From cdd46baea78fd5739fb72c016266f64e024edb1e Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Wed, 16 Feb 2022 18:02:20 -0800
Subject: [PATCH 01/18] CI: Test on Cython 3.0 on numpydev

---
 ci/deps/actions-310-numpydev.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index 3e32665d5433f..2c53da6587425 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -15,7 +15,7 @@ dependencies:
   - pytz
   - pip
   - pip:
-    - cython==0.29.24 # GH#34014
+    - cython
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From 27a674b31e1f62a049f4ae1e8b745038948896f9 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Wed, 16 Feb 2022 19:36:19 -0800
Subject: [PATCH 02/18] try something

---
 pandas/_libs/tslibs/offsets.pyx | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index dc049e9195d3f..f2ec069c82714 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -441,6 +441,7 @@ cdef class BaseOffset:
     def __add__(self, other):
         if not isinstance(self, BaseOffset):
             # cython semantics; this is __radd__
+            # TODO: (Cython 3.0) remove this, this moved to __radd__
             return other.__add__(self)
 
         elif util.is_array(other) and other.dtype == object:
@@ -451,6 +452,9 @@ cdef class BaseOffset:
         except ApplyTypeError:
             return NotImplemented
 
+    def __radd__(self, other):
+        return other.__add__(self)
+
     def __sub__(self, other):
         if PyDateTime_Check(other):
             raise TypeError('Cannot subtract datetime from offset.')
@@ -902,6 +906,7 @@ cdef class Tick(SingleConstructorOffset):
     def __add__(self, other):
         if not isinstance(self, Tick):
             # cython semantics; this is __radd__
+            # TODO: (Cython 3.0) remove this, this moved to __radd__
             return other.__add__(self)
 
         if isinstance(other, Tick):
@@ -918,6 +923,8 @@ cdef class Tick(SingleConstructorOffset):
             raise OverflowError(
                 f"the add operation between {self} and {other} will overflow"
             ) from err
+    def __radd__(self, other):
+        return other.__add__(self)
 
     def _apply(self, other):
         # Timestamp can handle tz and nano sec, thus no need to use apply_wraps

From d22e5883f0dd75f81eb3e3019a675bb0d52aa023 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Thu, 17 Feb 2022 06:50:02 -0800
Subject: [PATCH 03/18] try something else

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index f2ec069c82714..5608736d0ac7b 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -453,7 +453,7 @@ cdef class BaseOffset:
             return NotImplemented
 
     def __radd__(self, other):
-        return other.__add__(self)
+        return self.__add__(other)
 
     def __sub__(self, other):
         if PyDateTime_Check(other):

From 646dcedc4fefb99073c699678704d03680d7c958 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Wed, 23 Feb 2022 17:55:02 -0800
Subject: [PATCH 04/18] update

---
 pandas/_libs/tslibs/offsets.pyx | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 5608736d0ac7b..85a8e290b9711 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -453,6 +453,9 @@ cdef class BaseOffset:
             return NotImplemented
 
     def __radd__(self, other):
+        # We land here because the other object doesn't know how to add
+        # offset. We can call our own add method since order of operations
+        # doesn't matter.
         return self.__add__(other)
 
     def __sub__(self, other):
@@ -462,12 +465,19 @@ cdef class BaseOffset:
             return type(self)(self.n - other.n, normalize=self.normalize,
                               **self.kwds)
         elif not isinstance(self, BaseOffset):
+            # TODO(Cython 3): remove, this moved to __rsub__
             # cython semantics, this is __rsub__
             return (-other).__add__(self)
         else:
             # e.g. PeriodIndex
             return NotImplemented
 
+    def __rsub__(self, other):
+        # We land here because the other object doesn't know how to sub
+        # offset. We can call our own add method since order of operations
+        # doesn't matter.
+        return self.__sub__(other)
+
     def __call__(self, other):
         warnings.warn(
             "DateOffset.__call__ is deprecated and will be removed in a future "
@@ -494,10 +504,17 @@ cdef class BaseOffset:
             return type(self)(n=other * self.n, normalize=self.normalize,
                               **self.kwds)
         elif not isinstance(self, BaseOffset):
+            # TODO: (Cython 3) remove this, this moved to __rmul__
             # cython semantics, this is __rmul__
             return other.__mul__(self)
         return NotImplemented
 
