Use `Environment` instead of `ty::ParamEnv` in chalk context

11 files changed, 271 insertions, 103 deletions

diff --git a/src/librustc/dep_graph/dep_node.rs b/src/librustc/dep_graph/dep_node.rs
index 994bbe727fc..de03892b994 100644
--- a/src/librustc/dep_graph/dep_node.rs
+++ b/src/librustc/dep_graph/dep_node.rs
@@ -70,6 +70,7 @@ use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
 use std::fmt;
 use std::hash::Hash;
 use syntax_pos::symbol::InternedString;
+use traits;
 use traits::query::{
     CanonicalProjectionGoal, CanonicalTyGoal, CanonicalTypeOpEqGoal, CanonicalTypeOpSubtypeGoal,
     CanonicalPredicateGoal, CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpNormalizeGoal,
@@ -550,6 +551,7 @@ define_dep_nodes!( <'tcx>
     [anon] TraitSelect,
 
     [] ParamEnv(DefId),
+    [] Environment(DefId),
     [] DescribeDef(DefId),
 
     // FIXME(mw): DefSpans are not really inputs since they are derived from
@@ -669,7 +671,7 @@ define_dep_nodes!( <'tcx>
     [input] Features,
 
     [] ProgramClausesFor(DefId),
-    [] ProgramClausesForEnv(ParamEnv<'tcx>),
+    [] ProgramClausesForEnv(traits::Environment<'tcx>),
     [] WasmImportModuleMap(CrateNum),
     [] ForeignModules(CrateNum),
 
diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index e54968c5274..8df249d7341 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -1418,7 +1418,15 @@ impl_stable_hash_for!(enum traits::QuantifierKind {
     Existential
 });
 
+<<<<<<< HEAD
 impl_stable_hash_for!(struct ty::subst::UserSubsts<'tcx> { substs, user_self_ty });
 
 impl_stable_hash_for!(struct ty::subst::UserSelfTy<'tcx> { impl_def_id, self_ty });
 
+=======
+impl_stable_hash_for!(
+    impl<'tcx> for struct traits::Environment<'tcx> {
+        clauses,
+    }
+);
+>>>>>>> Use `Environment` instead of `ty::ParamEnv` in chalk context
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 6e4abee32c0..d95b0844e87 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -278,6 +278,8 @@ pub type TraitObligations<'tcx> = Vec<TraitObligation<'tcx>>;
 /// * `DomainGoal`
 /// * `Goal`
 /// * `Clause`
+/// * `Environment`
+/// * `InEnvironment`
 /// are used for representing the trait system in the form of
 /// logic programming clauses. They are part of the interface
 /// for the chalk SLG solver.
@@ -378,6 +380,33 @@ pub struct ProgramClause<'tcx> {
     pub hypotheses: Goals<'tcx>,
 }
 
+/// A set of clauses that we assume to be true.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct Environment<'tcx> {
+    pub clauses: Clauses<'tcx>,
+}
+
+impl Environment<'tcx> {
+    pub fn with<G>(self, goal: G) -> InEnvironment<'tcx, G> {
+        InEnvironment {
+            environment: self,
+            goal,
+        }
+    }
+}
+
+/// Something (usually a goal), along with an environment.
+#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
+pub struct InEnvironment<'tcx, G> {
+    pub environment: Environment<'tcx>,
+    pub goal: G,
+}
+
+/// Compute the environment of the given item.
+fn environment<'a, 'tcx>(_tcx: TyCtxt<'a, 'tcx, 'tcx>, _def_id: DefId) -> Environment<'tcx> {
+    panic!()
+}
+
 pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;
 
