bpo-42908: Mark cleanup code at end of try-except and with artificial (#24202)

* Mark bytecodes at end of try-except as artificial.

* Make sure that the CFG is consistent throughout optimiization. 

* Extend line-number propagation logic so that implicit returns after 'try-except' or 'with' have the correct line numbers.

* Update importlib

2 files changed, 41 insertions, 1 deletions

diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index 0383124..e342a14 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -1026,7 +1026,7 @@ expected_opinfo_jumpy = [
   Instruction(opname='POP_JUMP_IF_FALSE', opcode=114, arg=42, argval=42, argrepr='', offset=36, starts_line=None, is_jump_target=False),
   Instruction(opname='POP_TOP', opcode=1, arg=None, argval=None, argrepr='', offset=38, starts_line=8, is_jump_target=False),
   Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=52, argval=52, argrepr='', offset=40, starts_line=None, is_jump_target=False),
-  Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=8, argval=8, argrepr='', offset=42, starts_line=None, is_jump_target=True),
+  Instruction(opname='JUMP_ABSOLUTE', opcode=113, arg=8, argval=8, argrepr='', offset=42, starts_line=7, is_jump_target=True),
   Instruction(opname='LOAD_GLOBAL', opcode=116, arg=1, argval='print', argrepr='print', offset=44, starts_line=10, is_jump_target=True),
   Instruction(opname='LOAD_CONST', opcode=100, arg=4, argval='I can haz else clause?', argrepr="'I can haz else clause?'", offset=46, starts_line=None, is_jump_target=False),
   Instruction(opname='CALL_FUNCTION', opcode=131, arg=1, argval=1, argrepr='', offset=48, starts_line=None, is_jump_target=False),
diff --git a/Lib/test/test_sys_settrace.py b/Lib/test/test_sys_settrace.py
index 83b0392..4298986 100644
--- a/Lib/test/test_sys_settrace.py
+++ b/Lib/test/test_sys_settrace.py
@@ -916,6 +916,46 @@ class TraceTestCase(unittest.TestCase):
              (7, 'line'),
              (7, 'return')])
 
+    def test_if_false_in_with(self):
+
+        class C:
+            def __enter__(self):
+                return self
+            def __exit__(*args):
+                pass
+
+        def func():
+            with C():
+                if False:
+                    pass
+
+        self.run_and_compare(func,
+            [(0, 'call'),
+             (1, 'line'),
+             (-5, 'call'),
+             (-4, 'line'),
+             (-4, 'return'),
+             (2, 'line'),
+             (-3, 'call'),
+             (-2, 'line'),
+             (-2, 'return'),
+             (2, 'return')])
+
+    def test_if_false_in_try_except(self):
+
+        def func():
+            try:
+                if False:
+                    pass
+            except Exception:
+                X
+
+        self.run_and_compare(func,
+            [(0, 'call'),
+             (1, 'line'),
+             (2, 'line'),
+             (2, 'return')])
+
 
 class SkipLineEventsTraceTestCase(TraceTestCase):
     """Repeat the trace tests, but with per-line events skipped"""