Hello everyone! 

Recently I was curious about whether it is possible to create a fully typed `functools.partial` version. Because currently only return type is taken into account. 

So, I came up with the mypy plugin to type all the callable parameters during the partial application process and the final call. It works pretty well!

Source: https://github.com/dry-python/returns/blob/master/returns/curry.py#L7
Plugin: https://github.com/dry-python/returns/blob/master/returns/contrib/mypy/_curry.py
Tests: https://github.com/dry-python/returns/tree/master/typesafety/test_curry

I thought that mypy team might be interested in porting this (or similar) solution into the core. I would also be happy to receive any feedback on the code itself or the solution in general.

Thanks a lot for building mypy, it is awesome!

Nikita Sobolev