length then
-    .ret ()
+    ok ()
   else
-    .fail arrayOutOfBounds
+    fail arrayOutOfBounds
 
 -- This is actually the backward function
 def Vec.insert (α : Type u) (v: Vec α) (i: Usize) (x: α) : Result (Vec α) :=
   if i.val < v.length then
-    .ret ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
+    ok ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
   else
-    .fail arrayOutOfBounds
+    fail arrayOutOfBounds
 
 @[pspec]
 theorem Vec.insert_spec {α : Type u} (v: Vec α) (i: Usize) (x: α)
   (hbound : i.val < v.length) :
-  ∃ nv, v.insert α i x = ret nv ∧ nv.val = v.val.update i.val x := by
+  ∃ nv, v.insert α i x = ok nv ∧ nv.val = v.val.update i.val x := by
   simp [insert, *]
 
 def Vec.index_usize {α : Type u} (v: Vec α) (i: Usize) : Result α :=
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
-  | some x => ret x
+  | some x => ok x
 
 /- In the theorems below: we don't always need the `∃ ..`, but we use one
    so that `progress` introduces an opaque variable and an equality. This
@@ -97,7 +97,7 @@ def Vec.index_usize {α : Type u} (v: Vec α) (i: Usize) : Result α :=
 @[pspec]
 theorem Vec.index_usize_spec {α : Type u} [Inhabited α] (v: Vec α) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x, v.index_usize i = ret x ∧ x = v.val.index i.val := by
+  ∃ x, v.index_usize i = ok x ∧ x = v.val.index i.val := by
   simp only [index_usize]
   -- TODO: dependent rewrite
   have h := List.indexOpt_eq_index v.val i.val (by scalar_tac) (by simp [*])
@@ -107,12 +107,12 @@ def Vec.update_usize {α : Type u} (v: Vec α) (i: Usize) (x: α) : Result (Vec
   match v.val.indexOpt i.val with
   | none => fail .arrayOutOfBounds
   | some _ =>
-    .ret ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
+    ok ⟨ v.val.update i.val x, by have := v.property; simp [*] ⟩
 
 @[pspec]
 theorem Vec.update_usize_spec {α : Type u} (v: Vec α) (i: Usize) (x : α)
   (hbound : i.val < v.length) :
-  ∃ nv, v.update_usize i x = ret nv ∧
+  ∃ nv, v.update_usize i x = ok nv ∧
   nv.val = v.val.update i.val x
   := by
   simp only [update_usize]
@@ -124,15 +124,15 @@ theorem Vec.update_usize_spec {α : Type u} (v: Vec α) (i: Usize) (x : α)
 def Vec.index_mut_usize {α : Type u} (v: Vec α) (i: Usize) :
   Result (α × (α → Result (Vec α))) :=
   match Vec.index_usize v i with
-  | ret x =>
-    ret (x, Vec.update_usize v i)
+  | ok x =>
+    ok (x, Vec.update_usize v i)
   | fail e => fail e
   | div => div
 
 @[pspec]
 theorem Vec.index_mut_usize_spec {α : Type u} [Inhabited α] (v: Vec α) (i: Usize)
   (hbound : i.val < v.length) :
-  ∃ x back, v.index_mut_usize i = ret (x, back) ∧
+  ∃ x back, v.index_mut_usize i = ok (x, back) ∧
   x = v.val.index i.val ∧
   -- Backward function
   back = v.update_usize i
diff --git a/backends/lean/Base/Progress/Progress.lean b/backends/lean/Base/Progress/Progress.lean
index dc30c441..ea38c630 100644
--- a/backends/lean/Base/Progress/Progress.lean
+++ b/backends/lean/Base/Progress/Progress.lean
@@ -136,7 +136,7 @@ def progressWith (fExpr : Expr) (th : TheoremOrLocal)
     let _ ←
       tryTac
         (simpAt true []
-               [``Primitives.bind_tc_ret, ``Primitives.bind_tc_fail, ``Primitives.bind_tc_div]
+               [``Primitives.bind_tc_ok, ``Primitives.bind_tc_fail, ``Primitives.bind_tc_div]
                [hEq.fvarId!] (.targets #[] true))
     -- It may happen that at this point the goal is already solved (though this is rare)
     -- TODO: not sure this is the best way of checking it
@@ -397,33 +397,33 @@ namespace Test
   example {ty} {x y : Scalar ty}
     (hmin : Scalar.min ty ≤ x.val + y.val)
     (hmax : x.val + y.val ≤ Scalar.max ty) :
-    ∃ z, x + y = ret z ∧ z.val = x.val + y.val := by
+    ∃ z, x + y = ok z ∧ z.val = x.val + y.val := by
     progress keep _ as ⟨ z, h1 .. ⟩
     simp [*, h1]
 
   example {ty} {x y : Scalar ty}
     (hmin : Scalar.min ty ≤ x.val + y.val)
     (hmax : x.val + y.val ≤ Scalar.max ty) :
-    ∃ z, x + y = ret z ∧ z.val = x.val + y.val := by
+    ∃ z, x + y = ok z ∧ z.val = x.val + y.val := by
     progress keep h with Scalar.add_spec as ⟨ z ⟩
     simp [*, h]
 
   example {x y : U32}
     (hmax : x.val + y.val ≤ U32.max) :
-    ∃ z, x + y = ret z ∧ z.val = x.val + y.val := by
+    ∃ z, x + y = ok z ∧ z.val = x.val + y.val := by
     -- This spec theorem is suboptimal, but it is good to check that it works
     progress with Scalar.add_spec as ⟨ z, h1 .. ⟩
     simp [*, h1]
  
   example {x y : U32}
     (hmax : x.val + y.val ≤ U32.max) :
-    ∃ z, x + y = ret z ∧ z.val = x.val + y.val := by
+    ∃ z, x + y = ok z ∧ z.val = x.val + y.val := by
     progress with U32.add_spec as ⟨ z, h1 .. ⟩
     simp [*, h1]
 
   example {x y : U32}
     (hmax : x.val + y.val ≤ U32.max) :
-    ∃ z, x + y = ret z ∧ z.val = x.val + y.val := by
+    ∃ z, x + y = ok z ∧ z.val = x.val + y.val := by
     progress keep _ as ⟨ z, h1 .. ⟩
     simp [*, h1]
 
@@ -431,7 +431,7 @@ namespace Test
      `α : Type u` where u is quantified, while here we use `α : Type 0` -/
   example {α : Type} (v: Vec α) (i: Usize) (x : α)
     (hbounds : i.val < v.length) :
-    ∃ nv, v.update_usize i x = ret nv ∧
+    ∃ nv, v.update_usize i x = ok nv ∧
     nv.val = v.val.update i.val x := by
     progress
     simp [*]
@@ -443,8 +443,8 @@ namespace Test
       (do
          (do
             let _ ← v.update_usize i x
-            .ret ())
-         .ret ()) = ret nv
+            .ok ())
+         .ok ()) = ok nv
       := by
     progress
     simp [*]
@@ -454,8 +454,8 @@ namespace Test
      not a constant. We also test the case where the function under scrutinee
      is not a constant. -/
   example {x : U32}
-    (f : U32 → Result Unit) (h : ∀ x, f x = .ret ()) :
-    f x = ret () := by
+    (f : U32 → Result Unit) (h : ∀ x, f x = .ok ()) :
+    f x = ok () := by
     progress
 
 end Test
diff --git a/compiler/Extract.ml b/compiler/Extract.ml
index 985fb470..6eeef772 100644
--- a/compiler/Extract.ml
+++ b/compiler/Extract.ml
@@ -2867,7 +2867,7 @@ let extract_unit_test_if_unit_fun (ctx : extraction_ctx) (fmt : F.formatter)
         F.pp_print_string fmt "=";
         F.pp_print_space fmt ();
         let success =
-          ctx_get_variant def.meta (TAssumed TResult) result_return_id ctx
+          ctx_get_variant def.meta (TAssumed TResult) result_ok_id ctx
         in
         F.pp_print_string fmt (success ^ " ())")
     | Coq ->
@@ -2898,11 +2898,11 @@ let extract_unit_test_if_unit_fun (ctx : extraction_ctx) (fmt : F.formatter)
         F.pp_print_string fmt "==";
         F.pp_print_space fmt ();
         let success =
-          ctx_get_variant def.meta (TAssumed TResult) result_return_id ctx
+          ctx_get_variant def.meta (TAssumed TResult) result_ok_id ctx
         in
         F.pp_print_string fmt (success ^ " ())")
     | HOL4 ->
-        F.pp_print_string fmt "val _ = assert_return (";
+        F.pp_print_string fmt "val _ = assert_ok (";
         F.pp_print_string fmt "“";
         let fun_name =
           ctx_get_local_function def.meta def.def_id def.loop_id ctx
diff --git a/compiler/ExtractBase.ml b/compiler/ExtractBase.ml
index 47b613c2..656d2f27 100644
--- a/compiler/ExtractBase.ml
+++ b/compiler/ExtractBase.ml
@@ -1020,7 +1020,7 @@ let assumed_variants () : (assumed_ty * VariantId.id * string) list =
   match !backend with
   | FStar ->
       [
-        (TResult, result_return_id, "Return");
+        (TResult, result_ok_id, "Ok");
         (TResult, result_fail_id, "Fail");
         (TError, error_failure_id, "Failure");
         (TError, error_out_of_fuel_id, "OutOfFuel");
@@ -1029,7 +1029,7 @@ let assumed_variants () : (assumed_ty * VariantId.id * string) list =
       ]
   | Coq ->
       [
-        (TResult, result_return_id, "Return");
+        (TResult, result_ok_id, "Ok");
         (TResult, result_fail_id, "Fail_");
         (TError, error_failure_id, "Failure");
         (TError, error_out_of_fuel_id, "OutOfFuel");
@@ -1038,7 +1038,7 @@ let assumed_variants () : (assumed_ty * VariantId.id * string) list =
       ]
   | Lean ->
       [
-        (TResult, result_return_id, "Result.ret");
+        (TResult, result_ok_id, "Result.ok");
         (TResult, result_fail_id, "Result.fail");
         (* For panic: we omit the prefix "Error." because the type is always
            clear from the context. Also, "Error" is often used by user-defined
@@ -1049,7 +1049,7 @@ let assumed_variants () : (assumed_ty * VariantId.id * string) list =
       ]
   | HOL4 ->
       [
-        (TResult, result_return_id, "Return");
+        (TResult, result_ok_id, "Ok");
         (TResult, result_fail_id, "Fail");
         (TError, error_failure_id, "Failure");
         (* No Fuel::Zero on purpose *)
diff --git a/compiler/PrintPure.ml b/compiler/PrintPure.ml
index 97ea6048..db9c583d 100644
--- a/compiler/PrintPure.ml
+++ b/compiler/PrintPure.ml
@@ -312,7 +312,7 @@ let adt_variant_to_string ?(meta = None) (env : fmt_env) (adt_id : type_id)
           craise_opt_meta __FILE__ __LINE__ meta "Unreachable"
       | TResult ->
           let variant_id = Option.get variant_id in
-          if variant_id = result_return_id then "@Result::Return"
+          if variant_id = result_ok_id then "@Result::Return"
           else if variant_id = result_fail_id then "@Result::Fail"
           else
             craise_opt_meta __FILE__ __LINE__ meta
@@ -395,7 +395,7 @@ let adt_g_value_to_string ?(meta : Meta.meta option = None) (env : fmt_env)
           craise_opt_meta __FILE__ __LINE__ meta "Unreachable"
       | TResult ->
           let variant_id = Option.get variant_id in
-          if variant_id = result_return_id then
+          if variant_id = result_ok_id then
             match field_values with
             | [ v ] -> "@Result::Return " ^ v
             | _ ->
diff --git a/compiler/Pure.ml b/compiler/Pure.ml
index 7366783c..451767f8 100644
--- a/compiler/Pure.ml
+++ b/compiler/Pure.ml
@@ -92,7 +92,7 @@ type assumed_ty =
 (* TODO: we should never directly manipulate [Return] and [Fail], but rather
  * the monadic functions [return] and [fail] (makes treatment of error and
  * state-error monads more uniform) *)
-let result_return_id = VariantId.of_int 0
+let result_ok_id = VariantId.of_int 0
 let result_fail_id = VariantId.of_int 1
 let option_some_id = T.option_some_id
 let option_none_id = T.option_none_id
diff --git a/compiler/PureMicroPasses.ml b/compiler/PureMicroPasses.ml
index ebc5c65f..004ecfef 100644
--- a/compiler/PureMicroPasses.ml
+++ b/compiler/PureMicroPasses.ml
@@ -752,7 +752,7 @@ let simplify_let_bindings (_ctx : trans_ctx) (def : fun_decl) : fun_decl =
               },
               x ) ->
             (* return/fail case *)
-            if variant_id = result_return_id then
+            if variant_id = result_ok_id then
               (* Return case - note that the simplification we just perform
                  might have unlocked the tuple simplification below *)
               self#visit_Let env false lv x next
@@ -1084,19 +1084,19 @@ let filter_useless (_ctx : trans_ctx) (def : fun_decl) : fun_decl =
       let body = { body with body = body_exp; inputs_lvs } in
       { def with body = Some body }
 
-(** Simplify the lets immediately followed by a return.
+(** Simplify the lets immediately followed by an ok.
 
     Ex.:
     {[
       x <-- f y;
-      Return x
+      Ok x
 
         ~~>
 
       f y
     ]}
  *)
-let simplify_let_then_return _ctx (def : fun_decl) =
+let simplify_let_then_ok _ctx (def : fun_decl) =
   (* Match a pattern and an expression: evaluates to [true] if the expression
      is actually exactly the pattern *)
   let rec match_pattern_and_expr (pat : typed_pattern) (e : texpression) : bool
@@ -1152,7 +1152,7 @@ let simplify_let_then_return _ctx (def : fun_decl) =
               | Some e ->
                   if match_pattern_and_expr lv e then
                     (* We need to wrap the right-value in a ret *)
-                    (mk_result_return_texpression def.meta rv).e
+                    (mk_result_ok_texpression def.meta rv).e
                   else not_simpl_e
               | None ->
                   if match_pattern_and_expr lv next_e then rv.e else not_simpl_e
@@ -1791,7 +1791,7 @@ let unfold_monadic_let_bindings (_ctx : trans_ctx) (def : fun_decl) : fun_decl =
               let err_v = mk_texpression_from_var err_var in
               let fail_value = mk_result_fail_texpression def.meta err_v e.ty in
               let fail_branch = { pat = fail_pat; branch = fail_value } in
-              let success_pat = mk_result_return_pattern lv in
+              let success_pat = mk_result_ok_pattern lv in
               let success_branch = { pat = success_pat; branch = e } in
               let switch_body = Match [ fail_branch; success_branch ] in
               let e = Switch (re, switch_body) in
@@ -1854,9 +1854,9 @@ let apply_end_passes_to_def (ctx : trans_ctx) (def : fun_decl) : fun_decl =
        f y
      ]}
   *)
-  let def = simplify_let_then_return ctx def in
+  let def = simplify_let_then_ok ctx def in
   log#ldebug
-    (lazy ("simplify_let_then_return:\n\n" ^ fun_decl_to_string ctx def ^ "\n"));
+    (lazy ("simplify_let_then_ok:\n\n" ^ fun_decl_to_string ctx def ^ "\n"));
 
   (* Simplify the aggregated ADTs.
 
@@ -1892,11 +1892,10 @@ let apply_end_passes_to_def (ctx : trans_ctx) (def : fun_decl) : fun_decl =
 
   (* Simplify the let-then return again (the lambda simplification may have
      unlocked more simplifications here) *)
-  let def = simplify_let_then_return ctx def in
+  let def = simplify_let_then_ok ctx def in
   log#ldebug
     (lazy
-      ("simplify_let_then_return (pass 2):\n\n" ^ fun_decl_to_string ctx def
-     ^ "\n"));
+      ("simplify_let_then_ok (pass 2):\n\n" ^ fun_decl_to_string ctx def ^ "\n"));
 
   (* Decompose the monadic let-bindings - used by Coq *)
   let def =
diff --git a/compiler/PureTypeCheck.ml b/compiler/PureTypeCheck.ml
index 27044c27..c1da4019 100644
--- a/compiler/PureTypeCheck.ml
+++ b/compiler/PureTypeCheck.ml
@@ -32,7 +32,7 @@ let get_adt_field_types (meta : Meta.meta)
       | TResult ->
           let ty = Collections.List.to_cons_nil generics.types in
           let variant_id = Option.get variant_id in
-          if variant_id = result_return_id then [ ty ]
+          if variant_id = result_ok_id then [ ty ]
           else if variant_id = result_fail_id then [ mk_error_ty ]
           else
             craise __FILE__ __LINE__ meta
diff --git a/compiler/PureUtils.ml b/compiler/PureUtils.ml
index 1bef43b4..fdd14eba 100644
--- a/compiler/PureUtils.ml
+++ b/compiler/PureUtils.ml
@@ -586,12 +586,12 @@ let mk_result_fail_texpression_with_error_id (meta : Meta.meta)
   let error = mk_error error in
   mk_result_fail_texpression meta error ty
 
-let mk_result_return_texpression (meta : Meta.meta) (v : texpression) :
-    texpression =
+let mk_result_ok_texpression (meta : Meta.meta) (v : texpression) : texpression
+    =
   let type_args = [ v.ty ] in
   let ty = TAdt (TAssumed TResult, mk_generic_args_from_types type_args) in
   let id =
-    AdtCons { adt_id = TAssumed TResult; variant_id = Some result_return_id }
+    AdtCons { adt_id = TAssumed TResult; variant_id = Some result_ok_id }
   in
   let qualif = { id; generics = mk_generic_args_from_types type_args } in
   let cons_e = Qualif qualif in
@@ -613,11 +613,9 @@ let mk_result_fail_pattern_ignore_error (ty : ty) : typed_pattern =
   let error_pat : pattern = PatDummy in
   mk_result_fail_pattern error_pat ty
 
-let mk_result_return_pattern (v : typed_pattern) : typed_pattern =
+let mk_result_ok_pattern (v : typed_pattern) : typed_pattern =
   let ty = TAdt (TAssumed TResult, mk_generic_args_from_types [ v.ty ]) in
-  let value =
-    PatAdt { variant_id = Some result_return_id; field_values = [ v ] }
-  in
+  let value = PatAdt { variant_id = Some result_ok_id; field_values = [ v ] } in
   { value; ty }
 
 let opt_unmeta_mplace (e : texpression) : mplace option * texpression =
@@ -791,6 +789,6 @@ let opt_destruct_ret (e : texpression) : texpression option =
           ty = _;
         },
         arg )
-    when variant_id = Some result_return_id ->
+    when variant_id = Some result_ok_id ->
       Some arg
   | _ -> None
diff --git a/compiler/SymbolicToPure.ml b/compiler/SymbolicToPure.ml
index 93f9ef75..15b52237 100644
--- a/compiler/SymbolicToPure.ml
+++ b/compiler/SymbolicToPure.ml
@@ -268,6 +268,22 @@ type bs_ctx = {
           Note that when a function contains a loop, we group the function symbolic AST and the loop symbolic
           AST in a single function.
        *)
+  mk_return : (bs_ctx -> texpression option -> texpression) option;
+      (** Small helper: translate a [return] expression, given a value to "return".
+          The translation of [return] depends on the context, and in particular depends on
+          whether we are inside a subexpression like a loop or not.
+
+          Note that the function consumes an optional expression, which is:
+          - [Some] for a forward computation
+          - [None] for a backward computation
+
+          We initialize this at [None].
+      *)
+  mk_panic : texpression option;
+      (** Small helper: translate a [fail] expression.
+
+           We initialize this at [None].
+       *)
 }
 [@@deriving show]
 
@@ -2012,54 +2028,7 @@ let rec translate_expression (e : S.expression) (ctx : bs_ctx) : texpression =
   | Loop loop -> translate_loop loop ctx
   | Error (meta, msg) -> translate_error meta msg
 
-and translate_panic (ctx : bs_ctx) : texpression =
-  (* Here we use the function return type - note that it is ok because
-   * we don't match on panics which happen inside the function body -
-   * but it won't be true anymore once we translate individual blocks *)
-  (* If we use a state monad, we need to add a lambda for the state variable *)
-  (* Note that only forward functions return a state *)
-  let effect_info = ctx_get_effect_info ctx in
-  (* TODO: we should use a [Fail] function *)
-  let mk_output output_ty =
-    if effect_info.stateful then
-      (* Create the [Fail] value *)
-      let ret_ty = mk_simpl_tuple_ty [ mk_state_ty; output_ty ] in
-      let ret_v =
-        mk_result_fail_texpression_with_error_id ctx.meta error_failure_id
-          ret_ty
-      in
-      ret_v
-    else
-      mk_result_fail_texpression_with_error_id ctx.meta error_failure_id
-        output_ty
-  in
-  if ctx.inside_loop && Option.is_some ctx.bid then
-    (* We are synthesizing the backward function of a loop body *)
-    let bid = Option.get ctx.bid in
-    let loop_id = Option.get ctx.loop_id in
-    let loop = LoopId.Map.find loop_id ctx.loops in
-    let tys = RegionGroupId.Map.find bid loop.back_outputs in
-    let output = mk_simpl_tuple_ty tys in
-    mk_output output
-  else
-    (* Regular function, or forward function (the forward translation for
-       a loop has the same return type as the parent function)
-    *)
-    match ctx.bid with
-    | None ->
-        let back_tys = compute_back_tys ctx.sg None in
-        let back_tys = List.filter_map (fun x -> x) back_tys in
-        let tys =
-          if ctx.sg.fwd_info.ignore_output then back_tys
-          else ctx.sg.fwd_output :: back_tys
-        in
-        let output = mk_simpl_tuple_ty tys in
-        mk_output output
-    | Some bid ->
-        let output =
-          mk_simpl_tuple_ty (RegionGroupId.Map.find bid ctx.sg.back_sg).outputs
-        in
-        mk_output output
+and translate_panic (ctx : bs_ctx) : texpression = Option.get ctx.mk_panic
 
 (** [opt_v]: the value to return, in case we translate a forward body.
 
@@ -2071,42 +2040,8 @@ and translate_panic (ctx : bs_ctx) : texpression =
 *)
 and translate_return (ectx : C.eval_ctx) (opt_v : V.typed_value option)
     (ctx : bs_ctx) : texpression =
-  (* There are two cases:
-     - either we reach the return of a forward function or a forward loop body,
-       in which case the optional value should be [Some] (it is the returned value)
-     - or we are translating a backward function, in which case it should be [None]
-  *)
-  (* Compute the values that we should return *without the state and the result
-     wrapper* *)
-  let output =
-    match ctx.bid with
-    | None ->
-        (* Forward function *)
-        let v = Option.get opt_v in
-        typed_value_to_texpression ctx ectx v
-    | Some _ ->
-        (* Backward function *)
-        (* Sanity check *)
-        sanity_check __FILE__ __LINE__ (opt_v = None) ctx.meta;
-        (* Group the variables in which we stored the values we need to give back.
-           See the explanations for the [SynthInput] case in [translate_end_abstraction] *)
-        let backward_outputs = Option.get ctx.backward_outputs in
-        let field_values = List.map mk_texpression_from_var backward_outputs in
-        mk_simpl_tuple_texpression ctx.meta field_values
-  in
-  (* We may need to return a state
-   * - error-monad: Return x
-   * - state-error: Return (state, x)
-   * *)
-  let effect_info = ctx_get_effect_info ctx in
-  let output =
-    if effect_info.stateful then
-      let state_rvalue = mk_state_texpression ctx.state_var in
-      mk_simpl_tuple_texpression ctx.meta [ state_rvalue; output ]
-    else output
-  in
-  (* Wrap in a result - TODO: check effect_info.can_fail to not always wrap *)
-  mk_result_return_texpression ctx.meta output
+  let opt_v = Option.map (typed_value_to_texpression ctx ectx) opt_v in
+  (Option.get ctx.mk_return) ctx opt_v
 
 and translate_return_with_loop (loop_id : V.LoopId.id) (is_continue : bool)
     (ctx : bs_ctx) : texpression =
@@ -2154,8 +2089,7 @@ and translate_return_with_loop (loop_id : V.LoopId.id) (is_continue : bool)
     else output
   in
   (* Wrap in a result - TODO: check effect_info.can_fail to not always wrap *)
-  mk_emeta (Tag "return_with_loop")
-    (mk_result_return_texpression ctx.meta output)
+  mk_emeta (Tag "return_with_loop") (mk_result_ok_texpression ctx.meta output)
 
 and translate_function_call (call : S.call) (e : S.expression) (ctx : bs_ctx) :
     texpression =
@@ -3123,6 +3057,49 @@ and translate_forward_end (ectx : C.eval_ctx)
                 (ctx, backward_inputs_no_state @ [ var ])
               else (ctx, backward_inputs_no_state)
             in
+            (* Update the functions mk_return and mk_panic *)
+            let effect_info = back_sg.effect_info in
+            let mk_return ctx v =
+              assert (v = None);
+              let output =
+                (* Group the variables in which we stored the values we need to give back.
+                   See the explanations for the [SynthInput] case in [translate_end_abstraction] *)
+                let backward_outputs = Option.get ctx.backward_outputs in
+                let field_values =
+                  List.map mk_texpression_from_var backward_outputs
+                in
+                mk_simpl_tuple_texpression ctx.meta field_values
+              in
+              let output =
+                if effect_info.stateful then
+                  let state_rvalue = mk_state_texpression ctx.state_var in
+                  mk_simpl_tuple_texpression ctx.meta [ state_rvalue; output ]
+                else output
+              in
+              (* Wrap in a result - TODO: check effect_info.can_fail to not always wrap *)
+              mk_result_ok_texpression ctx.meta output
+            in
+            let mk_panic =
+              (* TODO: we should use a [Fail] function *)
+              let mk_output output_ty =
+                if effect_info.stateful then
+                  (* Create the [Fail] value *)
+                  let ret_ty = mk_simpl_tuple_ty [ mk_state_ty; output_ty ] in
+                  let ret_v =
+                    mk_result_fail_texpression_with_error_id ctx.meta
+                      error_failure_id ret_ty
+                  in
+                  ret_v
+                else
+                  mk_result_fail_texpression_with_error_id ctx.meta
+                    error_failure_id output_ty
+              in
+              let output =
+                mk_simpl_tuple_ty
+                  (RegionGroupId.Map.find bid ctx.sg.back_sg).outputs
+              in
+              mk_output output
+            in
             {
               ctx with
               backward_inputs_no_state =
@@ -3131,6 +3108,8 @@ and translate_forward_end (ectx : C.eval_ctx)
               backward_inputs_with_state =
                 RegionGroupId.Map.add bid backward_inputs_with_state
                   ctx.backward_inputs_with_state;
+              mk_return = Some mk_return;
+              mk_panic = Some mk_panic;
             }
           in
 
@@ -3230,7 +3209,7 @@ and translate_forward_end (ectx : C.eval_ctx)
 
     let state_var = List.map mk_texpression_from_var state_var in
     let ret = mk_simpl_tuple_texpression ctx.meta (state_var @ [ ret ]) in
-    let ret = mk_result_return_texpression ctx.meta ret in
+    let ret = mk_result_ok_texpression ctx.meta ret in
 
     (* Introduce all the let-bindings *)
 
@@ -3475,7 +3454,6 @@ and translate_loop (loop : S.loop) (ctx : bs_ctx) : texpression =
   in
 
   (* Compute the backward outputs *)
-  let ctx = ref ctx in
   let rg_to_given_back_tys =
     RegionGroupId.Map.map
       (fun tys ->
@@ -3483,13 +3461,12 @@ and translate_loop (loop : S.loop) (ctx : bs_ctx) : texpression =
         List.map
           (fun ty ->
             cassert __FILE__ __LINE__
-              (not (TypesUtils.ty_has_borrows !ctx.type_ctx.type_infos ty))
-              !ctx.meta "The types shouldn't contain borrows";
-            ctx_translate_fwd_ty !ctx ty)
+              (not (TypesUtils.ty_has_borrows ctx.type_ctx.type_infos ty))
+              ctx.meta "The types shouldn't contain borrows";
+            ctx_translate_fwd_ty ctx ty)
           tys)
       loop.rg_to_given_back_tys
   in
-  let ctx = !ctx in
 
   (* The output type of the loop function *)
   let fwd_effect_info = { ctx.sg.fwd_info.effect_info with is_rec = true } in
@@ -3594,6 +3571,44 @@ and translate_loop (loop : S.loop) (ctx : bs_ctx) : texpression =
       { types; const_generics; trait_refs }
     in
 
+    (* Update the helpers to translate the fail and return expressions *)
+    let mk_panic =
+      (* Note that we reuse the effect information from the parent function *)
+      let effect_info = ctx_get_effect_info ctx in
+      let back_tys = compute_back_tys ctx.sg None in
+      let back_tys = List.filter_map (fun x -> x) back_tys in
+      let tys =
+        if ctx.sg.fwd_info.ignore_output then back_tys
+        else ctx.sg.fwd_output :: back_tys
+      in
+      let output_ty = mk_simpl_tuple_ty tys in
+      if effect_info.stateful then
+        (* Create the [Fail] value *)
+        let ret_ty = mk_simpl_tuple_ty [ mk_state_ty; output_ty ] in
+        let ret_v =
+          mk_result_fail_texpression_with_error_id ctx.meta error_failure_id
+            ret_ty
+        in
+        ret_v
+      else
+        mk_result_fail_texpression_with_error_id ctx.meta error_failure_id
+          output_ty
+    in
+    let mk_return ctx v =
+      match v with
+      | None -> raise (Failure "Unexpected")
+      | Some output ->
+          let effect_info = ctx_get_effect_info ctx in
+          let output =
+            if effect_info.stateful then
+              let state_rvalue = mk_state_texpression ctx.state_var in
+              mk_simpl_tuple_texpression ctx.meta [ state_rvalue; output ]
+            else output
+          in
+          (* Wrap in a result - TODO: check effect_info.can_fail to not always wrap *)
+          mk_result_ok_texpression ctx.meta output
+    in
+
     let loop_info =
       {
         loop_id;
@@ -3609,7 +3624,7 @@ and translate_loop (loop : S.loop) (ctx : bs_ctx) : texpression =
       }
     in
     let loops = LoopId.Map.add loop_id loop_info ctx.loops in
-    { ctx with loops }
+    { ctx with loops; mk_return = Some mk_return; mk_panic = Some mk_panic }
   in
 
   (* Update the context to translate the function end *)
@@ -3776,6 +3791,50 @@ let translate_fun_decl (ctx : bs_ctx) (body : S.expression option) : fun_decl =
         let effect_info =
           get_fun_effect_info ctx (FunId (FRegular def_id)) None None
         in
+        let mk_return ctx v =
+          match v with
+          | None ->
+              raise
+                (Failure
+                   "Unexpected: reached a return expression without value in a \
+                    function forward expression")
+          | Some output ->
+              let output =
+                if effect_info.stateful then
+                  let state_rvalue = mk_state_texpression ctx.state_var in
+                  mk_simpl_tuple_texpression ctx.meta [ state_rvalue; output ]
+                else output
+              in
+              (* Wrap in a result - TODO: check effect_info.can_fail to not always wrap *)
+              mk_result_ok_texpression ctx.meta output
+        in
+        let mk_panic =
+          (* TODO: we should use a [Fail] function *)
+          let mk_output output_ty =
+            if effect_info.stateful then
+              (* Create the [Fail] value *)
+              let ret_ty = mk_simpl_tuple_ty [ mk_state_ty; output_ty ] in
+              let ret_v =
+                mk_result_fail_texpression_with_error_id ctx.meta
+                  error_failure_id ret_ty
+              in
+              ret_v
+            else
+              mk_result_fail_texpression_with_error_id ctx.meta error_failure_id
+                output_ty
+          in
+          let back_tys = compute_back_tys ctx.sg None in
+          let back_tys = List.filter_map (fun x -> x) back_tys in
+          let tys =
+            if ctx.sg.fwd_info.ignore_output then back_tys
+            else ctx.sg.fwd_output :: back_tys
+          in
+          let output = mk_simpl_tuple_ty tys in
+          mk_output output
+        in
+        let ctx =
+          { ctx with mk_return = Some mk_return; mk_panic = Some mk_panic }
+        in
         let body = translate_expression body ctx in
         (* Add a match over the fuel, if necessary *)
         let body =
diff --git a/compiler/Translate.ml b/compiler/Translate.ml
index 870f8a22..9460c5f4 100644
--- a/compiler/Translate.ml
+++ b/compiler/Translate.ml
@@ -158,6 +158,8 @@ let translate_function_to_pure_aux (trans_ctx : trans_ctx)
       inside_loop = false;
       loop_ids_map;
       loops = Pure.LoopId.Map.empty;
+      mk_return = None;
+      mk_panic = None;
     }
   in
 
diff --git a/tests/coq/arrays/Arrays.v b/tests/coq/arrays/Arrays.v
index 049d63cb..c9696147 100644
--- a/tests/coq/arrays/Arrays.v
+++ b/tests/coq/arrays/Arrays.v
@@ -36,19 +36,19 @@ Definition array_to_mut_slice_
 (** [arrays::array_len]:
     Source: 'src/arrays.rs', lines 25:0-25:40 *)
 Definition array_len (T : Type) (s : array T 32%usize) : result usize :=
-  s1 <- array_to_slice T 32%usize s; Return (slice_len T s1)
+  s1 <- array_to_slice T 32%usize s; Ok (slice_len T s1)
 .
 
 (** [arrays::shared_array_len]:
     Source: 'src/arrays.rs', lines 29:0-29:48 *)
 Definition shared_array_len (T : Type) (s : array T 32%usize) : result usize :=
-  s1 <- array_to_slice T 32%usize s; Return (slice_len T s1)
+  s1 <- array_to_slice T 32%usize s; Ok (slice_len T s1)
 .
 
 (** [arrays::shared_slice_len]:
     Source: 'src/arrays.rs', lines 33:0-33:44 *)
 Definition shared_slice_len (T : Type) (s : slice T) : result usize :=
-  Return (slice_len T s)
+  Ok (slice_len T s)
 .
 
 (** [arrays::index_array_shared]:
@@ -114,7 +114,7 @@ Definition slice_subslice_mut_
       (core_slice_index_SliceIndexRangeUsizeSliceTInst u32) x
       {| core_ops_range_Range_start := y; core_ops_range_Range_end_ := z |};
   let (s, index_mut_back) := p in
-  Return (s, index_mut_back)
+  Ok (s, index_mut_back)
 .
 
 (** [arrays::array_to_slice_shared_]:
@@ -155,7 +155,7 @@ Definition array_subslice_mut_
       (core_slice_index_SliceIndexRangeUsizeSliceTInst u32)) x
       {| core_ops_range_Range_start := y; core_ops_range_Range_end_ := z |};
   let (s, index_mut_back) := p in
-  Return (s, index_mut_back)
+  Ok (s, index_mut_back)
 .
 
 (** [arrays::index_slice_0]:
@@ -192,47 +192,46 @@ Definition update_update_array
   let (_, index_mut_back1) := p1 in
   a1 <- index_mut_back1 0%u32;
   _ <- index_mut_back a1;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::array_local_deep_copy]:
     Source: 'src/arrays.rs', lines 118:0-118:43 *)
 Definition array_local_deep_copy (x : array u32 32%usize) : result unit :=
-  Return tt
+  Ok tt
 .
 
 (** [arrays::take_array]:
     Source: 'src/arrays.rs', lines 122:0-122:30 *)
 Definition take_array (a : array u32 2%usize) : result unit :=
-  Return tt.
+  Ok tt.
 
 (** [arrays::take_array_borrow]:
     Source: 'src/arrays.rs', lines 123:0-123:38 *)
 Definition take_array_borrow (a : array u32 2%usize) : result unit :=
-  Return tt
-.
+  Ok tt.
 
 (** [arrays::take_slice]:
     Source: 'src/arrays.rs', lines 124:0-124:28 *)
 Definition take_slice (s : slice u32) : result unit :=
-  Return tt.
+  Ok tt.
 
 (** [arrays::take_mut_slice]:
     Source: 'src/arrays.rs', lines 125:0-125:36 *)
 Definition take_mut_slice (s : slice u32) : result (slice u32) :=
-  Return s.
+  Ok s.
 
 (** [arrays::const_array]:
     Source: 'src/arrays.rs', lines 127:0-127:32 *)
 Definition const_array : result (array u32 2%usize) :=
-  Return (mk_array u32 2%usize [ 0%u32; 0%u32 ])
+  Ok (mk_array u32 2%usize [ 0%u32; 0%u32 ])
 .
 
 (** [arrays::const_slice]:
     Source: 'src/arrays.rs', lines 131:0-131:20 *)
 Definition const_slice : result unit :=
   _ <- array_to_slice u32 2%usize (mk_array u32 2%usize [ 0%u32; 0%u32 ]);
-  Return tt
+  Ok tt
 .
 
 (** [arrays::take_all]:
@@ -247,7 +246,7 @@ Definition take_all : result unit :=
   let (s1, to_slice_mut_back) := p in
   s2 <- take_mut_slice s1;
   _ <- to_slice_mut_back s2;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::index_array]:
@@ -272,7 +271,7 @@ Definition index_slice_u32_0 (x : slice u32) : result u32 :=
     Source: 'src/arrays.rs', lines 166:0-166:50 *)
 Definition index_mut_slice_u32_0
   (x : slice u32) : result (u32 * (slice u32)) :=
-  i <- slice_index_usize u32 x 0%usize; Return (i, x)
+  i <- slice_index_usize u32 x 0%usize; Ok (i, x)
 .
 
 (** [arrays::index_all]:
@@ -292,7 +291,7 @@ Definition index_all : result u32 :=
   let (i7, s2) := p1 in
   i8 <- u32_add i6 i7;
   _ <- to_slice_mut_back s2;
-  Return i8
+  Ok i8
 .
 
 (** [arrays::update_array]:
@@ -301,7 +300,7 @@ Definition update_array (x : array u32 2%usize) : result unit :=
   p <- array_index_mut_usize u32 2%usize x 0%usize;
   let (_, index_mut_back) := p in
   _ <- index_mut_back 1%u32;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::update_array_mut_borrow]:
@@ -331,7 +330,7 @@ Definition update_all : result unit :=
   let (s, to_slice_mut_back) := p in
   s1 <- update_mut_slice s;
   _ <- to_slice_mut_back s1;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::range_all]:
@@ -349,7 +348,7 @@ Definition range_all : result unit :=
   let (s, index_mut_back) := p in
   s1 <- update_mut_slice s;
   _ <- index_mut_back s1;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::deref_array_borrow]:
@@ -362,13 +361,13 @@ Definition deref_array_borrow (x : array u32 2%usize) : result u32 :=
     Source: 'src/arrays.rs', lines 219:0-219:54 *)
 Definition deref_array_mut_borrow
   (x : array u32 2%usize) : result (u32 * (array u32 2%usize)) :=
-  i <- array_index_usize u32 2%usize x 0%usize; Return (i, x)
+  i <- array_index_usize u32 2%usize x 0%usize; Ok (i, x)
 .
 
 (** [arrays::take_array_t]:
     Source: 'src/arrays.rs', lines 227:0-227:31 *)
 Definition take_array_t (a : array AB_t 2%usize) : result unit :=
-  Return tt.
+  Ok tt.
 
 (** [arrays::non_copyable_array]:
     Source: 'src/arrays.rs', lines 229:0-229:27 *)
@@ -390,7 +389,7 @@ Fixpoint sum_loop
       sum3 <- u32_add sum1 i2;
       i3 <- usize_add i 1%usize;
       sum_loop n1 s sum3 i3)
-    else Return sum1
+    else Ok sum1
   end
 .
 
@@ -418,7 +417,7 @@ Fixpoint sum2_loop
       sum3 <- u32_add sum1 i4;
       i5 <- usize_add i 1%usize;
       sum2_loop n1 s s2 sum3 i5)
-    else Return sum1
+    else Ok sum1
   end
 .
 
@@ -439,7 +438,7 @@ Definition f0 : result unit :=
   let (_, index_mut_back) := p1 in
   s1 <- index_mut_back 1%u32;
   _ <- to_slice_mut_back s1;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::f1]:
@@ -450,13 +449,13 @@ Definition f1 : result unit :=
       0%usize;
   let (_, index_mut_back) := p in
   _ <- index_mut_back 1%u32;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::f2]:
     Source: 'src/arrays.rs', lines 273:0-273:17 *)
 Definition f2 (i : u32) : result unit :=
-  Return tt.
+  Ok tt.
 
 (** [arrays::f4]:
     Source: 'src/arrays.rs', lines 282:0-282:54 *)
@@ -483,7 +482,7 @@ Definition f3 (n : nat) : result u32 :=
 
 (** [arrays::SZ]
     Source: 'src/arrays.rs', lines 286:0-286:19 *)
-Definition sz_body : result usize := Return 32%usize.
+Definition sz_body : result usize := Ok 32%usize.
 Definition sz : usize := sz_body%global.
 
 (** [arrays::f5]:
@@ -505,7 +504,7 @@ Definition ite : result unit :=
   let (_, s3) := p3 in
   _ <- to_slice_mut_back1 s3;
   _ <- to_slice_mut_back s1;
-  Return tt
+  Ok tt
 .
 
 (** [arrays::zero_slice]: loop 0:
@@ -522,7 +521,7 @@ Fixpoint zero_slice_loop
       i1 <- usize_add i 1%usize;
       a1 <- index_mut_back 0%u8;
       zero_slice_loop n1 a1 i1 len)
-    else Return a
+    else Ok a
   end
 .
 
@@ -541,14 +540,14 @@ Fixpoint iter_mut_slice_loop
   | S n1 =>
     if i s< len
     then (i1 <- usize_add i 1%usize; iter_mut_slice_loop n1 len i1)
-    else Return tt
+    else Ok tt
   end
 .
 
 (** [arrays::iter_mut_slice]:
     Source: 'src/arrays.rs', lines 312:0-312:35 *)
 Definition iter_mut_slice (n : nat) (a : slice u8) : result (slice u8) :=
-  let len := slice_len u8 a in _ <- iter_mut_slice_loop n len 0%usize; Return a
+  let len := slice_len u8 a in _ <- iter_mut_slice_loop n len 0%usize; Ok a
 .
 
 (** [arrays::sum_mut_slice]: loop 0:
@@ -565,7 +564,7 @@ Fixpoint sum_mut_slice_loop
       s1 <- u32_add s i2;
       i3 <- usize_add i 1%usize;
       sum_mut_slice_loop n1 a i3 s1)
-    else Return s
+    else Ok s
   end
 .
 
@@ -573,7 +572,7 @@ Fixpoint sum_mut_slice_loop
     Source: 'src/arrays.rs', lines 320:0-320:42 *)
 Definition sum_mut_slice
   (n : nat) (a : slice u32) : result (u32 * (slice u32)) :=
-  i <- sum_mut_slice_loop n a 0%usize 0%u32; Return (i, a)
+  i <- sum_mut_slice_loop n a 0%usize 0%u32; Ok (i, a)
 .
 
 End Arrays.
diff --git a/tests/coq/arrays/Primitives.v b/tests/coq/arrays/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/arrays/Primitives.v
+++ b/tests/coq/arrays/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/betree/BetreeMain_Funs.v b/tests/coq/betree/BetreeMain_Funs.v
index 9256b149..80518eab 100644
--- a/tests/coq/betree/BetreeMain_Funs.v
+++ b/tests/coq/betree/BetreeMain_Funs.v
@@ -49,13 +49,13 @@ Definition betree_store_leaf_node
 (** [betree_main::betree::fresh_node_id]:
     Source: 'src/betree.rs', lines 55:0-55:48 *)
 Definition betree_fresh_node_id (counter : u64) : result (u64 * u64) :=
-  counter1 <- u64_add counter 1%u64; Return (counter, counter1)
+  counter1 <- u64_add counter 1%u64; Ok (counter, counter1)
 .
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::new]:
     Source: 'src/betree.rs', lines 206:4-206:20 *)
 Definition betree_NodeIdCounter_new : result betree_NodeIdCounter_t :=
-  Return {| betree_NodeIdCounter_next_node_id := 0%u64 |}
+  Ok {| betree_NodeIdCounter_next_node_id := 0%u64 |}
 .
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::fresh_id]:
@@ -63,7 +63,7 @@ Definition betree_NodeIdCounter_new : result betree_NodeIdCounter_t :=
 Definition betree_NodeIdCounter_fresh_id
   (self : betree_NodeIdCounter_t) : result (u64 * betree_NodeIdCounter_t) :=
   i <- u64_add self.(betree_NodeIdCounter_next_node_id) 1%u64;
-  Return (self.(betree_NodeIdCounter_next_node_id),
+  Ok (self.(betree_NodeIdCounter_next_node_id),
     {| betree_NodeIdCounter_next_node_id := i |})
 .
 
@@ -74,16 +74,16 @@ Definition betree_upsert_update
   match prev with
   | None =>
     match st with
-    | Betree_UpsertFunState_Add v => Return v
-    | Betree_UpsertFunState_Sub _ => Return 0%u64
+    | Betree_UpsertFunState_Add v => Ok v
+    | Betree_UpsertFunState_Sub _ => Ok 0%u64
     end
   | Some prev1 =>
     match st with
     | Betree_UpsertFunState_Add v =>
       margin <- u64_sub core_u64_max prev1;
-      if margin s>= v then u64_add prev1 v else Return core_u64_max
+      if margin s>= v then u64_add prev1 v else Ok core_u64_max
     | Betree_UpsertFunState_Sub v =>
-      if prev1 s>= v then u64_sub prev1 v else Return 0%u64
+      if prev1 s>= v then u64_sub prev1 v else Ok 0%u64
     end
   end
 .
@@ -97,7 +97,7 @@ Fixpoint betree_List_len
   | S n1 =>
     match self with
     | Betree_List_Cons _ tl => i <- betree_List_len T n1 tl; u64_add 1%u64 i
-    | Betree_List_Nil => Return 0%u64
+    | Betree_List_Nil => Ok 0%u64
     end
   end
 .
@@ -112,14 +112,14 @@ Fixpoint betree_List_split_at
   | O => Fail_ OutOfFuel
   | S n2 =>
     if n1 s= 0%u64
-    then Return (Betree_List_Nil, self)
+    then Ok (Betree_List_Nil, self)
     else
       match self with
       | Betree_List_Cons hd tl =>
         i <- u64_sub n1 1%u64;
         p <- betree_List_split_at T n2 tl i;
         let (ls0, ls1) := p in
-        Return (Betree_List_Cons hd ls0, ls1)
+        Ok (Betree_List_Cons hd ls0, ls1)
       | Betree_List_Nil => Fail_ Failure
       end
   end
@@ -130,7 +130,7 @@ Fixpoint betree_List_split_at
 Definition betree_List_push_front
   (T : Type) (self : betree_List_t T) (x : T) : result (betree_List_t T) :=
   let (tl, _) := core_mem_replace (betree_List_t T) self Betree_List_Nil in
-  Return (Betree_List_Cons x tl)
+  Ok (Betree_List_Cons x tl)
 .
 
 (** [betree_main::betree::{betree_main::betree::List<T>#1}::pop_front]:
@@ -139,7 +139,7 @@ Definition betree_List_pop_front
   (T : Type) (self : betree_List_t T) : result (T * (betree_List_t T)) :=
   let (ls, _) := core_mem_replace (betree_List_t T) self Betree_List_Nil in
   match ls with
-  | Betree_List_Cons x tl => Return (x, tl)
+  | Betree_List_Cons x tl => Ok (x, tl)
   | Betree_List_Nil => Fail_ Failure
   end
 .
@@ -148,7 +148,7 @@ Definition betree_List_pop_front
     Source: 'src/betree.rs', lines 318:4-318:22 *)
 Definition betree_List_hd (T : Type) (self : betree_List_t T) : result T :=
   match self with
-  | Betree_List_Cons hd _ => Return hd
+  | Betree_List_Cons hd _ => Ok hd
   | Betree_List_Nil => Fail_ Failure
   end
 .
@@ -158,8 +158,8 @@ Definition betree_List_hd (T : Type) (self : betree_List_t T) : result T :=
 Definition betree_ListPairU64T_head_has_key
   (T : Type) (self : betree_List_t (u64 * T)) (key : u64) : result bool :=
   match self with
-  | Betree_List_Cons hd _ => let (i, _) := hd in Return (i s= key)
-  | Betree_List_Nil => Return false
+  | Betree_List_Cons hd _ => let (i, _) := hd in Ok (i s= key)
+  | Betree_List_Nil => Ok false
   end
 .
 
@@ -176,12 +176,12 @@ Fixpoint betree_ListPairU64T_partition_at_pivot
     | Betree_List_Cons hd tl =>
       let (i, t) := hd in
       if i s>= pivot
-      then Return (Betree_List_Nil, Betree_List_Cons (i, t) tl)
+      then Ok (Betree_List_Nil, Betree_List_Cons (i, t) tl)
       else (
         p <- betree_ListPairU64T_partition_at_pivot T n1 tl pivot;
         let (ls0, ls1) := p in
-        Return (Betree_List_Cons (i, t) ls0, ls1))
-    | Betree_List_Nil => Return (Betree_List_Nil, Betree_List_Nil)
+        Ok (Betree_List_Cons (i, t) ls0, ls1))
+    | Betree_List_Nil => Ok (Betree_List_Nil, Betree_List_Nil)
     end
   end
 .
@@ -218,7 +218,7 @@ Definition betree_Leaf_split
       betree_Leaf_id := id1;
       betree_Leaf_size := params.(betree_Params_split_size)
     |} in
-  Return (st2, (mkbetree_Internal_t self.(betree_Leaf_id) pivot n1 n2,
+  Ok (st2, (mkbetree_Internal_t self.(betree_Leaf_id) pivot n1 n2,
     node_id_cnt2))
 .
 
@@ -236,16 +236,16 @@ Fixpoint betree_Node_lookup_first_message_for_key
     | Betree_List_Cons x next_msgs =>
       let (i, m) := x in
       if i s>= key
-      then Return (Betree_List_Cons (i, m) next_msgs, Return)
+      then Ok (Betree_List_Cons (i, m) next_msgs, Ok)
       else (
         p <- betree_Node_lookup_first_message_for_key n1 key next_msgs;
         let (l, lookup_first_message_for_key_back) := p in
         let back :=
           fun (ret : betree_List_t (u64 * betree_Message_t)) =>
             next_msgs1 <- lookup_first_message_for_key_back ret;
-            Return (Betree_List_Cons (i, m) next_msgs1) in
-        Return (l, back))
-    | Betree_List_Nil => Return (Betree_List_Nil, Return)
+            Ok (Betree_List_Cons (i, m) next_msgs1) in
+        Ok (l, back))
+    | Betree_List_Nil => Ok (Betree_List_Nil, Ok)
     end
   end
 .
@@ -263,12 +263,10 @@ Fixpoint betree_Node_lookup_in_bindings
     | Betree_List_Cons hd tl =>
       let (i, i1) := hd in
       if i s= key
-      then Return (Some i1)
+      then Ok (Some i1)
       else
-        if i s> key
-        then Return None
-        else betree_Node_lookup_in_bindings n1 key tl
-    | Betree_List_Nil => Return None
+        if i s> key then Ok None else betree_Node_lookup_in_bindings n1 key tl
+    | Betree_List_Nil => Ok None
     end
   end
 .
@@ -302,7 +300,7 @@ Fixpoint betree_Node_apply_upserts
       msgs1 <-
         betree_List_push_front (u64 * betree_Message_t) msgs (key,
           Betree_Message_Insert v);
-      Return (st1, (v, msgs1)))
+      Ok (st1, (v, msgs1)))
   end
 .
 
