From 61ad5104174ff5decdc3316abce6d7c2f60aeb1a Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 5 Nov 2018 17:07:43 -0800
Subject: [PATCH 01/12] BUG: fix and test offset comparison with non-offsets

---
 pandas/_libs/tslibs/offsets.pyx              |  7 +++--
 pandas/tests/tseries/offsets/test_offsets.py | 12 +++++++++
 pandas/tests/tseries/offsets/test_ticks.py   | 21 +++++++++++++++
 pandas/tseries/offsets.py                    | 27 +++++++++++++++-----
 4 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 78e1269aa5363..d739a60380805 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -306,8 +306,11 @@ class _BaseOffset(object):
 
     def __eq__(self, other):
         if is_string_object(other):
-            other = to_offset(other)
-
+            try:
+                other = to_offset(other)
+            except ValueError:
+                # e.g. "infer"
+                return False
         try:
             return self._params == other._params
         except AttributeError:
diff --git a/pandas/tests/tseries/offsets/test_offsets.py b/pandas/tests/tseries/offsets/test_offsets.py
index cbd3e0903b713..7c6f0b59192dc 100644
--- a/pandas/tests/tseries/offsets/test_offsets.py
+++ b/pandas/tests/tseries/offsets/test_offsets.py
@@ -187,6 +187,18 @@ def testMult2(self):
         assert self.d + (-5 * self._offset(-10)) == self.d + self._offset(50)
         assert self.d + (-3 * self._offset(-2)) == self.d + self._offset(6)
 
+    def test_compare_str(self):
+        # comparing to strings that cannot be cast to DateOffsets should
+        #  not raise for __eq__ or __ne__
+        if self._offset is None:
+            return
+        off = self._get_offset(self._offset)
+
+        assert not off == "infer"
+        assert off != "foo"
+        # Note: inequalities are only implemented for Tick subclasses;
+        #  tests for this are in test_ticks
+
 
 class TestCommon(Base):
     # exected value created by Base._get_offset
diff --git a/pandas/tests/tseries/offsets/test_ticks.py b/pandas/tests/tseries/offsets/test_ticks.py
index 369c0971f1e9a..d83266c2b2a92 100644
--- a/pandas/tests/tseries/offsets/test_ticks.py
+++ b/pandas/tests/tseries/offsets/test_ticks.py
@@ -267,3 +267,24 @@ def test_compare_ticks(cls):
     assert cls(4) > three
     assert cls(3) == cls(3)
     assert cls(3) != cls(4)
+
+
+@pytest.mark.parametrize('cls', tick_classes)
+def test_compare_ticks_to_strs(cls):
+    off = cls(19)
+
+    # These tests should work with any strings, but we particularly are
+    #  interested in "infer" as that comparison is convenient to make in
+    #  Datetime/Timedelta Array/Index constructors
+    assert not off == "infer"
+    assert not "foo" == off
+
+    for left, right in [("infer", off), (off, "infer")]:
+        with pytest.raises(TypeError):
+            left < right
+        with pytest.raises(TypeError):
+            left <= right
+        with pytest.raises(TypeError):
+            left > right
+        with pytest.raises(TypeError):
+            left >= right
diff --git a/pandas/tseries/offsets.py b/pandas/tseries/offsets.py
index 6fb562e301ac2..133b03dee375c 100644
--- a/pandas/tseries/offsets.py
+++ b/pandas/tseries/offsets.py
@@ -2199,9 +2199,18 @@ def apply_index(self, i):
 
 
 def _tick_comp(op):
+    assert op not in [operator.eq, operator.ne]
+
     def f(self, other):
-        return op(self.delta, other.delta)
+        try:
+            return op(self.delta, other.delta)
+        except AttributeError:
+            # comparing with a non-Tick object
+            raise TypeError("Invalid comparison between {cls} and {typ}"
+                            .format(cls=type(self).__name__,
+                                    typ=type(other).__name__))
 
