traits: Implement interning for Goal and Clause

5 files changed, 151 insertions, 59 deletions

diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index b30fb2ce016..32fd93cf20a 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -23,13 +23,12 @@ use infer::outlives::env::OutlivesEnvironment;
 use middle::region;
 use middle::const_val::ConstEvalErr;
 use ty::subst::Substs;
-use ty::{self, AdtKind, Ty, TyCtxt, TypeFoldable, ToPredicate};
+use ty::{self, AdtKind, Slice, Ty, TyCtxt, TypeFoldable, ToPredicate};
 use ty::error::{ExpectedFound, TypeError};
 use infer::{InferCtxt};
 
 use rustc_data_structures::sync::Lrc;
 use std::rc::Rc;
-use std::convert::From;
 use syntax::ast;
 use syntax_pos::{Span, DUMMY_SP};
 
@@ -280,37 +279,39 @@ pub enum QuantifierKind {
     Existential,
 }
 
-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum Goal<'tcx> {
-    // FIXME: use interned refs instead of `Box`
-    Implies(Vec<Clause<'tcx>>, Box<Goal<'tcx>>),
-    And(Box<Goal<'tcx>>, Box<Goal<'tcx>>),
-    Not(Box<Goal<'tcx>>),
+    Implies(&'tcx Slice<Clause<'tcx>>, &'tcx Goal<'tcx>),
+    And(&'tcx Goal<'tcx>, &'tcx Goal<'tcx>),
+    Not(&'tcx Goal<'tcx>),
     DomainGoal(DomainGoal<'tcx>),
-    Quantified(QuantifierKind, Box<ty::Binder<Goal<'tcx>>>)
-}
-
-impl<'tcx> From<DomainGoal<'tcx>> for Goal<'tcx> {
-    fn from(domain_goal: DomainGoal<'tcx>) -> Self {
-        Goal::DomainGoal(domain_goal)
-    }
+    Quantified(QuantifierKind, ty::Binder<&'tcx Goal<'tcx>>)
 }
 
-impl<'tcx> From<PolyDomainGoal<'tcx>> for Goal<'tcx> {
-    fn from(domain_goal: PolyDomainGoal<'tcx>) -> Self {
+impl<'tcx> Goal<'tcx> {
+    pub fn from_poly_domain_goal<'a>(
+        domain_goal: PolyDomainGoal<'tcx>,
+        tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    ) -> Goal<'tcx> {
         match domain_goal.no_late_bound_regions() {
             Some(p) => p.into(),
             None => Goal::Quantified(
                 QuantifierKind::Universal,
-                Box::new(domain_goal.map_bound(|p| p.into()))
+                domain_goal.map_bound(|p| tcx.mk_goal(Goal::from(p)))
             ),
         }
     }
 }
 
+impl<'tcx> From<DomainGoal<'tcx>> for Goal<'tcx> {
+    fn from(domain_goal: DomainGoal<'tcx>) -> Self {
+        Goal::DomainGoal(domain_goal)
+    }
+}
+
 /// This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary
 /// Harrop Formulas".
-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub enum Clause<'tcx> {
     Implies(ProgramClause<'tcx>),
     ForAll(ty::Binder<ProgramClause<'tcx>>),
@@ -322,13 +323,13 @@ pub enum Clause<'tcx> {
 /// it with the reverse implication operator `:-` to emphasize the way
 /// that programs are actually solved (via backchaining, which starts
 /// with the goal to solve and proceeds from there).
-#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct ProgramClause<'tcx> {
     /// This goal will be considered true...
     pub goal: DomainGoal<'tcx>,
 