+    def __rmul__(self, other):
+        # We land here because the other object doesn't know how to mul
+        # offset. We can call our own mul method since order of operations
+        # doesn't matter.
+        return self.__mul__(other)
+
     def __neg__(self):
         # Note: we are deferring directly to __mul__ instead of __rmul__, as
         # that allows us to use methods that can go in a `cdef class`
@@ -882,6 +899,7 @@ cdef class Tick(SingleConstructorOffset):
 
     def __mul__(self, other):
         if not isinstance(self, Tick):
+            # TODO: Cython3, remove this, this moved to __rmul__
             # cython semantics, this is __rmul__
             return other.__mul__(self)
         if is_float_object(other):
@@ -895,6 +913,12 @@ cdef class Tick(SingleConstructorOffset):
             return new_self * other
         return BaseOffset.__mul__(self, other)
 
+    def __rmul__(self, other):
+        # We land here because the other object doesn't know how to mul
+        # offset. We can call our own mul method since order of operations
+        # doesn't matter.
+        return self.__mul__(other)
+
     def __truediv__(self, other):
         if not isinstance(self, Tick):
             # cython semantics mean the args are sometimes swapped
@@ -924,7 +948,10 @@ cdef class Tick(SingleConstructorOffset):
                 f"the add operation between {self} and {other} will overflow"
             ) from err
     def __radd__(self, other):
-        return other.__add__(self)
+        # We land here because the other object doesn't know how to add
+        # offset. We can call our own add method since order of operations
+        # doesn't matter.
+        return self.__add__(other)
 
     def _apply(self, other):
         # Timestamp can handle tz and nano sec, thus no need to use apply_wraps

From 4a8722779233538b35414072f355237fe88d7bc5 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Sat, 26 Feb 2022 14:24:14 -0800
Subject: [PATCH 05/18] install cython from master

---
 ci/deps/actions-310-numpydev.yaml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index 2c53da6587425..c686744ecf19e 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -15,7 +15,8 @@ dependencies:
   - pytz
   - pip
   - pip:
-    - cython
+    #- cython # TODO: don't install from master after Cython 3.0.0a11 is released
+    - "git+https://github.com/cython/cython.git@master"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From d5a9c7e2041a91ab85b31035471c54b2ce21f54d Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Sun, 27 Feb 2022 09:21:20 -0800
Subject: [PATCH 06/18] try to get further in the test suite

---
 ci/deps/actions-310-numpydev.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index c686744ecf19e..c8967125738cc 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -16,7 +16,7 @@ dependencies:
   - pip
   - pip:
     #- cython # TODO: don't install from master after Cython 3.0.0a11 is released
-    - "git+https://github.com/cython/cython.git@master"
+    - "git+https://github.com/da-woods/cython.git@object-none"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From 5aa9f132f9376e18107755b9fcc160c852e0c322 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Sun, 27 Feb 2022 10:43:34 -0800
Subject: [PATCH 07/18] revert back to cython master branch

---
 ci/deps/actions-310-numpydev.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index c8967125738cc..c686744ecf19e 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -16,7 +16,7 @@ dependencies:
   - pip
   - pip:
     #- cython # TODO: don't install from master after Cython 3.0.0a11 is released
-    - "git+https://github.com/da-woods/cython.git@object-none"
+    - "git+https://github.com/cython/cython.git@master"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From de88da99a1837a454fb8bf6f0fbd2e39bad837ad Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Mon, 28 Feb 2022 18:22:00 -0800
Subject: [PATCH 08/18] try to get farther in the test suite

---
 ci/deps/actions-310-numpydev.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index c686744ecf19e..1ee233398b8ef 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -16,7 +16,7 @@ dependencies:
   - pip
   - pip:
     #- cython # TODO: don't install from master after Cython 3.0.0a11 is released
-    - "git+https://github.com/cython/cython.git@master"
+    - "git+https://github.com/lithomas1/cython.git@debug-pandas"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From ae3e6fa72cc675e4a8581c9c24eabbda6cd3d420 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Mon, 28 Feb 2022 20:58:06 -0800
Subject: [PATCH 09/18] fixes to offsets.pyx

