Loop with for ... of over a Map

[tiberiucorbu]

TypeScript Version: 2.1.6

Code

let entries: Map<string, string[]> = new Map<string, string[]>();
entries.set('a', ['foo'])
for (let entry of entries.values()) {
// do something with the entry
}

Expected behavior:
Since Typescript is advertised as a superset of ES6 than expected is that it should support es6 features. Therefor for ... of should work properly with IterableIterator as described here : https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Map

Actual behavior:
Compilation fails

TS2495: Type 'IterableIterator<string[]>' is not an array type or a string type.

[basarat]

The main complexity is the emit required for iterator support : http://babeljs.io/repl/#?babili=false&evaluate=true&lineWrap=false&presets=latest%2Creact%2Cstage-2&targets=&browsers=&builtIns=false&code=let%20entries%3A%20Map%3Cstring%2C%20string%5B%5D%3E%20%3D%20new%20Map()%3B%0Aentries.set('a'%2C%20%5B'foo'%5D)%0Afor%20(let%20entry%20of%20entries.values())%20%7B%0A%2F%2F%20do%20something%20with%20the%20entry%0A%7D&experimental=false&loose=false&spec=false&playground=true

TypeScript emitter doesn't have this support yet 🌹

[mhegazy]

This should be addressed by #12346 under --downlevelIteration. Make sure es2015 or es2015.iterable is part of your --lib arguments.