Refactor BuiltinBounds to Vec<DefId> on TraitObject.

Author: Mark-Simulacrum

src/librustc/traits/select.rs

@@ -41,6 +41,7 @@ use ty::{self, ToPredicate, ToPolyTraitRef, Ty, TyCtxt, TypeFoldable};
 use traits;
 use ty::fast_reject;
 use ty::relate::TypeRelation;
+use middle::lang_items;
 
 use rustc_data_structures::bitvec::BitVector;
 use rustc_data_structures::snapshot_vec::{SnapshotVecDelegate, SnapshotVec};
@@ -49,6 +50,7 @@ use std::fmt;
 use std::marker::PhantomData;
 use std::mem;
 use std::rc::Rc;
+use std::iter;
 use syntax::abi::Abi;
 use hir;
 use util::nodemap::FxHashMap;
@@ -1516,16 +1518,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             let self_ty = this.tcx().erase_late_bound_regions(&obligation.self_ty());
             let poly_trait_ref = match self_ty.sty {
                 ty::TyTrait(ref data) => {
-                    match this.tcx().lang_items.to_builtin_kind(obligation.predicate.def_id()) {
-                        Some(bound @ ty::BoundSend) | Some(bound @ ty::BoundSync) => {
-                            if data.builtin_bounds.contains(&bound) {
-                                debug!("assemble_candidates_from_object_ty: matched builtin bound, \
-                                        pushing candidate");
-                                candidates.vec.push(BuiltinObjectCandidate);
-                                return;
-                            }
-                        }
-                        _ => {}
+                    if data.auto_traits().any(|did| did == obligation.predicate.def_id()) {
+                        debug!("assemble_candidates_from_object_ty: matched builtin bound, \
+                                    pushing candidate");
+                        candidates.vec.push(BuiltinObjectCandidate);
+                        return;
                     }
 
                     match data.principal() {
@@ -1616,7 +1613,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 // #2 (region bounds).
                 match (data_a.principal(), data_b.principal()) {
                     (Some(ref a), Some(ref b)) => a.def_id() == b.def_id() &&
-                        data_a.builtin_bounds.is_superset(&data_b.builtin_bounds),
+                        data_b.auto_traits()
+                            // All of a's auto traits need to be in b's auto traits.
+                            .all(|b| data_a.auto_traits().any(|a| a == b)),
                     _ => false
                 }
             }
@@ -2481,7 +2480,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let new_trait = tcx.mk_trait(ty::TraitObject::new(
                     data_a.principal(),
                     data_b.region_bound,
-                    data_b.builtin_bounds,
+                    data_b.auto_traits().collect(),
                     data_a.projection_bounds.clone(),
                 ));
                 let origin = TypeOrigin::Misc(obligation.cause.span);
@@ -2504,10 +2503,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             // T -> Trait.
             (_, &ty::TyTrait(ref data)) => {
                 let mut object_dids =
-                    data.builtin_bounds.iter().flat_map(|bound| {
-                        tcx.lang_items.from_builtin_kind(bound).ok()
-                    })
-                    .chain(data.principal().map(|ref p| p.def_id()));
+                    data.auto_traits().chain(data.principal().map(|ref p| p.def_id()));
                 if let Some(did) = object_dids.find(|did| {
                     !tcx.is_object_safe(*did)
                 }) {
@@ -2527,19 +2523,21 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 push(data.principal().unwrap().with_self_ty(tcx, source).to_predicate());
 
                 // We can only make objects from sized types.
-                let mut builtin_bounds = data.builtin_bounds;
-                builtin_bounds.insert(ty::BoundSized);
+                let trait_refs = data.auto_traits()
+                    .chain(iter::once(
+                            tcx.lang_items.require(lang_items::SizedTraitLangItem)
+                            .unwrap_or_else(|msg| tcx.sess.fatal(&msg[..]))))
+                    .map(|did| ty::TraitRef {
+                        def_id: did,
+                        substs: tcx.mk_substs_trait(source, &[]),
+                    });
 
                 // Create additional obligations for all the various builtin
                 // bounds attached to the object cast. (In other words, if the
                 // object type is Foo+Send, this would create an obligation
                 // for the Send check.)
-                for bound in &builtin_bounds {
-                    if let Ok(tr) = tcx.trait_ref_for_builtin_bound(bound, source) {
-                        push(tr.to_predicate());
-                    } else {
-                        return Err(Unimplemented);
-                    }
+                for tr in trait_refs {
+                    push(tr.to_predicate());
                 }
 
