Proposed warning: `assert <generator_expression>`

[gschaffner]

For example:

assert (result[i] == expected[i] for i in range(len(expected)))
assert (result[key] == expected[key] for key in result.keys() | expected.keys())

bugbear could warn and suggest adding all().

Note that even an empty generator expression is truey:

assert (False for _ in range(0))

so it's fine that bugbear doesn't statically know the length of the generator.

There are a couple of similar warnings:

• F631 is a similar rule for assert <tuple>.
• Proposal (2) in Couple new rule suggestions #440 is a similar rule for assert <constant>.

[JelleZijlstra]

Seems useful!

This could even be added to Python itself as a SyntaxWarning.

[cooperlees]

Sounds good to me too ... Thanks for the PR too. Will check it out.