Closes #22507: document that PyType_IsSubtype does not call __subclasscheck__.

diff --git a/Doc/c-api/type.rst b/Doc/c-api/type.rst
index 8dc040b8520196df6edd6c15bfbe89c980db5c33..343437d676d70ee03e0d28aed95e4e46b534cc67 100644 (file)
--- a/Doc/c-api/type.rst
+++ b/Doc/c-api/type.rst
@@ -44,6 +44,7 @@ Type Objects
 
    .. versionadded:: 3.2
 
+
 .. c:function:: void PyType_Modified(PyTypeObject *type)
 
    Invalidate the internal lookup cache for the type and all of its
@@ -67,6 +68,11 @@ Type Objects
 
    Return true if *a* is a subtype of *b*.
 
+   This function only checks for actual subtypes, which means that
+   :meth:`~type.__subclasscheck__` is not called on *b*.  Call
+   :c:func:`PyObject_IsSubclass` to do the same check that :func:`issubclass`
+   would do.
+
 
 .. c:function:: PyObject* PyType_GenericAlloc(PyTypeObject *type, Py_ssize_t nitems)