                 // Create obligations for the projection predicates.

src/librustc/ty/relate.rs

@@ -428,7 +428,11 @@ pub fn super_relate_tys<'a, 'gcx, 'tcx, R>(relation: &mut R,
                     |relation| relation.relate_with_variance(ty::Contravariant,
                                                              &a_obj.region_bound,
                                                              &b_obj.region_bound))?;
-            let nb = relation.relate(&a_obj.builtin_bounds, &b_obj.builtin_bounds)?;
+            let nb = if !a_obj.auto_traits().eq(b_obj.auto_traits()) {
+                return Err(TypeError::Sorts(expected_found(relation, &a, &b)));
+            } else {
+                a_obj.auto_traits().collect()
+            };
             let pb = relation.relate(&a_obj.projection_bounds, &b_obj.projection_bounds)?;
             Ok(tcx.mk_trait(ty::TraitObject::new(principal, r, nb, pb)))
         }

src/librustc/ty/structural_impls.rs

@@ -432,7 +432,7 @@ impl<'tcx> TypeFoldable<'tcx> for ty::TraitObject<'tcx> {
         ty::TraitObject::new(
             self.principal().map(|p| p.fold_with(folder)),
             self.region_bound.fold_with(folder),
-            self.builtin_bounds,
+            self.auto_traits().collect(),
             self.projection_bounds.fold_with(folder),
         )
     }

src/librustc/ty/sty.rs

@@ -279,25 +279,29 @@ impl<'a, 'gcx, 'acx, 'tcx> ClosureSubsts<'tcx> {
 pub struct TraitObject<'tcx> {
     principal: Option<PolyExistentialTraitRef<'tcx>>,
     pub region_bound: &'tcx ty::Region,
-    pub builtin_bounds: BuiltinBounds,
+    auto_traits: Vec<DefId>,
     pub projection_bounds: Vec<PolyExistentialProjection<'tcx>>,
 }
 
 impl<'tcx> TraitObject<'tcx> {
     pub fn new(principal: Option<PolyExistentialTraitRef<'tcx>>, region_bound: &'tcx ty::Region,
-               builtin_bounds: BuiltinBounds, projection_bounds: Vec<PolyExistentialProjection<'tcx>>)
+               auto_traits: Vec<DefId>, projection_bounds: Vec<PolyExistentialProjection<'tcx>>)
         -> Self {
         TraitObject {
             principal: principal,
             region_bound: region_bound,
-            builtin_bounds: builtin_bounds,
+            auto_traits: auto_traits,
             projection_bounds: projection_bounds,
         }
     }
 
     pub fn principal(&self) -> Option<PolyExistentialTraitRef<'tcx>> {
         self.principal
     }
+
+    pub fn auto_traits<'a>(&'a self) -> impl Iterator<Item=DefId> + 'a {
+        self.auto_traits.iter().cloned()
+    }
 }
 
 /// A complete reference to a trait. These take numerous guises in syntax,
@@ -833,18 +837,22 @@ impl CLike for BuiltinBound {
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn try_add_builtin_trait(self,
-                                 trait_def_id: DefId,
-                                 builtin_bounds: &mut EnumSet<BuiltinBound>)
+                                 id: DefId,
+                                 auto_traits: &mut Vec<DefId>)
                                  -> bool
     {
-        //! Checks whether `trait_ref` refers to one of the builtin
-        //! traits, like `Send`, and adds the corresponding
-        //! bound to the set `builtin_bounds` if so. Returns true if `trait_ref`
-        //! is a builtin trait.
-
-        match self.lang_items.to_builtin_kind(trait_def_id) {
-            Some(bound) => { builtin_bounds.insert(bound); true }
-            None => false
+        //! Checks whether `id` refers to one of the builtin
+        //! traits, like `Send`, and adds it to `auto_traits` if so.
+        //! Returns true if `idf` refers to a builtin trait.
+
+        if Some(id) == self.lang_items.send_trait() ||
+            Some(id) == self.lang_items.sized_trait() ||
+            Some(id) == self.lang_items.copy_trait() ||
+            Some(id) == self.lang_items.sync_trait() {
+            auto_traits.push(id);
+            true
+        } else {
+            false
         }
     }
 }

src/librustc/ty/util.rs

@@ -535,7 +535,9 @@ impl<'a, 'gcx, 'tcx, H: Hasher> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tc
                 if let Some(ref p) = data.principal() {
                     self.def_id(p.def_id());
                 }
-                self.hash(data.builtin_bounds);
+                for d in data.auto_traits() {
+                    self.def_id(d);
+                }
             }
             TyTuple(tys) => {
                 self.hash(tys.len());

