From 1f7a03bb4476d79087c04a9b159b60c6a311dbdf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Tue, 9 Aug 2022 12:38:19 -0400
Subject: [PATCH 01/10] TYP: avoid inherit_names for DatetimeIndexOpsMixin

---
 pandas/core/arrays/datetimelike.py  | 32 ++++++++++-----
 pandas/core/arrays/timedeltas.py    |  7 +++-
 pandas/core/indexes/datetimelike.py | 63 ++++++++++++++++++++++-------
 pandas/core/indexes/datetimes.py    |  1 -
 pandas/core/indexes/period.py       |  6 +--
 5 files changed, 80 insertions(+), 29 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 2c070499308a7..8f274afe82177 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -552,7 +552,12 @@ def _concat_same_type(
 
             if obj.freq is not None and all(x.freq == obj.freq for x in to_concat):
                 pairs = zip(to_concat[:-1], to_concat[1:])
-                if all(pair[0][-1] + obj.freq == pair[1][0] for pair in pairs):
+                # error: No overload variant of "__radd__" of "BaseOffset" matches
+                # argument type "NaTType"
+                if all(
+                    pair[0][-1] + obj.freq == pair[1][0]  # type: ignore[operator]
+                    for pair in pairs
+                ):
                     new_freq = obj.freq
 
         new_obj._freq = new_freq
@@ -925,7 +930,7 @@ def _maybe_mask_results(
     # Frequency Properties/Methods
 
     @property
-    def freq(self):
+    def freq(self) -> BaseOffset | None:
         """
         Return the frequency object if it is set, otherwise None.
         """
@@ -1219,7 +1224,10 @@ def _sub_period(self, other: Period) -> npt.NDArray[np.object_]:
         new_i8_data = checked_add_with_arr(
             self.asi8, -other.ordinal, arr_mask=self._isnan
         )
-        new_data = np.array([self.freq.base * x for x in new_i8_data])
+        # error: Item "None" of "Optional[BaseOffset]" has no attribute "base"
+        new_data = np.array(
+            [self.freq.base * x for x in new_i8_data]  # type: ignore[union-attr]
+        )
 
         if self._hasna:
             new_data[self._isnan] = NaT
@@ -1417,8 +1425,10 @@ def _time_shift(
         if self.freq is None:
             raise NullFrequencyError("Cannot shift with no freq")
 
-        start = self[0] + periods * self.freq
-        end = self[-1] + periods * self.freq
+        # error: No overload variant of "__radd__" of "BaseOffset" matches
+        # argument type "NaTType"
+        start = self[0] + periods * self.freq  # type: ignore[operator]
+        end = self[-1] + periods * self.freq  # type: ignore[operator]
 
         # Note: in the DatetimeTZ case, _generate_range will infer the
         #  appropriate timezone from `start` and `end`, so tz does not need
@@ -1446,8 +1456,9 @@ def __add__(self, other):
             # as is_integer returns True for these
             if not is_period_dtype(self.dtype):
                 raise integer_op_not_supported(self)
+            # error: Item "None" of "Optional[BaseOffset]" has no attribute "n"
             result = cast("PeriodArray", self)._addsub_int_array_or_scalar(
-                other * self.freq.n, operator.add
+                other * self.freq.n, operator.add  # type: ignore[union-attr]
             )
 
         # array-like others
@@ -1463,8 +1474,9 @@ def __add__(self, other):
         elif is_integer_dtype(other_dtype):
             if not is_period_dtype(self.dtype):
                 raise integer_op_not_supported(self)
+            # error: Item "None" of "Optional[BaseOffset]" has no attribute "n"
             result = cast("PeriodArray", self)._addsub_int_array_or_scalar(
-                other * self.freq.n, operator.add
+                other * self.freq.n, operator.add  # type: ignore[union-attr]
             )
         else:
             # Includes Categorical, other ExtensionArrays
@@ -1504,8 +1516,9 @@ def __sub__(self, other):
             # as is_integer returns True for these
             if not is_period_dtype(self.dtype):
                 raise integer_op_not_supported(self)
+            # error: Item "None" of "Optional[BaseOffset]" has no attribute "n"
             result = cast("PeriodArray", self)._addsub_int_array_or_scalar(
-                other * self.freq.n, operator.sub
+                other * self.freq.n, operator.sub  # type: ignore[union-attr]
             )
 