---
 pandas/_libs/tslibs/offsets.pyx | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 85a8e290b9711..b04cf9cb40dd0 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -474,9 +474,8 @@ cdef class BaseOffset:
 
     def __rsub__(self, other):
         # We land here because the other object doesn't know how to sub
-        # offset. We can call our own add method since order of operations
-        # doesn't matter.
-        return self.__sub__(other)
+        # offset.
+        return (-self).__add__(other)
 
     def __call__(self, other):
         warnings.warn(
@@ -927,6 +926,10 @@ cdef class Tick(SingleConstructorOffset):
             result = self.delta.__truediv__(other)
         return _wrap_timedelta_result(result)
 
+    def __rtruediv__(self, other):
+        result = self.delta.__rtruediv__(other)
+        return _wrap_timedelta_result(result)
+
     def __add__(self, other):
         if not isinstance(self, Tick):
             # cython semantics; this is __radd__

From dc7517a96a59b7f597bc3b0c241bcad6afe7d779 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Tue, 1 Mar 2022 18:29:55 -0800
Subject: [PATCH 10/18] fix some more binops

---
 pandas/_libs/tslibs/nattype.pyx    | 23 +++++++++++++++++++++++
 pandas/_libs/tslibs/period.pyx     | 11 +++++++++++
 pandas/_libs/tslibs/timestamps.pyx |  9 +++++++++
 3 files changed, 43 insertions(+)

diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
index e6a70177463b8..b9ef6e5e1e450 100644
--- a/pandas/_libs/tslibs/nattype.pyx
+++ b/pandas/_libs/tslibs/nattype.pyx
@@ -154,6 +154,7 @@ cdef class _NaT(datetime):
 
     def __add__(self, other):
         if self is not c_NaT:
+            # TODO: Cython 3, remove this it moved to __radd__
             # cython __radd__ semantics
             self, other = other, self
 
@@ -180,6 +181,9 @@ cdef class _NaT(datetime):
         # Includes Period, DateOffset going through here
         return NotImplemented
 
+    def __radd__(self, other):
+        return self.__add__(other)
+
     def __sub__(self, other):
         # Duplicate some logic from _Timestamp.__sub__ to avoid needing
         # to subclass; allows us to @final(_Timestamp.__sub__)
@@ -188,6 +192,7 @@ cdef class _NaT(datetime):
 
         if self is not c_NaT:
             # cython __rsub__ semantics
+            # TODO: Cython 3, remove __rsub__ logic from here
             self, other = other, self
             is_rsub = True
 
@@ -231,6 +236,24 @@ cdef class _NaT(datetime):
         # Includes Period, DateOffset going through here
         return NotImplemented
 
+    def __rsub__(self, other):
+        if util.is_array(other):
+            if other.dtype.kind == "m":
+                # timedelta64 - NaT we have to treat NaT as timedelta64
+                #  for this to be meaningful, and the result is timedelta64
+                result = np.empty(other.shape, dtype="timedelta64[ns]")
+                result.fill("NaT")
+                return result
+
+            elif other.dtype.kind == "M":
+                # We treat NaT as a datetime, so regardless of whether this is
+                #  NaT - other or other - NaT, the result is timedelta64
+                result = np.empty(other.shape, dtype="timedelta64[ns]")
+                result.fill("NaT")
+                return result
+        # other cases are same, swap operands is allowed even though we subtract because this is NaT
+        return self.__sub__(other)
+
     def __pos__(self):
         return NaT
 
