Change null references to be not implemented yet

Author: jayphelps

src/compiler.ts

@@ -8271,7 +8271,12 @@ export class Compiler extends DiagnosticEmitter {
             this.currentType = signatureReference.type.asNullable();
             return module.i32(0);
           }
-          return module.ref_null();
+          // TODO: return null ref for externref or funcref
+          this.error(
+            DiagnosticCode.Not_implemented_0,
+            expression.range,
+            "null references"
+          );
         }
         this.currentType = options.usizeType;
         this.warning(
@@ -10653,7 +10658,10 @@ export class Compiler extends DiagnosticEmitter {
       case TypeKind.F32: return module.f32(0);
       case TypeKind.F64: return module.f64(0);
       case TypeKind.V128: return module.v128(v128_zero);
-      case TypeKind.EXTERNREF: return module.ref_null();
+      case TypeKind.EXTERNREF:
+        // TODO: return null ref for both externref as well as funcref
+        assert(false, 'null for externref is not yet supported');
+        return module.unreachable();
     }
   }
 

tests/compiler/features/reference-types.ts

@@ -26,9 +26,8 @@ console.log(someObject);
 console.log(someKey);
 console.log(Reflect.get(someObject, someKey));
 
-// can represent and recognize 'null'
-
-var nullGlobal: externref;
+// TODO: can represent and recognize 'null' for both externref and funcref
+/* var nullGlobal: externref;
 assert(!nullGlobal);
 nullGlobal = null;
 assert(!nullGlobal);
@@ -43,10 +42,11 @@ assert(!nullGlobalInit);
   assert(!nullLocalInit);
 }
 
-// can represent function references
+// funcref can represent function references
 
 function someFunc(): void {}
 var funcGlobal: externref = someFunc;
 {
   let funcLocal: externref = someFunc;
 }
+*/