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

Reproduziere die Branch-Auflistung mit dem match-case-Beispiel und untersuche den sys.monitoring-Einstiegspunkt co_branches() sowie das durch PR 122564 eingeführte Verhalten. Vergleiche die gemeldeten Ziele für Case-Muster und -Bodies; abgeschlossen ist die Aufgabe, wenn Branches in Case-Blöcke nicht mehr auf die Positionen der Muster abgebildet werden oder fälschlicherweise den Anschein erwecken, den Gültigkeitsbereich zu verlassen.