+    f.__name__ = '__{opname}__'.format(opname=op.__name__)
     return f
 
 
@@ -2220,8 +2229,6 @@ def __init__(self, n=1, normalize=False):
     __ge__ = _tick_comp(operator.ge)
     __lt__ = _tick_comp(operator.lt)
     __le__ = _tick_comp(operator.le)
-    __eq__ = _tick_comp(operator.eq)
-    __ne__ = _tick_comp(operator.ne)
 
     def __add__(self, other):
         if isinstance(other, Tick):
@@ -2242,8 +2249,11 @@ def __add__(self, other):
     def __eq__(self, other):
         if isinstance(other, compat.string_types):
             from pandas.tseries.frequencies import to_offset
-
-            other = to_offset(other)
+            try:
+                other = to_offset(other)
+            except ValueError:
+                # e.g. "infer"
+                return False
 
         if isinstance(other, Tick):
             return self.delta == other.delta
@@ -2258,8 +2268,11 @@ def __hash__(self):
     def __ne__(self, other):
         if isinstance(other, compat.string_types):
             from pandas.tseries.frequencies import to_offset
-
-            other = to_offset(other)
+            try:
+                other = to_offset(other)
+            except ValueError:
+                # e.g. "infer"
+                return True
 
         if isinstance(other, Tick):
             return self.delta != other.delta

From 937541e2ed3be2284d743407f8e482009ebac5d8 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 5 Nov 2018 17:09:15 -0800
Subject: [PATCH 02/12] whatsnew note

---
 doc/source/whatsnew/v0.24.0.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index 6ace245a4bae1..f955e9fc0adf4 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1162,6 +1162,7 @@ Offsets
 - Bug in :class:`FY5253` where date offsets could incorrectly raise an ``AssertionError`` in arithmetic operatons (:issue:`14774`)
 - Bug in :class:`DateOffset` where keyword arguments ``week`` and ``milliseconds`` were accepted and ignored.  Passing these will now raise ``ValueError`` (:issue:`19398`)
 - Bug in adding :class:`DateOffset` with :class:`DataFrame` or :class:`PeriodIndex` incorrectly raising ``TypeError`` (:issue:`23215`)
+- Bug in comparing :class:`DateOffset` objects with non-DateOffset objects, particularly strings, raising ``ValueError`` instead of returning ``False`` for equality checks and ``True`` for not-equal checks (:issue:`????`)
 
 Numeric
 ^^^^^^^

From ca9e8af967817b7a922868ae7405d0eb6ed8fba2 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 5 Nov 2018 17:50:56 -0800
Subject: [PATCH 03/12] Fix and test casting tz-aware datetimeindex to
 object-dtype ndarray or Index

---
 doc/source/whatsnew/v0.24.0.txt          |  2 ++
 pandas/core/arrays/datetimes.py          | 10 ++++++++++
 pandas/core/indexes/base.py              | 10 +++++++---
 pandas/tests/arrays/test_datetimelike.py | 23 +++++++++++++++++++++++
 pandas/tests/indexes/test_base.py        | 12 ++++++++++--
 5 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index f955e9fc0adf4..8943bb1ce3a74 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1357,3 +1357,5 @@ Other
 - :meth:`~pandas.io.formats.style.Styler.bar` now also supports tablewise application (in addition to rowwise and columnwise) with ``axis=None`` and setting clipping range with ``vmin`` and ``vmax`` (:issue:`21548` and :issue:`21526`). ``NaN`` values are also handled properly.
 - Logical operations ``&, |, ^`` between :class:`Series` and :class:`Index` will no longer raise ``ValueError`` (:issue:`22092`)
 - Bug in :meth:`DataFrame.combine_first` in which column types were unexpectedly converted to float (:issue:`20699`)
+- Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`????`)
+- Bug in :class:`DatetimeIndex` where calling `np.array(dtindex, dtype=object)` would incorrectly return an array of ``long`` objects (:issue:`????`)
diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index 0258e1e6e5973..00ae2ccbdc0d2 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -374,6 +374,16 @@ def _resolution(self):
     # ----------------------------------------------------------------
     # Array-like Methods
 
