I'm submitting a ...

[x] bug report => search github for a similar issue or PR before submitting

Current behavior
Silence

Expected behavior
Syntax error

Minimal reproduction of the problem with instructions

*ngFor="let elem of elements; let i of index"

Notice the "of index", which should be "= index".

Got no errors of any sorts, but the behavior is the same as "i = elem", leading to nasty runtime bugs.

What is the motivation / use case for changing the behavior?
To avoid spending hours on stupid bugs like that.

Please tell us about your environment:

• Angular version: 2.0.X
  Latest officially released 4

• Browser:
  all

• Language:
  TypeScript 2