`map` has a problem with generic types

[sambhav]

Note: if you are reporting a wrong signature of a function or a class in
the standard library, then the typeshed tracker is better suited
for this report: https://github.com/python/typeshed/issues

Please provide more information to help us understand the issue:

• Are you reporting a bug, or opening a feature request?
  bug
• Please insert below the code you are checking with mypy,
  or a mock-up repro if the source is private. We would appreciate
  if you try to simplify your case to a minimal repro.

from typing import TypeVar
T = TypeVar("T")
def foo(bar: T) -> T:
    return bar
map(foo, [1])

• What is the actual behavior/output?
  error: Argument 1 to "map" has incompatible type "Callable[[T], T]"; expected "Callable[[int], T]"

• What is the behavior/output you expect?
  For mypy to successfully pass

• What are the versions of mypy and Python you are using?
  Python 3.7.1 and the mypy-0.710+dev.f0491839adf2db2da74768b1d01f8e244e769f59
  Do you see the same issue after installing mypy from Git master?
  Yes

• What are the mypy flags you are using? (For example --strict-optional)
  None

• If mypy crashed with a traceback, please paste
  the full traceback below.

(You can freely edit this text, please remove all the lines
you believe are unnecessary.)

[ilevkivskyi]

Duplicate of #6697