+    def __array__(self, dtype=None):
+        if is_object_dtype(dtype):
+            return np.array(list(self), dtype=object)
+        elif dtype == 'i8':
+            return self.asi8
+
+        # TODO: warn that dtype is not used?
+        #  warn that conversion may be lossy?
+        return self._data.view(np.ndarray)  # follow Index.__array__
+
     def __iter__(self):
         """
         Return an iterator over the boxed values
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index ae64179b36485..fbdb25d67fac0 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -301,11 +301,15 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
               (dtype is not None and is_datetime64_any_dtype(dtype)) or
                 'tz' in kwargs):
             from pandas import DatetimeIndex
-            result = DatetimeIndex(data, copy=copy, name=name,
-                                   dtype=dtype, **kwargs)
+
             if dtype is not None and is_dtype_equal(_o_dtype, dtype):
-                return Index(result.to_pydatetime(), dtype=_o_dtype)
+                # if `data` is already a TZaware DatetimeIndex, then passing
+                #  dtype=object to the constructor will raise spuriously
+                result = DatetimeIndex(data, copy=copy, name=name, **kwargs)
+                return Index(list(result), dtype=_o_dtype)
             else:
+                result = DatetimeIndex(data, copy=copy, name=name,
+                                       dtype=dtype, **kwargs)
                 return result
 
         elif (is_timedelta64_dtype(data) or
diff --git a/pandas/tests/arrays/test_datetimelike.py b/pandas/tests/arrays/test_datetimelike.py
index 3fd03a351de7c..7caefda48b1fa 100644
--- a/pandas/tests/arrays/test_datetimelike.py
+++ b/pandas/tests/arrays/test_datetimelike.py
@@ -57,6 +57,29 @@ def timedelta_index(request):
 
 class TestDatetimeArray(object):
 
+    def test_array_object_dtype(self, tz_naive_fixture):
+        tz = tz_naive_fixture
+        dti = pd.date_range('2016-01-01', periods=3, tz=tz)
+        arr = DatetimeArrayMixin(dti)
+
+        expected = np.array(list(dti))
+
+        result = np.array(arr, dtype=object)
+        tm.assert_numpy_array_equal(result, expected)
+
+        # also test the DatetimeIndex method while we're at it
+        result = np.array(dti, dtype=object)
+        tm.assert_numpy_array_equal(result, expected)
+
+    def test_array(self, tz_naive_fixture):
+        tz = tz_naive_fixture
+        dti = pd.date_range('2016-01-01', periods=3, tz=tz)
+        arr = DatetimeArrayMixin(dti)
+
+        expected = dti.asi8.view('M8[ns]')
+        result = np.array(arr)
+        tm.assert_numpy_array_equal(result, expected)
+
     def test_from_dti(self, tz_naive_fixture):
         tz = tz_naive_fixture
         dti = pd.date_range('2016-01-01', periods=3, tz=tz)
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index daebc6e95aac4..592df07a74f49 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -132,7 +132,7 @@ def test_construction_list_tuples_nan(self, na_value, vtype):
     @pytest.mark.parametrize("cast_as_obj", [True, False])
     @pytest.mark.parametrize("index", [
         pd.date_range('2015-01-01 10:00', freq='D', periods=3,
-                      tz='US/Eastern'),  # DTI with tz
+                      tz='US/Eastern', name='Green Eggs & Ham'),  # DTI with tz
         pd.date_range('2015-01-01 10:00', freq='D', periods=3),  # DTI no tz
         pd.timedelta_range('1 days', freq='D', periods=3),  # td
         pd.period_range('2015-01-01', freq='D', periods=3)  # period
@@ -145,8 +145,16 @@ def test_constructor_from_index_dtlike(self, cast_as_obj, index):
 
         tm.assert_index_equal(result, index)
 
