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authorSon Ho2022-11-07 10:00:04 +0100
committerSon HO2022-11-07 10:36:13 +0100
commit357782ba4c039ac6d83b4fd8344121e89f87eb7b (patch)
tree7342d5976b3127d9c58155e162247442a442703d
parent47e0291dd840cfc59ee6c5bc3ac2c7edd1610ab7 (diff)
Update some comments
Diffstat (limited to '')
-rw-r--r--compiler/Invariants.ml2
-rw-r--r--compiler/Values.ml26
2 files changed, 14 insertions, 14 deletions
diff --git a/compiler/Invariants.ml b/compiler/Invariants.ml
index ff7fa1fc..ead064a4 100644
--- a/compiler/Invariants.ml
+++ b/compiler/Invariants.ml
@@ -219,7 +219,7 @@ let check_loans_borrows_relation_invariant (ctx : C.eval_ctx) : unit =
(match (info.loan_kind, kind) with
| T.Shared, (Shared | Reserved) | T.Mut, Mut -> ()
| _ -> raise (Failure "Invariant not satisfied"));
- (* An reserved borrow can't point to a value inside an abstraction *)
+ (* A reserved borrow can't point to a value inside an abstraction *)
assert (kind <> Reserved || not info.loan_in_abs);
(* Insert the borrow id *)
let borrow_ids = info.borrow_ids in
diff --git a/compiler/Values.ml b/compiler/Values.ml
index 071f5e0f..44b22f9f 100644
--- a/compiler/Values.ml
+++ b/compiler/Values.ml
@@ -113,15 +113,15 @@ and borrow_content =
| MutBorrow of (BorrowId.id[@opaque]) * typed_value
(** A mutably borrowed value. *)
| ReservedMutBorrow of mvalue * (BorrowId.id[@opaque])
- (** An reserved mut borrow.
+ (** A reserved mut borrow.
This is used to model {{: https://rustc-dev-guide.rust-lang.org/borrow_check/two_phase_borrows.html} two-phase borrows}.
When evaluating a two-phase mutable borrow, we first introduce a reserved
borrow which behaves like a shared borrow, until the moment we actually *use*
the borrow: at this point, we end all the other shared borrows (or reserved
- borrows - though there shouldn't be any other reserved borrows if the program
- is well typed) of this value and replace the reserved borrow with a
- mutable borrow.
+ borrows - though there shouldn't be any other reserved borrows) of this value
+ and replace the reserved borrow with a mutable borrow (as well as the shared
+ loan with a mutable loan).
A simple use case of two-phase borrows:
{[
@@ -134,23 +134,23 @@ and borrow_content =
v = Vec::new();
v1 = &mut v;
v2 = &v; // We need this borrow, but v has already been mutably borrowed!
- l = Vec::len(move v2);
- Vec::push(move v1, move l); // In practice, v1 gets activated only here
+ l = Vec::len(move v2); // We need v2 here, and v1 *below*
+ Vec::push(move v1, move l); // In practice, v1 gets promoted only here
]}
The meta-value is used for the same purposes as with shared borrows,
- at the exception that in case of reserved borrows it is not
+ at the exception that in the case of reserved borrows it is not
*necessary* for the synthesis: we keep it only as meta-information.
To be more precise:
- when generating the synthesized program, we may need to convert
shared borrows to pure values
- we never need to do so for reserved borrows: such borrows must
- be activated at the moment we use them (meaning we convert a *mutable*
- borrow to a pure value). However, we save meta-data about the assignments,
- which is used to make the code cleaner: when generating this meta-data,
- we may need to convert reserved borrows to pure values, in which
- situation we convert the meta-value we stored in the reserved
- borrow.
+ be promoted at the moment we use them (meaning in the synthesis we
+ convert a *mutable* borrow to a pure value). However, we save
+ meta-data about the assignments, which is used to make the code
+ cleaner: when generating this meta-data, we may need to convert
+ reserved borrows to pure values, in which situation we convert
+ the meta-value we stored in the reserved borrow.
*)
and loan_content =