Detect type hints: PEP484

Is it really necessary to have the unused imports for the typing comments to work?

asmeurer I've asked repeatedly that it not be necessary. That said, mypy-lang folks continue to insist it is necessary.

Regardless, I don't think pyflakes wants to do PEP 484 work since that's mypy-lang's area of expertise Thomas. Further, pyflakes needs a better AST considering the current one does *not* preserve comments. Without preserving comments, PyFlakes cannot introspect comments for # type: Foo to find that it is being used.

https://github.com/dropbox/typed_ast is a fork of the AST module that preserves type comments (and is used by mypy-lang); using that might be an option for allowing pyflakes to support the Python 2 type comment syntax.

Apart from whether or not pyflakes intends to support type hinting, it currently marks it as a syntax error (on arguments and return types):

def echo(arg: str) -> str:
    return arg

It marks invalid syntax at the first colon, and at the dash if the type hint on argument is removed.

Make sure your pyflakes is running in Python 3. Pyflakes detects syntax errors based on the version of Python it is running from. If you run pyflakes from Python 2 on Python 3-only code, it will complain about syntax errors. The easiest way to do this is to run

python3 -m pyflakes yourfile.py

Oh, oops. Found that just a few minutes ago when I was going to file something similar for keyword-only args. Was running pyflakes at two removes (via prospector, through the "syntastic" vim plugin), and didn't realize that it wasn't automatic for versions.

Please fix the imported but unused errors for the typing library.

I'm running into those when adding type hints to my python code.

Currently doing:

 from typing import Any, Dict, List, Tuple, Union # noqa

As a work-around.