-        if isinstance(index, pd.DatetimeIndex) and hasattr(index, 'tz'):
+        if isinstance(index, pd.DatetimeIndex):
             assert result.tz == index.tz
+            if cast_as_obj:
+                # GH#???? check that Index(dti, dtype=object) does not
+                #  incorrectly raise ValueError, and that nanoseconds are not
+                #  dropped
+                index += pd.Timedelta(nanoseconds=50)
+                result = pd.Index(index, dtype=object)
+                assert result.dtype == np.object_
+                assert list(result) == list(index)
 
     @pytest.mark.parametrize("index,has_tz", [
         (pd.date_range('2015-01-01 10:00', freq='D', periods=3,

From 9d0fbd7ef4a123f141ef1fac98afa011ad9b56d3 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 5 Nov 2018 17:57:33 -0800
Subject: [PATCH 04/12] add GH references

---
 doc/source/whatsnew/v0.24.0.txt              | 6 +++---
 pandas/core/indexes/base.py                  | 4 ++--
 pandas/tests/arrays/test_datetimelike.py     | 2 ++
 pandas/tests/indexes/test_base.py            | 2 +-
 pandas/tests/tseries/offsets/test_offsets.py | 1 +
 pandas/tests/tseries/offsets/test_ticks.py   | 1 +
 6 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index 8943bb1ce3a74..3586a617a0f35 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1162,7 +1162,7 @@ Offsets
 - Bug in :class:`FY5253` where date offsets could incorrectly raise an ``AssertionError`` in arithmetic operatons (:issue:`14774`)
 - Bug in :class:`DateOffset` where keyword arguments ``week`` and ``milliseconds`` were accepted and ignored.  Passing these will now raise ``ValueError`` (:issue:`19398`)
 - Bug in adding :class:`DateOffset` with :class:`DataFrame` or :class:`PeriodIndex` incorrectly raising ``TypeError`` (:issue:`23215`)
-- Bug in comparing :class:`DateOffset` objects with non-DateOffset objects, particularly strings, raising ``ValueError`` instead of returning ``False`` for equality checks and ``True`` for not-equal checks (:issue:`????`)
+- Bug in comparing :class:`DateOffset` objects with non-DateOffset objects, particularly strings, raising ``ValueError`` instead of returning ``False`` for equality checks and ``True`` for not-equal checks (:issue:`23524`)
 
 Numeric
 ^^^^^^^
@@ -1357,5 +1357,5 @@ Other
 - :meth:`~pandas.io.formats.style.Styler.bar` now also supports tablewise application (in addition to rowwise and columnwise) with ``axis=None`` and setting clipping range with ``vmin`` and ``vmax`` (:issue:`21548` and :issue:`21526`). ``NaN`` values are also handled properly.
 - Logical operations ``&, |, ^`` between :class:`Series` and :class:`Index` will no longer raise ``ValueError`` (:issue:`22092`)
 - Bug in :meth:`DataFrame.combine_first` in which column types were unexpectedly converted to float (:issue:`20699`)
-- Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`????`)
-- Bug in :class:`DatetimeIndex` where calling `np.array(dtindex, dtype=object)` would incorrectly return an array of ``long`` objects (:issue:`????`)
+- Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`23524`)
+- Bug in :class:`DatetimeIndex` where calling `np.array(dtindex, dtype=object)` would incorrectly return an array of ``long`` objects (:issue:`23524`)
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index fbdb25d67fac0..73f699c89dc75 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -303,8 +303,8 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
             from pandas import DatetimeIndex
 
             if dtype is not None and is_dtype_equal(_o_dtype, dtype):
-                # if `data` is already a TZaware DatetimeIndex, then passing
-                #  dtype=object to the constructor will raise spuriously
+                # GH#23524 if `data` is already a TZaware DatetimeIndex,
+                #  then passing dtype=object to the constructor would raise
                 result = DatetimeIndex(data, copy=copy, name=name, **kwargs)
                 return Index(list(result), dtype=_o_dtype)
             else:
diff --git a/pandas/tests/arrays/test_datetimelike.py b/pandas/tests/arrays/test_datetimelike.py
index 7caefda48b1fa..377531c1c748d 100644
--- a/pandas/tests/arrays/test_datetimelike.py
+++ b/pandas/tests/arrays/test_datetimelike.py
@@ -58,6 +58,7 @@ def timedelta_index(request):
 class TestDatetimeArray(object):
 
