sys.monitoring branches for `match` cases showing incorrectly

Bug report

Bug description:

With the code from PR 122564, the destinations of branches into the blocks of certain cases are mapping to the pattern as well, making them look like they go out of scope:

v = 1
match v:
    case 1:
        x = 1
    case 2:
        x = 2
    case 3:
        x = 3
x += 2

This code yields (branches listing below extracted from co_branches()):

  0          0       RESUME                   0

  1          2       LOAD_CONST               0 (1)
             4       STORE_NAME               0 (v)

  2          6       LOAD_NAME                0 (v)

  3          8       COPY                     1
            10       LOAD_CONST               0 (1)
            12       COMPARE_OP              88 (bool(==))
            16       POP_JUMP_IF_FALSE        5 (to L1)
            20       NOT_TAKEN
            22       POP_TOP

  4         24       LOAD_CONST               0 (1)
            26       STORE_NAME               1 (x)
            28       JUMP_FORWARD            19 (to L3)

  5   L1:   30       COPY                     1
            32       LOAD_CONST               1 (2)
            34       COMPARE_OP              88 (bool(==))
            38       POP_JUMP_IF_FALSE        5 (to L2)
            42       NOT_TAKEN
            44       POP_TOP

  6         46       LOAD_CONST               1 (2)
            48       STORE_NAME               1 (x)
            50       JUMP_FORWARD             8 (to L3)

  7   L2:   52       LOAD_CONST               2 (3)
            54       COMPARE_OP              88 (bool(==))
            58       POP_JUMP_IF_FALSE        3 (to L3)
            62       NOT_TAKEN

  8         64       LOAD_CONST               2 (3)
            66       STORE_NAME               1 (x)

  9   L3:   68       LOAD_NAME                1 (x)
            70       LOAD_CONST               1 (2)
            72       BINARY_OP               13 (+=)
            76       STORE_NAME               1 (x)
            78       RETURN_CONST             3 (None)
'<module>' branches:
    ex8.py 3:9-3:10 "1" (<module>@16) -> 3:9-3:10 "1" (<module>@22) [case -> out]
    ex8.py 3:9-3:10 "1" (<module>@16) -> 5:9-5:10 "2" (<module>@30) [case -> next case]
    ex8.py 5:9-5:10 "2" (<module>@38) -> 5:9-5:10 "2" (<module>@44) [case -> out]
    ex8.py 5:9-5:10 "2" (<module>@38) -> 7:9-7:10 "3" (<module>@52) [case -> next case]
    ex8.py 7:9-7:10 "3" (<module>@58) -> 8:12-8:13 "3" (<module>@64) [case -> body]
    ex8.py 7:9-7:10 "3" (<module>@58) -> 9:0-9:1 "x" (<module>@68) [case -> next]

@markshannon @nedbat

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-130627

Reproduire la liste des branches avec l’exemple de match-case et inspecter le point d’entrée co_branches() de sys.monitoring, ainsi que le comportement introduit par PR 122564. Comparer les destinations signalées pour les motifs et les corps des cases ; c’est terminé lorsque les branches vers les blocs case ne correspondent plus aux emplacements des motifs et ne semblent plus quitter la portée de manière incorrecte.