BUG: Fix ArrayLike(NDArrayOperatorsMixin) operations with object()

1 files changed, 20 insertions, 6 deletions

diff --git a/numpy/lib/tests/test_mixins.py b/numpy/lib/tests/test_mixins.py
index f45a3c661..bca974fc5 100644
--- a/numpy/lib/tests/test_mixins.py
+++ b/numpy/lib/tests/test_mixins.py
@@ -26,18 +26,23 @@ class ArrayLike(np.lib.mixins.NDArrayOperatorsMixin):
     def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
         out = kwargs.get('out', ())
         for x in inputs + out:
-            # Only support operations with instances of _HANDLED_TYPES
-            # and superclass instances of this type
+            # Only support operations with instances of _HANDLED_TYPES,
+            # or instances of ArrayLike that are superclasses of this
+            # object's type.
             if not (isinstance(x, self._HANDLED_TYPES) or
-                    isinstance(self, type(x))):
+                    (isinstance(x, ArrayLike) and
+                     isinstance(self, type(x)))):
                 return NotImplemented
 
-        # Defer to the implementation of the ufunc on unwrapped values
-        inputs = tuple(x.value if isinstance(self, type(x)) else x
+        # Defer to the implementation of the ufunc on unwrapped values.
+        # Use ArrayLike instead of type(self) for isinstance to allow
+        # subclasses that don't override __array_ufunc__ to handle
+        # ArrayLike objects.
+        inputs = tuple(x.value if isinstance(x, ArrayLike) else x
                        for x in inputs)
         if out:
             kwargs['out'] = tuple(
-                x.value if isinstance(self, type(x)) else x
+                x.value if isinstance(x, ArrayLike) else x
                 for x in out)
         result = getattr(ufunc, method)(*inputs, **kwargs)
 
@@ -128,6 +133,15 @@ class TestNDArrayOperatorsMixin(TestCase):
         _assert_equal_type_and_value(x + y, y)
         _assert_equal_type_and_value(y + x, y)
 
+    def test_object(self):
+        x = ArrayLike(0)
+        obj = object()
+        assert_equal(x.__add__(obj), NotImplemented)
+        with assert_raises(TypeError):
+            x + obj
+        with assert_raises(TypeError):
+            obj + x
+
     def test_unary_methods(self):
         array = np.array([-1, 0, 1, 2])
         array_like = ArrayLike(array)