async/await checks are too aggressive and even escape type: ignore

[timabbott]

I happen to use a third-party library (Mandrill) that has various functions that take the async keyword:

https://mandrillapp.com/api/docs/index.python.html

The error is this, and it applies even if you add a type: ignore on the affected line:
/tmp/foo.py:1: error: 'async' and 'await' will become reserved keywords in Python 3.7

def foo(async=True):                                                                                 
    pass                                                                                             
                                                                                                     
foo(async=False)  # type: ignore                                                                     

You get the same thing with even this:

x = dict(async=False)  # type: ignore                                                                

Other keywords don't have this problem (x = dict(type=False) works fine), so I think this is just a bug with this new friendly check for new keywords.

I worked around this by passing **{'async': False} instead, but it's kinda absurd.

[JelleZijlstra]

I ran into this too. It might be an issue with typed-ast instead but I haven't looked into details yet.

[gvanrossum]

There are two meanings of the term "keyword". Here, async and await will become reserved words of the language. type is just a "keyword argument". This really means that Mandrill will have to change.

Yet until then I agree that it would be nice if we could suppress the warning somehow. That may require a typed-ast change. @ddfisher?

[ddfisher]

Oops, this is definitely a bug in typed-ast. I accidentally turned a conditional warning into an unconditional error when making some fixes for Python 3.3 compatibility. I don't think it's typed-ast's place to warn about this error, so I'm going to remove it instead.

[ddfisher]

I'll release 1.0.2 to PyPI as soon as the wheels finish building.

[ddfisher]

Released typed-ast 1.0.2.