B909 improvements

[mimre25]

B909 improvements

[JelleZijlstra]

Thanks for writing this up.

Assign and AnnAssign can be ignored, since they just rebind the name, they do not mutate the container. (foo: T += 3 and similar are syntax errors.) Similarly, I wouldn't worry about the attribute setting mechanisms (setattr/delattr/etc.), because you can't set an attribute on builtin containers like list, tuple, set, and dict. There could be user-defined subclasses where setting an attribute interferes with iteration, but that feels too speculative for a lint rule.

[mimre25]

A good catch with Assign and AnnAssign.

Regarding the syntax errors: you're right - AugAssign and AnnAssign cannot be mixed.

What do you think about del?
Should we also remove that, when it only targets the container itself instead of an element inside of it?

[JelleZijlstra]

We should catch del container[i], but not del container.

[mimre25]

Sounds good to me.

I'll implement these improvements some time next week 🙂