fix: appease mypy

src/awkward/_namedaxis.py

@@ -308,6 +308,17 @@ def _prepare_named_axis_for_attrs(
     return _named_axis
 
 
+def _make_named_int_class(name: tp.Any) -> type[int]:
+    class NamedInt(int):
+        def __repr__(self):
+            value_repr = super().__repr__()
+            return f"{name!r} (named axis) -> {value_repr} (pos. axis)"
+
+        __str__ = __repr__
+
+    return NamedInt
+
+
 def _named_axis_to_positional_axis(
     named_axis: AxisMapping,
     axis: AxisName,
@@ -337,16 +348,14 @@ def _named_axis_to_positional_axis(
         # in order to properly display it in error messages. This is useful for cases
         # where the positional axis is pointing to a non-existing axis. The error message
         # will then show the original (named) axis together with the positional axis.
-        class namedint(int): ...  # pylint: disable=multiple-statements
+        cls = _make_named_int_class(axis)
+        return cls(named_axis[axis])
 
-        def _repr(self):
-            return f"{axis!r} (named axis) -> {super(namedint, self).__repr__()} (pos. axis)"
-
-        namedint.__repr__ = namedint.__str__ = _repr
-
-        return namedint(named_axis[axis])
-    if is_integer(axis) or axis is None:
-        return axis
+    if is_integer(axis):
+        # TODO: is_integer is an external  helper function that doesn't specify types
+        return int(tp.cast(tp.Any, axis))
+    elif axis is None:
+        return None
     else:
         raise ValueError(f"Invalid {axis=} [{type(axis)=}]")
 
@@ -777,9 +786,8 @@ def _normalize_named_slice(
                 idx = tp.cast(int, ax_name)
                 out_where[idx] = slice_
             elif _is_valid_named_axis(ax_name):
-                idx = _named_axis_to_positional_axis(named_axis, ax_name)
                 # it's an integer, pyright doesn't get this
-                idx = tp.cast(int, idx)
+                idx = tp.cast(int, _named_axis_to_positional_axis(named_axis, ax_name))
                 out_where[idx] = slice_
             else:
                 raise ValueError(f"Invalid axis name: {ax_name} in slice {where}")