Warn for extra semicolon

[leonardo-m]

The closing semicolon of the match {} is not warned against by Rusts nor Clippy:

enum Foo { A, B }

fn bar(f: Foo) {
    match f {
        Foo::A => {},
        Foo::B => {},
    };
}

fn main() {
    bar(Foo::A);
    bar(Foo::B);
}

[killercup]

Not sure this is lint-worthy as it doesn't change the semantics of the code. Is it removed by rustfmt?

[leonardo-m]

Is it removed by rustfmt?

Currently rustfmt doesn't remove it.

Not sure this is lint-worthy as it doesn't change the semantics of the code.

From my experience when the code isn't clean, it could cause troubles for someone later. I prefer Rust code to be tidy, it causes less troubles.

[brunoczim]

I don't think this should be a rustc's lint. It is an insignificant syntactic detail. There are much worse things like lack of indentation. I don't think we should warn those things either. Maybe it could be a clippy's lint (of pedant category).

Currently, rustfmt cannot remove this extra semicolon because it requires semantical analysis and it only does syntactic analysis. We need to know if the type of the expression is ().

[leonardo-m]

If that's the consensus I'll move this issue to Clippy issues.

[estebank]

@leonardo-m closing and linking from similar clippy issue.