From f780345d7687733f2f64679fa3eb73603f038f02 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Thu, 26 Oct 2023 08:52:05 -0700
Subject: [PATCH 1/5] REF: Avoid np.can_cast for scalar inference for NEP 50

---
 pandas/core/dtypes/cast.py | 24 ++++++++++--------------
 1 file changed, 10 insertions(+), 14 deletions(-)

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 27625db766862..d6882fee7aec3 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -699,7 +699,9 @@ def _maybe_promote(dtype: np.dtype, fill_value=np.nan):
             dtype = np.dtype(np.object_)
 
         elif issubclass(dtype.type, np.integer):
-            if not np.can_cast(fill_value, dtype):
+            try:
+                np_can_hold_element(dtype, fill_value)
+            except (LossySetitemError, NotImplementedError):
                 # upcast to prevent overflow
                 mst = np.min_scalar_type(fill_value)
                 dtype = np.promote_types(dtype, mst)
@@ -1751,9 +1753,14 @@ def np_can_hold_element(dtype: np.dtype, element: Any) -> Any:
 
     if dtype.kind in "iu":
         if isinstance(element, range):
-            if _dtype_can_hold_range(element, dtype):
+            if not len(element):
+                return True
+            try:
+                np_can_hold_element(dtype, element.start)
+                np_can_hold_element(dtype, element.stop)
                 return element
-            raise LossySetitemError
+            except (LossySetitemError, NotImplementedError) as err:
+                raise LossySetitemError from err
 
         if is_integer(element) or (is_float(element) and element.is_integer()):
             # e.g. test_setitem_series_int8 if we have a python int 1
@@ -1906,14 +1913,3 @@ def np_can_hold_element(dtype: np.dtype, element: Any) -> Any:
         raise LossySetitemError
 
     raise NotImplementedError(dtype)
-
-
-def _dtype_can_hold_range(rng: range, dtype: np.dtype) -> bool:
-    """
-    _maybe_infer_dtype_type infers to int64 (and float64 for very large endpoints),
-    but in many cases a range can be held by a smaller integer dtype.
-    Check if this is one of those cases.
-    """
-    if not len(rng):
-        return True
-    return np.can_cast(rng[0], dtype) and np.can_cast(rng[-1], dtype)

From 64b03f939c1bed6aebd44c09fb688fbf6299201a Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Thu, 26 Oct 2023 09:19:04 -0700
Subject: [PATCH 2/5] Use helper function

---
 pandas/core/dtypes/cast.py | 45 +++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 10 deletions(-)

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index d6882fee7aec3..2b146010b2e12 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -699,9 +699,7 @@ def _maybe_promote(dtype: np.dtype, fill_value=np.nan):
             dtype = np.dtype(np.object_)
 
         elif issubclass(dtype.type, np.integer):
-            try:
-                np_can_hold_element(dtype, fill_value)
-            except (LossySetitemError, NotImplementedError):
+            if not np_can_cast_scalar(fill_value, dtype):
                 # upcast to prevent overflow
                 mst = np.min_scalar_type(fill_value)
                 dtype = np.promote_types(dtype, mst)
@@ -1753,14 +1751,9 @@ def np_can_hold_element(dtype: np.dtype, element: Any) -> Any:
 
     if dtype.kind in "iu":
         if isinstance(element, range):
-            if not len(element):
-                return True
-            try:
-                np_can_hold_element(dtype, element.start)
-                np_can_hold_element(dtype, element.stop)
+            if _dtype_can_hold_range(element, dtype):
                 return element
-            except (LossySetitemError, NotImplementedError) as err:
-                raise LossySetitemError from err
+            raise LossySetitemError
 
         if is_integer(element) or (is_float(element) and element.is_integer()):
             # e.g. test_setitem_series_int8 if we have a python int 1
@@ -1913,3 +1906,35 @@ def np_can_hold_element(dtype: np.dtype, element: Any) -> Any:
         raise LossySetitemError
 
