Wrap vtable_methods return type in RC

src/librustc/traits/mod.rs

@@ -653,10 +653,11 @@ pub fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 pub fn vtable_methods<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     trait_ref: ty::PolyTraitRef<'tcx>)
-    -> Vec<Option<(DefId, &'tcx Substs<'tcx>)>>
+    -> Rc<Vec<Option<(DefId, &'tcx Substs<'tcx>)>>>
 {
     debug!("vtable_methods({:?})", trait_ref);
 
+    Rc::new(
         supertraits(tcx, trait_ref).flat_map(move |trait_ref| {
             let trait_methods = tcx.associated_items(trait_ref.def_id())
                 .filter(|item| item.kind == ty::AssociatedKind::Method);
@@ -697,6 +698,7 @@ pub fn vtable_methods<'a, 'tcx>(
                 Some((def_id, substs))
             })
         }).collect()
+    )
 }
 
 impl<'tcx,O> Obligation<'tcx,O> {

src/librustc/ty/maps/mod.rs

@@ -229,7 +229,7 @@ define_maps! { <'tcx>
     [] fn const_is_rvalue_promotable_to_static: ConstIsRvaluePromotableToStatic(DefId) -> bool,
     [] fn is_mir_available: IsMirAvailable(DefId) -> bool,
     [] fn vtable_methods: vtable_methods_node(ty::PolyTraitRef<'tcx>)
-                          -> Vec<Option<(DefId, &'tcx Substs<'tcx>)>>,
+                          -> Rc<Vec<Option<(DefId, &'tcx Substs<'tcx>)>>>,
 
     [] fn trans_fulfill_obligation: fulfill_obligation_dep_node(
         (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>)) -> Vtable<'tcx, ()>,

src/librustc_trans/collector.rs

@@ -850,7 +850,7 @@ fn create_trans_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
             // Walk all methods of the trait, including those of its supertraits
             let methods = tcx.vtable_methods(poly_trait_ref);
-            let methods = methods.into_iter().filter_map(|method| method)
+            let methods = methods.iter().cloned().filter_map(|method| method)
                 .map(|(def_id, substs)| ty::Instance::resolve(
                         tcx,
                         ty::ParamEnv::empty(traits::Reveal::All),

src/librustc_trans/meth.rs

@@ -86,7 +86,8 @@ pub fn get_vtable<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 
     if let Some(trait_ref) = trait_ref {
         let trait_ref = trait_ref.with_self_ty(tcx, ty);
-        let methods = tcx.vtable_methods(trait_ref).into_iter().map(|opt_mth| {
+        let methods = tcx.vtable_methods(trait_ref);
+        let methods = methods.iter().cloned().map(|opt_mth| {
             opt_mth.map_or(nullptr, |(def_id, substs)| {
                 callee::resolve_and_get_fn(ccx, def_id, substs)
             })