@@ -320,13 +318,13 @@ Fixpoint betree_Internal_lookup_in_children
       p <- betree_Node_lookup n1 self.(betree_Internal_left) key st;
       let (st1, p1) := p in
       let (o, n2) := p1 in
-      Return (st1, (o, mkbetree_Internal_t self.(betree_Internal_id)
+      Ok (st1, (o, mkbetree_Internal_t self.(betree_Internal_id)
         self.(betree_Internal_pivot) n2 self.(betree_Internal_right))))
     else (
       p <- betree_Node_lookup n1 self.(betree_Internal_right) key st;
       let (st1, p1) := p in
       let (o, n2) := p1 in
-      Return (st1, (o, mkbetree_Internal_t self.(betree_Internal_id)
+      Ok (st1, (o, mkbetree_Internal_t self.(betree_Internal_id)
         self.(betree_Internal_pivot) self.(betree_Internal_left) n2)))
   end
 
@@ -354,19 +352,19 @@ with betree_Node_lookup
           let (st2, p4) := p3 in
           let (o, node1) := p4 in
           _ <- lookup_first_message_for_key_back (Betree_List_Cons (k, msg) l);
-          Return (st2, (o, Betree_Node_Internal node1)))
+          Ok (st2, (o, Betree_Node_Internal node1)))
         else
           match msg with
           | Betree_Message_Insert v =>
             _ <-
               lookup_first_message_for_key_back (Betree_List_Cons (k,
                 Betree_Message_Insert v) l);
-            Return (st1, (Some v, Betree_Node_Internal node))
+            Ok (st1, (Some v, Betree_Node_Internal node))
           | Betree_Message_Delete =>
             _ <-
               lookup_first_message_for_key_back (Betree_List_Cons (k,
                 Betree_Message_Delete) l);
-            Return (st1, (None, Betree_Node_Internal node))
+            Ok (st1, (None, Betree_Node_Internal node))
           | Betree_Message_Upsert ufs =>
             p3 <- betree_Internal_lookup_in_children n1 node key st1;
             let (st2, p4) := p3 in
@@ -380,20 +378,20 @@ with betree_Node_lookup
             p7 <-
               betree_store_internal_node node1.(betree_Internal_id) msgs1 st3;
             let (st4, _) := p7 in
-            Return (st4, (Some v1, Betree_Node_Internal node1))
+            Ok (st4, (Some v1, Betree_Node_Internal node1))
           end
       | Betree_List_Nil =>
         p2 <- betree_Internal_lookup_in_children n1 node key st1;
         let (st2, p3) := p2 in
         let (o, node1) := p3 in
         _ <- lookup_first_message_for_key_back Betree_List_Nil;
-        Return (st2, (o, Betree_Node_Internal node1))
+        Ok (st2, (o, Betree_Node_Internal node1))
       end
     | Betree_Node_Leaf node =>
       p <- betree_load_leaf_node node.(betree_Leaf_id) st;
       let (st1, bindings) := p in
       o <- betree_Node_lookup_in_bindings n1 key bindings;
-      Return (st1, (o, Betree_Node_Leaf node))
+      Ok (st1, (o, Betree_Node_Leaf node))
     end
   end
 .
@@ -417,8 +415,8 @@ Fixpoint betree_Node_filter_messages_for_key
             m) l);
         let (_, msgs1) := p1 in
         betree_Node_filter_messages_for_key n1 key msgs1)
-      else Return (Betree_List_Cons (k, m) l)
-    | Betree_List_Nil => Return Betree_List_Nil
+      else Ok (Betree_List_Cons (k, m) l)
+    | Betree_List_Nil => Ok Betree_List_Nil
     end
   end
 .
@@ -443,10 +441,10 @@ Fixpoint betree_Node_lookup_first_message_after_key
         let back :=
           fun (ret : betree_List_t (u64 * betree_Message_t)) =>
             next_msgs1 <- lookup_first_message_after_key_back ret;
-            Return (Betree_List_Cons (k, m) next_msgs1) in
-        Return (l, back))
-      else Return (Betree_List_Cons (k, m) next_msgs, Return)
-    | Betree_List_Nil => Return (Betree_List_Nil, Return)
+            Ok (Betree_List_Cons (k, m) next_msgs1) in
+        Ok (l, back))
+      else Ok (Betree_List_Cons (k, m) next_msgs, Ok)
+    | Betree_List_Nil => Ok (Betree_List_Nil, Ok)
     end
   end
 .
@@ -527,7 +525,7 @@ Fixpoint betree_Node_apply_messages_to_internal
       let (i, m) := new_msg in
       msgs1 <- betree_Node_apply_to_internal n1 msgs i m;
       betree_Node_apply_messages_to_internal n1 msgs1 new_msgs_tl
-    | Betree_List_Nil => Return msgs
+    | Betree_List_Nil => Ok msgs
     end
   end
 .
@@ -546,16 +544,16 @@ Fixpoint betree_Node_lookup_mut_in_bindings
     | Betree_List_Cons hd tl =>
       let (i, i1) := hd in
       if i s>= key
-      then Return (Betree_List_Cons (i, i1) tl, Return)
+      then Ok (Betree_List_Cons (i, i1) tl, Ok)
       else (
         p <- betree_Node_lookup_mut_in_bindings n1 key tl;
         let (l, lookup_mut_in_bindings_back) := p in
         let back :=
           fun (ret : betree_List_t (u64 * u64)) =>
             tl1 <- lookup_mut_in_bindings_back ret;
-            Return (Betree_List_Cons (i, i1) tl1) in
-        Return (l, back))
-    | Betree_List_Nil => Return (Betree_List_Nil, Return)
+            Ok (Betree_List_Cons (i, i1) tl1) in
+        Ok (l, back))
+    | Betree_List_Nil => Ok (Betree_List_Nil, Ok)
     end
   end
 .
@@ -613,7 +611,7 @@ Fixpoint betree_Node_apply_messages_to_leaf
       let (i, m) := new_msg in
       bindings1 <- betree_Node_apply_to_leaf n1 bindings i m;
       betree_Node_apply_messages_to_leaf n1 bindings1 new_msgs_tl
-    | Betree_List_Nil => Return bindings
+    | Betree_List_Nil => Ok bindings
     end
   end
 .
@@ -650,20 +648,20 @@ Fixpoint betree_Internal_flush
             node_id_cnt1 msgs_right st1;
         let (st2, p4) := p3 in
         let (n3, node_id_cnt2) := p4 in
-        Return (st2, (Betree_List_Nil, (mkbetree_Internal_t
+        Ok (st2, (Betree_List_Nil, (mkbetree_Internal_t
           self.(betree_Internal_id) self.(betree_Internal_pivot) n2 n3,
           node_id_cnt2))))
       else
-        Return (st1, (msgs_right, (mkbetree_Internal_t
-          self.(betree_Internal_id) self.(betree_Internal_pivot) n2
-          self.(betree_Internal_right), node_id_cnt1))))
+        Ok (st1, (msgs_right, (mkbetree_Internal_t self.(betree_Internal_id)
+          self.(betree_Internal_pivot) n2 self.(betree_Internal_right),
+          node_id_cnt1))))
     else (
       p1 <-
         betree_Node_apply_messages n1 self.(betree_Internal_right) params
           node_id_cnt msgs_right st;
       let (st1, p2) := p1 in
       let (n2, node_id_cnt1) := p2 in
-      Return (st1, (msgs_left, (mkbetree_Internal_t self.(betree_Internal_id)
+      Ok (st1, (msgs_left, (mkbetree_Internal_t self.(betree_Internal_id)
         self.(betree_Internal_pivot) self.(betree_Internal_left) n2,
         node_id_cnt1))))
   end
@@ -694,12 +692,12 @@ with betree_Node_apply_messages
         p4 <-
           betree_store_internal_node node1.(betree_Internal_id) content2 st2;
         let (st3, _) := p4 in
-        Return (st3, (Betree_Node_Internal node1, node_id_cnt1)))
+        Ok (st3, (Betree_Node_Internal node1, node_id_cnt1)))
       else (
         p1 <-
           betree_store_internal_node node.(betree_Internal_id) content1 st1;
         let (st2, _) := p1 in
-        Return (st2, (Betree_Node_Internal node, node_id_cnt)))
+        Ok (st2, (Betree_Node_Internal node, node_id_cnt)))
     | Betree_Node_Leaf node =>
       p <- betree_load_leaf_node node.(betree_Leaf_id) st;
       let (st1, content) := p in
@@ -713,11 +711,11 @@ with betree_Node_apply_messages
         let (new_node, node_id_cnt1) := p2 in
         p3 <- betree_store_leaf_node node.(betree_Leaf_id) Betree_List_Nil st2;
         let (st3, _) := p3 in
-        Return (st3, (Betree_Node_Internal new_node, node_id_cnt1)))
+        Ok (st3, (Betree_Node_Internal new_node, node_id_cnt1)))
       else (
         p1 <- betree_store_leaf_node node.(betree_Leaf_id) content1 st1;
         let (st2, _) := p1 in
-        Return (st2, (Betree_Node_Leaf
+        Ok (st2, (Betree_Node_Leaf
           {| betree_Leaf_id := node.(betree_Leaf_id); betree_Leaf_size := len
           |}, node_id_cnt)))
     end
@@ -737,7 +735,7 @@ Definition betree_Node_apply
       (key, new_msg) Betree_List_Nil) st;
   let (st1, p1) := p in
   let (self1, node_id_cnt1) := p1 in
-  Return (st1, (self1, node_id_cnt1))
+  Ok (st1, (self1, node_id_cnt1))
 .
 
 (** [betree_main::betree::{betree_main::betree::BeTree#6}::new]:
@@ -751,7 +749,7 @@ Definition betree_BeTree_new
   let (id, node_id_cnt1) := p in
   p1 <- betree_store_leaf_node id Betree_List_Nil st;
   let (st1, _) := p1 in
-  Return (st1,
+  Ok (st1,
     {|
       betree_BeTree_params :=
         {|
@@ -777,7 +775,7 @@ Definition betree_BeTree_apply
       self.(betree_BeTree_node_id_cnt) key msg st;
   let (st1, p1) := p in
   let (n1, nic) := p1 in
-  Return (st1,
+  Ok (st1,
     {|
       betree_BeTree_params := self.(betree_BeTree_params);
       betree_BeTree_node_id_cnt := nic;
@@ -822,7 +820,7 @@ Definition betree_BeTree_lookup
   p <- betree_Node_lookup n self.(betree_BeTree_root) key st;
   let (st1, p1) := p in
   let (o, n1) := p1 in
-  Return (st1, (o,
+  Ok (st1, (o,
     {|
       betree_BeTree_params := self.(betree_BeTree_params);
       betree_BeTree_node_id_cnt := self.(betree_BeTree_node_id_cnt);
@@ -833,7 +831,7 @@ Definition betree_BeTree_lookup
 (** [betree_main::main]:
     Source: 'src/betree_main.rs', lines 5:0-5:9 *)
 Definition main : result unit :=
-  Return tt.
+  Ok tt.
 
 (** Unit test for [betree_main::main] *)
 Check (main )%return.
diff --git a/tests/coq/betree/Primitives.v b/tests/coq/betree/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/betree/Primitives.v
+++ b/tests/coq/betree/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/demo/Demo.v b/tests/coq/demo/Demo.v
index abec8e88..00b9b889 100644
--- a/tests/coq/demo/Demo.v
+++ b/tests/coq/demo/Demo.v
@@ -13,8 +13,8 @@ Module Demo.
 Definition choose
   (T : Type) (b : bool) (x : T) (y : T) : result (T * (T -> result (T * T))) :=
   if b
-  then let back := fun (ret : T) => Return (ret, y) in Return (x, back)
-  else let back := fun (ret : T) => Return (x, ret) in Return (y, back)
+  then let back := fun (ret : T) => Ok (ret, y) in Ok (x, back)
+  else let back := fun (ret : T) => Ok (x, ret) in Ok (y, back)
 .
 
 (** [demo::mul2_add1]:
@@ -37,7 +37,7 @@ Definition incr (x : u32) : result u32 :=
 (** [demo::use_incr]:
     Source: 'src/demo.rs', lines 25:0-25:17 *)
 Definition use_incr : result unit :=
-  x <- incr 0%u32; x1 <- incr x; _ <- incr x1; Return tt
+  x <- incr 0%u32; x1 <- incr x; _ <- incr x1; Ok tt
 .
 
 (** [demo::CList]
@@ -58,9 +58,7 @@ Fixpoint list_nth (T : Type) (n : nat) (l : CList_t T) (i : u32) : result T :=
   | S n1 =>
     match l with
     | CList_CCons x tl =>
-      if i s= 0%u32
-      then Return x
-      else (i1 <- u32_sub i 1%u32; list_nth T n1 tl i1)
+      if i s= 0%u32 then Ok x else (i1 <- u32_sub i 1%u32; list_nth T n1 tl i1)
     | CList_CNil => Fail_ Failure
     end
   end
@@ -78,17 +76,15 @@ Fixpoint list_nth_mut
     match l with
     | CList_CCons x tl =>
       if i s= 0%u32
-      then
-        let back := fun (ret : T) => Return (CList_CCons ret tl) in
-        Return (x, back)
+      then let back := fun (ret : T) => Ok (CList_CCons ret tl) in Ok (x, back)
       else (
         i1 <- u32_sub i 1%u32;
         p <- list_nth_mut T n1 tl i1;
         let (t, list_nth_mut_back) := p in
         let back :=
-          fun (ret : T) =>
-            tl1 <- list_nth_mut_back ret; Return (CList_CCons x tl1) in
-        Return (t, back))
+          fun (ret : T) => tl1 <- list_nth_mut_back ret; Ok (CList_CCons x tl1)
+          in
+        Ok (t, back))
     | CList_CNil => Fail_ Failure
     end
   end
@@ -106,16 +102,14 @@ Fixpoint list_nth_mut1_loop
     match l with
     | CList_CCons x tl =>
       if i s= 0%u32
-      then
-        let back := fun (ret : T) => Return (CList_CCons ret tl) in
-        Return (x, back)
+      then let back := fun (ret : T) => Ok (CList_CCons ret tl) in Ok (x, back)
       else (
         i1 <- u32_sub i 1%u32;
         p <- list_nth_mut1_loop T n1 tl i1;
         let (t, back) := p in
-        let back1 :=
-          fun (ret : T) => tl1 <- back ret; Return (CList_CCons x tl1) in
-        Return (t, back1))
+        let back1 := fun (ret : T) => tl1 <- back ret; Ok (CList_CCons x tl1)
+          in
+        Ok (t, back1))
     | CList_CNil => Fail_ Failure
     end
   end
@@ -137,7 +131,7 @@ Fixpoint i32_id (n : nat) (i : i32) : result i32 :=
   | O => Fail_ OutOfFuel
   | S n1 =>
     if i s= 0%i32
-    then Return 0%i32
+    then Ok 0%i32
     else (i1 <- i32_sub i 1%i32; i2 <- i32_id n1 i1; i32_add i2 1%i32)
   end
 .
@@ -157,9 +151,9 @@ Fixpoint list_tail
       let (c, list_tail_back) := p in
       let back :=
         fun (ret : CList_t T) =>
-          tl1 <- list_tail_back ret; Return (CList_CCons t tl1) in
-      Return (c, back)
-    | CList_CNil => Return (CList_CNil, Return)
+          tl1 <- list_tail_back ret; Ok (CList_CCons t tl1) in
+      Ok (c, back)
+    | CList_CNil => Ok (CList_CNil, Ok)
     end
   end
 .
@@ -176,7 +170,7 @@ Arguments Counter_t_incr { _ }.
 (** [demo::{(demo::Counter for usize)}::incr]:
     Source: 'src/demo.rs', lines 102:4-102:31 *)
 Definition counterUsize_incr (self : usize) : result (usize * usize) :=
-  self1 <- usize_add self 1%usize; Return (self, self1)
+  self1 <- usize_add self 1%usize; Ok (self, self1)
 .
 
 (** Trait implementation: [demo::{(demo::Counter for usize)}]
diff --git a/tests/coq/demo/Primitives.v b/tests/coq/demo/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/demo/Primitives.v
+++ b/tests/coq/demo/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/hashmap/Hashmap_Funs.v b/tests/coq/hashmap/Hashmap_Funs.v
index c0cde78d..ebb7897d 100644
--- a/tests/coq/hashmap/Hashmap_Funs.v
+++ b/tests/coq/hashmap/Hashmap_Funs.v
@@ -13,7 +13,7 @@ Module Hashmap_Funs.
 (** [hashmap::hash_key]:
     Source: 'src/hashmap.rs', lines 27:0-27:32 *)
 Definition hash_key (k : usize) : result usize :=
-  Return k.
+  Ok k.
 
 (** [hashmap::{hashmap::HashMap<T>}::allocate_slots]: loop 0:
     Source: 'src/hashmap.rs', lines 50:4-56:5 *)
@@ -29,7 +29,7 @@ Fixpoint hashMap_allocate_slots_loop
       slots1 <- alloc_vec_Vec_push (List_t T) slots List_Nil;
       n3 <- usize_sub n1 1%usize;
       hashMap_allocate_slots_loop T n2 slots1 n3)
-    else Return slots
+    else Ok slots
   end
 .
 
@@ -52,7 +52,7 @@ Definition hashMap_new_with_capacity
   slots <- hashMap_allocate_slots T n (alloc_vec_Vec_new (List_t T)) capacity;
   i <- usize_mul capacity max_load_dividend;
   i1 <- usize_div i max_load_divisor;
-  Return
+  Ok
     {|
       hashMap_num_entries := 0%usize;
       hashMap_max_load_factor := (max_load_dividend, max_load_divisor);
@@ -86,7 +86,7 @@ Fixpoint hashMap_clear_loop
       i2 <- usize_add i 1%usize;
       slots1 <- index_mut_back List_Nil;
       hashMap_clear_loop T n1 slots1 i2)
-    else Return slots
+    else Ok slots
   end
 .
 
@@ -95,7 +95,7 @@ Fixpoint hashMap_clear_loop
 Definition hashMap_clear
   (T : Type) (n : nat) (self : HashMap_t T) : result (HashMap_t T) :=
   hm <- hashMap_clear_loop T n self.(hashMap_slots) 0%usize;
-  Return
+  Ok
     {|
       hashMap_num_entries := 0%usize;
       hashMap_max_load_factor := self.(hashMap_max_load_factor);
@@ -107,7 +107,7 @@ Definition hashMap_clear
 (** [hashmap::{hashmap::HashMap<T>}::len]:
     Source: 'src/hashmap.rs', lines 90:4-90:30 *)
 Definition hashMap_len (T : Type) (self : HashMap_t T) : result usize :=
-  Return self.(hashMap_num_entries)
+  Ok self.(hashMap_num_entries)
 .
 
 (** [hashmap::{hashmap::HashMap<T>}::insert_in_list]: loop 0:
@@ -122,12 +122,12 @@ Fixpoint hashMap_insert_in_list_loop
     match ls with
     | List_Cons ckey cvalue tl =>
       if ckey s= key
-      then Return (false, List_Cons ckey value tl)
+      then Ok (false, List_Cons ckey value tl)
       else (
         p <- hashMap_insert_in_list_loop T n1 key value tl;
         let (b, tl1) := p in
-        Return (b, List_Cons ckey cvalue tl1))
-    | List_Nil => Return (true, List_Cons key value List_Nil)
+        Ok (b, List_Cons ckey cvalue tl1))
+    | List_Nil => Ok (true, List_Cons key value List_Nil)
     end
   end
 .
@@ -161,7 +161,7 @@ Definition hashMap_insert_no_resize
   then (
     i1 <- usize_add self.(hashMap_num_entries) 1%usize;
     v <- index_mut_back l1;
-    Return
+    Ok
       {|
         hashMap_num_entries := i1;
         hashMap_max_load_factor := self.(hashMap_max_load_factor);
@@ -170,7 +170,7 @@ Definition hashMap_insert_no_resize
       |})
   else (
     v <- index_mut_back l1;
-    Return
+    Ok
       {|
         hashMap_num_entries := self.(hashMap_num_entries);
         hashMap_max_load_factor := self.(hashMap_max_load_factor);
@@ -192,7 +192,7 @@ Fixpoint hashMap_move_elements_from_list_loop
     | List_Cons k v tl =>
       ntable1 <- hashMap_insert_no_resize T n1 ntable k v;
       hashMap_move_elements_from_list_loop T n1 ntable1 tl
-    | List_Nil => Return ntable
+    | List_Nil => Ok ntable
     end
   end
 .
@@ -228,7 +228,7 @@ Fixpoint hashMap_move_elements_loop
       i2 <- usize_add i 1%usize;
       slots1 <- index_mut_back l1;
       hashMap_move_elements_loop T n1 ntable1 slots1 i2)
-    else Return (ntable, slots)
+    else Ok (ntable, slots)
   end
 .
 
@@ -257,7 +257,7 @@ Definition hashMap_try_resize
     ntable <- hashMap_new_with_capacity T n i3 i i1;
     p <- hashMap_move_elements T n ntable self.(hashMap_slots) 0%usize;
     let (ntable1, _) := p in
-    Return
+    Ok
       {|
         hashMap_num_entries := self.(hashMap_num_entries);
         hashMap_max_load_factor := (i, i1);
@@ -265,7 +265,7 @@ Definition hashMap_try_resize
         hashMap_slots := ntable1.(hashMap_slots)
       |})
   else
-    Return
+    Ok
       {|
         hashMap_num_entries := self.(hashMap_num_entries);
         hashMap_max_load_factor := (i, i1);
@@ -284,7 +284,7 @@ Definition hashMap_insert
   i <- hashMap_len T self1;
   if i s> self1.(hashMap_max_load)
   then hashMap_try_resize T n self1
-  else Return self1
+  else Ok self1
 .
 
 (** [hashmap::{hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
@@ -297,9 +297,9 @@ Fixpoint hashMap_contains_key_in_list_loop
     match ls with
     | List_Cons ckey _ tl =>
       if ckey s= key
-      then Return true
+      then Ok true
       else hashMap_contains_key_in_list_loop T n1 key tl
-    | List_Nil => Return false
+    | List_Nil => Ok false
     end
   end
 .
@@ -334,9 +334,7 @@ Fixpoint hashMap_get_in_list_loop
   | S n1 =>
     match ls with
     | List_Cons ckey cvalue tl =>
-      if ckey s= key
-      then Return cvalue
-      else hashMap_get_in_list_loop T n1 key tl
+      if ckey s= key then Ok cvalue else hashMap_get_in_list_loop T n1 key tl
     | List_Nil => Fail_ Failure
     end
   end
@@ -376,15 +374,14 @@ Fixpoint hashMap_get_mut_in_list_loop
     | List_Cons ckey cvalue tl =>
       if ckey s= key
       then
-        let back := fun (ret : T) => Return (List_Cons ckey ret tl) in
-        Return (cvalue, back)
+        let back := fun (ret : T) => Ok (List_Cons ckey ret tl) in
+        Ok (cvalue, back)
       else (
         p <- hashMap_get_mut_in_list_loop T n1 tl key;
         let (t, back) := p in
         let back1 :=
-          fun (ret : T) => tl1 <- back ret; Return (List_Cons ckey cvalue tl1)
-          in
-        Return (t, back1))
+          fun (ret : T) => tl1 <- back ret; Ok (List_Cons ckey cvalue tl1) in
+        Ok (t, back1))
     | List_Nil => Fail_ Failure
     end
   end
@@ -419,14 +416,14 @@ Definition hashMap_get_mut
     fun (ret : T) =>
       l1 <- get_mut_in_list_back ret;
       v <- index_mut_back l1;
-      Return
+      Ok
         {|
           hashMap_num_entries := self.(hashMap_num_entries);
           hashMap_max_load_factor := self.(hashMap_max_load_factor);
           hashMap_max_load := self.(hashMap_max_load);
           hashMap_slots := v
         |} in
-  Return (t, back)
+  Ok (t, back)
 .
 
 (** [hashmap::{hashmap::HashMap<T>}::remove_from_list]: loop 0:
@@ -445,14 +442,14 @@ Fixpoint hashMap_remove_from_list_loop
         let (mv_ls, _) :=
           core_mem_replace (List_t T) (List_Cons ckey t tl) List_Nil in
         match mv_ls with
-        | List_Cons _ cvalue tl1 => Return (Some cvalue, tl1)
+        | List_Cons _ cvalue tl1 => Ok (Some cvalue, tl1)
         | List_Nil => Fail_ Failure
         end
       else (
         p <- hashMap_remove_from_list_loop T n1 key tl;
         let (o, tl1) := p in
-        Return (o, List_Cons ckey t tl1))
-    | List_Nil => Return (None, List_Nil)
+        Ok (o, List_Cons ckey t tl1))
+    | List_Nil => Ok (None, List_Nil)
     end
   end
 .
@@ -485,7 +482,7 @@ Definition hashMap_remove
   match x with
   | None =>
     v <- index_mut_back l1;
-    Return (None,
+    Ok (None,
       {|
         hashMap_num_entries := self.(hashMap_num_entries);
         hashMap_max_load_factor := self.(hashMap_max_load_factor);
@@ -495,7 +492,7 @@ Definition hashMap_remove
   | Some x1 =>
     i1 <- usize_sub self.(hashMap_num_entries) 1%usize;
     v <- index_mut_back l1;
-    Return (Some x1,
+    Ok (Some x1,
       {|
         hashMap_num_entries := i1;
         hashMap_max_load_factor := self.(hashMap_max_load_factor);
@@ -541,7 +538,7 @@ Definition test1 (n : nat) : result unit :=
             then Fail_ Failure
             else (
               i4 <- hashMap_get u64 n hm6 1056%usize;
-              if negb (i4 s= 256%u64) then Fail_ Failure else Return tt)))
+              if negb (i4 s= 256%u64) then Fail_ Failure else Ok tt)))
       end))
 .
 
diff --git a/tests/coq/hashmap/Primitives.v b/tests/coq/hashmap/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/hashmap/Primitives.v
+++ b/tests/coq/hashmap/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/hashmap_on_disk/HashmapMain_Funs.v b/tests/coq/hashmap_on_disk/HashmapMain_Funs.v
index 8e299800..79da6e80 100644
--- a/tests/coq/hashmap_on_disk/HashmapMain_Funs.v
+++ b/tests/coq/hashmap_on_disk/HashmapMain_Funs.v
@@ -15,7 +15,7 @@ Module HashmapMain_Funs.
 (** [hashmap_main::hashmap::hash_key]:
     Source: 'src/hashmap.rs', lines 27:0-27:32 *)
 Definition hashmap_hash_key (k : usize) : result usize :=
-  Return k.
+  Ok k.
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::allocate_slots]: loop 0:
     Source: 'src/hashmap.rs', lines 50:4-56:5 *)
@@ -32,7 +32,7 @@ Fixpoint hashmap_HashMap_allocate_slots_loop
       slots1 <- alloc_vec_Vec_push (hashmap_List_t T) slots Hashmap_List_Nil;
       n3 <- usize_sub n1 1%usize;
       hashmap_HashMap_allocate_slots_loop T n2 slots1 n3)
-    else Return slots
+    else Ok slots
   end
 .
 
@@ -58,7 +58,7 @@ Definition hashmap_HashMap_new_with_capacity
       capacity;
   i <- usize_mul capacity max_load_dividend;
   i1 <- usize_div i max_load_divisor;
-  Return
+  Ok
     {|
       hashmap_HashMap_num_entries := 0%usize;
       hashmap_HashMap_max_load_factor := (max_load_dividend, max_load_divisor);
@@ -94,7 +94,7 @@ Fixpoint hashmap_HashMap_clear_loop
       i2 <- usize_add i 1%usize;
       slots1 <- index_mut_back Hashmap_List_Nil;
       hashmap_HashMap_clear_loop T n1 slots1 i2)
-    else Return slots
+    else Ok slots
   end
 .
 
@@ -105,7 +105,7 @@ Definition hashmap_HashMap_clear
   result (hashmap_HashMap_t T)
   :=
   hm <- hashmap_HashMap_clear_loop T n self.(hashmap_HashMap_slots) 0%usize;
-  Return
+  Ok
     {|
       hashmap_HashMap_num_entries := 0%usize;
       hashmap_HashMap_max_load_factor := self.(hashmap_HashMap_max_load_factor);
@@ -118,7 +118,7 @@ Definition hashmap_HashMap_clear
     Source: 'src/hashmap.rs', lines 90:4-90:30 *)
 Definition hashmap_HashMap_len
   (T : Type) (self : hashmap_HashMap_t T) : result usize :=
-  Return self.(hashmap_HashMap_num_entries)
+  Ok self.(hashmap_HashMap_num_entries)
 .
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert_in_list]: loop 0:
@@ -133,13 +133,13 @@ Fixpoint hashmap_HashMap_insert_in_list_loop
     match ls with
     | Hashmap_List_Cons ckey cvalue tl =>
       if ckey s= key
-      then Return (false, Hashmap_List_Cons ckey value tl)
+      then Ok (false, Hashmap_List_Cons ckey value tl)
       else (
         p <- hashmap_HashMap_insert_in_list_loop T n1 key value tl;
         let (b, tl1) := p in
-        Return (b, Hashmap_List_Cons ckey cvalue tl1))
+        Ok (b, Hashmap_List_Cons ckey cvalue tl1))
     | Hashmap_List_Nil =>
-      Return (true, Hashmap_List_Cons key value Hashmap_List_Nil)
+      Ok (true, Hashmap_List_Cons key value Hashmap_List_Nil)
     end
   end
 .
@@ -173,7 +173,7 @@ Definition hashmap_HashMap_insert_no_resize
   then (
     i1 <- usize_add self.(hashmap_HashMap_num_entries) 1%usize;
     v <- index_mut_back l1;
-    Return
+    Ok
       {|
         hashmap_HashMap_num_entries := i1;
         hashmap_HashMap_max_load_factor :=
@@ -183,7 +183,7 @@ Definition hashmap_HashMap_insert_no_resize
       |})
   else (
     v <- index_mut_back l1;
-    Return
+    Ok
       {|
         hashmap_HashMap_num_entries := self.(hashmap_HashMap_num_entries);
         hashmap_HashMap_max_load_factor :=
@@ -206,7 +206,7 @@ Fixpoint hashmap_HashMap_move_elements_from_list_loop
     | Hashmap_List_Cons k v tl =>
       ntable1 <- hashmap_HashMap_insert_no_resize T n1 ntable k v;
       hashmap_HashMap_move_elements_from_list_loop T n1 ntable1 tl
-    | Hashmap_List_Nil => Return ntable
+    | Hashmap_List_Nil => Ok ntable
     end
   end
 .
@@ -243,7 +243,7 @@ Fixpoint hashmap_HashMap_move_elements_loop
       i2 <- usize_add i 1%usize;
       slots1 <- index_mut_back l1;
       hashmap_HashMap_move_elements_loop T n1 ntable1 slots1 i2)
-    else Return (ntable, slots)
+    else Ok (ntable, slots)
   end
 .
 
@@ -277,7 +277,7 @@ Definition hashmap_HashMap_try_resize
       hashmap_HashMap_move_elements T n ntable self.(hashmap_HashMap_slots)
         0%usize;
     let (ntable1, _) := p in
-    Return
+    Ok
       {|
         hashmap_HashMap_num_entries := self.(hashmap_HashMap_num_entries);
         hashmap_HashMap_max_load_factor := (i, i1);
@@ -285,7 +285,7 @@ Definition hashmap_HashMap_try_resize
         hashmap_HashMap_slots := ntable1.(hashmap_HashMap_slots)
       |})
   else
-    Return
+    Ok
       {|
         hashmap_HashMap_num_entries := self.(hashmap_HashMap_num_entries);
         hashmap_HashMap_max_load_factor := (i, i1);
@@ -304,7 +304,7 @@ Definition hashmap_HashMap_insert
   i <- hashmap_HashMap_len T self1;
   if i s> self1.(hashmap_HashMap_max_load)
   then hashmap_HashMap_try_resize T n self1
-  else Return self1
+  else Ok self1
 .
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
@@ -317,9 +317,9 @@ Fixpoint hashmap_HashMap_contains_key_in_list_loop
     match ls with
     | Hashmap_List_Cons ckey _ tl =>
       if ckey s= key
-      then Return true
+      then Ok true
       else hashmap_HashMap_contains_key_in_list_loop T n1 key tl
-    | Hashmap_List_Nil => Return false
+    | Hashmap_List_Nil => Ok false
     end
   end
 .
@@ -357,7 +357,7 @@ Fixpoint hashmap_HashMap_get_in_list_loop
     match ls with
     | Hashmap_List_Cons ckey cvalue tl =>
       if ckey s= key
-      then Return cvalue
+      then Ok cvalue
       else hashmap_HashMap_get_in_list_loop T n1 key tl
     | Hashmap_List_Nil => Fail_ Failure
     end
@@ -398,15 +398,15 @@ Fixpoint hashmap_HashMap_get_mut_in_list_loop
     | Hashmap_List_Cons ckey cvalue tl =>
       if ckey s= key
       then
-        let back := fun (ret : T) => Return (Hashmap_List_Cons ckey ret tl) in
-        Return (cvalue, back)
+        let back := fun (ret : T) => Ok (Hashmap_List_Cons ckey ret tl) in
+        Ok (cvalue, back)
       else (
         p <- hashmap_HashMap_get_mut_in_list_loop T n1 tl key;
         let (t, back) := p in
         let back1 :=
           fun (ret : T) =>
-            tl1 <- back ret; Return (Hashmap_List_Cons ckey cvalue tl1) in
-        Return (t, back1))
+            tl1 <- back ret; Ok (Hashmap_List_Cons ckey cvalue tl1) in
+        Ok (t, back1))
     | Hashmap_List_Nil => Fail_ Failure
     end
   end
@@ -441,7 +441,7 @@ Definition hashmap_HashMap_get_mut
     fun (ret : T) =>
       l1 <- get_mut_in_list_back ret;
       v <- index_mut_back l1;
-      Return
+      Ok
         {|
           hashmap_HashMap_num_entries := self.(hashmap_HashMap_num_entries);
           hashmap_HashMap_max_load_factor :=
@@ -449,7 +449,7 @@ Definition hashmap_HashMap_get_mut
           hashmap_HashMap_max_load := self.(hashmap_HashMap_max_load);
           hashmap_HashMap_slots := v
         |} in
-  Return (t, back)
+  Ok (t, back)
 .
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::remove_from_list]: loop 0:
@@ -469,14 +469,14 @@ Fixpoint hashmap_HashMap_remove_from_list_loop
           core_mem_replace (hashmap_List_t T) (Hashmap_List_Cons ckey t tl)
             Hashmap_List_Nil in
         match mv_ls with
-        | Hashmap_List_Cons _ cvalue tl1 => Return (Some cvalue, tl1)
+        | Hashmap_List_Cons _ cvalue tl1 => Ok (Some cvalue, tl1)
         | Hashmap_List_Nil => Fail_ Failure
         end
       else (
         p <- hashmap_HashMap_remove_from_list_loop T n1 key tl;
         let (o, tl1) := p in
-        Return (o, Hashmap_List_Cons ckey t tl1))
-    | Hashmap_List_Nil => Return (None, Hashmap_List_Nil)
+        Ok (o, Hashmap_List_Cons ckey t tl1))
+    | Hashmap_List_Nil => Ok (None, Hashmap_List_Nil)
     end
   end
 .
@@ -509,7 +509,7 @@ Definition hashmap_HashMap_remove
   match x with
   | None =>
     v <- index_mut_back l1;
-    Return (None,
+    Ok (None,
       {|
         hashmap_HashMap_num_entries := self.(hashmap_HashMap_num_entries);
         hashmap_HashMap_max_load_factor :=
@@ -520,7 +520,7 @@ Definition hashmap_HashMap_remove
   | Some x1 =>
     i1 <- usize_sub self.(hashmap_HashMap_num_entries) 1%usize;
     v <- index_mut_back l1;
-    Return (Some x1,
+    Ok (Some x1,
       {|
         hashmap_HashMap_num_entries := i1;
         hashmap_HashMap_max_load_factor :=
@@ -567,7 +567,7 @@ Definition hashmap_test1 (n : nat) : result unit :=
             then Fail_ Failure
             else (
               i4 <- hashmap_HashMap_get u64 n hm6 1056%usize;
-              if negb (i4 s= 256%u64) then Fail_ Failure else Return tt)))
+              if negb (i4 s= 256%u64) then Fail_ Failure else Ok tt)))
       end))
 .
 
@@ -584,6 +584,6 @@ Definition insert_on_disk
 (** [hashmap_main::main]:
     Source: 'src/hashmap_main.rs', lines 16:0-16:13 *)
 Definition main : result unit :=
-  Return tt.
+  Ok tt.
 
 End HashmapMain_Funs.
diff --git a/tests/coq/hashmap_on_disk/Primitives.v b/tests/coq/hashmap_on_disk/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/hashmap_on_disk/Primitives.v
+++ b/tests/coq/hashmap_on_disk/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/misc/Bitwise.v b/tests/coq/misc/Bitwise.v
index b04c95f2..b2339c58 100644
--- a/tests/coq/misc/Bitwise.v
+++ b/tests/coq/misc/Bitwise.v
@@ -23,16 +23,16 @@ Definition shift_i32 (a : i32) : result i32 :=
 (** [bitwise::xor_u32]:
     Source: 'src/bitwise.rs', lines 17:0-17:37 *)
 Definition xor_u32 (a : u32) (b : u32) : result u32 :=
-  Return (u32_xor a b).
+  Ok (u32_xor a b).
 
 (** [bitwise::or_u32]:
     Source: 'src/bitwise.rs', lines 21:0-21:36 *)
 Definition or_u32 (a : u32) (b : u32) : result u32 :=
-  Return (u32_or a b).
+  Ok (u32_or a b).
 
 (** [bitwise::and_u32]:
     Source: 'src/bitwise.rs', lines 25:0-25:37 *)
 Definition and_u32 (a : u32) (b : u32) : result u32 :=
-  Return (u32_and a b).
+  Ok (u32_and a b).
 
 End Bitwise.
diff --git a/tests/coq/misc/Constants.v b/tests/coq/misc/Constants.v
index fcafed53..71185975 100644
--- a/tests/coq/misc/Constants.v
+++ b/tests/coq/misc/Constants.v
@@ -10,17 +10,17 @@ Module Constants.
 
 (** [constants::X0]
     Source: 'src/constants.rs', lines 5:0-5:17 *)
-Definition x0_body : result u32 := Return 0%u32.
+Definition x0_body : result u32 := Ok 0%u32.
 Definition x0 : u32 := x0_body%global.
 
 (** [constants::X1]
     Source: 'src/constants.rs', lines 7:0-7:17 *)
-Definition x1_body : result u32 := Return core_u32_max.
+Definition x1_body : result u32 := Ok core_u32_max.
 Definition x1 : u32 := x1_body%global.
 
 (** [constants::X2]
     Source: 'src/constants.rs', lines 10:0-10:17 *)
-Definition x2_body : result u32 := Return 3%u32.
+Definition x2_body : result u32 := Ok 3%u32.
 Definition x2 : u32 := x2_body%global.
 
 (** [constants::incr]:
@@ -36,8 +36,7 @@ Definition x3 : u32 := x3_body%global.
 (** [constants::mk_pair0]:
     Source: 'src/constants.rs', lines 23:0-23:51 *)
 Definition mk_pair0 (x : u32) (y1 : u32) : result (u32 * u32) :=
-  Return (x, y1)
-.
+  Ok (x, y1).
 
 (** [constants::Pair]
     Source: 'src/constants.rs', lines 36:0-36:23 *)
@@ -50,7 +49,7 @@ Arguments pair_y { _ _ }.
 (** [constants::mk_pair1]:
     Source: 'src/constants.rs', lines 27:0-27:55 *)
 Definition mk_pair1 (x : u32) (y1 : u32) : result (Pair_t u32 u32) :=
-  Return {| pair_x := x; pair_y := y1 |}
+  Ok {| pair_x := x; pair_y := y1 |}
 .
 
 (** [constants::P0]
@@ -65,13 +64,13 @@ Definition p1 : Pair_t u32 u32 := p1_body%global.
 
 (** [constants::P2]
     Source: 'src/constants.rs', lines 33:0-33:24 *)
-Definition p2_body : result (u32 * u32) := Return (0%u32, 1%u32).
+Definition p2_body : result (u32 * u32) := Ok (0%u32, 1%u32).
 Definition p2 : (u32 * u32) := p2_body%global.
 
 (** [constants::P3]
     Source: 'src/constants.rs', lines 34:0-34:28 *)
 Definition p3_body : result (Pair_t u32 u32) :=
-  Return {| pair_x := 0%u32; pair_y := 1%u32 |}
+  Ok {| pair_x := 0%u32; pair_y := 1%u32 |}
 .
 Definition p3 : Pair_t u32 u32 := p3_body%global.
 
@@ -85,7 +84,7 @@ Arguments wrap_value { _ }.
 (** [constants::{constants::Wrap<T>}::new]:
     Source: 'src/constants.rs', lines 54:4-54:41 *)
 Definition wrap_new (T : Type) (value : T) : result (Wrap_t T) :=
-  Return {| wrap_value := value |}
+  Ok {| wrap_value := value |}
 .
 
 (** [constants::Y]
@@ -96,7 +95,7 @@ Definition y : Wrap_t i32 := y_body%global.
 (** [constants::unwrap_y]:
     Source: 'src/constants.rs', lines 43:0-43:30 *)
 Definition unwrap_y : result i32 :=
-  Return y.(wrap_value).
+  Ok y.(wrap_value).
 
 (** [constants::YVAL]
     Source: 'src/constants.rs', lines 47:0-47:19 *)
@@ -105,13 +104,13 @@ Definition yval : i32 := yval_body%global.
 
 (** [constants::get_z1::Z1]
     Source: 'src/constants.rs', lines 62:4-62:17 *)
-Definition get_z1_z1_body : result i32 := Return 3%i32.
+Definition get_z1_z1_body : result i32 := Ok 3%i32.
 Definition get_z1_z1 : i32 := get_z1_z1_body%global.
 
 (** [constants::get_z1]:
     Source: 'src/constants.rs', lines 61:0-61:28 *)
 Definition get_z1 : result i32 :=
-  Return get_z1_z1.
+  Ok get_z1_z1.
 
 (** [constants::add]:
     Source: 'src/constants.rs', lines 66:0-66:39 *)
@@ -120,12 +119,12 @@ Definition add (a : i32) (b : i32) : result i32 :=
 
 (** [constants::Q1]
     Source: 'src/constants.rs', lines 74:0-74:17 *)
-Definition q1_body : result i32 := Return 5%i32.
+Definition q1_body : result i32 := Ok 5%i32.
 Definition q1 : i32 := q1_body%global.
 
 (** [constants::Q2]
     Source: 'src/constants.rs', lines 75:0-75:17 *)
-Definition q2_body : result i32 := Return q1.
+Definition q2_body : result i32 := Ok q1.
 Definition q2 : i32 := q2_body%global.
 
 (** [constants::Q3]
@@ -140,7 +139,7 @@ Definition get_z2 : result i32 :=
 
 (** [constants::S1]
     Source: 'src/constants.rs', lines 80:0-80:18 *)
-Definition s1_body : result u32 := Return 6%u32.
+Definition s1_body : result u32 := Ok 6%u32.
 Definition s1 : u32 := s1_body%global.
 
 (** [constants::S2]
@@ -150,7 +149,7 @@ Definition s2 : u32 := s2_body%global.
 
 (** [constants::S3]
     Source: 'src/constants.rs', lines 82:0-82:29 *)
-Definition s3_body : result (Pair_t u32 u32) := Return p3.
+Definition s3_body : result (Pair_t u32 u32) := Ok p3.
 Definition s3 : Pair_t u32 u32 := s3_body%global.
 
 (** [constants::S4]
@@ -167,12 +166,12 @@ Arguments v_x { _ _ }.
 
 (** [constants::{constants::V<T, N>#1}::LEN]
     Source: 'src/constants.rs', lines 91:4-91:24 *)
-Definition v_len_body (T : Type) (N : usize) : result usize := Return N.
+Definition v_len_body (T : Type) (N : usize) : result usize := Ok N.
 Definition v_len (T : Type) (N : usize) : usize := (v_len_body T N)%global.
 
 (** [constants::use_v]:
     Source: 'src/constants.rs', lines 94:0-94:42 *)
 Definition use_v (T : Type) (N : usize) : result usize :=
-  Return (v_len T N).
+  Ok (v_len T N).
 
 End Constants.
diff --git a/tests/coq/misc/External_Funs.v b/tests/coq/misc/External_Funs.v
index a6832854..41d4a7bd 100644
--- a/tests/coq/misc/External_Funs.v
+++ b/tests/coq/misc/External_Funs.v
@@ -31,7 +31,7 @@ Definition test_new_non_zero_u32
 (** [external::test_vec]:
     Source: 'src/external.rs', lines 17:0-17:17 *)
 Definition test_vec : result unit :=
-  _ <- alloc_vec_Vec_push u32 (alloc_vec_Vec_new u32) 0%u32; Return tt
+  _ <- alloc_vec_Vec_push u32 (alloc_vec_Vec_new u32) 0%u32; Ok tt
 .
 
 (** Unit test for [external::test_vec] *)
@@ -46,8 +46,8 @@ Definition custom_swap
   p <- core_mem_swap T x y st;
   let (st1, p1) := p in
   let (x1, y1) := p1 in
-  let back := fun (ret : T) (st2 : state) => Return (st2, (ret, y1)) in
-  Return (st1, (x1, back))
+  let back := fun (ret : T) (st2 : state) => Ok (st2, (ret, y1)) in
+  Ok (st1, (x1, back))
 .
 
 (** [external::test_custom_swap]:
@@ -60,7 +60,7 @@ Definition test_custom_swap
   p2 <- custom_swap_back 1%u32 st1;
   let (_, p3) := p2 in
   let (x1, y1) := p3 in
-  Return (st1, (x1, y1))
+  Ok (st1, (x1, y1))
 .
 
 (** [external::test_swap_non_zero]:
@@ -69,7 +69,7 @@ Definition test_swap_non_zero (x : u32) (st : state) : result (state * u32) :=
   p <- swap u32 x 0%u32 st;
   let (st1, p1) := p in
   let (x1, _) := p1 in
-  if x1 s= 0%u32 then Fail_ Failure else Return (st1, x1)
+  if x1 s= 0%u32 then Fail_ Failure else Ok (st1, x1)
 .
 
 End External_Funs.
diff --git a/tests/coq/misc/External_FunsExternal.v b/tests/coq/misc/External_FunsExternal.v
index e9655f57..130b48a2 100644
--- a/tests/coq/misc/External_FunsExternal.v
+++ b/tests/coq/misc/External_FunsExternal.v
@@ -13,7 +13,7 @@ Module External_FunsExternal.
 (** [core::mem::swap]:
     Source: '/rustc/d59363ad0b6391b7fc5bbb02c9ccf9300eef3753/library/core/src/mem/mod.rs', lines 726:0-726:42 *)
 Definition core_mem_swap (T : Type) (x : T) (y : T) (s : state) :=
-  Return (s, (y, x))
+  Ok (s, (y, x))
 .
 
 (** [core::num::nonzero::{core::num::nonzero::NonZeroU32#14}::new]: forward function
diff --git a/tests/coq/misc/Loops.v b/tests/coq/misc/Loops.v
index ae529cf8..f396f16f 100644
--- a/tests/coq/misc/Loops.v
+++ b/tests/coq/misc/Loops.v
@@ -83,7 +83,7 @@ Fixpoint sum_array_loop
       s1 <- u32_add s i1;
       i2 <- usize_add i 1%usize;
       sum_array_loop N n1 a i2 s1)
-    else Return s
+    else Ok s
   end
 .
 
@@ -110,7 +110,7 @@ Fixpoint clear_loop
       i2 <- usize_add i 1%usize;
       v1 <- index_mut_back 0%u32;
       clear_loop n1 v1 i2)
-    else Return v
+    else Ok v
   end
 .
 
@@ -138,8 +138,8 @@ Fixpoint list_mem_loop (n : nat) (x : u32) (ls : List_t u32) : result bool :=
   | O => Fail_ OutOfFuel
   | S n1 =>
     match ls with
-    | List_Cons y tl => if y s= x then Return true else list_mem_loop n1 x tl
-    | List_Nil => Return false
+    | List_Cons y tl => if y s= x then Ok true else list_mem_loop n1 x tl
+    | List_Nil => Ok false
     end
   end
 .
@@ -162,16 +162,13 @@ Fixpoint list_nth_mut_loop_loop
     match ls with
     | List_Cons x tl =>
       if i s= 0%u32
-      then
-        let back := fun (ret : T) => Return (List_Cons ret tl) in
-        Return (x, back)
+      then let back := fun (ret : T) => Ok (List_Cons ret tl) in Ok (x, back)
       else (
         i1 <- u32_sub i 1%u32;
         p <- list_nth_mut_loop_loop T n1 tl i1;
         let (t, back) := p in
-        let back1 := fun (ret : T) => tl1 <- back ret; Return (List_Cons x tl1)
-          in
-        Return (t, back1))
+        let back1 := fun (ret : T) => tl1 <- back ret; Ok (List_Cons x tl1) in
+        Ok (t, back1))
     | List_Nil => Fail_ Failure
     end
   end
@@ -196,7 +193,7 @@ Fixpoint list_nth_shared_loop_loop
     match ls with
     | List_Cons x tl =>
       if i s= 0%u32
-      then Return x
+      then Ok x
       else (i1 <- u32_sub i 1%u32; list_nth_shared_loop_loop T n1 tl i1)
     | List_Nil => Fail_ Failure
     end
@@ -223,14 +220,13 @@ Fixpoint get_elem_mut_loop
     | List_Cons y tl =>
       if y s= x
       then
-        let back := fun (ret : usize) => Return (List_Cons ret tl) in
-        Return (y, back)
+        let back := fun (ret : usize) => Ok (List_Cons ret tl) in Ok (y, back)
       else (
         p <- get_elem_mut_loop n1 x tl;
         let (i, back) := p in
-        let back1 :=
-          fun (ret : usize) => tl1 <- back ret; Return (List_Cons y tl1) in
-        Return (i, back1))
+        let back1 := fun (ret : usize) => tl1 <- back ret; Ok (List_Cons y tl1)
+          in
+        Ok (i, back1))
     | List_Nil => Fail_ Failure
     end
   end
@@ -249,7 +245,7 @@ Definition get_elem_mut
   p1 <- get_elem_mut_loop n x ls;
   let (i, back) := p1 in
   let back1 := fun (ret : usize) => l <- back ret; index_mut_back l in
-  Return (i, back1)
+  Ok (i, back1)
 .
 
 (** [loops::get_elem_shared]: loop 0:
@@ -260,8 +256,7 @@ Fixpoint get_elem_shared_loop
   | O => Fail_ OutOfFuel
   | S n1 =>
     match ls with
-    | List_Cons y tl =>
-      if y s= x then Return y else get_elem_shared_loop n1 x tl
+    | List_Cons y tl => if y s= x then Ok y else get_elem_shared_loop n1 x tl
     | List_Nil => Fail_ Failure
     end
   end
@@ -285,14 +280,13 @@ Definition id_mut
   (T : Type) (ls : List_t T) :
   result ((List_t T) * (List_t T -> result (List_t T)))
   :=
-  Return (ls, Return)
+  Ok (ls, Ok)
 .
 
 (** [loops::id_shared]:
     Source: 'src/loops.rs', lines 149:0-149:45 *)
 Definition id_shared (T : Type) (ls : List_t T) : result (List_t T) :=
-  Return ls
-.
+  Ok ls.
 
 (** [loops::list_nth_mut_loop_with_id]: loop 0:
     Source: 'src/loops.rs', lines 154:0-165:1 *)
@@ -306,16 +300,13 @@ Fixpoint list_nth_mut_loop_with_id_loop
     match ls with
     | List_Cons x tl =>
       if i s= 0%u32
-      then
-        let back := fun (ret : T) => Return (List_Cons ret tl) in
-        Return (x, back)
+      then let back := fun (ret : T) => Ok (List_Cons ret tl) in Ok (x, back)
       else (
         i1 <- u32_sub i 1%u32;
         p <- list_nth_mut_loop_with_id_loop T n1 i1 tl;
         let (t, back) := p in
-        let back1 := fun (ret : T) => tl1 <- back ret; Return (List_Cons x tl1)
-          in
-        Return (t, back1))
+        let back1 := fun (ret : T) => tl1 <- back ret; Ok (List_Cons x tl1) in
+        Ok (t, back1))
     | List_Nil => Fail_ Failure
     end
   end
@@ -332,7 +323,7 @@ Definition list_nth_mut_loop_with_id
   p1 <- list_nth_mut_loop_with_id_loop T n i ls1;
   let (t, back) := p1 in
   let back1 := fun (ret : T) => l <- back ret; id_mut_back l in
-  Return (t, back1)
+  Ok (t, back1)
 .
 
