restore V_attempted_read behaviour after merge

1 files changed, 11 insertions, 1 deletions

diff --git a/src/constant_fold.ml b/src/constant_fold.ml
index acae4581..a46f2765 100644
--- a/src/constant_fold.ml
+++ b/src/constant_fold.ml
@@ -78,7 +78,9 @@ and exp_of_value =
   | V_tuple vs ->
      mk_exp (E_tuple (List.map exp_of_value vs))
   | V_unit -> mk_lit_exp L_unit
-  | V_attempted_read str -> mk_exp (E_id (mk_id str))
+  | V_attempted_read str ->
+     prerr_endline ("constant_fold folding away V_attempted_read " ^ str);
+     mk_exp (E_id (mk_id str))
   | _ -> failwith "No expression for value"
 
 (* We want to avoid evaluating things like print statements at compile
@@ -126,6 +128,14 @@ let rec run frame =
      run (Interpreter.eval_frame frame)
   | Interpreter.Break frame ->
      run (Interpreter.eval_frame frame)
+  | Interpreter.Effect_request (st, Interpreter.Read_reg (reg, cont)) ->
+     (* return a dummy value to read_reg requests which we handle above
+        if an expression finally evals to it, but the interpreter
+        will fail if it tries to actually use. See value.ml *)
+     prerr_endline ("constant_fold returned V_attempted_read " ^ reg ^ "\n");
+     run (cont (Value.V_attempted_read reg) st)
+  | Interpreter.Effect_request _ ->
+     assert false (* effectful, raise exception to abort constant folding *)
 
 (** This rewriting pass looks for function applications (E_app)
    expressions where every argument is a literal. It passes these