Use a TypedArena rather than an Arena for the backing storage of vari…

…ance analysis.

(The code was not using the main feature of Arena in the first place,
since all of the `alloc` calls were on the same type.

src/librustc_typeck/variance.rs

@@ -192,7 +192,7 @@ use self::VarianceTerm::*;
 use self::ParamKind::*;
 
 use arena;
-use arena::Arena;
+use arena::TypedArena;
 use middle::resolve_lifetime as rl;
 use middle::subst;
 use middle::subst::{ParamSpace, FnSpace, TypeSpace, SelfSpace, VecPerParamSpace};
@@ -210,7 +210,7 @@ use util::ppaux::Repr;
 
 pub fn infer_variance(tcx: &ty::ctxt) {
     let krate = tcx.map.krate();
-    let mut arena = arena::Arena::new();
+    let mut arena = arena::TypedArena::new();
     let terms_cx = determine_parameters_to_be_inferred(tcx, &mut arena, krate);
     let constraints_cx = add_constraints_from_crate(terms_cx, krate);
     solve_constraints(constraints_cx);
@@ -254,7 +254,7 @@ impl<'a> fmt::Debug for VarianceTerm<'a> {
 
 struct TermsContext<'a, 'tcx: 'a> {
     tcx: &'a ty::ctxt<'tcx>,
-    arena: &'a Arena,
+    arena: &'a TypedArena<VarianceTerm<'a>>,
 
     empty_variances: Rc<ty::ItemVariances>,
 
@@ -282,7 +282,7 @@ struct InferredInfo<'a> {
 }
 
 fn determine_parameters_to_be_inferred<'a, 'tcx>(tcx: &'a ty::ctxt<'tcx>,
-                                                 arena: &'a mut Arena,
+                                                 arena: &'a mut TypedArena<VarianceTerm<'a>>,
                                                  krate: &ast::Crate)
                                                  -> TermsContext<'a, 'tcx> {
     let mut terms_cx = TermsContext {
@@ -312,7 +312,7 @@ impl<'a, 'tcx> TermsContext<'a, 'tcx> {
                     index: uint,
                     param_id: ast::NodeId) {
         let inf_index = InferredIndex(self.inferred_infos.len());
-        let term = self.arena.alloc(|| InferredTerm(inf_index));
+        let term = self.arena.alloc(InferredTerm(inf_index));
         self.inferred_infos.push(InferredInfo { item_id: item_id,
                                                 kind: kind,
                                                 space: space,
@@ -455,10 +455,10 @@ fn add_constraints_from_crate<'a, 'tcx>(terms_cx: TermsContext<'a, 'tcx>,
 
     let unsafe_lang_item = terms_cx.tcx.lang_items.unsafe_type();
 
-    let covariant = terms_cx.arena.alloc(|| ConstantTerm(ty::Covariant));
-    let contravariant = terms_cx.arena.alloc(|| ConstantTerm(ty::Contravariant));
-    let invariant = terms_cx.arena.alloc(|| ConstantTerm(ty::Invariant));
-    let bivariant = terms_cx.arena.alloc(|| ConstantTerm(ty::Bivariant));
+    let covariant = terms_cx.arena.alloc(ConstantTerm(ty::Covariant));
+    let contravariant = terms_cx.arena.alloc(ConstantTerm(ty::Contravariant));
+    let invariant = terms_cx.arena.alloc(ConstantTerm(ty::Invariant));
+    let bivariant = terms_cx.arena.alloc(ConstantTerm(ty::Bivariant));
     let mut constraint_cx = ConstraintContext {
         terms_cx: terms_cx,
 
@@ -719,7 +719,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             }
 
             _ => {
-                &*self.terms_cx.arena.alloc(|| TransformTerm(v1, v2))
+                &*self.terms_cx.arena.alloc(TransformTerm(v1, v2))
             }
         }
     }