Fix overloaded static methods on instances (#13482)

mypy/checkmember.py

@@ -302,7 +302,7 @@ def analyze_instance_member_access(
  mx.msg.cant_assign_to_method(mx.context)
  signature = function_type(method, mx.named_type("builtins.function"))
  signature = freshen_function_type_vars(signature)
- if name == "__new__":
+ if name == "__new__" or method.is_static:
  # __new__ is special and behaves like a static method -- don't strip
  # the first argument.
  pass
@@ -315,6 +315,8 @@ def analyze_instance_member_access(
  signature, dispatched_type, method.is_class, mx.context, name, mx.msg
  )
  signature = bind_self(signature, mx.self_type, is_classmethod=method.is_class)
+ # TODO: should we skip these steps for static methods as well?
+ # Since generic static methods should not be allowed.
  typ = map_instance_to_supertype(typ, method.info)
  member_type = expand_type_by_instance(signature, typ)
  freeze_type_vars(member_type)

test-data/unit/check-overloading.test

@@ -6527,3 +6527,20 @@ class Test:
  def foo(self, arg: Sequence[A]) -> None: ...
  def foo(self, arg: Union[Sequence[E], Sequence[A]]) -> None:
  ...
+
+[case testOverloadedStaticMethodOnInstance]
+from typing import overload
+
+class Snafu(object):
+ @overload
+ @staticmethod
+ def snafu(value: bytes) -> bytes: ...
+ @overload
+ @staticmethod
+ def snafu(value: str) -> str: ...
+ @staticmethod
+ def snafu(value):
+ ...
+reveal_type(Snafu().snafu('123')) # N: Revealed type is "builtins.str"
+reveal_type(Snafu.snafu('123')) # N: Revealed type is "builtins.str"
+[builtins fixtures/staticmethod.pyi]