Chrome Version: (copy from chrome://version)
OS: (e.g. Win7, OSX 10.9.5, etc...)

What steps will reproduce the problem?
(1) try executing for (var x of 1) { }
(2) now try executing new Set(1,2,3)

What is the expected result?

Two reasonable error messages (e.g. "Uncaught TypeError: 1 is not iterable")

What happens instead?
The for loop produces a reasonable error message, but the Set constructor says:
"Uncaught TypeError: undefined is not a function"

This is reasonably important because it's easy to accidentally omit the list square-brackets when constructing sets (e.g. writing new Set(1,2,3) instead of new Set([1,2,3])) - we should make it super easy to catch and fix this mistake.