The following code is currently consistent with the type hint syntax but contains a line that is completely ignored.

   >>> d = {}
   >>> d['a']: int
   >>> d
   {}
   >>> __annotations__
   {}
    >>> '__annotations__' in dir(d)
   False

I believe that type hints that cannot be either attached to an object nor added to any other __annotations__ dict should either generate a SyntaxError or, at the very least, result in a warning.