     def test_array_object_dtype(self, tz_naive_fixture):
+        # GH#23524
         tz = tz_naive_fixture
         dti = pd.date_range('2016-01-01', periods=3, tz=tz)
         arr = DatetimeArrayMixin(dti)
@@ -72,6 +73,7 @@ def test_array_object_dtype(self, tz_naive_fixture):
         tm.assert_numpy_array_equal(result, expected)
 
     def test_array(self, tz_naive_fixture):
+        # GH#23524
         tz = tz_naive_fixture
         dti = pd.date_range('2016-01-01', periods=3, tz=tz)
         arr = DatetimeArrayMixin(dti)
diff --git a/pandas/tests/indexes/test_base.py b/pandas/tests/indexes/test_base.py
index 592df07a74f49..726db0cdee4fe 100644
--- a/pandas/tests/indexes/test_base.py
+++ b/pandas/tests/indexes/test_base.py
@@ -148,7 +148,7 @@ def test_constructor_from_index_dtlike(self, cast_as_obj, index):
         if isinstance(index, pd.DatetimeIndex):
             assert result.tz == index.tz
             if cast_as_obj:
-                # GH#???? check that Index(dti, dtype=object) does not
+                # GH#23524 check that Index(dti, dtype=object) does not
                 #  incorrectly raise ValueError, and that nanoseconds are not
                 #  dropped
                 index += pd.Timedelta(nanoseconds=50)
diff --git a/pandas/tests/tseries/offsets/test_offsets.py b/pandas/tests/tseries/offsets/test_offsets.py
index 7c6f0b59192dc..d68dd65c9841b 100644
--- a/pandas/tests/tseries/offsets/test_offsets.py
+++ b/pandas/tests/tseries/offsets/test_offsets.py
@@ -188,6 +188,7 @@ def testMult2(self):
         assert self.d + (-3 * self._offset(-2)) == self.d + self._offset(6)
 
     def test_compare_str(self):
+        # GH#23524
         # comparing to strings that cannot be cast to DateOffsets should
         #  not raise for __eq__ or __ne__
         if self._offset is None:
diff --git a/pandas/tests/tseries/offsets/test_ticks.py b/pandas/tests/tseries/offsets/test_ticks.py
index d83266c2b2a92..128010fe6d32c 100644
--- a/pandas/tests/tseries/offsets/test_ticks.py
+++ b/pandas/tests/tseries/offsets/test_ticks.py
@@ -271,6 +271,7 @@ def test_compare_ticks(cls):
 
 @pytest.mark.parametrize('cls', tick_classes)
 def test_compare_ticks_to_strs(cls):
+    # GH#23524
     off = cls(19)
 
     # These tests should work with any strings, but we particularly are

From dbf145f0ac3941d5d12ddef8a431151049100bef Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 5 Nov 2018 19:09:00 -0800
Subject: [PATCH 05/12] Clarify comment

---
 pandas/core/indexes/base.py | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 73f699c89dc75..b2a68770eb554 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -303,8 +303,10 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
             from pandas import DatetimeIndex
 
             if dtype is not None and is_dtype_equal(_o_dtype, dtype):
-                # GH#23524 if `data` is already a TZaware DatetimeIndex,
-                #  then passing dtype=object to the constructor would raise
+                # GH#23524 passing `dtype=object` to DatetimeIndex is invalid,
+                #  will raise in the where `data` is already tz-aware.  So
+                #  we leave it out of this step and cast to object-dtype after
+                #  the DatetimeIndex construction.
                 result = DatetimeIndex(data, copy=copy, name=name, **kwargs)
                 return Index(list(result), dtype=_o_dtype)
             else:

From 8853b6a43448945fce0e4a555c15087b1a635b48 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 6 Nov 2018 08:14:30 -0800
Subject: [PATCH 06/12] test for np.array(arr, dtype=np.int64)

