Update reference type shorthands in binary output (#4828)

Add support for emitting the string type reference shorthands, which had
previously been omitted accidentally due to the `default` case in that switch.
Also avoid emitting shorthands for non-nullable reference types as a first step
towards transitioning the shorthands to represent nullable types instead. Not
emitting these shorthands at all will give V8 the flexibility it needs to change
its interpretation of the shorthands without breaking any workflows using
Binaryen.

1 files changed, 31 insertions, 26 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index edcf5f7bf..9f28c00bb 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -1342,32 +1342,37 @@ void WasmBinaryWriter::writeInlineBuffer(const char* data, size_t size) {
 void WasmBinaryWriter::writeType(Type type) {
   if (type.isRef()) {
     auto heapType = type.getHeapType();
-    if (heapType.isBasic()) {
-      if (type.isNullable()) {
-        switch (heapType.getBasic()) {
-          case HeapType::any:
-            o << S32LEB(BinaryConsts::EncodedType::anyref);
-            return;
-          case HeapType::func:
-            o << S32LEB(BinaryConsts::EncodedType::funcref);
-            return;
-          case HeapType::eq:
-            o << S32LEB(BinaryConsts::EncodedType::eqref);
-            return;
-          default:
-            break;
-        }
-      } else {
-        switch (heapType.getBasic()) {
-          case HeapType::i31:
-            o << S32LEB(BinaryConsts::EncodedType::i31ref);
-            return;
-          case HeapType::data:
-            o << S32LEB(BinaryConsts::EncodedType::dataref);
-            return;
-          default:
-            break;
-        }
+    if (heapType.isBasic() && type.isNullable()) {
+      switch (heapType.getBasic()) {
+        case HeapType::any:
+          o << S32LEB(BinaryConsts::EncodedType::anyref);
+          return;
+        case HeapType::func:
+          o << S32LEB(BinaryConsts::EncodedType::funcref);
+          return;
+        case HeapType::eq:
+          o << S32LEB(BinaryConsts::EncodedType::eqref);
+          return;
+        case HeapType::i31:
+          // TODO: Emit i31ref once V8 (and Binaryen itself) treats it as
+          // nullable.
+          break;
+        case HeapType::data:
+          // TODO: Emit dataref once V8 (and Binaryen itself) treats it as
+          // nullable.
+          break;
+        case HeapType::string:
+          o << S32LEB(BinaryConsts::EncodedType::stringref);
+          return;
+        case HeapType::stringview_wtf8:
+          o << S32LEB(BinaryConsts::EncodedType::stringview_wtf8);
+          return;
+        case HeapType::stringview_wtf16:
+          o << S32LEB(BinaryConsts::EncodedType::stringview_wtf16);
+          return;
+        case HeapType::stringview_iter:
+          o << S32LEB(BinaryConsts::EncodedType::stringview_iter);
+          return;
       }
     }
     if (type.isNullable()) {