Remove NAT_TYPES and silence warning

Author: spencerkclark

xarray/computation/nanops.py

@@ -29,7 +29,7 @@ def _maybe_null_out(result, axis, mask, min_count=1):
         dtype, fill_value = dtypes.maybe_promote(result.dtype)
         result = where(null_mask, fill_value, astype(result, dtype))
 
-    elif getattr(result, "dtype", None) not in dtypes.NAT_TYPES:
+    elif hasattr(result, "dtype") and result.dtype.kind not in "mM":
         null_mask = mask.size - duck_array_ops.sum(mask)
         result = where(null_mask < min_count, np.nan, result)
 

xarray/core/dtypes.py

@@ -108,9 +108,6 @@ def maybe_promote(dtype: T_dtype) -> tuple[T_dtype, Any]:
     return dtype_out, fill_value
 
 
-NAT_TYPES = {np.datetime64("NaT").dtype, np.timedelta64("NaT").dtype}
-
-
 def get_fill_value(dtype):
     """Return an appropriate fill value for this dtype.
 

xarray/tests/test_dtypes.py

@@ -123,12 +123,6 @@ def test_maybe_promote(kind, expected) -> None:
     assert str(actual[1]) == expected[1]
 
 
-def test_nat_types_membership() -> None:
-    assert np.datetime64("NaT").dtype in dtypes.NAT_TYPES
-    assert np.timedelta64("NaT").dtype in dtypes.NAT_TYPES
-    assert np.float64 not in dtypes.NAT_TYPES
-
-
 @pytest.mark.parametrize(
     ["dtype", "kinds", "xp", "expected"],
     (