Add [unary_parenthesis_followed_by_cast]

[KisaragiEffective]

check list:

• Followed [lint naming conventions][lint_naming]
• Added passing UI tests (including committed .stderr file)
• cargo test passes locally
• Executed cargo dev update_lints
• Added lint documentation
• Run cargo dev fmt

unresolved questions:

• should this lint fire not only local variables, but also do other unary (such as literals) expressions?

close #10557.

Please write a short comment explaining your change (or "none" for internal only changes)

changelog: Add [unary_parenthesis_followed_by_cast]

[rustbot]

r? @llogiq

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[KisaragiEffective]

(force-pushed due to lack of my GPG signature)

[llogiq]

I'm curious why the unused_parens lint doesn't catch this. (x) is just parenthesized x, if one wants to build a 1-tuple, the correct syntax is (x,).

[KisaragiEffective]

@llogiq It seems current implementation doesn't handle ExprKind::Cast. Should I submit another PR (to solve the issue) on rustc?

[llogiq]

Yeah, fixing the false negative in rustc is a better solution. You can keep this PR open in case the other one doesn't go through.

[KisaragiEffective]

submitted rust-lang/rust#110189, I'm going to close this.