 (** [loops::list_nth_shared_loop_with_id]: loop 0:
@@ -345,7 +336,7 @@ Fixpoint list_nth_shared_loop_with_id_loop
     match ls with
     | List_Cons x tl =>
       if i s= 0%u32
-      then Return x
+      then Ok x
       else (
         i1 <- u32_sub i 1%u32; list_nth_shared_loop_with_id_loop T n1 i1 tl)
     | List_Nil => Fail_ Failure
@@ -375,18 +366,18 @@ Fixpoint list_nth_mut_loop_pair_loop
       | List_Cons x1 tl1 =>
         if i s= 0%u32
         then
-          let back'a := fun (ret : T) => Return (List_Cons ret tl0) in
-          let back'b := fun (ret : T) => Return (List_Cons ret tl1) in
-          Return ((x0, x1), back'a, back'b)
+          let back'a := fun (ret : T) => Ok (List_Cons ret tl0) in
+          let back'b := fun (ret : T) => Ok (List_Cons ret tl1) in
+          Ok ((x0, x1), back'a, back'b)
         else (
           i1 <- u32_sub i 1%u32;
           t <- list_nth_mut_loop_pair_loop T n1 tl0 tl1 i1;
           let '(p, back'a, back'b) := t in
           let back'a1 :=
-            fun (ret : T) => tl01 <- back'a ret; Return (List_Cons x0 tl01) in
+            fun (ret : T) => tl01 <- back'a ret; Ok (List_Cons x0 tl01) in
           let back'b1 :=
-            fun (ret : T) => tl11 <- back'b ret; Return (List_Cons x1 tl11) in
-          Return (p, back'a1, back'b1))
+            fun (ret : T) => tl11 <- back'b ret; Ok (List_Cons x1 tl11) in
+          Ok (p, back'a1, back'b1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -417,7 +408,7 @@ Fixpoint list_nth_shared_loop_pair_loop
       match ls1 with
       | List_Cons x1 tl1 =>
         if i s= 0%u32
-        then Return (x0, x1)
+        then Ok (x0, x1)
         else (
           i1 <- u32_sub i 1%u32; list_nth_shared_loop_pair_loop T n1 tl0 tl1 i1)
       | List_Nil => Fail_ Failure
@@ -453,9 +444,8 @@ Fixpoint list_nth_mut_loop_pair_merge_loop
         then
           let back :=
             fun (ret : (T * T)) =>
-              let (t, t1) := ret in Return (List_Cons t tl0, List_Cons t1 tl1)
-            in
-          Return ((x0, x1), back)
+              let (t, t1) := ret in Ok (List_Cons t tl0, List_Cons t1 tl1) in
+          Ok ((x0, x1), back)
         else (
           i1 <- u32_sub i 1%u32;
           p <- list_nth_mut_loop_pair_merge_loop T n1 tl0 tl1 i1;
@@ -464,8 +454,8 @@ Fixpoint list_nth_mut_loop_pair_merge_loop
             fun (ret : (T * T)) =>
               p2 <- back ret;
               let (tl01, tl11) := p2 in
-              Return (List_Cons x0 tl01, List_Cons x1 tl11) in
-          Return (p1, back1))
+              Ok (List_Cons x0 tl01, List_Cons x1 tl11) in
+          Ok (p1, back1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -496,7 +486,7 @@ Fixpoint list_nth_shared_loop_pair_merge_loop
       match ls1 with
       | List_Cons x1 tl1 =>
         if i s= 0%u32
-        then Return (x0, x1)
+        then Ok (x0, x1)
         else (
           i1 <- u32_sub i 1%u32;
           list_nth_shared_loop_pair_merge_loop T n1 tl0 tl1 i1)
@@ -531,15 +521,15 @@ Fixpoint list_nth_mut_shared_loop_pair_loop
       | List_Cons x1 tl1 =>
         if i s= 0%u32
         then
-          let back := fun (ret : T) => Return (List_Cons ret tl0) in
-          Return ((x0, x1), back)
+          let back := fun (ret : T) => Ok (List_Cons ret tl0) in
+          Ok ((x0, x1), back)
         else (
           i1 <- u32_sub i 1%u32;
           p <- list_nth_mut_shared_loop_pair_loop T n1 tl0 tl1 i1;
           let (p1, back) := p in
           let back1 :=
-            fun (ret : T) => tl01 <- back ret; Return (List_Cons x0 tl01) in
-          Return (p1, back1))
+            fun (ret : T) => tl01 <- back ret; Ok (List_Cons x0 tl01) in
+          Ok (p1, back1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -571,15 +561,15 @@ Fixpoint list_nth_mut_shared_loop_pair_merge_loop
       | List_Cons x1 tl1 =>
         if i s= 0%u32
         then
-          let back := fun (ret : T) => Return (List_Cons ret tl0) in
-          Return ((x0, x1), back)
+          let back := fun (ret : T) => Ok (List_Cons ret tl0) in
+          Ok ((x0, x1), back)
         else (
           i1 <- u32_sub i 1%u32;
           p <- list_nth_mut_shared_loop_pair_merge_loop T n1 tl0 tl1 i1;
           let (p1, back) := p in
           let back1 :=
-            fun (ret : T) => tl01 <- back ret; Return (List_Cons x0 tl01) in
-          Return (p1, back1))
+            fun (ret : T) => tl01 <- back ret; Ok (List_Cons x0 tl01) in
+          Ok (p1, back1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -611,15 +601,15 @@ Fixpoint list_nth_shared_mut_loop_pair_loop
       | List_Cons x1 tl1 =>
         if i s= 0%u32
         then
-          let back := fun (ret : T) => Return (List_Cons ret tl1) in
-          Return ((x0, x1), back)
+          let back := fun (ret : T) => Ok (List_Cons ret tl1) in
+          Ok ((x0, x1), back)
         else (
           i1 <- u32_sub i 1%u32;
           p <- list_nth_shared_mut_loop_pair_loop T n1 tl0 tl1 i1;
           let (p1, back) := p in
           let back1 :=
-            fun (ret : T) => tl11 <- back ret; Return (List_Cons x1 tl11) in
-          Return (p1, back1))
+            fun (ret : T) => tl11 <- back ret; Ok (List_Cons x1 tl11) in
+          Ok (p1, back1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -651,15 +641,15 @@ Fixpoint list_nth_shared_mut_loop_pair_merge_loop
       | List_Cons x1 tl1 =>
         if i s= 0%u32
         then
-          let back := fun (ret : T) => Return (List_Cons ret tl1) in
-          Return ((x0, x1), back)
+          let back := fun (ret : T) => Ok (List_Cons ret tl1) in
+          Ok ((x0, x1), back)
         else (
           i1 <- u32_sub i 1%u32;
           p <- list_nth_shared_mut_loop_pair_merge_loop T n1 tl0 tl1 i1;
           let (p1, back) := p in
           let back1 :=
-            fun (ret : T) => tl11 <- back ret; Return (List_Cons x1 tl11) in
-          Return (p1, back1))
+            fun (ret : T) => tl11 <- back ret; Ok (List_Cons x1 tl11) in
+          Ok (p1, back1))
       | List_Nil => Fail_ Failure
       end
     | List_Nil => Fail_ Failure
@@ -684,7 +674,7 @@ Fixpoint ignore_input_mut_borrow_loop (n : nat) (i : u32) : result unit :=
   | S n1 =>
     if i s> 0%u32
     then (i1 <- u32_sub i 1%u32; ignore_input_mut_borrow_loop n1 i1)
-    else Return tt
+    else Ok tt
   end
 .
 
@@ -692,7 +682,7 @@ Fixpoint ignore_input_mut_borrow_loop (n : nat) (i : u32) : result unit :=
     Source: 'src/loops.rs', lines 345:0-345:56 *)
 Definition ignore_input_mut_borrow
   (n : nat) (_a : u32) (i : u32) : result u32 :=
-  _ <- ignore_input_mut_borrow_loop n i; Return _a
+  _ <- ignore_input_mut_borrow_loop n i; Ok _a
 .
 
 (** [loops::incr_ignore_input_mut_borrow]: loop 0:
@@ -703,7 +693,7 @@ Fixpoint incr_ignore_input_mut_borrow_loop (n : nat) (i : u32) : result unit :=
   | S n1 =>
     if i s> 0%u32
     then (i1 <- u32_sub i 1%u32; incr_ignore_input_mut_borrow_loop n1 i1)
-    else Return tt
+    else Ok tt
   end
 .
 
@@ -711,7 +701,7 @@ Fixpoint incr_ignore_input_mut_borrow_loop (n : nat) (i : u32) : result unit :=
     Source: 'src/loops.rs', lines 353:0-353:60 *)
 Definition incr_ignore_input_mut_borrow
   (n : nat) (a : u32) (i : u32) : result u32 :=
-  a1 <- u32_add a 1%u32; _ <- incr_ignore_input_mut_borrow_loop n i; Return a1
+  a1 <- u32_add a 1%u32; _ <- incr_ignore_input_mut_borrow_loop n i; Ok a1
 .
 
 (** [loops::ignore_input_shared_borrow]: loop 0:
@@ -722,7 +712,7 @@ Fixpoint ignore_input_shared_borrow_loop (n : nat) (i : u32) : result unit :=
   | S n1 =>
     if i s> 0%u32
     then (i1 <- u32_sub i 1%u32; ignore_input_shared_borrow_loop n1 i1)
-    else Return tt
+    else Ok tt
   end
 .
 
@@ -730,7 +720,7 @@ Fixpoint ignore_input_shared_borrow_loop (n : nat) (i : u32) : result unit :=
     Source: 'src/loops.rs', lines 362:0-362:59 *)
 Definition ignore_input_shared_borrow
   (n : nat) (_a : u32) (i : u32) : result u32 :=
-  _ <- ignore_input_shared_borrow_loop n i; Return _a
+  _ <- ignore_input_shared_borrow_loop n i; Ok _a
 .
 
 End Loops.
diff --git a/tests/coq/misc/NoNestedBorrows.v b/tests/coq/misc/NoNestedBorrows.v
index d4035104..ecdfb281 100644
--- a/tests/coq/misc/NoNestedBorrows.v
+++ b/tests/coq/misc/NoNestedBorrows.v
@@ -170,12 +170,12 @@ Definition cast_bool_to_i32 (x : bool) : result i32 :=
 (** [no_nested_borrows::cast_bool_to_bool]:
     Source: 'src/no_nested_borrows.rs', lines 137:0-137:41 *)
 Definition cast_bool_to_bool (x : bool) : result bool :=
-  Return x.
+  Ok x.
 
 (** [no_nested_borrows::test2]:
     Source: 'src/no_nested_borrows.rs', lines 142:0-142:14 *)
 Definition test2 : result unit :=
-  _ <- u32_add 23%u32 44%u32; Return tt.
+  _ <- u32_add 23%u32 44%u32; Ok tt.
 
 (** Unit test for [no_nested_borrows::test2] *)
 Check (test2 )%return.
@@ -183,7 +183,7 @@ Check (test2 )%return.
 (** [no_nested_borrows::get_max]:
     Source: 'src/no_nested_borrows.rs', lines 154:0-154:37 *)
 Definition get_max (x : u32) (y : u32) : result u32 :=
-  if x s>= y then Return x else Return y
+  if x s>= y then Ok x else Ok y
 .
 
 (** [no_nested_borrows::test3]:
@@ -192,7 +192,7 @@ Definition test3 : result unit :=
   x <- get_max 4%u32 3%u32;
   y <- get_max 10%u32 11%u32;
   z <- u32_add x y;
-  if negb (z s= 15%u32) then Fail_ Failure else Return tt
+  if negb (z s= 15%u32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test3] *)
@@ -201,7 +201,7 @@ Check (test3 )%return.
 (** [no_nested_borrows::test_neg1]:
     Source: 'src/no_nested_borrows.rs', lines 169:0-169:18 *)
 Definition test_neg1 : result unit :=
-  y <- i32_neg 3%i32; if negb (y s= (-3)%i32) then Fail_ Failure else Return tt
+  y <- i32_neg 3%i32; if negb (y s= (-3)%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test_neg1] *)
@@ -210,7 +210,7 @@ Check (test_neg1 )%return.
 (** [no_nested_borrows::refs_test1]:
     Source: 'src/no_nested_borrows.rs', lines 176:0-176:19 *)
 Definition refs_test1 : result unit :=
-  if negb (1%i32 s= 1%i32) then Fail_ Failure else Return tt
+  if negb (1%i32 s= 1%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::refs_test1] *)
@@ -227,7 +227,7 @@ Definition refs_test2 : result unit :=
     else
       if negb (2%i32 s= 2%i32)
       then Fail_ Failure
-      else if negb (2%i32 s= 2%i32) then Fail_ Failure else Return tt
+      else if negb (2%i32 s= 2%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::refs_test2] *)
@@ -236,7 +236,7 @@ Check (refs_test2 )%return.
 (** [no_nested_borrows::test_list1]:
     Source: 'src/no_nested_borrows.rs', lines 203:0-203:19 *)
 Definition test_list1 : result unit :=
-  Return tt.
+  Ok tt.
 
 (** Unit test for [no_nested_borrows::test_list1] *)
 Check (test_list1 )%return.
@@ -248,7 +248,7 @@ Definition test_box1 : result unit :=
   let (_, deref_mut_back) := p in
   b <- deref_mut_back 1%i32;
   x <- alloc_boxed_Box_deref i32 b;
-  if negb (x s= 1%i32) then Fail_ Failure else Return tt
+  if negb (x s= 1%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test_box1] *)
@@ -257,24 +257,24 @@ Check (test_box1 )%return.
 (** [no_nested_borrows::copy_int]:
     Source: 'src/no_nested_borrows.rs', lines 218:0-218:30 *)
 Definition copy_int (x : i32) : result i32 :=
-  Return x.
+  Ok x.
 
 (** [no_nested_borrows::test_unreachable]:
     Source: 'src/no_nested_borrows.rs', lines 224:0-224:32 *)
 Definition test_unreachable (b : bool) : result unit :=
-  if b then Fail_ Failure else Return tt
+  if b then Fail_ Failure else Ok tt
 .
 
 (** [no_nested_borrows::test_panic]:
     Source: 'src/no_nested_borrows.rs', lines 232:0-232:26 *)
 Definition test_panic (b : bool) : result unit :=
-  if b then Fail_ Failure else Return tt
+  if b then Fail_ Failure else Ok tt
 .
 
 (** [no_nested_borrows::test_copy_int]:
     Source: 'src/no_nested_borrows.rs', lines 239:0-239:22 *)
 Definition test_copy_int : result unit :=
-  y <- copy_int 0%i32; if negb (0%i32 s= y) then Fail_ Failure else Return tt
+  y <- copy_int 0%i32; if negb (0%i32 s= y) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test_copy_int] *)
@@ -283,14 +283,14 @@ Check (test_copy_int )%return.
 (** [no_nested_borrows::is_cons]:
     Source: 'src/no_nested_borrows.rs', lines 246:0-246:38 *)
 Definition is_cons (T : Type) (l : List_t T) : result bool :=
-  match l with | List_Cons _ _ => Return true | List_Nil => Return false end
+  match l with | List_Cons _ _ => Ok true | List_Nil => Ok false end
 .
 
 (** [no_nested_borrows::test_is_cons]:
     Source: 'src/no_nested_borrows.rs', lines 253:0-253:21 *)
 Definition test_is_cons : result unit :=
   b <- is_cons i32 (List_Cons 0%i32 List_Nil);
-  if negb b then Fail_ Failure else Return tt
+  if negb b then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test_is_cons] *)
@@ -299,10 +299,7 @@ Check (test_is_cons )%return.
 (** [no_nested_borrows::split_list]:
     Source: 'src/no_nested_borrows.rs', lines 259:0-259:48 *)
 Definition split_list (T : Type) (l : List_t T) : result (T * (List_t T)) :=
-  match l with
-  | List_Cons hd tl => Return (hd, tl)
-  | List_Nil => Fail_ Failure
-  end
+  match l with | List_Cons hd tl => Ok (hd, tl) | List_Nil => Fail_ Failure end
 .
 
 (** [no_nested_borrows::test_split_list]:
@@ -310,7 +307,7 @@ Definition split_list (T : Type) (l : List_t T) : result (T * (List_t T)) :=
 Definition test_split_list : result unit :=
   p <- split_list i32 (List_Cons 0%i32 List_Nil);
   let (hd, _) := p in
-  if negb (hd s= 0%i32) then Fail_ Failure else Return tt
+  if negb (hd s= 0%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [no_nested_borrows::test_split_list] *)
@@ -321,8 +318,8 @@ Check (test_split_list )%return.
 Definition choose
   (T : Type) (b : bool) (x : T) (y : T) : result (T * (T -> result (T * T))) :=
   if b
-  then let back := fun (ret : T) => Return (ret, y) in Return (x, back)
-  else let back := fun (ret : T) => Return (x, ret) in Return (y, back)
+  then let back := fun (ret : T) => Ok (ret, y) in Ok (x, back)
+  else let back := fun (ret : T) => Ok (x, ret) in Ok (y, back)
 .
 
 (** [no_nested_borrows::choose_test]:
@@ -338,7 +335,7 @@ Definition choose_test : result unit :=
     let (x, y) := p1 in
     if negb (x s= 1%i32)
     then Fail_ Failure
-    else if negb (y s= 0%i32) then Fail_ Failure else Return tt)
+    else if negb (y s= 0%i32) then Fail_ Failure else Ok tt)
 .
 
 (** Unit test for [no_nested_borrows::choose_test] *)
@@ -347,7 +344,7 @@ Check (choose_test )%return.
 (** [no_nested_borrows::test_char]:
     Source: 'src/no_nested_borrows.rs', lines 294:0-294:26 *)
 Definition test_char : result char :=
-  Return (char_of_byte Coq.Init.Byte.x61).
+  Ok (char_of_byte Coq.Init.Byte.x61).
 
 (** [no_nested_borrows::Tree]
     Source: 'src/no_nested_borrows.rs', lines 299:0-299:16 *)
@@ -373,7 +370,7 @@ Arguments NodeElem_Nil { _ }.
 Fixpoint list_length (T : Type) (l : List_t T) : result u32 :=
   match l with
   | List_Cons _ l1 => i <- list_length T l1; u32_add 1%u32 i
-  | List_Nil => Return 0%u32
+  | List_Nil => Ok 0%u32
   end
 .
 
@@ -383,7 +380,7 @@ Fixpoint list_nth_shared (T : Type) (l : List_t T) (i : u32) : result T :=
   match l with
   | List_Cons x tl =>
     if i s= 0%u32
-    then Return x
+    then Ok x
     else (i1 <- u32_sub i 1%u32; list_nth_shared T tl i1)
   | List_Nil => Fail_ Failure
   end
@@ -398,17 +395,14 @@ Fixpoint list_nth_mut
   match l with
   | List_Cons x tl =>
     if i s= 0%u32
-    then
-      let back := fun (ret : T) => Return (List_Cons ret tl) in
-      Return (x, back)
+    then let back := fun (ret : T) => Ok (List_Cons ret tl) in Ok (x, back)
     else (
       i1 <- u32_sub i 1%u32;
       p <- list_nth_mut T tl i1;
       let (t, list_nth_mut_back) := p in
       let back :=
-        fun (ret : T) => tl1 <- list_nth_mut_back ret; Return (List_Cons x tl1)
-        in
-      Return (t, back))
+        fun (ret : T) => tl1 <- list_nth_mut_back ret; Ok (List_Cons x tl1) in
+      Ok (t, back))
   | List_Nil => Fail_ Failure
   end
 .
@@ -419,7 +413,7 @@ Fixpoint list_rev_aux
   (T : Type) (li : List_t T) (lo : List_t T) : result (List_t T) :=
   match li with
   | List_Cons hd tl => list_rev_aux T tl (List_Cons hd lo)
-  | List_Nil => Return lo
+  | List_Nil => Ok lo
   end
 .
 
@@ -463,7 +457,7 @@ Definition test_list_functions : result unit :=
             then Fail_ Failure
             else (
               i6 <- list_nth_shared i32 ls 2%u32;
-              if negb (i6 s= 2%i32) then Fail_ Failure else Return tt))))))
+              if negb (i6 s= 2%i32) then Fail_ Failure else Ok tt))))))
 .
 
 (** Unit test for [no_nested_borrows::test_list_functions] *)
@@ -475,7 +469,7 @@ Definition id_mut_pair1
   (T1 T2 : Type) (x : T1) (y : T2) :
   result ((T1 * T2) * ((T1 * T2) -> result (T1 * T2)))
   :=
-  Return ((x, y), Return)
+  Ok ((x, y), Ok)
 .
 
 (** [no_nested_borrows::id_mut_pair2]:
@@ -484,7 +478,7 @@ Definition id_mut_pair2
   (T1 T2 : Type) (p : (T1 * T2)) :
   result ((T1 * T2) * ((T1 * T2) -> result (T1 * T2)))
   :=
-  let (t, t1) := p in Return ((t, t1), Return)
+  let (t, t1) := p in Ok ((t, t1), Ok)
 .
 
 (** [no_nested_borrows::id_mut_pair3]:
@@ -493,7 +487,7 @@ Definition id_mut_pair3
   (T1 T2 : Type) (x : T1) (y : T2) :
   result ((T1 * T2) * (T1 -> result T1) * (T2 -> result T2))
   :=
-  Return ((x, y), Return, Return)
+  Ok ((x, y), Ok, Ok)
 .
 
 (** [no_nested_borrows::id_mut_pair4]:
@@ -502,7 +496,7 @@ Definition id_mut_pair4
   (T1 T2 : Type) (p : (T1 * T2)) :
   result ((T1 * T2) * (T1 -> result T1) * (T2 -> result T2))
   :=
-  let (t, t1) := p in Return ((t, t1), Return, Return)
+  let (t, t1) := p in Ok ((t, t1), Ok, Ok)
 .
 
 (** [no_nested_borrows::StructWithTuple]
@@ -519,19 +513,19 @@ Arguments structWithTuple_p { _ _ }.
 (** [no_nested_borrows::new_tuple1]:
     Source: 'src/no_nested_borrows.rs', lines 437:0-437:48 *)
 Definition new_tuple1 : result (StructWithTuple_t u32 u32) :=
-  Return {| structWithTuple_p := (1%u32, 2%u32) |}
+  Ok {| structWithTuple_p := (1%u32, 2%u32) |}
 .
 
 (** [no_nested_borrows::new_tuple2]:
     Source: 'src/no_nested_borrows.rs', lines 441:0-441:48 *)
 Definition new_tuple2 : result (StructWithTuple_t i16 i16) :=
-  Return {| structWithTuple_p := (1%i16, 2%i16) |}
+  Ok {| structWithTuple_p := (1%i16, 2%i16) |}
 .
 
 (** [no_nested_borrows::new_tuple3]:
     Source: 'src/no_nested_borrows.rs', lines 445:0-445:48 *)
 Definition new_tuple3 : result (StructWithTuple_t u64 i64) :=
-  Return {| structWithTuple_p := (1%u64, 2%i64) |}
+  Ok {| structWithTuple_p := (1%u64, 2%i64) |}
 .
 
 (** [no_nested_borrows::StructWithPair]
@@ -548,7 +542,7 @@ Arguments structWithPair_p { _ _ }.
 (** [no_nested_borrows::new_pair1]:
     Source: 'src/no_nested_borrows.rs', lines 454:0-454:46 *)
 Definition new_pair1 : result (StructWithPair_t u32 u32) :=
-  Return {| structWithPair_p := {| pair_x := 1%u32; pair_y := 2%u32 |} |}
+  Ok {| structWithPair_p := {| pair_x := 1%u32; pair_y := 2%u32 |} |}
 .
 
 (** [no_nested_borrows::test_constants]:
@@ -572,7 +566,7 @@ Definition test_constants : result unit :=
         swp <- new_pair1;
         if negb (swp.(structWithPair_p).(pair_x) s= 1%u32)
         then Fail_ Failure
-        else Return tt)))
+        else Ok tt)))
 .
 
 (** Unit test for [no_nested_borrows::test_constants] *)
@@ -581,7 +575,7 @@ Check (test_constants )%return.
 (** [no_nested_borrows::test_weird_borrows1]:
     Source: 'src/no_nested_borrows.rs', lines 471:0-471:28 *)
 Definition test_weird_borrows1 : result unit :=
-  Return tt.
+  Ok tt.
 
 (** Unit test for [no_nested_borrows::test_weird_borrows1] *)
 Check (test_weird_borrows1 )%return.
@@ -590,30 +584,30 @@ Check (test_weird_borrows1 )%return.
     Source: 'src/no_nested_borrows.rs', lines 481:0-481:37 *)
 Definition test_mem_replace (px : u32) : result u32 :=
   let (y, _) := core_mem_replace u32 px 1%u32 in
-  if negb (y s= 0%u32) then Fail_ Failure else Return 2%u32
+  if negb (y s= 0%u32) then Fail_ Failure else Ok 2%u32
 .
 
 (** [no_nested_borrows::test_shared_borrow_bool1]:
     Source: 'src/no_nested_borrows.rs', lines 488:0-488:47 *)
 Definition test_shared_borrow_bool1 (b : bool) : result u32 :=
-  if b then Return 0%u32 else Return 1%u32
+  if b then Ok 0%u32 else Ok 1%u32
 .
 
 (** [no_nested_borrows::test_shared_borrow_bool2]:
     Source: 'src/no_nested_borrows.rs', lines 501:0-501:40 *)
 Definition test_shared_borrow_bool2 : result u32 :=
-  Return 0%u32.
+  Ok 0%u32.
 
 (** [no_nested_borrows::test_shared_borrow_enum1]:
     Source: 'src/no_nested_borrows.rs', lines 516:0-516:52 *)
 Definition test_shared_borrow_enum1 (l : List_t u32) : result u32 :=
-  match l with | List_Cons _ _ => Return 1%u32 | List_Nil => Return 0%u32 end
+  match l with | List_Cons _ _ => Ok 1%u32 | List_Nil => Ok 0%u32 end
 .
 
 (** [no_nested_borrows::test_shared_borrow_enum2]:
     Source: 'src/no_nested_borrows.rs', lines 528:0-528:40 *)
 Definition test_shared_borrow_enum2 : result u32 :=
-  Return 0%u32.
+  Ok 0%u32.
 
 (** [no_nested_borrows::incr]:
     Source: 'src/no_nested_borrows.rs', lines 539:0-539:24 *)
@@ -628,7 +622,7 @@ Definition call_incr (x : u32) : result u32 :=
 (** [no_nested_borrows::read_then_incr]:
     Source: 'src/no_nested_borrows.rs', lines 548:0-548:41 *)
 Definition read_then_incr (x : u32) : result (u32 * u32) :=
-  x1 <- u32_add x 1%u32; Return (x, x1)
+  x1 <- u32_add x 1%u32; Ok (x, x1)
 .
 
 (** [no_nested_borrows::Tuple]
@@ -638,14 +632,14 @@ Definition Tuple_t (T1 T2 : Type) : Type := T1 * T2.
 (** [no_nested_borrows::use_tuple_struct]:
     Source: 'src/no_nested_borrows.rs', lines 556:0-556:48 *)
 Definition use_tuple_struct (x : Tuple_t u32 u32) : result (Tuple_t u32 u32) :=
-  let (_, i) := x in Return (1%u32, i)
+  let (_, i) := x in Ok (1%u32, i)
 .
 
 (** [no_nested_borrows::create_tuple_struct]:
     Source: 'src/no_nested_borrows.rs', lines 560:0-560:61 *)
 Definition create_tuple_struct
   (x : u32) (y : u64) : result (Tuple_t u32 u64) :=
-  Return (x, y)
+  Ok (x, y)
 .
 
 (** [no_nested_borrows::IdType]
@@ -655,11 +649,11 @@ Definition IdType_t (T : Type) : Type := T.
 (** [no_nested_borrows::use_id_type]:
     Source: 'src/no_nested_borrows.rs', lines 567:0-567:40 *)
 Definition use_id_type (T : Type) (x : IdType_t T) : result T :=
-  Return x.
+  Ok x.
 
 (** [no_nested_borrows::create_id_type]:
     Source: 'src/no_nested_borrows.rs', lines 571:0-571:43 *)
 Definition create_id_type (T : Type) (x : T) : result (IdType_t T) :=
-  Return x.
+  Ok x.
 
 End NoNestedBorrows.
diff --git a/tests/coq/misc/Paper.v b/tests/coq/misc/Paper.v
index 77276223..5995de15 100644
--- a/tests/coq/misc/Paper.v
+++ b/tests/coq/misc/Paper.v
@@ -16,7 +16,7 @@ Definition ref_incr (x : i32) : result i32 :=
 (** [paper::test_incr]:
     Source: 'src/paper.rs', lines 8:0-8:18 *)
 Definition test_incr : result unit :=
-  x <- ref_incr 0%i32; if negb (x s= 1%i32) then Fail_ Failure else Return tt
+  x <- ref_incr 0%i32; if negb (x s= 1%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [paper::test_incr] *)
@@ -27,8 +27,8 @@ Check (test_incr )%return.
 Definition choose
   (T : Type) (b : bool) (x : T) (y : T) : result (T * (T -> result (T * T))) :=
   if b
-  then let back := fun (ret : T) => Return (ret, y) in Return (x, back)
-  else let back := fun (ret : T) => Return (x, ret) in Return (y, back)
+  then let back := fun (ret : T) => Ok (ret, y) in Ok (x, back)
+  else let back := fun (ret : T) => Ok (x, ret) in Ok (y, back)
 .
 
 (** [paper::test_choose]:
@@ -44,7 +44,7 @@ Definition test_choose : result unit :=
     let (x, y) := p1 in
     if negb (x s= 1%i32)
     then Fail_ Failure
-    else if negb (y s= 0%i32) then Fail_ Failure else Return tt)
+    else if negb (y s= 0%i32) then Fail_ Failure else Ok tt)
 .
 
 (** Unit test for [paper::test_choose] *)
@@ -69,17 +69,14 @@ Fixpoint list_nth_mut
   match l with
   | List_Cons x tl =>
     if i s= 0%u32
-    then
-      let back := fun (ret : T) => Return (List_Cons ret tl) in
-      Return (x, back)
+    then let back := fun (ret : T) => Ok (List_Cons ret tl) in Ok (x, back)
     else (
       i1 <- u32_sub i 1%u32;
       p <- list_nth_mut T tl i1;
       let (t, list_nth_mut_back) := p in
       let back :=
-        fun (ret : T) => tl1 <- list_nth_mut_back ret; Return (List_Cons x tl1)
-        in
-      Return (t, back))
+        fun (ret : T) => tl1 <- list_nth_mut_back ret; Ok (List_Cons x tl1) in
+      Ok (t, back))
   | List_Nil => Fail_ Failure
   end
 .
@@ -89,7 +86,7 @@ Fixpoint list_nth_mut
 Fixpoint sum (l : List_t i32) : result i32 :=
   match l with
   | List_Cons x tl => i <- sum tl; i32_add x i
-  | List_Nil => Return 0%i32
+  | List_Nil => Ok 0%i32
   end
 .
 
@@ -103,7 +100,7 @@ Definition test_nth : result unit :=
   x1 <- i32_add x 1%i32;
   l2 <- list_nth_mut_back x1;
   i <- sum l2;
-  if negb (i s= 7%i32) then Fail_ Failure else Return tt
+  if negb (i s= 7%i32) then Fail_ Failure else Ok tt
 .
 
 (** Unit test for [paper::test_nth] *)
@@ -118,7 +115,7 @@ Definition call_choose (p : (u32 * u32)) : result u32 :=
   pz1 <- u32_add pz 1%u32;
   p2 <- choose_back pz1;
   let (px1, _) := p2 in
-  Return px1
+  Ok px1
 .
 
 End Paper.
diff --git a/tests/coq/misc/PoloniusList.v b/tests/coq/misc/PoloniusList.v
index dfa09328..8af7f69c 100644
--- a/tests/coq/misc/PoloniusList.v
+++ b/tests/coq/misc/PoloniusList.v
@@ -27,15 +27,15 @@ Fixpoint get_list_at_x
   match ls with
   | List_Cons hd tl =>
     if hd s= x
-    then Return (List_Cons hd tl, Return)
+    then Ok (List_Cons hd tl, Ok)
     else (
       p <- get_list_at_x tl x;
       let (l, get_list_at_x_back) := p in
       let back :=
         fun (ret : List_t u32) =>
-          tl1 <- get_list_at_x_back ret; Return (List_Cons hd tl1) in
-      Return (l, back))
-  | List_Nil => Return (List_Nil, Return)
+          tl1 <- get_list_at_x_back ret; Ok (List_Cons hd tl1) in
+      Ok (l, back))
+  | List_Nil => Ok (List_Nil, Ok)
   end
 .
 
diff --git a/tests/coq/misc/Primitives.v b/tests/coq/misc/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/misc/Primitives.v
+++ b/tests/coq/misc/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/traits/Primitives.v b/tests/coq/traits/Primitives.v
index 990e27e4..e84d65ce 100644
--- a/tests/coq/traits/Primitives.v
+++ b/tests/coq/traits/Primitives.v
@@ -19,19 +19,19 @@ Inductive error :=
   | OutOfFuel.
 
 Inductive result A :=
-  | Return : A -> result A
+  | Ok : A -> result A
   | Fail_ : error -> result A.
 
-Arguments Return {_} a.
+Arguments Ok {_} a.
 Arguments Fail_ {_}.
 
 Definition bind {A B} (m: result A) (f: A -> result B) : result B :=
   match m with
   | Fail_ e => Fail_ e
-  | Return x => f x
+  | Ok x => f x
   end.
 
-Definition return_ {A: Type} (x: A) : result A := Return x.
+Definition return_ {A: Type} (x: A) : result A := Ok x.
 Definition fail_ {A: Type} (e: error) : result A := Fail_ e.
 
 Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
@@ -39,27 +39,27 @@ Notation "x <- c1 ; c2" := (bind c1 (fun x => c2))
 
 (** Monadic assert *)
 Definition massert (b: bool) : result unit :=
-  if b then Return tt else Fail_ Failure.
+  if b then Ok tt else Fail_ Failure.
 
 (** Normalize and unwrap a successful result (used for globals) *)
-Definition eval_result_refl {A} {x} (a: result A) (p: a = Return x) : A :=
-  match a as r return (r = Return x -> A) with
-  | Return a' => fun _  => a'
+Definition eval_result_refl {A} {x} (a: result A) (p: a = Ok x) : A :=
+  match a as r return (r = Ok x -> A) with
+  | Ok a' => fun _  => a'
   | Fail_ e   => fun p' =>
       False_rect _ (eq_ind (Fail_ e)
           (fun e : result A =>
           match e with
-          | Return _ => False
+          | Ok _ => False
           | Fail_ e => True
           end)
-        I (Return x) p')
+        I (Ok x) p')
   end p.
 
 Notation "x %global" := (eval_result_refl x eq_refl) (at level 40).
 Notation "x %return" := (eval_result_refl x eq_refl) (at level 40).
 
 (* Sanity check *)
-Check (if true then Return (1 + 2) else Fail_ Failure)%global = 3.
+Check (if true then Ok (1 + 2) else Fail_ Failure)%global = 3.
 
 (*** Misc *)
 
@@ -236,7 +236,7 @@ Import Sumbool.
 
 Definition mk_scalar (ty: scalar_ty) (x: Z) : result (scalar ty) :=
   match sumbool_of_bool (scalar_in_bounds ty x) with
-  | left H => Return (exist _ x (scalar_in_bounds_valid _ _ H))
+  | left H => Ok (exist _ x (scalar_in_bounds_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
@@ -544,9 +544,9 @@ Arguments core_ops_range_Range_end_ {_}.
 
 (*** [alloc] *)
 
-Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Return x.
+Definition alloc_boxed_Box_deref (T : Type) (x : T) : result T := Ok x.
 Definition alloc_boxed_Box_deref_mut (T : Type) (x : T) : result (T * (T -> result T)) :=
-  Return (x, fun x => Return x).
+  Ok (x, fun x => Ok x).
 
 (* Trait instance *)
 Definition alloc_boxed_Box_coreopsDerefInst (Self : Type) : core_ops_deref_Deref Self := {|
@@ -589,7 +589,7 @@ Definition array_index_mut_usize (T : Type) (n : usize) (a : array T n) (i : usi
   result (T * (T -> result (array T n))) :=
   match array_index_usize T n a i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_update_usize T n a i)
+  | Ok x => Ok (x, array_update_usize T n a i)
   end.
 
 (*** Slice *)
@@ -603,7 +603,7 @@ Definition slice_index_mut_usize (T : Type) (s : slice T) (i : usize) :
   result (T * (T -> result (slice T))) :=
   match slice_index_usize T s i with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, slice_update_usize T s i)
+  | Ok x => Ok (x, slice_update_usize T s i)
   end.
 
 (*** Subslices *)
@@ -615,7 +615,7 @@ Definition array_to_slice_mut (T : Type) (n : usize) (a : array T n) :
   result (slice T * (slice T -> result (array T n))) :=
   match array_to_slice T n a with
   | Fail_ e => Fail_ e
-  | Return x => Return (x, array_from_slice T n a)
+  | Ok x => Ok (x, array_from_slice T n a)
   end.
 
 Axiom array_subslice: forall (T : Type) (n : usize) (x : array T n) (r : core_ops_range_Range usize), result (slice T).
@@ -657,17 +657,17 @@ end end.
 Definition alloc_vec_Vec_bind {A B} (v: alloc_vec_Vec A) (f: list A -> result (list B)) : result (alloc_vec_Vec B) :=
   l <- f (alloc_vec_Vec_to_list v) ;
   match sumbool_of_bool (scalar_le_max Usize (Z.of_nat (length l))) with
-  | left H => Return (exist _ l (scalar_le_max_valid _ _ H))
+  | left H => Ok (exist _ l (scalar_le_max_valid _ _ H))
   | right _ => Fail_ Failure
   end.
 
 Definition alloc_vec_Vec_push (T: Type) (v: alloc_vec_Vec T) (x: T) : result (alloc_vec_Vec T) :=
-  alloc_vec_Vec_bind v (fun l => Return (l ++ [x])).
+  alloc_vec_Vec_bind v (fun l => Ok (l ++ [x])).
 
 Definition alloc_vec_Vec_insert (T: Type) (v: alloc_vec_Vec T) (i: usize) (x: T) : result (alloc_vec_Vec T) :=
   alloc_vec_Vec_bind v (fun l =>
     if to_Z i <? Z.of_nat (length l)
-    then Return (list_update l (usize_to_nat i) x)
+    then Ok (list_update l (usize_to_nat i) x)
     else Fail_ Failure).
 
 (* Helper *)
@@ -679,8 +679,8 @@ Axiom alloc_vec_Vec_update_usize : forall {T : Type} (v : alloc_vec_Vec T) (i :
 Definition alloc_vec_Vec_index_mut_usize {T : Type} (v: alloc_vec_Vec T) (i: usize) :
   result (T * (T -> result (alloc_vec_Vec T))) :=
   match alloc_vec_Vec_index_usize v i with
-  | Return x =>
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x =>
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail_ e => Fail_ e
   end.
 
@@ -717,7 +717,7 @@ Definition core_slice_index_Slice_index
   x <- inst.(core_slice_index_SliceIndex_get) i s;
   match x with
   | None => Fail_ Failure
-  | Some x => Return x
+  | Some x => Ok x
   end.
 
 (* [core::slice::index::Range:::get]: forward function *)
diff --git a/tests/coq/traits/Traits.v b/tests/coq/traits/Traits.v
index 0e942c7d..fb37a507 100644
--- a/tests/coq/traits/Traits.v
+++ b/tests/coq/traits/Traits.v
@@ -20,7 +20,7 @@ Arguments BoolTrait_t_get_bool { _ }.
 (** [traits::{(traits::BoolTrait for bool)}::get_bool]:
     Source: 'src/traits.rs', lines 12:4-12:30 *)
 Definition boolTraitBool_get_bool (self : bool) : result bool :=
-  Return self.
+  Ok self.
 
 (** Trait implementation: [traits::{(traits::BoolTrait for bool)}]
     Source: 'src/traits.rs', lines 11:0-11:23 *)
@@ -32,21 +32,21 @@ Definition BoolTraitBool : BoolTrait_t bool := {|
     Source: 'src/traits.rs', lines 6:4-6:30 *)
 Definition boolTrait_ret_true
   {Self : Type} (self_clause : BoolTrait_t Self) (self : Self) : result bool :=
-  Return true
+  Ok true
 .
 
 (** [traits::test_bool_trait_bool]:
     Source: 'src/traits.rs', lines 17:0-17:44 *)
 Definition test_bool_trait_bool (x : bool) : result bool :=
   b <- boolTraitBool_get_bool x;
-  if b then boolTrait_ret_true BoolTraitBool x else Return false
+  if b then boolTrait_ret_true BoolTraitBool x else Ok false
 .
 
 (** [traits::{(traits::BoolTrait for core::option::Option<T>)#1}::get_bool]:
     Source: 'src/traits.rs', lines 23:4-23:30 *)
 Definition boolTraitOption_get_bool
   (T : Type) (self : option T) : result bool :=
-  match self with | None => Return false | Some _ => Return true end
+  match self with | None => Ok false | Some _ => Ok true end
 .
 
 (** Trait implementation: [traits::{(traits::BoolTrait for core::option::Option<T>)#1}]
@@ -59,7 +59,7 @@ Definition BoolTraitOption (T : Type) : BoolTrait_t (option T) := {|
     Source: 'src/traits.rs', lines 31:0-31:54 *)
 Definition test_bool_trait_option (T : Type) (x : option T) : result bool :=
   b <- boolTraitOption_get_bool T x;
-  if b then boolTrait_ret_true (BoolTraitOption T) x else Return false
+  if b then boolTrait_ret_true (BoolTraitOption T) x else Ok false
 .
 
 (** [traits::test_bool_trait]:
@@ -81,7 +81,7 @@ Arguments ToU64_t_to_u64 { _ }.
 (** [traits::{(traits::ToU64 for u64)#2}::to_u64]:
     Source: 'src/traits.rs', lines 44:4-44:26 *)
 Definition toU64U64_to_u64 (self : u64) : result u64 :=
-  Return self.
+  Ok self.
 
 (** Trait implementation: [traits::{(traits::ToU64 for u64)#2}]
     Source: 'src/traits.rs', lines 43:0-43:18 *)
@@ -167,7 +167,7 @@ Arguments ToType_t_to_type { _ _ }.
 (** [traits::{(traits::ToType<bool> for u64)#5}::to_type]:
     Source: 'src/traits.rs', lines 93:4-93:28 *)
 Definition toTypeU64Bool_to_type (self : u64) : result bool :=
-  Return (self s> 0%u64)
+  Ok (self s> 0%u64)
 .
 
 (** Trait implementation: [traits::{(traits::ToType<bool> for u64)#5}]
@@ -238,7 +238,7 @@ Arguments TestType_test_TestTrait_t_test { _ }.
     Source: 'src/traits.rs', lines 139:12-139:34 *)
 Definition testType_test_TestTraittraitsTestTypetestTestType1_test
   (self : TestType_test_TestType1_t) : result bool :=
-  Return (self s> 1%u64)
+  Ok (self s> 1%u64)
 .
 
 (** Trait implementation: [traits::{traits::TestType<T>#6}::test::{(traits::{traits::TestType<T>#6}::test::TestTrait for traits::{traits::TestType<T>#6}::test::TestType1)}]
@@ -258,7 +258,7 @@ Definition testType_test
   x1 <- toU64Inst.(ToU64_t_to_u64) x;
   if x1 s> 0%u64
   then testType_test_TestTraittraitsTestTypetestTestType1_test 0%u64
-  else Return false
+  else Ok false
 .
 
 (** [traits::BoolWrapper]
@@ -285,7 +285,7 @@ Definition ToTypetraitsBoolWrapperT (T : Type) (toTypeBoolTInst : ToType_t bool
     Source: 'src/traits.rs', lines 164:4-164:21 *)
 Definition with_const_ty_len2_default_body (Self : Type) (LEN : usize)
   : result usize :=
-  Return 32%usize
+  Ok 32%usize
 .
 Definition with_const_ty_len2_default (Self : Type) (LEN : usize) : usize :=
   (with_const_ty_len2_default_body Self LEN)%global
@@ -313,7 +313,7 @@ Arguments WithConstTy_t_f { _ _ }.
 
 (** [traits::{(traits::WithConstTy<32: usize> for bool)#8}::LEN1]
     Source: 'src/traits.rs', lines 175:4-175:21 *)
-Definition with_const_ty_bool32_len1_body : result usize := Return 12%usize.
+Definition with_const_ty_bool32_len1_body : result usize := Ok 12%usize.
 Definition with_const_ty_bool32_len1 : usize :=
   with_const_ty_bool32_len1_body%global
 .
@@ -322,7 +322,7 @@ Definition with_const_ty_bool32_len1 : usize :=
     Source: 'src/traits.rs', lines 180:4-180:39 *)
 Definition withConstTyBool32_f
   (i : u64) (a : array u8 32%usize) : result u64 :=
-  Return i
+  Ok i
 .
 
 (** Trait implementation: [traits::{(traits::WithConstTy<32: usize> for bool)#8}]
@@ -342,7 +342,7 @@ Definition use_with_const_ty1
   (H : Type) (LEN : usize) (withConstTyInst : WithConstTy_t H LEN) :
   result usize
   :=
-  Return withConstTyInst.(WithConstTy_tWithConstTy_t_LEN1)
+  Ok withConstTyInst.(WithConstTy_tWithConstTy_t_LEN1)
 .
 
 (** [traits::use_with_const_ty2]:
@@ -352,7 +352,7 @@ Definition use_with_const_ty2
   (w : withConstTyInst.(WithConstTy_tWithConstTy_t_W)) :
   result unit
   :=
-  Return tt
+  Ok tt
 .
 
 (** [traits::use_with_const_ty3]:
@@ -368,7 +368,7 @@ Definition use_with_const_ty3
 (** [traits::test_where1]:
     Source: 'src/traits.rs', lines 193:0-193:40 *)
 Definition test_where1 (T : Type) (_x : T) : result unit :=
-  Return tt.
+  Ok tt.
 
 (** [traits::test_where2]:
     Source: 'src/traits.rs', lines 194:0-194:57 *)
@@ -376,7 +376,7 @@ Definition test_where2
   (T : Type) (withConstTyT32Inst : WithConstTy_t T 32%usize) (_x : u32) :
   result unit
   :=
-  Return tt
+  Ok tt
 .
 
 (** Trait declaration: [traits::ParentTrait0]
@@ -435,7 +435,7 @@ Definition order1
   ParentTrait0_t U) :
   result unit
   :=
-  Return tt
+  Ok tt
 .
 
 (** Trait declaration: [traits::ChildTrait1]
@@ -552,7 +552,7 @@ Definition ParentTrait2U32 : ParentTrait2_t u32 := {|
 (** [traits::{(traits::ChildTrait2 for u32)#13}::convert]:
     Source: 'src/traits.rs', lines 273:4-273:29 *)
 Definition childTrait2U32_convert (x : u32) : result u32 :=
-  Return x.
+  Ok x.
 
 (** Trait implementation: [traits::{(traits::ChildTrait2 for u32)#13}]
     Source: 'src/traits.rs', lines 272:0-272:24 *)
@@ -625,9 +625,7 @@ Arguments Trait_tTrait_t_LEN { _ }.
 
 (** [traits::{(traits::Trait for @Array<T, N>)#14}::LEN]
     Source: 'src/traits.rs', lines 315:4-315:20 *)
-Definition trait_array_len_body (T : Type) (N : usize) : result usize :=
-  Return N
-.
+Definition trait_array_len_body (T : Type) (N : usize) : result usize := Ok N.
 Definition trait_array_len (T : Type) (N : usize) : usize :=
   (trait_array_len_body T N)%global
 .
@@ -642,7 +640,7 @@ Definition TraitArray (T : Type) (N : usize) : Trait_t (array T N) := {|
     Source: 'src/traits.rs', lines 319:4-319:20 *)
 Definition traittraits_wrapper_len_body (T : Type) (traitInst : Trait_t T)
   : result usize :=
-  Return 0%usize
+  Ok 0%usize
 .
 Definition traittraits_wrapper_len (T : Type) (traitInst : Trait_t T)
   : usize :=
@@ -659,7 +657,7 @@ Definition TraittraitsWrapper (T : Type) (traitInst : Trait_t T) : Trait_t
 (** [traits::use_wrapper_len]:
     Source: 'src/traits.rs', lines 322:0-322:43 *)
 Definition use_wrapper_len (T : Type) (traitInst : Trait_t T) : result usize :=
-  Return (TraittraitsWrapper T traitInst).(Trait_tTrait_t_LEN)
+  Ok (TraittraitsWrapper T traitInst).(Trait_tTrait_t_LEN)
 .
 
 (** [traits::Foo]
@@ -685,7 +683,7 @@ Arguments Core_result_Result_Err { _ _ }.
     Source: 'src/traits.rs', lines 332:4-332:33 *)
 Definition foo_foo_body (T U : Type) (traitInst : Trait_t T)
   : result (core_result_Result_t T i32) :=
-  Return (Core_result_Result_Err 0%i32)
+  Ok (Core_result_Result_Err 0%i32)
 .
 Definition foo_foo (T U : Type) (traitInst : Trait_t T)
   : core_result_Result_t T i32 :=
@@ -696,14 +694,14 @@ Definition foo_foo (T U : Type) (traitInst : Trait_t T)
     Source: 'src/traits.rs', lines 335:0-335:48 *)
 Definition use_foo1
   (T U : Type) (traitInst : Trait_t T) : result (core_result_Result_t T i32) :=
-  Return (foo_foo T U traitInst)
+  Ok (foo_foo T U traitInst)
 .
 
 (** [traits::use_foo2]:
     Source: 'src/traits.rs', lines 339:0-339:48 *)
 Definition use_foo2
   (T U : Type) (traitInst : Trait_t U) : result (core_result_Result_t U i32) :=
-  Return (foo_foo U T traitInst)
+  Ok (foo_foo U T traitInst)
 .
 