---
 pandas/core/arrays/datetimes.py          |  3 ++-
 pandas/tests/arrays/test_datetimelike.py | 13 +++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index 0c9455388e9c5..e65d0744c4138 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -19,6 +19,7 @@
 from pandas.core.dtypes.common import (
     _NS_DTYPE,
     is_object_dtype,
+    is_int64_dtype,
     is_datetime64tz_dtype,
     is_datetime64_dtype,
     ensure_int64)
@@ -379,7 +380,7 @@ def _resolution(self):
     def __array__(self, dtype=None):
         if is_object_dtype(dtype):
             return np.array(list(self), dtype=object)
-        elif dtype == 'i8':
+        elif is_int64_dtype(dtype):
             return self.asi8
 
         # TODO: warn that dtype is not used?
diff --git a/pandas/tests/arrays/test_datetimelike.py b/pandas/tests/arrays/test_datetimelike.py
index 377531c1c748d..638f88f44f9ac 100644
--- a/pandas/tests/arrays/test_datetimelike.py
+++ b/pandas/tests/arrays/test_datetimelike.py
@@ -82,6 +82,19 @@ def test_array(self, tz_naive_fixture):
         result = np.array(arr)
         tm.assert_numpy_array_equal(result, expected)
 
+    def test_array_i8_dtype(self, tz_naive_fixture):
+        # GH#23524
+        tz = tz_naive_fixture
+        dti = pd.date_range('2016-01-01', periods=3, tz=tz)
+        arr = DatetimeArrayMixin(dti)
+
+        expected = dti.asi8
+        result = np.array(arr, dtype='i8')
+        tm.assert_numpy_array_equal(result, expected)
+
+        result = np.array(arr, dtype=np.int64)
+        tm.assert_numpy_array_equal(result, expected)
+
     def test_from_dti(self, tz_naive_fixture):
         tz = tz_naive_fixture
         dti = pd.date_range('2016-01-01', periods=3, tz=tz)

From 9add480c09be6edbe1ea1b1d4f5a9f02ffd324f0 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 6 Nov 2018 08:34:46 -0800
Subject: [PATCH 07/12] release note for fixing dropping of nanoseconds

---
 doc/source/whatsnew/v0.24.0.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index d6f482a904807..a7c16856fee71 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1367,3 +1367,4 @@ Other
 - Bug in :meth:`DataFrame.combine_first` in which column types were unexpectedly converted to float (:issue:`20699`)
 - Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`23524`)
 - Bug in :class:`DatetimeIndex` where calling `np.array(dtindex, dtype=object)` would incorrectly return an array of ``long`` objects (:issue:`23524`)
+- Bug in :class:`Index` where calling `np.array(dtindex, dtype=object)` on a timezone-naive :class:`DatetimeIndex` would return an array of ``datetime`` objects instead of :class:`Timestamp` objects, potentially losing nanosecond portions of the timestamps (:issue:`23524`)

From cfd8e717e90effbbd8d54f1ac125c0a0e843d17c Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 6 Nov 2018 17:01:54 -0800
Subject: [PATCH 08/12] test for copy=False being respected

---
 pandas/tests/arrays/test_datetimelike.py | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/pandas/tests/arrays/test_datetimelike.py b/pandas/tests/arrays/test_datetimelike.py
index 638f88f44f9ac..5ba99a48e34ad 100644
--- a/pandas/tests/arrays/test_datetimelike.py
+++ b/pandas/tests/arrays/test_datetimelike.py
@@ -82,6 +82,11 @@ def test_array(self, tz_naive_fixture):
         result = np.array(arr)
         tm.assert_numpy_array_equal(result, expected)
 
+        # check that we are not making copies when setting copy=False
+        result = np.array(arr, copy=False)
+        assert result.base is expected.base
+        assert result.base is not None
+
     def test_array_i8_dtype(self, tz_naive_fixture):
         # GH#23524
         tz = tz_naive_fixture
@@ -95,6 +100,11 @@ def test_array_i8_dtype(self, tz_naive_fixture):
         result = np.array(arr, dtype=np.int64)
         tm.assert_numpy_array_equal(result, expected)
 
