rustc_traits: deny(unused_lifetimes).

src/librustc_traits/chalk_context/mod.rs

@@ -575,7 +575,7 @@ impl ExClauseFold<'tcx> for ChalkArenas<'tcx> {
         }
     }
 
-    fn visit_ex_clause_with<'gcx: 'tcx, V: TypeVisitor<'tcx>>(
+    fn visit_ex_clause_with<V: TypeVisitor<'tcx>>(
         ex_clause: &ExClause<Self>,
         visitor: &mut V,
     ) -> bool {

src/librustc_traits/lib.rs

@@ -3,6 +3,7 @@
 
 #![deny(rust_2018_idioms)]
 #![deny(internal)]
+#![deny(unused_lifetimes)]
 
 #![feature(crate_visibility_modifier)]
 #![feature(in_band_lifetimes)]