 End Traits.
diff --git a/tests/fstar/arrays/Arrays.Funs.fst b/tests/fstar/arrays/Arrays.Funs.fst
index 731c7290..983b3761 100644
--- a/tests/fstar/arrays/Arrays.Funs.fst
+++ b/tests/fstar/arrays/Arrays.Funs.fst
@@ -28,17 +28,17 @@ let array_to_mut_slice_
 (** [arrays::array_len]:
     Source: 'src/arrays.rs', lines 25:0-25:40 *)
 let array_len (t : Type0) (s : array t 32) : result usize =
-  let* s1 = array_to_slice t 32 s in Return (slice_len t s1)
+  let* s1 = array_to_slice t 32 s in Ok (slice_len t s1)
 
 (** [arrays::shared_array_len]:
     Source: 'src/arrays.rs', lines 29:0-29:48 *)
 let shared_array_len (t : Type0) (s : array t 32) : result usize =
-  let* s1 = array_to_slice t 32 s in Return (slice_len t s1)
+  let* s1 = array_to_slice t 32 s in Ok (slice_len t s1)
 
 (** [arrays::shared_slice_len]:
     Source: 'src/arrays.rs', lines 33:0-33:44 *)
 let shared_slice_len (t : Type0) (s : slice t) : result usize =
-  Return (slice_len t s)
+  Ok (slice_len t s)
 
 (** [arrays::index_array_shared]:
     Source: 'src/arrays.rs', lines 37:0-37:57 *)
@@ -94,7 +94,7 @@ let slice_subslice_mut_
     core_slice_index_Slice_index_mut u32 (core_ops_range_Range usize)
       (core_slice_index_SliceIndexRangeUsizeSliceTInst u32) x
       { start = y; end_ = z } in
-  Return (s, index_mut_back)
+  Ok (s, index_mut_back)
 
 (** [arrays::array_to_slice_shared_]:
     Source: 'src/arrays.rs', lines 72:0-72:54 *)
@@ -129,7 +129,7 @@ let array_subslice_mut_
       (core_ops_index_IndexMutSliceTIInst u32 (core_ops_range_Range usize)
       (core_slice_index_SliceIndexRangeUsizeSliceTInst u32)) x
       { start = y; end_ = z } in
-  Return (s, index_mut_back)
+  Ok (s, index_mut_back)
 
 (** [arrays::index_slice_0]:
     Source: 'src/arrays.rs', lines 88:0-88:38 *)
@@ -156,42 +156,42 @@ let update_update_array
   let* (_, index_mut_back1) = array_index_mut_usize u32 32 a j in
   let* a1 = index_mut_back1 0 in
   let* _ = index_mut_back a1 in
-  Return ()
+  Ok ()
 
 (** [arrays::array_local_deep_copy]:
     Source: 'src/arrays.rs', lines 118:0-118:43 *)
 let array_local_deep_copy (x : array u32 32) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::take_array]:
     Source: 'src/arrays.rs', lines 122:0-122:30 *)
 let take_array (a : array u32 2) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::take_array_borrow]:
     Source: 'src/arrays.rs', lines 123:0-123:38 *)
 let take_array_borrow (a : array u32 2) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::take_slice]:
     Source: 'src/arrays.rs', lines 124:0-124:28 *)
 let take_slice (s : slice u32) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::take_mut_slice]:
     Source: 'src/arrays.rs', lines 125:0-125:36 *)
 let take_mut_slice (s : slice u32) : result (slice u32) =
-  Return s
+  Ok s
 
 (** [arrays::const_array]:
     Source: 'src/arrays.rs', lines 127:0-127:32 *)
 let const_array : result (array u32 2) =
-  Return (mk_array u32 2 [ 0; 0 ])
+  Ok (mk_array u32 2 [ 0; 0 ])
 
 (** [arrays::const_slice]:
     Source: 'src/arrays.rs', lines 131:0-131:20 *)
 let const_slice : result unit =
-  let* _ = array_to_slice u32 2 (mk_array u32 2 [ 0; 0 ]) in Return ()
+  let* _ = array_to_slice u32 2 (mk_array u32 2 [ 0; 0 ]) in Ok ()
 
 (** [arrays::take_all]:
     Source: 'src/arrays.rs', lines 141:0-141:17 *)
@@ -205,7 +205,7 @@ let take_all : result unit =
     array_to_slice_mut u32 2 (mk_array u32 2 [ 0; 0 ]) in
   let* s2 = take_mut_slice s1 in
   let* _ = to_slice_mut_back s2 in
-  Return ()
+  Ok ()
 
 (** [arrays::index_array]:
     Source: 'src/arrays.rs', lines 155:0-155:38 *)
@@ -225,7 +225,7 @@ let index_slice_u32_0 (x : slice u32) : result u32 =
 (** [arrays::index_mut_slice_u32_0]:
     Source: 'src/arrays.rs', lines 166:0-166:50 *)
 let index_mut_slice_u32_0 (x : slice u32) : result (u32 & (slice u32)) =
-  let* i = slice_index_usize u32 x 0 in Return (i, x)
+  let* i = slice_index_usize u32 x 0 in Ok (i, x)
 
 (** [arrays::index_all]:
     Source: 'src/arrays.rs', lines 170:0-170:25 *)
@@ -243,14 +243,14 @@ let index_all : result u32 =
   let* (i7, s2) = index_mut_slice_u32_0 s1 in
   let* i8 = u32_add i6 i7 in
   let* _ = to_slice_mut_back s2 in
-  Return i8
+  Ok i8
 
 (** [arrays::update_array]:
     Source: 'src/arrays.rs', lines 184:0-184:36 *)
 let update_array (x : array u32 2) : result unit =
   let* (_, index_mut_back) = array_index_mut_usize u32 2 x 0 in
   let* _ = index_mut_back 1 in
-  Return ()
+  Ok ()
 
 (** [arrays::update_array_mut_borrow]:
     Source: 'src/arrays.rs', lines 187:0-187:48 *)
@@ -272,7 +272,7 @@ let update_all : result unit =
   let* (s, to_slice_mut_back) = array_to_slice_mut u32 2 x in
   let* s1 = update_mut_slice s in
   let* _ = to_slice_mut_back s1 in
-  Return ()
+  Ok ()
 
 (** [arrays::range_all]:
     Source: 'src/arrays.rs', lines 205:0-205:18 *)
@@ -284,7 +284,7 @@ let range_all : result unit =
       (mk_array u32 4 [ 0; 0; 0; 0 ]) { start = 1; end_ = 3 } in
   let* s1 = update_mut_slice s in
   let* _ = index_mut_back s1 in
-  Return ()
+  Ok ()
 
 (** [arrays::deref_array_borrow]:
     Source: 'src/arrays.rs', lines 214:0-214:46 *)
@@ -294,12 +294,12 @@ let deref_array_borrow (x : array u32 2) : result u32 =
 (** [arrays::deref_array_mut_borrow]:
     Source: 'src/arrays.rs', lines 219:0-219:54 *)
 let deref_array_mut_borrow (x : array u32 2) : result (u32 & (array u32 2)) =
-  let* i = array_index_usize u32 2 x 0 in Return (i, x)
+  let* i = array_index_usize u32 2 x 0 in Ok (i, x)
 
 (** [arrays::take_array_t]:
     Source: 'src/arrays.rs', lines 227:0-227:31 *)
 let take_array_t (a : array aB_t 2) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::non_copyable_array]:
     Source: 'src/arrays.rs', lines 229:0-229:27 *)
@@ -319,7 +319,7 @@ let rec sum_loop
     let* sum3 = u32_add sum1 i2 in
     let* i3 = usize_add i 1 in
     sum_loop s sum3 i3
-  else Return sum1
+  else Ok sum1
 
 (** [arrays::sum]:
     Source: 'src/arrays.rs', lines 242:0-242:28 *)
@@ -341,7 +341,7 @@ let rec sum2_loop
     let* sum3 = u32_add sum1 i4 in
     let* i5 = usize_add i 1 in
     sum2_loop s s2 sum3 i5
-  else Return sum1
+  else Ok sum1
 
 (** [arrays::sum2]:
     Source: 'src/arrays.rs', lines 252:0-252:41 *)
@@ -358,7 +358,7 @@ let f0 : result unit =
   let* (_, index_mut_back) = slice_index_mut_usize u32 s 0 in
   let* s1 = index_mut_back 1 in
   let* _ = to_slice_mut_back s1 in
-  Return ()
+  Ok ()
 
 (** [arrays::f1]:
     Source: 'src/arrays.rs', lines 268:0-268:11 *)
@@ -366,12 +366,12 @@ let f1 : result unit =
   let* (_, index_mut_back) =
     array_index_mut_usize u32 2 (mk_array u32 2 [ 1; 2 ]) 0 in
   let* _ = index_mut_back 1 in
-  Return ()
+  Ok ()
 
 (** [arrays::f2]:
     Source: 'src/arrays.rs', lines 273:0-273:17 *)
 let f2 (i : u32) : result unit =
-  Return ()
+  Ok ()
 
 (** [arrays::f4]:
     Source: 'src/arrays.rs', lines 282:0-282:54 *)
@@ -393,7 +393,7 @@ let f3 : result u32 =
 
 (** [arrays::SZ]
     Source: 'src/arrays.rs', lines 286:0-286:19 *)
-let sz_body : result usize = Return 32
+let sz_body : result usize = Ok 32
 let sz : usize = eval_global sz_body
 
 (** [arrays::f5]:
@@ -412,7 +412,7 @@ let ite : result unit =
   let* (_, s3) = index_mut_slice_u32_0 s2 in
   let* _ = to_slice_mut_back1 s3 in
   let* _ = to_slice_mut_back s1 in
-  Return ()
+  Ok ()
 
 (** [arrays::zero_slice]: loop 0:
     Source: 'src/arrays.rs', lines 303:0-310:1 *)
@@ -426,7 +426,7 @@ let rec zero_slice_loop
     let* i1 = usize_add i 1 in
     let* a1 = index_mut_back 0 in
     zero_slice_loop a1 i1 len
-  else Return a
+  else Ok a
 
 (** [arrays::zero_slice]:
     Source: 'src/arrays.rs', lines 303:0-303:31 *)
@@ -441,12 +441,12 @@ let rec iter_mut_slice_loop
   =
   if i < len
   then let* i1 = usize_add i 1 in iter_mut_slice_loop len i1
-  else Return ()
+  else Ok ()
 
 (** [arrays::iter_mut_slice]:
     Source: 'src/arrays.rs', lines 312:0-312:35 *)
 let iter_mut_slice (a : slice u8) : result (slice u8) =
-  let len = slice_len u8 a in let* _ = iter_mut_slice_loop len 0 in Return a
+  let len = slice_len u8 a in let* _ = iter_mut_slice_loop len 0 in Ok a
 
 (** [arrays::sum_mut_slice]: loop 0:
     Source: 'src/arrays.rs', lines 320:0-328:1 *)
@@ -461,10 +461,10 @@ let rec sum_mut_slice_loop
     let* s1 = u32_add s i2 in
     let* i3 = usize_add i 1 in
     sum_mut_slice_loop a i3 s1
-  else Return s
+  else Ok s
 
 (** [arrays::sum_mut_slice]:
     Source: 'src/arrays.rs', lines 320:0-320:42 *)
 let sum_mut_slice (a : slice u32) : result (u32 & (slice u32)) =
-  let* i = sum_mut_slice_loop a 0 0 in Return (i, a)
+  let* i = sum_mut_slice_loop a 0 0 in Ok (i, a)
 
diff --git a/tests/fstar/arrays/Primitives.fst b/tests/fstar/arrays/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/arrays/Primitives.fst
+++ b/tests/fstar/arrays/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/betree/BetreeMain.Funs.fst b/tests/fstar/betree/BetreeMain.Funs.fst
index 129e6f7e..8e64f43f 100644
--- a/tests/fstar/betree/BetreeMain.Funs.fst
+++ b/tests/fstar/betree/BetreeMain.Funs.fst
@@ -41,19 +41,19 @@ let betree_store_leaf_node
 (** [betree_main::betree::fresh_node_id]:
     Source: 'src/betree.rs', lines 55:0-55:48 *)
 let betree_fresh_node_id (counter : u64) : result (u64 & u64) =
-  let* counter1 = u64_add counter 1 in Return (counter, counter1)
+  let* counter1 = u64_add counter 1 in Ok (counter, counter1)
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::new]:
     Source: 'src/betree.rs', lines 206:4-206:20 *)
 let betree_NodeIdCounter_new : result betree_NodeIdCounter_t =
-  Return { next_node_id = 0 }
+  Ok { next_node_id = 0 }
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::fresh_id]:
     Source: 'src/betree.rs', lines 210:4-210:36 *)
 let betree_NodeIdCounter_fresh_id
   (self : betree_NodeIdCounter_t) : result (u64 & betree_NodeIdCounter_t) =
   let* i = u64_add self.next_node_id 1 in
-  Return (self.next_node_id, { next_node_id = i })
+  Ok (self.next_node_id, { next_node_id = i })
 
 (** [betree_main::betree::upsert_update]:
     Source: 'src/betree.rs', lines 234:0-234:70 *)
@@ -62,16 +62,16 @@ let betree_upsert_update
   begin match prev with
   | None ->
     begin match st with
-    | Betree_UpsertFunState_Add v -> Return v
-    | Betree_UpsertFunState_Sub _ -> Return 0
+    | Betree_UpsertFunState_Add v -> Ok v
+    | Betree_UpsertFunState_Sub _ -> Ok 0
     end
   | Some prev1 ->
     begin match st with
     | Betree_UpsertFunState_Add v ->
       let* margin = u64_sub core_u64_max prev1 in
-      if margin >= v then u64_add prev1 v else Return core_u64_max
+      if margin >= v then u64_add prev1 v else Ok core_u64_max
     | Betree_UpsertFunState_Sub v ->
-      if prev1 >= v then u64_sub prev1 v else Return 0
+      if prev1 >= v then u64_sub prev1 v else Ok 0
     end
   end
 
@@ -83,7 +83,7 @@ let rec betree_List_len
   =
   begin match self with
   | Betree_List_Cons _ tl -> let* i = betree_List_len t tl in u64_add 1 i
-  | Betree_List_Nil -> Return 0
+  | Betree_List_Nil -> Ok 0
   end
 
 (** [betree_main::betree::{betree_main::betree::List<T>#1}::split_at]:
@@ -94,14 +94,14 @@ let rec betree_List_split_at
   (decreases (betree_List_split_at_decreases t self n))
   =
   if n = 0
-  then Return (Betree_List_Nil, self)
+  then Ok (Betree_List_Nil, self)
   else
     begin match self with
     | Betree_List_Cons hd tl ->
       let* i = u64_sub n 1 in
       let* p = betree_List_split_at t tl i in
       let (ls0, ls1) = p in
-      Return (Betree_List_Cons hd ls0, ls1)
+      Ok (Betree_List_Cons hd ls0, ls1)
     | Betree_List_Nil -> Fail Failure
     end
 
@@ -110,7 +110,7 @@ let rec betree_List_split_at
 let betree_List_push_front
   (t : Type0) (self : betree_List_t t) (x : t) : result (betree_List_t t) =
   let (tl, _) = core_mem_replace (betree_List_t t) self Betree_List_Nil in
-  Return (Betree_List_Cons x tl)
+  Ok (Betree_List_Cons x tl)
 
 (** [betree_main::betree::{betree_main::betree::List<T>#1}::pop_front]:
     Source: 'src/betree.rs', lines 306:4-306:32 *)
@@ -118,7 +118,7 @@ let betree_List_pop_front
   (t : Type0) (self : betree_List_t t) : result (t & (betree_List_t t)) =
   let (ls, _) = core_mem_replace (betree_List_t t) self Betree_List_Nil in
   begin match ls with
-  | Betree_List_Cons x tl -> Return (x, tl)
+  | Betree_List_Cons x tl -> Ok (x, tl)
   | Betree_List_Nil -> Fail Failure
   end
 
@@ -126,7 +126,7 @@ let betree_List_pop_front
     Source: 'src/betree.rs', lines 318:4-318:22 *)
 let betree_List_hd (t : Type0) (self : betree_List_t t) : result t =
   begin match self with
-  | Betree_List_Cons hd _ -> Return hd
+  | Betree_List_Cons hd _ -> Ok hd
   | Betree_List_Nil -> Fail Failure
   end
 
@@ -135,8 +135,8 @@ let betree_List_hd (t : Type0) (self : betree_List_t t) : result t =
 let betree_ListPairU64T_head_has_key
   (t : Type0) (self : betree_List_t (u64 & t)) (key : u64) : result bool =
   begin match self with
-  | Betree_List_Cons hd _ -> let (i, _) = hd in Return (i = key)
-  | Betree_List_Nil -> Return false
+  | Betree_List_Cons hd _ -> let (i, _) = hd in Ok (i = key)
+  | Betree_List_Nil -> Ok false
   end
 
 (** [betree_main::betree::{betree_main::betree::List<(u64, T)>#2}::partition_at_pivot]:
@@ -150,12 +150,12 @@ let rec betree_ListPairU64T_partition_at_pivot
   | Betree_List_Cons hd tl ->
     let (i, x) = hd in
     if i >= pivot
-    then Return (Betree_List_Nil, Betree_List_Cons (i, x) tl)
+    then Ok (Betree_List_Nil, Betree_List_Cons (i, x) tl)
     else
       let* p = betree_ListPairU64T_partition_at_pivot t tl pivot in
       let (ls0, ls1) = p in
-      Return (Betree_List_Cons (i, x) ls0, ls1)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Betree_List_Nil)
+      Ok (Betree_List_Cons (i, x) ls0, ls1)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Betree_List_Nil)
   end
 
 (** [betree_main::betree::{betree_main::betree::Leaf#3}::split]:
@@ -176,7 +176,7 @@ let betree_Leaf_split
   let* (st2, _) = betree_store_leaf_node id1 content1 st1 in
   let n = Betree_Node_Leaf { id = id0; size = params.split_size } in
   let n1 = Betree_Node_Leaf { id = id1; size = params.split_size } in
-  Return (st2, ({ id = self.id; pivot = pivot; left = n; right = n1 },
+  Ok (st2, ({ id = self.id; pivot = pivot; left = n; right = n1 },
     node_id_cnt2))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_for_key]:
@@ -191,16 +191,16 @@ let rec betree_Node_lookup_first_message_for_key
   | Betree_List_Cons x next_msgs ->
     let (i, m) = x in
     if i >= key
-    then Return (Betree_List_Cons (i, m) next_msgs, Return)
+    then Ok (Betree_List_Cons (i, m) next_msgs, Ok)
     else
       let* (l, lookup_first_message_for_key_back) =
         betree_Node_lookup_first_message_for_key key next_msgs in
       let back =
         fun ret ->
           let* next_msgs1 = lookup_first_message_for_key_back ret in
-          Return (Betree_List_Cons (i, m) next_msgs1) in
-      Return (l, back)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (i, m) next_msgs1) in
+      Ok (l, back)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_in_bindings]:
@@ -214,9 +214,9 @@ let rec betree_Node_lookup_in_bindings
   | Betree_List_Cons hd tl ->
     let (i, i1) = hd in
     if i = key
-    then Return (Some i1)
-    else if i > key then Return None else betree_Node_lookup_in_bindings key tl
-  | Betree_List_Nil -> Return None
+    then Ok (Some i1)
+    else if i > key then Ok None else betree_Node_lookup_in_bindings key tl
+  | Betree_List_Nil -> Ok None
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_upserts]:
@@ -244,7 +244,7 @@ let rec betree_Node_apply_upserts
     let* msgs1 =
       betree_List_push_front (u64 & betree_Message_t) msgs (key,
         Betree_Message_Insert v) in
-    Return (st1, (v, msgs1))
+    Ok (st1, (v, msgs1))
 
 (** [betree_main::betree::{betree_main::betree::Internal#4}::lookup_in_children]:
     Source: 'src/betree.rs', lines 395:4-395:63 *)
@@ -256,10 +256,10 @@ let rec betree_Internal_lookup_in_children
   if key < self.pivot
   then
     let* (st1, (o, n)) = betree_Node_lookup self.left key st in
-    Return (st1, (o, { self with left = n }))
+    Ok (st1, (o, { self with left = n }))
   else
     let* (st1, (o, n)) = betree_Node_lookup self.right key st in
-    Return (st1, (o, { self with right = n }))
+    Ok (st1, (o, { self with right = n }))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup]:
     Source: 'src/betree.rs', lines 709:4-709:58 *)
@@ -282,19 +282,19 @@ and betree_Node_lookup
           betree_Internal_lookup_in_children node key st1 in
         let* _ =
           lookup_first_message_for_key_back (Betree_List_Cons (k, msg) l) in
-        Return (st2, (o, Betree_Node_Internal node1))
+        Ok (st2, (o, Betree_Node_Internal node1))
       else
         begin match msg with
         | Betree_Message_Insert v ->
           let* _ =
             lookup_first_message_for_key_back (Betree_List_Cons (k,
               Betree_Message_Insert v) l) in
-          Return (st1, (Some v, Betree_Node_Internal node))
+          Ok (st1, (Some v, Betree_Node_Internal node))
         | Betree_Message_Delete ->
           let* _ =
             lookup_first_message_for_key_back (Betree_List_Cons (k,
               Betree_Message_Delete) l) in
-          Return (st1, (None, Betree_Node_Internal node))
+          Ok (st1, (None, Betree_Node_Internal node))
         | Betree_Message_Upsert ufs ->
           let* (st2, (v, node1)) =
             betree_Internal_lookup_in_children node key st1 in
@@ -303,18 +303,18 @@ and betree_Node_lookup
               Betree_Message_Upsert ufs) l) v key st2 in
           let* msgs1 = lookup_first_message_for_key_back pending1 in
           let* (st4, _) = betree_store_internal_node node1.id msgs1 st3 in
-          Return (st4, (Some v1, Betree_Node_Internal node1))
+          Ok (st4, (Some v1, Betree_Node_Internal node1))
         end
     | Betree_List_Nil ->
       let* (st2, (o, node1)) = betree_Internal_lookup_in_children node key st1
         in
       let* _ = lookup_first_message_for_key_back Betree_List_Nil in
-      Return (st2, (o, Betree_Node_Internal node1))
+      Ok (st2, (o, Betree_Node_Internal node1))
     end
   | Betree_Node_Leaf node ->
     let* (st1, bindings) = betree_load_leaf_node node.id st in
     let* o = betree_Node_lookup_in_bindings key bindings in
-    Return (st1, (o, Betree_Node_Leaf node))
+    Ok (st1, (o, Betree_Node_Leaf node))
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::filter_messages_for_key]:
@@ -333,8 +333,8 @@ let rec betree_Node_filter_messages_for_key
         betree_List_pop_front (u64 & betree_Message_t) (Betree_List_Cons (k, m)
           l) in
       betree_Node_filter_messages_for_key key msgs1
-    else Return (Betree_List_Cons (k, m) l)
-  | Betree_List_Nil -> Return Betree_List_Nil
+    else Ok (Betree_List_Cons (k, m) l)
+  | Betree_List_Nil -> Ok Betree_List_Nil
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_after_key]:
@@ -355,10 +355,10 @@ let rec betree_Node_lookup_first_message_after_key
       let back =
         fun ret ->
           let* next_msgs1 = lookup_first_message_after_key_back ret in
-          Return (Betree_List_Cons (k, m) next_msgs1) in
-      Return (l, back)
-    else Return (Betree_List_Cons (k, m) next_msgs, Return)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (k, m) next_msgs1) in
+      Ok (l, back)
+    else Ok (Betree_List_Cons (k, m) next_msgs, Ok)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_to_internal]:
@@ -434,7 +434,7 @@ let rec betree_Node_apply_messages_to_internal
     let (i, m) = new_msg in
     let* msgs1 = betree_Node_apply_to_internal msgs i m in
     betree_Node_apply_messages_to_internal msgs1 new_msgs_tl
-  | Betree_List_Nil -> Return msgs
+  | Betree_List_Nil -> Ok msgs
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_mut_in_bindings]:
@@ -449,16 +449,16 @@ let rec betree_Node_lookup_mut_in_bindings
   | Betree_List_Cons hd tl ->
     let (i, i1) = hd in
     if i >= key
-    then Return (Betree_List_Cons (i, i1) tl, Return)
+    then Ok (Betree_List_Cons (i, i1) tl, Ok)
     else
       let* (l, lookup_mut_in_bindings_back) =
         betree_Node_lookup_mut_in_bindings key tl in
       let back =
         fun ret ->
           let* tl1 = lookup_mut_in_bindings_back ret in
-          Return (Betree_List_Cons (i, i1) tl1) in
-      Return (l, back)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (i, i1) tl1) in
+      Ok (l, back)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_to_leaf]:
@@ -510,7 +510,7 @@ let rec betree_Node_apply_messages_to_leaf
     let (i, m) = new_msg in
     let* bindings1 = betree_Node_apply_to_leaf bindings i m in
     betree_Node_apply_messages_to_leaf bindings1 new_msgs_tl
-  | Betree_List_Nil -> Return bindings
+  | Betree_List_Nil -> Ok bindings
   end
 
 (** [betree_main::betree::{betree_main::betree::Internal#4}::flush]:
@@ -541,14 +541,14 @@ let rec betree_Internal_flush
         betree_Node_apply_messages self.right params node_id_cnt1 msgs_right
           st1 in
       let (n1, node_id_cnt2) = p2 in
-      Return (st2, (Betree_List_Nil, ({ self with left = n; right = n1 },
+      Ok (st2, (Betree_List_Nil, ({ self with left = n; right = n1 },
         node_id_cnt2)))
-    else Return (st1, (msgs_right, ({ self with left = n }, node_id_cnt1)))
+    else Ok (st1, (msgs_right, ({ self with left = n }, node_id_cnt1)))
   else
     let* (st1, p1) =
       betree_Node_apply_messages self.right params node_id_cnt msgs_right st in
     let (n, node_id_cnt1) = p1 in
-    Return (st1, (msgs_left, ({ self with right = n }, node_id_cnt1)))
+    Ok (st1, (msgs_left, ({ self with right = n }, node_id_cnt1)))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_messages]:
     Source: 'src/betree.rs', lines 588:4-593:5 *)
@@ -571,10 +571,10 @@ and betree_Node_apply_messages
         betree_Internal_flush node params node_id_cnt content1 st1 in
       let (node1, node_id_cnt1) = p in
       let* (st3, _) = betree_store_internal_node node1.id content2 st2 in
-      Return (st3, (Betree_Node_Internal node1, node_id_cnt1))
+      Ok (st3, (Betree_Node_Internal node1, node_id_cnt1))
     else
       let* (st2, _) = betree_store_internal_node node.id content1 st1 in
-      Return (st2, (Betree_Node_Internal node, node_id_cnt))
+      Ok (st2, (Betree_Node_Internal node, node_id_cnt))
   | Betree_Node_Leaf node ->
     let* (st1, content) = betree_load_leaf_node node.id st in
     let* content1 = betree_Node_apply_messages_to_leaf content msgs in
@@ -585,10 +585,10 @@ and betree_Node_apply_messages
       let* (st2, (new_node, node_id_cnt1)) =
         betree_Leaf_split node content1 params node_id_cnt st1 in
       let* (st3, _) = betree_store_leaf_node node.id Betree_List_Nil st2 in
-      Return (st3, (Betree_Node_Internal new_node, node_id_cnt1))
+      Ok (st3, (Betree_Node_Internal new_node, node_id_cnt1))
     else
       let* (st2, _) = betree_store_leaf_node node.id content1 st1 in
-      Return (st2, (Betree_Node_Leaf { node with size = len }, node_id_cnt))
+      Ok (st2, (Betree_Node_Leaf { node with size = len }, node_id_cnt))
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply]:
@@ -603,7 +603,7 @@ let betree_Node_apply
     betree_Node_apply_messages self params node_id_cnt (Betree_List_Cons (key,
       new_msg) Betree_List_Nil) st in
   let (self1, node_id_cnt1) = p in
-  Return (st1, (self1, node_id_cnt1))
+  Ok (st1, (self1, node_id_cnt1))
 
 (** [betree_main::betree::{betree_main::betree::BeTree#6}::new]:
     Source: 'src/betree.rs', lines 849:4-849:60 *)
@@ -614,7 +614,7 @@ let betree_BeTree_new
   let* node_id_cnt = betree_NodeIdCounter_new in
   let* (id, node_id_cnt1) = betree_NodeIdCounter_fresh_id node_id_cnt in
   let* (st1, _) = betree_store_leaf_node id Betree_List_Nil st in
-  Return (st1,
+  Ok (st1,
     {
       params = { min_flush_size = min_flush_size; split_size = split_size };
       node_id_cnt = node_id_cnt1;
@@ -630,7 +630,7 @@ let betree_BeTree_apply
   let* (st1, p) =
     betree_Node_apply self.root self.params self.node_id_cnt key msg st in
   let (n, nic) = p in
-  Return (st1, { self with node_id_cnt = nic; root = n })
+  Ok (st1, { self with node_id_cnt = nic; root = n })
 
 (** [betree_main::betree::{betree_main::betree::BeTree#6}::insert]:
     Source: 'src/betree.rs', lines 874:4-874:52 *)
@@ -664,13 +664,13 @@ let betree_BeTree_lookup
   result (state & ((option u64) & betree_BeTree_t))
   =
   let* (st1, (o, n)) = betree_Node_lookup self.root key st in
-  Return (st1, (o, { self with root = n }))
+  Ok (st1, (o, { self with root = n }))
 
 (** [betree_main::main]:
     Source: 'src/betree_main.rs', lines 5:0-5:9 *)
 let main : result unit =
-  Return ()
+  Ok ()
 
 (** Unit test for [betree_main::main] *)
-let _ = assert_norm (main = Return ())
+let _ = assert_norm (main = Ok ())
 
diff --git a/tests/fstar/betree/Primitives.fst b/tests/fstar/betree/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/betree/Primitives.fst
+++ b/tests/fstar/betree/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/betree_back_stateful/BetreeMain.Funs.fst b/tests/fstar/betree_back_stateful/BetreeMain.Funs.fst
index 129e6f7e..8e64f43f 100644
--- a/tests/fstar/betree_back_stateful/BetreeMain.Funs.fst
+++ b/tests/fstar/betree_back_stateful/BetreeMain.Funs.fst
@@ -41,19 +41,19 @@ let betree_store_leaf_node
 (** [betree_main::betree::fresh_node_id]:
     Source: 'src/betree.rs', lines 55:0-55:48 *)
 let betree_fresh_node_id (counter : u64) : result (u64 & u64) =
-  let* counter1 = u64_add counter 1 in Return (counter, counter1)
+  let* counter1 = u64_add counter 1 in Ok (counter, counter1)
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::new]:
     Source: 'src/betree.rs', lines 206:4-206:20 *)
 let betree_NodeIdCounter_new : result betree_NodeIdCounter_t =
-  Return { next_node_id = 0 }
+  Ok { next_node_id = 0 }
 
 (** [betree_main::betree::{betree_main::betree::NodeIdCounter}::fresh_id]:
     Source: 'src/betree.rs', lines 210:4-210:36 *)
 let betree_NodeIdCounter_fresh_id
   (self : betree_NodeIdCounter_t) : result (u64 & betree_NodeIdCounter_t) =
   let* i = u64_add self.next_node_id 1 in
-  Return (self.next_node_id, { next_node_id = i })
+  Ok (self.next_node_id, { next_node_id = i })
 
 (** [betree_main::betree::upsert_update]:
     Source: 'src/betree.rs', lines 234:0-234:70 *)
@@ -62,16 +62,16 @@ let betree_upsert_update
   begin match prev with
   | None ->
     begin match st with
-    | Betree_UpsertFunState_Add v -> Return v
-    | Betree_UpsertFunState_Sub _ -> Return 0
+    | Betree_UpsertFunState_Add v -> Ok v
+    | Betree_UpsertFunState_Sub _ -> Ok 0
     end
   | Some prev1 ->
     begin match st with
     | Betree_UpsertFunState_Add v ->
       let* margin = u64_sub core_u64_max prev1 in
-      if margin >= v then u64_add prev1 v else Return core_u64_max
+      if margin >= v then u64_add prev1 v else Ok core_u64_max
     | Betree_UpsertFunState_Sub v ->
-      if prev1 >= v then u64_sub prev1 v else Return 0
+      if prev1 >= v then u64_sub prev1 v else Ok 0
     end
   end
 
@@ -83,7 +83,7 @@ let rec betree_List_len
   =
   begin match self with
   | Betree_List_Cons _ tl -> let* i = betree_List_len t tl in u64_add 1 i
-  | Betree_List_Nil -> Return 0
+  | Betree_List_Nil -> Ok 0
   end
 
 (** [betree_main::betree::{betree_main::betree::List<T>#1}::split_at]:
@@ -94,14 +94,14 @@ let rec betree_List_split_at
   (decreases (betree_List_split_at_decreases t self n))
   =
   if n = 0
-  then Return (Betree_List_Nil, self)
+  then Ok (Betree_List_Nil, self)
   else
     begin match self with
     | Betree_List_Cons hd tl ->
       let* i = u64_sub n 1 in
       let* p = betree_List_split_at t tl i in
       let (ls0, ls1) = p in
-      Return (Betree_List_Cons hd ls0, ls1)
+      Ok (Betree_List_Cons hd ls0, ls1)
     | Betree_List_Nil -> Fail Failure
     end
 
@@ -110,7 +110,7 @@ let rec betree_List_split_at
 let betree_List_push_front
   (t : Type0) (self : betree_List_t t) (x : t) : result (betree_List_t t) =
   let (tl, _) = core_mem_replace (betree_List_t t) self Betree_List_Nil in
-  Return (Betree_List_Cons x tl)
+  Ok (Betree_List_Cons x tl)
 
 (** [betree_main::betree::{betree_main::betree::List<T>#1}::pop_front]:
     Source: 'src/betree.rs', lines 306:4-306:32 *)
@@ -118,7 +118,7 @@ let betree_List_pop_front
   (t : Type0) (self : betree_List_t t) : result (t & (betree_List_t t)) =
   let (ls, _) = core_mem_replace (betree_List_t t) self Betree_List_Nil in
   begin match ls with
-  | Betree_List_Cons x tl -> Return (x, tl)
+  | Betree_List_Cons x tl -> Ok (x, tl)
   | Betree_List_Nil -> Fail Failure
   end
 
@@ -126,7 +126,7 @@ let betree_List_pop_front
     Source: 'src/betree.rs', lines 318:4-318:22 *)
 let betree_List_hd (t : Type0) (self : betree_List_t t) : result t =
   begin match self with
-  | Betree_List_Cons hd _ -> Return hd
+  | Betree_List_Cons hd _ -> Ok hd
   | Betree_List_Nil -> Fail Failure
   end
 
@@ -135,8 +135,8 @@ let betree_List_hd (t : Type0) (self : betree_List_t t) : result t =
 let betree_ListPairU64T_head_has_key
   (t : Type0) (self : betree_List_t (u64 & t)) (key : u64) : result bool =
   begin match self with
-  | Betree_List_Cons hd _ -> let (i, _) = hd in Return (i = key)
-  | Betree_List_Nil -> Return false
+  | Betree_List_Cons hd _ -> let (i, _) = hd in Ok (i = key)
+  | Betree_List_Nil -> Ok false
   end
 
 (** [betree_main::betree::{betree_main::betree::List<(u64, T)>#2}::partition_at_pivot]:
@@ -150,12 +150,12 @@ let rec betree_ListPairU64T_partition_at_pivot
   | Betree_List_Cons hd tl ->
     let (i, x) = hd in
     if i >= pivot
-    then Return (Betree_List_Nil, Betree_List_Cons (i, x) tl)
+    then Ok (Betree_List_Nil, Betree_List_Cons (i, x) tl)
     else
       let* p = betree_ListPairU64T_partition_at_pivot t tl pivot in
       let (ls0, ls1) = p in
-      Return (Betree_List_Cons (i, x) ls0, ls1)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Betree_List_Nil)
+      Ok (Betree_List_Cons (i, x) ls0, ls1)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Betree_List_Nil)
   end
 
 (** [betree_main::betree::{betree_main::betree::Leaf#3}::split]:
@@ -176,7 +176,7 @@ let betree_Leaf_split
   let* (st2, _) = betree_store_leaf_node id1 content1 st1 in
   let n = Betree_Node_Leaf { id = id0; size = params.split_size } in
   let n1 = Betree_Node_Leaf { id = id1; size = params.split_size } in
-  Return (st2, ({ id = self.id; pivot = pivot; left = n; right = n1 },
+  Ok (st2, ({ id = self.id; pivot = pivot; left = n; right = n1 },
     node_id_cnt2))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_for_key]:
@@ -191,16 +191,16 @@ let rec betree_Node_lookup_first_message_for_key
   | Betree_List_Cons x next_msgs ->
     let (i, m) = x in
     if i >= key
-    then Return (Betree_List_Cons (i, m) next_msgs, Return)
+    then Ok (Betree_List_Cons (i, m) next_msgs, Ok)
     else
       let* (l, lookup_first_message_for_key_back) =
         betree_Node_lookup_first_message_for_key key next_msgs in
       let back =
         fun ret ->
           let* next_msgs1 = lookup_first_message_for_key_back ret in
-          Return (Betree_List_Cons (i, m) next_msgs1) in
-      Return (l, back)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (i, m) next_msgs1) in
+      Ok (l, back)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_in_bindings]:
@@ -214,9 +214,9 @@ let rec betree_Node_lookup_in_bindings
   | Betree_List_Cons hd tl ->
     let (i, i1) = hd in
     if i = key
-    then Return (Some i1)
-    else if i > key then Return None else betree_Node_lookup_in_bindings key tl
-  | Betree_List_Nil -> Return None
+    then Ok (Some i1)
+    else if i > key then Ok None else betree_Node_lookup_in_bindings key tl
+  | Betree_List_Nil -> Ok None
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_upserts]:
@@ -244,7 +244,7 @@ let rec betree_Node_apply_upserts
     let* msgs1 =
       betree_List_push_front (u64 & betree_Message_t) msgs (key,
         Betree_Message_Insert v) in
-    Return (st1, (v, msgs1))
+    Ok (st1, (v, msgs1))
 
 (** [betree_main::betree::{betree_main::betree::Internal#4}::lookup_in_children]:
     Source: 'src/betree.rs', lines 395:4-395:63 *)
@@ -256,10 +256,10 @@ let rec betree_Internal_lookup_in_children
   if key < self.pivot
   then
     let* (st1, (o, n)) = betree_Node_lookup self.left key st in
-    Return (st1, (o, { self with left = n }))
+    Ok (st1, (o, { self with left = n }))
   else
     let* (st1, (o, n)) = betree_Node_lookup self.right key st in
-    Return (st1, (o, { self with right = n }))
+    Ok (st1, (o, { self with right = n }))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup]:
     Source: 'src/betree.rs', lines 709:4-709:58 *)
@@ -282,19 +282,19 @@ and betree_Node_lookup
           betree_Internal_lookup_in_children node key st1 in
         let* _ =
           lookup_first_message_for_key_back (Betree_List_Cons (k, msg) l) in
-        Return (st2, (o, Betree_Node_Internal node1))
+        Ok (st2, (o, Betree_Node_Internal node1))
       else
         begin match msg with
         | Betree_Message_Insert v ->
           let* _ =
             lookup_first_message_for_key_back (Betree_List_Cons (k,
               Betree_Message_Insert v) l) in
-          Return (st1, (Some v, Betree_Node_Internal node))
+          Ok (st1, (Some v, Betree_Node_Internal node))
         | Betree_Message_Delete ->
           let* _ =
             lookup_first_message_for_key_back (Betree_List_Cons (k,
               Betree_Message_Delete) l) in
-          Return (st1, (None, Betree_Node_Internal node))
+          Ok (st1, (None, Betree_Node_Internal node))
         | Betree_Message_Upsert ufs ->
           let* (st2, (v, node1)) =
             betree_Internal_lookup_in_children node key st1 in
@@ -303,18 +303,18 @@ and betree_Node_lookup
               Betree_Message_Upsert ufs) l) v key st2 in
           let* msgs1 = lookup_first_message_for_key_back pending1 in
           let* (st4, _) = betree_store_internal_node node1.id msgs1 st3 in
-          Return (st4, (Some v1, Betree_Node_Internal node1))
+          Ok (st4, (Some v1, Betree_Node_Internal node1))
         end
     | Betree_List_Nil ->
       let* (st2, (o, node1)) = betree_Internal_lookup_in_children node key st1
         in
       let* _ = lookup_first_message_for_key_back Betree_List_Nil in
-      Return (st2, (o, Betree_Node_Internal node1))
+      Ok (st2, (o, Betree_Node_Internal node1))
     end
   | Betree_Node_Leaf node ->
     let* (st1, bindings) = betree_load_leaf_node node.id st in
     let* o = betree_Node_lookup_in_bindings key bindings in
-    Return (st1, (o, Betree_Node_Leaf node))
+    Ok (st1, (o, Betree_Node_Leaf node))
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::filter_messages_for_key]:
@@ -333,8 +333,8 @@ let rec betree_Node_filter_messages_for_key
         betree_List_pop_front (u64 & betree_Message_t) (Betree_List_Cons (k, m)
           l) in
       betree_Node_filter_messages_for_key key msgs1
-    else Return (Betree_List_Cons (k, m) l)
-  | Betree_List_Nil -> Return Betree_List_Nil
+    else Ok (Betree_List_Cons (k, m) l)
+  | Betree_List_Nil -> Ok Betree_List_Nil
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_after_key]:
@@ -355,10 +355,10 @@ let rec betree_Node_lookup_first_message_after_key
       let back =
         fun ret ->
           let* next_msgs1 = lookup_first_message_after_key_back ret in
-          Return (Betree_List_Cons (k, m) next_msgs1) in
-      Return (l, back)
-    else Return (Betree_List_Cons (k, m) next_msgs, Return)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (k, m) next_msgs1) in
+      Ok (l, back)
+    else Ok (Betree_List_Cons (k, m) next_msgs, Ok)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_to_internal]:
@@ -434,7 +434,7 @@ let rec betree_Node_apply_messages_to_internal
     let (i, m) = new_msg in
     let* msgs1 = betree_Node_apply_to_internal msgs i m in
     betree_Node_apply_messages_to_internal msgs1 new_msgs_tl
-  | Betree_List_Nil -> Return msgs
+  | Betree_List_Nil -> Ok msgs
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::lookup_mut_in_bindings]:
@@ -449,16 +449,16 @@ let rec betree_Node_lookup_mut_in_bindings
   | Betree_List_Cons hd tl ->
     let (i, i1) = hd in
     if i >= key
-    then Return (Betree_List_Cons (i, i1) tl, Return)
+    then Ok (Betree_List_Cons (i, i1) tl, Ok)
     else
       let* (l, lookup_mut_in_bindings_back) =
         betree_Node_lookup_mut_in_bindings key tl in
       let back =
         fun ret ->
           let* tl1 = lookup_mut_in_bindings_back ret in
-          Return (Betree_List_Cons (i, i1) tl1) in
-      Return (l, back)
-  | Betree_List_Nil -> Return (Betree_List_Nil, Return)
+          Ok (Betree_List_Cons (i, i1) tl1) in
+      Ok (l, back)
+  | Betree_List_Nil -> Ok (Betree_List_Nil, Ok)
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_to_leaf]:
@@ -510,7 +510,7 @@ let rec betree_Node_apply_messages_to_leaf
     let (i, m) = new_msg in
     let* bindings1 = betree_Node_apply_to_leaf bindings i m in
     betree_Node_apply_messages_to_leaf bindings1 new_msgs_tl
-  | Betree_List_Nil -> Return bindings
+  | Betree_List_Nil -> Ok bindings
   end
 
 (** [betree_main::betree::{betree_main::betree::Internal#4}::flush]:
@@ -541,14 +541,14 @@ let rec betree_Internal_flush
         betree_Node_apply_messages self.right params node_id_cnt1 msgs_right
           st1 in
       let (n1, node_id_cnt2) = p2 in
-      Return (st2, (Betree_List_Nil, ({ self with left = n; right = n1 },
+      Ok (st2, (Betree_List_Nil, ({ self with left = n; right = n1 },
         node_id_cnt2)))
-    else Return (st1, (msgs_right, ({ self with left = n }, node_id_cnt1)))
+    else Ok (st1, (msgs_right, ({ self with left = n }, node_id_cnt1)))
   else
     let* (st1, p1) =
       betree_Node_apply_messages self.right params node_id_cnt msgs_right st in
     let (n, node_id_cnt1) = p1 in
-    Return (st1, (msgs_left, ({ self with right = n }, node_id_cnt1)))
+    Ok (st1, (msgs_left, ({ self with right = n }, node_id_cnt1)))
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply_messages]:
     Source: 'src/betree.rs', lines 588:4-593:5 *)
@@ -571,10 +571,10 @@ and betree_Node_apply_messages
         betree_Internal_flush node params node_id_cnt content1 st1 in
       let (node1, node_id_cnt1) = p in
       let* (st3, _) = betree_store_internal_node node1.id content2 st2 in
-      Return (st3, (Betree_Node_Internal node1, node_id_cnt1))
+      Ok (st3, (Betree_Node_Internal node1, node_id_cnt1))
     else
       let* (st2, _) = betree_store_internal_node node.id content1 st1 in
-      Return (st2, (Betree_Node_Internal node, node_id_cnt))
+      Ok (st2, (Betree_Node_Internal node, node_id_cnt))
   | Betree_Node_Leaf node ->
     let* (st1, content) = betree_load_leaf_node node.id st in
     let* content1 = betree_Node_apply_messages_to_leaf content msgs in
@@ -585,10 +585,10 @@ and betree_Node_apply_messages
       let* (st2, (new_node, node_id_cnt1)) =
         betree_Leaf_split node content1 params node_id_cnt st1 in
       let* (st3, _) = betree_store_leaf_node node.id Betree_List_Nil st2 in
-      Return (st3, (Betree_Node_Internal new_node, node_id_cnt1))
+      Ok (st3, (Betree_Node_Internal new_node, node_id_cnt1))
     else
       let* (st2, _) = betree_store_leaf_node node.id content1 st1 in
-      Return (st2, (Betree_Node_Leaf { node with size = len }, node_id_cnt))
+      Ok (st2, (Betree_Node_Leaf { node with size = len }, node_id_cnt))
   end
 
 (** [betree_main::betree::{betree_main::betree::Node#5}::apply]:
@@ -603,7 +603,7 @@ let betree_Node_apply
     betree_Node_apply_messages self params node_id_cnt (Betree_List_Cons (key,
       new_msg) Betree_List_Nil) st in
   let (self1, node_id_cnt1) = p in
-  Return (st1, (self1, node_id_cnt1))
+  Ok (st1, (self1, node_id_cnt1))
 
 (** [betree_main::betree::{betree_main::betree::BeTree#6}::new]:
     Source: 'src/betree.rs', lines 849:4-849:60 *)
@@ -614,7 +614,7 @@ let betree_BeTree_new
   let* node_id_cnt = betree_NodeIdCounter_new in
   let* (id, node_id_cnt1) = betree_NodeIdCounter_fresh_id node_id_cnt in
   let* (st1, _) = betree_store_leaf_node id Betree_List_Nil st in
-  Return (st1,
+  Ok (st1,
     {
       params = { min_flush_size = min_flush_size; split_size = split_size };
       node_id_cnt = node_id_cnt1;
@@ -630,7 +630,7 @@ let betree_BeTree_apply
   let* (st1, p) =
     betree_Node_apply self.root self.params self.node_id_cnt key msg st in
   let (n, nic) = p in
-  Return (st1, { self with node_id_cnt = nic; root = n })
+  Ok (st1, { self with node_id_cnt = nic; root = n })
 
 (** [betree_main::betree::{betree_main::betree::BeTree#6}::insert]:
     Source: 'src/betree.rs', lines 874:4-874:52 *)
@@ -664,13 +664,13 @@ let betree_BeTree_lookup
   result (state & ((option u64) & betree_BeTree_t))
   =
   let* (st1, (o, n)) = betree_Node_lookup self.root key st in
-  Return (st1, (o, { self with root = n }))
+  Ok (st1, (o, { self with root = n }))
 
 (** [betree_main::main]:
     Source: 'src/betree_main.rs', lines 5:0-5:9 *)
 let main : result unit =
-  Return ()
+  Ok ()
 
 (** Unit test for [betree_main::main] *)
-let _ = assert_norm (main = Return ())
+let _ = assert_norm (main = Ok ())
 
diff --git a/tests/fstar/betree_back_stateful/Primitives.fst b/tests/fstar/betree_back_stateful/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/betree_back_stateful/Primitives.fst
+++ b/tests/fstar/betree_back_stateful/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/demo/Demo.fst b/tests/fstar/demo/Demo.fst
index 9c59ab9b..b210662f 100644
--- a/tests/fstar/demo/Demo.fst
+++ b/tests/fstar/demo/Demo.fst
@@ -10,8 +10,8 @@ open Primitives
 let choose
   (t : Type0) (b : bool) (x : t) (y : t) : result (t & (t -> result (t & t))) =
   if b
-  then let back = fun ret -> Return (ret, y) in Return (x, back)
-  else let back = fun ret -> Return (x, ret) in Return (y, back)
+  then let back = fun ret -> Ok (ret, y) in Ok (x, back)
+  else let back = fun ret -> Ok (x, ret) in Ok (y, back)
 
 (** [demo::mul2_add1]:
     Source: 'src/demo.rs', lines 13:0-13:31 *)
@@ -31,7 +31,7 @@ let incr (x : u32) : result u32 =
 (** [demo::use_incr]:
     Source: 'src/demo.rs', lines 25:0-25:17 *)
 let use_incr : result unit =
-  let* x = incr 0 in let* x1 = incr x in let* _ = incr x1 in Return ()
+  let* x = incr 0 in let* x1 = incr x in let* _ = incr x1 in Ok ()
 
 (** [demo::CList]
     Source: 'src/demo.rs', lines 34:0-34:17 *)
@@ -48,7 +48,7 @@ let rec list_nth (t : Type0) (n : nat) (l : cList_t t) (i : u32) : result t =
     let n1 = decrease n in
     begin match l with
     | CList_CCons x tl ->
-      if i = 0 then Return x else let* i1 = u32_sub i 1 in list_nth t n1 tl i1
+      if i = 0 then Ok x else let* i1 = u32_sub i 1 in list_nth t n1 tl i1
     | CList_CNil -> Fail Failure
     end
 
@@ -65,15 +65,14 @@ let rec list_nth_mut
     begin match l with
     | CList_CCons x tl ->
       if i = 0
-      then
-        let back = fun ret -> Return (CList_CCons ret tl) in Return (x, back)
+      then let back = fun ret -> Ok (CList_CCons ret tl) in Ok (x, back)
       else
         let* i1 = u32_sub i 1 in
         let* (x1, list_nth_mut_back) = list_nth_mut t n1 tl i1 in
         let back =
-          fun ret ->
-            let* tl1 = list_nth_mut_back ret in Return (CList_CCons x tl1) in
-        Return (x1, back)
+          fun ret -> let* tl1 = list_nth_mut_back ret in Ok (CList_CCons x tl1)
+          in
+        Ok (x1, back)
     | CList_CNil -> Fail Failure
     end
 
@@ -90,14 +89,12 @@ let rec list_nth_mut1_loop
     begin match l with
     | CList_CCons x tl ->
       if i = 0
-      then
-        let back = fun ret -> Return (CList_CCons ret tl) in Return (x, back)
+      then let back = fun ret -> Ok (CList_CCons ret tl) in Ok (x, back)
       else
         let* i1 = u32_sub i 1 in
         let* (x1, back) = list_nth_mut1_loop t n1 tl i1 in
-        let back1 =
-          fun ret -> let* tl1 = back ret in Return (CList_CCons x tl1) in
-        Return (x1, back1)
+        let back1 = fun ret -> let* tl1 = back ret in Ok (CList_CCons x tl1) in
+        Ok (x1, back1)
     | CList_CNil -> Fail Failure
     end
 
@@ -117,7 +114,7 @@ let rec i32_id (n : nat) (i : i32) : result i32 =
   else
     let n1 = decrease n in
     if i = 0
-    then Return 0
+    then Ok 0
     else let* i1 = i32_sub i 1 in let* i2 = i32_id n1 i1 in i32_add i2 1
 
 (** [demo::list_tail]:
@@ -134,10 +131,9 @@ let rec list_tail
     | CList_CCons x tl ->
       let* (c, list_tail_back) = list_tail t n1 tl in
       let back =
-        fun ret -> let* tl1 = list_tail_back ret in Return (CList_CCons x tl1)
-        in
-      Return (c, back)
-    | CList_CNil -> Return (CList_CNil, Return)
+        fun ret -> let* tl1 = list_tail_back ret in Ok (CList_CCons x tl1) in
+      Ok (c, back)
+    | CList_CNil -> Ok (CList_CNil, Ok)
     end
 
 (** Trait declaration: [demo::Counter]
@@ -147,7 +143,7 @@ noeq type counter_t (self : Type0) = { incr : self -> result (usize & self); }
 (** [demo::{(demo::Counter for usize)}::incr]:
     Source: 'src/demo.rs', lines 102:4-102:31 *)
 let counterUsize_incr (self : usize) : result (usize & usize) =
-  let* self1 = usize_add self 1 in Return (self, self1)
+  let* self1 = usize_add self 1 in Ok (self, self1)
 
 (** Trait implementation: [demo::{(demo::Counter for usize)}]
     Source: 'src/demo.rs', lines 101:0-101:22 *)
diff --git a/tests/fstar/demo/Primitives.fst b/tests/fstar/demo/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/demo/Primitives.fst
+++ b/tests/fstar/demo/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/hashmap/Hashmap.Funs.fst b/tests/fstar/hashmap/Hashmap.Funs.fst
index d897933a..2be587af 100644
--- a/tests/fstar/hashmap/Hashmap.Funs.fst
+++ b/tests/fstar/hashmap/Hashmap.Funs.fst
@@ -10,7 +10,7 @@ include Hashmap.Clauses
 (** [hashmap::hash_key]:
     Source: 'src/hashmap.rs', lines 27:0-27:32 *)
 let hash_key (k : usize) : result usize =
-  Return k
+  Ok k
 
 (** [hashmap::{hashmap::HashMap<T>}::allocate_slots]: loop 0:
     Source: 'src/hashmap.rs', lines 50:4-56:5 *)
@@ -24,7 +24,7 @@ let rec hashMap_allocate_slots_loop
     let* slots1 = alloc_vec_Vec_push (list_t t) slots List_Nil in
     let* n1 = usize_sub n 1 in
     hashMap_allocate_slots_loop t slots1 n1
-  else Return slots
+  else Ok slots
 
 (** [hashmap::{hashmap::HashMap<T>}::allocate_slots]:
     Source: 'src/hashmap.rs', lines 50:4-50:76 *)
@@ -45,7 +45,7 @@ let hashMap_new_with_capacity
     in
   let* i = usize_mul capacity max_load_dividend in
   let* i1 = usize_div i max_load_divisor in
-  Return
+  Ok
     {
       num_entries = 0;
       max_load_factor = (max_load_dividend, max_load_divisor);
@@ -74,18 +74,18 @@ let rec hashMap_clear_loop
     let* i2 = usize_add i 1 in
     let* slots1 = index_mut_back List_Nil in
     hashMap_clear_loop t slots1 i2
-  else Return slots
+  else Ok slots
 
 (** [hashmap::{hashmap::HashMap<T>}::clear]:
     Source: 'src/hashmap.rs', lines 80:4-80:27 *)
 let hashMap_clear (t : Type0) (self : hashMap_t t) : result (hashMap_t t) =
   let* hm = hashMap_clear_loop t self.slots 0 in
-  Return { self with num_entries = 0; slots = hm }
+  Ok { self with num_entries = 0; slots = hm }
 