src/librustc/ty/wf.rs

@@ -298,7 +298,6 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
     /// is WF. Returns false if `ty0` is an unresolved type variable,
     /// in which case we are not able to simplify at all.
     fn compute(&mut self, ty0: Ty<'tcx>) -> bool {
-        let tcx = self.infcx.tcx;
         let mut subtys = ty0.walk();
         while let Some(ty) = subtys.next() {
             match ty.sty {
@@ -391,15 +390,12 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                     let cause = self.cause(traits::MiscObligation);
 
                     let component_traits =
-                        data.builtin_bounds.iter().flat_map(|bound| {
-                            tcx.lang_items.from_builtin_kind(bound).ok()
-                        })
-                        .chain(data.principal().map(|ref p| p.def_id()));
+                        data.auto_traits().chain(data.principal().map(|ref p| p.def_id()));
                     self.out.extend(
-                        component_traits.map(|did| { traits::Obligation::new(
+                        component_traits.map(|did| traits::Obligation::new(
                             cause.clone(),
                             ty::Predicate::ObjectSafe(did)
-                        )})
+                        ))
                     );
                 }
 
@@ -493,7 +489,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
             let implicit_bounds =
                 object_region_bounds(self.infcx.tcx,
                                      data.principal().unwrap(),
-                                     data.builtin_bounds);
+                                     data.auto_traits());
 
             let explicit_bound = data.region_bound;
 
@@ -512,18 +508,25 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
 /// they declare `trait SomeTrait : 'static`, for example, then
 /// `'static` would appear in the list. The hard work is done by
 /// `ty::required_region_bounds`, see that for more information.
-pub fn object_region_bounds<'a, 'gcx, 'tcx>(
+pub fn object_region_bounds<'a, 'gcx, 'tcx, I>(
     tcx: TyCtxt<'a, 'gcx, 'tcx>,
     principal: ty::PolyExistentialTraitRef<'tcx>,
-    others: ty::BuiltinBounds)
+    others: I)
     -> Vec<&'tcx ty::Region>
+    where I: Iterator<Item=DefId>
 {
     // Since we don't actually *know* the self type for an object,
     // this "open(err)" serves as a kind of dummy standin -- basically
     // a skolemized type.
     let open_ty = tcx.mk_infer(ty::FreshTy(0));
 
-    let mut predicates = others.to_predicates(tcx, open_ty);
+    let mut predicates = others.map(|d| {
+        let trait_ref = ty::TraitRef {
+            def_id: d,
+            substs: tcx.mk_substs_trait(open_ty, &[])
+        };
+        trait_ref.to_predicate()
+    }).collect::<Vec<_>>();
     predicates.push(principal.with_self_ty(tcx, open_ty).to_predicate());
 
     tcx.required_region_bounds(open_ty, predicates)

src/librustc/util/ppaux.rs

@@ -349,13 +349,15 @@ impl<'tcx> fmt::Display for ty::TraitObject<'tcx> {
             }).collect();
 
             let tap = ty::Binder(TraitAndProjections(principal, projections));
-            in_binder(f, tcx, &ty::Binder(""), Some(tap))
-        })?;
+            in_binder(f, tcx, &ty::Binder(""), Some(tap))?;
 
-        // Builtin bounds.
-        for bound in &self.builtin_bounds {
-            write!(f, " + {:?}", bound)?;
-        }
+            // Builtin bounds.
+            for did in self.auto_traits() {
+                write!(f, " + {}", tcx.item_path_str(did))?;
+            }
+
+            Ok(())
+        })?;
 
         // FIXME: It'd be nice to compute from context when this bound
         // is implied, but that's non-trivial -- we'd perhaps have to
@@ -474,10 +476,14 @@ impl<'tcx> fmt::Debug for ty::TraitObject<'tcx> {
             write!(f, "{}", region_str)?;
         }
 
-        for bound in &self.builtin_bounds {
-            maybe_continue(f)?;
-            write!(f, "{:?}", bound)?;
-        }
+        ty::tls::with(|tcx| {
+            for did in self.auto_traits() {
+                maybe_continue(f)?;
+                write!(f, " + {}", tcx.item_path_str(did))?;
+            }
+
+            Ok(())
+        })?;
 
         for projection_bound in &self.projection_bounds {
             maybe_continue(f)?;