+        # check that we are not making copies when setting copy=False
+        result = np.array(arr, dtype='i8', copy=False)
+        assert result.base is expected.base
+        assert result.base is not None
+
     def test_from_dti(self, tz_naive_fixture):
         tz = tz_naive_fixture
         dti = pd.date_range('2016-01-01', periods=3, tz=tz)

From b4ecfbb1d3180acc223a8bb1e0553ec0579e378e Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 7 Nov 2018 08:02:13 -0800
Subject: [PATCH 09/12] fix missing backticks

---
 doc/source/whatsnew/v0.24.0.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index 497d13d4c098d..1d026eb2c4f00 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1372,5 +1372,5 @@ Other
 - Logical operations ``&, |, ^`` between :class:`Series` and :class:`Index` will no longer raise ``ValueError`` (:issue:`22092`)
 - Bug in :meth:`DataFrame.combine_first` in which column types were unexpectedly converted to float (:issue:`20699`)
 - Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`23524`)
-- Bug in :class:`DatetimeIndex` where calling `np.array(dtindex, dtype=object)` would incorrectly return an array of ``long`` objects (:issue:`23524`)
-- Bug in :class:`Index` where calling `np.array(dtindex, dtype=object)` on a timezone-naive :class:`DatetimeIndex` would return an array of ``datetime`` objects instead of :class:`Timestamp` objects, potentially losing nanosecond portions of the timestamps (:issue:`23524`)
+- Bug in :class:`DatetimeIndex` where calling ``np.array(dtindex, dtype=object)`` would incorrectly return an array of ``long`` objects (:issue:`23524`)
+- Bug in :class:`Index` where calling ``np.array(dtindex, dtype=object)`` on a timezone-naive :class:`DatetimeIndex` would return an array of ``datetime`` objects instead of :class:`Timestamp` objects, potentially losing nanosecond portions of the timestamps (:issue:`23524`)

From 756574f46d5ee2c573df8d28ac1540f49bfb18d8 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 7 Nov 2018 08:05:45 -0800
Subject: [PATCH 10/12] comments

---
 pandas/_libs/tslibs/offsets.pyx | 2 ++
 pandas/tseries/offsets.py       | 4 ++++
 2 files changed, 6 insertions(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 34e4faa5fd274..74442708a0f42 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -307,6 +307,8 @@ class _BaseOffset(object):
     def __eq__(self, other):
         if is_string_object(other):
             try:
+                # GH#23524 if to_offset fails, we are dealing with an
+                #  incomparable type so == is False and != is True
                 other = to_offset(other)
             except ValueError:
                 # e.g. "infer"
diff --git a/pandas/tseries/offsets.py b/pandas/tseries/offsets.py
index 133b03dee375c..83bd7aeb6ee19 100644
--- a/pandas/tseries/offsets.py
+++ b/pandas/tseries/offsets.py
@@ -2250,6 +2250,8 @@ def __eq__(self, other):
         if isinstance(other, compat.string_types):
             from pandas.tseries.frequencies import to_offset
             try:
+                # GH#23524 if to_offset fails, we are dealing with an
+                #  incomparable type so == is False and != is True
                 other = to_offset(other)
             except ValueError:
                 # e.g. "infer"
@@ -2269,6 +2271,8 @@ def __ne__(self, other):
         if isinstance(other, compat.string_types):
             from pandas.tseries.frequencies import to_offset
             try:
+                # GH#23524 if to_offset fails, we are dealing with an
+                #  incomparable type so == is False and != is True
                 other = to_offset(other)
             except ValueError:
                 # e.g. "infer"

From bf1677addae30c468ab316291fc7637b8273c83a Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Thu, 8 Nov 2018 06:56:29 -0800
Subject: [PATCH 11/12] move whatsnew note, do astype differently

