added test for class or union error message

Author: randolf-scholz

Lib/test/test_patma.py

@@ -3410,6 +3410,16 @@ def test_class_pattern_not_type(self):
                     w = 0
         self.assertIsNone(w)
 
+    def test_class_or_union_not_specialform(self):
+        w = None
+        from typing import Literal
+        msg = 'called match pattern must be a class or a union'
+        with self.assertRaisesRegex(TypeError, msg):
+            match 1:
+                case Literal():
+                    w = 0
+        self.assertIsNone(w)
+
     def test_regular_protocol(self):
         from typing import Protocol
         class P(Protocol): ...

Python/ceval.c

@@ -730,7 +730,7 @@ _PyEval_MatchClass(PyThreadState *tstate, PyObject *subject, PyObject *type,
     if (_PyUnion_Check(type)) {
         // get union members
         PyObject *members = _Py_union_args(type);
-        Py_ssize_t n = PyTuple_GET_SIZE(members);
+        const Py_ssize_t n = PyTuple_GET_SIZE(members);
 
         // iterate over union members and return first match
         for (Py_ssize_t i = 0; i < n; i++) {
@@ -745,8 +745,8 @@ _PyEval_MatchClass(PyThreadState *tstate, PyObject *subject, PyObject *type,
         return NULL;
     }
     if (!PyType_Check(type)) {
-        const char *e = "called match pattern must be a class or a union, (got %s, %s)";
-        _PyErr_Format(tstate, PyExc_TypeError, e, Py_TYPE(type)->tp_name, subject->ob_type->tp_name);
+        const char *e = "called match pattern must be a class or a union (got %s)";
+        _PyErr_Format(tstate, PyExc_TypeError, e, Py_TYPE(type)->tp_name);
         return NULL;
     }
     assert(PyTuple_CheckExact(kwargs));