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 8c331b13f9735..24cb1f97c7c7c 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1739,6 +1739,7 @@ cdef class _Period(PeriodMixin):
     def __add__(self, other):
         if not is_period_object(self):
             # cython semantics; this is analogous to a call to __radd__
+            # TODO: Cython3, remove this
             if self is NaT:
                 return NaT
             return other.__add__(self)
@@ -1763,6 +1764,11 @@ cdef class _Period(PeriodMixin):
 
         return NotImplemented
 
+    def __radd__(self, other):
+        if other is NaT:
+            return NaT
+        return self.__add__(other)
+
     def __sub__(self, other):
         if not is_period_object(self):
             # cython semantics; this is like a call to __rsub__
@@ -1789,6 +1795,11 @@ cdef class _Period(PeriodMixin):
 
         return NotImplemented
 
+    def __rsub__(self, other):
+        if other is NaT:
+            return NaT
+        return NotImplemented
+
     def asfreq(self, freq, how='E') -> "Period":
         """
         Convert Period to desired frequency, at the start or end of the interval.
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index aad49bd70b120..94a0a57739dc9 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -308,9 +308,13 @@ cdef class _Timestamp(ABCTimestamp):
 
         elif not isinstance(self, _Timestamp):
             # cython semantics, args have been switched and this is __radd__
+            # TODO: Cython 3, remove this it moved to __radd__
             return other.__add__(self)
         return NotImplemented
 
+    def __radd__(self, other):
+        return self.__add__(other)
+
     def __sub__(self, other):
 
         if is_any_td_scalar(other) or is_integer_object(other):
@@ -367,10 +371,15 @@ cdef class _Timestamp(ABCTimestamp):
         elif is_datetime64_object(self):
             # GH#28286 cython semantics for __rsub__, `other` is actually
             #  the Timestamp
+            # TODO: Cython 3 remove this, this moved to __rsub__
             return type(other)(self) - other
 
         return NotImplemented
 
+    def __rsub__(self, other):
+        if is_datetime64_object(other):
+            return type(self)(other) - self
+        return NotImplemented
     # -----------------------------------------------------------------
 
     cdef int64_t _maybe_convert_value_to_local(self):

From 416bca57e18823e93502bede6c72ea6b9f8cb39d Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Sat, 5 Mar 2022 14:41:17 -0800
Subject: [PATCH 11/18] fix some more tests

---
 pandas/_libs/interval.pyx          | 14 ++++++++++++++
 pandas/_libs/tslibs/timestamps.pyx |  7 +++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/interval.pyx b/pandas/_libs/interval.pyx
index aba635e19995a..4b515f183e347 100644
--- a/pandas/_libs/interval.pyx
+++ b/pandas/_libs/interval.pyx
@@ -414,6 +414,15 @@ cdef class Interval(IntervalMixin):
             return Interval(y.left + self, y.right + self, closed=y.closed)
         return NotImplemented
 
+    def __radd__(self, y):
+        if (
+                isinstance(y, numbers.Number)
+                or PyDelta_Check(y)
+                or is_timedelta64_object(y)
+        ):
+            return self.__add__(y)
+        return NotImplemented
+
     def __sub__(self, y):
         if (
             isinstance(y, numbers.Number)
@@ -430,6 +439,11 @@ cdef class Interval(IntervalMixin):
             return Interval(y.left * self, y.right * self, closed=y.closed)
         return NotImplemented
 
+    def __rmul__(self, y):
+        if isinstance(y, numbers.Number):
+            return self.__mul__(y)
+        return NotImplemented
+
     def __truediv__(self, y):
         if isinstance(y, numbers.Number):
             return Interval(self.left / y, self.right / y, closed=self.closed)
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 94a0a57739dc9..c358d51f97cc4 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -313,7 +313,10 @@ cdef class _Timestamp(ABCTimestamp):
         return NotImplemented
 
     def __radd__(self, other):
-        return self.__add__(other)
+        # Have to duplicate checks to avoid infinite recursion due to NotImplemented
+        if is_any_td_scalar(other) or is_integer_object(other) or is_array(other):
+            return self.__add__(other)
+        return NotImplemented
 
     def __sub__(self, other):
 
@@ -377,7 +380,7 @@ cdef class _Timestamp(ABCTimestamp):
         return NotImplemented
 
     def __rsub__(self, other):
-        if is_datetime64_object(other):
+        if PyDateTime_Check(other) or is_datetime64_object(other):
             return type(self)(other) - self
         return NotImplemented
     # -----------------------------------------------------------------

From 127e97b9fb76ca2563a490209a4ad7a23a0d3b76 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Mon, 7 Mar 2022 20:06:48 -0800
Subject: [PATCH 12/18] workaround cython bug?

