remove the SimplifiedType from the DepNode for now, just to keep

size of `DepNode` smaller and because we are not that fine-grained yet
anyhow

src/librustc/dep_graph/mod.rs

@@ -11,7 +11,6 @@
 use self::thread::{DepGraphThreadData, DepMessage};
 use middle::def_id::DefId;
 use middle::ty;
-use middle::ty::fast_reject::SimplifiedType;
 use rustc_front::hir;
 use rustc_front::intravisit::Visitor;
 use std::rc::Rc;
@@ -102,7 +101,7 @@ pub enum DepNode {
     // which would yield an overly conservative dep-graph.
     TraitItems(DefId),
     ReprHints(DefId),
-    TraitSelect(DefId, Option<SimplifiedType>),
+    TraitSelect(DefId),
 }
 
 #[derive(Clone)]

src/librustc/middle/traits/mod.rs

@@ -20,7 +20,6 @@ use middle::def_id::DefId;
 use middle::free_region::FreeRegionMap;
 use middle::subst;
 use middle::ty::{self, Ty, TypeFoldable};
-use middle::ty::fast_reject;
 use middle::infer::{self, fixup_err_to_string, InferCtxt};
 
 use std::rc::Rc;
@@ -618,15 +617,8 @@ impl<'tcx> FulfillmentError<'tcx> {
 
 impl<'tcx> TraitObligation<'tcx> {
     /// Creates the dep-node for selecting/evaluating this trait reference.
-    fn dep_node(&self, tcx: &ty::ctxt<'tcx>) -> DepNode {
-        let simplified_ty =
-            fast_reject::simplify_type(tcx,
-                                       self.predicate.skip_binder().self_ty(), // (*)
-                                       true);
-
-        // (*) skip_binder is ok because `simplify_type` doesn't care about regions
-
-        DepNode::TraitSelect(self.predicate.def_id(), simplified_ty)
+    fn dep_node(&self) -> DepNode {
+        DepNode::TraitSelect(self.predicate.def_id())
     }
 
     fn self_ty(&self) -> ty::Binder<Ty<'tcx>> {

src/librustc/middle/traits/select.rs

@@ -307,7 +307,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         debug!("select({:?})", obligation);
         assert!(!obligation.predicate.has_escaping_regions());
 
-        let dep_node = obligation.dep_node(self.tcx());
+        let dep_node = obligation.dep_node();
         let _task = self.tcx().dep_graph.in_task(dep_node);
 
         let stack = self.push_stack(TraitObligationStackList::empty(), obligation);