Require argument names to match in Protocol

Feature

Currently mypy does not check that argument names in functions that implement protocols match the argument names in the protocol. This fails when arguments are passed as keywords.

For example, this passes mypy:

from typing import Protocol

class MyProtocol(Protocol):
    def foo(self, a: int) -> None: ...

class MyObject:
    def foo(self, b: int) -> None:
        pass

def call_foo(obj: MyProtocol) -> None:
    obj.foo(a=1)

call_foo(MyObject())

but fails at runtime:

Traceback (most recent call last):
  File "/Users/sidharthkapur/protocol_test.py", line 13, in <module>
    call_foo(MyObject())
  File "/Users/sidharthkapur/protocol_test.py", line 11, in call_foo
    obj.foo(a=1)
TypeError: MyObject.foo() got an unexpected keyword argument 'a'

Pitch

If we checked this in mypy, we could prevent runtime errors like the one above.

issue にある Protocol と MyObject の再現コードから始め、それを mypy にかけて現在の動作を確認します。Protocol の実装互換性チェックを追跡し、引数名が一致しない場合とキーワード呼び出しのカバレッジを追加します。完了条件は、mypy が互換性のない実装を拒否しつつ、有効な Protocol 実装を引き続き受け入れることです。