Check whether _simple_new always receives an ndarray

Author: reidy-p

pandas/core/indexes/base.py

@@ -506,6 +506,9 @@ def _shallow_copy(self, values=None, **kwargs):
         attributes.update(kwargs)
         if not len(values) and 'dtype' not in kwargs:
             attributes['dtype'] = self.dtype
+        from pandas import DatetimeIndex
+        if isinstance(values, DatetimeIndex):
+            values = values.values
         return self._simple_new(values, **attributes)
 
     def _shallow_copy_with_infer(self, values=None, **kwargs):

pandas/core/indexes/datetimes.py

@@ -525,6 +525,7 @@ def _generate(cls, start, end, periods, name, freq,
                                           freq=freq, name=name)
             else:
                 index = _generate_regular_range(start, end, periods, freq)
+
         else:
 
             if tz is not None:
@@ -548,6 +549,7 @@ def _generate(cls, start, end, periods, name, freq,
                                               freq=freq, name=name)
                 else:
                     index = _generate_regular_range(start, end, periods, freq)
+
                 if tz is not None and getattr(index, 'tz', None) is None:
                     arr = conversion.tz_localize_to_utc(_ensure_int64(index),
                                                         tz,
@@ -608,6 +610,8 @@ def _simple_new(cls, values, name=None, freq=None, tz=None,
                            dtype=dtype, **kwargs)
             values = np.array(values, copy=False)
 
+        assert isinstance(values, np.ndarray)
+
         if is_object_dtype(values):
             return cls(values, name=name, freq=freq, tz=tz,
                        dtype=dtype, **kwargs).values
@@ -1002,7 +1006,7 @@ def unique(self, level=None):
         else:
             naive = self
         result = super(DatetimeIndex, naive).unique(level=level)
-        return self._simple_new(result, name=self.name, tz=self.tz,
+        return self._simple_new(result.values, name=self.name, tz=self.tz,
                                 freq=self.freq)
 
     def union(self, other):

pandas/tests/indexes/test_base.py

@@ -329,7 +329,7 @@ def test_index_ctor_infer_periodindex(self):
     ])
     def test_constructor_simple_new(self, vals, dtype):
         index = Index(vals, name=dtype)
-        result = index._simple_new(index, dtype)
+        result = index._simple_new(index.values, dtype)
         tm.assert_index_equal(result, index)
 
     @pytest.mark.parametrize("vals", [