     raise NotImplementedError(dtype)
+
+
+def _dtype_can_hold_range(rng: range, dtype: np.dtype) -> bool:
+    """
+    _maybe_infer_dtype_type infers to int64 (and float64 for very large endpoints),
+    but in many cases a range can be held by a smaller integer dtype.
+    Check if this is one of those cases.
+    """
+    if not len(rng):
+        return True
+    return np_can_cast_scalar(rng.start, dtype) and np_can_cast_scalar(rng.end, dtype)
+
+
+def np_can_cast_scalar(element: Scalar, dtype: np.dtype) -> bool:
+    """
+    np.can_cast pandas-equivalent for pre 2-0 behavior that allowed scalar
+    inference
+
+    Parameters
+    ----------
+    element : Scalar
+    dtype : np.dtype
+
+    Returns
+    -------
+    bool
+    """
+    try:
+        np_can_hold_element(dtype, element)
+        return True
+    except (LossySetitemError, NotImplementedError):
+        return False

From 2b5c4b0a23ae35c026b9844554029f993ee7a5f4 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Thu, 26 Oct 2023 09:56:59 -0700
Subject: [PATCH 3/5] end->stop

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

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 2b146010b2e12..8191476944d22 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -1916,7 +1916,7 @@ def _dtype_can_hold_range(rng: range, dtype: np.dtype) -> bool:
     """
     if not len(rng):
         return True
-    return np_can_cast_scalar(rng.start, dtype) and np_can_cast_scalar(rng.end, dtype)
+    return np_can_cast_scalar(rng.start, dtype) and np_can_cast_scalar(rng.stop, dtype)
 
 
 def np_can_cast_scalar(element: Scalar, dtype: np.dtype) -> bool:

From c55e46ec5f41f242d94dd9936959ebd84e69f7a3 Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Thu, 26 Oct 2023 11:18:53 -0700
Subject: [PATCH 4/5] ignore typing

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

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 8191476944d22..716d1a78f93c5 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -699,7 +699,7 @@ def _maybe_promote(dtype: np.dtype, fill_value=np.nan):
             dtype = np.dtype(np.object_)
 
         elif issubclass(dtype.type, np.integer):
-            if not np_can_cast_scalar(fill_value, dtype):
+            if not np_can_cast_scalar(fill_value, dtype):  # type: ignore[arg-type]
                 # upcast to prevent overflow
                 mst = np.min_scalar_type(fill_value)
                 dtype = np.promote_types(dtype, mst)

From 6176b11e830fb72e2b32ea00b55645621dd3c0cd Mon Sep 17 00:00:00 2001
From: Matthew Roeschke <10647082+mroeschke@users.noreply.github.com>
Date: Thu, 26 Oct 2023 14:11:43 -0700
Subject: [PATCH 5/5] Address NEP 50 later

---
 ci/run_tests.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ci/run_tests.sh b/ci/run_tests.sh
index 48ef21686a26f..6a70ea1df3e71 100755
--- a/ci/run_tests.sh
+++ b/ci/run_tests.sh
@@ -10,7 +10,8 @@ echo PYTHONHASHSEED=$PYTHONHASHSEED
 
 COVERAGE="-s --cov=pandas --cov-report=xml --cov-append --cov-config=pyproject.toml"
 
-PYTEST_CMD="MESONPY_EDITABLE_VERBOSE=1 PYTHONDEVMODE=1 PYTHONWARNDEFAULTENCODING=1 pytest -r fEs -n $PYTEST_WORKERS --dist=loadfile $TEST_ARGS $COVERAGE $PYTEST_TARGET"
+# TODO: Support NEP 50 and remove NPY_PROMOTION_STATE
+PYTEST_CMD="NPY_PROMOTION_STATE=legacy MESONPY_EDITABLE_VERBOSE=1 PYTHONDEVMODE=1 PYTHONWARNDEFAULTENCODING=1 pytest -r fEs -n $PYTEST_WORKERS --dist=loadfile $TEST_ARGS $COVERAGE $PYTEST_TARGET"
 
 if [[ "$PATTERN" ]]; then
   PYTEST_CMD="$PYTEST_CMD -m \"$PATTERN\""