Improve abc module and builtin function decorators (#5703)

stdlib/abc.pyi

@@ -1,8 +1,11 @@
 import sys
 from _typeshed import SupportsWrite
-from typing import Any, Callable, TypeVar
+from collections.abc import Callable
+from typing import Any, Generic, TypeVar
+from typing_extensions import Literal
 
 _T = TypeVar("_T")
+_R_co = TypeVar("_R_co", covariant=True)
 _FuncT = TypeVar("_FuncT", bound=Callable[..., Any])
 
 # These definitions have special processing in mypy
@@ -16,12 +19,15 @@ class ABCMeta(type):
 
 def abstractmethod(funcobj: _FuncT) -> _FuncT: ...
 
+class abstractclassmethod(classmethod[_R_co], Generic[_R_co]):
+    __isabstractmethod__: Literal[True]
+    def __init__(self: abstractclassmethod[_R_co], callable: Callable[..., _R_co]) -> None: ...
+
+class abstractstaticmethod(staticmethod[_R_co], Generic[_R_co]):
+    __isabstractmethod__: Literal[True]
+    def __init__(self, callable: Callable[..., _R_co]) -> None: ...
+
 class abstractproperty(property): ...
-
-# These two are deprecated and not supported by mypy
-def abstractstaticmethod(callable: _FuncT) -> _FuncT: ...
-def abstractclassmethod(callable: _FuncT) -> _FuncT: ...
-
 class ABC(metaclass=ABCMeta): ...
 
 def get_cache_token() -> object: ...