 #[derive(Clone,Debug)]
@@ -1080,6 +1109,7 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
         codegen_fulfill_obligation: codegen::codegen_fulfill_obligation,
         vtable_methods,
         substitute_normalize_and_test_predicates,
+        environment,
         ..*providers
     };
 }
diff --git a/src/librustc/traits/structural_impls.rs b/src/librustc/traits/structural_impls.rs
index 1524f89af29..7b7446e27d2 100644
--- a/src/librustc/traits/structural_impls.rs
+++ b/src/librustc/traits/structural_impls.rs
@@ -658,7 +658,43 @@ EnumTypeFoldableImpl! {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::List<traits::Clause<'tcx>> {
+BraceStructTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for traits::Environment<'tcx> { clauses }
+}
+
+BraceStructTypeFoldableImpl! {
+    impl<'tcx, G> TypeFoldable<'tcx> for traits::InEnvironment<'tcx, G> {
+        environment,
+        goal
+    } where G: TypeFoldable<'tcx>
+}
+
+impl<'a, 'tcx> Lift<'tcx> for traits::Environment<'a> {
+    type Lifted = traits::Environment<'tcx>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
+        tcx.lift(&self.clauses).map(|clauses| {
+            traits::Environment {
+                clauses,
+            }
+        })
+    }
+}
+
+impl<'a, 'tcx, G: Lift<'tcx>> Lift<'tcx> for traits::InEnvironment<'a, G> {
+    type Lifted = traits::InEnvironment<'tcx, G::Lifted>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Self::Lifted> {
+        tcx.lift(&self.environment).and_then(|environment| {
+            tcx.lift(&self.goal).map(|goal| {
+                traits::InEnvironment {
+                    environment,
+                    goal,
+                }
+            })
+        })
+    }
+}
+
+impl<'tcx> TypeFoldable<'tcx> for traits::Clauses<'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))
diff --git a/src/librustc/ty/query/config.rs b/src/librustc/ty/query/config.rs
index 79eab3c6f34..d0c3109da52 100644
--- a/src/librustc/ty/query/config.rs
+++ b/src/librustc/ty/query/config.rs
@@ -12,6 +12,7 @@ use dep_graph::SerializedDepNodeIndex;
 use dep_graph::DepNode;
 use hir::def_id::{CrateNum, DefId, DefIndex};
 use mir::interpret::GlobalId;
+use traits;
 use traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal, CanonicalTypeOpEqGoal,
     CanonicalTypeOpNormalizeGoal, CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpSubtypeGoal,
@@ -826,8 +827,14 @@ impl<'tcx> QueryDescription<'tcx> for queries::program_clauses_for<'tcx> {
 }
 
 impl<'tcx> QueryDescription<'tcx> for queries::program_clauses_for_env<'tcx> {
-    fn describe(_tcx: TyCtxt<'_, '_, '_>, _: ty::ParamEnv<'tcx>) -> Cow<'static, str> {
-        "generating chalk-style clauses for param env".into()
+    fn describe(_tcx: TyCtxt<'_, '_, '_>, _: traits::Environment<'tcx>) -> Cow<'static, str> {
+        "generating chalk-style clauses for environment".into()
+    }
+}
+
+impl<'tcx> QueryDescription<'tcx> for queries::environment<'tcx> {
+    fn describe(_tcx: TyCtxt<'_, '_, '_>, _: DefId) -> Cow<'static, str> {
+        "return a chalk-style environment".into()
     }
 }
 
diff --git a/src/librustc/ty/query/keys.rs b/src/librustc/ty/query/keys.rs
index 96b0a768001..f2d7a6792b5 100644
--- a/src/librustc/ty/query/keys.rs
+++ b/src/librustc/ty/query/keys.rs
@@ -12,6 +12,7 @@
 
 use infer::canonical::Canonical;
 use hir::def_id::{CrateNum, DefId, LOCAL_CRATE, DefIndex};
+use traits;
 use ty::{self, Ty, TyCtxt};
 use ty::subst::Substs;
 use ty::fast_reject::SimplifiedType;
@@ -181,6 +182,15 @@ impl<'tcx, T: Key> Key for ty::ParamEnvAnd<'tcx, T> {
     }
 }
 