         elif isinstance(other, Period):
@@ -1527,8 +1540,9 @@ def __sub__(self, other):
         elif is_integer_dtype(other_dtype):
             if not is_period_dtype(self.dtype):
                 raise integer_op_not_supported(self)
+            # error: Item "None" of "Optional[BaseOffset]" has no attribute "n"
             result = cast("PeriodArray", self)._addsub_int_array_or_scalar(
-                other * self.freq.n, operator.sub
+                other * self.freq.n, operator.sub  # type: ignore[union-attr]
             )
         else:
             # Includes ExtensionArrays, float_dtype
diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index 4011f29855949..d5174976a2e98 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -446,7 +446,8 @@ def __truediv__(self, other):
             freq = None
             if self.freq is not None:
                 # Tick division is not implemented, so operate on Timedelta
-                freq = self.freq.delta / other
+                # error: "BaseOffset" has no attribute "delta"
+                freq = self.freq.delta / other  # type: ignore[attr-defined]
                 freq = to_offset(freq)
             return type(self)._simple_new(result, dtype=result.dtype, freq=freq)
 
@@ -926,7 +927,9 @@ def sequence_to_td64ns(
     data = np.array(data, copy=copy)
 
     assert data.dtype == "m8[ns]", data
-    return data, inferred_freq
+    # error: Incompatible return value type (got "Tuple[Any, Optional[BaseOffset]]",
+    # expected "Tuple[ndarray[Any, Any], Optional[Tick]]")
+    return data, inferred_freq  # type: ignore[return-value]
 
 
 def ints_to_td64ns(data, unit="ns"):
diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 84955d5137383..382abc888474c 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -30,6 +30,7 @@
     parsing,
     to_offset,
 )
+from pandas._typing import npt
 from pandas.compat.numpy import function as nv
 from pandas.util._decorators import (
     Appender,
@@ -59,10 +60,7 @@
     Index,
     _index_shared_docs,
 )
-from pandas.core.indexes.extension import (
-    NDArrayBackedExtensionIndex,
-    inherit_names,
-)
+from pandas.core.indexes.extension import NDArrayBackedExtensionIndex
 from pandas.core.indexes.range import RangeIndex
 from pandas.core.tools.timedeltas import to_timedelta
 
@@ -75,12 +73,6 @@
 _TDT = TypeVar("_TDT", bound="DatetimeTimedeltaMixin")
 
 
-@inherit_names(
-    ["inferred_freq", "_resolution_obj", "resolution"],
-    DatetimeLikeArrayMixin,
-    cache=True,
-)
-@inherit_names(["mean", "asi8", "freq", "freqstr"], DatetimeLikeArrayMixin)
 class DatetimeIndexOpsMixin(NDArrayBackedExtensionIndex):
     """
     Common ops mixin to support a unified interface datetimelike Index.
@@ -89,9 +81,51 @@ class DatetimeIndexOpsMixin(NDArrayBackedExtensionIndex):
     _is_numeric_dtype = False
     _can_hold_strings = False
     _data: DatetimeArray | TimedeltaArray | PeriodArray
-    freq: BaseOffset | None
-    freqstr: str | None
-    _resolution_obj: Resolution
+
+    # ------------------------------------------------------------------------
+
+    @doc(DatetimeLikeArrayMixin.mean)
+    def mean(self, *, skipna: bool = True, axis: int | None = 0):
+        return self._data.mean(skipna=skipna, axis=axis)
+
+    # error: Decorated property not supported
+    @property  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.asi8)
+    def asi8(self) -> npt.NDArray[np.int64]:
+        return self._data.asi8
+
+    # error: Decorated property not supported
+    @property  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.freq)
+    def freq(self) -> BaseOffset | None:
+        return self._data.freq
+
+    @freq.setter
+    def freq(self, value) -> None:
+        # error: Property "freq" defined in "PeriodArray" is read-only
+        self._data.freq = value  # type: ignore[misc]
+
+    # error: Decorated property not supported
+    @property  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.freqstr)
+    def freqstr(self) -> str | None:
+        return self._data.freqstr
+
+    # error: Decorated property not supported
+    @cache_readonly  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.inferred_freq)
+    def inferred_freq(self) -> str | None:
+        return self._data.inferred_freq
+
+    @cache_readonly
+    def _resolution_obj(self) -> Resolution | None:
+        return self._data._resolution_obj
+
+    # error: Decorated property not supported
+    @cache_readonly  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.resolution)
+    def resolution(self) -> str:
+        return self._data.resolution
 
