MyPy typechecking method names that clash with other types

[alanhdu]

Using mypy 0.560 (and with the current master) and python 3.6.4, typechecking the following function:

class A:
    def int(self) -> int:
        return 5

fails with:

test.py:2: error: Invalid type "test.A.int"

In general, it looks like if I define a method with the name of a type, I can no longer use that type in return annotations in that class.

[ilevkivskyi]

I think this is a duplicate of #3775

The workaround is to use import builtins and then builtins.int.