added test for legacy unions

Author: randolf-scholz

Lib/test/test_patma.py

@@ -3402,16 +3402,28 @@ def test_class_pattern_not_type(self):
         self.assertIsNone(w)
 
     def test_class_or_union_not_specialform(self):
-        w = None
         from typing import Literal
         name = type(Literal).__name__
-        msg = rf"called match pattern must be a class or a union \(got {name}\)"
+        msg = rf"called match pattern must be a class or types.UnionType \(got {name}\)"
+        w = None
         with self.assertRaisesRegex(TypeError, msg):
             match 1:
                 case Literal():
                     w = 0
         self.assertIsNone(w)
 
+    def test_patma_legacy_union_type(self):
+        from typing import Union
+        IntOrStr = Union[int, str]
+        name = type(IntOrStr).__name__
+        msg = rf"called match pattern must be a class or types.UnionType \(got {name}\)"
+        w = None
+        with self.assertRaisesRegex(TypeError, msg):
+            match 1:
+                case IntOrStr():
+                    w = 0
+        self.assertIsNone(w)
+
     def test_regular_protocol(self):
         from typing import Protocol
         class P(Protocol): ...

Misc/NEWS.d/next/Core and Builtins/2024-05-02-20-16-12.gh-issue-118524.B4rIYi.rst

@@ -1 +1 @@
-Since Python 3.10, it was possible to use unions as the second argument to ``isinstance``. Now, unions can also be used as match patterns.
+Since Python 3.10, it was possible to use unions as the second argument to ``isinstance``. Now, PEP604 style unions can also be used as match patterns.

Python/ceval.c

@@ -476,7 +476,7 @@ _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)";
+        const char *e = "called match pattern must be a class or types.UnionType (got %s)";
         _PyErr_Format(tstate, PyExc_TypeError, e, Py_TYPE(type)->tp_name);
         return NULL;
     }