     # ------------------------------------------------------------------------
 
@@ -215,7 +249,8 @@ def _summary(self, name=None) -> str:
     def _can_partial_date_slice(self, reso: Resolution) -> bool:
         # e.g. test_getitem_setitem_periodindex
         # History of conversation GH#3452, GH#3931, GH#2369, GH#14826
-        return reso > self._resolution_obj
+        # error: Unsupported left operand type for > ("Resolution")
+        return reso > self._resolution_obj  # type: ignore[operator]
         # NB: for DTI/PI, not TDI
 
     def _parsed_string_to_bounds(self, reso: Resolution, parsed):
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index 2625d8c683a0c..edadea182334a 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -261,7 +261,6 @@ def _engine_type(self) -> type[libindex.DatetimeEngine]:
         return libindex.DatetimeEngine
 
     _data: DatetimeArray
-    inferred_freq: str | None
     tz: tzinfo | None
 
     # --------------------------------------------------------------------
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index fedcba7aa9644..469a01f46c947 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -167,8 +167,7 @@ def _engine_type(self) -> type[libindex.PeriodEngine]:
         return libindex.PeriodEngine
 
     @cache_readonly
-    # Signature of "_resolution_obj" incompatible with supertype "DatetimeIndexOpsMixin"
-    def _resolution_obj(self) -> Resolution:  # type: ignore[override]
+    def _resolution_obj(self) -> Resolution:
         # for compat with DatetimeIndex
         return self.dtype._resolution_obj
 
@@ -393,7 +392,8 @@ def is_full(self) -> bool:
         if not self.is_monotonic_increasing:
             raise ValueError("Index is not monotonic")
         values = self.asi8
-        return ((values[1:] - values[:-1]) < 2).all()
+        # error: Incompatible return value type (got "bool_", expected "bool")
+        return ((values[1:] - values[:-1]) < 2).all()  # type: ignore[return-value]
 
     @property
     def inferred_type(self) -> str:

From dafc87deec1642b2de02b1320c1774e1d8dcd1fe Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Fri, 12 Aug 2022 12:12:13 -0400
Subject: [PATCH 02/10] address some of the comments

---
 pandas/core/arrays/timedeltas.py | 26 ++++++++++++++++++++------
 pandas/core/indexes/period.py    |  3 +--
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index d5174976a2e98..49cc91d1f3ea1 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -36,6 +36,7 @@
     npt,
 )
 from pandas.compat.numpy import function as nv
+from pandas.util._decorators import doc
 from pandas.util._validators import validate_endpoints
 
 from pandas.core.dtypes.astype import astype_td64_unit_conversion
@@ -143,6 +144,23 @@ def _box_func(self, x: np.timedelta64) -> Timedelta | NaTType:
             return NaT
         return Timedelta._from_value_and_reso(y, reso=self._reso)
 
