Typecheck typeshed's code with pyright (#9793)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

tests/pytype_test.py

@@ -1,4 +1,6 @@
 #!/usr/bin/env python3
+# Lack of pytype typing
+# pyright: reportUnknownVariableType=false, reportUnknownMemberType=false, reportUnknownArgumentType=false, reportMissingTypeStubs=false
 """Test runner for typeshed.
 
 Depends on pytype being installed.
@@ -19,11 +21,14 @@ import traceback
 from collections.abc import Iterable, Sequence
 
 import pkg_resources
-from pytype import config as pytype_config, load_pytd  # type: ignore[import]
-from pytype.imports import typeshed  # type: ignore[import]
 
 from parse_metadata import read_dependencies
 
+assert sys.platform != "win32"
+# pytype is not py.typed https://github.com/google/pytype/issues/1325
+from pytype import config as pytype_config, load_pytd  # type: ignore[import]  # noqa: E402
+from pytype.imports import typeshed  # type: ignore[import]  # noqa: E402
+
 TYPESHED_SUBDIRS = ["stdlib", "stubs"]
 TYPESHED_HOME = "TYPESHED_HOME"
 _LOADERS = {}
@@ -155,7 +160,11 @@ def get_missing_modules(files_to_test: Sequence[str]) -> Iterable[str]:
     for distribution in stub_distributions:
         for pkg in read_dependencies(distribution).external_pkgs:
             # See https://stackoverflow.com/a/54853084
-            top_level_file = os.path.join(pkg_resources.get_distribution(pkg).egg_info, "top_level.txt")  # type: ignore[attr-defined]
+            top_level_file = os.path.join(
+                # Fixed in #9747
+                pkg_resources.get_distribution(pkg).egg_info,  # type: ignore[attr-defined]  # pyright: ignore[reportGeneralTypeIssues]
+                "top_level.txt",
+            )
             with open(top_level_file) as f:
                 missing_modules.update(f.read().splitlines())
     return missing_modules