only use typing_extensions for older python versions

pyproject.toml

@@ -27,7 +27,7 @@ classifiers = [
 dependencies = [
     "setuptools>=62.4",
     "semantic_version>=2.8.2,<3",
-    "typing_extensions>=3.7.4.3",
+    'typing_extensions>=3.7.4.3; python_version<"3.9"',
     'tomli>=1.2.1; python_version<"3.11"'
 ]
 

setuptools_rust/build.py

@@ -24,7 +24,11 @@
 from setuptools.command.build import build as CommandBuild
 from setuptools.command.build_ext import build_ext as CommandBuildExt
 from setuptools.command.build_ext import get_abi3_suffix
-from typing_extensions import Literal
+
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
 
 from ._utils import format_called_process_error
 from .command import RustCommand

setuptools_rust/extension.py

@@ -2,14 +2,19 @@
 import os
 import re
 import subprocess
+import sys
 import warnings
 from setuptools.errors import SetupError
 from enum import IntEnum, auto
 from functools import lru_cache
 from typing import Any, Dict, List, NewType, Optional, Sequence, Union, cast
 
 from semantic_version import SimpleSpec
-from typing_extensions import Literal
+
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
 
 from ._utils import format_called_process_error
 

setuptools_rust/setuptools_ext.py

@@ -14,7 +14,11 @@
 from setuptools.command.install_scripts import install_scripts
 from setuptools.command.sdist import sdist
 from setuptools.dist import Distribution
-from typing_extensions import Literal
+
+if sys.version_info >= (3, 8):
+    from typing import Literal
+else:
+    from typing_extensions import Literal
 
 from .build import _get_bdist_wheel_cmd
 from .extension import Binding, RustBin, RustExtension, Strip