simplify DepNode for trait selection

Author: nikomatsakis

src/librustc/dep_graph/dep_node.rs

@@ -132,7 +132,7 @@ pub enum DepNode<D: Clone + Debug> {
     // which would yield an overly conservative dep-graph.
     TraitItems(D),
     ReprHints(D),
-    TraitSelect(D, Vec<D>),
+    TraitSelect(Vec<D>),
 }
 
 impl<D: Clone + Debug> DepNode<D> {
@@ -237,10 +237,9 @@ impl<D: Clone + Debug> DepNode<D> {
             TraitImpls(ref d) => op(d).map(TraitImpls),
             TraitItems(ref d) => op(d).map(TraitItems),
             ReprHints(ref d) => op(d).map(ReprHints),
-            TraitSelect(ref d, ref type_ds) => {
-                let d = try_opt!(op(d));
+            TraitSelect(ref type_ds) => {
                 let type_ds = try_opt!(type_ds.iter().map(|d| op(d)).collect());
-                Some(TraitSelect(d, type_ds))
+                Some(TraitSelect(type_ds))
             }
         }
     }

src/librustc/infer/mod.rs

@@ -670,6 +670,15 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
     }
 
+    /// Finishes processes any obligations that remain in the
+    /// fulfillment context, and then returns the result with all type
+    /// variables removed and regions erased. Because this is intended
+    /// for use after type-check has completed, if any errors occur,
+    /// it will panic. It is used during normalization and other cases
+    /// where processing the obligations in `fulfill_cx` may cause
+    /// type inference variables that appear in `result` to be
+    /// unified, and hence we need to process those obligations to get
+    /// the complete picture of the type.
     pub fn drain_fulfillment_cx_or_panic<T>(&self,
                                             span: Span,
                                             fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
@@ -679,47 +688,28 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     {
         debug!("drain_fulfillment_cx_or_panic()");
 
-        let when = "resolving bounds after type-checking";
-        let v = match self.drain_fulfillment_cx(fulfill_cx, result) {
-            Ok(v) => v,
+        // In principle, we only need to do this so long as `result`
+        // contains unbound type parameters. It could be a slight
+        // optimization to stop iterating early.
+        match fulfill_cx.select_all_or_error(self) {
+            Ok(()) => { }
             Err(errors) => {
-                span_bug!(span, "Encountered errors `{:?}` {}", errors, when);
+                span_bug!(span, "Encountered errors `{:?}` resolving bounds after type-checking",
+                          errors);
             }
-        };
+        }
 
-        match self.tcx.lift_to_global(&v) {
-            Some(v) => v,
+        let result = self.resolve_type_vars_if_possible(result);
+        let result = self.tcx.erase_regions(&result);
+
+        match self.tcx.lift_to_global(&result) {
+            Some(result) => result,
             None => {
-                span_bug!(span, "Uninferred types/regions in `{:?}` {}", v, when);
+                span_bug!(span, "Uninferred types/regions in `{:?}`", result);
             }
         }
     }
 
-    /// Finishes processes any obligations that remain in the fulfillment
-    /// context, and then "freshens" and returns `result`. This is
-    /// primarily used during normalization and other cases where
-    /// processing the obligations in `fulfill_cx` may cause type
-    /// inference variables that appear in `result` to be unified, and
-    /// hence we need to process those obligations to get the complete
-    /// picture of the type.
-    pub fn drain_fulfillment_cx<T>(&self,
-                                   fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
-                                   result: &T)
-                                   -> Result<T,Vec<traits::FulfillmentError<'tcx>>>
-        where T : TypeFoldable<'tcx>
-    {
-        debug!("drain_fulfillment_cx(result={:?})",
-               result);
-
-        // In principle, we only need to do this so long as `result`
-        // contains unbound type parameters. It could be a slight
-        // optimization to stop iterating early.
-        fulfill_cx.select_all_or_error(self)?;
-
-        let result = self.resolve_type_vars_if_possible(result);
-        Ok(self.tcx.erase_regions(&result))
-    }
-
     pub fn projection_mode(&self) -> Reveal {
         self.projection_mode
     }

src/librustc/ty/mod.rs

@@ -958,8 +958,9 @@ impl<'tcx> TraitPredicate<'tcx> {
                     _ =>
                         None
                 })
+                .chain(iter::once(self.def_id()))
                 .collect();
-        DepNode::TraitSelect(self.def_id(), def_ids)
+        DepNode::TraitSelect(def_ids)
     }
 
     pub fn input_types<'a>(&'a self) -> impl DoubleEndedIterator<Item=Ty<'tcx>> + 'a {

src/librustc_trans/common.rs

@@ -1028,7 +1028,7 @@ pub fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             fulfill_cx.register_predicate_obligation(&infcx, obligation);
         }
 
-        fulfill_cx.select_all_or_error(infcx).is_ok()
+        fulfill_cx.select_all_or_error(&infcx).is_ok()
     })
 }
 

src/librustc_trans/monomorphize.rs

@@ -48,7 +48,11 @@ pub fn apply_param_substs<'a, 'tcx, T>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                        -> T
     where T: TransNormalize<'tcx>
 {
+    debug!("apply_param_substs(param_substs={:?}, value={:?})", param_substs, value);
     let substituted = value.subst(tcx, param_substs);
+    debug!("apply_param_substs: substituted={:?}{}",
+           substituted,
+           if substituted.has_projection_types() { " [needs projection]" } else { "" });
     tcx.normalize_associated_type(&substituted)
 }