from __future__ import annotations

from typing import Callable

from mypy.plugin import MethodContext, Plugin

from mypy.types import CallableType, Type, get_proper_type

class MethodDecoratorPlugin(Plugin):

def get_method_hook(self, fullname: str) -> Callable[[MethodContext], Type] | None:

if "Foo.a" in fullname:

return method_decorator_callback

return None

def method_decorator_callback(ctx: MethodContext) -> Type:

default = get_proper_type(ctx.default_return_type)

if isinstance(default, CallableType):

str_type = ctx.api.named_generic_type("builtins.str", [])

return default.copy_modified(ret_type=str_type)

return ctx.default_return_type

def plugin(version: str) -> type[MethodDecoratorPlugin]:

return MethodDecoratorPlugin