+impl<'tcx> Key for traits::Environment<'tcx> {
+    fn query_crate(&self) -> CrateNum {
+        LOCAL_CRATE
+    }
+    fn default_span(&self, _: TyCtxt<'_, '_, '_>) -> Span {
+        DUMMY_SP
+    }
+}
+
 impl Key for InternedString {
     fn query_crate(&self) -> CrateNum {
         LOCAL_CRATE
diff --git a/src/librustc/ty/query/mod.rs b/src/librustc/ty/query/mod.rs
index c4f39ffcd20..83c8eab0f39 100644
--- a/src/librustc/ty/query/mod.rs
+++ b/src/librustc/ty/query/mod.rs
@@ -377,6 +377,8 @@ define_queries! { <'tcx>
         // might want to use `reveal_all()` method to change modes.
         [] fn param_env: ParamEnv(DefId) -> ty::ParamEnv<'tcx>,
 
+        [] fn environment: Environment(DefId) -> traits::Environment<'tcx>,
+
         // Trait selection queries. These are best used by invoking `ty.moves_by_default()`,
         // `ty.is_copy()`, etc, since that will prune the environment where possible.
         [] fn is_copy_raw: is_copy_dep_node(ty::ParamEnvAnd<'tcx, Ty<'tcx>>) -> bool,
@@ -664,7 +666,7 @@ define_queries! { <'tcx>
         [] fn program_clauses_for: ProgramClausesFor(DefId) -> Clauses<'tcx>,
 
         [] fn program_clauses_for_env: ProgramClausesForEnv(
-            ty::ParamEnv<'tcx>
+            traits::Environment<'tcx>
         ) -> Clauses<'tcx>,
     },
 
diff --git a/src/librustc/ty/query/plumbing.rs b/src/librustc/ty/query/plumbing.rs
index 39a59cf090e..f83f8bcf1a1 100644
--- a/src/librustc/ty/query/plumbing.rs
+++ b/src/librustc/ty/query/plumbing.rs
@@ -1156,6 +1156,7 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::CheckMatch => { force!(check_match, def_id!()); }
 
         DepKind::ParamEnv => { force!(param_env, def_id!()); }
+        DepKind::Environment => { force!(environment, def_id!()); }
         DepKind::DescribeDef => { force!(describe_def, def_id!()); }
         DepKind::DefSpan => { force!(def_span, def_id!()); }
         DepKind::LookupStability => { force!(lookup_stability, def_id!()); }
diff --git a/src/librustc_traits/chalk_context.rs b/src/librustc_traits/chalk_context.rs
index 536c1523406..2fd8aa0c3af 100644
--- a/src/librustc_traits/chalk_context.rs
+++ b/src/librustc_traits/chalk_context.rs
@@ -23,7 +23,9 @@ use rustc::traits::{
     Goal,
     GoalKind,
     ProgramClause,
-    QuantifierKind
+    QuantifierKind,
+    Environment,
+    InEnvironment,
 };
 use rustc::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use rustc::ty::subst::Kind;
@@ -68,10 +70,10 @@ BraceStructTypeFoldableImpl! {
 impl context::Context for ChalkArenas<'tcx> {
     type CanonicalExClause = Canonical<'tcx, ExClause<Self>>;
 
-    type CanonicalGoalInEnvironment = Canonical<'tcx, ty::ParamEnvAnd<'tcx, Goal<'tcx>>>;
+    type CanonicalGoalInEnvironment = Canonical<'tcx, InEnvironment<'tcx, Goal<'tcx>>>;
 
     // u-canonicalization not yet implemented
-    type UCanonicalGoalInEnvironment = Canonical<'tcx, ty::ParamEnvAnd<'tcx, Goal<'tcx>>>;
+    type UCanonicalGoalInEnvironment = Canonical<'tcx, InEnvironment<'tcx, Goal<'tcx>>>;
 
     type CanonicalConstrainedSubst = Canonical<'tcx, ConstrainedSubst<'tcx>>;
 
@@ -82,13 +84,13 @@ impl context::Context for ChalkArenas<'tcx> {
 
     type InferenceNormalizedSubst = CanonicalVarValues<'tcx>;
 
