Implementing fix suggested in #426

CHANGELOG.rst
    Added entry

line_profiler/line_profiler.py::LineProfiler._add_namespace(...)
    Removed unnecessary `typing.cast()` in default arguments

line_profiler/line_profiler_utils.py
    _StrEnum
        New alias which resolves:
        - Statically, always to `enum.StrEnum`
        - At the runtime, also thereto if available, and to
          `_StrEnumBase` otherwise
    StringEnum
        Now always "statically" inheriting from `_StrEnum` to make
        things less confusing to the type-checker

Author: TTsangSC

CHANGELOG.rst

@@ -6,6 +6,8 @@ Changes
 * FIX: Make sure that the profiled code is run in the
   ``sys.modules['__main__']`` namespace to avoid issues w/e.g. pickling
   (#423)
+* FIX: ``ScopingPolicy`` members now type-check properly as instances thereof
+  (#427)
 
 
 5.0.2

line_profiler/line_profiler.py

@@ -600,15 +600,9 @@ def _add_namespace(
         namespace: type | types.ModuleType,
         *,
         seen: set[int] | None = None,
-        func_scoping_policy: ScopingPolicy = cast(
-            ScopingPolicy, ScopingPolicy.NONE
-        ),
-        class_scoping_policy: ScopingPolicy = cast(
-            ScopingPolicy, ScopingPolicy.NONE
-        ),
-        module_scoping_policy: ScopingPolicy = cast(
-            ScopingPolicy, ScopingPolicy.NONE
-        ),
+        func_scoping_policy: ScopingPolicy = ScopingPolicy.NONE,
+        class_scoping_policy: ScopingPolicy = ScopingPolicy.NONE,
+        module_scoping_policy: ScopingPolicy = ScopingPolicy.NONE,
         wrap: bool = False,
         name: str | None = None,
     ) -> int:

line_profiler/line_profiler_utils.py

@@ -46,7 +46,14 @@ def __str__(self) -> str:
         return self.value
 
 
-class StringEnum(getattr(enum, 'StrEnum', _StrEnumBase)):  # type: ignore[misc]
+try:
+    from enum import StrEnum as _StrEnum
+except ImportError:
+    if not typing.TYPE_CHECKING:  # Don't confuse the typechecker
+        _StrEnum = _StrEnumBase
+
+
+class StringEnum(_StrEnum):
     """
     Convenience wrapper around :py:class:`enum.StrEnum`.