+    # error: Decorated property not supported
+    @property  # type: ignore[misc]
+    @doc(dtl.DatetimeLikeArrayMixin.freq)
+    def freq(self) -> Tick:
+        # error: Incompatible return value type (got "Optional[BaseOffset]",
+        # expected "Tick")
+        return self._freq  # type: ignore[return-value]
+
+    @freq.setter
+    def freq(self, value) -> None:
+        # python doesn't support super().freq = value (any mypy has some
+        # issue with the workaround)
+        # error: overloaded function has no attribute "fset"
+        super(TimedeltaArray, TimedeltaArray).freq.fset(  # type: ignore[attr-defined]
+            self, value
+        )
+
     @property
     # error: Return type "dtype" of "dtype" incompatible with return type
     # "ExtensionDtype" in supertype "ExtensionArray"
@@ -445,9 +463,7 @@ def __truediv__(self, other):
             result = self._ndarray / other
             freq = None
             if self.freq is not None:
-                # Tick division is not implemented, so operate on Timedelta
-                # error: "BaseOffset" has no attribute "delta"
-                freq = self.freq.delta / other  # type: ignore[attr-defined]
+                freq = self.freq.delta / other
                 freq = to_offset(freq)
             return type(self)._simple_new(result, dtype=result.dtype, freq=freq)
 
@@ -927,9 +943,7 @@ def sequence_to_td64ns(
     data = np.array(data, copy=copy)
 
     assert data.dtype == "m8[ns]", data
-    # error: Incompatible return value type (got "Tuple[Any, Optional[BaseOffset]]",
-    # expected "Tuple[ndarray[Any, Any], Optional[Tick]]")
-    return data, inferred_freq  # type: ignore[return-value]
+    return data, inferred_freq
 
 
 def ints_to_td64ns(data, unit="ns"):
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 469a01f46c947..e2741aa185051 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -392,8 +392,7 @@ def is_full(self) -> bool:
         if not self.is_monotonic_increasing:
             raise ValueError("Index is not monotonic")
         values = self.asi8
-        # error: Incompatible return value type (got "bool_", expected "bool")
-        return ((values[1:] - values[:-1]) < 2).all()  # type: ignore[return-value]
+        return ((values[1:] - values[:-1]) < 2).all().item()
 
     @property
     def inferred_type(self) -> str:

From d3a443074d7318518303a10afdade5ce8005c2c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Sat, 13 Aug 2022 14:39:20 -0400
Subject: [PATCH 03/10] move inferred_freq

---
 pandas/core/indexes/datetimelike.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 382abc888474c..df60ad28614eb 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -111,12 +111,6 @@ def freq(self, value) -> None:
     def freqstr(self) -> str | None:
         return self._data.freqstr
 
-    # error: Decorated property not supported
-    @cache_readonly  # type: ignore[misc]
-    @doc(DatetimeLikeArrayMixin.inferred_freq)
-    def inferred_freq(self) -> str | None:
-        return self._data.inferred_freq
-
     @cache_readonly
     def _resolution_obj(self) -> Resolution | None:
         return self._data._resolution_obj
@@ -438,6 +432,12 @@ def values(self) -> np.ndarray:
         # NB: For Datetime64TZ this is lossy
         return self._data._ndarray
 
+    # error: Decorated property not supported
+    @cache_readonly  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.inferred_freq)
+    def inferred_freq(self) -> str | None:
+        return self._data.inferred_freq
+
     # --------------------------------------------------------------------
     # Set Operation Methods
 

From 40b8d11d6c700ef7469b724f39dd592286430827 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Mon, 15 Aug 2022 22:10:06 -0400
Subject: [PATCH 04/10] move freq-setter in DatetimeTimedeltaMixin

---
 pandas/core/arrays/timedeltas.py    |  1 +
 pandas/core/indexes/datetimelike.py | 16 +++++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index 49cc91d1f3ea1..874976436b663 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -463,6 +463,7 @@ def __truediv__(self, other):
             result = self._ndarray / other
             freq = None
             if self.freq is not None:
+                # Tick division is not implemented, so operate on Timedelta
                 freq = self.freq.delta / other
                 freq = to_offset(freq)
             return type(self)._simple_new(result, dtype=result.dtype, freq=freq)
diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index df60ad28614eb..75497d03cc47b 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -100,11 +100,6 @@ def asi8(self) -> npt.NDArray[np.int64]:
     def freq(self) -> BaseOffset | None:
         return self._data.freq
 