     /// ...if we can prove these hypotheses (there may be no hypotheses at all):
-    pub hypotheses: Vec<Goal<'tcx>>,
+    pub hypotheses: &'tcx Slice<Goal<'tcx>>,
 }
 
 pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;
diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs
index 865a9a34aaa..523cd42940e 100644
--- a/src/librustc/traits/structural_impls.rs
+++ b/src/librustc/traits/structural_impls.rs
@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use rustc_data_structures::accumulate_vec::AccumulateVec;
 use traits;
 use traits::project::Normalized;
 use ty::{self, Lift, TyCtxt};
@@ -557,6 +558,28 @@ EnumTypeFoldableImpl! {
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Slice<traits::Goal<'tcx>> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        let v = self.iter().map(|t| t.fold_with(folder)).collect::<AccumulateVec<[_; 8]>>();
+        folder.tcx().intern_goals(&v)
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|t| t.visit_with(visitor))
+    }
+}
+
+impl<'tcx> TypeFoldable<'tcx> for &'tcx traits::Goal<'tcx> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        let v = (**self).fold_with(folder);
+        folder.tcx().mk_goal(v)
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        (**self).visit_with(visitor)
+    }
+}
+
 BraceStructTypeFoldableImpl! {
     impl<'tcx> TypeFoldable<'tcx> for traits::ProgramClause<'tcx> {
         goal,
@@ -570,3 +593,14 @@ EnumTypeFoldableImpl! {
         (traits::Clause::ForAll)(clause),
     }
 }
+
+impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Slice<traits::Clause<'tcx>> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        let v = self.iter().map(|t| t.fold_with(folder)).collect::<AccumulateVec<[_; 8]>>();
+        folder.tcx().intern_clauses(&v)
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|t| t.visit_with(visitor))
+    }
+}
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 2713b2d11e0..4acef5855d8 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -38,6 +38,7 @@ use ty::subst::{Kind, Substs};
 use ty::ReprOptions;
 use ty::Instance;
 use traits;
+use traits::{Clause, Goal};
 use ty::{self, Ty, TypeAndMut};
 use ty::{TyS, TypeVariants, Slice};
 use ty::{AdtKind, AdtDef, ClosureSubsts, GeneratorInterior, Region, Const};
@@ -125,34 +126,40 @@ impl<'tcx> GlobalArenas<'tcx> {
     }
 }
 
+type InternedSet<'tcx, T> = Lock<FxHashSet<Interned<'tcx, T>>>;
+
 pub struct CtxtInterners<'tcx> {
     /// The arena that types, regions, etc are allocated from
     arena: &'tcx DroplessArena,
 
     /// Specifically use a speedy hash algorithm for these hash sets,
     /// they're accessed quite often.
-    type_: Lock<FxHashSet<Interned<'tcx, TyS<'tcx>>>>,
-    type_list: Lock<FxHashSet<Interned<'tcx, Slice<Ty<'tcx>>>>>,
-    substs: Lock<FxHashSet<Interned<'tcx, Substs<'tcx>>>>,
-    canonical_var_infos: Lock<FxHashSet<Interned<'tcx, Slice<CanonicalVarInfo>>>>,
-    region: Lock<FxHashSet<Interned<'tcx, RegionKind>>>,
-    existential_predicates: Lock<FxHashSet<Interned<'tcx, Slice<ExistentialPredicate<'tcx>>>>>,
-    predicates: Lock<FxHashSet<Interned<'tcx, Slice<Predicate<'tcx>>>>>,
-    const_: Lock<FxHashSet<Interned<'tcx, Const<'tcx>>>>,
+    type_: InternedSet<'tcx, TyS<'tcx>>,
+    type_list: InternedSet<'tcx, Slice<Ty<'tcx>>>,
+    substs: InternedSet<'tcx, Substs<'tcx>>,
+    canonical_var_infos: InternedSet<'tcx, Slice<CanonicalVarInfo>>,
+    region: InternedSet<'tcx, RegionKind>,
+    existential_predicates: InternedSet<'tcx, Slice<ExistentialPredicate<'tcx>>>,
+    predicates: InternedSet<'tcx, Slice<Predicate<'tcx>>>,
+    const_: InternedSet<'tcx, Const<'tcx>>,
+    clauses: InternedSet<'tcx, Slice<Clause<'tcx>>>,
+    goals: InternedSet<'tcx, Slice<Goal<'tcx>>>,
 }
 
