Support type hints for Python 2.7 and straddling code

[hackerkid]

from typing import List

def hello(): # type: () -> None
    print 'hello'

class Example:
    def method(self, lst, opt=0, *args, **kwargs):
        # type: (List[str], int, *str, **bool) -> int
        print("Do stuff")

Running autoflake --remove-all-unused-imports would remove from typing import List. This should not be the case as List import is used for defining the type.

• https://www.python.org/dev/peps/pep-0484/#suggested-syntax-for-python-2-7-and-straddling-code
• mypy is a static type checker for Python and uses type annotation in comments for supporting python2.7 code. http://mypy.readthedocs.io/en/latest/python2.html
• http://blog.zulip.org/2016/10/13/static-types-in-python-oh-mypy/

[myint]

autoflake is just removing what pyflakes reports, so it might be good to report it there.

[jaens]

Looks like there's already an issue about type comments for pyflakes: PyCQA/pyflakes#247

[asottile]

this should just work now with the latest pyflakes 2.x after my patch here: PyCQA/pyflakes#400