---
 pandas/_libs/tslibs/timestamps.pyx | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index c358d51f97cc4..757045619a55d 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -282,8 +282,10 @@ cdef class _Timestamp(ABCTimestamp):
         return other.tzinfo is None
 
     def __add__(self, other):
-        cdef:
-            int64_t nanos = 0
+        # TODO: There is a Cython 3 bug where self.values + nanos
+        # would silently overflow if this is defined
+        #cdef:
+        #    int64_t nanos = 0
 
         if is_any_td_scalar(other):
             nanos = delta_to_nanoseconds(other)
@@ -344,6 +346,7 @@ cdef class _Timestamp(ABCTimestamp):
                 and (PyDateTime_Check(other) or is_datetime64_object(other))):
             # both_timestamps is to determine whether Timedelta(self - other)
             # should raise the OOB error, or fall back returning a timedelta.
+            # TODO: Cython 3: clean out the bits that moved to __rsub__
             both_timestamps = (isinstance(other, _Timestamp) and
                                isinstance(self, _Timestamp))
             if isinstance(self, _Timestamp):
@@ -380,7 +383,14 @@ cdef class _Timestamp(ABCTimestamp):
         return NotImplemented
 
     def __rsub__(self, other):
-        if PyDateTime_Check(other) or is_datetime64_object(other):
+        if PyDateTime_Check(other):
+            try:
+                return type(self)(other) - self
+            except (OverflowError, OutOfBoundsDatetime) as err:
+                # We get here in stata tests, fall back to stdlib datetime
+                #  method and return stdlib timedelta object
+                pass
+        elif is_datetime64_object(other):
             return type(self)(other) - self
         return NotImplemented
     # -----------------------------------------------------------------

From 7259c4cca5a86187e15c11ac8548b0f89069fd5d Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Mon, 14 Mar 2022 13:01:31 -0700
Subject: [PATCH 13/18] standardize todos

---
 pandas/_libs/tslibs/nattype.pyx    |  4 ++--
 pandas/_libs/tslibs/offsets.pyx    | 12 +++---------
 pandas/_libs/tslibs/period.pyx     |  2 +-
 pandas/_libs/tslibs/timestamps.pyx |  6 +++---
 4 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
index b9ef6e5e1e450..8e1b86182f2bc 100644
--- a/pandas/_libs/tslibs/nattype.pyx
+++ b/pandas/_libs/tslibs/nattype.pyx
@@ -154,7 +154,7 @@ cdef class _NaT(datetime):
 
     def __add__(self, other):
         if self is not c_NaT:
-            # TODO: Cython 3, remove this it moved to __radd__
+            # TODO(cython3): remove this it moved to __radd__
             # cython __radd__ semantics
             self, other = other, self
 
@@ -192,7 +192,7 @@ cdef class _NaT(datetime):
 
         if self is not c_NaT:
             # cython __rsub__ semantics
-            # TODO: Cython 3, remove __rsub__ logic from here
+            # TODO(cython3): remove __rsub__ logic from here
             self, other = other, self
             is_rsub = True
 
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index b04cf9cb40dd0..e16bb4c0a6cac 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -441,7 +441,7 @@ cdef class BaseOffset:
     def __add__(self, other):
         if not isinstance(self, BaseOffset):
             # cython semantics; this is __radd__
-            # TODO: (Cython 3.0) remove this, this moved to __radd__
+            # TODO(cython3): remove this, this moved to __radd__
             return other.__add__(self)
 
         elif util.is_array(other) and other.dtype == object:
@@ -503,7 +503,7 @@ cdef class BaseOffset:
             return type(self)(n=other * self.n, normalize=self.normalize,
                               **self.kwds)
         elif not isinstance(self, BaseOffset):
-            # TODO: (Cython 3) remove this, this moved to __rmul__
+            # TODO(cython3): remove this, this moved to __rmul__
             # cython semantics, this is __rmul__
             return other.__mul__(self)
         return NotImplemented
@@ -913,9 +913,6 @@ cdef class Tick(SingleConstructorOffset):
         return BaseOffset.__mul__(self, other)
 
