modules as protocols doesn't type-check against the protocol #13771

Bug Report

I was really excited to see #13513 merge but trying it out seems like it doesn't actually type-check things

here's a small example

# main.py
from typing import Protocol

class P(Protocol):
    def f(self) -> str: ...

import t
t_p: P = t  # expect an error here, it does not match P

# t.py
def f() -> int:
    return 6

I expect this to error because the f inside t returns int but the protocol specifies it should return str.

additionally, I think I should also be able to write something like this, but it currently errors for an unrelated reason (even when the module matches the protocol):

from typing import Protocol

class P(Protocol):
    def f(self) -> str: ...

t: P
import t  # error: Name "t" already defined on line 6

Your Environment

• Mypy version used: 0.981
• Mypy command-line flags: mypy main.py
• Mypy configuration options from mypy.ini (and other config files): n/a
• Python version used: 3.8.10