rustc/ty: improve allocations

src/librustc/ty/outlives.rs

@@ -180,9 +180,5 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 }
 
 fn push_region_constraints<'tcx>(out: &mut Vec<Component<'tcx>>, regions: Vec<ty::Region<'tcx>>) {
-    for r in regions {
-        if !r.is_late_bound() {
-            out.push(Component::Region(r));
-        }
-    }
+    out.extend(regions.iter().filter(|&r| !r.is_late_bound()).map(|r| Component::Region(r)));
 }

src/librustc/ty/subst.rs

@@ -229,6 +229,7 @@ impl<'a, 'gcx, 'tcx> Substs<'tcx> {
                       mk_kind: &mut F)
     where F: FnMut(&ty::GenericParamDef, &[Kind<'tcx>]) -> Kind<'tcx>
     {
+        substs.reserve(defs.params.len());
         for param in &defs.params {
             let kind = mk_kind(param, substs);
             assert_eq!(param.index as usize, substs.len());

src/librustc/ty/wf.rs

@@ -493,6 +493,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
 
             let explicit_bound = region;
 
+            self.out.reserve(implicit_bounds.len());
             for implicit_bound in implicit_bounds {
                 let cause = self.cause(traits::ObjectTypeBound(ty, explicit_bound));
                 let outlives = ty::Binder::dummy(