-    type GoalInEnvironment = ty::ParamEnvAnd<'tcx, Goal<'tcx>>;
+    type GoalInEnvironment = InEnvironment<'tcx, Goal<'tcx>>;
 
     type RegionConstraint = QueryRegionConstraint<'tcx>;
 
     type Substitution = CanonicalVarValues<'tcx>;
 
-    type Environment = ty::ParamEnv<'tcx>;
+    type Environment = Environment<'tcx>;
 
     type Goal = Goal<'tcx>;
 
@@ -105,17 +107,17 @@ impl context::Context for ChalkArenas<'tcx> {
     type UnificationResult = InferOk<'tcx, ()>;
 
     fn goal_in_environment(
-        env: &ty::ParamEnv<'tcx>,
+        env: &Environment<'tcx>,
         goal: Goal<'tcx>,
-    ) -> ty::ParamEnvAnd<'tcx, Goal<'tcx>> {
-        env.and(goal)
+    ) -> InEnvironment<'tcx, Goal<'tcx>> {
+        env.with(goal)
     }
 }
 
 impl context::AggregateOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
     fn make_solution(
         &self,
-        _root_goal: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        _root_goal: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
         _simplified_answers: impl context::AnswerStream<ChalkArenas<'gcx>>,
     ) -> Option<Canonical<'gcx, QueryResponse<'gcx, ()>>> {
         unimplemented!()
@@ -124,7 +126,10 @@ impl context::AggregateOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
 
 impl context::ContextOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
     /// True if this is a coinductive goal -- e.g., proving an auto trait.
-    fn is_coinductive(&self, _goal: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>) -> bool {
+    fn is_coinductive(
+        &self,
+        _goal: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>
+    ) -> bool {
         unimplemented!()
     }
 
@@ -142,7 +147,7 @@ impl context::ContextOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
     /// - the environment and goal found by substitution `S` into `arg`
     fn instantiate_ucanonical_goal<R>(
         &self,
-        _arg: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        _arg: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
         _op: impl context::WithInstantiatedUCanonicalGoal<ChalkArenas<'gcx>, Output = R>,
     ) -> R {
         unimplemented!()
@@ -175,19 +180,19 @@ impl context::ContextOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
     }
 
     fn canonical(
-        u_canon: &'a Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
-    ) -> &'a Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>> {
+        u_canon: &'a Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
+    ) -> &'a Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>> {
         u_canon
     }
 
     fn is_trivial_substitution(
-        _u_canon: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        _u_canon: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
         _canonical_subst: &Canonical<'gcx, ConstrainedSubst<'gcx>>,
     ) -> bool {
         unimplemented!()
     }
 
-    fn num_universes(_: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>) -> usize {
+    fn num_universes(_: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>) -> usize {
         0 // FIXME
     }
 
@@ -196,8 +201,8 @@ impl context::ContextOps<ChalkArenas<'gcx>> for ChalkContext<'cx, 'gcx> {
     /// but for the universes of universally quantified names.
     fn map_goal_from_canonical(
         _map: &UniverseMap,
-        value: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
-    ) -> Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>> {
+        value: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
+    ) -> Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>> {
         *value // FIXME universe maps not implemented yet
     }
 
@@ -267,10 +272,10 @@ impl context::InferenceTable<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 
     fn add_clauses(
         &mut self,
-        _env: &ty::ParamEnv<'tcx>,
+        _env: &Environment<'tcx>,
         _clauses: Vec<ProgramClause<'tcx>>,
-    ) -> ty::ParamEnv<'tcx> {
-        panic!("FIXME no method to add clauses to ParamEnv yet")
+    ) -> Environment<'tcx> {
+        panic!("FIXME no method to add clauses to Environment yet")
     }
 }
 
