Update reference types (#3084)

Align with the current state of the reference types proposal:
* Remove `nullref`
* Remove `externref` and `funcref` subtyping
* A `Literal` of a nullable reference type can now represent `null` (previously was type `nullref`)
* Update the tests and temporarily comment out those tests relying on subtyping

4 files changed, 10 insertions, 9 deletions

diff --git a/src/ir/ExpressionManipulator.cpp b/src/ir/ExpressionManipulator.cpp
index 57048b9bd..6f64ec77b 100644
--- a/src/ir/ExpressionManipulator.cpp
+++ b/src/ir/ExpressionManipulator.cpp
@@ -227,7 +227,9 @@ flexibleCopy(Expression* original, Module& wasm, CustomCopier custom) {
         builder.makeHost(curr->op, curr->nameOperand, std::move(operands));
       return ret;
     }
-    Expression* visitRefNull(RefNull* curr) { return builder.makeRefNull(); }
+    Expression* visitRefNull(RefNull* curr) {
+      return builder.makeRefNull(curr->type);
+    }
     Expression* visitRefIsNull(RefIsNull* curr) {
       return builder.makeRefIsNull(copy(curr->value));
     }
diff --git a/src/ir/abstract.h b/src/ir/abstract.h
index f706e9972..b00537bf5 100644
--- a/src/ir/abstract.h
+++ b/src/ir/abstract.h
@@ -103,7 +103,6 @@ inline UnaryOp getUnary(Type type, Op op) {
     }
     case Type::funcref:
     case Type::externref:
-    case Type::nullref:
     case Type::exnref:
     case Type::none:
     case Type::unreachable: {
@@ -268,7 +267,6 @@ inline BinaryOp getBinary(Type type, Op op) {
     }
     case Type::funcref:
     case Type::externref:
-    case Type::nullref:
     case Type::exnref:
     case Type::none:
     case Type::unreachable: {
diff --git a/src/ir/manipulation.h b/src/ir/manipulation.h
index 49ed7e11e..fb1f0181e 100644
--- a/src/ir/manipulation.h
+++ b/src/ir/manipulation.h
@@ -40,9 +40,10 @@ template<typename InputType> inline Nop* nop(InputType* target) {
   return ret;
 }
 
-template<typename InputType> inline RefNull* refNull(InputType* target) {
+template<typename InputType>
+inline RefNull* refNull(InputType* target, Type type) {
   auto* ret = convert<InputType, RefNull>(target);
-  ret->finalize();
+  ret->finalize(type);
   return ret;
 }
 
diff --git a/src/ir/properties.h b/src/ir/properties.h
index 0c6824e4a..ac61f787e 100644
--- a/src/ir/properties.h
+++ b/src/ir/properties.h
@@ -93,10 +93,10 @@ inline bool isConstantExpression(const Expression* curr) {
 inline Literal getSingleLiteral(const Expression* curr) {
   if (auto* c = curr->dynCast<Const>()) {
     return c->value;
-  } else if (curr->is<RefNull>()) {
-    return Literal(Type::nullref);
-  } else if (auto* c = curr->dynCast<RefFunc>()) {
-    return Literal(c->func);
+  } else if (auto* n = curr->dynCast<RefNull>()) {
+    return Literal(n->type);
+  } else if (auto* r = curr->dynCast<RefFunc>()) {
+    return Literal(r->func);
   } else {
     WASM_UNREACHABLE("non-constant expression");
   }