fix: raise error when converting NaT to int

Previously, it was converting it to -2^63.

Author: Alvaro-Kothe

doc/source/whatsnew/v3.0.0.rst

@@ -964,6 +964,7 @@ Datetimelike
 - Bug in :meth:`to_datetime` reports incorrect index in case of any failure scenario. (:issue:`58298`)
 - Bug in :meth:`to_datetime` with ``format="ISO8601"`` and ``utc=True`` where naive timestamps incorrectly inherited timezone offset from previous timestamps in a series. (:issue:`61389`)
 - Bug in :meth:`to_datetime` wrongly converts when ``arg`` is a ``np.datetime64`` object with unit of ``ps``. (:issue:`60341`)
+- Bug in Datetime-like arrays converting ``NaT`` to -(2**63) when casting to integer. Now it raises ``IntCastingNaNError`` (:issue:`59711`)
 - Bug in comparison between objects with ``np.datetime64`` dtype and ``timestamp[pyarrow]`` dtypes incorrectly raising ``TypeError`` (:issue:`60937`)
 - Bug in comparison between objects with pyarrow date dtype and ``timestamp[pyarrow]`` or ``np.datetime64`` dtype failing to consider these as non-comparable (:issue:`62157`)
 - Bug in constructing arrays with :class:`ArrowDtype` with ``timestamp`` type incorrectly allowing ``Decimal("NaN")`` (:issue:`61773`)

pandas/core/arrays/datetimelike.py

@@ -87,6 +87,7 @@
 )
 from pandas.util._exceptions import find_stack_level
 
+from pandas.core.dtypes.astype import check_to_int_nansafe
 from pandas.core.dtypes.cast import construct_1d_object_array_from_listlike
 from pandas.core.dtypes.common import (
     is_all_strings,
@@ -490,6 +491,7 @@ def astype(self, dtype, copy: bool = True):
         elif dtype.kind in "iu":
             # we deliberately ignore int32 vs. int64 here.
             # See https://github.com/pandas-dev/pandas/issues/24381 for more.
+            check_to_int_nansafe(self, infinite_check=False)
             values = self.asi8
             if dtype != np.int64:
                 raise TypeError(

pandas/core/dtypes/astype.py

@@ -27,6 +27,7 @@
     ExtensionDtype,
     NumpyEADtype,
 )
+from pandas.core.dtypes.missing import isna
 
 if TYPE_CHECKING:
     from pandas._typing import (
@@ -138,10 +139,7 @@ def _astype_float_to_int_nansafe(
     """
     astype with a check preventing converting NaN to an meaningless integer value.
     """
-    if not np.isfinite(values).all():
-        raise IntCastingNaNError(
-            "Cannot convert non-finite values (NA or inf) to integer"
-        )
+    check_to_int_nansafe(values)
     if dtype.kind == "u":
         # GH#45151
         if not (values >= 0).all():
@@ -151,6 +149,34 @@ def _astype_float_to_int_nansafe(
         return values.astype(dtype, copy=copy)
 
 
+def check_to_int_nansafe(values: np.ndarray, infinite_check: bool = True):
+    """
+    Validate that values can be safely converted to integer type.
+
+    Parameters
+    ----------
+    values : np.ndarray
+        Array of values to check for conversion to integer.
+    infinite_check : bool
+        If True, check for both infinite and missing values.
+        If False, check only for missing values.
+        This distinction exists
+        because ``np.isfinite`` isn't compatible with ``np.ufunc``.
+
+    Raises
+    ------
+    IntCastingNaNError
+        If any non-finite value is detected.
+    """
+    error_msg = "Cannot convert non-finite values (NA or inf) to integer"
+    if infinite_check:
+        if not np.isfinite(values).all():
+            raise IntCastingNaNError(error_msg)
+    else:
+        if isna(values).any():
+            raise IntCastingNaNError(error_msg)
+
+
 def astype_array(values: ArrayLike, dtype: DtypeObj, copy: bool = False) -> ArrayLike:
     """
     Cast array (ndarray or ExtensionArray) to the new dtype.

pandas/tests/series/methods/test_astype.py

@@ -389,6 +389,15 @@ def test_astype_cast_nan_inf_int(self, any_int_numpy_dtype, value):
         with pytest.raises(ValueError, match=msg):
             ser.astype(any_int_numpy_dtype)
 
+    @pytest.mark.parametrize("dtype", tm.DATETIME64_DTYPES + tm.TIMEDELTA64_DTYPES)
+    def test_int_cast_raises_with_datetime(self, dtype):
+        # GH 59711
+        ser = Series([np.nan], dtype=dtype)
+
+        msg = r"Cannot convert non-finite values \(NA or inf\) to integer"
+        with pytest.raises(ValueError, match=msg):
+            ser.astype(int)
+
     def test_astype_cast_object_int_fail(self, any_int_numpy_dtype):
         arr = Series(["car", "house", "tree", "1"])
         msg = r"invalid literal for int\(\) with base 10: 'car'"