detect compare used instead of an iterable

Seems like part of a larger issue of propagating type inference from literals. int.__eq__(int) returns bool; bool.__iter__() raises TypeError. I would love to see pyflakes do this, but it would be better to do it in a generic way, rather than picking and choosing random examples.

Note that == for general objects could return anything because of __eq__ (and there are definitely some libraries that use it as syntactic sugar).

In particular, if a and b are numpy arrays, then a == b is a numpy array (which is iterable).

Ya, sorry this is a specific case. I found it while working on https://github.com/PyCQA/pycodestyle/issues/371#issuecomment-240614113 , and thought I better raise it here before I forgot it.

It is unfortunate that it can only easily be done for literals and built in types, and needs to understand the classes possibly defined in other modules before it could reliably work for anything else.

Im not sure how valuable it is if it only supports literals and built in types.

I think if it were done generically it would be very useful, because it would catch a lot of typos. Even just spellchecking attribute names on literals would help me out personally quite a bit.