make Inherited builder give by reference

Author: nikomatsakis

src/librustc_typeck/check/mod.rs

@@ -613,10 +613,10 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
 impl<'a, 'gcx> InheritedBuilder<'a, 'gcx> {
     fn enter<'tcx, R>(
         &'tcx mut self,
-        f: impl FnOnce(Inherited<'_, 'gcx, 'tcx>) -> R,
+        f: impl FnOnce(&Inherited<'_, 'gcx, 'tcx>) -> R,
     ) -> R {
         let def_id = self.def_id;
-        self.infcx.enter(|infcx| f(Inherited::new(infcx, def_id)))
+        self.infcx.enter(|infcx| f(&Inherited::new(infcx, def_id)))
     }
 }
 

src/librustc_typeck/check/wfcheck.rs

@@ -55,7 +55,7 @@ impl<'a, 'gcx> CheckWfFcxBuilder<'a, 'gcx> {
         let span = self.span;
         let param_env = self.param_env;
         self.inherited.enter(|inh| {
-            let fcx = FnCtxt::new(&inh, param_env, id);
+            let fcx = FnCtxt::new(inh, param_env, id);
             let wf_tys = f(&fcx, &mut CheckTypeWellFormedVisitor {
                 tcx: fcx.tcx.global_tcx(),
                 code,