Refactor object-safety test to use def-ids only

Author: nikomatsakis

src/librustc/middle/traits/mod.rs

@@ -48,6 +48,8 @@ pub use self::util::get_vtable_index_of_object_method;
 pub use self::util::trait_ref_for_builtin_bound;
 pub use self::util::supertraits;
 pub use self::util::Supertraits;
+pub use self::util::supertrait_def_ids;
+pub use self::util::SupertraitDefIds;
 pub use self::util::transitive_bounds;
 pub use self::util::upcast;
 
@@ -640,7 +642,7 @@ impl<'tcx> FulfillmentError<'tcx> {
 }
 
 impl<'tcx> TraitObligation<'tcx> {
-    fn self_ty(&self) -> Ty<'tcx> {
-        self.predicate.0.self_ty()
+    fn self_ty(&self) -> ty::Binder<Ty<'tcx>> {
+        ty::Binder(self.predicate.skip_binder().self_ty())
     }
 }

src/librustc/middle/traits/object_safety.rs

@@ -53,36 +53,36 @@ pub enum MethodViolationCode {
 }
 
 pub fn is_object_safe<'tcx>(tcx: &ty::ctxt<'tcx>,
-                            trait_ref: ty::PolyTraitRef<'tcx>)
+                            trait_def_id: ast::DefId)
                             -> bool
 {
     // Because we query yes/no results frequently, we keep a cache:
     let cached_result =
-        tcx.object_safety_cache.borrow().get(&trait_ref.def_id()).cloned();
+        tcx.object_safety_cache.borrow().get(&trait_def_id).cloned();
 
     let result =
         cached_result.unwrap_or_else(|| {
-            let result = object_safety_violations(tcx, trait_ref.clone()).is_empty();
+            let result = object_safety_violations(tcx, trait_def_id).is_empty();
 
             // Record just a yes/no result in the cache; this is what is
             // queried most frequently. Note that this may overwrite a
             // previous result, but always with the same thing.
-            tcx.object_safety_cache.borrow_mut().insert(trait_ref.def_id(), result);
+            tcx.object_safety_cache.borrow_mut().insert(trait_def_id, result);
 
             result
         });
 
-    debug!("is_object_safe({}) = {}", trait_ref.repr(tcx), result);
+    debug!("is_object_safe({}) = {}", trait_def_id.repr(tcx), result);
 
     result
 }
 
 pub fn object_safety_violations<'tcx>(tcx: &ty::ctxt<'tcx>,
-                                      sub_trait_ref: ty::PolyTraitRef<'tcx>)
+                                      trait_def_id: ast::DefId)
                                       -> Vec<ObjectSafetyViolation<'tcx>>
 {
-    supertraits(tcx, sub_trait_ref)
-        .flat_map(|tr| object_safety_violations_for_trait(tcx, tr.def_id()).into_iter())
+    traits::supertrait_def_ids(tcx, trait_def_id)
+        .flat_map(|def_id| object_safety_violations_for_trait(tcx, def_id).into_iter())
         .collect()
 }
 

src/librustc/middle/traits/select.rs

@@ -1237,7 +1237,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // self-type from one of the other inputs. Without this check,
         // these cases wind up being considered ambiguous due to a
         // (spurious) ambiguity introduced here.
-        if !object_safety::is_object_safe(self.tcx(), obligation.predicate.to_poly_trait_ref()) {
+        let predicate_trait_ref = obligation.predicate.to_poly_trait_ref();
+        if !object_safety::is_object_safe(self.tcx(), predicate_trait_ref.def_id()) {
             return;
         }
 

src/librustc/middle/traits/util.rs

@@ -209,6 +209,47 @@ pub fn transitive_bounds<'cx, 'tcx>(tcx: &'cx ty::ctxt<'tcx>,
     elaborate_trait_refs(tcx, bounds).filter_to_traits()
 }
 
+///////////////////////////////////////////////////////////////////////////
+// Iterator over def-ids of supertraits
+
+pub struct SupertraitDefIds<'cx, 'tcx:'cx> {
+    tcx: &'cx ty::ctxt<'tcx>,
+    stack: Vec<ast::DefId>,
+    visited: FnvHashSet<ast::DefId>,
+}
+
+pub fn supertrait_def_ids<'cx, 'tcx>(tcx: &'cx ty::ctxt<'tcx>,
+                                     trait_def_id: ast::DefId)
+                                     -> SupertraitDefIds<'cx, 'tcx>
+{
+    SupertraitDefIds {
+        tcx: tcx,
+        stack: vec![trait_def_id],
+        visited: Some(trait_def_id).into_iter().collect(),
+    }
+}
+
+impl<'cx, 'tcx> Iterator for SupertraitDefIds<'cx, 'tcx> {
+    type Item = ast::DefId;
+
+    fn next(&mut self) -> Option<ast::DefId> {
+        let def_id = match self.stack.pop() {
+            Some(def_id) => def_id,
+            None => { return None; }
+        };
+
+        let predicates = ty::lookup_super_predicates(self.tcx, def_id);
+        let visited = &mut self.visited;
+        self.stack.extend(
+            predicates.predicates
+                      .iter()
+                      .filter_map(|p| p.to_opt_poly_trait_ref())
+                      .map(|t| t.def_id())
+                      .filter(|&super_def_id| visited.insert(super_def_id)));
+        Some(def_id)
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Other
 ///////////////////////////////////////////////////////////////////////////

src/librustc_typeck/check/vtable.rs

@@ -28,18 +28,17 @@ pub fn check_object_safety<'tcx>(tcx: &ty::ctxt<'tcx>,
                                  object_trait: &ty::TyTrait<'tcx>,
                                  span: Span)
 {
-    let object_trait_ref =
-        object_trait.principal_trait_ref_with_self_ty(tcx, tcx.types.err);
+    let trait_def_id = object_trait.principal_def_id();
 
-    if traits::is_object_safe(tcx, object_trait_ref.clone()) {
+    if traits::is_object_safe(tcx, trait_def_id) {
         return;
     }
 
     span_err!(tcx.sess, span, E0038,
               "cannot convert to a trait object because trait `{}` is not object-safe",
-              ty::item_path_str(tcx, object_trait_ref.def_id()));
+              ty::item_path_str(tcx, trait_def_id));
 
-    let violations = traits::object_safety_violations(tcx, object_trait_ref.clone());
+    let violations = traits::object_safety_violations(tcx, trait_def_id);
     for violation in violations {
         match violation {
             ObjectSafetyViolation::SizedSelf => {