 (** [hashmap::{hashmap::HashMap<T>}::len]:
     Source: 'src/hashmap.rs', lines 90:4-90:30 *)
 let hashMap_len (t : Type0) (self : hashMap_t t) : result usize =
-  Return self.num_entries
+  Ok self.num_entries
 
 (** [hashmap::{hashmap::HashMap<T>}::insert_in_list]: loop 0:
     Source: 'src/hashmap.rs', lines 97:4-114:5 *)
@@ -97,11 +97,11 @@ let rec hashMap_insert_in_list_loop
   begin match ls with
   | List_Cons ckey cvalue tl ->
     if ckey = key
-    then Return (false, List_Cons ckey value tl)
+    then Ok (false, List_Cons ckey value tl)
     else
       let* (b, tl1) = hashMap_insert_in_list_loop t key value tl in
-      Return (b, List_Cons ckey cvalue tl1)
-  | List_Nil -> Return (true, List_Cons key value List_Nil)
+      Ok (b, List_Cons ckey cvalue tl1)
+  | List_Nil -> Ok (true, List_Cons key value List_Nil)
   end
 
 (** [hashmap::{hashmap::HashMap<T>}::insert_in_list]:
@@ -130,8 +130,8 @@ let hashMap_insert_no_resize
   then
     let* i1 = usize_add self.num_entries 1 in
     let* v = index_mut_back l1 in
-    Return { self with num_entries = i1; slots = v }
-  else let* v = index_mut_back l1 in Return { self with slots = v }
+    Ok { self with num_entries = i1; slots = v }
+  else let* v = index_mut_back l1 in Ok { self with slots = v }
 
 (** [hashmap::{hashmap::HashMap<T>}::move_elements_from_list]: loop 0:
     Source: 'src/hashmap.rs', lines 183:4-196:5 *)
@@ -144,7 +144,7 @@ let rec hashMap_move_elements_from_list_loop
   | List_Cons k v tl ->
     let* ntable1 = hashMap_insert_no_resize t ntable k v in
     hashMap_move_elements_from_list_loop t ntable1 tl
-  | List_Nil -> Return ntable
+  | List_Nil -> Ok ntable
   end
 
 (** [hashmap::{hashmap::HashMap<T>}::move_elements_from_list]:
@@ -172,7 +172,7 @@ let rec hashMap_move_elements_loop
     let* i2 = usize_add i 1 in
     let* slots1 = index_mut_back l1 in
     hashMap_move_elements_loop t ntable1 slots1 i2
-  else Return (ntable, slots)
+  else Ok (ntable, slots)
 
 (** [hashmap::{hashmap::HashMap<T>}::move_elements]:
     Source: 'src/hashmap.rs', lines 171:4-171:95 *)
@@ -198,10 +198,10 @@ let hashMap_try_resize
     let* ntable = hashMap_new_with_capacity t i3 i i1 in
     let* p = hashMap_move_elements t ntable self.slots 0 in
     let (ntable1, _) = p in
-    Return
+    Ok
       { ntable1 with num_entries = self.num_entries; max_load_factor = (i, i1)
       }
-  else Return { self with max_load_factor = (i, i1) }
+  else Ok { self with max_load_factor = (i, i1) }
 
 (** [hashmap::{hashmap::HashMap<T>}::insert]:
     Source: 'src/hashmap.rs', lines 129:4-129:48 *)
@@ -211,7 +211,7 @@ let hashMap_insert
   =
   let* self1 = hashMap_insert_no_resize t self key value in
   let* i = hashMap_len t self1 in
-  if i > self1.max_load then hashMap_try_resize t self1 else Return self1
+  if i > self1.max_load then hashMap_try_resize t self1 else Ok self1
 
 (** [hashmap::{hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
     Source: 'src/hashmap.rs', lines 206:4-219:5 *)
@@ -222,10 +222,8 @@ let rec hashMap_contains_key_in_list_loop
   =
   begin match ls with
   | List_Cons ckey _ tl ->
-    if ckey = key
-    then Return true
-    else hashMap_contains_key_in_list_loop t key tl
-  | List_Nil -> Return false
+    if ckey = key then Ok true else hashMap_contains_key_in_list_loop t key tl
+  | List_Nil -> Ok false
   end
 
 (** [hashmap::{hashmap::HashMap<T>}::contains_key_in_list]:
@@ -255,7 +253,7 @@ let rec hashMap_get_in_list_loop
   =
   begin match ls with
   | List_Cons ckey cvalue tl ->
-    if ckey = key then Return cvalue else hashMap_get_in_list_loop t key tl
+    if ckey = key then Ok cvalue else hashMap_get_in_list_loop t key tl
   | List_Nil -> Fail Failure
   end
 
@@ -286,14 +284,12 @@ let rec hashMap_get_mut_in_list_loop
   begin match ls with
   | List_Cons ckey cvalue tl ->
     if ckey = key
-    then
-      let back = fun ret -> Return (List_Cons ckey ret tl) in
-      Return (cvalue, back)
+    then let back = fun ret -> Ok (List_Cons ckey ret tl) in Ok (cvalue, back)
     else
       let* (x, back) = hashMap_get_mut_in_list_loop t tl key in
       let back1 =
-        fun ret -> let* tl1 = back ret in Return (List_Cons ckey cvalue tl1) in
-      Return (x, back1)
+        fun ret -> let* tl1 = back ret in Ok (List_Cons ckey cvalue tl1) in
+      Ok (x, back1)
   | List_Nil -> Fail Failure
   end
 
@@ -323,8 +319,8 @@ let hashMap_get_mut
     fun ret ->
       let* l1 = get_mut_in_list_back ret in
       let* v = index_mut_back l1 in
-      Return { self with slots = v } in
-  Return (x, back)
+      Ok { self with slots = v } in
+  Ok (x, back)
 
 (** [hashmap::{hashmap::HashMap<T>}::remove_from_list]: loop 0:
     Source: 'src/hashmap.rs', lines 265:4-291:5 *)
@@ -340,13 +336,13 @@ let rec hashMap_remove_from_list_loop
       let (mv_ls, _) =
         core_mem_replace (list_t t) (List_Cons ckey x tl) List_Nil in
       begin match mv_ls with
-      | List_Cons _ cvalue tl1 -> Return (Some cvalue, tl1)
+      | List_Cons _ cvalue tl1 -> Ok (Some cvalue, tl1)
       | List_Nil -> Fail Failure
       end
     else
       let* (o, tl1) = hashMap_remove_from_list_loop t key tl in
-      Return (o, List_Cons ckey x tl1)
-  | List_Nil -> Return (None, List_Nil)
+      Ok (o, List_Cons ckey x tl1)
+  | List_Nil -> Ok (None, List_Nil)
   end
 
 (** [hashmap::{hashmap::HashMap<T>}::remove_from_list]:
@@ -372,12 +368,11 @@ let hashMap_remove
       hash_mod in
   let* (x, l1) = hashMap_remove_from_list t key l in
   begin match x with
-  | None ->
-    let* v = index_mut_back l1 in Return (None, { self with slots = v })
+  | None -> let* v = index_mut_back l1 in Ok (None, { self with slots = v })
   | Some x1 ->
     let* i1 = usize_sub self.num_entries 1 in
     let* v = index_mut_back l1 in
-    Return (Some x1, { self with num_entries = i1; slots = v })
+    Ok (Some x1, { self with num_entries = i1; slots = v })
   end
 
 (** [hashmap::test1]:
@@ -414,6 +409,6 @@ let test1 : result unit =
             then Fail Failure
             else
               let* i4 = hashMap_get u64 hm6 1056 in
-              if not (i4 = 256) then Fail Failure else Return ()
+              if not (i4 = 256) then Fail Failure else Ok ()
       end
 
diff --git a/tests/fstar/hashmap/Primitives.fst b/tests/fstar/hashmap/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/hashmap/Primitives.fst
+++ b/tests/fstar/hashmap/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/hashmap_on_disk/HashmapMain.Funs.fst b/tests/fstar/hashmap_on_disk/HashmapMain.Funs.fst
index e0005c81..ff86e087 100644
--- a/tests/fstar/hashmap_on_disk/HashmapMain.Funs.fst
+++ b/tests/fstar/hashmap_on_disk/HashmapMain.Funs.fst
@@ -11,7 +11,7 @@ include HashmapMain.Clauses
 (** [hashmap_main::hashmap::hash_key]:
     Source: 'src/hashmap.rs', lines 27:0-27:32 *)
 let hashmap_hash_key (k : usize) : result usize =
-  Return k
+  Ok k
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::allocate_slots]: loop 0:
     Source: 'src/hashmap.rs', lines 50:4-56:5 *)
@@ -26,7 +26,7 @@ let rec hashmap_HashMap_allocate_slots_loop
       in
     let* n1 = usize_sub n 1 in
     hashmap_HashMap_allocate_slots_loop t slots1 n1
-  else Return slots
+  else Ok slots
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::allocate_slots]:
     Source: 'src/hashmap.rs', lines 50:4-50:76 *)
@@ -48,7 +48,7 @@ let hashmap_HashMap_new_with_capacity
       capacity in
   let* i = usize_mul capacity max_load_dividend in
   let* i1 = usize_div i max_load_divisor in
-  Return
+  Ok
     {
       num_entries = 0;
       max_load_factor = (max_load_dividend, max_load_divisor);
@@ -78,20 +78,20 @@ let rec hashmap_HashMap_clear_loop
     let* i2 = usize_add i 1 in
     let* slots1 = index_mut_back Hashmap_List_Nil in
     hashmap_HashMap_clear_loop t slots1 i2
-  else Return slots
+  else Ok slots
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::clear]:
     Source: 'src/hashmap.rs', lines 80:4-80:27 *)
 let hashmap_HashMap_clear
   (t : Type0) (self : hashmap_HashMap_t t) : result (hashmap_HashMap_t t) =
   let* hm = hashmap_HashMap_clear_loop t self.slots 0 in
-  Return { self with num_entries = 0; slots = hm }
+  Ok { self with num_entries = 0; slots = hm }
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::len]:
     Source: 'src/hashmap.rs', lines 90:4-90:30 *)
 let hashmap_HashMap_len
   (t : Type0) (self : hashmap_HashMap_t t) : result usize =
-  Return self.num_entries
+  Ok self.num_entries
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert_in_list]: loop 0:
     Source: 'src/hashmap.rs', lines 97:4-114:5 *)
@@ -103,12 +103,11 @@ let rec hashmap_HashMap_insert_in_list_loop
   begin match ls with
   | Hashmap_List_Cons ckey cvalue tl ->
     if ckey = key
-    then Return (false, Hashmap_List_Cons ckey value tl)
+    then Ok (false, Hashmap_List_Cons ckey value tl)
     else
       let* (b, tl1) = hashmap_HashMap_insert_in_list_loop t key value tl in
-      Return (b, Hashmap_List_Cons ckey cvalue tl1)
-  | Hashmap_List_Nil ->
-    Return (true, Hashmap_List_Cons key value Hashmap_List_Nil)
+      Ok (b, Hashmap_List_Cons ckey cvalue tl1)
+  | Hashmap_List_Nil -> Ok (true, Hashmap_List_Cons key value Hashmap_List_Nil)
   end
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert_in_list]:
@@ -137,8 +136,8 @@ let hashmap_HashMap_insert_no_resize
   then
     let* i1 = usize_add self.num_entries 1 in
     let* v = index_mut_back l1 in
-    Return { self with num_entries = i1; slots = v }
-  else let* v = index_mut_back l1 in Return { self with slots = v }
+    Ok { self with num_entries = i1; slots = v }
+  else let* v = index_mut_back l1 in Ok { self with slots = v }
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements_from_list]: loop 0:
     Source: 'src/hashmap.rs', lines 183:4-196:5 *)
@@ -152,7 +151,7 @@ let rec hashmap_HashMap_move_elements_from_list_loop
   | Hashmap_List_Cons k v tl ->
     let* ntable1 = hashmap_HashMap_insert_no_resize t ntable k v in
     hashmap_HashMap_move_elements_from_list_loop t ntable1 tl
-  | Hashmap_List_Nil -> Return ntable
+  | Hashmap_List_Nil -> Ok ntable
   end
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements_from_list]:
@@ -183,7 +182,7 @@ let rec hashmap_HashMap_move_elements_loop
     let* i2 = usize_add i 1 in
     let* slots1 = index_mut_back l1 in
     hashmap_HashMap_move_elements_loop t ntable1 slots1 i2
-  else Return (ntable, slots)
+  else Ok (ntable, slots)
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements]:
     Source: 'src/hashmap.rs', lines 171:4-171:95 *)
@@ -209,10 +208,10 @@ let hashmap_HashMap_try_resize
     let* ntable = hashmap_HashMap_new_with_capacity t i3 i i1 in
     let* p = hashmap_HashMap_move_elements t ntable self.slots 0 in
     let (ntable1, _) = p in
-    Return
+    Ok
       { ntable1 with num_entries = self.num_entries; max_load_factor = (i, i1)
       }
-  else Return { self with max_load_factor = (i, i1) }
+  else Ok { self with max_load_factor = (i, i1) }
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert]:
     Source: 'src/hashmap.rs', lines 129:4-129:48 *)
@@ -222,9 +221,7 @@ let hashmap_HashMap_insert
   =
   let* self1 = hashmap_HashMap_insert_no_resize t self key value in
   let* i = hashmap_HashMap_len t self1 in
-  if i > self1.max_load
-  then hashmap_HashMap_try_resize t self1
-  else Return self1
+  if i > self1.max_load then hashmap_HashMap_try_resize t self1 else Ok self1
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
     Source: 'src/hashmap.rs', lines 206:4-219:5 *)
@@ -236,9 +233,9 @@ let rec hashmap_HashMap_contains_key_in_list_loop
   begin match ls with
   | Hashmap_List_Cons ckey _ tl ->
     if ckey = key
-    then Return true
+    then Ok true
     else hashmap_HashMap_contains_key_in_list_loop t key tl
-  | Hashmap_List_Nil -> Return false
+  | Hashmap_List_Nil -> Ok false
   end
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::contains_key_in_list]:
@@ -269,9 +266,7 @@ let rec hashmap_HashMap_get_in_list_loop
   =
   begin match ls with
   | Hashmap_List_Cons ckey cvalue tl ->
-    if ckey = key
-    then Return cvalue
-    else hashmap_HashMap_get_in_list_loop t key tl
+    if ckey = key then Ok cvalue else hashmap_HashMap_get_in_list_loop t key tl
   | Hashmap_List_Nil -> Fail Failure
   end
 
@@ -305,14 +300,14 @@ let rec hashmap_HashMap_get_mut_in_list_loop
   | Hashmap_List_Cons ckey cvalue tl ->
     if ckey = key
     then
-      let back = fun ret -> Return (Hashmap_List_Cons ckey ret tl) in
-      Return (cvalue, back)
+      let back = fun ret -> Ok (Hashmap_List_Cons ckey ret tl) in
+      Ok (cvalue, back)
     else
       let* (x, back) = hashmap_HashMap_get_mut_in_list_loop t tl key in
       let back1 =
         fun ret ->
-          let* tl1 = back ret in Return (Hashmap_List_Cons ckey cvalue tl1) in
-      Return (x, back1)
+          let* tl1 = back ret in Ok (Hashmap_List_Cons ckey cvalue tl1) in
+      Ok (x, back1)
   | Hashmap_List_Nil -> Fail Failure
   end
 
@@ -342,8 +337,8 @@ let hashmap_HashMap_get_mut
     fun ret ->
       let* l1 = get_mut_in_list_back ret in
       let* v = index_mut_back l1 in
-      Return { self with slots = v } in
-  Return (x, back)
+      Ok { self with slots = v } in
+  Ok (x, back)
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::remove_from_list]: loop 0:
     Source: 'src/hashmap.rs', lines 265:4-291:5 *)
@@ -360,13 +355,13 @@ let rec hashmap_HashMap_remove_from_list_loop
         core_mem_replace (hashmap_List_t t) (Hashmap_List_Cons ckey x tl)
           Hashmap_List_Nil in
       begin match mv_ls with
-      | Hashmap_List_Cons _ cvalue tl1 -> Return (Some cvalue, tl1)
+      | Hashmap_List_Cons _ cvalue tl1 -> Ok (Some cvalue, tl1)
       | Hashmap_List_Nil -> Fail Failure
       end
     else
       let* (o, tl1) = hashmap_HashMap_remove_from_list_loop t key tl in
-      Return (o, Hashmap_List_Cons ckey x tl1)
-  | Hashmap_List_Nil -> Return (None, Hashmap_List_Nil)
+      Ok (o, Hashmap_List_Cons ckey x tl1)
+  | Hashmap_List_Nil -> Ok (None, Hashmap_List_Nil)
   end
 
 (** [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::remove_from_list]:
@@ -392,12 +387,11 @@ let hashmap_HashMap_remove
       self.slots hash_mod in
   let* (x, l1) = hashmap_HashMap_remove_from_list t key l in
   begin match x with
-  | None ->
-    let* v = index_mut_back l1 in Return (None, { self with slots = v })
+  | None -> let* v = index_mut_back l1 in Ok (None, { self with slots = v })
   | Some x1 ->
     let* i1 = usize_sub self.num_entries 1 in
     let* v = index_mut_back l1 in
-    Return (Some x1, { self with num_entries = i1; slots = v })
+    Ok (Some x1, { self with num_entries = i1; slots = v })
   end
 
 (** [hashmap_main::hashmap::test1]:
@@ -434,7 +428,7 @@ let hashmap_test1 : result unit =
             then Fail Failure
             else
               let* i4 = hashmap_HashMap_get u64 hm6 1056 in
-              if not (i4 = 256) then Fail Failure else Return ()
+              if not (i4 = 256) then Fail Failure else Ok ()
       end
 
 (** [hashmap_main::insert_on_disk]:
@@ -448,5 +442,5 @@ let insert_on_disk
 (** [hashmap_main::main]:
     Source: 'src/hashmap_main.rs', lines 16:0-16:13 *)
 let main : result unit =
-  Return ()
+  Ok ()
 
diff --git a/tests/fstar/hashmap_on_disk/HashmapMain.Properties.fst b/tests/fstar/hashmap_on_disk/HashmapMain.Properties.fst
index 358df29e..beb3dc2c 100644
--- a/tests/fstar/hashmap_on_disk/HashmapMain.Properties.fst
+++ b/tests/fstar/hashmap_on_disk/HashmapMain.Properties.fst
@@ -20,7 +20,7 @@ assume
 val serialize_lem (hm : hashmap_HashMap_t u64) (st : state) : Lemma (
   match hashmap_utils_serialize hm st with
   | Fail _ -> True
-  | Return (st', ()) -> state_v st' == hm)
+  | Ok (st', ()) -> state_v st' == hm)
   [SMTPat (hashmap_utils_serialize hm st)]
 
 /// [deserialize] gives us the hash map stored on disk, without updating it
@@ -28,7 +28,7 @@ assume
 val deserialize_lem (st : state) : Lemma (
   match hashmap_utils_deserialize st with
   | Fail _ -> True
-  | Return (st', hm) -> hm == state_v st /\ st' == st)
+  | Ok (st', hm) -> hm == state_v st /\ st' == st)
   [SMTPat (hashmap_utils_deserialize st)]
 
 (*** Lemmas *)
@@ -39,10 +39,10 @@ val deserialize_lem (st : state) : Lemma (
 val insert_on_disk_lem (key : usize) (value : u64) (st : state) : Lemma (
   match insert_on_disk key value st with
   | Fail _ -> True
-  | Return (st', ()) ->
+  | Ok (st', ()) ->
     let hm = state_v st in
     match hashmap_HashMap_insert u64 hm key value with
     | Fail _ -> False
-    | Return hm' -> hm' == state_v st')
+    | Ok hm' -> hm' == state_v st')
 
 let insert_on_disk_lem key value st = ()
diff --git a/tests/fstar/hashmap_on_disk/Primitives.fst b/tests/fstar/hashmap_on_disk/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/hashmap_on_disk/Primitives.fst
+++ b/tests/fstar/hashmap_on_disk/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/misc/Bitwise.fst b/tests/fstar/misc/Bitwise.fst
index 7330f07a..11ef6861 100644
--- a/tests/fstar/misc/Bitwise.fst
+++ b/tests/fstar/misc/Bitwise.fst
@@ -18,15 +18,15 @@ let shift_i32 (a : i32) : result i32 =
 (** [bitwise::xor_u32]:
     Source: 'src/bitwise.rs', lines 17:0-17:37 *)
 let xor_u32 (a : u32) (b : u32) : result u32 =
-  Return (u32_xor a b)
+  Ok (u32_xor a b)
 
 (** [bitwise::or_u32]:
     Source: 'src/bitwise.rs', lines 21:0-21:36 *)
 let or_u32 (a : u32) (b : u32) : result u32 =
-  Return (u32_or a b)
+  Ok (u32_or a b)
 
 (** [bitwise::and_u32]:
     Source: 'src/bitwise.rs', lines 25:0-25:37 *)
 let and_u32 (a : u32) (b : u32) : result u32 =
-  Return (u32_and a b)
+  Ok (u32_and a b)
 
diff --git a/tests/fstar/misc/Constants.fst b/tests/fstar/misc/Constants.fst
index 8d1cf3ce..4fbafb83 100644
--- a/tests/fstar/misc/Constants.fst
+++ b/tests/fstar/misc/Constants.fst
@@ -7,17 +7,17 @@ open Primitives
 
 (** [constants::X0]
     Source: 'src/constants.rs', lines 5:0-5:17 *)
-let x0_body : result u32 = Return 0
+let x0_body : result u32 = Ok 0
 let x0 : u32 = eval_global x0_body
 
 (** [constants::X1]
     Source: 'src/constants.rs', lines 7:0-7:17 *)
-let x1_body : result u32 = Return core_u32_max
+let x1_body : result u32 = Ok core_u32_max
 let x1 : u32 = eval_global x1_body
 
 (** [constants::X2]
     Source: 'src/constants.rs', lines 10:0-10:17 *)
-let x2_body : result u32 = Return 3
+let x2_body : result u32 = Ok 3
 let x2 : u32 = eval_global x2_body
 
 (** [constants::incr]:
@@ -33,7 +33,7 @@ let x3 : u32 = eval_global x3_body
 (** [constants::mk_pair0]:
     Source: 'src/constants.rs', lines 23:0-23:51 *)
 let mk_pair0 (x : u32) (y1 : u32) : result (u32 & u32) =
-  Return (x, y1)
+  Ok (x, y1)
 
 (** [constants::Pair]
     Source: 'src/constants.rs', lines 36:0-36:23 *)
@@ -42,7 +42,7 @@ type pair_t (t1 t2 : Type0) = { x : t1; y : t2; }
 (** [constants::mk_pair1]:
     Source: 'src/constants.rs', lines 27:0-27:55 *)
 let mk_pair1 (x : u32) (y1 : u32) : result (pair_t u32 u32) =
-  Return { x = x; y = y1 }
+  Ok { x = x; y = y1 }
 
 (** [constants::P0]
     Source: 'src/constants.rs', lines 31:0-31:24 *)
@@ -56,12 +56,12 @@ let p1 : pair_t u32 u32 = eval_global p1_body
 
 (** [constants::P2]
     Source: 'src/constants.rs', lines 33:0-33:24 *)
-let p2_body : result (u32 & u32) = Return (0, 1)
+let p2_body : result (u32 & u32) = Ok (0, 1)
 let p2 : (u32 & u32) = eval_global p2_body
 
 (** [constants::P3]
     Source: 'src/constants.rs', lines 34:0-34:28 *)
-let p3_body : result (pair_t u32 u32) = Return { x = 0; y = 1 }
+let p3_body : result (pair_t u32 u32) = Ok { x = 0; y = 1 }
 let p3 : pair_t u32 u32 = eval_global p3_body
 
 (** [constants::Wrap]
@@ -71,7 +71,7 @@ type wrap_t (t : Type0) = { value : t; }
 (** [constants::{constants::Wrap<T>}::new]:
     Source: 'src/constants.rs', lines 54:4-54:41 *)
 let wrap_new (t : Type0) (value : t) : result (wrap_t t) =
-  Return { value = value }
+  Ok { value = value }
 
 (** [constants::Y]
     Source: 'src/constants.rs', lines 41:0-41:22 *)
@@ -81,7 +81,7 @@ let y : wrap_t i32 = eval_global y_body
 (** [constants::unwrap_y]:
     Source: 'src/constants.rs', lines 43:0-43:30 *)
 let unwrap_y : result i32 =
-  Return y.value
+  Ok y.value
 
 (** [constants::YVAL]
     Source: 'src/constants.rs', lines 47:0-47:19 *)
@@ -90,13 +90,13 @@ let yval : i32 = eval_global yval_body
 
 (** [constants::get_z1::Z1]
     Source: 'src/constants.rs', lines 62:4-62:17 *)
-let get_z1_z1_body : result i32 = Return 3
+let get_z1_z1_body : result i32 = Ok 3
 let get_z1_z1 : i32 = eval_global get_z1_z1_body
 
 (** [constants::get_z1]:
     Source: 'src/constants.rs', lines 61:0-61:28 *)
 let get_z1 : result i32 =
-  Return get_z1_z1
+  Ok get_z1_z1
 
 (** [constants::add]:
     Source: 'src/constants.rs', lines 66:0-66:39 *)
@@ -105,12 +105,12 @@ let add (a : i32) (b : i32) : result i32 =
 
 (** [constants::Q1]
     Source: 'src/constants.rs', lines 74:0-74:17 *)
-let q1_body : result i32 = Return 5
+let q1_body : result i32 = Ok 5
 let q1 : i32 = eval_global q1_body
 
 (** [constants::Q2]
     Source: 'src/constants.rs', lines 75:0-75:17 *)
-let q2_body : result i32 = Return q1
+let q2_body : result i32 = Ok q1
 let q2 : i32 = eval_global q2_body
 
 (** [constants::Q3]
@@ -125,7 +125,7 @@ let get_z2 : result i32 =
 
 (** [constants::S1]
     Source: 'src/constants.rs', lines 80:0-80:18 *)
-let s1_body : result u32 = Return 6
+let s1_body : result u32 = Ok 6
 let s1 : u32 = eval_global s1_body
 
 (** [constants::S2]
@@ -135,7 +135,7 @@ let s2 : u32 = eval_global s2_body
 
 (** [constants::S3]
     Source: 'src/constants.rs', lines 82:0-82:29 *)
-let s3_body : result (pair_t u32 u32) = Return p3
+let s3_body : result (pair_t u32 u32) = Ok p3
 let s3 : pair_t u32 u32 = eval_global s3_body
 
 (** [constants::S4]
@@ -149,11 +149,11 @@ type v_t (t : Type0) (n : usize) = { x : array t n; }
 
 (** [constants::{constants::V<T, N>#1}::LEN]
     Source: 'src/constants.rs', lines 91:4-91:24 *)
-let v_len_body (t : Type0) (n : usize) : result usize = Return n
+let v_len_body (t : Type0) (n : usize) : result usize = Ok n
 let v_len (t : Type0) (n : usize) : usize = eval_global (v_len_body t n)
 
 (** [constants::use_v]:
     Source: 'src/constants.rs', lines 94:0-94:42 *)
 let use_v (t : Type0) (n : usize) : result usize =
-  Return (v_len t n)
+  Ok (v_len t n)
 
diff --git a/tests/fstar/misc/External.Funs.fst b/tests/fstar/misc/External.Funs.fst
index 78960404..d4247b8f 100644
--- a/tests/fstar/misc/External.Funs.fst
+++ b/tests/fstar/misc/External.Funs.fst
@@ -22,10 +22,10 @@ let test_new_non_zero_u32
 (** [external::test_vec]:
     Source: 'src/external.rs', lines 17:0-17:17 *)
 let test_vec : result unit =
-  let* _ = alloc_vec_Vec_push u32 (alloc_vec_Vec_new u32) 0 in Return ()
+  let* _ = alloc_vec_Vec_push u32 (alloc_vec_Vec_new u32) 0 in Ok ()
 
 (** Unit test for [external::test_vec] *)
-let _ = assert_norm (test_vec = Return ())
+let _ = assert_norm (test_vec = Ok ())
 
 (** [external::custom_swap]:
     Source: 'src/external.rs', lines 24:0-24:66 *)
@@ -34,8 +34,8 @@ let custom_swap
   result (state & (t & (t -> state -> result (state & (t & t)))))
   =
   let* (st1, (x1, y1)) = core_mem_swap t x y st in
-  let back = fun ret st2 -> Return (st2, (ret, y1)) in
-  Return (st1, (x1, back))
+  let back = fun ret st2 -> Ok (st2, (ret, y1)) in
+  Ok (st1, (x1, back))
 
 (** [external::test_custom_swap]:
     Source: 'src/external.rs', lines 29:0-29:59 *)
@@ -43,12 +43,12 @@ let test_custom_swap
   (x : u32) (y : u32) (st : state) : result (state & (u32 & u32)) =
   let* (st1, (_, custom_swap_back)) = custom_swap u32 x y st in
   let* (_, (x1, y1)) = custom_swap_back 1 st1 in
-  Return (st1, (x1, y1))
+  Ok (st1, (x1, y1))
 
 (** [external::test_swap_non_zero]:
     Source: 'src/external.rs', lines 35:0-35:44 *)
 let test_swap_non_zero (x : u32) (st : state) : result (state & u32) =
   let* (st1, p) = swap u32 x 0 st in
   let (x1, _) = p in
-  if x1 = 0 then Fail Failure else Return (st1, x1)
+  if x1 = 0 then Fail Failure else Ok (st1, x1)
 
diff --git a/tests/fstar/misc/Loops.Funs.fst b/tests/fstar/misc/Loops.Funs.fst
index 93683deb..26cb91d2 100644
--- a/tests/fstar/misc/Loops.Funs.fst
+++ b/tests/fstar/misc/Loops.Funs.fst
@@ -70,7 +70,7 @@ let rec sum_array_loop
     let* s1 = u32_add s i1 in
     let* i2 = usize_add i 1 in
     sum_array_loop n a i2 s1
-  else Return s
+  else Ok s
 
 (** [loops::sum_array]:
     Source: 'src/loops.rs', lines 50:0-50:52 *)
@@ -92,7 +92,7 @@ let rec clear_loop
     let* i2 = usize_add i 1 in
     let* v1 = index_mut_back 0 in
     clear_loop v1 i2
-  else Return v
+  else Ok v
 
 (** [loops::clear]:
     Source: 'src/loops.rs', lines 62:0-62:30 *)
@@ -106,8 +106,8 @@ let rec list_mem_loop
   Tot (result bool) (decreases (list_mem_loop_decreases x ls))
   =
   begin match ls with
-  | List_Cons y tl -> if y = x then Return true else list_mem_loop x tl
-  | List_Nil -> Return false
+  | List_Cons y tl -> if y = x then Ok true else list_mem_loop x tl
+  | List_Nil -> Ok false
   end
 
 (** [loops::list_mem]:
@@ -125,12 +125,12 @@ let rec list_nth_mut_loop_loop
   begin match ls with
   | List_Cons x tl ->
     if i = 0
-    then let back = fun ret -> Return (List_Cons ret tl) in Return (x, back)
+    then let back = fun ret -> Ok (List_Cons ret tl) in Ok (x, back)
     else
       let* i1 = u32_sub i 1 in
       let* (x1, back) = list_nth_mut_loop_loop t tl i1 in
-      let back1 = fun ret -> let* tl1 = back ret in Return (List_Cons x tl1) in
-      Return (x1, back1)
+      let back1 = fun ret -> let* tl1 = back ret in Ok (List_Cons x tl1) in
+      Ok (x1, back1)
   | List_Nil -> Fail Failure
   end
 
@@ -151,7 +151,7 @@ let rec list_nth_shared_loop_loop
   begin match ls with
   | List_Cons x tl ->
     if i = 0
-    then Return x
+    then Ok x
     else let* i1 = u32_sub i 1 in list_nth_shared_loop_loop t tl i1
   | List_Nil -> Fail Failure
   end
@@ -171,11 +171,11 @@ let rec get_elem_mut_loop
   begin match ls with
   | List_Cons y tl ->
     if y = x
-    then let back = fun ret -> Return (List_Cons ret tl) in Return (y, back)
+    then let back = fun ret -> Ok (List_Cons ret tl) in Ok (y, back)
     else
       let* (i, back) = get_elem_mut_loop x tl in
-      let back1 = fun ret -> let* tl1 = back ret in Return (List_Cons y tl1) in
-      Return (i, back1)
+      let back1 = fun ret -> let* tl1 = back ret in Ok (List_Cons y tl1) in
+      Ok (i, back1)
   | List_Nil -> Fail Failure
   end
 
@@ -190,7 +190,7 @@ let get_elem_mut
       (core_slice_index_SliceIndexUsizeSliceTInst (list_t usize)) slots 0 in
   let* (i, back) = get_elem_mut_loop x ls in
   let back1 = fun ret -> let* l = back ret in index_mut_back l in
-  Return (i, back1)
+  Ok (i, back1)
 
 (** [loops::get_elem_shared]: loop 0:
     Source: 'src/loops.rs', lines 129:0-143:1 *)
@@ -199,7 +199,7 @@ let rec get_elem_shared_loop
   Tot (result usize) (decreases (get_elem_shared_loop_decreases x ls))
   =
   begin match ls with
-  | List_Cons y tl -> if y = x then Return y else get_elem_shared_loop x tl
+  | List_Cons y tl -> if y = x then Ok y else get_elem_shared_loop x tl
   | List_Nil -> Fail Failure
   end
 
@@ -218,12 +218,12 @@ let id_mut
   (t : Type0) (ls : list_t t) :
   result ((list_t t) & (list_t t -> result (list_t t)))
   =
-  Return (ls, Return)
+  Ok (ls, Ok)
 
 (** [loops::id_shared]:
     Source: 'src/loops.rs', lines 149:0-149:45 *)
 let id_shared (t : Type0) (ls : list_t t) : result (list_t t) =
-  Return ls
+  Ok ls
 
 (** [loops::list_nth_mut_loop_with_id]: loop 0:
     Source: 'src/loops.rs', lines 154:0-165:1 *)
@@ -235,12 +235,12 @@ let rec list_nth_mut_loop_with_id_loop
   begin match ls with
   | List_Cons x tl ->
     if i = 0
-    then let back = fun ret -> Return (List_Cons ret tl) in Return (x, back)
+    then let back = fun ret -> Ok (List_Cons ret tl) in Ok (x, back)
     else
       let* i1 = u32_sub i 1 in
       let* (x1, back) = list_nth_mut_loop_with_id_loop t i1 tl in
-      let back1 = fun ret -> let* tl1 = back ret in Return (List_Cons x tl1) in
-      Return (x1, back1)
+      let back1 = fun ret -> let* tl1 = back ret in Ok (List_Cons x tl1) in
+      Ok (x1, back1)
   | List_Nil -> Fail Failure
   end
 
@@ -253,7 +253,7 @@ let list_nth_mut_loop_with_id
   let* (ls1, id_mut_back) = id_mut t ls in
   let* (x, back) = list_nth_mut_loop_with_id_loop t i ls1 in
   let back1 = fun ret -> let* l = back ret in id_mut_back l in
-  Return (x, back1)
+  Ok (x, back1)
 
 (** [loops::list_nth_shared_loop_with_id]: loop 0:
     Source: 'src/loops.rs', lines 168:0-179:1 *)
@@ -265,7 +265,7 @@ let rec list_nth_shared_loop_with_id_loop
   begin match ls with
   | List_Cons x tl ->
     if i = 0
-    then Return x
+    then Ok x
     else let* i1 = u32_sub i 1 in list_nth_shared_loop_with_id_loop t i1 tl
   | List_Nil -> Fail Failure
   end
@@ -289,17 +289,17 @@ let rec list_nth_mut_loop_pair_loop
     | List_Cons x1 tl1 ->
       if i = 0
       then
-        let back'a = fun ret -> Return (List_Cons ret tl0) in
-        let back'b = fun ret -> Return (List_Cons ret tl1) in
-        Return ((x0, x1), back'a, back'b)
+        let back'a = fun ret -> Ok (List_Cons ret tl0) in
+        let back'b = fun ret -> Ok (List_Cons ret tl1) in
+        Ok ((x0, x1), back'a, back'b)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back'a, back'b) = list_nth_mut_loop_pair_loop t tl0 tl1 i1 in
         let back'a1 =
-          fun ret -> let* tl01 = back'a ret in Return (List_Cons x0 tl01) in
+          fun ret -> let* tl01 = back'a ret in Ok (List_Cons x0 tl01) in
         let back'b1 =
-          fun ret -> let* tl11 = back'b ret in Return (List_Cons x1 tl11) in
-        Return (p, back'a1, back'b1)
+          fun ret -> let* tl11 = back'b ret in Ok (List_Cons x1 tl11) in
+        Ok (p, back'a1, back'b1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -325,7 +325,7 @@ let rec list_nth_shared_loop_pair_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then Return (x0, x1)
+      then Ok (x0, x1)
       else let* i1 = u32_sub i 1 in list_nth_shared_loop_pair_loop t tl0 tl1 i1
     | List_Nil -> Fail Failure
     end
@@ -353,16 +353,16 @@ let rec list_nth_mut_loop_pair_merge_loop
       then
         let back =
           fun ret ->
-            let (x, x2) = ret in Return (List_Cons x tl0, List_Cons x2 tl1) in
-        Return ((x0, x1), back)
+            let (x, x2) = ret in Ok (List_Cons x tl0, List_Cons x2 tl1) in
+        Ok ((x0, x1), back)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back) = list_nth_mut_loop_pair_merge_loop t tl0 tl1 i1 in
         let back1 =
           fun ret ->
             let* (tl01, tl11) = back ret in
-            Return (List_Cons x0 tl01, List_Cons x1 tl11) in
-        Return (p, back1)
+            Ok (List_Cons x0 tl01, List_Cons x1 tl11) in
+        Ok (p, back1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -388,7 +388,7 @@ let rec list_nth_shared_loop_pair_merge_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then Return (x0, x1)
+      then Ok (x0, x1)
       else
         let* i1 = u32_sub i 1 in
         list_nth_shared_loop_pair_merge_loop t tl0 tl1 i1
@@ -415,15 +415,13 @@ let rec list_nth_mut_shared_loop_pair_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then
-        let back = fun ret -> Return (List_Cons ret tl0) in
-        Return ((x0, x1), back)
+      then let back = fun ret -> Ok (List_Cons ret tl0) in Ok ((x0, x1), back)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back) = list_nth_mut_shared_loop_pair_loop t tl0 tl1 i1 in
-        let back1 =
-          fun ret -> let* tl01 = back ret in Return (List_Cons x0 tl01) in
-        Return (p, back1)
+        let back1 = fun ret -> let* tl01 = back ret in Ok (List_Cons x0 tl01)
+          in
+        Ok (p, back1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -449,16 +447,14 @@ let rec list_nth_mut_shared_loop_pair_merge_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then
-        let back = fun ret -> Return (List_Cons ret tl0) in
-        Return ((x0, x1), back)
+      then let back = fun ret -> Ok (List_Cons ret tl0) in Ok ((x0, x1), back)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back) = list_nth_mut_shared_loop_pair_merge_loop t tl0 tl1 i1
           in
-        let back1 =
-          fun ret -> let* tl01 = back ret in Return (List_Cons x0 tl01) in
-        Return (p, back1)
+        let back1 = fun ret -> let* tl01 = back ret in Ok (List_Cons x0 tl01)
+          in
+        Ok (p, back1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -484,15 +480,13 @@ let rec list_nth_shared_mut_loop_pair_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then
-        let back = fun ret -> Return (List_Cons ret tl1) in
-        Return ((x0, x1), back)
+      then let back = fun ret -> Ok (List_Cons ret tl1) in Ok ((x0, x1), back)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back) = list_nth_shared_mut_loop_pair_loop t tl0 tl1 i1 in
-        let back1 =
-          fun ret -> let* tl11 = back ret in Return (List_Cons x1 tl11) in
-        Return (p, back1)
+        let back1 = fun ret -> let* tl11 = back ret in Ok (List_Cons x1 tl11)
+          in
+        Ok (p, back1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -518,16 +512,14 @@ let rec list_nth_shared_mut_loop_pair_merge_loop
     begin match ls1 with
     | List_Cons x1 tl1 ->
       if i = 0
-      then
-        let back = fun ret -> Return (List_Cons ret tl1) in
-        Return ((x0, x1), back)
+      then let back = fun ret -> Ok (List_Cons ret tl1) in Ok ((x0, x1), back)
       else
         let* i1 = u32_sub i 1 in
         let* (p, back) = list_nth_shared_mut_loop_pair_merge_loop t tl0 tl1 i1
           in
-        let back1 =
-          fun ret -> let* tl11 = back ret in Return (List_Cons x1 tl11) in
-        Return (p, back1)
+        let back1 = fun ret -> let* tl11 = back ret in Ok (List_Cons x1 tl11)
+          in
+        Ok (p, back1)
     | List_Nil -> Fail Failure
     end
   | List_Nil -> Fail Failure
@@ -549,12 +541,12 @@ let rec ignore_input_mut_borrow_loop
   =
   if i > 0
   then let* i1 = u32_sub i 1 in ignore_input_mut_borrow_loop i1
-  else Return ()
+  else Ok ()
 
 (** [loops::ignore_input_mut_borrow]:
     Source: 'src/loops.rs', lines 345:0-345:56 *)
 let ignore_input_mut_borrow (_a : u32) (i : u32) : result u32 =
-  let* _ = ignore_input_mut_borrow_loop i in Return _a
+  let* _ = ignore_input_mut_borrow_loop i in Ok _a
 
 (** [loops::incr_ignore_input_mut_borrow]: loop 0:
     Source: 'src/loops.rs', lines 353:0-358:1 *)
@@ -564,14 +556,14 @@ let rec incr_ignore_input_mut_borrow_loop
   =
   if i > 0
   then let* i1 = u32_sub i 1 in incr_ignore_input_mut_borrow_loop i1
-  else Return ()
+  else Ok ()
 
 (** [loops::incr_ignore_input_mut_borrow]:
     Source: 'src/loops.rs', lines 353:0-353:60 *)
 let incr_ignore_input_mut_borrow (a : u32) (i : u32) : result u32 =
   let* a1 = u32_add a 1 in
   let* _ = incr_ignore_input_mut_borrow_loop i in
-  Return a1
+  Ok a1
 
 (** [loops::ignore_input_shared_borrow]: loop 0:
     Source: 'src/loops.rs', lines 362:0-366:1 *)
@@ -581,10 +573,10 @@ let rec ignore_input_shared_borrow_loop
   =
   if i > 0
   then let* i1 = u32_sub i 1 in ignore_input_shared_borrow_loop i1
-  else Return ()
+  else Ok ()
 
 (** [loops::ignore_input_shared_borrow]:
     Source: 'src/loops.rs', lines 362:0-362:59 *)
 let ignore_input_shared_borrow (_a : u32) (i : u32) : result u32 =
-  let* _ = ignore_input_shared_borrow_loop i in Return _a
+  let* _ = ignore_input_shared_borrow_loop i in Ok _a
 
diff --git a/tests/fstar/misc/NoNestedBorrows.fst b/tests/fstar/misc/NoNestedBorrows.fst
index 1a93beaa..ac443a99 100644
--- a/tests/fstar/misc/NoNestedBorrows.fst
+++ b/tests/fstar/misc/NoNestedBorrows.fst
@@ -151,20 +151,20 @@ let cast_bool_to_i32 (x : bool) : result i32 =
 (** [no_nested_borrows::cast_bool_to_bool]:
     Source: 'src/no_nested_borrows.rs', lines 137:0-137:41 *)
 let cast_bool_to_bool (x : bool) : result bool =
-  Return x
+  Ok x
 
 (** [no_nested_borrows::test2]:
     Source: 'src/no_nested_borrows.rs', lines 142:0-142:14 *)
 let test2 : result unit =
-  let* _ = u32_add 23 44 in Return ()
+  let* _ = u32_add 23 44 in Ok ()
 
 (** Unit test for [no_nested_borrows::test2] *)
-let _ = assert_norm (test2 = Return ())
+let _ = assert_norm (test2 = Ok ())
 
 (** [no_nested_borrows::get_max]:
     Source: 'src/no_nested_borrows.rs', lines 154:0-154:37 *)
 let get_max (x : u32) (y : u32) : result u32 =
-  if x >= y then Return x else Return y
+  if x >= y then Ok x else Ok y
 
 (** [no_nested_borrows::test3]:
     Source: 'src/no_nested_borrows.rs', lines 162:0-162:14 *)
@@ -172,26 +172,26 @@ let test3 : result unit =
   let* x = get_max 4 3 in
   let* y = get_max 10 11 in
   let* z = u32_add x y in
-  if not (z = 15) then Fail Failure else Return ()
+  if not (z = 15) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test3] *)
-let _ = assert_norm (test3 = Return ())
+let _ = assert_norm (test3 = Ok ())
 
 (** [no_nested_borrows::test_neg1]:
     Source: 'src/no_nested_borrows.rs', lines 169:0-169:18 *)
 let test_neg1 : result unit =
-  let* y = i32_neg 3 in if not (y = -3) then Fail Failure else Return ()
+  let* y = i32_neg 3 in if not (y = -3) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_neg1] *)
-let _ = assert_norm (test_neg1 = Return ())
+let _ = assert_norm (test_neg1 = Ok ())
 
 (** [no_nested_borrows::refs_test1]:
     Source: 'src/no_nested_borrows.rs', lines 176:0-176:19 *)
 let refs_test1 : result unit =
-  if not (1 = 1) then Fail Failure else Return ()
+  if not (1 = 1) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::refs_test1] *)
-let _ = assert_norm (refs_test1 = Return ())
+let _ = assert_norm (refs_test1 = Ok ())
 
 (** [no_nested_borrows::refs_test2]:
     Source: 'src/no_nested_borrows.rs', lines 187:0-187:19 *)
@@ -204,18 +204,18 @@ let refs_test2 : result unit =
     else
       if not (2 = 2)
       then Fail Failure
-      else if not (2 = 2) then Fail Failure else Return ()
+      else if not (2 = 2) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::refs_test2] *)
-let _ = assert_norm (refs_test2 = Return ())
+let _ = assert_norm (refs_test2 = Ok ())
 
 (** [no_nested_borrows::test_list1]:
     Source: 'src/no_nested_borrows.rs', lines 203:0-203:19 *)
 let test_list1 : result unit =
-  Return ()
+  Ok ()
 
 (** Unit test for [no_nested_borrows::test_list1] *)
-let _ = assert_norm (test_list1 = Return ())
+let _ = assert_norm (test_list1 = Ok ())
 
 (** [no_nested_borrows::test_box1]:
     Source: 'src/no_nested_borrows.rs', lines 208:0-208:18 *)
@@ -223,56 +223,53 @@ let test_box1 : result unit =
   let* (_, deref_mut_back) = alloc_boxed_Box_deref_mut i32 0 in
   let* b = deref_mut_back 1 in
   let* x = alloc_boxed_Box_deref i32 b in
-  if not (x = 1) then Fail Failure else Return ()
+  if not (x = 1) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_box1] *)
-let _ = assert_norm (test_box1 = Return ())
+let _ = assert_norm (test_box1 = Ok ())
 
 (** [no_nested_borrows::copy_int]:
     Source: 'src/no_nested_borrows.rs', lines 218:0-218:30 *)
 let copy_int (x : i32) : result i32 =
-  Return x
+  Ok x
 
 (** [no_nested_borrows::test_unreachable]:
     Source: 'src/no_nested_borrows.rs', lines 224:0-224:32 *)
 let test_unreachable (b : bool) : result unit =
-  if b then Fail Failure else Return ()
+  if b then Fail Failure else Ok ()
 
 (** [no_nested_borrows::test_panic]:
     Source: 'src/no_nested_borrows.rs', lines 232:0-232:26 *)
 let test_panic (b : bool) : result unit =
-  if b then Fail Failure else Return ()
+  if b then Fail Failure else Ok ()
 
 (** [no_nested_borrows::test_copy_int]:
     Source: 'src/no_nested_borrows.rs', lines 239:0-239:22 *)
 let test_copy_int : result unit =
-  let* y = copy_int 0 in if not (0 = y) then Fail Failure else Return ()
+  let* y = copy_int 0 in if not (0 = y) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_copy_int] *)
-let _ = assert_norm (test_copy_int = Return ())
+let _ = assert_norm (test_copy_int = Ok ())
 
 (** [no_nested_borrows::is_cons]:
     Source: 'src/no_nested_borrows.rs', lines 246:0-246:38 *)
 let is_cons (t : Type0) (l : list_t t) : result bool =
-  begin match l with
-  | List_Cons _ _ -> Return true
-  | List_Nil -> Return false
-  end
+  begin match l with | List_Cons _ _ -> Ok true | List_Nil -> Ok false end
 
 (** [no_nested_borrows::test_is_cons]:
     Source: 'src/no_nested_borrows.rs', lines 253:0-253:21 *)
 let test_is_cons : result unit =
   let* b = is_cons i32 (List_Cons 0 List_Nil) in
-  if not b then Fail Failure else Return ()
+  if not b then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_is_cons] *)
-let _ = assert_norm (test_is_cons = Return ())
+let _ = assert_norm (test_is_cons = Ok ())
 
 (** [no_nested_borrows::split_list]:
     Source: 'src/no_nested_borrows.rs', lines 259:0-259:48 *)
 let split_list (t : Type0) (l : list_t t) : result (t & (list_t t)) =
   begin match l with
-  | List_Cons hd tl -> Return (hd, tl)
+  | List_Cons hd tl -> Ok (hd, tl)
   | List_Nil -> Fail Failure
   end
 
@@ -281,18 +278,18 @@ let split_list (t : Type0) (l : list_t t) : result (t & (list_t t)) =
 let test_split_list : result unit =
   let* p = split_list i32 (List_Cons 0 List_Nil) in
   let (hd, _) = p in
-  if not (hd = 0) then Fail Failure else Return ()
+  if not (hd = 0) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_split_list] *)
-let _ = assert_norm (test_split_list = Return ())
+let _ = assert_norm (test_split_list = Ok ())
 
 (** [no_nested_borrows::choose]:
     Source: 'src/no_nested_borrows.rs', lines 274:0-274:70 *)
 let choose
   (t : Type0) (b : bool) (x : t) (y : t) : result (t & (t -> result (t & t))) =
   if b
-  then let back = fun ret -> Return (ret, y) in Return (x, back)
-  else let back = fun ret -> Return (x, ret) in Return (y, back)
+  then let back = fun ret -> Ok (ret, y) in Ok (x, back)
+  else let back = fun ret -> Ok (x, ret) in Ok (y, back)
 
 (** [no_nested_borrows::choose_test]:
     Source: 'src/no_nested_borrows.rs', lines 282:0-282:20 *)
@@ -305,15 +302,15 @@ let choose_test : result unit =
     let* (x, y) = choose_back z1 in
     if not (x = 1)
     then Fail Failure
-    else if not (y = 0) then Fail Failure else Return ()
+    else if not (y = 0) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::choose_test] *)
-let _ = assert_norm (choose_test = Return ())
+let _ = assert_norm (choose_test = Ok ())
 
 (** [no_nested_borrows::test_char]:
     Source: 'src/no_nested_borrows.rs', lines 294:0-294:26 *)
 let test_char : result char =
-  Return 'a'
+  Ok 'a'
 
 (** [no_nested_borrows::Tree]
     Source: 'src/no_nested_borrows.rs', lines 299:0-299:16 *)
@@ -332,7 +329,7 @@ and nodeElem_t (t : Type0) =
 let rec list_length (t : Type0) (l : list_t t) : result u32 =
   begin match l with
   | List_Cons _ l1 -> let* i = list_length t l1 in u32_add 1 i
-  | List_Nil -> Return 0
+  | List_Nil -> Ok 0
   end
 
 (** [no_nested_borrows::list_nth_shared]:
@@ -340,9 +337,7 @@ let rec list_length (t : Type0) (l : list_t t) : result u32 =
 let rec list_nth_shared (t : Type0) (l : list_t t) (i : u32) : result t =
   begin match l with
   | List_Cons x tl ->
-    if i = 0
-    then Return x
-    else let* i1 = u32_sub i 1 in list_nth_shared t tl i1
+    if i = 0 then Ok x else let* i1 = u32_sub i 1 in list_nth_shared t tl i1
   | List_Nil -> Fail Failure
   end
 
