Don't treat return as a yield

[ghost]

Fixes #22298

See in particular the change to generatorTypeCheck14.types. This was working in #3031 but changed in #10676, likely just an oversight as that was a huge baseline change.

Also, changed checkAndAggregateYieldOperandTypes to no longer use pushIfUnique as @sandersn noted that getUnionType can handle duplicates already.

[DanielRosenwasser]

The feature is working as intended. The returned type becomes the value of an IteratorResult when done is true.

[DanielRosenwasser]

Example:

function* foo() {
  yield 1;
  yield 2;
  return 3;
}

var x = foo();
var r;
do {
  r = x.next()
  console.log(JSON.stringify(r))
} while (!r.done)

// {"value":1,"done":false}
// {"value":2,"done":false}
// {"value":3,"done":true}

[mhegazy]

The feature is working as intended. The returned type becomes the value of an IteratorResult when done is true.

we are currentlly not doing so...

for example yield undefined causes the function to return undefined.

[ghost]

@mhegazy you are probably confusing this with #22297? This is a different issue I happened to discover while doing that one.