Python version check not recognized if sys not named sys about mypy HOT 1 CLOSED

PEP 484 states:

Type checkers are expected to understand simple version and platform checks, e.g.:

import sys

if sys.version_info[0] >= 3:
    # Python 3 specific definitions
else:
    # Python 2 specific definitions

if sys.platform == 'win32':
    # Windows specific definitions
else:
    # Posix specific definitions

Don’t expect a checker to understand obfuscations like "".join(reversed(sys.platform)) == "xunil".

Emphasis here on "simple" :)

Mypy doesn't have an arbitrary understanding of constructs like this; it has to heavily special-case each version of this kind of condition that it supports. I think we're pretty unlikely to add support for aliasing sys in this way anytime soon, I'm afraid :)

from mypy.