Avoid double lowering of lifetime identifiers.

`LoweringContext::new_named_lifetime` lowers the `ident` passed in. Both
of its call sites *also* lower `ident` *before* passing it in. I.e. both
call sites cause the ident to be lowered twice. This commit removes the
lowering at the two call sites, so the ident is only lowered once.

Author: nnethercote

compiler/rustc_ast_lowering/src/item.rs

@@ -1757,7 +1757,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 })
             }
             GenericParamKind::Lifetime => {
-                let ident = self.lower_ident(ident);
                 let lt_id = self.next_node_id();
                 let lifetime = self.new_named_lifetime(id, lt_id, ident);
                 hir::WherePredicateKind::RegionPredicate(hir::WhereRegionPredicate {

compiler/rustc_ast_lowering/src/lib.rs

@@ -1769,8 +1769,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     }
 
     fn lower_lifetime(&mut self, l: &Lifetime) -> &'hir hir::Lifetime {
-        let ident = self.lower_ident(l.ident);
-        self.new_named_lifetime(l.id, l.id, ident)
+        self.new_named_lifetime(l.id, l.id, l.ident)
     }
 
     #[instrument(level = "debug", skip(self))]