`ParamSpec` inferred overly wide from protocol

Bug Report

When implementing a protocol generic wrt a ParamSpec type inference ends up inferring Any for the param spec in certain cases. Writing code around the way the type checker works we can force it to unify against a properly inferred param spec, but this limits our ability to write nice APIs.

To Reproduce

from typing import Protocol, reveal_type

class Context: pass

class Namer[**P](Protocol):
    def name_for(self, *args: P.args, **kwargs: P.kwargs) -> str: ...

    def execute_on(
        self, ctx: Context, *args: P.args, **kwargs: P.kwargs
    ) -> None: ...

class Impl0:
    @staticmethod
    def name_for(x: int, y: str) -> str:
        return 'Test'
    @staticmethod
    def execute_on(ctx: Context, x: int, y: str):
        pass
    
class Impl1:
    @staticmethod
    def name_for(y: str) -> str:
        return 'Test'
    @staticmethod
    def execute_on(ctx: Context, x: int, y: str):
        pass

class UseImplFirst[**P, T]:
    def __init__(self, impl: T, *args: P.args, **kwargs: P.kwargs) -> None:
        self.impl = impl
        self.args = args
        self.kwargs = kwargs
    def __call__(self: UseImplFirst[P, Namer[P]]) -> None:
        pass

def useImplSecond[**P](impl: Namer[P], *args: P.args, **kwargs: P.kwargs):
    pass

def useImplThird[**P](wrapper: UseImplFirst[P, Namer[P]]) -> None:
    pass

__testImpl0: Namer[[int, str]] = Impl0
UseImplFirst(Impl0, 0, '0')()
useImplSecond(Impl0, 0, '0')
useImplThird(UseImplFirst(Impl0, 0, '0'))

__testImpl1: Namer[[int, str]] = Impl1    # Should fail (Fails)
UseImplFirst(Impl1, 1, '1')()             # Should fail (Succeeds)
useImplSecond(Impl1, 1, '1')              # Should fail (Succeeds)
useImplThird(UseImplFirst(Impl1, 1, '1')) # Should fail (Succeeds)

• Gist
• Playground (1.12.0)
• Playground (1.20.2)

Expected Behavior / Actual Behavior

See the snippet above.

Woraround
The following forces mypy to infer the ParamSpec first and unify against the protocol implementation later:

class UseImpl[**P]:
    def __init__(self, *args: P.args, **kwargs: P.kwargs):
        self.args = args
        self.kwargs = kwargs
    def __call__(self, impl: Namer[P]) -> None:
        pass


__testImpl0: Namer[[int, str]] = Impl0
UseImpl(0, '0')(Impl0)

__testImpl1: Namer[[int, str]] = Impl1 # Should fail (Fails)
UseImpl(1, '1')(Impl1)                 # Should fail (fails)

• gist
• Playground (1.20.2)

Beginne damit, den Reproducer aus dem Issue auszuführen und die Playgrounds von mypy 1.12.0 und 1.20.2 zu vergleichen. Verwende die erwarteten Fehler für Impl1 und den funktionierenden Workaround als Abschlusskriterien und füge Regressionstests in den relevanten Tests zur Typinferenz hinzu, sobald der Implementierungsbereich identifiziert ist.