MAINT: Allow subclasses in ndarray.__array_function__.

The Liskov substitution principle suggests it should.

1 files changed, 5 insertions, 11 deletions

diff --git a/numpy/core/overrides.py b/numpy/core/overrides.py
index 1cc1ff8d8..8bdbe1708 100644
--- a/numpy/core/overrides.py
+++ b/numpy/core/overrides.py
@@ -62,16 +62,6 @@ def get_overloaded_types_and_args(relevant_args):
                 overloaded_types = [arg_type]
                 overloaded_args = [arg]
 
-    # Short-cut for the common case of only ndarray.
-    if overloaded_types == _NDARRAY_ONLY:
-        return overloaded_types, []
-
-    # Special handling for ndarray.__array_function__
-    overloaded_args = [
-        arg for arg in overloaded_args
-        if type(arg).__array_function__ is not _NDARRAY_ARRAY_FUNCTION
-    ]
-
     return overloaded_types, overloaded_args
 
 
@@ -106,7 +96,11 @@ def array_function_implementation_or_override(
     """
     # Check for __array_function__ methods.
     types, overloaded_args = get_overloaded_types_and_args(relevant_args)
-    if not overloaded_args:
+    # Short-cut for common cases: no overload or only ndarray overload
+    # (directly or with subclasses that do not override __array_function__).
+    if (not overloaded_args or types == _NDARRAY_ONLY or
+            all(type(arg).__array_function__ is _NDARRAY_ARRAY_FUNCTION
+                for arg in overloaded_args)):
         return implementation(*args, **kwargs)
 
     # Call overrides