C is fun PT2 (ignore this)

Author: Gobot1234

Include/internal/pycore_global_objects_fini_generated.h

@@ -93,6 +93,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(__contains__)
         STRUCT_FOR_ID(__copy__)
         STRUCT_FOR_ID(__ctypes_from_outparam__)
+        STRUCT_FOR_ID(__default__)
         STRUCT_FOR_ID(__del__)
         STRUCT_FOR_ID(__delattr__)
         STRUCT_FOR_ID(__delete__)

Include/internal/pycore_global_strings.h

@@ -828,6 +828,14 @@ def test_union_parameter_chaining(self):
         self.assertEqual((list[T] | list[S])[int, T], list[int] | list[T])
         self.assertEqual((list[T] | list[S])[int, int], list[int])
 
+    def test_union_parameter_default_ordering(self):
+        T = typing.TypeVar("T")
+        U = typing.TypeVar("U", default=int)
+
+        self.assertEqual((list[U] | list[T]).__parameters__, (U, T))
+        with self.assertRaises(TypeError):
+            list[U] | list[T]
+
     def test_union_parameter_substitution(self):
         def eq(actual, expected, typed=True):
             self.assertEqual(actual, expected)
@@ -967,6 +975,18 @@ def __eq__(self, other):
                 with self.assertRaises(TypeError):
                     issubclass(int, type_)
 
+    def test_generic_alias_subclass_with_defaults(self):
+        T = typing.TypeVar("T")
+        U = typing.TypeVar("U", default=int)
+        class MyGeneric:
+            __class_getitem__ = classmethod(types.GenericAlias)
+
+        class Fine(MyGeneric[T, U]):
+            ...
+
+        with self.assertRaises(TypeError):
+            class NonDefaultFollows(MyGeneric[U, T]): ...
+
     def test_or_type_operator_with_bad_module(self):
         class BadMeta(type):
             __qualname__ = 'TypeVar'

Include/internal/pycore_runtime_init_generated.h

@@ -214,9 +214,11 @@ _Py_make_parameters(PyObject *args)
     if (parameters == NULL)
         return NULL;
     Py_ssize_t iparam = 0;
+    bool seen_default = false;
     for (Py_ssize_t iarg = 0; iarg < nargs; iarg++) {
         PyObject *t = PyTuple_GET_ITEM(args, iarg);
         PyObject *subst;
+
         // We don't want __parameters__ descriptor of a bare Python class.
         if (PyType_Check(t)) {
             continue;
@@ -225,7 +227,28 @@ _Py_make_parameters(PyObject *args)
             Py_DECREF(parameters);
             return NULL;
         }
+        printf("Here\n");
         if (subst) {
+            printf("subst checking contains\n");
+            PyObject_Print(t, stdout, 0);
+            PyObject_Print(parameters, stdout, 0);
+            PyObject *default_;
+            bool does_not_contain = tuple_index(parameters, nargs, t) == -1;
+            if (does_not_contain) {
+                if (_PyObject_LookupAttr(t, &_Py_ID(__default__), &default_) < 0) {
+                    Py_DECREF(default_);
+                    Py_DECREF(subst);
+                    return NULL;
+                }
+                PyObject_Print(default_, stdout, 0);
+                if (default_ && !!Py_IsNone(default_)) {
+                    seen_default = true;
+                } else if (seen_default) {
+                    PyErr_Format(PyExc_TypeError, "TypeVarLike without a default follows one with a default");
+                }
+                printf("\n%d seen default\n", seen_default);
+            }
+
             iparam += tuple_add(parameters, iparam, t);
             Py_DECREF(subst);
         }
@@ -248,7 +271,24 @@ _Py_make_parameters(PyObject *args)
                     }
                 }
                 for (Py_ssize_t j = 0; j < len2; j++) {
+                    PyObject *default_;
                     PyObject *t2 = PyTuple_GET_ITEM(subparams, j);
+
+                    bool does_not_contain = tuple_index(parameters, nargs, t) == -1;
+                    if (does_not_contain) {
+                        if (_PyObject_LookupAttr(t2, &_Py_ID(__default__), &default_) < 0) {
+                            Py_DECREF(default_);
+                            Py_DECREF(subst);
+                            return NULL;
+                        }
+                        PyObject_Print(default_, stdout, 0);
+                        printf("\n%d seen default\n", seen_default);
+                        if (default_ && !!Py_IsNone(default_)) {
+                            seen_default = true;
+                        } else if (seen_default) {
+                            PyErr_Format(PyExc_TypeError, "TypeVarLike without a default follows one with a default");
+                        }
+                    }
                     iparam += tuple_add(parameters, iparam, t2);
                 }
             }