BUG: Tick + np.timedelta64 (#44474)

doc/source/whatsnew/v1.4.0.rst

@@ -540,7 +540,7 @@ Datetimelike
 - Bug in inplace addition and subtraction of :class:`DatetimeIndex` or :class:`TimedeltaIndex` with :class:`DatetimeArray` or :class:`TimedeltaArray` (:issue:`43904`)
 - Bug in in calling ``np.isnan``, ``np.isfinite``, or ``np.isinf`` on a timezone-aware :class:`DatetimeIndex` incorrectly raising ``TypeError`` (:issue:`43917`)
 - Bug in constructing a :class:`Series` from datetime-like strings with mixed timezones incorrectly partially-inferring datetime values (:issue:`40111`)
--
+- Bug in addition with a :class:`Tick` object and a ``np.timedelta64`` object incorrectly raising instead of returning :class:`Timedelta` (:issue:`44474`)
 
 Timedelta
 ^^^^^^^^^

pandas/_libs/tslibs/offsets.pyx

@@ -72,7 +72,10 @@ from pandas._libs.tslibs.np_datetime cimport (
 from pandas._libs.tslibs.tzconversion cimport tz_convert_from_utc_single
 
 from .dtypes cimport PeriodDtypeCode
-from .timedeltas cimport delta_to_nanoseconds
+from .timedeltas cimport (
+    delta_to_nanoseconds,
+    is_any_td_scalar,
+)
 
 from .timedeltas import Timedelta
 
@@ -154,7 +157,11 @@ def apply_wraps(func):
 
         if other is NaT:
             return NaT
-        elif isinstance(other, BaseOffset) or PyDelta_Check(other):
+        elif (
+            isinstance(other, BaseOffset)
+            or PyDelta_Check(other)
+            or util.is_timedelta64_object(other)
+        ):
             # timedelta path
             return func(self, other)
         elif is_datetime64_object(other) or PyDate_Check(other):
@@ -902,7 +909,7 @@ cdef class Tick(SingleConstructorOffset):
             # PyDate_Check includes date, datetime
             return Timestamp(other) + self
 
-        if PyDelta_Check(other):
+        if util.is_timedelta64_object(other) or PyDelta_Check(other):
             return other + self.delta
         elif isinstance(other, type(self)):
             # TODO: this is reached in tests that specifically call apply,
@@ -1396,9 +1403,10 @@ cdef class BusinessDay(BusinessMixin):
                 result = result + self.offset
             return result
 
-        elif PyDelta_Check(other) or isinstance(other, Tick):
+        elif is_any_td_scalar(other):
+            td = Timedelta(self.offset) + other
             return BusinessDay(
-                self.n, offset=self.offset + other, normalize=self.normalize
+                self.n, offset=td.to_pytimedelta(), normalize=self.normalize
             )
         else:
             raise ApplyTypeError(
@@ -3265,8 +3273,9 @@ cdef class CustomBusinessDay(BusinessDay):
                 result = result + self.offset
             return result
 
-        elif PyDelta_Check(other) or isinstance(other, Tick):
-            return BDay(self.n, offset=self.offset + other, normalize=self.normalize)
+        elif is_any_td_scalar(other):
+            td = Timedelta(self.offset) + other
+            return BDay(self.n, offset=td.to_pytimedelta(), normalize=self.normalize)
         else:
             raise ApplyTypeError(
                 "Only know how to combine trading day with "

pandas/tests/tseries/offsets/test_business_day.py

@@ -7,6 +7,7 @@
     timedelta,
 )
 
+import numpy as np
 import pytest
 
 from pandas._libs.tslibs.offsets import (
@@ -17,6 +18,7 @@
 
 from pandas import (
     DatetimeIndex,
+    Timedelta,
     _testing as tm,
 )
 from pandas.tests.tseries.offsets.common import (
@@ -57,11 +59,30 @@ def test_with_offset(self):
 
         assert (self.d + offset) == datetime(2008, 1, 2, 2)
 
-    def test_with_offset_index(self):
-        dti = DatetimeIndex([self.d])
-        result = dti + (self.offset + timedelta(hours=2))
+    @pytest.mark.parametrize("reverse", [True, False])
+    @pytest.mark.parametrize(
+        "td",
+        [
+            Timedelta(hours=2),
+            Timedelta(hours=2).to_pytimedelta(),
+            Timedelta(hours=2).to_timedelta64(),
+        ],
+        ids=lambda x: type(x),
+    )
+    def test_with_offset_index(self, reverse, td, request):
+        if reverse and isinstance(td, np.timedelta64):
+            mark = pytest.mark.xfail(
+                reason="need __array_priority__, but that causes other errors"
+            )
+            request.node.add_marker(mark)
 
+        dti = DatetimeIndex([self.d])
         expected = DatetimeIndex([datetime(2008, 1, 2, 2)])
+
+        if reverse:
+            result = dti + (td + self.offset)
+        else:
+            result = dti + (self.offset + td)
         tm.assert_index_equal(result, expected)
 
     def test_eq(self):

pandas/tests/tseries/offsets/test_custom_business_day.py

@@ -19,6 +19,7 @@
 
 from pandas import (
     DatetimeIndex,
+    Timedelta,
     _testing as tm,
     read_pickle,
 )
@@ -62,11 +63,30 @@ def test_with_offset(self):
 
         assert (self.d + offset) == datetime(2008, 1, 2, 2)
 
-    def test_with_offset_index(self):
-        dti = DatetimeIndex([self.d])
-        result = dti + (self.offset + timedelta(hours=2))
+    @pytest.mark.parametrize("reverse", [True, False])
+    @pytest.mark.parametrize(
+        "td",
+        [
+            Timedelta(hours=2),
+            Timedelta(hours=2).to_pytimedelta(),
+            Timedelta(hours=2).to_timedelta64(),
+        ],
+        ids=lambda x: type(x),
+    )
+    def test_with_offset_index(self, reverse, td, request):
+        if reverse and isinstance(td, np.timedelta64):
+            mark = pytest.mark.xfail(
+                reason="need __array_priority__, but that causes other errors"
+            )
+            request.node.add_marker(mark)
 
+        dti = DatetimeIndex([self.d])
         expected = DatetimeIndex([datetime(2008, 1, 2, 2)])
+
+        if reverse:
+            result = dti + (td + self.offset)
+        else:
+            result = dti + (self.offset + td)
         tm.assert_index_equal(result, expected)
 
     def test_eq(self):

pandas/tests/tseries/offsets/test_ticks.py

@@ -230,9 +230,16 @@ def test_Nanosecond():
 )
 def test_tick_addition(kls, expected):
     offset = kls(3)
-    result = offset + Timedelta(hours=2)
-    assert isinstance(result, Timedelta)
-    assert result == expected
+    td = Timedelta(hours=2)
+
+    for other in [td, td.to_pytimedelta(), td.to_timedelta64()]:
+        result = offset + other
+        assert isinstance(result, Timedelta)
+        assert result == expected
+
+        result = other + offset
+        assert isinstance(result, Timedelta)
+        assert result == expected
 
 
 @pytest.mark.parametrize("cls", tick_classes)