[Generators] not correct "this" binding in v20180319

[teppeis]

Degraded in v20180319
https://kangax.github.io/compat-table/es6/#test-generators_correct_this_binding

input

// functions / generators / correct "this" binding
module.exports = function() {
  function* generator() {
    yield this.x;
    yield this.y;
  }
  var iterator = { g: generator, x: 5, y: 6 }.g();
  var item = iterator.next();
  var passed = item.value === 5 && item.done === false;
  item = iterator.next();
  passed &= item.value === 6 && item.done === false;
  item = iterator.next();
  passed &= item.value === undefined && item.done === true;
  return passed;
};

output

• output in v20180204: PASS
• output in v20180319: FAIL

[MatrixFrog]

It turns out the generator transpilation is doing things correctly but then the "fold constants" pass is producing invalid code. It didn't do this in the previous release because the generator function was brought into the object literal before "fold constants":

function *generator() {...}
{g:generator, x:5, y:6}

became

{*g() {...}, x:5, y:6}

but in the new compiler that does not happen. Will do a bisect and figure out where this changed.

[teppeis]

@MatrixFrog Fixed in v20180506. Thanks!