     def __rmul__(self, other):
-        # We land here because the other object doesn't know how to mul
-        # offset. We can call our own mul method since order of operations
-        # doesn't matter.
         return self.__mul__(other)
 
     def __truediv__(self, other):
@@ -933,7 +930,7 @@ cdef class Tick(SingleConstructorOffset):
     def __add__(self, other):
         if not isinstance(self, Tick):
             # cython semantics; this is __radd__
-            # TODO: (Cython 3.0) remove this, this moved to __radd__
+            # TODO(cython3): remove this, this moved to __radd__
             return other.__add__(self)
 
         if isinstance(other, Tick):
@@ -951,9 +948,6 @@ cdef class Tick(SingleConstructorOffset):
                 f"the add operation between {self} and {other} will overflow"
             ) from err
     def __radd__(self, other):
-        # We land here because the other object doesn't know how to add
-        # offset. We can call our own add method since order of operations
-        # doesn't matter.
         return self.__add__(other)
 
     def _apply(self, other):
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index ecce5e4f2adeb..64596ebe710ab 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1720,7 +1720,7 @@ cdef class _Period(PeriodMixin):
     def __add__(self, other):
         if not is_period_object(self):
             # cython semantics; this is analogous to a call to __radd__
-            # TODO: Cython3, remove this
+            # TODO(cython3): remove this
             if self is NaT:
                 return NaT
             return other.__add__(self)
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 757045619a55d..e115f4b7c76b6 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -310,7 +310,7 @@ cdef class _Timestamp(ABCTimestamp):
 
         elif not isinstance(self, _Timestamp):
             # cython semantics, args have been switched and this is __radd__
-            # TODO: Cython 3, remove this it moved to __radd__
+            # TODO(cython3): remove this it moved to __radd__
             return other.__add__(self)
         return NotImplemented
 
@@ -346,7 +346,7 @@ cdef class _Timestamp(ABCTimestamp):
                 and (PyDateTime_Check(other) or is_datetime64_object(other))):
             # both_timestamps is to determine whether Timedelta(self - other)
             # should raise the OOB error, or fall back returning a timedelta.
-            # TODO: Cython 3: clean out the bits that moved to __rsub__
+            # TODO(cython3): clean out the bits that moved to __rsub__
             both_timestamps = (isinstance(other, _Timestamp) and
                                isinstance(self, _Timestamp))
             if isinstance(self, _Timestamp):
@@ -377,7 +377,7 @@ cdef class _Timestamp(ABCTimestamp):
         elif is_datetime64_object(self):
             # GH#28286 cython semantics for __rsub__, `other` is actually
             #  the Timestamp
-            # TODO: Cython 3 remove this, this moved to __rsub__
+            # TODO(cython3): remove this, this moved to __rsub__
             return type(other)(self) - other
 
         return NotImplemented

From f123a47ff420c821291652f2cd2849b94670b480 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Tue, 15 Mar 2022 18:10:21 -0700
Subject: [PATCH 14/18] switch to master branch

---
 ci/deps/actions-310-numpydev.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/ci/deps/actions-310-numpydev.yaml b/ci/deps/actions-310-numpydev.yaml
index 1ee233398b8ef..c686744ecf19e 100644
--- a/ci/deps/actions-310-numpydev.yaml
+++ b/ci/deps/actions-310-numpydev.yaml
@@ -16,7 +16,7 @@ dependencies:
   - pip
   - pip:
     #- cython # TODO: don't install from master after Cython 3.0.0a11 is released
-    - "git+https://github.com/lithomas1/cython.git@debug-pandas"
+    - "git+https://github.com/cython/cython.git@master"
     - "--extra-index-url https://pypi.anaconda.org/scipy-wheels-nightly/simple"
     - "--pre"
     - "numpy"

From 00c492de53a1b31007acd5a1cea15d37a4c1fe60 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Mon, 21 Mar 2022 10:56:38 -0700
Subject: [PATCH 15/18] address comments

