From 559341d13a7ba5abb8521f6d0d982d4f25b86ce0 Mon Sep 17 00:00:00 2001
From: Oscar Spencer <oscar@grain-lang.org>
Date: Fri, 8 Apr 2022 13:37:50 -0400
Subject: [PATCH] fix!: Expression.Return.get_value can be null (#149)

* fix!: Expression.Return.get_value can be null

* Add test
---
 src/binaryen_stubs_expressions.c  |  7 ++++++-
 src/binaryen_stubs_expressions.js |  3 ++-
 src/expression.ml                 |  2 +-
 src/expression.mli                |  2 +-
 test/test.ml                      | 14 ++++++++++++++
 5 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/binaryen_stubs_expressions.c b/src/binaryen_stubs_expressions.c
index cfb2cc6a..791bedd1 100644
--- a/src/binaryen_stubs_expressions.c
+++ b/src/binaryen_stubs_expressions.c
@@ -1534,7 +1534,12 @@ CAMLprim value
 caml_binaryen_return_get_value(value _exp) {
   CAMLparam1(_exp);
   BinaryenExpressionRef exp = BinaryenExpressionRef_val(_exp);
-  CAMLreturn(alloc_BinaryenExpressionRef(BinaryenReturnGetValue(exp)));
+  BinaryenExpressionRef val = BinaryenReturnGetValue(exp);
+  if (val == NULL) {
+    CAMLreturn(Val_none);
+  } else {
+    CAMLreturn(caml_alloc_some(alloc_BinaryenExpressionRef(val)));
+  }
 }
 
 CAMLprim value
diff --git a/src/binaryen_stubs_expressions.js b/src/binaryen_stubs_expressions.js
index 58a471f8..08537805 100644
--- a/src/binaryen_stubs_expressions.js
+++ b/src/binaryen_stubs_expressions.js
@@ -1273,8 +1273,9 @@ function caml_binaryen_drop_set_value(exp, value) {
 
 //Provides: caml_binaryen_return_get_value
 //Requires: binaryen
+//Requires: to_option
 function caml_binaryen_return_get_value(exp) {
-  return binaryen.Return.getValue(exp);
+  return to_option(binaryen.Return.getValue(exp));
 }
 
 //Provides: caml_binaryen_return_set_value
diff --git a/src/expression.ml b/src/expression.ml
index 7220bfad..339076fd 100644
--- a/src/expression.ml
+++ b/src/expression.ml
@@ -693,7 +693,7 @@ end
 
 module Return = struct
   external make : Module.t -> t -> t = "caml_binaryen_return"
-  external get_value : t -> t = "caml_binaryen_return_get_value"
+  external get_value : t -> t option = "caml_binaryen_return_get_value"
   external set_value : t -> t -> unit = "caml_binaryen_return_set_value"
 end
 
diff --git a/src/expression.mli b/src/expression.mli
index acf8a2a7..1430228c 100644
--- a/src/expression.mli
+++ b/src/expression.mli
@@ -241,7 +241,7 @@ end
 
 module Return : sig
   val make : Module.t -> t -> t
-  val get_value : t -> t
+  val get_value : t -> t option
   val set_value : t -> t -> unit
 end
 
diff --git a/test/test.ml b/test/test.ml
index d4167e9b..3c641742 100644
--- a/test/test.ml
+++ b/test/test.ml
@@ -20,6 +20,20 @@ let _ = Settings.set_low_memory_unused false
 let wasm_mod = Module.create ()
 let _ = Module.set_features wasm_mod [ Module.Feature.all ]
 
+(* Testing Return.get_value *)
+let _ =
+  assert (
+    Option.is_some
+      (Expression.Return.get_value
+         (Expression.Return.make wasm_mod
+            (Expression.Const.make wasm_mod (Literal.int32 0l)))))
+
+let _ =
+  assert (
+    Option.is_none
+      (Expression.Return.get_value
+         (Expression.Return.make wasm_mod (Expression.Null.make ()))))
+
 (* Create function type for i32 (i32, i32) *)
 let params () = Type.create [| Type.int32; Type.int32 |]
 let results = Type.int32