bpo-46244: Remove __slots__ from typing.TypeVar, .ParamSpec (#30444)

* add missing __slots__ to typing._TypeVarLike

* add news entry

* remove slots from _TypeVarLike base classes

* cleanup diff

* fix broken link in blurb

Author: ariebovenberg

Lib/typing.py

@@ -805,9 +805,6 @@ def longest(x: A, y: A) -> A:
     Note that only type variables defined in global scope can be pickled.
     """
 
-    __slots__ = ('__name__', '__bound__', '__constraints__',
-                 '__covariant__', '__contravariant__', '__dict__')
-
     def __init__(self, name, *constraints, bound=None,
                  covariant=False, contravariant=False):
         self.__name__ = name
@@ -907,9 +904,6 @@ def add_two(x: float, y: float) -> float:
     be pickled.
     """
 
-    __slots__ = ('__name__', '__bound__', '__covariant__', '__contravariant__',
-                 '__dict__')
-
     @property
     def args(self):
         return ParamSpecArgs(self)

Misc/NEWS.d/next/Library/2022-01-06-21-31-14.bpo-46244.hjyfJj.rst

@@ -0,0 +1,2 @@
+Removed ``__slots__`` from :class:`typing.ParamSpec` and :class:`typing.TypeVar`.
+They served no purpose. Patch by Arie Bovenberg.