 impl<'gcx: 'tcx, 'tcx> CtxtInterners<'tcx> {
     fn new(arena: &'tcx DroplessArena) -> CtxtInterners<'tcx> {
         CtxtInterners {
-            arena: arena,
-            type_: Lock::new(FxHashSet()),
-            type_list: Lock::new(FxHashSet()),
-            substs: Lock::new(FxHashSet()),
-            canonical_var_infos: Lock::new(FxHashSet()),
-            region: Lock::new(FxHashSet()),
-            existential_predicates: Lock::new(FxHashSet()),
-            predicates: Lock::new(FxHashSet()),
-            const_: Lock::new(FxHashSet()),
+            arena,
+            type_: Default::default(),
+            type_list: Default::default(),
+            substs: Default::default(),
+            region: Default::default(),
+            existential_predicates: Default::default(),
+            canonical_var_infos: Default::default(),
+            predicates: Default::default(),
+            const_: Default::default(),
+            clauses: Default::default(),
+            goals: Default::default(),
         }
     }
 
@@ -2088,6 +2095,20 @@ impl<'tcx: 'lcx, 'lcx> Borrow<Const<'lcx>> for Interned<'tcx, Const<'tcx>> {
     }
 }
 
+impl<'tcx: 'lcx, 'lcx> Borrow<[Clause<'lcx>]>
+for Interned<'tcx, Slice<Clause<'tcx>>> {
+    fn borrow<'a>(&'a self) -> &'a [Clause<'lcx>] {
+        &self.0[..]
+    }
+}
+
+impl<'tcx: 'lcx, 'lcx> Borrow<[Goal<'lcx>]>
+for Interned<'tcx, Slice<Goal<'tcx>>> {
+    fn borrow<'a>(&'a self) -> &'a [Goal<'lcx>] {
+        &self.0[..]
+    }
+}
+
 macro_rules! intern_method {
     ($lt_tcx:tt, $name:ident: $method:ident($alloc:ty,
                                             $alloc_method:ident,
@@ -2185,7 +2206,9 @@ slice_interners!(
     existential_predicates: _intern_existential_predicates(ExistentialPredicate),
     predicates: _intern_predicates(Predicate),
     type_list: _intern_type_list(Ty),
-    substs: _intern_substs(Kind)
+    substs: _intern_substs(Kind),
+    clauses: _intern_clauses(Clause),
+    goals: _intern_goals(Goal)
 );
 
 // This isn't a perfect fit: CanonicalVarInfo slices are always
@@ -2490,6 +2513,22 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         }
     }
 
+    pub fn intern_clauses(self, ts: &[Clause<'tcx>]) -> &'tcx Slice<Clause<'tcx>> {
+        if ts.len() == 0 {
+            Slice::empty()
+        } else {
+            self._intern_clauses(ts)
+        }
+    }
+
+    pub fn intern_goals(self, ts: &[Goal<'tcx>]) -> &'tcx Slice<Goal<'tcx>> {
+        if ts.len() == 0 {
+            Slice::empty()
+        } else {
+            self._intern_goals(ts)
+        }
+    }
+
     pub fn mk_fn_sig<I>(self,
                         inputs: I,
                         output: I::Item,
@@ -2536,6 +2575,20 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_substs(iter::once(s).chain(t.into_iter().cloned()).map(Kind::from))
     }
 
