From 95494c3efe9d49c55398dff2d755748808d7e7b4 Mon Sep 17 00:00:00 2001
From: Son Ho
Date: Wed, 24 Nov 2021 12:11:20 +0100
Subject: Make progress on eval_rvalue

---
 src/Interpreter.ml | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/Interpreter.ml b/src/Interpreter.ml
index 60afa79a..5e12cd74 100644
--- a/src/Interpreter.ml
+++ b/src/Interpreter.ml
@@ -1516,6 +1516,8 @@ let eval_rvalue (config : config) (ctx : eval_ctx) (rvalue : rvalue) :
           (* Compute the rvalue - simply a shared borrow with a fresh id *)
           let ctx2 = { ctx with env = env2 } in
           let ctx3, bid = fresh_borrow_id ctx2 in
+          let rv_ty = Types.Ref (Erased, v.ty, Shared) in
+          let rv = { value = Borrow (SharedBorrow bid); ty = rv_ty } in
           (* Compute the value with which to replace the value at place p *)
           let nv =
             match v.value with
@@ -1531,8 +1533,24 @@ let eval_rvalue (config : config) (ctx : eval_ctx) (rvalue : rvalue) :
           (* Update the value in the environment *)
           let env4 = write_place_unwrap config access p nv ctx3.env in
           (* Return *)
-          ({ ctx3 with env = env4 }, v)
-      | Expressions.Mut -> raise Unimplemented
+          ({ ctx3 with env = env4 }, rv)
+      | Expressions.Mut ->
+          (* Access the value *)
+          let access = Write in
+          let env1 = update_env_along_read_place config access p ctx.env in
+          let env2 = collect_borrows_at_place config access p env1 in
+          let v = read_place_unwrap config access p ctx.env in
+          (* Compute the rvalue - write the value in a mutable borrow *)
+          let ctx2 = { ctx with env = env2 } in
+          let ctx3, bid = fresh_borrow_id ctx2 in
+          let rv_ty = Types.Ref (Erased, v.ty, Mut) in
+          let rv = { value = Borrow (MutBorrow (bid, v)); ty = rv_ty } in
+          (* Compute the value with which to replace the value at place p *)
+          let nv = { v with value = Loan (MutLoan bid) } in
+          (* Update the value in the environment *)
+          let env4 = write_place_unwrap config access p nv ctx3.env in
+          (* Return *)
+          ({ ctx3 with env = env4 }, rv)
       | Expressions.TwoPhaseMut -> raise Unimplemented)
   | UnaryOp (unop, op) -> raise Unimplemented
   | BinaryOp (binop, op1, op2) -> raise Unimplemented
-- 
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