[esnext] prototype runtime implementation for async functions

src/js/promise.js

Index: src/js/promise.js
diff --git a/src/js/promise.js b/src/js/promise.js
index 65a8bf3f4ddf0ec598c7c0a21067dff943a5ea66..c12270996b1cf96da3aed90ba928ed49c1bfdd60 100644
--- a/src/js/promise.js
+++ b/src/js/promise.js
@@ -293,6 +293,19 @@ function PromiseReject(r) {
   }
 }
 
+// Shortcut Promise.reject and Promise.resolve() implementations, used by
+// Async Functions implementation.
+function PromiseCreateRejected(r) {
+  var promise = PromiseCreateAndSet(-1, r);
+  %PromiseRejectEvent(promise, r, false);
+  return promise;
+}
+
+function PromiseCreateResolved(x) {
+  if (IsPromise(x) && x.constructor === GlobalPromise) return x;
+  return PromiseCreateAndSet(+1, x);
+}

[Dan Ehrenberg, 2016/05/04 22:52:36]

This seems like a good optimization. Maybe in a separate patch, we could
refactor PromiseResolve and PromiseReject to use them if this === GlobalPromise.
That would make me a bit more comfortable with respect to testing, since there
are already a bunch of tests for those directly, both in mjsunit and test262.
Another alternative to the same end would be to just put PromiseResolve and
PromiseReject on the context (renaming the RejectPromise/FuifillPromise entries
appropriately) and call out to those directly. Either way, the testing surface
is reduced. Normally I wouldn't be so picky, but we had so many bugs with
Promise correctness.

+
 // ES#sec-promise.prototype.then
 // Promise.prototype.then ( onFulfilled, onRejected )
 // Multi-unwrapped chaining with thenable coercion.
@@ -487,6 +500,8 @@ utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [
   "promise_reject", RejectPromise,
   "promise_resolve", FulfillPromise,
   "promise_then", PromiseThen,
+  "promise_create_rejected", PromiseCreateRejected,
+  "promise_create_resolved", PromiseCreateResolved
 ]);
 
 // This allows extras to create promises quickly without building extra
@@ -506,6 +521,10 @@ utils.Export(function(to) {
   to.PromiseChain = PromiseChain;
   to.PromiseDefer = PromiseDefer;
   to.PromiseAccept = PromiseAccept;
+
+  to.PromiseCreateRejected = PromiseCreateRejected;
+  to.PromiseCreateResolved = PromiseCreateResolved;
+  to.PromiseThen = PromiseThen;
 });
 
 })