-    @freq.setter
-    def freq(self, value) -> None:
-        # error: Property "freq" defined in "PeriodArray" is read-only
-        self._data.freq = value  # type: ignore[misc]
-
     # error: Decorated property not supported
     @property  # type: ignore[misc]
     @doc(DatetimeLikeArrayMixin.freqstr)
@@ -432,6 +427,17 @@ def values(self) -> np.ndarray:
         # NB: For Datetime64TZ this is lossy
         return self._data._ndarray
 
+    # error: Decorated property not supported
+    @property  # type: ignore[misc]
+    @doc(DatetimeLikeArrayMixin.freq)
+    def freq(self) -> BaseOffset | None:
+        # needed to define the setter (same as in DatetimeIndexOpsMixin)
+        return self._data.freq
+
+    @freq.setter
+    def freq(self, value) -> None:
+        self._data.freq = value
+
     # error: Decorated property not supported
     @cache_readonly  # type: ignore[misc]
     @doc(DatetimeLikeArrayMixin.inferred_freq)

From 05c7e0fdafa643c078ad35ccb7c3f9954291ecf5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Sat, 20 Aug 2022 09:42:43 -0400
Subject: [PATCH 05/10] fix dev test

---
 pandas/tests/indexes/period/test_freq_attr.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/indexes/period/test_freq_attr.py b/pandas/tests/indexes/period/test_freq_attr.py
index e1ecffa4982bd..71115929121bc 100644
--- a/pandas/tests/indexes/period/test_freq_attr.py
+++ b/pandas/tests/indexes/period/test_freq_attr.py
@@ -20,7 +20,7 @@ def test_freq_setter_deprecated(self):
 
         # warning for setter
         msg = (
-            "property 'freq' of 'PeriodArray' object has no setter"
+            "property 'freq' of 'PeriodIndex' object has no setter"
             if PY311
             else "can't set attribute"
         )

From b00e4400b92b103f9d14fe3532d3868e2583d082 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Sat, 3 Sep 2022 09:47:04 -0400
Subject: [PATCH 06/10] make _resolution_obj abstract

---
 pandas/core/indexes/datetimelike.py | 16 ++++++++++------
 pandas/core/indexes/datetimes.py    |  6 +++++-
 pandas/core/indexes/timedeltas.py   |  7 +++++++
 3 files changed, 22 insertions(+), 7 deletions(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 7b03a9e9c4955..37d94ed93f285 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -3,6 +3,10 @@
 """
 from __future__ import annotations
 
+from abc import (
+    ABC,
+    abstractmethod,
+)
 from datetime import datetime
 import inspect
 from typing import (
@@ -73,7 +77,7 @@
 _TDT = TypeVar("_TDT", bound="DatetimeTimedeltaMixin")
 
 
-class DatetimeIndexOpsMixin(NDArrayBackedExtensionIndex):
+class DatetimeIndexOpsMixin(NDArrayBackedExtensionIndex, ABC):
     """
     Common ops mixin to support a unified interface datetimelike Index.
     """
@@ -106,9 +110,10 @@ def freq(self) -> BaseOffset | None:
     def freqstr(self) -> str | None:
         return self._data.freqstr
 
+    @abstractmethod
     @cache_readonly
-    def _resolution_obj(self) -> Resolution | None:
-        return self._data._resolution_obj
+    def _resolution_obj(self) -> Resolution:
+        ...
 
