Support matrix multiplication (@)

[spkersten]

The matrix multiplication operators @ and @= and their corresponding methods, __matmul__, __rmatmul__, and __imatmul__, that are introduced with Python 3.5 should be supported. See PEP 465.

[gilesc]

Was this fixed? I am using mypy v0.4.5 installed via pip3 (just getting started) and I get errors when using this feature. I haven't even started annotating anything yet.

I run mypy --python-version=3.5 -p mypackage, and get lots of errors like the following:

mypackage/distance.py: note: In function "nearest_neighbors":
mypackage/distance.py:57: error: Parse error before @

And the line referred to is:

r = Xa[:,j] @ Xa / (Xa.shape[0] - 1)

Since I use this feature heavily I get tons of such errors.

[gvanrossum]

Yeah, the default parser doesn't support that. We're moving to a new parser, which you can invoke with --fast-parser. Unfortunately that leads to raise RuntimeError('mypy does not support the MatMult operator') which becomes a crash, so it's just as bad. We'll have to fix this. Thanks for noticing!