bpo-42233: Add union type expression support for GenericAlias and fix de-duplicating of GenericAlias (GH-23077)

1 files changed, 15 insertions, 5 deletions

diff --git a/Objects/unionobject.c b/Objects/unionobject.c
index 1b7f8ab51a..2308bfc9f2 100644
--- a/Objects/unionobject.c
+++ b/Objects/unionobject.c
@@ -237,9 +237,19 @@ dedup_and_flatten_args(PyObject* args)
         PyObject* i_element = PyTuple_GET_ITEM(args, i);
         for (Py_ssize_t j = i + 1; j < arg_length; j++) {
             PyObject* j_element = PyTuple_GET_ITEM(args, j);
-            if (i_element == j_element) {
-                is_duplicate = 1;
+            int is_ga = Py_TYPE(i_element) == &Py_GenericAliasType &&
+                        Py_TYPE(j_element) == &Py_GenericAliasType;
+            // RichCompare to also deduplicate GenericAlias types (slower)
+            is_duplicate = is_ga ? PyObject_RichCompareBool(i_element, j_element, Py_EQ)
+                : i_element == j_element;
+            // Should only happen if RichCompare fails
+            if (is_duplicate < 0) {
+                Py_DECREF(args);
+                Py_DECREF(new_args);
+                return NULL;
             }
+            if (is_duplicate)
+                break;
         }
         if (!is_duplicate) {
             Py_INCREF(i_element);
@@ -290,8 +300,8 @@ is_unionable(PyObject *obj)
         type == &_Py_UnionType);
 }
 
-static PyObject *
-type_or(PyTypeObject* self, PyObject* param)
+PyObject *
+_Py_union_type_or(PyObject* self, PyObject* param)
 {
     PyObject *tuple = PyTuple_Pack(2, self, param);
     if (tuple == NULL) {
@@ -404,7 +414,7 @@ static PyMethodDef union_methods[] = {
         {0}};
 
 static PyNumberMethods union_as_number = {
-        .nb_or = (binaryfunc)type_or, // Add __or__ function
+        .nb_or = _Py_union_type_or, // Add __or__ function
 };
 
 PyTypeObject _Py_UnionType = {