BUG: better exception on invalid slicing on CategoricalIndex (#40364)

Author: jbrockmendel

pandas/core/indexes/category.py

@@ -542,13 +542,6 @@ def _convert_list_indexer(self, keyarr):
 
         return self.get_indexer_for(keyarr)
 
-    @doc(Index._maybe_cast_slice_bound)
-    def _maybe_cast_slice_bound(self, label, side: str, kind):
-        if kind == "loc":
-            return label
-
-        return super()._maybe_cast_slice_bound(label, side, kind)
-
     # --------------------------------------------------------------------
 
     def _is_comparable_dtype(self, dtype: DtypeObj) -> bool:

pandas/tests/indexing/test_categorical.py

@@ -469,7 +469,11 @@ def test_ix_categorical_index_non_unique(self):
 
     def test_loc_slice(self):
         # GH9748
-        with pytest.raises(KeyError, match="1"):
+        msg = (
+            "cannot do slice indexing on CategoricalIndex with these "
+            r"indexers \[1\] of type int"
+        )
+        with pytest.raises(TypeError, match=msg):
             self.df.loc[1:5]
 
         result = self.df.loc["b":"c"]