     # error: Decorated property not supported
     @cache_readonly  # type: ignore[misc]
@@ -238,8 +243,7 @@ def _summary(self, name=None) -> str:
     def _can_partial_date_slice(self, reso: Resolution) -> bool:
         # e.g. test_getitem_setitem_periodindex
         # History of conversation GH#3452, GH#3931, GH#2369, GH#14826
-        # error: Unsupported left operand type for > ("Resolution")
-        return reso > self._resolution_obj  # type: ignore[operator]
+        return reso > self._resolution_obj
         # NB: for DTI/PI, not TDI
 
     def _parsed_string_to_bounds(self, reso: Resolution, parsed):
@@ -397,7 +401,7 @@ def _maybe_cast_listlike_indexer(self, keyarr):
         return Index(res, dtype=res.dtype)
 
 
-class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin):
+class DatetimeTimedeltaMixin(DatetimeIndexOpsMixin, ABC):
     """
     Mixin class for methods shared by DatetimeIndex and TimedeltaIndex,
     but not PeriodIndex
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index f6e56422c38df..d6c5d81a8fae1 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -121,7 +121,7 @@ def _new_DatetimeIndex(cls, d):
     DatetimeArray,
     wrap=True,
 )
-@inherit_names(["is_normalized", "_resolution_obj"], DatetimeArray, cache=True)
+@inherit_names(["is_normalized"], DatetimeArray, cache=True)
 @inherit_names(
     [
         "tz",
@@ -307,6 +307,10 @@ def isocalendar(self) -> DataFrame:
         df = self._data.isocalendar()
         return df.set_index(self)
 
+    @cache_readonly
+    def _resolution_obj(self) -> Resolution:
+        return self._data._resolution_obj
+
     # --------------------------------------------------------------------
     # Constructors
 
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 12a8f2c0d5a9d..c7bcdac9c6739 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -112,6 +112,13 @@ def _engine_type(self) -> type[libindex.TimedeltaEngine]:
     # Use base class method instead of DatetimeTimedeltaMixin._get_string_slice
     _get_string_slice = Index._get_string_slice
 
+    # error: Return type "None" of "_resolution_obj" incompatible with return type
+    # "Resolution" in supertype "DatetimeIndexOpsMixin"
+    @property
+    def _resolution_obj(self) -> None:  # type: ignore[override]
+        # not used but need to implement it because it is an abstract method
+        return None
+
     # -------------------------------------------------------------------
     # Constructors
 

From f2af92953c17938344fe1153a46e3f5287c633ea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Sat, 3 Sep 2022 12:05:33 -0400
Subject: [PATCH 07/10] use property in abstract class

---
 pandas/core/indexes/datetimelike.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 37d94ed93f285..6ae2126eef3b9 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -111,7 +111,7 @@ def freqstr(self) -> str | None:
         return self._data.freqstr
 
     @abstractmethod
-    @cache_readonly
+    @property
     def _resolution_obj(self) -> Resolution:
         ...
 

From 4723a9bf9a384993d0c84b70ee059d903b553c42 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Sat, 3 Sep 2022 12:16:50 -0400
Subject: [PATCH 08/10] fix order

---
 pandas/core/indexes/datetimelike.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 6ae2126eef3b9..ab5fc8f06f5ab 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -110,8 +110,8 @@ def freq(self) -> BaseOffset | None:
     def freqstr(self) -> str | None:
         return self._data.freqstr
 
+    @cache_readonly
     @abstractmethod
-    @property
     def _resolution_obj(self) -> Resolution:
         ...
 

From 0f0fb06b07e02cf6d62341e11f9925d321d812bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Tue, 6 Sep 2022 19:27:48 -0400
Subject: [PATCH 09/10] address non-cast comments

---
 pandas/_libs/tslibs/offsets.pyi    |  3 +++
 pandas/core/arrays/datetimelike.py | 13 +++----------
 pandas/core/arrays/timedeltas.py   |  6 +++---
 3 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyi b/pandas/_libs/tslibs/offsets.pyi
index c3d550c7a5ba9..34c5c661f6ec9 100644
--- a/pandas/_libs/tslibs/offsets.pyi
+++ b/pandas/_libs/tslibs/offsets.pyi
@@ -13,6 +13,7 @@ from typing import (
 