+    pub fn mk_clauses<I: InternAs<[Clause<'tcx>],
+        &'tcx Slice<Clause<'tcx>>>>(self, iter: I) -> I::Output {
+        iter.intern_with(|xs| self.intern_clauses(xs))
+    }
+
+    pub fn mk_goals<I: InternAs<[Goal<'tcx>],
+        &'tcx Slice<Goal<'tcx>>>>(self, iter: I) -> I::Output {
+        iter.intern_with(|xs| self.intern_goals(xs))
+    }
+
+    pub fn mk_goal(self, goal: Goal<'tcx>) -> &'tcx Goal {
+        &self.mk_goals(iter::once(goal))[0]
+    }
+
     pub fn lint_node<S: Into<MultiSpan>>(self,
                                          lint: &'static Lint,
                                          id: NodeId,
diff --git a/src/librustc/ty/maps/mod.rs b/src/librustc/ty/maps/mod.rs
index 5a23a3b952a..56634cc189e 100644
--- a/src/librustc/ty/maps/mod.rs
+++ b/src/librustc/ty/maps/mod.rs
@@ -39,7 +39,7 @@ use traits::query::dropck_outlives::{DtorckConstraint, DropckOutlivesResult};
 use traits::query::normalize::NormalizationResult;
 use traits::specialization_graph;
 use traits::Clause;
-use ty::{self, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt};
+use ty::{self, CrateInherentImpls, ParamEnvAnd, Slice, Ty, TyCtxt};
 use ty::steal::Steal;
 use ty::subst::Substs;
 use util::nodemap::{DefIdSet, DefIdMap, ItemLocalSet};
@@ -435,7 +435,7 @@ define_maps! { <'tcx>
 
     [] fn features_query: features_node(CrateNum) -> Lrc<feature_gate::Features>,
 
-    [] fn program_clauses_for: ProgramClausesFor(DefId) -> Lrc<Vec<Clause<'tcx>>>,
+    [] fn program_clauses_for: ProgramClausesFor(DefId) -> Lrc<&'tcx Slice<Clause<'tcx>>>,
 
     [] fn wasm_custom_sections: WasmCustomSections(CrateNum) -> Lrc<Vec<DefId>>,
     [] fn wasm_import_module_map: WasmImportModuleMap(CrateNum)
diff --git a/src/librustc_traits/lowering.rs b/src/librustc_traits/lowering.rs
index 3d24b087c59..df6793e8a60 100644
--- a/src/librustc_traits/lowering.rs
+++ b/src/librustc_traits/lowering.rs
@@ -11,12 +11,14 @@
 use rustc::hir::{self, ImplPolarity};
 use rustc::hir::def_id::DefId;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
-use rustc::ty::{self, TyCtxt};
+use rustc::ty::{self, Slice, TyCtxt};
 use rustc::ty::subst::Substs;
-use rustc::traits::{WhereClauseAtom, PolyDomainGoal, DomainGoal, ProgramClause, Clause};
+use rustc::traits::{WhereClauseAtom, PolyDomainGoal, DomainGoal, ProgramClause, Clause, Goal};
 use syntax::ast;
 use rustc_data_structures::sync::Lrc;
 
+use std::iter;
+
 trait Lower<T> {
     /// Lower a rustc construction (e.g. `ty::TraitPredicate`) to a chalk-like type.
     fn lower(&self) -> T;
@@ -113,7 +115,7 @@ impl<'tcx> IntoFromEnvGoal for DomainGoal<'tcx> {
 }
 
 crate fn program_clauses_for<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-    -> Lrc<Vec<Clause<'tcx>>>
+                                       -> Lrc<&'tcx Slice<Clause<'tcx>>>
 {
     let node_id = tcx.hir.as_local_node_id(def_id).unwrap();
     let item = tcx.hir.expect_item(node_id);
@@ -122,12 +124,12 @@ crate fn program_clauses_for<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefI
         hir::ItemImpl(..) => program_clauses_for_impl(tcx, def_id),
 
         // FIXME: other constructions e.g. traits, associated types...
-        _ => Lrc::new(vec![]),
+        _ => Lrc::new(tcx.mk_clauses(iter::empty::<Clause>())),
     }
 }
 
 fn program_clauses_for_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-    -> Lrc<Vec<Clause<'tcx>>>
+                                       -> Lrc<&'tcx Slice<Clause<'tcx>>>
 {
     // `trait Trait<P1..Pn> where WC { .. } // P0 == Self`
 