@@ -355,14 +350,13 @@ let rec list_nth_mut
   begin match l with
   | List_Cons x tl ->
     if i = 0
-    then let back = fun ret -> Return (List_Cons ret tl) in Return (x, back)
+    then let back = fun ret -> Ok (List_Cons ret tl) in Ok (x, back)
     else
       let* i1 = u32_sub i 1 in
       let* (x1, list_nth_mut_back) = list_nth_mut t tl i1 in
       let back =
-        fun ret -> let* tl1 = list_nth_mut_back ret in Return (List_Cons x tl1)
-        in
-      Return (x1, back)
+        fun ret -> let* tl1 = list_nth_mut_back ret in Ok (List_Cons x tl1) in
+      Ok (x1, back)
   | List_Nil -> Fail Failure
   end
 
@@ -372,7 +366,7 @@ let rec list_rev_aux
   (t : Type0) (li : list_t t) (lo : list_t t) : result (list_t t) =
   begin match li with
   | List_Cons hd tl -> list_rev_aux t tl (List_Cons hd lo)
-  | List_Nil -> Return lo
+  | List_Nil -> Ok lo
   end
 
 (** [no_nested_borrows::list_rev]:
@@ -413,10 +407,10 @@ let test_list_functions : result unit =
             then Fail Failure
             else
               let* i6 = list_nth_shared i32 ls 2 in
-              if not (i6 = 2) then Fail Failure else Return ()
+              if not (i6 = 2) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_list_functions] *)
-let _ = assert_norm (test_list_functions = Return ())
+let _ = assert_norm (test_list_functions = Ok ())
 
 (** [no_nested_borrows::id_mut_pair1]:
     Source: 'src/no_nested_borrows.rs', lines 414:0-414:89 *)
@@ -424,7 +418,7 @@ let id_mut_pair1
   (t1 t2 : Type0) (x : t1) (y : t2) :
   result ((t1 & t2) & ((t1 & t2) -> result (t1 & t2)))
   =
-  Return ((x, y), Return)
+  Ok ((x, y), Ok)
 
 (** [no_nested_borrows::id_mut_pair2]:
     Source: 'src/no_nested_borrows.rs', lines 418:0-418:88 *)
@@ -432,7 +426,7 @@ let id_mut_pair2
   (t1 t2 : Type0) (p : (t1 & t2)) :
   result ((t1 & t2) & ((t1 & t2) -> result (t1 & t2)))
   =
-  let (x, x1) = p in Return ((x, x1), Return)
+  let (x, x1) = p in Ok ((x, x1), Ok)
 
 (** [no_nested_borrows::id_mut_pair3]:
     Source: 'src/no_nested_borrows.rs', lines 422:0-422:93 *)
@@ -440,7 +434,7 @@ let id_mut_pair3
   (t1 t2 : Type0) (x : t1) (y : t2) :
   result ((t1 & t2) & (t1 -> result t1) & (t2 -> result t2))
   =
-  Return ((x, y), Return, Return)
+  Ok ((x, y), Ok, Ok)
 
 (** [no_nested_borrows::id_mut_pair4]:
     Source: 'src/no_nested_borrows.rs', lines 426:0-426:92 *)
@@ -448,7 +442,7 @@ let id_mut_pair4
   (t1 t2 : Type0) (p : (t1 & t2)) :
   result ((t1 & t2) & (t1 -> result t1) & (t2 -> result t2))
   =
-  let (x, x1) = p in Return ((x, x1), Return, Return)
+  let (x, x1) = p in Ok ((x, x1), Ok, Ok)
 
 (** [no_nested_borrows::StructWithTuple]
     Source: 'src/no_nested_borrows.rs', lines 433:0-433:34 *)
@@ -457,17 +451,17 @@ type structWithTuple_t (t1 t2 : Type0) = { p : (t1 & t2); }
 (** [no_nested_borrows::new_tuple1]:
     Source: 'src/no_nested_borrows.rs', lines 437:0-437:48 *)
 let new_tuple1 : result (structWithTuple_t u32 u32) =
-  Return { p = (1, 2) }
+  Ok { p = (1, 2) }
 
 (** [no_nested_borrows::new_tuple2]:
     Source: 'src/no_nested_borrows.rs', lines 441:0-441:48 *)
 let new_tuple2 : result (structWithTuple_t i16 i16) =
-  Return { p = (1, 2) }
+  Ok { p = (1, 2) }
 
 (** [no_nested_borrows::new_tuple3]:
     Source: 'src/no_nested_borrows.rs', lines 445:0-445:48 *)
 let new_tuple3 : result (structWithTuple_t u64 i64) =
-  Return { p = (1, 2) }
+  Ok { p = (1, 2) }
 
 (** [no_nested_borrows::StructWithPair]
     Source: 'src/no_nested_borrows.rs', lines 450:0-450:33 *)
@@ -476,7 +470,7 @@ type structWithPair_t (t1 t2 : Type0) = { p : pair_t t1 t2; }
 (** [no_nested_borrows::new_pair1]:
     Source: 'src/no_nested_borrows.rs', lines 454:0-454:46 *)
 let new_pair1 : result (structWithPair_t u32 u32) =
-  Return { p = { x = 1; y = 2 } }
+  Ok { p = { x = 1; y = 2 } }
 
 (** [no_nested_borrows::test_constants]:
     Source: 'src/no_nested_borrows.rs', lines 462:0-462:23 *)
@@ -497,44 +491,44 @@ let test_constants : result unit =
       then Fail Failure
       else
         let* swp = new_pair1 in
-        if not (swp.p.x = 1) then Fail Failure else Return ()
+        if not (swp.p.x = 1) then Fail Failure else Ok ()
 
 (** Unit test for [no_nested_borrows::test_constants] *)
-let _ = assert_norm (test_constants = Return ())
+let _ = assert_norm (test_constants = Ok ())
 
 (** [no_nested_borrows::test_weird_borrows1]:
     Source: 'src/no_nested_borrows.rs', lines 471:0-471:28 *)
 let test_weird_borrows1 : result unit =
-  Return ()
+  Ok ()
 
 (** Unit test for [no_nested_borrows::test_weird_borrows1] *)
-let _ = assert_norm (test_weird_borrows1 = Return ())
+let _ = assert_norm (test_weird_borrows1 = Ok ())
 
 (** [no_nested_borrows::test_mem_replace]:
     Source: 'src/no_nested_borrows.rs', lines 481:0-481:37 *)
 let test_mem_replace (px : u32) : result u32 =
   let (y, _) = core_mem_replace u32 px 1 in
-  if not (y = 0) then Fail Failure else Return 2
+  if not (y = 0) then Fail Failure else Ok 2
 
 (** [no_nested_borrows::test_shared_borrow_bool1]:
     Source: 'src/no_nested_borrows.rs', lines 488:0-488:47 *)
 let test_shared_borrow_bool1 (b : bool) : result u32 =
-  if b then Return 0 else Return 1
+  if b then Ok 0 else Ok 1
 
 (** [no_nested_borrows::test_shared_borrow_bool2]:
     Source: 'src/no_nested_borrows.rs', lines 501:0-501:40 *)
 let test_shared_borrow_bool2 : result u32 =
-  Return 0
+  Ok 0
 
 (** [no_nested_borrows::test_shared_borrow_enum1]:
     Source: 'src/no_nested_borrows.rs', lines 516:0-516:52 *)
 let test_shared_borrow_enum1 (l : list_t u32) : result u32 =
-  begin match l with | List_Cons _ _ -> Return 1 | List_Nil -> Return 0 end
+  begin match l with | List_Cons _ _ -> Ok 1 | List_Nil -> Ok 0 end
 
 (** [no_nested_borrows::test_shared_borrow_enum2]:
     Source: 'src/no_nested_borrows.rs', lines 528:0-528:40 *)
 let test_shared_borrow_enum2 : result u32 =
-  Return 0
+  Ok 0
 
 (** [no_nested_borrows::incr]:
     Source: 'src/no_nested_borrows.rs', lines 539:0-539:24 *)
@@ -549,7 +543,7 @@ let call_incr (x : u32) : result u32 =
 (** [no_nested_borrows::read_then_incr]:
     Source: 'src/no_nested_borrows.rs', lines 548:0-548:41 *)
 let read_then_incr (x : u32) : result (u32 & u32) =
-  let* x1 = u32_add x 1 in Return (x, x1)
+  let* x1 = u32_add x 1 in Ok (x, x1)
 
 (** [no_nested_borrows::Tuple]
     Source: 'src/no_nested_borrows.rs', lines 554:0-554:24 *)
@@ -558,12 +552,12 @@ type tuple_t (t1 t2 : Type0) = t1 * t2
 (** [no_nested_borrows::use_tuple_struct]:
     Source: 'src/no_nested_borrows.rs', lines 556:0-556:48 *)
 let use_tuple_struct (x : tuple_t u32 u32) : result (tuple_t u32 u32) =
-  let (_, i) = x in Return (1, i)
+  let (_, i) = x in Ok (1, i)
 
 (** [no_nested_borrows::create_tuple_struct]:
     Source: 'src/no_nested_borrows.rs', lines 560:0-560:61 *)
 let create_tuple_struct (x : u32) (y : u64) : result (tuple_t u32 u64) =
-  Return (x, y)
+  Ok (x, y)
 
 (** [no_nested_borrows::IdType]
     Source: 'src/no_nested_borrows.rs', lines 565:0-565:20 *)
@@ -572,10 +566,10 @@ type idType_t (t : Type0) = t
 (** [no_nested_borrows::use_id_type]:
     Source: 'src/no_nested_borrows.rs', lines 567:0-567:40 *)
 let use_id_type (t : Type0) (x : idType_t t) : result t =
-  Return x
+  Ok x
 
 (** [no_nested_borrows::create_id_type]:
     Source: 'src/no_nested_borrows.rs', lines 571:0-571:43 *)
 let create_id_type (t : Type0) (x : t) : result (idType_t t) =
-  Return x
+  Ok x
 
diff --git a/tests/fstar/misc/Paper.fst b/tests/fstar/misc/Paper.fst
index c2f47ad1..e6b4eb25 100644
--- a/tests/fstar/misc/Paper.fst
+++ b/tests/fstar/misc/Paper.fst
@@ -13,18 +13,18 @@ let ref_incr (x : i32) : result i32 =
 (** [paper::test_incr]:
     Source: 'src/paper.rs', lines 8:0-8:18 *)
 let test_incr : result unit =
-  let* x = ref_incr 0 in if not (x = 1) then Fail Failure else Return ()
+  let* x = ref_incr 0 in if not (x = 1) then Fail Failure else Ok ()
 
 (** Unit test for [paper::test_incr] *)
-let _ = assert_norm (test_incr = Return ())
+let _ = assert_norm (test_incr = Ok ())
 
 (** [paper::choose]:
     Source: 'src/paper.rs', lines 15:0-15:70 *)
 let choose
   (t : Type0) (b : bool) (x : t) (y : t) : result (t & (t -> result (t & t))) =
   if b
-  then let back = fun ret -> Return (ret, y) in Return (x, back)
-  else let back = fun ret -> Return (x, ret) in Return (y, back)
+  then let back = fun ret -> Ok (ret, y) in Ok (x, back)
+  else let back = fun ret -> Ok (x, ret) in Ok (y, back)
 
 (** [paper::test_choose]:
     Source: 'src/paper.rs', lines 23:0-23:20 *)
@@ -37,10 +37,10 @@ let test_choose : result unit =
     let* (x, y) = choose_back z1 in
     if not (x = 1)
     then Fail Failure
-    else if not (y = 0) then Fail Failure else Return ()
+    else if not (y = 0) then Fail Failure else Ok ()
 
 (** Unit test for [paper::test_choose] *)
-let _ = assert_norm (test_choose = Return ())
+let _ = assert_norm (test_choose = Ok ())
 
 (** [paper::List]
     Source: 'src/paper.rs', lines 35:0-35:16 *)
@@ -57,14 +57,13 @@ let rec list_nth_mut
   begin match l with
   | List_Cons x tl ->
     if i = 0
-    then let back = fun ret -> Return (List_Cons ret tl) in Return (x, back)
+    then let back = fun ret -> Ok (List_Cons ret tl) in Ok (x, back)
     else
       let* i1 = u32_sub i 1 in
       let* (x1, list_nth_mut_back) = list_nth_mut t tl i1 in
       let back =
-        fun ret -> let* tl1 = list_nth_mut_back ret in Return (List_Cons x tl1)
-        in
-      Return (x1, back)
+        fun ret -> let* tl1 = list_nth_mut_back ret in Ok (List_Cons x tl1) in
+      Ok (x1, back)
   | List_Nil -> Fail Failure
   end
 
@@ -73,7 +72,7 @@ let rec list_nth_mut
 let rec sum (l : list_t i32) : result i32 =
   begin match l with
   | List_Cons x tl -> let* i = sum tl in i32_add x i
-  | List_Nil -> Return 0
+  | List_Nil -> Ok 0
   end
 
 (** [paper::test_nth]:
@@ -85,10 +84,10 @@ let test_nth : result unit =
   let* x1 = i32_add x 1 in
   let* l2 = list_nth_mut_back x1 in
   let* i = sum l2 in
-  if not (i = 7) then Fail Failure else Return ()
+  if not (i = 7) then Fail Failure else Ok ()
 
 (** Unit test for [paper::test_nth] *)
-let _ = assert_norm (test_nth = Return ())
+let _ = assert_norm (test_nth = Ok ())
 
 (** [paper::call_choose]:
     Source: 'src/paper.rs', lines 76:0-76:44 *)
@@ -97,5 +96,5 @@ let call_choose (p : (u32 & u32)) : result u32 =
   let* (pz, choose_back) = choose u32 true px py in
   let* pz1 = u32_add pz 1 in
   let* (px1, _) = choose_back pz1 in
-  Return px1
+  Ok px1
 
diff --git a/tests/fstar/misc/PoloniusList.fst b/tests/fstar/misc/PoloniusList.fst
index 4203247e..c0bc592e 100644
--- a/tests/fstar/misc/PoloniusList.fst
+++ b/tests/fstar/misc/PoloniusList.fst
@@ -20,13 +20,13 @@ let rec get_list_at_x
   begin match ls with
   | List_Cons hd tl ->
     if hd = x
-    then Return (List_Cons hd tl, Return)
+    then Ok (List_Cons hd tl, Ok)
     else
       let* (l, get_list_at_x_back) = get_list_at_x tl x in
       let back =
-        fun ret ->
-          let* tl1 = get_list_at_x_back ret in Return (List_Cons hd tl1) in
-      Return (l, back)
-  | List_Nil -> Return (List_Nil, Return)
+        fun ret -> let* tl1 = get_list_at_x_back ret in Ok (List_Cons hd tl1)
+        in
+      Ok (l, back)
+  | List_Nil -> Ok (List_Nil, Ok)
   end
 
diff --git a/tests/fstar/misc/Primitives.fst b/tests/fstar/misc/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/misc/Primitives.fst
+++ b/tests/fstar/misc/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/traits/Primitives.fst b/tests/fstar/traits/Primitives.fst
index fca80829..acdb09dc 100644
--- a/tests/fstar/traits/Primitives.fst
+++ b/tests/fstar/traits/Primitives.fst
@@ -23,11 +23,11 @@ type error : Type0 =
 | OutOfFuel
 
 type result (a : Type0) : Type0 =
-| Return : v:a -> result a
+| Ok : v:a -> result a
 | Fail : e:error -> result a
 
 // Monadic return operator
-unfold let return (#a : Type0) (x : a) : result a = Return x
+unfold let return (#a : Type0) (x : a) : result a = Ok x
 
 // Monadic bind operator.
 // Allows to use the notation:
@@ -36,17 +36,17 @@ unfold let return (#a : Type0) (x : a) : result a = Return x
 // ...
 // ```
 unfold let (let*) (#a #b : Type0) (m: result a)
-  (f: (x:a) -> Pure (result b) (requires (m == Return x)) (ensures fun _ -> True)) :
+  (f: (x:a) -> Pure (result b) (requires (m == Ok x)) (ensures fun _ -> True)) :
   result b =
   match m with
-  | Return x -> f x
+  | Ok x -> f x
   | Fail e   -> Fail e
 
 // Monadic assert(...)
-let massert (b:bool) : result unit = if b then Return () else Fail Failure
+let massert (b:bool) : result unit = if b then Ok () else Fail Failure
 
 // Normalize and unwrap a successful result (used for globals).
-let eval_global (#a : Type0) (x : result a{Return? (normalize_term x)}) : a = Return?.v x
+let eval_global (#a : Type0) (x : result a{Ok? (normalize_term x)}) : a = Ok?.v x
 
 (*** Misc *)
 type char = FStar.Char.char
@@ -144,7 +144,7 @@ let scalar_max (ty : scalar_ty) : int =
 type scalar (ty : scalar_ty) : eqtype = x:int{scalar_min ty <= x && x <= scalar_max ty}
 
 let mk_scalar (ty : scalar_ty) (x : int) : result (scalar ty) =
-  if scalar_min ty <= x && scalar_max ty >= x then Return x else Fail Failure
+  if scalar_min ty <= x && scalar_max ty >= x then Ok x else Fail Failure
 
 let scalar_neg (#ty : scalar_ty) (x : scalar ty) : result (scalar ty) = mk_scalar ty (-x)
 
@@ -498,9 +498,9 @@ type core_ops_range_Range (a : Type0) = {
 
 (*** [alloc] *)
 
-let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Return x
+let alloc_boxed_Box_deref (t : Type0) (x : t) : result t = Ok x
 let alloc_boxed_Box_deref_mut (t : Type0) (x : t) : result (t & (t -> result t)) =
-  Return (x, (fun x -> Return x))
+  Ok (x, (fun x -> Ok x))
 
 // Trait instance
 let alloc_boxed_Box_coreopsDerefInst (self : Type0) : core_ops_deref_Deref self = {
@@ -528,20 +528,20 @@ let mk_array (a : Type0) (n : usize)
   l
 
 let array_index_usize (a : Type0) (n : usize) (x : array a n) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let array_update_usize (a : Type0) (n : usize) (x : array a n) (i : usize) (nx : a) :
   result (array a n) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let array_index_mut_usize (a : Type0) (n : usize) (x : array a n) (i : usize) :
   result (a & (a -> result (array a n))) =
   match array_index_usize a n x i with
   | Fail e -> Fail e
-  | Return v ->
-    Return (v, array_update_usize a n x i)
+  | Ok v ->
+    Ok (v, array_update_usize a n x i)
 
 (*** Slice *)
 type slice (a : Type0) = s:list a{length s <= usize_max}
@@ -549,30 +549,30 @@ type slice (a : Type0) = s:list a{length s <= usize_max}
 let slice_len (a : Type0) (s : slice a) : usize = length s
 
 let slice_index_usize (a : Type0) (x : slice a) (i : usize) : result a =
-  if i < length x then Return (index x i)
+  if i < length x then Ok (index x i)
   else Fail Failure
 
 let slice_update_usize (a : Type0) (x : slice a) (i : usize) (nx : a) : result (slice a) =
-  if i < length x then Return (list_update x i nx)
+  if i < length x then Ok (list_update x i nx)
   else Fail Failure
 
 let slice_index_mut_usize (a : Type0) (s : slice a) (i : usize) :
   result (a & (a -> result (slice a))) =
   match slice_index_usize a s i with
   | Fail e -> Fail e
-  | Return x ->
-    Return (x, slice_update_usize a s i)
+  | Ok x ->
+    Ok (x, slice_update_usize a s i)
 
 (*** Subslices *)
 
-let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Return x
+let array_to_slice (a : Type0) (n : usize) (x : array a n) : result (slice a) = Ok x
 let array_from_slice (a : Type0) (n : usize) (x : array a n) (s : slice a) : result (array a n) =
-  if length s = n then Return s
+  if length s = n then Ok s
   else Fail Failure
 
 let array_to_slice_mut (a : Type0) (n : usize) (x : array a n) :
   result (slice a & (slice a -> result (array a n))) =
-  Return (x, array_from_slice a n x)
+  Ok (x, array_from_slice a n x)
 
 // TODO: finish the definitions below (there lacks [List.drop] and [List.take] in the standard library *)
 let array_subslice (a : Type0) (n : usize) (x : array a n) (r : core_ops_range_Range usize) : result (slice a) =
@@ -598,16 +598,16 @@ let alloc_vec_Vec_len (a : Type0) (v : alloc_vec_Vec a) : usize = length v
 
 // Helper
 let alloc_vec_Vec_index_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) : result a =
-  if i < length v then Return (index v i) else Fail Failure
+  if i < length v then Ok (index v i) else Fail Failure
 // Helper
 let alloc_vec_Vec_update_usize (#a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 let alloc_vec_Vec_index_mut_usize (#a : Type0) (v: alloc_vec_Vec a) (i: usize) :
   result (a & (a → result (alloc_vec_Vec a))) =
   match alloc_vec_Vec_index_usize v i with
-  | Return x ->
-    Return (x, alloc_vec_Vec_update_usize v i)
+  | Ok x ->
+    Ok (x, alloc_vec_Vec_update_usize v i)
   | Fail e -> Fail e
 
 let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
@@ -616,17 +616,17 @@ let alloc_vec_Vec_push (a  : Type0) (v : alloc_vec_Vec a) (x : a) :
   (ensures (fun res ->
     match res with
     | Fail e -> e == Failure
-    | Return v' -> length v' = length v + 1)) =
+    | Ok v' -> length v' = length v + 1)) =
   if length v < usize_max then begin
     (**) assert_norm(length [x] == 1);
     (**) append_length v [x];
     (**) assert(length (append v [x]) = length v + 1);
-    Return (append v [x])
+    Ok (append v [x])
     end
   else Fail Failure
 
 let alloc_vec_Vec_insert (a : Type0) (v : alloc_vec_Vec a) (i : usize) (x : a) : result (alloc_vec_Vec a) =
-  if i < length v then Return (list_update v i x) else Fail Failure
+  if i < length v then Ok (list_update v i x) else Fail Failure
 
 // Trait declaration: [core::slice::index::private_slice_index::Sealed]
 type core_slice_index_private_slice_index_Sealed (self : Type0) = unit
@@ -650,7 +650,7 @@ let core_slice_index_Slice_index
   let* x = inst.get i s in
   match x with
   | None -> Fail Failure
-  | Some x -> Return x
+  | Some x -> Ok x
 
 // [core::slice::index::Range:::get]: forward function
 let core_slice_index_RangeUsize_get (t : Type0) (i : core_ops_range_Range usize) (s : slice t) :
diff --git a/tests/fstar/traits/Traits.fst b/tests/fstar/traits/Traits.fst
index 199d49bf..1f0293a0 100644
--- a/tests/fstar/traits/Traits.fst
+++ b/tests/fstar/traits/Traits.fst
@@ -12,7 +12,7 @@ noeq type boolTrait_t (self : Type0) = { get_bool : self -> result bool; }
 (** [traits::{(traits::BoolTrait for bool)}::get_bool]:
     Source: 'src/traits.rs', lines 12:4-12:30 *)
 let boolTraitBool_get_bool (self : bool) : result bool =
-  Return self
+  Ok self
 
 (** Trait implementation: [traits::{(traits::BoolTrait for bool)}]
     Source: 'src/traits.rs', lines 11:0-11:23 *)
@@ -24,18 +24,18 @@ let boolTrait_ret_true
   (#self : Type0) (self_clause : boolTrait_t self) (self1 : self) :
   result bool
   =
-  Return true
+  Ok true
 
 (** [traits::test_bool_trait_bool]:
     Source: 'src/traits.rs', lines 17:0-17:44 *)
 let test_bool_trait_bool (x : bool) : result bool =
   let* b = boolTraitBool_get_bool x in
-  if b then boolTrait_ret_true boolTraitBool x else Return false
+  if b then boolTrait_ret_true boolTraitBool x else Ok false
 
 (** [traits::{(traits::BoolTrait for core::option::Option<T>)#1}::get_bool]:
     Source: 'src/traits.rs', lines 23:4-23:30 *)
 let boolTraitOption_get_bool (t : Type0) (self : option t) : result bool =
-  begin match self with | None -> Return false | Some _ -> Return true end
+  begin match self with | None -> Ok false | Some _ -> Ok true end
 
 (** Trait implementation: [traits::{(traits::BoolTrait for core::option::Option<T>)#1}]
     Source: 'src/traits.rs', lines 22:0-22:31 *)
@@ -47,7 +47,7 @@ let boolTraitOption (t : Type0) : boolTrait_t (option t) = {
     Source: 'src/traits.rs', lines 31:0-31:54 *)
 let test_bool_trait_option (t : Type0) (x : option t) : result bool =
   let* b = boolTraitOption_get_bool t x in
-  if b then boolTrait_ret_true (boolTraitOption t) x else Return false
+  if b then boolTrait_ret_true (boolTraitOption t) x else Ok false
 
 (** [traits::test_bool_trait]:
     Source: 'src/traits.rs', lines 35:0-35:50 *)
@@ -62,7 +62,7 @@ noeq type toU64_t (self : Type0) = { to_u64 : self -> result u64; }
 (** [traits::{(traits::ToU64 for u64)#2}::to_u64]:
     Source: 'src/traits.rs', lines 44:4-44:26 *)
 let toU64U64_to_u64 (self : u64) : result u64 =
-  Return self
+  Ok self
 
 (** Trait implementation: [traits::{(traits::ToU64 for u64)#2}]
     Source: 'src/traits.rs', lines 43:0-43:18 *)
@@ -133,7 +133,7 @@ noeq type toType_t (self t : Type0) = { to_type : self -> result t; }
 (** [traits::{(traits::ToType<bool> for u64)#5}::to_type]:
     Source: 'src/traits.rs', lines 93:4-93:28 *)
 let toTypeU64Bool_to_type (self : u64) : result bool =
-  Return (self > 0)
+  Ok (self > 0)
 
 (** Trait implementation: [traits::{(traits::ToType<bool> for u64)#5}]
     Source: 'src/traits.rs', lines 92:0-92:25 *)
@@ -188,7 +188,7 @@ noeq type testType_test_TestTrait_t (self : Type0) = {
     Source: 'src/traits.rs', lines 139:12-139:34 *)
 let testType_test_TestTraittraitsTestTypetestTestType1_test
   (self : testType_test_TestType1_t) : result bool =
-  Return (self > 1)
+  Ok (self > 1)
 
 (** Trait implementation: [traits::{traits::TestType<T>#6}::test::{(traits::{traits::TestType<T>#6}::test::TestTrait for traits::{traits::TestType<T>#6}::test::TestType1)}]
     Source: 'src/traits.rs', lines 138:8-138:36 *)
@@ -206,7 +206,7 @@ let testType_test
   let* x1 = toU64Inst.to_u64 x in
   if x1 > 0
   then testType_test_TestTraittraitsTestTypetestTestType1_test 0
-  else Return false
+  else Ok false
 
 (** [traits::BoolWrapper]
     Source: 'src/traits.rs', lines 150:0-150:22 *)
@@ -231,7 +231,7 @@ let toTypetraitsBoolWrapperT (t : Type0) (toTypeBoolTInst : toType_t bool t) :
     Source: 'src/traits.rs', lines 164:4-164:21 *)
 let with_const_ty_len2_default_body (self : Type0) (len : usize)
   : result usize =
-  Return 32
+  Ok 32
 let with_const_ty_len2_default (self : Type0) (len : usize) : usize =
   eval_global (with_const_ty_len2_default_body self len)
 
@@ -248,14 +248,14 @@ noeq type withConstTy_t (self : Type0) (len : usize) = {
 
 (** [traits::{(traits::WithConstTy<32: usize> for bool)#8}::LEN1]
     Source: 'src/traits.rs', lines 175:4-175:21 *)
-let with_const_ty_bool32_len1_body : result usize = Return 12
+let with_const_ty_bool32_len1_body : result usize = Ok 12
 let with_const_ty_bool32_len1 : usize =
   eval_global with_const_ty_bool32_len1_body
 
 (** [traits::{(traits::WithConstTy<32: usize> for bool)#8}::f]:
     Source: 'src/traits.rs', lines 180:4-180:39 *)
 let withConstTyBool32_f (i : u64) (a : array u8 32) : result u64 =
-  Return i
+  Ok i
 
 (** Trait implementation: [traits::{(traits::WithConstTy<32: usize> for bool)#8}]
     Source: 'src/traits.rs', lines 174:0-174:29 *)
@@ -274,7 +274,7 @@ let use_with_const_ty1
   (h : Type0) (len : usize) (withConstTyInst : withConstTy_t h len) :
   result usize
   =
-  Return withConstTyInst.cLEN1
+  Ok withConstTyInst.cLEN1
 
 (** [traits::use_with_const_ty2]:
     Source: 'src/traits.rs', lines 187:0-187:73 *)
@@ -283,7 +283,7 @@ let use_with_const_ty2
   (w : withConstTyInst.tW) :
   result unit
   =
-  Return ()
+  Ok ()
 
 (** [traits::use_with_const_ty3]:
     Source: 'src/traits.rs', lines 189:0-189:80 *)
@@ -297,7 +297,7 @@ let use_with_const_ty3
 (** [traits::test_where1]:
     Source: 'src/traits.rs', lines 193:0-193:40 *)
 let test_where1 (t : Type0) (_x : t) : result unit =
-  Return ()
+  Ok ()
 
 (** [traits::test_where2]:
     Source: 'src/traits.rs', lines 194:0-194:57 *)
@@ -305,7 +305,7 @@ let test_where2
   (t : Type0) (withConstTyT32Inst : withConstTy_t t 32) (_x : u32) :
   result unit
   =
-  Return ()
+  Ok ()
 
 (** Trait declaration: [traits::ParentTrait0]
     Source: 'src/traits.rs', lines 200:0-200:22 *)
@@ -347,7 +347,7 @@ let order1
   parentTrait0_t u) :
   result unit
   =
-  Return ()
+  Ok ()
 
 (** Trait declaration: [traits::ChildTrait1]
     Source: 'src/traits.rs', lines 222:0-222:35 *)
@@ -421,7 +421,7 @@ let parentTrait2U32 : parentTrait2_t u32 = {
 (** [traits::{(traits::ChildTrait2 for u32)#13}::convert]:
     Source: 'src/traits.rs', lines 273:4-273:29 *)
 let childTrait2U32_convert (x : u32) : result u32 =
-  Return x
+  Ok x
 
 (** Trait implementation: [traits::{(traits::ChildTrait2 for u32)#13}]
     Source: 'src/traits.rs', lines 272:0-272:24 *)
@@ -468,7 +468,7 @@ noeq type trait_t (self : Type0) = { cLEN : usize; }
 
 (** [traits::{(traits::Trait for @Array<T, N>)#14}::LEN]
     Source: 'src/traits.rs', lines 315:4-315:20 *)
-let trait_array_len_body (t : Type0) (n : usize) : result usize = Return n
+let trait_array_len_body (t : Type0) (n : usize) : result usize = Ok n
 let trait_array_len (t : Type0) (n : usize) : usize =
   eval_global (trait_array_len_body t n)
 
@@ -482,7 +482,7 @@ let traitArray (t : Type0) (n : usize) : trait_t (array t n) = {
     Source: 'src/traits.rs', lines 319:4-319:20 *)
 let traittraits_wrapper_len_body (t : Type0) (traitInst : trait_t t)
   : result usize =
-  Return 0
+  Ok 0
 let traittraits_wrapper_len (t : Type0) (traitInst : trait_t t) : usize =
   eval_global (traittraits_wrapper_len_body t traitInst)
 
@@ -496,7 +496,7 @@ let traittraitsWrapper (t : Type0) (traitInst : trait_t t) : trait_t (wrapper_t
 (** [traits::use_wrapper_len]:
     Source: 'src/traits.rs', lines 322:0-322:43 *)
 let use_wrapper_len (t : Type0) (traitInst : trait_t t) : result usize =
-  Return (traittraitsWrapper t traitInst).cLEN
+  Ok (traittraitsWrapper t traitInst).cLEN
 
 (** [traits::Foo]
     Source: 'src/traits.rs', lines 326:0-326:20 *)
@@ -513,7 +513,7 @@ type core_result_Result_t (t e : Type0) =
     Source: 'src/traits.rs', lines 332:4-332:33 *)
 let foo_foo_body (t u : Type0) (traitInst : trait_t t)
   : result (core_result_Result_t t i32) =
-  Return (Core_result_Result_Err 0)
+  Ok (Core_result_Result_Err 0)
 let foo_foo (t u : Type0) (traitInst : trait_t t)
   : core_result_Result_t t i32 =
   eval_global (foo_foo_body t u traitInst)
@@ -522,11 +522,11 @@ let foo_foo (t u : Type0) (traitInst : trait_t t)
     Source: 'src/traits.rs', lines 335:0-335:48 *)
 let use_foo1
   (t u : Type0) (traitInst : trait_t t) : result (core_result_Result_t t i32) =
-  Return (foo_foo t u traitInst)
+  Ok (foo_foo t u traitInst)
 
 (** [traits::use_foo2]:
     Source: 'src/traits.rs', lines 339:0-339:48 *)
 let use_foo2
   (t u : Type0) (traitInst : trait_t u) : result (core_result_Result_t u i32) =
-  Return (foo_foo u t traitInst)
+  Ok (foo_foo u t traitInst)
 
diff --git a/tests/lean/Arrays.lean b/tests/lean/Arrays.lean
index 207f31b9..d606640a 100644
--- a/tests/lean/Arrays.lean
+++ b/tests/lean/Arrays.lean
@@ -35,19 +35,19 @@ def array_to_mut_slice_
 def array_len (T : Type) (s : Array T 32#usize) : Result Usize :=
   do
   let s1 ← Array.to_slice T 32#usize s
-  Result.ret (Slice.len T s1)
+  Result.ok (Slice.len T s1)
 
 /- [arrays::shared_array_len]:
    Source: 'src/arrays.rs', lines 29:0-29:48 -/
 def shared_array_len (T : Type) (s : Array T 32#usize) : Result Usize :=
   do
   let s1 ← Array.to_slice T 32#usize s
-  Result.ret (Slice.len T s1)
+  Result.ok (Slice.len T s1)
 
 /- [arrays::shared_slice_len]:
    Source: 'src/arrays.rs', lines 33:0-33:44 -/
 def shared_slice_len (T : Type) (s : Slice T) : Result Usize :=
-  Result.ret (Slice.len T s)
+  Result.ok (Slice.len T s)
 
 /- [arrays::index_array_shared]:
    Source: 'src/arrays.rs', lines 37:0-37:57 -/
@@ -105,7 +105,7 @@ def slice_subslice_mut_
     core.slice.index.Slice.index_mut U32 (core.ops.range.Range Usize)
       (core.slice.index.SliceIndexRangeUsizeSliceTInst U32) x
       { start := y, end_ := z }
-  Result.ret (s, index_mut_back)
+  Result.ok (s, index_mut_back)
 
 /- [arrays::array_to_slice_shared_]:
    Source: 'src/arrays.rs', lines 72:0-72:54 -/
@@ -141,7 +141,7 @@ def array_subslice_mut_
       (core.ops.index.IndexMutSliceTIInst U32 (core.ops.range.Range Usize)
       (core.slice.index.SliceIndexRangeUsizeSliceTInst U32)) x
       { start := y, end_ := z }
-  Result.ret (s, index_mut_back)
+  Result.ok (s, index_mut_back)
 
 /- [arrays::index_slice_0]:
    Source: 'src/arrays.rs', lines 88:0-88:38 -/
@@ -175,37 +175,37 @@ def update_update_array
   let (_, index_mut_back1) ← Array.index_mut_usize U32 32#usize a j
   let a1 ← index_mut_back1 0#u32
   let _ ← index_mut_back a1
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::array_local_deep_copy]:
    Source: 'src/arrays.rs', lines 118:0-118:43 -/
 def array_local_deep_copy (x : Array U32 32#usize) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::take_array]:
    Source: 'src/arrays.rs', lines 122:0-122:30 -/
 def take_array (a : Array U32 2#usize) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::take_array_borrow]:
    Source: 'src/arrays.rs', lines 123:0-123:38 -/
 def take_array_borrow (a : Array U32 2#usize) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::take_slice]:
    Source: 'src/arrays.rs', lines 124:0-124:28 -/
 def take_slice (s : Slice U32) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::take_mut_slice]:
    Source: 'src/arrays.rs', lines 125:0-125:36 -/
 def take_mut_slice (s : Slice U32) : Result (Slice U32) :=
-  Result.ret s
+  Result.ok s
 
 /- [arrays::const_array]:
    Source: 'src/arrays.rs', lines 127:0-127:32 -/
 def const_array : Result (Array U32 2#usize) :=
-  Result.ret (Array.make U32 2#usize [ 0#u32, 0#u32 ])
+  Result.ok (Array.make U32 2#usize [ 0#u32, 0#u32 ])
 
 /- [arrays::const_slice]:
    Source: 'src/arrays.rs', lines 131:0-131:20 -/
@@ -213,7 +213,7 @@ def const_slice : Result Unit :=
   do
   let _ ←
     Array.to_slice U32 2#usize (Array.make U32 2#usize [ 0#u32, 0#u32 ])
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::take_all]:
    Source: 'src/arrays.rs', lines 141:0-141:17 -/
@@ -229,7 +229,7 @@ def take_all : Result Unit :=
     Array.to_slice_mut U32 2#usize (Array.make U32 2#usize [ 0#u32, 0#u32 ])
   let s2 ← take_mut_slice s1
   let _ ← to_slice_mut_back s2
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::index_array]:
    Source: 'src/arrays.rs', lines 155:0-155:38 -/
@@ -251,7 +251,7 @@ def index_slice_u32_0 (x : Slice U32) : Result U32 :=
 def index_mut_slice_u32_0 (x : Slice U32) : Result (U32 × (Slice U32)) :=
   do
   let i ← Slice.index_usize U32 x 0#usize
-  Result.ret (i, x)
+  Result.ok (i, x)
 
 /- [arrays::index_all]:
    Source: 'src/arrays.rs', lines 170:0-170:25 -/
@@ -271,7 +271,7 @@ def index_all : Result U32 :=
   let (i7, s2) ← index_mut_slice_u32_0 s1
   let i8 ← i6 + i7
   let _ ← to_slice_mut_back s2
-  Result.ret i8
+  Result.ok i8
 
 /- [arrays::update_array]:
    Source: 'src/arrays.rs', lines 184:0-184:36 -/
@@ -279,7 +279,7 @@ def update_array (x : Array U32 2#usize) : Result Unit :=
   do
   let (_, index_mut_back) ← Array.index_mut_usize U32 2#usize x 0#usize
   let _ ← index_mut_back 1#u32
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::update_array_mut_borrow]:
    Source: 'src/arrays.rs', lines 187:0-187:48 -/
@@ -306,7 +306,7 @@ def update_all : Result Unit :=
   let (s, to_slice_mut_back) ← Array.to_slice_mut U32 2#usize x
   let s1 ← update_mut_slice s
   let _ ← to_slice_mut_back s1
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::range_all]:
    Source: 'src/arrays.rs', lines 205:0-205:18 -/
@@ -320,7 +320,7 @@ def range_all : Result Unit :=
       { start := 1#usize, end_ := 3#usize }
   let s1 ← update_mut_slice s
   let _ ← index_mut_back s1
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::deref_array_borrow]:
    Source: 'src/arrays.rs', lines 214:0-214:46 -/
@@ -333,12 +333,12 @@ def deref_array_mut_borrow
   (x : Array U32 2#usize) : Result (U32 × (Array U32 2#usize)) :=
   do
   let i ← Array.index_usize U32 2#usize x 0#usize
-  Result.ret (i, x)
+  Result.ok (i, x)
 
 /- [arrays::take_array_t]:
    Source: 'src/arrays.rs', lines 227:0-227:31 -/
 def take_array_t (a : Array AB 2#usize) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::non_copyable_array]:
    Source: 'src/arrays.rs', lines 229:0-229:27 -/
@@ -356,7 +356,7 @@ divergent def sum_loop (s : Slice U32) (sum1 : U32) (i : Usize) : Result U32 :=
     let sum3 ← sum1 + i2
     let i3 ← i + 1#usize
     sum_loop s sum3 i3
-  else Result.ret sum1
+  else Result.ok sum1
 
 /- [arrays::sum]:
    Source: 'src/arrays.rs', lines 242:0-242:28 -/
@@ -377,7 +377,7 @@ divergent def sum2_loop
     let sum3 ← sum1 + i4
     let i5 ← i + 1#usize
     sum2_loop s s2 sum3 i5
-  else Result.ret sum1
+  else Result.ok sum1
 
 /- [arrays::sum2]:
    Source: 'src/arrays.rs', lines 252:0-252:41 -/
@@ -397,7 +397,7 @@ def f0 : Result Unit :=
   let (_, index_mut_back) ← Slice.index_mut_usize U32 s 0#usize
   let s1 ← index_mut_back 1#u32
   let _ ← to_slice_mut_back s1
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::f1]:
    Source: 'src/arrays.rs', lines 268:0-268:11 -/
@@ -407,12 +407,12 @@ def f1 : Result Unit :=
     Array.index_mut_usize U32 2#usize (Array.make U32 2#usize [ 1#u32, 2#u32 ])
       0#usize
   let _ ← index_mut_back 1#u32
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::f2]:
    Source: 'src/arrays.rs', lines 273:0-273:17 -/
 def f2 (i : U32) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::f4]:
    Source: 'src/arrays.rs', lines 282:0-282:54 -/
@@ -438,7 +438,7 @@ def f3 : Result U32 :=
 
 /- [arrays::SZ]
    Source: 'src/arrays.rs', lines 286:0-286:19 -/
-def SZ_body : Result Usize := Result.ret 32#usize
+def SZ_body : Result Usize := Result.ok 32#usize
 def SZ : Usize := eval_global SZ_body
 
 /- [arrays::f5]:
@@ -458,7 +458,7 @@ def ite : Result Unit :=
   let (_, s3) ← index_mut_slice_u32_0 s2
   let _ ← to_slice_mut_back1 s3
   let _ ← to_slice_mut_back s1
-  Result.ret ()
+  Result.ok ()
 
 /- [arrays::zero_slice]: loop 0:
    Source: 'src/arrays.rs', lines 303:0-310:1 -/
@@ -471,7 +471,7 @@ divergent def zero_slice_loop
     let i1 ← i + 1#usize
     let a1 ← index_mut_back 0#u8
     zero_slice_loop a1 i1 len
-  else Result.ret a
+  else Result.ok a
 
 /- [arrays::zero_slice]:
    Source: 'src/arrays.rs', lines 303:0-303:31 -/
@@ -486,7 +486,7 @@ divergent def iter_mut_slice_loop (len : Usize) (i : Usize) : Result Unit :=
   then do
        let i1 ← i + 1#usize
        iter_mut_slice_loop len i1
-  else Result.ret ()
+  else Result.ok ()
 
 /- [arrays::iter_mut_slice]:
    Source: 'src/arrays.rs', lines 312:0-312:35 -/
@@ -494,7 +494,7 @@ def iter_mut_slice (a : Slice U8) : Result (Slice U8) :=
   do
   let len := Slice.len U8 a
   let _ ← iter_mut_slice_loop len 0#usize
-  Result.ret a
+  Result.ok a
 
 /- [arrays::sum_mut_slice]: loop 0:
    Source: 'src/arrays.rs', lines 320:0-328:1 -/
@@ -508,13 +508,13 @@ divergent def sum_mut_slice_loop
     let s1 ← s + i2
     let i3 ← i + 1#usize
     sum_mut_slice_loop a i3 s1
-  else Result.ret s
+  else Result.ok s
 
 /- [arrays::sum_mut_slice]:
    Source: 'src/arrays.rs', lines 320:0-320:42 -/
 def sum_mut_slice (a : Slice U32) : Result (U32 × (Slice U32)) :=
   do
   let i ← sum_mut_slice_loop a 0#usize 0#u32
-  Result.ret (i, a)
+  Result.ok (i, a)
 
 end arrays
diff --git a/tests/lean/BetreeMain/Funs.lean b/tests/lean/BetreeMain/Funs.lean
index 2fbcd6a4..0c31b9bc 100644
--- a/tests/lean/BetreeMain/Funs.lean
+++ b/tests/lean/BetreeMain/Funs.lean
@@ -42,12 +42,12 @@ def betree.store_leaf_node
 def betree.fresh_node_id (counter : U64) : Result (U64 × U64) :=
   do
   let counter1 ← counter + 1#u64
-  Result.ret (counter, counter1)
+  Result.ok (counter, counter1)
 
 /- [betree_main::betree::{betree_main::betree::NodeIdCounter}::new]:
    Source: 'src/betree.rs', lines 206:4-206:20 -/
 def betree.NodeIdCounter.new : Result betree.NodeIdCounter :=
-  Result.ret { next_node_id := 0#u64 }
+  Result.ok { next_node_id := 0#u64 }
 
 /- [betree_main::betree::{betree_main::betree::NodeIdCounter}::fresh_id]:
    Source: 'src/betree.rs', lines 210:4-210:36 -/
@@ -55,7 +55,7 @@ def betree.NodeIdCounter.fresh_id
   (self : betree.NodeIdCounter) : Result (U64 × betree.NodeIdCounter) :=
   do
   let i ← self.next_node_id + 1#u64
-  Result.ret (self.next_node_id, { next_node_id := i })
+  Result.ok (self.next_node_id, { next_node_id := i })
 
 /- [betree_main::betree::upsert_update]:
    Source: 'src/betree.rs', lines 234:0-234:70 -/
@@ -64,8 +64,8 @@ def betree.upsert_update
   match prev with
   | none =>
     match st with
-    | betree.UpsertFunState.Add v => Result.ret v
-    | betree.UpsertFunState.Sub _ => Result.ret 0#u64
+    | betree.UpsertFunState.Add v => Result.ok v
+    | betree.UpsertFunState.Sub _ => Result.ok 0#u64
   | some prev1 =>
     match st with
     | betree.UpsertFunState.Add v =>
@@ -73,11 +73,11 @@ def betree.upsert_update
       let margin ← core_u64_max - prev1
       if margin >= v
       then prev1 + v
-      else Result.ret core_u64_max
+      else Result.ok core_u64_max
     | betree.UpsertFunState.Sub v =>
       if prev1 >= v
       then prev1 - v
-      else Result.ret 0#u64
+      else Result.ok 0#u64
 
 /- [betree_main::betree::{betree_main::betree::List<T>#1}::len]:
    Source: 'src/betree.rs', lines 276:4-276:24 -/
@@ -86,7 +86,7 @@ divergent def betree.List.len (T : Type) (self : betree.List T) : Result U64 :=
   | betree.List.Cons _ tl => do
                              let i ← betree.List.len T tl
                              1#u64 + i
-  | betree.List.Nil => Result.ret 0#u64
+  | betree.List.Nil => Result.ok 0#u64
 
 /- [betree_main::betree::{betree_main::betree::List<T>#1}::split_at]:
    Source: 'src/betree.rs', lines 284:4-284:51 -/
@@ -95,7 +95,7 @@ divergent def betree.List.split_at
   Result ((betree.List T) × (betree.List T))
   :=
   if n = 0#u64
-  then Result.ret (betree.List.Nil, self)
+  then Result.ok (betree.List.Nil, self)
   else
     match self with
     | betree.List.Cons hd tl =>
@@ -103,7 +103,7 @@ divergent def betree.List.split_at
       let i ← n - 1#u64
       let p ← betree.List.split_at T tl i
       let (ls0, ls1) := p
-      Result.ret (betree.List.Cons hd ls0, ls1)
+      Result.ok (betree.List.Cons hd ls0, ls1)
     | betree.List.Nil => Result.fail .panic
 
 /- [betree_main::betree::{betree_main::betree::List<T>#1}::push_front]:
@@ -111,7 +111,7 @@ divergent def betree.List.split_at
 def betree.List.push_front
   (T : Type) (self : betree.List T) (x : T) : Result (betree.List T) :=
   let (tl, _) := core.mem.replace (betree.List T) self betree.List.Nil
-  Result.ret (betree.List.Cons x tl)
+  Result.ok (betree.List.Cons x tl)
 
 /- [betree_main::betree::{betree_main::betree::List<T>#1}::pop_front]:
    Source: 'src/betree.rs', lines 306:4-306:32 -/
@@ -119,14 +119,14 @@ def betree.List.pop_front
   (T : Type) (self : betree.List T) : Result (T × (betree.List T)) :=
   let (ls, _) := core.mem.replace (betree.List T) self betree.List.Nil
   match ls with
-  | betree.List.Cons x tl => Result.ret (x, tl)
+  | betree.List.Cons x tl => Result.ok (x, tl)
   | betree.List.Nil => Result.fail .panic
 
 /- [betree_main::betree::{betree_main::betree::List<T>#1}::hd]:
    Source: 'src/betree.rs', lines 318:4-318:22 -/
 def betree.List.hd (T : Type) (self : betree.List T) : Result T :=
   match self with
-  | betree.List.Cons hd _ => Result.ret hd
+  | betree.List.Cons hd _ => Result.ok hd
   | betree.List.Nil => Result.fail .panic
 
 /- [betree_main::betree::{betree_main::betree::List<(u64, T)>#2}::head_has_key]:
@@ -135,8 +135,8 @@ def betree.ListPairU64T.head_has_key
   (T : Type) (self : betree.List (U64 × T)) (key : U64) : Result Bool :=
   match self with
   | betree.List.Cons hd _ => let (i, _) := hd
-                             Result.ret (i = key)
-  | betree.List.Nil => Result.ret false
+                             Result.ok (i = key)
+  | betree.List.Nil => Result.ok false
 
 /- [betree_main::betree::{betree_main::betree::List<(u64, T)>#2}::partition_at_pivot]:
    Source: 'src/betree.rs', lines 339:4-339:73 -/
@@ -148,13 +148,13 @@ divergent def betree.ListPairU64T.partition_at_pivot
   | betree.List.Cons hd tl =>
     let (i, t) := hd
     if i >= pivot
-    then Result.ret (betree.List.Nil, betree.List.Cons (i, t) tl)
+    then Result.ok (betree.List.Nil, betree.List.Cons (i, t) tl)
     else
       do
       let p ← betree.ListPairU64T.partition_at_pivot T tl pivot
       let (ls0, ls1) := p
-      Result.ret (betree.List.Cons (i, t) ls0, ls1)
-  | betree.List.Nil => Result.ret (betree.List.Nil, betree.List.Nil)
+      Result.ok (betree.List.Cons (i, t) ls0, ls1)
+  | betree.List.Nil => Result.ok (betree.List.Nil, betree.List.Nil)
 
 /- [betree_main::betree::{betree_main::betree::Leaf#3}::split]:
    Source: 'src/betree.rs', lines 359:4-364:17 -/
@@ -174,7 +174,7 @@ def betree.Leaf.split
   let (st2, _) ← betree.store_leaf_node id1 content1 st1
   let n := betree.Node.Leaf { id := id0, size := params.split_size }
   let n1 := betree.Node.Leaf { id := id1, size := params.split_size }
-  Result.ret (st2, (betree.Internal.mk self.id pivot n n1, node_id_cnt2))
+  Result.ok (st2, (betree.Internal.mk self.id pivot n n1, node_id_cnt2))
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_for_key]:
    Source: 'src/betree.rs', lines 789:4-792:34 -/
@@ -187,7 +187,7 @@ divergent def betree.Node.lookup_first_message_for_key
   | betree.List.Cons x next_msgs =>
     let (i, m) := x
     if i >= key
-    then Result.ret (betree.List.Cons (i, m) next_msgs, Result.ret)
+    then Result.ok (betree.List.Cons (i, m) next_msgs, Result.ok)
     else
       do
       let (l, lookup_first_message_for_key_back) ←
@@ -196,9 +196,9 @@ divergent def betree.Node.lookup_first_message_for_key
         fun ret =>
           do
           let next_msgs1 ← lookup_first_message_for_key_back ret
-          Result.ret (betree.List.Cons (i, m) next_msgs1)
-      Result.ret (l, back)
-  | betree.List.Nil => Result.ret (betree.List.Nil, Result.ret)
+          Result.ok (betree.List.Cons (i, m) next_msgs1)
+      Result.ok (l, back)
+  | betree.List.Nil => Result.ok (betree.List.Nil, Result.ok)
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::lookup_in_bindings]:
    Source: 'src/betree.rs', lines 636:4-636:80 -/
@@ -208,12 +208,12 @@ divergent def betree.Node.lookup_in_bindings
   | betree.List.Cons hd tl =>
     let (i, i1) := hd
     if i = key
-    then Result.ret (some i1)
+    then Result.ok (some i1)
     else
       if i > key
-      then Result.ret none
+      then Result.ok none
       else betree.Node.lookup_in_bindings key tl
-  | betree.List.Nil => Result.ret none
+  | betree.List.Nil => Result.ok none
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::apply_upserts]:
    Source: 'src/betree.rs', lines 819:4-819:90 -/
@@ -242,7 +242,7 @@ divergent def betree.Node.apply_upserts
     let msgs1 ←
       betree.List.push_front (U64 × betree.Message) msgs (key,
         betree.Message.Insert v)
-    Result.ret (st1, (v, msgs1))
+    Result.ok (st1, (v, msgs1))
 
