New lint: `unnecessary_semicolon` (#14032)

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.

----

changelog: [`unnecessary_semicolon`]: new lint

1 files changed, 1 insertions, 1 deletions

diff --git a/clippy_lints/src/missing_inline.rs b/clippy_lints/src/missing_inline.rs
index 05aa425de9e..bba1b63be27 100644
--- a/clippy_lints/src/missing_inline.rs
+++ b/clippy_lints/src/missing_inline.rs
@@ -135,7 +135,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingInline {
             | hir::ItemKind::ForeignMod { .. }
             | hir::ItemKind::Impl { .. }
             | hir::ItemKind::Use(..) => {},
-        };
+        }
     }
 
     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {