Bug 1502355 - Make |WritableStreamDefaultWriterWrite| return a narrower |PromiseObject*| type for more clarity. r=arai

Differential Revision: https://phabricator.services.mozilla.com/D71115

js/src/builtin/streams/WritableStreamDefaultWriter.cpp

@@ -42,6 +42,7 @@ using JS::Value;
 
 using js::ClassSpec;
 using js::GetErrorMessage;
+using js::PromiseObject;
 using js::ReturnPromiseRejectedWithPendingError;
 using js::UnwrapAndTypeCheckArgument;
 using js::UnwrapAndTypeCheckThis;
@@ -502,7 +503,7 @@ static MOZ_MUST_USE bool WritableStreamDefaultWriter_write(JSContext* cx,
   }
 
   // Step 3: Return this.[[readyPromise]].
-  JSObject* promise =
+  PromiseObject* promise =
       WritableStreamDefaultWriterWrite(cx, unwrappedWriter, args.get(0));
   if (!promise) {
     return false;

js/src/builtin/streams/WritableStreamWriterOperations.cpp

@@ -312,7 +312,7 @@ bool js::WritableStreamDefaultWriterRelease(
  * Streams spec, 4.6.9.
  * WritableStreamDefaultWriterWrite ( writer, chunk )
  */
-JSObject* js::WritableStreamDefaultWriterWrite(
+PromiseObject* js::WritableStreamDefaultWriterWrite(
     JSContext* cx, Handle<WritableStreamDefaultWriter*> unwrappedWriter,
     Handle<Value> chunk) {
   cx->check(chunk);
@@ -351,7 +351,8 @@ JSObject* js::WritableStreamDefaultWriterWrite(
   }
 
   auto RejectWithStoredError =
-      [](JSContext* cx, Handle<WritableStream*> unwrappedStream) -> JSObject* {
+      [](JSContext* cx,
+         Handle<WritableStream*> unwrappedStream) -> PromiseObject* {
     Rooted<Value> storedError(cx, unwrappedStream->storedError());
     if (!cx->compartment()->wrap(cx, &storedError)) {
       return nullptr;

js/src/builtin/streams/WritableStreamWriterOperations.h

@@ -19,6 +19,7 @@ class JS_PUBLIC_API JSObject;
 
 namespace js {
 
+class PromiseObject;
 class WritableStreamDefaultWriter;
 
 extern JSObject* WritableStreamDefaultWriterAbort(
@@ -43,7 +44,7 @@ extern MOZ_MUST_USE bool WritableStreamDefaultWriterGetDesiredSize(
 extern MOZ_MUST_USE bool WritableStreamDefaultWriterRelease(
     JSContext* cx, JS::Handle<WritableStreamDefaultWriter*> unwrappedWriter);
 
-extern JSObject* WritableStreamDefaultWriterWrite(
+extern PromiseObject* WritableStreamDefaultWriterWrite(
     JSContext* cx, JS::Handle<WritableStreamDefaultWriter*> unwrappedWriter,
     JS::Handle<JS::Value> chunk);