Mypy incorrectly says signature is incompatible with supertype when using decorator #3260
Description
When checking the code below with mypy v0.501, mypy complains that
deco.py:10: error: Signature of "a" incompatible with supertype "A"
According to @ilevkivskyi this may be related to #1441.
import functools
class A:
@functools.lru_cache()
def a(self) -> str:
return 'a'
class B(A):
@functools.lru_cache()
def a(self) -> str:
return super().a() + 'b'