 /- [betree_main::betree::{betree_main::betree::Internal#4}::lookup_in_children]:
    Source: 'src/betree.rs', lines 395:4-395:63 -/
@@ -255,11 +255,11 @@ mutual divergent def betree.Internal.lookup_in_children
   then
     do
     let (st1, (o, n2)) ← betree.Node.lookup n key st
-    Result.ret (st1, (o, betree.Internal.mk i i1 n2 n1))
+    Result.ok (st1, (o, betree.Internal.mk i i1 n2 n1))
   else
     do
     let (st1, (o, n2)) ← betree.Node.lookup n1 key st
-    Result.ret (st1, (o, betree.Internal.mk i i1 n n2))
+    Result.ok (st1, (o, betree.Internal.mk i i1 n n2))
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::lookup]:
    Source: 'src/betree.rs', lines 709:4-709:58 -/
@@ -285,7 +285,7 @@ divergent def betree.Node.lookup
             st1
         let _ ←
           lookup_first_message_for_key_back (betree.List.Cons (k, msg) l)
-        Result.ret (st2, (o, betree.Node.Internal node1))
+        Result.ok (st2, (o, betree.Node.Internal node1))
       else
         match msg with
         | betree.Message.Insert v =>
@@ -293,14 +293,14 @@ divergent def betree.Node.lookup
           let _ ←
             lookup_first_message_for_key_back (betree.List.Cons (k,
               betree.Message.Insert v) l)
-          Result.ret (st1, (some v, betree.Node.Internal (betree.Internal.mk i
+          Result.ok (st1, (some v, betree.Node.Internal (betree.Internal.mk i
             i1 n n1)))
         | betree.Message.Delete =>
           do
           let _ ←
             lookup_first_message_for_key_back (betree.List.Cons (k,
               betree.Message.Delete) l)
-          Result.ret (st1, (none, betree.Node.Internal (betree.Internal.mk i i1
+          Result.ok (st1, (none, betree.Node.Internal (betree.Internal.mk i i1
             n n1)))
         | betree.Message.Upsert ufs =>
           do
@@ -313,20 +313,20 @@ divergent def betree.Node.lookup
           let ⟨ i2, i3, n2, n3 ⟩ := node1
           let msgs1 ← lookup_first_message_for_key_back pending1
           let (st4, _) ← betree.store_internal_node i2 msgs1 st3
-          Result.ret (st4, (some v1, betree.Node.Internal (betree.Internal.mk
-            i2 i3 n2 n3)))
+          Result.ok (st4, (some v1, betree.Node.Internal (betree.Internal.mk i2
+            i3 n2 n3)))
     | betree.List.Nil =>
       do
       let (st2, (o, node1)) ←
         betree.Internal.lookup_in_children (betree.Internal.mk i i1 n n1) key
           st1
       let _ ← lookup_first_message_for_key_back betree.List.Nil
-      Result.ret (st2, (o, betree.Node.Internal node1))
+      Result.ok (st2, (o, betree.Node.Internal node1))
   | betree.Node.Leaf node =>
     do
     let (st1, bindings) ← betree.load_leaf_node node.id st
     let o ← betree.Node.lookup_in_bindings key bindings
-    Result.ret (st1, (o, betree.Node.Leaf node))
+    Result.ok (st1, (o, betree.Node.Leaf node))
 
 end
 
@@ -346,8 +346,8 @@ divergent def betree.Node.filter_messages_for_key
         betree.List.pop_front (U64 × betree.Message) (betree.List.Cons (k, m)
           l)
       betree.Node.filter_messages_for_key key msgs1
-    else Result.ret (betree.List.Cons (k, m) l)
-  | betree.List.Nil => Result.ret betree.List.Nil
+    else Result.ok (betree.List.Cons (k, m) l)
+  | betree.List.Nil => Result.ok betree.List.Nil
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::lookup_first_message_after_key]:
    Source: 'src/betree.rs', lines 689:4-692:34 -/
@@ -368,10 +368,10 @@ divergent def betree.Node.lookup_first_message_after_key
         fun ret =>
           do
           let next_msgs1 ← lookup_first_message_after_key_back ret
-          Result.ret (betree.List.Cons (k, m) next_msgs1)
-      Result.ret (l, back)
-    else Result.ret (betree.List.Cons (k, m) next_msgs, Result.ret)
-  | betree.List.Nil => Result.ret (betree.List.Nil, Result.ret)
+          Result.ok (betree.List.Cons (k, m) next_msgs1)
+      Result.ok (l, back)
+    else Result.ok (betree.List.Cons (k, m) next_msgs, Result.ok)
+  | betree.List.Nil => Result.ok (betree.List.Nil, Result.ok)
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::apply_to_internal]:
    Source: 'src/betree.rs', lines 521:4-521:89 -/
@@ -450,7 +450,7 @@ divergent def betree.Node.apply_messages_to_internal
     let (i, m) := new_msg
     let msgs1 ← betree.Node.apply_to_internal msgs i m
     betree.Node.apply_messages_to_internal msgs1 new_msgs_tl
-  | betree.List.Nil => Result.ret msgs
+  | betree.List.Nil => Result.ok msgs
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::lookup_mut_in_bindings]:
    Source: 'src/betree.rs', lines 653:4-656:32 -/
@@ -463,7 +463,7 @@ divergent def betree.Node.lookup_mut_in_bindings
   | betree.List.Cons hd tl =>
     let (i, i1) := hd
     if i >= key
-    then Result.ret (betree.List.Cons (i, i1) tl, Result.ret)
+    then Result.ok (betree.List.Cons (i, i1) tl, Result.ok)
     else
       do
       let (l, lookup_mut_in_bindings_back) ←
@@ -472,9 +472,9 @@ divergent def betree.Node.lookup_mut_in_bindings
         fun ret =>
           do
           let tl1 ← lookup_mut_in_bindings_back ret
-          Result.ret (betree.List.Cons (i, i1) tl1)
-      Result.ret (l, back)
-  | betree.List.Nil => Result.ret (betree.List.Nil, Result.ret)
+          Result.ok (betree.List.Cons (i, i1) tl1)
+      Result.ok (l, back)
+  | betree.List.Nil => Result.ok (betree.List.Nil, Result.ok)
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::apply_to_leaf]:
    Source: 'src/betree.rs', lines 460:4-460:87 -/
@@ -529,7 +529,7 @@ divergent def betree.Node.apply_messages_to_leaf
     let (i, m) := new_msg
     let bindings1 ← betree.Node.apply_to_leaf bindings i m
     betree.Node.apply_messages_to_leaf bindings1 new_msgs_tl
-  | betree.List.Nil => Result.ret bindings
+  | betree.List.Nil => Result.ok bindings
 
 /- [betree_main::betree::{betree_main::betree::Internal#4}::flush]:
    Source: 'src/betree.rs', lines 410:4-415:26 -/
@@ -558,17 +558,17 @@ mutual divergent def betree.Internal.flush
       let (st2, p2) ←
         betree.Node.apply_messages n1 params node_id_cnt1 msgs_right st1
       let (n3, node_id_cnt2) := p2
-      Result.ret (st2, (betree.List.Nil, (betree.Internal.mk i i1 n2 n3,
+      Result.ok (st2, (betree.List.Nil, (betree.Internal.mk i i1 n2 n3,
         node_id_cnt2)))
     else
-      Result.ret (st1, (msgs_right, (betree.Internal.mk i i1 n2 n1,
+      Result.ok (st1, (msgs_right, (betree.Internal.mk i i1 n2 n1,
         node_id_cnt1)))
   else
     do
     let (st1, p1) ←
       betree.Node.apply_messages n1 params node_id_cnt msgs_right st
     let (n2, node_id_cnt1) := p1
-    Result.ret (st1, (msgs_left, (betree.Internal.mk i i1 n n2, node_id_cnt1)))
+    Result.ok (st1, (msgs_left, (betree.Internal.mk i i1 n n2, node_id_cnt1)))
 
 /- [betree_main::betree::{betree_main::betree::Node#5}::apply_messages]:
    Source: 'src/betree.rs', lines 588:4-593:5 -/
@@ -594,12 +594,12 @@ divergent def betree.Node.apply_messages
       let (node1, node_id_cnt1) := p
       let ⟨ i2, i3, n2, n3 ⟩ := node1
       let (st3, _) ← betree.store_internal_node i2 content2 st2
-      Result.ret (st3, (betree.Node.Internal (betree.Internal.mk i2 i3 n2 n3),
+      Result.ok (st3, (betree.Node.Internal (betree.Internal.mk i2 i3 n2 n3),
         node_id_cnt1))
     else
       do
       let (st2, _) ← betree.store_internal_node i content1 st1
-      Result.ret (st2, (betree.Node.Internal (betree.Internal.mk i i1 n n1),
+      Result.ok (st2, (betree.Node.Internal (betree.Internal.mk i i1 n n1),
         node_id_cnt))
   | betree.Node.Leaf node =>
     do
@@ -613,11 +613,11 @@ divergent def betree.Node.apply_messages
       let (st2, (new_node, node_id_cnt1)) ←
         betree.Leaf.split node content1 params node_id_cnt st1
       let (st3, _) ← betree.store_leaf_node node.id betree.List.Nil st2
-      Result.ret (st3, (betree.Node.Internal new_node, node_id_cnt1))
+      Result.ok (st3, (betree.Node.Internal new_node, node_id_cnt1))
     else
       do
       let (st2, _) ← betree.store_leaf_node node.id content1 st1
-      Result.ret (st2, (betree.Node.Leaf { node with size := len },
+      Result.ok (st2, (betree.Node.Leaf { node with size := len },
         node_id_cnt))
 
 end
@@ -635,7 +635,7 @@ def betree.Node.apply
     betree.Node.apply_messages self params node_id_cnt (betree.List.Cons (key,
       new_msg) betree.List.Nil) st
   let (self1, node_id_cnt1) := p
-  Result.ret (st1, (self1, node_id_cnt1))
+  Result.ok (st1, (self1, node_id_cnt1))
 
 /- [betree_main::betree::{betree_main::betree::BeTree#6}::new]:
    Source: 'src/betree.rs', lines 849:4-849:60 -/
@@ -647,7 +647,7 @@ def betree.BeTree.new
   let node_id_cnt ← betree.NodeIdCounter.new
   let (id, node_id_cnt1) ← betree.NodeIdCounter.fresh_id node_id_cnt
   let (st1, _) ← betree.store_leaf_node id betree.List.Nil st
-  Result.ret (st1,
+  Result.ok (st1,
     {
       params := { min_flush_size := min_flush_size, split_size := split_size },
       node_id_cnt := node_id_cnt1,
@@ -664,7 +664,7 @@ def betree.BeTree.apply
   let (st1, p) ←
     betree.Node.apply self.root self.params self.node_id_cnt key msg st
   let (n, nic) := p
-  Result.ret (st1, { self with node_id_cnt := nic, root := n })
+  Result.ok (st1, { self with node_id_cnt := nic, root := n })
 
 /- [betree_main::betree::{betree_main::betree::BeTree#6}::insert]:
    Source: 'src/betree.rs', lines 874:4-874:52 -/
@@ -699,14 +699,14 @@ def betree.BeTree.lookup
   :=
   do
   let (st1, (o, n)) ← betree.Node.lookup self.root key st
-  Result.ret (st1, (o, { self with root := n }))
+  Result.ok (st1, (o, { self with root := n }))
 
 /- [betree_main::main]:
    Source: 'src/betree_main.rs', lines 5:0-5:9 -/
 def main : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- Unit test for [betree_main::main] -/
-#assert (main == Result.ret ())
+#assert (main == Result.ok ())
 
 end betree_main
diff --git a/tests/lean/Bitwise.lean b/tests/lean/Bitwise.lean
index 7c47e3dd..c13129f1 100644
--- a/tests/lean/Bitwise.lean
+++ b/tests/lean/Bitwise.lean
@@ -22,16 +22,16 @@ def shift_i32 (a : I32) : Result I32 :=
 /- [bitwise::xor_u32]:
    Source: 'src/bitwise.rs', lines 17:0-17:37 -/
 def xor_u32 (a : U32) (b : U32) : Result U32 :=
-  Result.ret (a ^^^ b)
+  Result.ok (a ^^^ b)
 
 /- [bitwise::or_u32]:
    Source: 'src/bitwise.rs', lines 21:0-21:36 -/
 def or_u32 (a : U32) (b : U32) : Result U32 :=
-  Result.ret (a ||| b)
+  Result.ok (a ||| b)
 
 /- [bitwise::and_u32]:
    Source: 'src/bitwise.rs', lines 25:0-25:37 -/
 def and_u32 (a : U32) (b : U32) : Result U32 :=
-  Result.ret (a &&& b)
+  Result.ok (a &&& b)
 
 end bitwise
diff --git a/tests/lean/Constants.lean b/tests/lean/Constants.lean
index 40f590d4..3cc3ca40 100644
--- a/tests/lean/Constants.lean
+++ b/tests/lean/Constants.lean
@@ -7,17 +7,17 @@ namespace constants
 
 /- [constants::X0]
    Source: 'src/constants.rs', lines 5:0-5:17 -/
-def X0_body : Result U32 := Result.ret 0#u32
+def X0_body : Result U32 := Result.ok 0#u32
 def X0 : U32 := eval_global X0_body
 
 /- [constants::X1]
    Source: 'src/constants.rs', lines 7:0-7:17 -/
-def X1_body : Result U32 := Result.ret core_u32_max
+def X1_body : Result U32 := Result.ok core_u32_max
 def X1 : U32 := eval_global X1_body
 
 /- [constants::X2]
    Source: 'src/constants.rs', lines 10:0-10:17 -/
-def X2_body : Result U32 := Result.ret 3#u32
+def X2_body : Result U32 := Result.ok 3#u32
 def X2 : U32 := eval_global X2_body
 
 /- [constants::incr]:
@@ -33,7 +33,7 @@ def X3 : U32 := eval_global X3_body
 /- [constants::mk_pair0]:
    Source: 'src/constants.rs', lines 23:0-23:51 -/
 def mk_pair0 (x : U32) (y : U32) : Result (U32 × U32) :=
-  Result.ret (x, y)
+  Result.ok (x, y)
 
 /- [constants::Pair]
    Source: 'src/constants.rs', lines 36:0-36:23 -/
@@ -44,7 +44,7 @@ structure Pair (T1 T2 : Type) where
 /- [constants::mk_pair1]:
    Source: 'src/constants.rs', lines 27:0-27:55 -/
 def mk_pair1 (x : U32) (y : U32) : Result (Pair U32 U32) :=
-  Result.ret { x := x, y := y }
+  Result.ok { x := x, y := y }
 
 /- [constants::P0]
    Source: 'src/constants.rs', lines 31:0-31:24 -/
@@ -58,12 +58,12 @@ def P1 : Pair U32 U32 := eval_global P1_body
 
 /- [constants::P2]
    Source: 'src/constants.rs', lines 33:0-33:24 -/
-def P2_body : Result (U32 × U32) := Result.ret (0#u32, 1#u32)
+def P2_body : Result (U32 × U32) := Result.ok (0#u32, 1#u32)
 def P2 : (U32 × U32) := eval_global P2_body
 
 /- [constants::P3]
    Source: 'src/constants.rs', lines 34:0-34:28 -/
-def P3_body : Result (Pair U32 U32) := Result.ret { x := 0#u32, y := 1#u32 }
+def P3_body : Result (Pair U32 U32) := Result.ok { x := 0#u32, y := 1#u32 }
 def P3 : Pair U32 U32 := eval_global P3_body
 
 /- [constants::Wrap]
@@ -74,7 +74,7 @@ structure Wrap (T : Type) where
 /- [constants::{constants::Wrap<T>}::new]:
    Source: 'src/constants.rs', lines 54:4-54:41 -/
 def Wrap.new (T : Type) (value : T) : Result (Wrap T) :=
-  Result.ret { value := value }
+  Result.ok { value := value }
 
 /- [constants::Y]
    Source: 'src/constants.rs', lines 41:0-41:22 -/
@@ -84,7 +84,7 @@ def Y : Wrap I32 := eval_global Y_body
 /- [constants::unwrap_y]:
    Source: 'src/constants.rs', lines 43:0-43:30 -/
 def unwrap_y : Result I32 :=
-  Result.ret Y.value
+  Result.ok Y.value
 
 /- [constants::YVAL]
    Source: 'src/constants.rs', lines 47:0-47:19 -/
@@ -93,13 +93,13 @@ def YVAL : I32 := eval_global YVAL_body
 
 /- [constants::get_z1::Z1]
    Source: 'src/constants.rs', lines 62:4-62:17 -/
-def get_z1.Z1_body : Result I32 := Result.ret 3#i32
+def get_z1.Z1_body : Result I32 := Result.ok 3#i32
 def get_z1.Z1 : I32 := eval_global get_z1.Z1_body
 
 /- [constants::get_z1]:
    Source: 'src/constants.rs', lines 61:0-61:28 -/
 def get_z1 : Result I32 :=
-  Result.ret get_z1.Z1
+  Result.ok get_z1.Z1
 
 /- [constants::add]:
    Source: 'src/constants.rs', lines 66:0-66:39 -/
@@ -108,12 +108,12 @@ def add (a : I32) (b : I32) : Result I32 :=
 
 /- [constants::Q1]
    Source: 'src/constants.rs', lines 74:0-74:17 -/
-def Q1_body : Result I32 := Result.ret 5#i32
+def Q1_body : Result I32 := Result.ok 5#i32
 def Q1 : I32 := eval_global Q1_body
 
 /- [constants::Q2]
    Source: 'src/constants.rs', lines 75:0-75:17 -/
-def Q2_body : Result I32 := Result.ret Q1
+def Q2_body : Result I32 := Result.ok Q1
 def Q2 : I32 := eval_global Q2_body
 
 /- [constants::Q3]
@@ -131,7 +131,7 @@ def get_z2 : Result I32 :=
 
 /- [constants::S1]
    Source: 'src/constants.rs', lines 80:0-80:18 -/
-def S1_body : Result U32 := Result.ret 6#u32
+def S1_body : Result U32 := Result.ok 6#u32
 def S1 : U32 := eval_global S1_body
 
 /- [constants::S2]
@@ -141,7 +141,7 @@ def S2 : U32 := eval_global S2_body
 
 /- [constants::S3]
    Source: 'src/constants.rs', lines 82:0-82:29 -/
-def S3_body : Result (Pair U32 U32) := Result.ret P3
+def S3_body : Result (Pair U32 U32) := Result.ok P3
 def S3 : Pair U32 U32 := eval_global S3_body
 
 /- [constants::S4]
@@ -156,12 +156,12 @@ structure V (T : Type) (N : Usize) where
 
 /- [constants::{constants::V<T, N>#1}::LEN]
    Source: 'src/constants.rs', lines 91:4-91:24 -/
-def V.LEN_body (T : Type) (N : Usize) : Result Usize := Result.ret N
+def V.LEN_body (T : Type) (N : Usize) : Result Usize := Result.ok N
 def V.LEN (T : Type) (N : Usize) : Usize := eval_global (V.LEN_body T N)
 
 /- [constants::use_v]:
    Source: 'src/constants.rs', lines 94:0-94:42 -/
 def use_v (T : Type) (N : Usize) : Result Usize :=
-  Result.ret (V.LEN T N)
+  Result.ok (V.LEN T N)
 
 end constants
diff --git a/tests/lean/Demo/Demo.lean b/tests/lean/Demo/Demo.lean
index 6d9fef8e..3a3aeb96 100644
--- a/tests/lean/Demo/Demo.lean
+++ b/tests/lean/Demo/Demo.lean
@@ -12,10 +12,10 @@ def choose
   Result (T × (T → Result (T × T)))
   :=
   if b
-  then let back := fun ret => Result.ret (ret, y)
-       Result.ret (x, back)
-  else let back := fun ret => Result.ret (x, ret)
-       Result.ret (y, back)
+  then let back := fun ret => Result.ok (ret, y)
+       Result.ok (x, back)
+  else let back := fun ret => Result.ok (x, ret)
+       Result.ok (y, back)
 
 /- [demo::mul2_add1]:
    Source: 'src/demo.rs', lines 13:0-13:31 -/
@@ -43,7 +43,7 @@ def use_incr : Result Unit :=
   let x ← incr 0#u32
   let x1 ← incr x
   let _ ← incr x1
-  Result.ret ()
+  Result.ok ()
 
 /- [demo::CList]
    Source: 'src/demo.rs', lines 34:0-34:17 -/
@@ -57,7 +57,7 @@ divergent def list_nth (T : Type) (l : CList T) (i : U32) : Result T :=
   match l with
   | CList.CCons x tl =>
     if i = 0#u32
-    then Result.ret x
+    then Result.ok x
     else do
          let i1 ← i - 1#u32
          list_nth T tl i1
@@ -73,8 +73,8 @@ divergent def list_nth_mut
   | CList.CCons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (CList.CCons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (CList.CCons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -83,8 +83,8 @@ divergent def list_nth_mut
         fun ret =>
           do
           let tl1 ← list_nth_mut_back ret
-          Result.ret (CList.CCons x tl1)
-      Result.ret (t, back)
+          Result.ok (CList.CCons x tl1)
+      Result.ok (t, back)
   | CList.CNil => Result.fail .panic
 
 /- [demo::list_nth_mut1]: loop 0:
@@ -97,8 +97,8 @@ divergent def list_nth_mut1_loop
   | CList.CCons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (CList.CCons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (CList.CCons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -106,8 +106,8 @@ divergent def list_nth_mut1_loop
       let back1 :=
         fun ret => do
                    let tl1 ← back ret
-                   Result.ret (CList.CCons x tl1)
-      Result.ret (t, back1)
+                   Result.ok (CList.CCons x tl1)
+      Result.ok (t, back1)
   | CList.CNil => Result.fail .panic
 
 /- [demo::list_nth_mut1]:
@@ -122,7 +122,7 @@ def list_nth_mut1
    Source: 'src/demo.rs', lines 80:0-80:28 -/
 divergent def i32_id (i : I32) : Result I32 :=
   if i = 0#i32
-  then Result.ret 0#i32
+  then Result.ok 0#i32
   else do
        let i1 ← i - 1#i32
        let i2 ← i32_id i1
@@ -142,9 +142,9 @@ divergent def list_tail
       fun ret =>
         do
         let tl1 ← list_tail_back ret
-        Result.ret (CList.CCons t tl1)
-    Result.ret (c, back)
-  | CList.CNil => Result.ret (CList.CNil, Result.ret)
+        Result.ok (CList.CCons t tl1)
+    Result.ok (c, back)
+  | CList.CNil => Result.ok (CList.CNil, Result.ok)
 
 /- Trait declaration: [demo::Counter]
    Source: 'src/demo.rs', lines 97:0-97:17 -/
@@ -156,7 +156,7 @@ structure Counter (Self : Type) where
 def CounterUsize.incr (self : Usize) : Result (Usize × Usize) :=
   do
   let self1 ← self + 1#usize
-  Result.ret (self, self1)
+  Result.ok (self, self1)
 
 /- Trait implementation: [demo::{(demo::Counter for usize)}]
    Source: 'src/demo.rs', lines 101:0-101:22 -/
diff --git a/tests/lean/Demo/Properties.lean b/tests/lean/Demo/Properties.lean
index e514ac3e..abdc2985 100644
--- a/tests/lean/Demo/Properties.lean
+++ b/tests/lean/Demo/Properties.lean
@@ -9,7 +9,7 @@ namespace demo
 
 -- @[pspec]
 theorem mul2_add1_spec (x : U32) (h : 2 * ↑x + 1 ≤ U32.max)
-  : ∃ y, mul2_add1 x = ret y ∧
+  : ∃ y, mul2_add1 x = ok y ∧
   ↑y = 2 * ↑x + (1 : Int)
   := by
   rw [mul2_add1]
@@ -18,7 +18,7 @@ theorem mul2_add1_spec (x : U32) (h : 2 * ↑x + 1 ≤ U32.max)
   simp; scalar_tac
 
 theorem use_mul2_add1_spec (x : U32) (y : U32) (h : 2 * ↑x + 1 + ↑y ≤ U32.max) :
-  ∃ z, use_mul2_add1 x y = ret z ∧
+  ∃ z, use_mul2_add1 x y = ok z ∧
   ↑z = 2 * ↑x + (1 : Int) + ↑y := by
   rw [use_mul2_add1]
   progress with mul2_add1_spec as ⟨ i ⟩
@@ -34,7 +34,7 @@ open CList
 
 theorem list_nth_spec {T : Type} [Inhabited T] (l : CList T) (i : U32)
   (h : ↑i < l.to_list.len) :
-  ∃ x, list_nth T l i = ret x ∧
+  ∃ x, list_nth T l i = ok x ∧
   x = l.to_list.index ↑i
   := by
   rw [list_nth]
@@ -52,7 +52,7 @@ theorem list_nth_spec {T : Type} [Inhabited T] (l : CList T) (i : U32)
       simp_all
 
 theorem i32_id_spec (x : I32) (h : 0 ≤ x.val) :
-  ∃ y, i32_id x = ret y ∧ x.val = y.val := by
+  ∃ y, i32_id x = ok y ∧ x.val = y.val := by
   rw [i32_id]
   if hx : x = 0#i32 then
     simp_all
@@ -66,8 +66,8 @@ termination_by x.val.toNat
 decreasing_by scalar_decr_tac
 
 theorem list_tail_spec {T : Type} [Inhabited T] (l : CList T) :
-  ∃ back, list_tail T l = ret (CList.CNil, back) ∧
-  ∀ tl', ∃ l', back tl' = ret l' ∧ l'.to_list = l.to_list ++ tl'.to_list := by
+  ∃ back, list_tail T l = ok (CList.CNil, back) ∧
+  ∀ tl', ∃ l', back tl' = ok l' ∧ l'.to_list = l.to_list ++ tl'.to_list := by
   rw [list_tail]
   match l with
   | CNil =>
diff --git a/tests/lean/External/Funs.lean b/tests/lean/External/Funs.lean
index cfb2cb3c..78e0f95c 100644
--- a/tests/lean/External/Funs.lean
+++ b/tests/lean/External/Funs.lean
@@ -26,10 +26,10 @@ def test_new_non_zero_u32
 def test_vec : Result Unit :=
   do
   let _ ← alloc.vec.Vec.push U32 (alloc.vec.Vec.new U32) 0#u32
-  Result.ret ()
+  Result.ok ()
 
 /- Unit test for [external::test_vec] -/
-#assert (test_vec == Result.ret ())
+#assert (test_vec == Result.ok ())
 
 /- [external::custom_swap]:
    Source: 'src/external.rs', lines 24:0-24:66 -/
@@ -39,8 +39,8 @@ def custom_swap
   :=
   do
   let (st1, (x1, y1)) ← core.mem.swap T x y st
-  let back := fun ret st2 => Result.ret (st2, (ret, y1))
-  Result.ret (st1, (x1, back))
+  let back := fun ret st2 => Result.ok (st2, (ret, y1))
+  Result.ok (st1, (x1, back))
 
 /- [external::test_custom_swap]:
    Source: 'src/external.rs', lines 29:0-29:59 -/
@@ -49,7 +49,7 @@ def test_custom_swap
   do
   let (st1, (_, custom_swap_back)) ← custom_swap U32 x y st
   let (_, (x1, y1)) ← custom_swap_back 1#u32 st1
-  Result.ret (st1, (x1, y1))
+  Result.ok (st1, (x1, y1))
 
 /- [external::test_swap_non_zero]:
    Source: 'src/external.rs', lines 35:0-35:44 -/
@@ -59,6 +59,6 @@ def test_swap_non_zero (x : U32) (st : State) : Result (State × U32) :=
   let (x1, _) := p
   if x1 = 0#u32
   then Result.fail .panic
-  else Result.ret (st1, x1)
+  else Result.ok (st1, x1)
 
 end external
diff --git a/tests/lean/External/FunsExternal.lean b/tests/lean/External/FunsExternal.lean
index 63830abc..b6efc65f 100644
--- a/tests/lean/External/FunsExternal.lean
+++ b/tests/lean/External/FunsExternal.lean
@@ -9,7 +9,7 @@ open external
 /- [core::mem::swap] -/
 def core.mem.swap
   (T : Type) : T → T → State → Result (State × (T × T)) :=
-  fun x y s => .ret (s, (y, x))
+  fun x y s => .ok (s, (y, x))
 
 /- [core::num::nonzero::NonZeroU32::{14}::new] -/
 def core.num.nonzero.NonZeroU32.new :
diff --git a/tests/lean/Hashmap/Funs.lean b/tests/lean/Hashmap/Funs.lean
index 363d751a..9cbd958c 100644
--- a/tests/lean/Hashmap/Funs.lean
+++ b/tests/lean/Hashmap/Funs.lean
@@ -9,7 +9,7 @@ namespace hashmap
 /- [hashmap::hash_key]:
    Source: 'src/hashmap.rs', lines 27:0-27:32 -/
 def hash_key (k : Usize) : Result Usize :=
-  Result.ret k
+  Result.ok k
 
 /- [hashmap::{hashmap::HashMap<T>}::allocate_slots]: loop 0:
    Source: 'src/hashmap.rs', lines 50:4-56:5 -/
@@ -23,7 +23,7 @@ divergent def HashMap.allocate_slots_loop
     let slots1 ← alloc.vec.Vec.push (List T) slots List.Nil
     let n1 ← n - 1#usize
     HashMap.allocate_slots_loop T slots1 n1
-  else Result.ret slots
+  else Result.ok slots
 
 /- [hashmap::{hashmap::HashMap<T>}::allocate_slots]:
    Source: 'src/hashmap.rs', lines 50:4-50:76 -/
@@ -44,7 +44,7 @@ def HashMap.new_with_capacity
   let slots ← HashMap.allocate_slots T (alloc.vec.Vec.new (List T)) capacity
   let i ← capacity * max_load_dividend
   let i1 ← i / max_load_divisor
-  Result.ret
+  Result.ok
     {
       num_entries := 0#usize,
       max_load_factor := (max_load_dividend, max_load_divisor),
@@ -73,19 +73,19 @@ divergent def HashMap.clear_loop
     let i2 ← i + 1#usize
     let slots1 ← index_mut_back List.Nil
     HashMap.clear_loop T slots1 i2
-  else Result.ret slots
+  else Result.ok slots
 
 /- [hashmap::{hashmap::HashMap<T>}::clear]:
    Source: 'src/hashmap.rs', lines 80:4-80:27 -/
 def HashMap.clear (T : Type) (self : HashMap T) : Result (HashMap T) :=
   do
   let hm ← HashMap.clear_loop T self.slots 0#usize
-  Result.ret { self with num_entries := 0#usize, slots := hm }
+  Result.ok { self with num_entries := 0#usize, slots := hm }
 
 /- [hashmap::{hashmap::HashMap<T>}::len]:
    Source: 'src/hashmap.rs', lines 90:4-90:30 -/
 def HashMap.len (T : Type) (self : HashMap T) : Result Usize :=
-  Result.ret self.num_entries
+  Result.ok self.num_entries
 
 /- [hashmap::{hashmap::HashMap<T>}::insert_in_list]: loop 0:
    Source: 'src/hashmap.rs', lines 97:4-114:5 -/
@@ -96,12 +96,12 @@ divergent def HashMap.insert_in_list_loop
   match ls with
   | List.Cons ckey cvalue tl =>
     if ckey = key
-    then Result.ret (false, List.Cons ckey value tl)
+    then Result.ok (false, List.Cons ckey value tl)
     else
       do
       let (b, tl1) ← HashMap.insert_in_list_loop T key value tl
-      Result.ret (b, List.Cons ckey cvalue tl1)
-  | List.Nil => Result.ret (true, List.Cons key value List.Nil)
+      Result.ok (b, List.Cons ckey cvalue tl1)
+  | List.Nil => Result.ok (true, List.Cons key value List.Nil)
 
 /- [hashmap::{hashmap::HashMap<T>}::insert_in_list]:
    Source: 'src/hashmap.rs', lines 97:4-97:71 -/
@@ -130,10 +130,10 @@ def HashMap.insert_no_resize
     do
     let i1 ← self.num_entries + 1#usize
     let v ← index_mut_back l1
-    Result.ret { self with num_entries := i1, slots := v }
+    Result.ok { self with num_entries := i1, slots := v }
   else do
        let v ← index_mut_back l1
-       Result.ret { self with slots := v }
+       Result.ok { self with slots := v }
 
 /- [hashmap::{hashmap::HashMap<T>}::move_elements_from_list]: loop 0:
    Source: 'src/hashmap.rs', lines 183:4-196:5 -/
@@ -144,7 +144,7 @@ divergent def HashMap.move_elements_from_list_loop
     do
     let ntable1 ← HashMap.insert_no_resize T ntable k v
     HashMap.move_elements_from_list_loop T ntable1 tl
-  | List.Nil => Result.ret ntable
+  | List.Nil => Result.ok ntable
 
 /- [hashmap::{hashmap::HashMap<T>}::move_elements_from_list]:
    Source: 'src/hashmap.rs', lines 183:4-183:72 -/
@@ -171,7 +171,7 @@ divergent def HashMap.move_elements_loop
     let i2 ← i + 1#usize
     let slots1 ← index_mut_back l1
     HashMap.move_elements_loop T ntable1 slots1 i2
-  else Result.ret (ntable, slots)
+  else Result.ok (ntable, slots)
 
 /- [hashmap::{hashmap::HashMap<T>}::move_elements]:
    Source: 'src/hashmap.rs', lines 171:4-171:95 -/
@@ -198,13 +198,13 @@ def HashMap.try_resize (T : Type) (self : HashMap T) : Result (HashMap T) :=
     let ntable ← HashMap.new_with_capacity T i3 i i1
     let p ← HashMap.move_elements T ntable self.slots 0#usize
     let (ntable1, _) := p
-    Result.ret
+    Result.ok
       {
         ntable1
           with
           num_entries := self.num_entries, max_load_factor := (i, i1)
       }
-  else Result.ret { self with max_load_factor := (i, i1) }
+  else Result.ok { self with max_load_factor := (i, i1) }
 
 /- [hashmap::{hashmap::HashMap<T>}::insert]:
    Source: 'src/hashmap.rs', lines 129:4-129:48 -/
@@ -217,7 +217,7 @@ def HashMap.insert
   let i ← HashMap.len T self1
   if i > self1.max_load
   then HashMap.try_resize T self1
-  else Result.ret self1
+  else Result.ok self1
 
 /- [hashmap::{hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
    Source: 'src/hashmap.rs', lines 206:4-219:5 -/
@@ -226,9 +226,9 @@ divergent def HashMap.contains_key_in_list_loop
   match ls with
   | List.Cons ckey _ tl =>
     if ckey = key
-    then Result.ret true
+    then Result.ok true
     else HashMap.contains_key_in_list_loop T key tl
-  | List.Nil => Result.ret false
+  | List.Nil => Result.ok false
 
 /- [hashmap::{hashmap::HashMap<T>}::contains_key_in_list]:
    Source: 'src/hashmap.rs', lines 206:4-206:68 -/
@@ -256,7 +256,7 @@ divergent def HashMap.get_in_list_loop
   match ls with
   | List.Cons ckey cvalue tl =>
     if ckey = key
-    then Result.ret cvalue
+    then Result.ok cvalue
     else HashMap.get_in_list_loop T key tl
   | List.Nil => Result.fail .panic
 
@@ -287,8 +287,8 @@ divergent def HashMap.get_mut_in_list_loop
   | List.Cons ckey cvalue tl =>
     if ckey = key
     then
-      let back := fun ret => Result.ret (List.Cons ckey ret tl)
-      Result.ret (cvalue, back)
+      let back := fun ret => Result.ok (List.Cons ckey ret tl)
+      Result.ok (cvalue, back)
     else
       do
       let (t, back) ← HashMap.get_mut_in_list_loop T tl key
@@ -296,8 +296,8 @@ divergent def HashMap.get_mut_in_list_loop
         fun ret =>
           do
           let tl1 ← back ret
-          Result.ret (List.Cons ckey cvalue tl1)
-      Result.ret (t, back1)
+          Result.ok (List.Cons ckey cvalue tl1)
+      Result.ok (t, back1)
   | List.Nil => Result.fail .panic
 
 /- [hashmap::{hashmap::HashMap<T>}::get_mut_in_list]:
@@ -327,8 +327,8 @@ def HashMap.get_mut
       do
       let l1 ← get_mut_in_list_back ret
       let v ← index_mut_back l1
-      Result.ret { self with slots := v }
-  Result.ret (t, back)
+      Result.ok { self with slots := v }
+  Result.ok (t, back)
 
 /- [hashmap::{hashmap::HashMap<T>}::remove_from_list]: loop 0:
    Source: 'src/hashmap.rs', lines 265:4-291:5 -/
@@ -341,13 +341,13 @@ divergent def HashMap.remove_from_list_loop
       let (mv_ls, _) :=
         core.mem.replace (List T) (List.Cons ckey t tl) List.Nil
       match mv_ls with
-      | List.Cons _ cvalue tl1 => Result.ret (some cvalue, tl1)
+      | List.Cons _ cvalue tl1 => Result.ok (some cvalue, tl1)
       | List.Nil => Result.fail .panic
     else
       do
       let (o, tl1) ← HashMap.remove_from_list_loop T key tl
-      Result.ret (o, List.Cons ckey t tl1)
-  | List.Nil => Result.ret (none, List.Nil)
+      Result.ok (o, List.Cons ckey t tl1)
+  | List.Nil => Result.ok (none, List.Nil)
 
 /- [hashmap::{hashmap::HashMap<T>}::remove_from_list]:
    Source: 'src/hashmap.rs', lines 265:4-265:69 -/
@@ -373,12 +373,12 @@ def HashMap.remove
   | none =>
     do
     let v ← index_mut_back l1
-    Result.ret (none, { self with slots := v })
+    Result.ok (none, { self with slots := v })
   | some x1 =>
     do
     let i1 ← self.num_entries - 1#usize
     let v ← index_mut_back l1
-    Result.ret (some x1, { self with num_entries := i1, slots := v })
+    Result.ok (some x1, { self with num_entries := i1, slots := v })
 
 /- [hashmap::test1]:
    Source: 'src/hashmap.rs', lines 315:0-315:10 -/
@@ -422,6 +422,6 @@ def test1 : Result Unit :=
               let i4 ← HashMap.get U64 hm6 1056#usize
               if ¬ (i4 = 256#u64)
               then Result.fail .panic
-              else Result.ret ()
+              else Result.ok ()
 
 end hashmap
diff --git a/tests/lean/Hashmap/Properties.lean b/tests/lean/Hashmap/Properties.lean
index 4e0ca509..fcaf5806 100644
--- a/tests/lean/Hashmap/Properties.lean
+++ b/tests/lean/Hashmap/Properties.lean
@@ -59,7 +59,7 @@ def distinct_keys (ls : Core.List (Usize × α)) := ls.pairwise_rel (λ x y => x
 
 def hash_mod_key (k : Usize) (l : Int) : Int :=
   match hash_key k with
-  | .ret k => k.val % l
+  | .ok k => k.val % l
   | _ => 0
 
 @[simp]
@@ -121,7 +121,7 @@ theorem insert_in_list_spec_aux {α : Type} (l : Int) (key: Usize) (value: α) (
   (hinv : slot_s_inv_hash l (hash_mod_key key l) l0.v)
   (hdk : distinct_keys l0.v) :
   ∃ b l1,
-    insert_in_list α key value l0 = ret (b, l1) ∧
+    insert_in_list α key value l0 = ok (b, l1) ∧
     -- The boolean is true ↔ we inserted a new binding
     (b ↔ (l0.lookup key = none)) ∧
     -- We update the binding
@@ -183,7 +183,7 @@ theorem insert_in_list_spec {α : Type} (l : Int) (key: Usize) (value: α) (l0:
   (hinv : slot_s_inv_hash l (hash_mod_key key l) l0.v)
   (hdk : distinct_keys l0.v) :
   ∃ b l1,
-    insert_in_list α key value l0 = ret (b, l1) ∧
+    insert_in_list α key value l0 = ok (b, l1) ∧
     (b ↔ (l0.lookup key = none)) ∧
     -- We update the binding
     l1.lookup key = value ∧
@@ -240,7 +240,7 @@ set_option maxHeartbeats 2000000
 
 theorem insert_no_resize_spec {α : Type} (hm : HashMap α) (key : Usize) (value : α)
   (hinv : hm.inv) (hnsat : hm.lookup key = none → hm.len_s < Usize.max) :
-  ∃ nhm, hm.insert_no_resize α key value = ret nhm  ∧
+  ∃ nhm, hm.insert_no_resize α key value = ok nhm  ∧
   -- We preserve the invariant
   nhm.inv ∧
   -- We updated the binding for key
@@ -253,7 +253,7 @@ theorem insert_no_resize_spec {α : Type} (hm : HashMap α) (key : Usize) (value
    | some _ => nhm.len_s = hm.len_s) := by
   rw [insert_no_resize]
   -- Simplify. Note that this also simplifies some function calls, like array index
-  simp [hash_key, bind_tc_ret]
+  simp [hash_key, bind_tc_ok]
   have _ : (alloc.vec.Vec.len (List α) hm.slots).val ≠ 0 := by
    intro
    simp_all [inv]
@@ -281,7 +281,7 @@ theorem insert_no_resize_spec {α : Type} (hm : HashMap α) (key : Usize) (value
   rw [if_update_eq] -- TODO: necessary because we don't have a join
   -- TODO: progress to ...
   have hipost :
-    ∃ i0, (if inserted = true then hm.num_entries + Usize.ofInt 1 else pure hm.num_entries) = ret i0 ∧
+    ∃ i0, (if inserted = true then hm.num_entries + Usize.ofInt 1 else pure hm.num_entries) = ok i0 ∧
     i0.val = if inserted then hm.num_entries.val + 1 else hm.num_entries.val
     := by
     if inserted then
@@ -328,7 +328,7 @@ theorem insert_no_resize_spec {α : Type} (hm : HashMap α) (key : Usize) (value
       -- TODO: we want to automate this
       simp only [k_hash_mod]
       have h := Int.emod_lt_of_pos k.val hvpos
-      simp_all only [ret.injEq, exists_eq_left', List.len_update, gt_iff_lt,
+      simp_all only [ok.injEq, exists_eq_left', List.len_update, gt_iff_lt,
                      List.index_update_eq, ne_eq, not_false_eq_true, neq_imp]
     if h_hm : k_hash_mod = hash_mod.val then
       simp_all only [k_hash_mod, List.len_update, gt_iff_lt, List.index_update_eq,
diff --git a/tests/lean/HashmapMain/Funs.lean b/tests/lean/HashmapMain/Funs.lean
index 6fac6940..e985ec6a 100644
--- a/tests/lean/HashmapMain/Funs.lean
+++ b/tests/lean/HashmapMain/Funs.lean
@@ -10,7 +10,7 @@ namespace hashmap_main
 /- [hashmap_main::hashmap::hash_key]:
    Source: 'src/hashmap.rs', lines 27:0-27:32 -/
 def hashmap.hash_key (k : Usize) : Result Usize :=
-  Result.ret k
+  Result.ok k
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::allocate_slots]: loop 0:
    Source: 'src/hashmap.rs', lines 50:4-56:5 -/
@@ -24,7 +24,7 @@ divergent def hashmap.HashMap.allocate_slots_loop
     let slots1 ← alloc.vec.Vec.push (hashmap.List T) slots hashmap.List.Nil
     let n1 ← n - 1#usize
     hashmap.HashMap.allocate_slots_loop T slots1 n1
-  else Result.ret slots
+  else Result.ok slots
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::allocate_slots]:
    Source: 'src/hashmap.rs', lines 50:4-50:76 -/
@@ -47,7 +47,7 @@ def hashmap.HashMap.new_with_capacity
       capacity
   let i ← capacity * max_load_dividend
   let i1 ← i / max_load_divisor
-  Result.ret
+  Result.ok
     {
       num_entries := 0#usize,
       max_load_factor := (max_load_dividend, max_load_divisor),
@@ -76,7 +76,7 @@ divergent def hashmap.HashMap.clear_loop
     let i2 ← i + 1#usize
     let slots1 ← index_mut_back hashmap.List.Nil
     hashmap.HashMap.clear_loop T slots1 i2
-  else Result.ret slots
+  else Result.ok slots
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::clear]:
    Source: 'src/hashmap.rs', lines 80:4-80:27 -/
@@ -84,12 +84,12 @@ def hashmap.HashMap.clear
   (T : Type) (self : hashmap.HashMap T) : Result (hashmap.HashMap T) :=
   do
   let hm ← hashmap.HashMap.clear_loop T self.slots 0#usize
-  Result.ret { self with num_entries := 0#usize, slots := hm }
+  Result.ok { self with num_entries := 0#usize, slots := hm }
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::len]:
    Source: 'src/hashmap.rs', lines 90:4-90:30 -/
 def hashmap.HashMap.len (T : Type) (self : hashmap.HashMap T) : Result Usize :=
-  Result.ret self.num_entries
+  Result.ok self.num_entries
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert_in_list]: loop 0:
    Source: 'src/hashmap.rs', lines 97:4-114:5 -/
@@ -100,13 +100,13 @@ divergent def hashmap.HashMap.insert_in_list_loop
   match ls with
   | hashmap.List.Cons ckey cvalue tl =>
     if ckey = key
-    then Result.ret (false, hashmap.List.Cons ckey value tl)
+    then Result.ok (false, hashmap.List.Cons ckey value tl)
     else
       do
       let (b, tl1) ← hashmap.HashMap.insert_in_list_loop T key value tl
-      Result.ret (b, hashmap.List.Cons ckey cvalue tl1)
+      Result.ok (b, hashmap.List.Cons ckey cvalue tl1)
   | hashmap.List.Nil =>
-    Result.ret (true, hashmap.List.Cons key value hashmap.List.Nil)
+    Result.ok (true, hashmap.List.Cons key value hashmap.List.Nil)
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert_in_list]:
    Source: 'src/hashmap.rs', lines 97:4-97:71 -/
@@ -136,10 +136,10 @@ def hashmap.HashMap.insert_no_resize
     do
     let i1 ← self.num_entries + 1#usize
     let v ← index_mut_back l1
-    Result.ret { self with num_entries := i1, slots := v }
+    Result.ok { self with num_entries := i1, slots := v }
   else do
        let v ← index_mut_back l1
-       Result.ret { self with slots := v }
+       Result.ok { self with slots := v }
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements_from_list]: loop 0:
    Source: 'src/hashmap.rs', lines 183:4-196:5 -/
@@ -152,7 +152,7 @@ divergent def hashmap.HashMap.move_elements_from_list_loop
     do
     let ntable1 ← hashmap.HashMap.insert_no_resize T ntable k v
     hashmap.HashMap.move_elements_from_list_loop T ntable1 tl
-  | hashmap.List.Nil => Result.ret ntable
+  | hashmap.List.Nil => Result.ok ntable
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements_from_list]:
    Source: 'src/hashmap.rs', lines 183:4-183:72 -/
@@ -181,7 +181,7 @@ divergent def hashmap.HashMap.move_elements_loop
     let i2 ← i + 1#usize
     let slots1 ← index_mut_back l1
     hashmap.HashMap.move_elements_loop T ntable1 slots1 i2
-  else Result.ret (ntable, slots)
+  else Result.ok (ntable, slots)
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::move_elements]:
    Source: 'src/hashmap.rs', lines 171:4-171:95 -/
@@ -209,13 +209,13 @@ def hashmap.HashMap.try_resize
     let ntable ← hashmap.HashMap.new_with_capacity T i3 i i1
     let p ← hashmap.HashMap.move_elements T ntable self.slots 0#usize
     let (ntable1, _) := p
-    Result.ret
+    Result.ok
       {
         ntable1
           with
           num_entries := self.num_entries, max_load_factor := (i, i1)
       }
-  else Result.ret { self with max_load_factor := (i, i1) }
+  else Result.ok { self with max_load_factor := (i, i1) }
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::insert]:
    Source: 'src/hashmap.rs', lines 129:4-129:48 -/
@@ -228,7 +228,7 @@ def hashmap.HashMap.insert
   let i ← hashmap.HashMap.len T self1
   if i > self1.max_load
   then hashmap.HashMap.try_resize T self1
-  else Result.ret self1
+  else Result.ok self1
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::contains_key_in_list]: loop 0:
    Source: 'src/hashmap.rs', lines 206:4-219:5 -/
@@ -237,9 +237,9 @@ divergent def hashmap.HashMap.contains_key_in_list_loop
   match ls with
   | hashmap.List.Cons ckey _ tl =>
     if ckey = key
-    then Result.ret true
+    then Result.ok true
     else hashmap.HashMap.contains_key_in_list_loop T key tl
-  | hashmap.List.Nil => Result.ret false
+  | hashmap.List.Nil => Result.ok false
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::contains_key_in_list]:
    Source: 'src/hashmap.rs', lines 206:4-206:68 -/
@@ -268,7 +268,7 @@ divergent def hashmap.HashMap.get_in_list_loop
   match ls with
   | hashmap.List.Cons ckey cvalue tl =>
     if ckey = key
-    then Result.ret cvalue
+    then Result.ok cvalue
     else hashmap.HashMap.get_in_list_loop T key tl
   | hashmap.List.Nil => Result.fail .panic
 
@@ -302,8 +302,8 @@ divergent def hashmap.HashMap.get_mut_in_list_loop
   | hashmap.List.Cons ckey cvalue tl =>
     if ckey = key
     then
-      let back := fun ret => Result.ret (hashmap.List.Cons ckey ret tl)
-      Result.ret (cvalue, back)
+      let back := fun ret => Result.ok (hashmap.List.Cons ckey ret tl)
+      Result.ok (cvalue, back)
     else
       do
       let (t, back) ← hashmap.HashMap.get_mut_in_list_loop T tl key
@@ -311,8 +311,8 @@ divergent def hashmap.HashMap.get_mut_in_list_loop
         fun ret =>
           do
           let tl1 ← back ret
-          Result.ret (hashmap.List.Cons ckey cvalue tl1)
-      Result.ret (t, back1)
+          Result.ok (hashmap.List.Cons ckey cvalue tl1)
+      Result.ok (t, back1)
   | hashmap.List.Nil => Result.fail .panic
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::get_mut_in_list]:
@@ -343,8 +343,8 @@ def hashmap.HashMap.get_mut
       do
       let l1 ← get_mut_in_list_back ret
       let v ← index_mut_back l1
-      Result.ret { self with slots := v }
-  Result.ret (t, back)
+      Result.ok { self with slots := v }
+  Result.ok (t, back)
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::remove_from_list]: loop 0:
    Source: 'src/hashmap.rs', lines 265:4-291:5 -/
@@ -360,13 +360,13 @@ divergent def hashmap.HashMap.remove_from_list_loop
         core.mem.replace (hashmap.List T) (hashmap.List.Cons ckey t tl)
           hashmap.List.Nil
       match mv_ls with
-      | hashmap.List.Cons _ cvalue tl1 => Result.ret (some cvalue, tl1)
+      | hashmap.List.Cons _ cvalue tl1 => Result.ok (some cvalue, tl1)
       | hashmap.List.Nil => Result.fail .panic
     else
       do
       let (o, tl1) ← hashmap.HashMap.remove_from_list_loop T key tl
-      Result.ret (o, hashmap.List.Cons ckey t tl1)
-  | hashmap.List.Nil => Result.ret (none, hashmap.List.Nil)
+      Result.ok (o, hashmap.List.Cons ckey t tl1)
+  | hashmap.List.Nil => Result.ok (none, hashmap.List.Nil)
 
 /- [hashmap_main::hashmap::{hashmap_main::hashmap::HashMap<T>}::remove_from_list]:
    Source: 'src/hashmap.rs', lines 265:4-265:69 -/
@@ -395,12 +395,12 @@ def hashmap.HashMap.remove
   | none =>
     do
     let v ← index_mut_back l1
-    Result.ret (none, { self with slots := v })
+    Result.ok (none, { self with slots := v })
   | some x1 =>
     do
     let i1 ← self.num_entries - 1#usize
     let v ← index_mut_back l1
-    Result.ret (some x1, { self with num_entries := i1, slots := v })
+    Result.ok (some x1, { self with num_entries := i1, slots := v })
 
