RUF023: Sorting __match_args__ changes match semantics

[dosisod]

RUF023 should not sort __match_args__ because the order of __match_args__ affects which elements are matched against when using positional args in class patterns.

Take the following code example:

from dataclasses import dataclass

@dataclass
class UnaryExpr:
    __match_args__ = ("op", "lhs")

    op: str
    lhs: int


def is_minus_one(expr):
    match expr:
        case UnaryExpr("-", 1):
            return True

    return False


is_minus_one(UnaryExpr("-", 1))  # True
is_minus_one(UnaryExpr("+", 1))  # False

Ruff emits the following errors:

$ ruff --preview --select RUF023 file.py
file.py:6:22: RUF023 [*] `UnaryExpr.__match_args__` is not sorted

If you change __match_args__ to ("lhs", "op"), the semantics of the match statement changes, and now both is_minus_one calls return False.

[AlexWaygood]

Oof, I can't believe I forgot that this was how things worked. Thanks!