---
 pandas/_libs/interval.pyx       | 20 ++++++++++++--------
 pandas/_libs/tslibs/nattype.pyx |  2 ++
 pandas/_libs/tslibs/offsets.pyx | 11 ++---------
 3 files changed, 16 insertions(+), 17 deletions(-)

diff --git a/pandas/_libs/interval.pyx b/pandas/_libs/interval.pyx
index 4b515f183e347..f31eb6a117a03 100644
--- a/pandas/_libs/interval.pyx
+++ b/pandas/_libs/interval.pyx
@@ -404,6 +404,8 @@ cdef class Interval(IntervalMixin):
         ):
             return Interval(self.left + y, self.right + y, closed=self.closed)
         elif (
+            # __radd__ pattern
+            # TODO(cython3): remove this
             isinstance(y, Interval)
             and (
                 isinstance(self, numbers.Number)
@@ -414,13 +416,13 @@ cdef class Interval(IntervalMixin):
             return Interval(y.left + self, y.right + self, closed=y.closed)
         return NotImplemented
 
-    def __radd__(self, y):
+    def __radd__(self, other):
         if (
-                isinstance(y, numbers.Number)
-                or PyDelta_Check(y)
-                or is_timedelta64_object(y)
+                isinstance(other, numbers.Number)
+                or PyDelta_Check(other)
+                or is_timedelta64_object(other)
         ):
-            return self.__add__(y)
+            return Interval(self.left + other, self.right + other, closed=self.closed)
         return NotImplemented
 
     def __sub__(self, y):
@@ -436,12 +438,14 @@ cdef class Interval(IntervalMixin):
         if isinstance(y, numbers.Number):
             return Interval(self.left * y, self.right * y, closed=self.closed)
         elif isinstance(y, Interval) and isinstance(self, numbers.Number):
+            # __radd__ semantics
+            # TODO(cython3): remove this
             return Interval(y.left * self, y.right * self, closed=y.closed)
         return NotImplemented
 
-    def __rmul__(self, y):
-        if isinstance(y, numbers.Number):
-            return self.__mul__(y)
+    def __rmul__(self, other):
+        if isinstance(other, numbers.Number):
+            return Interval(self.left * other, self.right * other, closed=self.closed)
         return NotImplemented
 
     def __truediv__(self, y):
diff --git a/pandas/_libs/tslibs/nattype.pyx b/pandas/_libs/tslibs/nattype.pyx
index 8e1b86182f2bc..d2ea2a4925a2c 100644
--- a/pandas/_libs/tslibs/nattype.pyx
+++ b/pandas/_libs/tslibs/nattype.pyx
@@ -216,6 +216,8 @@ cdef class _NaT(datetime):
                     result.fill("NaT")
                     return result
 
+                # __rsub__ logic here
+                # TODO(cython3): remove this, move above code out of ``if not is_rsub`` block
                 # timedelta64 - NaT we have to treat NaT as timedelta64
                 #  for this to be meaningful, and the result is timedelta64
                 result = np.empty(other.shape, dtype="timedelta64[ns]")
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index e16bb4c0a6cac..86ddd5c502023 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -453,9 +453,6 @@ cdef class BaseOffset:
             return NotImplemented
 
     def __radd__(self, other):
-        # We land here because the other object doesn't know how to add
-        # offset. We can call our own add method since order of operations
-        # doesn't matter.
         return self.__add__(other)
 
     def __sub__(self, other):
@@ -473,8 +470,6 @@ cdef class BaseOffset:
             return NotImplemented
 
     def __rsub__(self, other):
-        # We land here because the other object doesn't know how to sub
-        # offset.
         return (-self).__add__(other)
 
     def __call__(self, other):
@@ -509,9 +504,6 @@ cdef class BaseOffset:
         return NotImplemented
 
     def __rmul__(self, other):
-        # We land here because the other object doesn't know how to mul
-        # offset. We can call our own mul method since order of operations
-        # doesn't matter.
         return self.__mul__(other)
 
     def __neg__(self):
@@ -898,7 +890,7 @@ cdef class Tick(SingleConstructorOffset):
 
     def __mul__(self, other):
         if not isinstance(self, Tick):
-            # TODO: Cython3, remove this, this moved to __rmul__
+            # TODO(cython3), remove this, this moved to __rmul__
             # cython semantics, this is __rmul__
             return other.__mul__(self)
         if is_float_object(other):
@@ -947,6 +939,7 @@ cdef class Tick(SingleConstructorOffset):
             raise OverflowError(
                 f"the add operation between {self} and {other} will overflow"
             ) from err
+
     def __radd__(self, other):
         return self.__add__(other)
 

