Iterator in for ... of loop transpiled to use length property which is undefined

[jasonpang]

TypeScript Version: nightly (2.2.0-dev.20161118)

Chrome Version: Stable 54.0.2840.99 (Official Build) m (64-bit) (Revision 7eca4ce1e662f12cadaf96c30cd2335fd03e7140-refs/branch-heads/2840@{#830})

TypeScript Code: (relevant portion)

for (var param of iterator) {

Transpiled ES5 JavaScript (relevant portion):

 for (... ; _i < iterator_1.length; _i++) {
                 ^^^^^^^^^^^^^^^^^
                 length is undefined

Screenshot of Transpiled ES5 Code:

Expected behavior:
Using for (var x of iterator) { ... } should be transpiled correctly.

Actual behavior:
The iterator loop is transpiled to use the length property which appears to be undefined for the iterator.

Reproducible Project

For some reason, GitHub isn't allowing me to upload a .zip file, so here's a Google Drive link to the project ZIP: https://goo.gl/xvbwHu.

[kitsonk]

That would have been a compile time error.

Dupe of #11209 and others...

[jasonpang]

Makes sense, I also see this at the bottom here: https://www.typescriptlang.org/docs/handbook/iterators-and-generators.html

Closing since this is a documented issue and there are other open issues about this.