---
 doc/source/whatsnew/v0.24.0.txt | 6 +++---
 pandas/core/indexes/base.py     | 6 ++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
index a2ed86afa2ffa..7d831092f1549 100644
--- a/doc/source/whatsnew/v0.24.0.txt
+++ b/doc/source/whatsnew/v0.24.0.txt
@@ -1124,6 +1124,9 @@ Datetimelike
 - Bug in :class:`PeriodIndex` with attribute ``freq.n`` greater than 1 where adding a :class:`DateOffset` object would return incorrect results (:issue:`23215`)
 - Bug in :class:`Series` that interpreted string indices as lists of characters when setting datetimelike values (:issue:`23451`)
 - Bug in :class:`Timestamp` constructor which would drop the frequency of an input :class:`Timestamp` (:issue:`22311`)
+- Bug in :class:`DatetimeIndex` where calling ``np.array(dtindex, dtype=object)`` would incorrectly return an array of ``long`` objects (:issue:`23524`)
+- Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`23524`)
+- Bug in :class:`Index` where calling ``np.array(dtindex, dtype=object)`` on a timezone-naive :class:`DatetimeIndex` would return an array of ``datetime`` objects instead of :class:`Timestamp` objects, potentially losing nanosecond portions of the timestamps (:issue:`23524`)
 
 Timedelta
 ^^^^^^^^^
@@ -1373,6 +1376,3 @@ Other
 - :meth:`~pandas.io.formats.style.Styler.bar` now also supports tablewise application (in addition to rowwise and columnwise) with ``axis=None`` and setting clipping range with ``vmin`` and ``vmax`` (:issue:`21548` and :issue:`21526`). ``NaN`` values are also handled properly.
 - Logical operations ``&, |, ^`` between :class:`Series` and :class:`Index` will no longer raise ``ValueError`` (:issue:`22092`)
 - Bug in :meth:`DataFrame.combine_first` in which column types were unexpectedly converted to float (:issue:`20699`)
-- Bug in :class:`Index` where passing a timezone-aware :class:`DatetimeIndex` and `dtype=object` would incorrectly raise a ``ValueError`` (:issue:`23524`)
-- Bug in :class:`DatetimeIndex` where calling ``np.array(dtindex, dtype=object)`` would incorrectly return an array of ``long`` objects (:issue:`23524`)
-- Bug in :class:`Index` where calling ``np.array(dtindex, dtype=object)`` on a timezone-naive :class:`DatetimeIndex` would return an array of ``datetime`` objects instead of :class:`Timestamp` objects, potentially losing nanosecond portions of the timestamps (:issue:`23524`)
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 57d260ec553c4..60d38b766ee4c 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -307,8 +307,10 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
                 #  will raise in the where `data` is already tz-aware.  So
                 #  we leave it out of this step and cast to object-dtype after
                 #  the DatetimeIndex construction.
-                result = DatetimeIndex(data, copy=copy, name=name, **kwargs)
-                return Index(list(result), dtype=_o_dtype)
+                # Note we can pass copy=False because the .astype below
+                #  will always make a copy
+                result = DatetimeIndex(data, copy=False, name=name, **kwargs)
+                return result.astype(object)
             else:
                 result = DatetimeIndex(data, copy=copy, name=name,
                                        dtype=dtype, **kwargs)

From 0a5dbed0f27f7610211881862844b622c70ff631 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 9 Nov 2018 06:01:46 -0800
Subject: [PATCH 12/12] remove comment

---
 pandas/core/arrays/datetimes.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/core/arrays/datetimes.py b/pandas/core/arrays/datetimes.py
index e65d0744c4138..3a2c21b4ddf95 100644
--- a/pandas/core/arrays/datetimes.py
+++ b/pandas/core/arrays/datetimes.py
@@ -383,8 +383,7 @@ def __array__(self, dtype=None):
         elif is_int64_dtype(dtype):
             return self.asi8
 
-        # TODO: warn that dtype is not used?
-        #  warn that conversion may be lossy?
+        # TODO: warn that conversion may be lossy?
         return self._data.view(np.ndarray)  # follow Index.__array__
 
     def __iter__(self):