redundant_pattern_matching: parenthesize guarded matches! suggestion

[shulaoda]

The suggestion for a guarded matches!(x, Pat if guard) was built as x.is_some() && guard but never wrapped in parentheses, so applying it where the matches!(...) binds tighter than && (!matches!(...), matches!(...) == false, a method receiver, an as cast, ...) changed operator precedence. That either silently changed the program's behavior or broke compilation.

The fix wraps the whole is_xxx() && guard suggestion in parentheses when the parent expression binds tighter than &&, and leaves it untouched otherwise (statements, if/while conditions, arguments, &&/|| operands).

Fixes #17286

changelog: [redundant_pattern_matching]: parenthesize the suggestion for a guarded matches! so the autofix keeps the original operator precedence

[rustbot]

r? @dswij

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