Restore compatibility with Python 3.8

Author: AlexWaygood

Tools/clinic/clinic.py

@@ -5,6 +5,8 @@
 # Licensed to the PSF under a contributor agreement.
 #
 
+from __future__ import annotations
+
 import abc
 import ast
 import builtins as bltns
@@ -27,9 +29,15 @@
 import traceback
 import types
 
-from collections.abc import Callable
 from types import *
-from typing import Any, NamedTuple
+from typing import Any, Callable, Dict, NamedTuple, TYPE_CHECKING
+
+# types.NoneType only exists on Python 3.10+
+# type(None) isn't understood by type-checkers on <3.10 :(
+if TYPE_CHECKING:
+    from _typeshed import NoneType
+else:
+    NoneType = type(None)
 
 # TODO:
 #
@@ -1935,7 +1943,7 @@ def dump(self):
 # maps strings to Language objects.
 # "languages" maps the name of the language ("C", "Python").
 # "extensions" maps the file extension ("c", "py").
-LangDict = dict[str, Callable[[str], Language]]
+LangDict = Dict[str, Callable[[str], Language]]
 
 languages = { 'C': CLanguage, 'Python': PythonLanguage }
 extensions: LangDict = { name: CLanguage for name in "c cc cpp cxx h hh hpp hxx".split() }

Tools/clinic/cpp.py

@@ -1,10 +1,12 @@
+from __future__ import annotations
+
 import re
 import sys
-from collections.abc import Callable
+from typing import Callable, List, Tuple
 
 
-TokenAndCondition = tuple[str, str]
-TokenStack = list[TokenAndCondition]
+TokenAndCondition = Tuple[str, str]
+TokenStack = List[TokenAndCondition]
 
 def negate(condition: str) -> str:
     """

Tools/clinic/mypy.ini

@@ -1,6 +1,6 @@
 [mypy]
-# make sure clinic can still be run on Python 3.10
-python_version = 3.10
+# make sure clinic can still be run on Python 3.8
+python_version = 3.8
 pretty = True
 enable_error_code = ignore-without-code
 disallow_any_generics = True