Add missing checks to Promise.resolve and Promise.reject.

[cscott]

These checks were overlooked when @@species was resolved from these methods.

Discovered by running the ES2015 test262 test suite against es6-shim.

[ljharb]

Ah, thanks - could we add test coverage for these to this repo also?

[ljharb]

These checks are already covered by IsConstructor inside PromiseCapability - I added 3d5bc93 to be sure.

Can you share the test262 test conditions that cause a failure without this PR's changes?

[cscott]

It's the built-ins/Promise/resolve/context-non-object-with-promise.js test case which is failing. It passes undefined as the context object, but a valid Promise as the argument, so it never gets to the check in IsConstructor. I added PR #381 to demonstrate how test262 test cases could be run on es6-shim, which should let you reproduce the failure.

[ljharb]

The only difference I see in the test262 tests is that they're voiding the constructor property on the promise they pass in - however, looking at es6-shim's code path for resolve/reject, they both immediately do effectively new PromiseCapability(this), which in its first line throws if IsConstructor fails for the argument, which it would for any non-function "this" value.

I definitely see the test failing in #381 but I'm mystified as to why.

[ljharb]

aha, although Promise.reject already works fine, Promise.resolve has an ES.IsPromise check inside it.

[ljharb]

@cscott Why does resolve have that check but not reject?

[ljharb]

I'm pursuing that question with the committee members, but in the meantime, if you could freshly rebase this on top of latest master I'd love to merge it ASAP. Thanks!

[cscott]

Rebased.

[ljharb]

Thanks!