Fix issues with __module__ and __doc__ descriptors.

Lib/functools.py

@@ -1047,6 +1047,17 @@ def __init__(self, unbound, obj, cls):
         self._dispatch = unbound.dispatcher.dispatch
         self._obj = obj
         self._cls = cls
+        # Set instance attributes which cannot be handled in __getattr__()
+        # because they conflict with type descriptors.
+        func = unbound.func
+        try:
+            self.__module__ = func.__module__
+        except AttributeError:
+            pass
+        try:
+            self.__doc__ = func.__doc__
+        except AttributeError:
+            pass
 
     def __call__(self, /, *args, **kwargs):
         if not args:
@@ -1057,19 +1068,13 @@ def __call__(self, /, *args, **kwargs):
         return self._dispatch(args[0].__class__).__get__(self._obj, self._cls)(*args, **kwargs)
 
     def __getattr__(self, name):
+        # Resolve these attributes lazily to speed up creation of
+        # the _singledispatchmethod_get instance.
         if name not in {'__name__', '__qualname__', '__isabstractmethod__',
                         '__annotations__', '__type_params__'}:
             raise AttributeError
         return getattr(self._unbound.func, name)
 
-    @property
-    def __module__(self):
-        return self._unbound.func.__module__
-
-    @property
-    def __doc__(self):
-        return self._unbound.func.__doc__
-
     @property
     def register(self):
         return self._unbound.register

Lib/test/test_functools.py

@@ -2911,6 +2911,7 @@ def static_func(arg: int) -> str:
         ):
             with self.subTest(meth=meth):
                 self.assertEqual(meth.__module__, __name__)
+                self.assertEqual(type(meth).__module__, 'functools')
                 self.assertEqual(meth.__qualname__, prefix + meth.__name__)
                 self.assertEqual(meth.__doc__,
                                  ('My function docstring'