From 92325d7c55ea238c64c26ed33aecab70d607c9ab Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Tue, 22 Mar 2022 09:52:13 -0700
Subject: [PATCH 16/18] handle overflow correctly

---
 pandas/_libs/tslibs/timestamps.pyx | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 71170e4b55a70..69a98f57b1da5 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -281,15 +281,18 @@ cdef class _Timestamp(ABCTimestamp):
             return other.tzinfo is not None
         return other.tzinfo is None
 
+    @cython.overflowcheck(True)
     def __add__(self, other):
-        # TODO: There is a Cython 3 bug where self.values + nanos
-        # would silently overflow if this is defined
-        #cdef:
-        #    int64_t nanos = 0
+        cdef:
+           int64_t nanos = 0
 
         if is_any_td_scalar(other):
             nanos = delta_to_nanoseconds(other)
-            result = type(self)(self.value + nanos, tz=self.tzinfo)
+            try:
+                result = type(self)(self.value + nanos, tz=self.tzinfo)
+            except OverflowError:
+                # Use Python ints
+                result = type(self)(int(self.value) + int(nanos), tz=self.tzinfo)
             if result is not NaT:
                 result._set_freq(self._freq)  # avoid warning in constructor
             return result

From eaea742db66aea5fadfbae5331fe50dd6df5e751 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Thu, 24 Mar 2022 20:03:35 -0700
Subject: [PATCH 17/18] address comments

---
 pandas/_libs/tslibs/offsets.pyx    | 2 +-
 pandas/_libs/tslibs/timestamps.pyx | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index fb46b277b6d52..5a7f931292e7b 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -471,7 +471,7 @@ cdef class BaseOffset:
             return type(self)(self.n - other.n, normalize=self.normalize,
                               **self.kwds)
         elif not isinstance(self, BaseOffset):
-            # TODO(Cython 3): remove, this moved to __rsub__
+            # TODO(cython3): remove, this moved to __rsub__
             # cython semantics, this is __rsub__
             return (-other).__add__(self)
         else:
diff --git a/pandas/_libs/tslibs/timestamps.pyx b/pandas/_libs/tslibs/timestamps.pyx
index 69a98f57b1da5..7cb52d6cd3527 100644
--- a/pandas/_libs/tslibs/timestamps.pyx
+++ b/pandas/_libs/tslibs/timestamps.pyx
@@ -284,7 +284,7 @@ cdef class _Timestamp(ABCTimestamp):
     @cython.overflowcheck(True)
     def __add__(self, other):
         cdef:
-           int64_t nanos = 0
+            int64_t nanos = 0
 
         if is_any_td_scalar(other):
             nanos = delta_to_nanoseconds(other)
@@ -292,6 +292,7 @@ cdef class _Timestamp(ABCTimestamp):
                 result = type(self)(self.value + nanos, tz=self.tzinfo)
             except OverflowError:
                 # Use Python ints
+                # Hit in test_tdi_add_overflow
                 result = type(self)(int(self.value) + int(nanos), tz=self.tzinfo)
             if result is not NaT:
                 result._set_freq(self._freq)  # avoid warning in constructor

From f4674520c54831b867b820d708b6d7c86bf58308 Mon Sep 17 00:00:00 2001
From: Thomas Li <47963215+lithomas1@users.noreply.github.com>
Date: Thu, 24 Mar 2022 20:41:53 -0700
Subject: [PATCH 18/18] test something

---
 pandas/_libs/tslibs/period.pyx | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 9117f2cf13b50..c18d71e324a28 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1736,13 +1736,12 @@ cdef class _Period(PeriodMixin):
         return NotImplemented
 
     def __radd__(self, other):
-        if other is NaT:
-            return NaT
         return self.__add__(other)
 
     def __sub__(self, other):
         if not is_period_object(self):
             # cython semantics; this is like a call to __rsub__
+            # TODO(cython3): remove this
             if self is NaT:
                 return NaT
             return NotImplemented