Minor corrections to previous submit (#16820)

doc/source/whatsnew/v0.20.3.txt

@@ -42,7 +42,7 @@ Bug Fixes
 - Fixed compat with loading a ``DataFrame`` with a ``PeriodIndex``, from a ``format='fixed'`` HDFStore, in Python 3, that was written in Python 2 (:issue:`16781`)
 - Fixed a bug in failing to compute rolling computations of a column-MultiIndexed ``DataFrame`` (:issue:`16789`, :issue:`16825`)
 - Bug in a DataFrame/Series with a ``TimedeltaIndex`` when slice indexing (:issue:`16637`)
-- Handle reindexing an empty categorical index rather than throwing (:issue:`16770`)
+- Bug in reindexing on an empty ``CategoricalIndex`` (:issue:`16770`)
 
 
 Conversion

pandas/core/indexes/category.py

@@ -420,7 +420,7 @@ def reindex(self, target, method=None, level=None, limit=None,
 
         indexer, missing = self.get_indexer_non_unique(np.array(target))
 
-        if len(self.codes):
+        if len(indexer):
             new_target = self.take(indexer)
         else:
             new_target = target
@@ -434,8 +434,6 @@ def reindex(self, target, method=None, level=None, limit=None,
                 result = Index(np.array(self), name=self.name)
                 new_target, indexer, _ = result._reindex_non_unique(
                     np.array(target))
-                # see GH 16819, indexer needs to be converted to correct type
-                indexer = np.array(indexer, dtype=np.int64)
             else:
 
                 codes = new_target.codes.copy()

pandas/tests/indexes/test_category.py

@@ -425,7 +425,7 @@ def test_reindex_empty_index(self):
         res, indexer = c.reindex(['a', 'b'])
         tm.assert_index_equal(res, Index(['a', 'b']), exact=True)
         tm.assert_numpy_array_equal(indexer,
-                                    np.array([-1, -1], dtype=np.int64))
+                                    np.array([-1, -1], dtype=np.intp))
 
     def test_duplicates(self):