from typing import Callable, TypeVar
from abc import ABC, abstractmethod
class Base(ABC):
 @abstractmethod
 def func(self, arg: int | str, /) -> int:
 pass
BaseT = TypeVar("BaseT", bound=Base, contravariant=True) # used to type the `self` argument
def handle_int(func: Callable[[BaseT, str], int], /) -> Callable[[BaseT, int | str], int]:
 # A wrapper would be defined to convert ints to strings
 ...
class Impl(Base):
 @handle_int # Breaks if Base.func doesn't have the pos. only '/' marker
 def func(self, arg: str) -> int:
 return 1
 def other(self):
 reveal_type(self.func) # (int | str) -> int

from typing import Callable, Protocol, TypeVar, Self, overload
from abc import ABC, abstractmethod
class Base(ABC):
 @abstractmethod
 def func(self, arg: int | str) -> int:
 pass
BaseT = TypeVar("BaseT", bound=Base, contravariant=True)
class BoundFuncProto(Protocol):
 def __call__(self, arg: int | str) -> int: ...
class FuncProto(Protocol[BaseT]):
 def __call__(_self, self: BaseT, arg: int | str) -> int: ...
 # Trying to define `__get__`, as suggested in other discussions, and to make it work
 # with instance vs class access, but to no eval:
 @overload
 def __get__(self, obj: None, objtype: type[Base] | None = ..., /) -> Self: ...
 @overload
 def __get__(self, obj: BaseT, objtype: type[BaseT] | None = ..., /) -> BoundFuncProto: ...
def handle_int(func: Callable[[BaseT, str], int], /) -> FuncProto[BaseT]:
 # A wrapper would be defined to convert ints to strings
 ...
class Impl(Base):
 @handle_int
 def func(self, arg: str) -> int: # "func" overrides method of same name in class "Base" with incompatible type "FuncProto[Impl]"
 return 1
 def other(self):
 reveal_type(self.func) # BoundFuncProto
 self.func(1) # type checks
reveal_type(Impl.func) # FuncProto[Impl]