@@ -147,18 +149,18 @@ fn program_clauses_for_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefI
         }
     };
     // `FromEnv(Self: Trait<P1..Pn>)`
-    let from_env = DomainGoal::FromEnv(trait_pred.lower()).into();
+    let from_env = Goal::from(DomainGoal::FromEnv(trait_pred.lower()));
     // `Implemented(Self: Trait<P1..Pn>)`
     let impl_trait = DomainGoal::Holds(WhereClauseAtom::Implemented(trait_pred));
 
     // `Implemented(Self: Trait<P1..Pn>) :- FromEnv(Self: Trait<P1..Pn>)`
     let implemented_from_env = ProgramClause {
         goal: impl_trait,
-        hypotheses: vec![from_env],
+        hypotheses: tcx.mk_goals(iter::once(from_env)),
     };
-    let mut clauses = vec![
+    let clauses = iter::once(
         Clause::ForAll(ty::Binder::dummy(implemented_from_env))
-    ];
+    );
 
     // Rule Implied-Bound-From-Trait
     //
@@ -175,14 +177,14 @@ fn program_clauses_for_trait<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefI
     let where_clauses = &tcx.predicates_of(def_id).predicates;
     let implied_bound_clauses =
         where_clauses[1..].into_iter()
-        .map(|wc| implied_bound_from_trait(trait_pred, wc));
-    clauses.extend(implied_bound_clauses);
+        .map(|wc| implied_bound_from_trait(tcx, trait_pred, wc));
 
-    Lrc::new(clauses)
+    Lrc::new(tcx.mk_clauses(clauses.chain(implied_bound_clauses)))
 }
 
 /// For a given `where_clause`, returns a clause `FromEnv(WC) :- FromEnv(Self: Trait<P1..Pn>)`.
-fn implied_bound_from_trait<'tcx>(
+fn implied_bound_from_trait<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
     trait_pred: ty::TraitPredicate<'tcx>,
     where_clause: &ty::Predicate<'tcx>,
 ) -> Clause<'tcx> {
@@ -193,16 +195,16 @@ fn implied_bound_from_trait<'tcx>(
     Clause::ForAll(
         where_clause.lower().map_bound(|goal| ProgramClause {
             goal: goal.into_from_env_goal(),
-            hypotheses: vec![impl_trait.into()],
+            hypotheses: tcx.mk_goals(iter::once(Goal::from(impl_trait))),
         })
     )
 }
 
 fn program_clauses_for_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
-    -> Lrc<Vec<Clause<'tcx>>>
+                                      -> Lrc<&'tcx Slice<Clause<'tcx>>>
 {
     if let ImplPolarity::Negative = tcx.impl_polarity(def_id) {
-        return Lrc::new(vec![]);
+        return Lrc::new(tcx.mk_clauses(iter::empty::<Clause>()));
     }
 
     // Rule Implemented-From-Impl (see rustc guide)
@@ -224,9 +226,11 @@ fn program_clauses_for_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId
      // `Implemented(A0: Trait<A1..An>) :- WC`
     let clause = ProgramClause {
         goal: trait_pred,
-        hypotheses: where_clauses.into_iter().map(|wc| wc.into()).collect()
+        hypotheses: tcx.mk_goals(
+            where_clauses.into_iter().map(|wc| Goal::from_poly_domain_goal(wc, tcx))
+        )
     };
-    Lrc::new(vec![Clause::ForAll(ty::Binder::dummy(clause))])
+    Lrc::new(tcx.mk_clauses(iter::once(Clause::ForAll(ty::Binder::dummy(clause)))))
 }
 
 pub fn dump_program_clauses<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
@@ -248,7 +252,7 @@ impl<'a, 'tcx> ClauseDumper<'a, 'tcx > {
         for attr in attrs {
             if attr.check_name("rustc_dump_program_clauses") {
                 let clauses = self.tcx.program_clauses_for(def_id);
-                for clause in &*clauses {
+                for clause in *clauses {
                     // Skip the top-level binder for a less verbose output
                     let program_clause = match clause {
                         Clause::Implies(program_clause) => program_clause,