 /- [hashmap_main::hashmap::test1]:
    Source: 'src/hashmap.rs', lines 315:0-315:10 -/
@@ -444,7 +444,7 @@ def hashmap.test1 : Result Unit :=
               let i4 ← hashmap.HashMap.get U64 hm6 1056#usize
               if ¬ (i4 = 256#u64)
               then Result.fail .panic
-              else Result.ret ()
+              else Result.ok ()
 
 /- [hashmap_main::insert_on_disk]:
    Source: 'src/hashmap_main.rs', lines 7:0-7:43 -/
@@ -458,6 +458,6 @@ def insert_on_disk
 /- [hashmap_main::main]:
    Source: 'src/hashmap_main.rs', lines 16:0-16:13 -/
 def main : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 end hashmap_main
diff --git a/tests/lean/Loops.lean b/tests/lean/Loops.lean
index 27434db8..eeba1add 100644
--- a/tests/lean/Loops.lean
+++ b/tests/lean/Loops.lean
@@ -65,7 +65,7 @@ divergent def sum_array_loop
     let s1 ← s + i1
     let i2 ← i + 1#usize
     sum_array_loop N a i2 s1
-  else Result.ret s
+  else Result.ok s
 
 /- [loops::sum_array]:
    Source: 'src/loops.rs', lines 50:0-50:52 -/
@@ -86,7 +86,7 @@ divergent def clear_loop
     let i2 ← i + 1#usize
     let v1 ← index_mut_back 0#u32
     clear_loop v1 i2
-  else Result.ret v
+  else Result.ok v
 
 /- [loops::clear]:
    Source: 'src/loops.rs', lines 62:0-62:30 -/
@@ -104,9 +104,9 @@ inductive List (T : Type) :=
 divergent def list_mem_loop (x : U32) (ls : List U32) : Result Bool :=
   match ls with
   | List.Cons y tl => if y = x
-                      then Result.ret true
+                      then Result.ok true
                       else list_mem_loop x tl
-  | List.Nil => Result.ret false
+  | List.Nil => Result.ok false
 
 /- [loops::list_mem]:
    Source: 'src/loops.rs', lines 76:0-76:52 -/
@@ -121,8 +121,8 @@ divergent def list_nth_mut_loop_loop
   | List.Cons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (List.Cons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (List.Cons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -130,8 +130,8 @@ divergent def list_nth_mut_loop_loop
       let back1 :=
         fun ret => do
                    let tl1 ← back ret
-                   Result.ret (List.Cons x tl1)
-      Result.ret (t, back1)
+                   Result.ok (List.Cons x tl1)
+      Result.ok (t, back1)
   | List.Nil => Result.fail .panic
 
 /- [loops::list_nth_mut_loop]:
@@ -147,7 +147,7 @@ divergent def list_nth_shared_loop_loop
   match ls with
   | List.Cons x tl =>
     if i = 0#u32
-    then Result.ret x
+    then Result.ok x
     else do
          let i1 ← i - 1#u32
          list_nth_shared_loop_loop T tl i1
@@ -168,16 +168,16 @@ divergent def get_elem_mut_loop
   | List.Cons y tl =>
     if y = x
     then
-      let back := fun ret => Result.ret (List.Cons ret tl)
-      Result.ret (y, back)
+      let back := fun ret => Result.ok (List.Cons ret tl)
+      Result.ok (y, back)
     else
       do
       let (i, back) ← get_elem_mut_loop x tl
       let back1 :=
         fun ret => do
                    let tl1 ← back ret
-                   Result.ret (List.Cons y tl1)
-      Result.ret (i, back1)
+                   Result.ok (List.Cons y tl1)
+      Result.ok (i, back1)
   | List.Nil => Result.fail .panic
 
 /- [loops::get_elem_mut]:
@@ -194,7 +194,7 @@ def get_elem_mut
   let back1 := fun ret => do
                           let l ← back ret
                           index_mut_back l
-  Result.ret (i, back1)
+  Result.ok (i, back1)
 
 /- [loops::get_elem_shared]: loop 0:
    Source: 'src/loops.rs', lines 129:0-143:1 -/
@@ -202,7 +202,7 @@ divergent def get_elem_shared_loop
   (x : Usize) (ls : List Usize) : Result Usize :=
   match ls with
   | List.Cons y tl => if y = x
-                      then Result.ret y
+                      then Result.ok y
                       else get_elem_shared_loop x tl
   | List.Nil => Result.fail .panic
 
@@ -222,12 +222,12 @@ def id_mut
   (T : Type) (ls : List T) :
   Result ((List T) × (List T → Result (List T)))
   :=
-  Result.ret (ls, Result.ret)
+  Result.ok (ls, Result.ok)
 
 /- [loops::id_shared]:
    Source: 'src/loops.rs', lines 149:0-149:45 -/
 def id_shared (T : Type) (ls : List T) : Result (List T) :=
-  Result.ret ls
+  Result.ok ls
 
 /- [loops::list_nth_mut_loop_with_id]: loop 0:
    Source: 'src/loops.rs', lines 154:0-165:1 -/
@@ -237,8 +237,8 @@ divergent def list_nth_mut_loop_with_id_loop
   | List.Cons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (List.Cons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (List.Cons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -246,8 +246,8 @@ divergent def list_nth_mut_loop_with_id_loop
       let back1 :=
         fun ret => do
                    let tl1 ← back ret
-                   Result.ret (List.Cons x tl1)
-      Result.ret (t, back1)
+                   Result.ok (List.Cons x tl1)
+      Result.ok (t, back1)
   | List.Nil => Result.fail .panic
 
 /- [loops::list_nth_mut_loop_with_id]:
@@ -260,7 +260,7 @@ def list_nth_mut_loop_with_id
   let back1 := fun ret => do
                           let l ← back ret
                           id_mut_back l
-  Result.ret (t, back1)
+  Result.ok (t, back1)
 
 /- [loops::list_nth_shared_loop_with_id]: loop 0:
    Source: 'src/loops.rs', lines 168:0-179:1 -/
@@ -269,7 +269,7 @@ divergent def list_nth_shared_loop_with_id_loop
   match ls with
   | List.Cons x tl =>
     if i = 0#u32
-    then Result.ret x
+    then Result.ok x
     else do
          let i1 ← i - 1#u32
          list_nth_shared_loop_with_id_loop T i1 tl
@@ -295,9 +295,9 @@ divergent def list_nth_mut_loop_pair_loop
     | List.Cons x1 tl1 =>
       if i = 0#u32
       then
-        let back'a := fun ret => Result.ret (List.Cons ret tl0)
-        let back'b := fun ret => Result.ret (List.Cons ret tl1)
-        Result.ret ((x0, x1), back'a, back'b)
+        let back'a := fun ret => Result.ok (List.Cons ret tl0)
+        let back'b := fun ret => Result.ok (List.Cons ret tl1)
+        Result.ok ((x0, x1), back'a, back'b)
       else
         do
         let i1 ← i - 1#u32
@@ -305,12 +305,12 @@ divergent def list_nth_mut_loop_pair_loop
         let back'a1 :=
           fun ret => do
                      let tl01 ← back'a ret
-                     Result.ret (List.Cons x0 tl01)
+                     Result.ok (List.Cons x0 tl01)
         let back'b1 :=
           fun ret => do
                      let tl11 ← back'b ret
-                     Result.ret (List.Cons x1 tl11)
-        Result.ret (p, back'a1, back'b1)
+                     Result.ok (List.Cons x1 tl11)
+        Result.ok (p, back'a1, back'b1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -331,7 +331,7 @@ divergent def list_nth_shared_loop_pair_loop
     match ls1 with
     | List.Cons x1 tl1 =>
       if i = 0#u32
-      then Result.ret (x0, x1)
+      then Result.ok (x0, x1)
       else do
            let i1 ← i - 1#u32
            list_nth_shared_loop_pair_loop T tl0 tl1 i1
@@ -359,8 +359,8 @@ divergent def list_nth_mut_loop_pair_merge_loop
         let back :=
           fun ret =>
             let (t, t1) := ret
-            Result.ret (List.Cons t tl0, List.Cons t1 tl1)
-        Result.ret ((x0, x1), back)
+            Result.ok (List.Cons t tl0, List.Cons t1 tl1)
+        Result.ok ((x0, x1), back)
       else
         do
         let i1 ← i - 1#u32
@@ -369,8 +369,8 @@ divergent def list_nth_mut_loop_pair_merge_loop
           fun ret =>
             do
             let (tl01, tl11) ← back ret
-            Result.ret (List.Cons x0 tl01, List.Cons x1 tl11)
-        Result.ret (p, back1)
+            Result.ok (List.Cons x0 tl01, List.Cons x1 tl11)
+        Result.ok (p, back1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -391,7 +391,7 @@ divergent def list_nth_shared_loop_pair_merge_loop
     match ls1 with
     | List.Cons x1 tl1 =>
       if i = 0#u32
-      then Result.ret (x0, x1)
+      then Result.ok (x0, x1)
       else
         do
         let i1 ← i - 1#u32
@@ -417,8 +417,8 @@ divergent def list_nth_mut_shared_loop_pair_loop
     | List.Cons x1 tl1 =>
       if i = 0#u32
       then
-        let back := fun ret => Result.ret (List.Cons ret tl0)
-        Result.ret ((x0, x1), back)
+        let back := fun ret => Result.ok (List.Cons ret tl0)
+        Result.ok ((x0, x1), back)
       else
         do
         let i1 ← i - 1#u32
@@ -426,8 +426,8 @@ divergent def list_nth_mut_shared_loop_pair_loop
         let back1 :=
           fun ret => do
                      let tl01 ← back ret
-                     Result.ret (List.Cons x0 tl01)
-        Result.ret (p, back1)
+                     Result.ok (List.Cons x0 tl01)
+        Result.ok (p, back1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -451,8 +451,8 @@ divergent def list_nth_mut_shared_loop_pair_merge_loop
     | List.Cons x1 tl1 =>
       if i = 0#u32
       then
-        let back := fun ret => Result.ret (List.Cons ret tl0)
-        Result.ret ((x0, x1), back)
+        let back := fun ret => Result.ok (List.Cons ret tl0)
+        Result.ok ((x0, x1), back)
       else
         do
         let i1 ← i - 1#u32
@@ -460,8 +460,8 @@ divergent def list_nth_mut_shared_loop_pair_merge_loop
         let back1 :=
           fun ret => do
                      let tl01 ← back ret
-                     Result.ret (List.Cons x0 tl01)
-        Result.ret (p, back1)
+                     Result.ok (List.Cons x0 tl01)
+        Result.ok (p, back1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -485,8 +485,8 @@ divergent def list_nth_shared_mut_loop_pair_loop
     | List.Cons x1 tl1 =>
       if i = 0#u32
       then
-        let back := fun ret => Result.ret (List.Cons ret tl1)
-        Result.ret ((x0, x1), back)
+        let back := fun ret => Result.ok (List.Cons ret tl1)
+        Result.ok ((x0, x1), back)
       else
         do
         let i1 ← i - 1#u32
@@ -494,8 +494,8 @@ divergent def list_nth_shared_mut_loop_pair_loop
         let back1 :=
           fun ret => do
                      let tl11 ← back ret
-                     Result.ret (List.Cons x1 tl11)
-        Result.ret (p, back1)
+                     Result.ok (List.Cons x1 tl11)
+        Result.ok (p, back1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -519,8 +519,8 @@ divergent def list_nth_shared_mut_loop_pair_merge_loop
     | List.Cons x1 tl1 =>
       if i = 0#u32
       then
-        let back := fun ret => Result.ret (List.Cons ret tl1)
-        Result.ret ((x0, x1), back)
+        let back := fun ret => Result.ok (List.Cons ret tl1)
+        Result.ok ((x0, x1), back)
       else
         do
         let i1 ← i - 1#u32
@@ -528,8 +528,8 @@ divergent def list_nth_shared_mut_loop_pair_merge_loop
         let back1 :=
           fun ret => do
                      let tl11 ← back ret
-                     Result.ret (List.Cons x1 tl11)
-        Result.ret (p, back1)
+                     Result.ok (List.Cons x1 tl11)
+        Result.ok (p, back1)
     | List.Nil => Result.fail .panic
   | List.Nil => Result.fail .panic
 
@@ -548,14 +548,14 @@ divergent def ignore_input_mut_borrow_loop (i : U32) : Result Unit :=
   then do
        let i1 ← i - 1#u32
        ignore_input_mut_borrow_loop i1
-  else Result.ret ()
+  else Result.ok ()
 
 /- [loops::ignore_input_mut_borrow]:
    Source: 'src/loops.rs', lines 345:0-345:56 -/
 def ignore_input_mut_borrow (_a : U32) (i : U32) : Result U32 :=
   do
   let _ ← ignore_input_mut_borrow_loop i
-  Result.ret _a
+  Result.ok _a
 
 /- [loops::incr_ignore_input_mut_borrow]: loop 0:
    Source: 'src/loops.rs', lines 353:0-358:1 -/
@@ -564,7 +564,7 @@ divergent def incr_ignore_input_mut_borrow_loop (i : U32) : Result Unit :=
   then do
        let i1 ← i - 1#u32
        incr_ignore_input_mut_borrow_loop i1
-  else Result.ret ()
+  else Result.ok ()
 
 /- [loops::incr_ignore_input_mut_borrow]:
    Source: 'src/loops.rs', lines 353:0-353:60 -/
@@ -572,7 +572,7 @@ def incr_ignore_input_mut_borrow (a : U32) (i : U32) : Result U32 :=
   do
   let a1 ← a + 1#u32
   let _ ← incr_ignore_input_mut_borrow_loop i
-  Result.ret a1
+  Result.ok a1
 
 /- [loops::ignore_input_shared_borrow]: loop 0:
    Source: 'src/loops.rs', lines 362:0-366:1 -/
@@ -581,13 +581,13 @@ divergent def ignore_input_shared_borrow_loop (i : U32) : Result Unit :=
   then do
        let i1 ← i - 1#u32
        ignore_input_shared_borrow_loop i1
-  else Result.ret ()
+  else Result.ok ()
 
 /- [loops::ignore_input_shared_borrow]:
    Source: 'src/loops.rs', lines 362:0-362:59 -/
 def ignore_input_shared_borrow (_a : U32) (i : U32) : Result U32 :=
   do
   let _ ← ignore_input_shared_borrow_loop i
-  Result.ret _a
+  Result.ok _a
 
 end loops
diff --git a/tests/lean/NoNestedBorrows.lean b/tests/lean/NoNestedBorrows.lean
index b90f6aef..7d28f7f9 100644
--- a/tests/lean/NoNestedBorrows.lean
+++ b/tests/lean/NoNestedBorrows.lean
@@ -159,24 +159,24 @@ def cast_bool_to_i32 (x : Bool) : Result I32 :=
 /- [no_nested_borrows::cast_bool_to_bool]:
    Source: 'src/no_nested_borrows.rs', lines 137:0-137:41 -/
 def cast_bool_to_bool (x : Bool) : Result Bool :=
-  Result.ret x
+  Result.ok x
 
 /- [no_nested_borrows::test2]:
    Source: 'src/no_nested_borrows.rs', lines 142:0-142:14 -/
 def test2 : Result Unit :=
   do
   let _ ← 23#u32 + 44#u32
-  Result.ret ()
+  Result.ok ()
 
 /- Unit test for [no_nested_borrows::test2] -/
-#assert (test2 == Result.ret ())
+#assert (test2 == Result.ok ())
 
 /- [no_nested_borrows::get_max]:
    Source: 'src/no_nested_borrows.rs', lines 154:0-154:37 -/
 def get_max (x : U32) (y : U32) : Result U32 :=
   if x >= y
-  then Result.ret x
-  else Result.ret y
+  then Result.ok x
+  else Result.ok y
 
 /- [no_nested_borrows::test3]:
    Source: 'src/no_nested_borrows.rs', lines 162:0-162:14 -/
@@ -187,10 +187,10 @@ def test3 : Result Unit :=
   let z ← x + y
   if ¬ (z = 15#u32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test3] -/
-#assert (test3 == Result.ret ())
+#assert (test3 == Result.ok ())
 
 /- [no_nested_borrows::test_neg1]:
    Source: 'src/no_nested_borrows.rs', lines 169:0-169:18 -/
@@ -199,20 +199,20 @@ def test_neg1 : Result Unit :=
   let y ← -. 3#i32
   if ¬ (y = (-3)#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_neg1] -/
-#assert (test_neg1 == Result.ret ())
+#assert (test_neg1 == Result.ok ())
 
 /- [no_nested_borrows::refs_test1]:
    Source: 'src/no_nested_borrows.rs', lines 176:0-176:19 -/
 def refs_test1 : Result Unit :=
   if ¬ (1#i32 = 1#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::refs_test1] -/
-#assert (refs_test1 == Result.ret ())
+#assert (refs_test1 == Result.ok ())
 
 /- [no_nested_borrows::refs_test2]:
    Source: 'src/no_nested_borrows.rs', lines 187:0-187:19 -/
@@ -227,18 +227,18 @@ def refs_test2 : Result Unit :=
       then Result.fail .panic
       else if ¬ (2#i32 = 2#i32)
            then Result.fail .panic
-           else Result.ret ()
+           else Result.ok ()
 
 /- Unit test for [no_nested_borrows::refs_test2] -/
-#assert (refs_test2 == Result.ret ())
+#assert (refs_test2 == Result.ok ())
 
 /- [no_nested_borrows::test_list1]:
    Source: 'src/no_nested_borrows.rs', lines 203:0-203:19 -/
 def test_list1 : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_list1] -/
-#assert (test_list1 == Result.ret ())
+#assert (test_list1 == Result.ok ())
 
 /- [no_nested_borrows::test_box1]:
    Source: 'src/no_nested_borrows.rs', lines 208:0-208:18 -/
@@ -249,29 +249,29 @@ def test_box1 : Result Unit :=
   let x ← alloc.boxed.Box.deref I32 b
   if ¬ (x = 1#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_box1] -/
-#assert (test_box1 == Result.ret ())
+#assert (test_box1 == Result.ok ())
 
 /- [no_nested_borrows::copy_int]:
    Source: 'src/no_nested_borrows.rs', lines 218:0-218:30 -/
 def copy_int (x : I32) : Result I32 :=
-  Result.ret x
+  Result.ok x
 
 /- [no_nested_borrows::test_unreachable]:
    Source: 'src/no_nested_borrows.rs', lines 224:0-224:32 -/
 def test_unreachable (b : Bool) : Result Unit :=
   if b
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- [no_nested_borrows::test_panic]:
    Source: 'src/no_nested_borrows.rs', lines 232:0-232:26 -/
 def test_panic (b : Bool) : Result Unit :=
   if b
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- [no_nested_borrows::test_copy_int]:
    Source: 'src/no_nested_borrows.rs', lines 239:0-239:22 -/
@@ -280,17 +280,17 @@ def test_copy_int : Result Unit :=
   let y ← copy_int 0#i32
   if ¬ (0#i32 = y)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_copy_int] -/
-#assert (test_copy_int == Result.ret ())
+#assert (test_copy_int == Result.ok ())
 
 /- [no_nested_borrows::is_cons]:
    Source: 'src/no_nested_borrows.rs', lines 246:0-246:38 -/
 def is_cons (T : Type) (l : List T) : Result Bool :=
   match l with
-  | List.Cons _ _ => Result.ret true
-  | List.Nil => Result.ret false
+  | List.Cons _ _ => Result.ok true
+  | List.Nil => Result.ok false
 
 /- [no_nested_borrows::test_is_cons]:
    Source: 'src/no_nested_borrows.rs', lines 253:0-253:21 -/
@@ -299,16 +299,16 @@ def test_is_cons : Result Unit :=
   let b ← is_cons I32 (List.Cons 0#i32 List.Nil)
   if ¬ b
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_is_cons] -/
-#assert (test_is_cons == Result.ret ())
+#assert (test_is_cons == Result.ok ())
 
 /- [no_nested_borrows::split_list]:
    Source: 'src/no_nested_borrows.rs', lines 259:0-259:48 -/
 def split_list (T : Type) (l : List T) : Result (T × (List T)) :=
   match l with
-  | List.Cons hd tl => Result.ret (hd, tl)
+  | List.Cons hd tl => Result.ok (hd, tl)
   | List.Nil => Result.fail .panic
 
 /- [no_nested_borrows::test_split_list]:
@@ -319,10 +319,10 @@ def test_split_list : Result Unit :=
   let (hd, _) := p
   if ¬ (hd = 0#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_split_list] -/
-#assert (test_split_list == Result.ret ())
+#assert (test_split_list == Result.ok ())
 
 /- [no_nested_borrows::choose]:
    Source: 'src/no_nested_borrows.rs', lines 274:0-274:70 -/
@@ -331,10 +331,10 @@ def choose
   Result (T × (T → Result (T × T)))
   :=
   if b
-  then let back := fun ret => Result.ret (ret, y)
-       Result.ret (x, back)
-  else let back := fun ret => Result.ret (x, ret)
-       Result.ret (y, back)
+  then let back := fun ret => Result.ok (ret, y)
+       Result.ok (x, back)
+  else let back := fun ret => Result.ok (x, ret)
+       Result.ok (y, back)
 
 /- [no_nested_borrows::choose_test]:
    Source: 'src/no_nested_borrows.rs', lines 282:0-282:20 -/
@@ -351,15 +351,15 @@ def choose_test : Result Unit :=
     then Result.fail .panic
     else if ¬ (y = 0#i32)
          then Result.fail .panic
-         else Result.ret ()
+         else Result.ok ()
 
 /- Unit test for [no_nested_borrows::choose_test] -/
-#assert (choose_test == Result.ret ())
+#assert (choose_test == Result.ok ())
 
 /- [no_nested_borrows::test_char]:
    Source: 'src/no_nested_borrows.rs', lines 294:0-294:26 -/
 def test_char : Result Char :=
-  Result.ret 'a'
+  Result.ok 'a'
 
 mutual
 
@@ -384,7 +384,7 @@ divergent def list_length (T : Type) (l : List T) : Result U32 :=
   | List.Cons _ l1 => do
                       let i ← list_length T l1
                       1#u32 + i
-  | List.Nil => Result.ret 0#u32
+  | List.Nil => Result.ok 0#u32
 
 /- [no_nested_borrows::list_nth_shared]:
    Source: 'src/no_nested_borrows.rs', lines 347:0-347:62 -/
@@ -392,7 +392,7 @@ divergent def list_nth_shared (T : Type) (l : List T) (i : U32) : Result T :=
   match l with
   | List.Cons x tl =>
     if i = 0#u32
-    then Result.ret x
+    then Result.ok x
     else do
          let i1 ← i - 1#u32
          list_nth_shared T tl i1
@@ -406,8 +406,8 @@ divergent def list_nth_mut
   | List.Cons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (List.Cons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (List.Cons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -416,8 +416,8 @@ divergent def list_nth_mut
         fun ret =>
           do
           let tl1 ← list_nth_mut_back ret
-          Result.ret (List.Cons x tl1)
-      Result.ret (t, back)
+          Result.ok (List.Cons x tl1)
+      Result.ok (t, back)
   | List.Nil => Result.fail .panic
 
 /- [no_nested_borrows::list_rev_aux]:
@@ -426,7 +426,7 @@ divergent def list_rev_aux
   (T : Type) (li : List T) (lo : List T) : Result (List T) :=
   match li with
   | List.Cons hd tl => list_rev_aux T tl (List.Cons hd lo)
-  | List.Nil => Result.ret lo
+  | List.Nil => Result.ok lo
 
 /- [no_nested_borrows::list_rev]:
    Source: 'src/no_nested_borrows.rs', lines 393:0-393:42 -/
@@ -476,10 +476,10 @@ def test_list_functions : Result Unit :=
               let i6 ← list_nth_shared I32 ls 2#u32
               if ¬ (i6 = 2#i32)
               then Result.fail .panic
-              else Result.ret ()
+              else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_list_functions] -/
-#assert (test_list_functions == Result.ret ())
+#assert (test_list_functions == Result.ok ())
 
 /- [no_nested_borrows::id_mut_pair1]:
    Source: 'src/no_nested_borrows.rs', lines 414:0-414:89 -/
@@ -487,7 +487,7 @@ def id_mut_pair1
   (T1 T2 : Type) (x : T1) (y : T2) :
   Result ((T1 × T2) × ((T1 × T2) → Result (T1 × T2)))
   :=
-  Result.ret ((x, y), Result.ret)
+  Result.ok ((x, y), Result.ok)
 
 /- [no_nested_borrows::id_mut_pair2]:
    Source: 'src/no_nested_borrows.rs', lines 418:0-418:88 -/
@@ -496,7 +496,7 @@ def id_mut_pair2
   Result ((T1 × T2) × ((T1 × T2) → Result (T1 × T2)))
   :=
   let (t, t1) := p
-  Result.ret ((t, t1), Result.ret)
+  Result.ok ((t, t1), Result.ok)
 
 /- [no_nested_borrows::id_mut_pair3]:
    Source: 'src/no_nested_borrows.rs', lines 422:0-422:93 -/
@@ -504,7 +504,7 @@ def id_mut_pair3
   (T1 T2 : Type) (x : T1) (y : T2) :
   Result ((T1 × T2) × (T1 → Result T1) × (T2 → Result T2))
   :=
-  Result.ret ((x, y), Result.ret, Result.ret)
+  Result.ok ((x, y), Result.ok, Result.ok)
 
 /- [no_nested_borrows::id_mut_pair4]:
    Source: 'src/no_nested_borrows.rs', lines 426:0-426:92 -/
@@ -513,7 +513,7 @@ def id_mut_pair4
   Result ((T1 × T2) × (T1 → Result T1) × (T2 → Result T2))
   :=
   let (t, t1) := p
-  Result.ret ((t, t1), Result.ret, Result.ret)
+  Result.ok ((t, t1), Result.ok, Result.ok)
 
 /- [no_nested_borrows::StructWithTuple]
    Source: 'src/no_nested_borrows.rs', lines 433:0-433:34 -/
@@ -523,17 +523,17 @@ structure StructWithTuple (T1 T2 : Type) where
 /- [no_nested_borrows::new_tuple1]:
    Source: 'src/no_nested_borrows.rs', lines 437:0-437:48 -/
 def new_tuple1 : Result (StructWithTuple U32 U32) :=
-  Result.ret { p := (1#u32, 2#u32) }
+  Result.ok { p := (1#u32, 2#u32) }
 
 /- [no_nested_borrows::new_tuple2]:
    Source: 'src/no_nested_borrows.rs', lines 441:0-441:48 -/
 def new_tuple2 : Result (StructWithTuple I16 I16) :=
-  Result.ret { p := (1#i16, 2#i16) }
+  Result.ok { p := (1#i16, 2#i16) }
 
 /- [no_nested_borrows::new_tuple3]:
    Source: 'src/no_nested_borrows.rs', lines 445:0-445:48 -/
 def new_tuple3 : Result (StructWithTuple U64 I64) :=
-  Result.ret { p := (1#u64, 2#i64) }
+  Result.ok { p := (1#u64, 2#i64) }
 
 /- [no_nested_borrows::StructWithPair]
    Source: 'src/no_nested_borrows.rs', lines 450:0-450:33 -/
@@ -543,7 +543,7 @@ structure StructWithPair (T1 T2 : Type) where
 /- [no_nested_borrows::new_pair1]:
    Source: 'src/no_nested_borrows.rs', lines 454:0-454:46 -/
 def new_pair1 : Result (StructWithPair U32 U32) :=
-  Result.ret { p := { x := 1#u32, y := 2#u32 } }
+  Result.ok { p := { x := 1#u32, y := 2#u32 } }
 
 /- [no_nested_borrows::test_constants]:
    Source: 'src/no_nested_borrows.rs', lines 462:0-462:23 -/
@@ -570,18 +570,18 @@ def test_constants : Result Unit :=
         let swp ← new_pair1
         if ¬ (swp.p.x = 1#u32)
         then Result.fail .panic
-        else Result.ret ()
+        else Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_constants] -/
-#assert (test_constants == Result.ret ())
+#assert (test_constants == Result.ok ())
 
 /- [no_nested_borrows::test_weird_borrows1]:
    Source: 'src/no_nested_borrows.rs', lines 471:0-471:28 -/
 def test_weird_borrows1 : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- Unit test for [no_nested_borrows::test_weird_borrows1] -/
-#assert (test_weird_borrows1 == Result.ret ())
+#assert (test_weird_borrows1 == Result.ok ())
 
 /- [no_nested_borrows::test_mem_replace]:
    Source: 'src/no_nested_borrows.rs', lines 481:0-481:37 -/
@@ -589,31 +589,31 @@ def test_mem_replace (px : U32) : Result U32 :=
   let (y, _) := core.mem.replace U32 px 1#u32
   if ¬ (y = 0#u32)
   then Result.fail .panic
-  else Result.ret 2#u32
+  else Result.ok 2#u32
 
 /- [no_nested_borrows::test_shared_borrow_bool1]:
    Source: 'src/no_nested_borrows.rs', lines 488:0-488:47 -/
 def test_shared_borrow_bool1 (b : Bool) : Result U32 :=
   if b
-  then Result.ret 0#u32
-  else Result.ret 1#u32
+  then Result.ok 0#u32
+  else Result.ok 1#u32
 
 /- [no_nested_borrows::test_shared_borrow_bool2]:
    Source: 'src/no_nested_borrows.rs', lines 501:0-501:40 -/
 def test_shared_borrow_bool2 : Result U32 :=
-  Result.ret 0#u32
+  Result.ok 0#u32
 
 /- [no_nested_borrows::test_shared_borrow_enum1]:
    Source: 'src/no_nested_borrows.rs', lines 516:0-516:52 -/
 def test_shared_borrow_enum1 (l : List U32) : Result U32 :=
   match l with
-  | List.Cons _ _ => Result.ret 1#u32
-  | List.Nil => Result.ret 0#u32
+  | List.Cons _ _ => Result.ok 1#u32
+  | List.Nil => Result.ok 0#u32
 
 /- [no_nested_borrows::test_shared_borrow_enum2]:
    Source: 'src/no_nested_borrows.rs', lines 528:0-528:40 -/
 def test_shared_borrow_enum2 : Result U32 :=
-  Result.ret 0#u32
+  Result.ok 0#u32
 
 /- [no_nested_borrows::incr]:
    Source: 'src/no_nested_borrows.rs', lines 539:0-539:24 -/
@@ -630,7 +630,7 @@ def call_incr (x : U32) : Result U32 :=
 def read_then_incr (x : U32) : Result (U32 × U32) :=
   do
   let x1 ← x + 1#u32
-  Result.ret (x, x1)
+  Result.ok (x, x1)
 
 /- [no_nested_borrows::Tuple]
    Source: 'src/no_nested_borrows.rs', lines 554:0-554:24 -/
@@ -639,12 +639,12 @@ def Tuple (T1 T2 : Type) := T1 × T2
 /- [no_nested_borrows::use_tuple_struct]:
    Source: 'src/no_nested_borrows.rs', lines 556:0-556:48 -/
 def use_tuple_struct (x : Tuple U32 U32) : Result (Tuple U32 U32) :=
-  Result.ret (1#u32, x.#1)
+  Result.ok (1#u32, x.#1)
 
 /- [no_nested_borrows::create_tuple_struct]:
    Source: 'src/no_nested_borrows.rs', lines 560:0-560:61 -/
 def create_tuple_struct (x : U32) (y : U64) : Result (Tuple U32 U64) :=
-  Result.ret (x, y)
+  Result.ok (x, y)
 
 /- [no_nested_borrows::IdType]
    Source: 'src/no_nested_borrows.rs', lines 565:0-565:20 -/
@@ -653,11 +653,11 @@ def create_tuple_struct (x : U32) (y : U64) : Result (Tuple U32 U64) :=
 /- [no_nested_borrows::use_id_type]:
    Source: 'src/no_nested_borrows.rs', lines 567:0-567:40 -/
 def use_id_type (T : Type) (x : IdType T) : Result T :=
-  Result.ret x
+  Result.ok x
 
 /- [no_nested_borrows::create_id_type]:
    Source: 'src/no_nested_borrows.rs', lines 571:0-571:43 -/
 def create_id_type (T : Type) (x : T) : Result (IdType T) :=
-  Result.ret x
+  Result.ok x
 
 end no_nested_borrows
diff --git a/tests/lean/Paper.lean b/tests/lean/Paper.lean
index 5b00aa83..32203eca 100644
--- a/tests/lean/Paper.lean
+++ b/tests/lean/Paper.lean
@@ -17,10 +17,10 @@ def test_incr : Result Unit :=
   let x ← ref_incr 0#i32
   if ¬ (x = 1#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [paper::test_incr] -/
-#assert (test_incr == Result.ret ())
+#assert (test_incr == Result.ok ())
 
 /- [paper::choose]:
    Source: 'src/paper.rs', lines 15:0-15:70 -/
@@ -29,10 +29,10 @@ def choose
   Result (T × (T → Result (T × T)))
   :=
   if b
-  then let back := fun ret => Result.ret (ret, y)
-       Result.ret (x, back)
-  else let back := fun ret => Result.ret (x, ret)
-       Result.ret (y, back)
+  then let back := fun ret => Result.ok (ret, y)
+       Result.ok (x, back)
+  else let back := fun ret => Result.ok (x, ret)
+       Result.ok (y, back)
 
 /- [paper::test_choose]:
    Source: 'src/paper.rs', lines 23:0-23:20 -/
@@ -49,10 +49,10 @@ def test_choose : Result Unit :=
     then Result.fail .panic
     else if ¬ (y = 0#i32)
          then Result.fail .panic
-         else Result.ret ()
+         else Result.ok ()
 
 /- Unit test for [paper::test_choose] -/
-#assert (test_choose == Result.ret ())
+#assert (test_choose == Result.ok ())
 
 /- [paper::List]
    Source: 'src/paper.rs', lines 35:0-35:16 -/
@@ -68,8 +68,8 @@ divergent def list_nth_mut
   | List.Cons x tl =>
     if i = 0#u32
     then
-      let back := fun ret => Result.ret (List.Cons ret tl)
-      Result.ret (x, back)
+      let back := fun ret => Result.ok (List.Cons ret tl)
+      Result.ok (x, back)
     else
       do
       let i1 ← i - 1#u32
@@ -78,8 +78,8 @@ divergent def list_nth_mut
         fun ret =>
           do
           let tl1 ← list_nth_mut_back ret
-          Result.ret (List.Cons x tl1)
-      Result.ret (t, back)
+          Result.ok (List.Cons x tl1)
+      Result.ok (t, back)
   | List.Nil => Result.fail .panic
 
 /- [paper::sum]:
@@ -89,7 +89,7 @@ divergent def sum (l : List I32) : Result I32 :=
   | List.Cons x tl => do
                       let i ← sum tl
                       x + i
-  | List.Nil => Result.ret 0#i32
+  | List.Nil => Result.ok 0#i32
 
 /- [paper::test_nth]:
    Source: 'src/paper.rs', lines 68:0-68:17 -/
@@ -103,10 +103,10 @@ def test_nth : Result Unit :=
   let i ← sum l2
   if ¬ (i = 7#i32)
   then Result.fail .panic
-  else Result.ret ()
+  else Result.ok ()
 
 /- Unit test for [paper::test_nth] -/
-#assert (test_nth == Result.ret ())
+#assert (test_nth == Result.ok ())
 
 /- [paper::call_choose]:
    Source: 'src/paper.rs', lines 76:0-76:44 -/
@@ -116,6 +116,6 @@ def call_choose (p : (U32 × U32)) : Result U32 :=
   let (pz, choose_back) ← choose U32 true px py
   let pz1 ← pz + 1#u32
   let (px1, _) ← choose_back pz1
-  Result.ret px1
+  Result.ok px1
 
 end paper
diff --git a/tests/lean/PoloniusList.lean b/tests/lean/PoloniusList.lean
index c657237f..09f41056 100644
--- a/tests/lean/PoloniusList.lean
+++ b/tests/lean/PoloniusList.lean
@@ -20,7 +20,7 @@ divergent def get_list_at_x
   match ls with
   | List.Cons hd tl =>
     if hd = x
-    then Result.ret (List.Cons hd tl, Result.ret)
+    then Result.ok (List.Cons hd tl, Result.ok)
     else
       do
       let (l, get_list_at_x_back) ← get_list_at_x tl x
@@ -28,8 +28,8 @@ divergent def get_list_at_x
         fun ret =>
           do
           let tl1 ← get_list_at_x_back ret
-          Result.ret (List.Cons hd tl1)
-      Result.ret (l, back)
-  | List.Nil => Result.ret (List.Nil, Result.ret)
+          Result.ok (List.Cons hd tl1)
+      Result.ok (l, back)
+  | List.Nil => Result.ok (List.Nil, Result.ok)
 
 end polonius_list
diff --git a/tests/lean/Traits.lean b/tests/lean/Traits.lean
index 766b109d..0076e6f6 100644
--- a/tests/lean/Traits.lean
+++ b/tests/lean/Traits.lean
@@ -13,7 +13,7 @@ structure BoolTrait (Self : Type) where
 /- [traits::{(traits::BoolTrait for bool)}::get_bool]:
    Source: 'src/traits.rs', lines 12:4-12:30 -/
 def BoolTraitBool.get_bool (self : Bool) : Result Bool :=
-  Result.ret self
+  Result.ok self
 
 /- Trait implementation: [traits::{(traits::BoolTrait for bool)}]
    Source: 'src/traits.rs', lines 11:0-11:23 -/
@@ -25,7 +25,7 @@ def BoolTraitBool : BoolTrait Bool := {
    Source: 'src/traits.rs', lines 6:4-6:30 -/
 def BoolTrait.ret_true
   {Self : Type} (self_clause : BoolTrait Self) (self : Self) : Result Bool :=
-  Result.ret true
+  Result.ok true
 
 /- [traits::test_bool_trait_bool]:
    Source: 'src/traits.rs', lines 17:0-17:44 -/
@@ -34,14 +34,14 @@ def test_bool_trait_bool (x : Bool) : Result Bool :=
   let b ← BoolTraitBool.get_bool x
   if b
   then BoolTrait.ret_true BoolTraitBool x
-  else Result.ret false
+  else Result.ok false
 
 /- [traits::{(traits::BoolTrait for core::option::Option<T>)#1}::get_bool]:
    Source: 'src/traits.rs', lines 23:4-23:30 -/
 def BoolTraitOption.get_bool (T : Type) (self : Option T) : Result Bool :=
   match self with
-  | none => Result.ret false
-  | some _ => Result.ret true
+  | none => Result.ok false
+  | some _ => Result.ok true
 
 /- Trait implementation: [traits::{(traits::BoolTrait for core::option::Option<T>)#1}]
    Source: 'src/traits.rs', lines 22:0-22:31 -/
@@ -56,7 +56,7 @@ def test_bool_trait_option (T : Type) (x : Option T) : Result Bool :=
   let b ← BoolTraitOption.get_bool T x
   if b
   then BoolTrait.ret_true (BoolTraitOption T) x
-  else Result.ret false
+  else Result.ok false
 
 /- [traits::test_bool_trait]:
    Source: 'src/traits.rs', lines 35:0-35:50 -/
@@ -72,7 +72,7 @@ structure ToU64 (Self : Type) where
 /- [traits::{(traits::ToU64 for u64)#2}::to_u64]:
    Source: 'src/traits.rs', lines 44:4-44:26 -/
 def ToU64U64.to_u64 (self : U64) : Result U64 :=
-  Result.ret self
+  Result.ok self
 
 /- Trait implementation: [traits::{(traits::ToU64 for u64)#2}]
    Source: 'src/traits.rs', lines 43:0-43:18 -/
@@ -148,7 +148,7 @@ structure ToType (Self T : Type) where
 /- [traits::{(traits::ToType<bool> for u64)#5}::to_type]:
    Source: 'src/traits.rs', lines 93:4-93:28 -/
 def ToTypeU64Bool.to_type (self : U64) : Result Bool :=
-  Result.ret (self > 0#u64)
+  Result.ok (self > 0#u64)
 
 /- Trait implementation: [traits::{(traits::ToType<bool> for u64)#5}]
    Source: 'src/traits.rs', lines 92:0-92:25 -/
@@ -202,7 +202,7 @@ structure TestType.test.TestTrait (Self : Type) where
    Source: 'src/traits.rs', lines 139:12-139:34 -/
 def TestType.test.TestTraittraitsTestTypetestTestType1.test
   (self : TestType.test.TestType1) : Result Bool :=
-  Result.ret (self > 1#u64)
+  Result.ok (self > 1#u64)
 
 /- Trait implementation: [traits::{traits::TestType<T>#6}::test::{(traits::{traits::TestType<T>#6}::test::TestTrait for traits::{traits::TestType<T>#6}::test::TestType1)}]
    Source: 'src/traits.rs', lines 138:8-138:36 -/
@@ -219,7 +219,7 @@ def TestType.test
   let x1 ← ToU64Inst.to_u64 x
   if x1 > 0#u64
   then TestType.test.TestTraittraitsTestTypetestTestType1.test 0#u64
-  else Result.ret false
+  else Result.ok false
 
 /- [traits::BoolWrapper]
    Source: 'src/traits.rs', lines 150:0-150:22 -/
@@ -243,7 +243,7 @@ def ToTypetraitsBoolWrapperT (T : Type) (ToTypeBoolTInst : ToType Bool T) :
 /- [traits::WithConstTy::LEN2]
    Source: 'src/traits.rs', lines 164:4-164:21 -/
 def WithConstTy.LEN2_default_body (Self : Type) (LEN : Usize) : Result Usize :=
-  Result.ret 32#usize
+  Result.ok 32#usize
 def WithConstTy.LEN2_default (Self : Type) (LEN : Usize) : Usize :=
   eval_global (WithConstTy.LEN2_default_body Self LEN)
 
@@ -259,13 +259,13 @@ structure WithConstTy (Self : Type) (LEN : Usize) where
 
 /- [traits::{(traits::WithConstTy<32: usize> for bool)#8}::LEN1]
    Source: 'src/traits.rs', lines 175:4-175:21 -/
-def WithConstTyBool32.LEN1_body : Result Usize := Result.ret 12#usize
+def WithConstTyBool32.LEN1_body : Result Usize := Result.ok 12#usize
 def WithConstTyBool32.LEN1 : Usize := eval_global WithConstTyBool32.LEN1_body
 
 /- [traits::{(traits::WithConstTy<32: usize> for bool)#8}::f]:
    Source: 'src/traits.rs', lines 180:4-180:39 -/
 def WithConstTyBool32.f (i : U64) (a : Array U8 32#usize) : Result U64 :=
-  Result.ret i
+  Result.ok i
 
 /- Trait implementation: [traits::{(traits::WithConstTy<32: usize> for bool)#8}]
    Source: 'src/traits.rs', lines 174:0-174:29 -/
@@ -284,7 +284,7 @@ def use_with_const_ty1
   (H : Type) (LEN : Usize) (WithConstTyInst : WithConstTy H LEN) :
   Result Usize
   :=
-  Result.ret WithConstTyInst.LEN1
+  Result.ok WithConstTyInst.LEN1
 
 /- [traits::use_with_const_ty2]:
    Source: 'src/traits.rs', lines 187:0-187:73 -/
@@ -293,7 +293,7 @@ def use_with_const_ty2
   (w : WithConstTyInst.W) :
   Result Unit
   :=
-  Result.ret ()
+  Result.ok ()
 
 /- [traits::use_with_const_ty3]:
    Source: 'src/traits.rs', lines 189:0-189:80 -/
@@ -307,7 +307,7 @@ def use_with_const_ty3
 /- [traits::test_where1]:
    Source: 'src/traits.rs', lines 193:0-193:40 -/
 def test_where1 (T : Type) (_x : T) : Result Unit :=
-  Result.ret ()
+  Result.ok ()
 
 /- [traits::test_where2]:
    Source: 'src/traits.rs', lines 194:0-194:57 -/
@@ -315,7 +315,7 @@ def test_where2
   (T : Type) (WithConstTyT32Inst : WithConstTy T 32#usize) (_x : U32) :
   Result Unit
   :=
-  Result.ret ()
+  Result.ok ()
 
 /- Trait declaration: [traits::ParentTrait0]
    Source: 'src/traits.rs', lines 200:0-200:22 -/
@@ -355,7 +355,7 @@ def order1
   ParentTrait0 U) :
   Result Unit
   :=
-  Result.ret ()
+  Result.ok ()
 
 /- Trait declaration: [traits::ChildTrait1]
    Source: 'src/traits.rs', lines 222:0-222:35 -/
@@ -429,7 +429,7 @@ def ParentTrait2U32 : ParentTrait2 U32 := {
 /- [traits::{(traits::ChildTrait2 for u32)#13}::convert]:
    Source: 'src/traits.rs', lines 273:4-273:29 -/
 def ChildTrait2U32.convert (x : U32) : Result U32 :=
-  Result.ret x
+  Result.ok x
 
 /- Trait implementation: [traits::{(traits::ChildTrait2 for u32)#13}]
    Source: 'src/traits.rs', lines 272:0-272:24 -/
@@ -475,7 +475,7 @@ structure Trait (Self : Type) where
 
 /- [traits::{(traits::Trait for @Array<T, N>)#14}::LEN]
    Source: 'src/traits.rs', lines 315:4-315:20 -/
-def TraitArray.LEN_body (T : Type) (N : Usize) : Result Usize := Result.ret N
+def TraitArray.LEN_body (T : Type) (N : Usize) : Result Usize := Result.ok N
 def TraitArray.LEN (T : Type) (N : Usize) : Usize :=
   eval_global (TraitArray.LEN_body T N)
 
@@ -489,7 +489,7 @@ def TraitArray (T : Type) (N : Usize) : Trait (Array T N) := {
    Source: 'src/traits.rs', lines 319:4-319:20 -/
 def TraittraitsWrapper.LEN_body (T : Type) (TraitInst : Trait T)
   : Result Usize :=
-  Result.ret 0#usize
+  Result.ok 0#usize
 def TraittraitsWrapper.LEN (T : Type) (TraitInst : Trait T) : Usize :=
   eval_global (TraittraitsWrapper.LEN_body T TraitInst)
 
@@ -503,7 +503,7 @@ def TraittraitsWrapper (T : Type) (TraitInst : Trait T) : Trait (Wrapper T)
 /- [traits::use_wrapper_len]:
    Source: 'src/traits.rs', lines 322:0-322:43 -/
 def use_wrapper_len (T : Type) (TraitInst : Trait T) : Result Usize :=
-  Result.ret (TraittraitsWrapper T TraitInst).LEN
+  Result.ok (TraittraitsWrapper T TraitInst).LEN
 
 /- [traits::Foo]
    Source: 'src/traits.rs', lines 326:0-326:20 -/
@@ -522,7 +522,7 @@ inductive core.result.Result (T E : Type) :=
    Source: 'src/traits.rs', lines 332:4-332:33 -/
 def Foo.FOO_body (T U : Type) (TraitInst : Trait T)
   : Result (core.result.Result T I32) :=
-  Result.ret (core.result.Result.Err 0#i32)
+  Result.ok (core.result.Result.Err 0#i32)
 def Foo.FOO (T U : Type) (TraitInst : Trait T) : core.result.Result T I32 :=
   eval_global (Foo.FOO_body T U TraitInst)
 
@@ -530,12 +530,12 @@ def Foo.FOO (T U : Type) (TraitInst : Trait T) : core.result.Result T I32 :=
    Source: 'src/traits.rs', lines 335:0-335:48 -/
 def use_foo1
   (T U : Type) (TraitInst : Trait T) : Result (core.result.Result T I32) :=
-  Result.ret (Foo.FOO T U TraitInst)
+  Result.ok (Foo.FOO T U TraitInst)
 
 /- [traits::use_foo2]:
    Source: 'src/traits.rs', lines 339:0-339:48 -/
 def use_foo2
   (T U : Type) (TraitInst : Trait U) : Result (core.result.Result U I32) :=
-  Result.ret (Foo.FOO U T TraitInst)
+  Result.ok (Foo.FOO U T TraitInst)
 
 end traits
diff --git a/tests/lean/Tutorial.lean b/tests/lean/Tutorial.lean
index d92b2dd7..94b70991 100644
--- a/tests/lean/Tutorial.lean
+++ b/tests/lean/Tutorial.lean
@@ -18,7 +18,7 @@ namespace Tutorial
 def mul2_add1 (x : U32) : Result U32 := do
   let x1 ← x + x
   let x2 ← x1 + 1#u32
-  ret x2
+  ok x2
 
 /- There are several things to note.
 
@@ -75,9 +75,9 @@ def mul2_add1 (x : U32) : Result U32 := do
  -/
 def mul2_add1_desugared (x : U32) : Result U32 :=
   match Scalar.add x x with
-  | ret x1 => -- Success case
+  | ok x1 => -- Success case
     match Scalar.add x1 (U32.ofInt 1) with
-    | ret x2 => ret x2
+    | ok x2 => ok x2
     | error => error
   | error => error -- Propagating the errors
 
@@ -105,7 +105,7 @@ theorem mul2_add1_spec
    -/
   (h : 2 * ↑x + 1 ≤ U32.max)
   /- The postcondition -/
-  : ∃ y, mul2_add1 x = ret y ∧  -- The call succeeds
+  : ∃ y, mul2_add1 x = ok y ∧  -- The call succeeds
   ↑ y = 2 * ↑x + (1 : Int)   -- The output has the expected value
   := by
   /- The proof -/
@@ -154,7 +154,7 @@ theorem mul2_add1_spec
  -/
 @[pspec] -- the [pspec] attribute saves the theorem in a database, for [progress] to use it
 theorem mul2_add1_spec2 (x : U32) (h : 2 * ↑x + 1 ≤ U32.max)
-  : ∃ y, mul2_add1 x = ret y ∧
+  : ∃ y, mul2_add1 x = ok y ∧
   ↑ y = 2 * ↑x + (1 : Int)
   := by
   rw [mul2_add1]
@@ -172,7 +172,7 @@ def use_mul2_add1 (x : U32) (y : U32) : Result U32 := do
 
 @[pspec]
 theorem use_mul2_add1_spec (x : U32) (y : U32) (h : 2 * ↑x + 1 + ↑y ≤ U32.max) :
-  ∃ z, use_mul2_add1 x y = ret z ∧
+  ∃ z, use_mul2_add1 x y = ok z ∧
   ↑z = 2 * ↑x + (1 : Int) + ↑y := by
   rw [use_mul2_add1]
   -- Here we use [progress] on [mul2_add1]
@@ -230,7 +230,7 @@ divergent def list_nth (T : Type) (l : CList T) (i : U32) : Result T :=
   match l with
   | CCons x tl =>
     if i = 0#u32
-    then ret x
+    then ok x
     else do
       let i1 ← i - 1#u32
       list_nth T tl i1
@@ -263,7 +263,7 @@ theorem list_nth_spec {T : Type} [Inhabited T] (l : CList T) (i : U32)
   -- Precondition: the index is in bounds
   (h : ↑i < l.to_list.len)
   -- Postcondition
-  : ∃ x, list_nth T l i = ret x ∧
+  : ∃ x, list_nth T l i = ok x ∧
   -- [x] is the ith element of [l] after conversion to [List]
   x = l.to_list.index ↑i
   := by
@@ -340,7 +340,7 @@ theorem list_nth_spec {T : Type} [Inhabited T] (l : CList T) (i : U32)
 
    If in a theorem we state and prove that:
    ```
-   ∃ y, i32_id x = ret x
+   ∃ y, i32_id x = ok x
    ```
    we not only prove that the function doesn't fail, but also that it terminates.
 
@@ -348,7 +348,7 @@ theorem list_nth_spec {T : Type} [Inhabited T] (l : CList T) (i : U32)
    annotates it with the [divergent] keyword.
  -/
 divergent def i32_id (x : I32) : Result I32 :=
-  if x = 0#i32 then ret 0#i32
+  if x = 0#i32 then ok 0#i32
   else do
     let x1 ← x - 1#i32
     let x2 ← i32_id x1
@@ -356,7 +356,7 @@ divergent def i32_id (x : I32) : Result I32 :=
 
 /- We can easily prove that [i32_id] behaves like the identity on positive inputs -/
 theorem i32_id_spec (x : I32) (h : 0 ≤ x.val) :
-  ∃ y, i32_id x = ret y ∧ x.val = y.val := by
+  ∃ y, i32_id x = ok y ∧ x.val = y.val := by
   rw [i32_id]
   if hx : x = 0#i32 then
     simp_all