 import numpy as np
 
+from pandas._libs.tslibs.nattype import NaTType
 from pandas._typing import npt
 
 from .timedeltas import Timedelta
@@ -49,6 +50,8 @@ class BaseOffset:
     @overload
     def __radd__(self, other: npt.NDArray[np.object_]) -> npt.NDArray[np.object_]: ...
     @overload
+    def __radd__(self, other: NaTType) -> NaTType: ...
+    @overload
     def __radd__(self: _BaseOffsetT, other: BaseOffset) -> _BaseOffsetT: ...
     @overload
     def __radd__(self, other: _DatetimeT) -> _DatetimeT: ...
diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 5b46ac9bf6476..95e2c15c4862a 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -552,12 +552,7 @@ def _concat_same_type(
 
             if obj.freq is not None and all(x.freq == obj.freq for x in to_concat):
                 pairs = zip(to_concat[:-1], to_concat[1:])
-                # error: No overload variant of "__radd__" of "BaseOffset" matches
-                # argument type "NaTType"
-                if all(
-                    pair[0][-1] + obj.freq == pair[1][0]  # type: ignore[operator]
-                    for pair in pairs
-                ):
+                if all(pair[0][-1] + obj.freq == pair[1][0] for pair in pairs):
                     new_freq = obj.freq
 
         new_obj._freq = new_freq
@@ -1435,10 +1430,8 @@ def _time_shift(
         if self.freq is None:
             raise NullFrequencyError("Cannot shift with no freq")
 
-        # error: No overload variant of "__radd__" of "BaseOffset" matches
-        # argument type "NaTType"
-        start = self[0] + periods * self.freq  # type: ignore[operator]
-        end = self[-1] + periods * self.freq  # type: ignore[operator]
+        start = self[0] + periods * self.freq
+        end = self[-1] + periods * self.freq
 
         # Note: in the DatetimeTZ case, _generate_range will infer the
         #  appropriate timezone from `start` and `end`, so tz does not need
diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index 8fdf86b9af707..a76491e04b93c 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -147,9 +147,9 @@ def _box_func(self, x: np.timedelta64) -> Timedelta | NaTType:
     # error: Decorated property not supported
     @property  # type: ignore[misc]
     @doc(dtl.DatetimeLikeArrayMixin.freq)
-    def freq(self) -> Tick:
-        # error: Incompatible return value type (got "Optional[BaseOffset]",
-        # expected "Tick")
+    def freq(self) -> Tick | None:
+        # error: Incompatible return value type (got "Optional[BaseOffset]", expected
+        # "Optional[Tick]")
         return self._freq  # type: ignore[return-value]
 
     @freq.setter

From 2ed057dcf3eae03dfe7862a52c7ca7ad22a26c6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Torsten=20W=C3=B6rtwein?= <twoertwein@gmail.com>
Date: Tue, 6 Sep 2022 19:43:21 -0400
Subject: [PATCH 10/10] add casts

---
 pandas/core/arrays/datetimelike.py | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 95e2c15c4862a..c946fc2ac6e13 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -1220,9 +1220,8 @@ def _sub_period(self, other: Period) -> npt.NDArray[np.object_]:
         new_i8_data = checked_add_with_arr(
             self.asi8, -other.ordinal, arr_mask=self._isnan
         )
-        # error: Item "None" of "Optional[BaseOffset]" has no attribute "base"
         new_data = np.array(
-            [self.freq.base * x for x in new_i8_data]  # type: ignore[union-attr]
+            [cast("PeriodArray", self).freq.base * x for x in new_i8_data]
         )
 
         if self._hasna:
@@ -1459,9 +1458,9 @@ def __add__(self, other):
             # as is_integer returns True for these
             if not is_period_dtype(self.dtype):
                 raise integer_op_not_supported(self)
-            # error: Item "None" of "Optional[BaseOffset]" has no attribute "n"
-            result = cast("PeriodArray", self)._addsub_int_array_or_scalar(
-                other * self.freq.n, operator.add  # type: ignore[union-attr]
+            self_periodarray = cast("PeriodArray", self)
+            result = self_periodarray._addsub_int_array_or_scalar(
+                other * self_periodarray.freq.n, operator.add
             )
 
         # array-like others