Ecma262: Incorrect assertion in ForIn/OfHeadEvaluation

[jorendorff]

https://tc39.es/ecma262/#sec-runtime-semantics-forin-div-ofheadevaluation-tdznames-expr-iterationkind

Steps 7.a-b. say:

a. Assert: iterationKind is iterate.
b. If iterationKind is async-iterate, let iteratorHint be async.

The assertion rules out the condition on the next line.

[ljharb]

The implication is that the assertion should have been removed in #1066.

[jmdyck]

or else changed to: Assert: _iterationKind_ is ~iterate~ or ~async-iterate~.

[ljharb]

Good call, that seems better.

[ExE-Boss]

Or changed to:

1. If iterationKind is ~async-iterate~, then let iteratorHint be ~async~.
2. Else,
   1. Assert: iterationKind is ~iterate~.
   2. Let iteratorHint be ~sync~.

1. If _iterationKind_ is ~async-iterate~, then let _iteratorHint_ be ~async~.
1. Else,
    1. Assert: _iterationKind_ is ~iterate~.
    1. Let _iteratorHint_ be ~sync~.

This is used in ValidateAndApplyPropertyDescriptor § Step 2.d.