Reassigned method raises "signature incompatible with supertype"

Bug Report

A rather simple class with an aliased method raises "signature incompatible with supertype" - which seems to happen due to the method name (i can't really find something else that's wrong).

To Reproduce

class A:
    def hello(self, a: str, b: str):
        pass

    world = hello

class B(A):
    # Also tried without ":A" on the self argument
    def world(self: A, a: str, b: str):
        # Do something slightly different when child-class is the instance
        pass

Expected Behavior

Mypy should pass - as the function signature is correct except for the method name.
It should obviously flag if an argument is missing (or named wrongly).
The only workaround to the above error is to actually implement world in the parent class - which is obviously what i'd like to avoid as that'll be unnecessary code, and one unnecessary additional function call and nesting level.

# type: ignore[override] on the "world" method does not circumvent this problem

Actual Behavior

mypy_decoroator.py:12: error: Signature of "world" incompatible with supertype "A"
mypy_decoroator.py:12: note:      Superclass:
mypy_decoroator.py:12: note:          def hello(self: A, a: str, b: str) -> Any
mypy_decoroator.py:12: note:      Subclass:
mypy_decoroator.py:12: note:          def world(self, a: str, b: str) -> Any

(Write what happened.)

Your Environment

• Mypy version used:0.942
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): n/A
• Python version used: 3.9.7
• Operating system and version: linux

Start with the minimal class A/B reproducer in the issue and run mypy against it to confirm the reported diagnostic. Trace how the aliased method is compared with the superclass method; done when the compatible alias is accepted while missing or incorrectly named arguments still produce an override error.