Fix typing

Author: kdeldycke

meta_package_manager/base.py

@@ -36,7 +36,7 @@
 from click_extra.colorize import default_theme as theme
 from click_extra.envvar import env_copy
 from click_extra.testing import INDENT, args_cleanup, format_cli_prompt
-from extra_platforms import UNIX, Group, current_platforms
+from extra_platforms import UNIX, Group, Platform, current_platforms
 from packageurl import PackageURL
 
 from .version import TokenizedString, parse_version
@@ -577,9 +577,16 @@ def version(self) -> TokenizedString | None:
     @cached_property
     def supported(self) -> bool:
         """Is the package manager supported on that platform?"""
-        # At this point self.platforms is normalized as a frozenset of Platform
-        # instances.
-        return len(self.platforms.intersection(current_platforms())) > 0
+        return (
+            len(
+                # XXX At this point self.platforms is normalized as a frozenset of
+                # Platform instances.
+                cast("frozenset[Platform]", self.platforms).intersection(
+                    current_platforms()
+                )
+            )
+            > 0
+        )
 
     @cached_property
     def executable(self) -> bool: