Wrong overload signatures with @overload and @staticmethod

[aaron-skydio]

Bug Report

When given the following file, mypy does not produce the correct signatures for the two overloads of __call__:

from typing import overload, Callable, TypeVar, Optional, Any, Union


class SingletonAPI:
    F = TypeVar("F", bound=Callable[..., Any])

    # Bare decorator usage
    @overload
    @staticmethod
    def __call__(func: F) -> F:
        ...

    # Decorator with arguments
    @overload
    @staticmethod
    def __call__(
        *,
        show_spinner: bool = True,
    ) -> Callable[[F], F]:
        ...

    @staticmethod
    def __call__(
        func: Optional[F] = None,
        *,
        show_spinner: bool = True,
    ) -> Any:
        ...


singleton = SingletonAPI()


@singleton
def f(a: bool) -> str:
    pass


@singleton(show_spinner=True)
def g(a: bool) -> str:
    pass

To Reproduce

Run mypy on the above file. We've tested on mypy 0.942 and mypy-0.950+dev.74df7fb1172993af3b2456765fb8368481ef0ab9

Expected Behavior

As best we can tell, the above usage is correct, and we expect mypy to find no errors in this code.

Actual Behavior

Mypy emits the following errors on this code:

fails.py:34: error: No overload variant of "__call__" of "SingletonAPI" matches argument type "Callable[[bool], str]"
fails.py:34: note: Possible overload variants:
fails.py:34: note:     def __call__(func) -> SingletonAPI
fails.py:34: note:     def __call__(show_spinner) -> Callable[[F], F]
fails.py:39: error: No overload variant of "__call__" of "SingletonAPI" matches argument type "bool"
fails.py:39: note: Possible overload variants:
fails.py:39: note:     def __call__(func) -> SingletonAPI
fails.py:39: note:     def __call__(show_spinner) -> Callable[[F], F]
Found 2 errors in 1 file (checked 1 source file)

If we apply the following fix to the above file to make __call__ an instance method instead of static, it passes:

--- fails.py    2022-04-11 23:37:13.397162142 -0700
+++ passes.py   2022-04-11 23:37:29.197661252 -0700
@@ -6,21 +6,23 @@
 
     # Bare decorator usage
     @overload
-    @staticmethod
-    def __call__(func: F) -> F:
+    # @staticmethod
+    def __call__(self, func: F) -> F:
         ...
 
     # Decorator with arguments
     @overload
-    @staticmethod
+    # @staticmethod
     def __call__(
+        self,
         *,
         show_spinner: bool = True,
     ) -> Callable[[F], F]:
         ...
 
-    @staticmethod
+    # @staticmethod
     def __call__(
+        self,
         func: Optional[F] = None,
         *,
         show_spinner: bool = True,

Your Environment

• Mypy version used: 0.942, and mypy-0.950+dev.74df7fb1172993af3b2456765fb8368481ef0ab9
• Mypy command-line flags: --python-version=3.6 through 3.10
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.8 and 3.10
• Operating system and version: Ubuntu Linux

[AlexWaygood]

This looks like it might be a duplicate of #7781? :)

[aaron-skydio]

It certainly does :)
I swear I searched...

[AlexWaygood]

No worries! Mypy has a lot of open issues :)