No current plans to pursue this upstream.
Generators can't "return" until PHP 7:
PHP has a setting called post_max_size. If a POST request is larger than this size, PHP does not populate $_POST or $_FILES.
Wed, Apr 8
This also updates the XHPAST linter to target PHP 5.5 (see T13492); it complained about Generator otherwise.
XHPAST currently can't build an AST for $result = yield ..., even though this is a valid construct. This is probably a straightforward fix.
Tue, Apr 7
Superseded by D21066.
Much of this is supported now; T13492 has some general followup.
Test failures are expected.
(This was ultimately superseded by D21065.)
This is entangled with T9753.
XHPAST currently can not parse $x = yield $y;. I suspect this was added to the PHP grammar after XHPAST diverged. I'm hopeful the fix is straightforward.
No current plans to pursue this.