[3.12] gh-123048: Fix missing source location in pattern matching code (GH-123167)

Lib/test/test_patma.py

@@ -1,6 +1,7 @@
 import array
 import collections
 import dataclasses
+import dis
 import enum
 import inspect
 import sys
@@ -3083,6 +3084,24 @@ class Keys:
         self.assertIs(y, None)
         self.assertIs(z, None)
 
+class TestSourceLocations(unittest.TestCase):
+    def test_jump_threading(self):
+        # See gh-123048
+        def f():
+            x = 0
+            v = 1
+            match v:
+                case 1:
+                    if x < 0:
+                        x = 1
+                case 2:
+                    if x < 0:
+                        x = 1
+            x += 1
+
+        for inst in dis.get_instructions(f):
+            if inst.opcode in dis.hasjrel or inst.opcode in dis.hasjabs:
+                self.assertIsNotNone(inst.positions.lineno, "jump without location")
 
 class TestTracing(unittest.TestCase):
 

Misc/NEWS.d/next/Core and Builtins/2024-08-20-11-09-16.gh-issue-123048.2TISpv.rst

@@ -0,0 +1,2 @@
+Fix a bug where pattern matching code could emit a :opcode:`JUMP_FORWARD`
+with no source location.