Rollup merge of #127092 - compiler-errors:rtn-dots-redux, r=estebank

Change return-type-notation to use `(..)`

Aligns the syntax with the current wording of [RFC 3654](https://github.com/rust-lang/rfcs/pull/3654). Also implements rustfmt support (along with making a match exhaustive).

Tracking:
* https://github.com/rust-lang/rust/issues/109417

compiler/rustc_passes/src/hir_stats.rs

@@ -695,7 +695,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
     fn visit_generic_args(&mut self, g: &'v ast::GenericArgs) {
         record_variants!(
             (self, g, g, Id::None, ast, GenericArgs, GenericArgs),
-            [AngleBracketed, Parenthesized]
+            [AngleBracketed, Parenthesized, ParenthesizedElided]
         );
         ast_visit::walk_generic_args(self, g)
     }