add a global evaluation cache

Author: Ariel Ben-Yehuda

src/librustc/middle/traits/select.rs

@@ -659,7 +659,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     }
 
     fn pick_evaluation_cache(&self) -> &EvaluationCache<'tcx> {
-        &self.param_env().evaluation_cache
+        // see comment in `pick_candidate_cache`
+        if self.intercrate ||
+            !self.param_env().caller_bounds.is_empty()
+        {
+            &self.param_env().evaluation_cache
+        } else
+        {
+            &self.tcx().evaluation_cache
+        }
     }
 
     fn check_evaluation_cache(&self, trait_ref: ty::PolyTraitRef<'tcx>)

src/librustc/middle/ty/context.rs

@@ -332,6 +332,11 @@ pub struct ctxt<'tcx> {
     /// for things that do not have to do with the parameters in scope.
     pub selection_cache: traits::SelectionCache<'tcx>,
 
+    /// Caches the results of trait evaluation. This cache is used
+    /// for things that do not have to do with the parameters in scope.
+    /// Merge this with `selection_cache`?
+    pub evaluation_cache: traits::EvaluationCache<'tcx>,
+
     /// A set of predicates that have been fulfilled *somewhere*.
     /// This is used to avoid duplicate work. Predicates are only
     /// added to this set when they mention only "global" names
@@ -512,6 +517,7 @@ impl<'tcx> ctxt<'tcx> {
             transmute_restrictions: RefCell::new(Vec::new()),
             stability: RefCell::new(stability),
             selection_cache: traits::SelectionCache::new(),
+            evaluation_cache: traits::EvaluationCache::new(),
             repr_hint_cache: RefCell::new(DefIdMap()),
             const_qualif_map: RefCell::new(NodeMap()),
             custom_coerce_unsized_kinds: RefCell::new(DefIdMap()),