This lint detects and removes the unnecessary semicolon after a `match`
or `if` statement returning `()`. It seems to be quite a common
"mistake", given the number of hits (88) we had in the Clippy sources
themselves.
The lint doesn't bother about loops, as `rustfmt` already removes the
extra semicolon. It doesn't handle blocks either, as an extra block
level, followed or not by a semicolon, is likely intentional.
I propose to put the lint in `pedantic`, as putting it in `style` seems
quite hazardous given the number of hits.
Note: there exists a `redundant-semicolon` lint in the compiler, but it
is an early lint and cannot check that the expression evaluates to `()`,
so it ignores the cases we're handling here.
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changelog: [`unnecessary_semicolon`]: new lint
8f1b4bb87a