async arrow function masks "Promise is not defined" errors.

[DanielRosenwasser]

// foo.ts
/*start*/(async (a) => {
})/*end*/

Promise.all([]);

{
  "compilerOptions": {
    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
    "strict": true,                           /* Enable all strict type-checking options. */
  }
}

1. Open up an editor session

Expected

'Promise' only refers to a type, but is being used as a value here. Do you need to change your target library? Try changing the `lib` compiler option to es2015 or later.ts(2585)

Actual

No errors!!!

Try deleting from /*start*/ to /*end*/ and you correctly get an error!

[DanielRosenwasser]

First time this behavior is observable is [email protected]. I suspect that this is also related to #37522.

[sandersn]

Like #37522, no longer repros on master.