COMPAT: Fix numpy 2.1 timedelta * DateOffset (#59441)

Author: mroeschke

pandas/core/arrays/timedeltas.py

@@ -467,6 +467,10 @@ def __mul__(self, other) -> Self:
         if is_scalar(other):
             # numpy will accept float and int, raise TypeError for others
             result = self._ndarray * other
+            if result.dtype.kind != "m":
+                # numpy >= 2.1 may not raise a TypeError
+                # and seems to dispatch to others.__rmul__?
+                raise TypeError(f"Cannot multiply with {type(other).__name__}")
             freq = None
             if self.freq is not None and not isna(other):
                 freq = self.freq * other
@@ -494,6 +498,10 @@ def __mul__(self, other) -> Self:
 
         # numpy will accept float or int dtype, raise TypeError for others
         result = self._ndarray * other
+        if result.dtype.kind != "m":
+            # numpy >= 2.1 may not raise a TypeError
+            # and seems to dispatch to others.__rmul__?
+            raise TypeError(f"Cannot multiply with {type(other).__name__}")
         return type(self)._simple_new(result, dtype=result.dtype)
 
     __rmul__ = __mul__

pandas/tests/arithmetic/test_timedelta64.py

@@ -1460,7 +1460,13 @@ def test_td64arr_mul_int(self, box_with_array):
     def test_td64arr_mul_tdlike_scalar_raises(self, two_hours, box_with_array):
         rng = timedelta_range("1 days", "10 days", name="foo")
         rng = tm.box_expected(rng, box_with_array)
-        msg = "argument must be an integer|cannot use operands with types dtype"
+        msg = "|".join(
+            [
+                "argument must be an integer",
+                "cannot use operands with types dtype",
+                "Cannot multiply with",
+            ]
+        )
         with pytest.raises(TypeError, match=msg):
             rng * two_hours