@@ -279,7 +284,7 @@ impl context::ResolventOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 {
     fn resolvent_clause(
         &mut self,
-        _environment: &ty::ParamEnv<'tcx>,
+        _environment: &Environment<'tcx>,
         _goal: &DomainGoal<'tcx>,
         _subst: &CanonicalVarValues<'tcx>,
         _clause: &ProgramClause<'tcx>,
@@ -290,8 +295,8 @@ impl context::ResolventOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
     fn apply_answer_subst(
         &mut self,
         _ex_clause: ChalkExClause<'tcx>,
-        _selected_goal: &ty::ParamEnvAnd<'tcx, Goal<'tcx>>,
-        _answer_table_goal: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        _selected_goal: &InEnvironment<'tcx, Goal<'tcx>>,
+        _answer_table_goal: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
         _canonical_answer_subst: &Canonical<'gcx, ConstrainedSubst<'gcx>>,
     ) -> chalk_engine::fallible::Fallible<ChalkExClause<'tcx>> {
         panic!()
@@ -303,8 +308,8 @@ impl context::TruncateOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 {
     fn truncate_goal(
         &mut self,
-        subgoal: &ty::ParamEnvAnd<'tcx, Goal<'tcx>>,
-    ) -> Option<ty::ParamEnvAnd<'tcx, Goal<'tcx>>> {
+        subgoal: &InEnvironment<'tcx, Goal<'tcx>>,
+    ) -> Option<InEnvironment<'tcx, Goal<'tcx>>> {
         Some(*subgoal) // FIXME we should truncate at some point!
     }
 
@@ -321,7 +326,7 @@ impl context::UnificationOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 {
     fn program_clauses(
         &self,
-        _environment: &ty::ParamEnv<'tcx>,
+        _environment: &Environment<'tcx>,
         goal: &DomainGoal<'tcx>,
     ) -> Vec<ProgramClause<'tcx>> {
         use rustc::traits::WhereClause::*;
@@ -389,8 +394,8 @@ impl context::UnificationOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 
     fn canonicalize_goal(
         &mut self,
-        value: &ty::ParamEnvAnd<'tcx, Goal<'tcx>>,
-    ) -> Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>> {
+        value: &InEnvironment<'tcx, Goal<'tcx>>,
+    ) -> Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>> {
         let mut _orig_values = OriginalQueryValues::default();
         self.infcx.canonicalize_query(value, &mut _orig_values)
     }
@@ -412,9 +417,9 @@ impl context::UnificationOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 
     fn u_canonicalize_goal(
         &mut self,
-        value: &Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        value: &Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
     ) -> (
-        Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>,
+        Canonical<'gcx, InEnvironment<'gcx, Goal<'gcx>>>,
         UniverseMap,
     ) {
         (value.clone(), UniverseMap)
@@ -422,14 +427,14 @@ impl context::UnificationOps<ChalkArenas<'gcx>, ChalkArenas<'tcx>>
 
     fn invert_goal(
         &mut self,
-        _value: &ty::ParamEnvAnd<'tcx, Goal<'tcx>>,
-    ) -> Option<ty::ParamEnvAnd<'tcx, Goal<'tcx>>> {
+        _value: &InEnvironment<'tcx, Goal<'tcx>>,
+    ) -> Option<InEnvironment<'tcx, Goal<'tcx>>> {
         panic!("goal inversion not yet implemented")
     }
 
     fn unify_parameters(
         &mut self,
-        _environment: &ty::ParamEnv<'tcx>,
+        _environment: &Environment<'tcx>,
         _a: &Kind<'tcx>,
         _b: &Kind<'tcx>,
     ) -> ChalkEngineFallible<InferOk<'tcx, ()>> {
diff --git a/src/librustc_traits/lowering/environment.rs b/src/librustc_traits/lowering/environment.rs
new file mode 100644
index 00000000000..b04766b087e
--- /dev/null
+++ b/src/librustc_traits/lowering/environment.rs
@@ -0,0 +1,127 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use rustc::traits::{
+    Clause,
+    Clauses,
+    DomainGoal,
+    FromEnv,
+    Goal,
+    ProgramClause,
+    Environment,
+};
+use rustc::ty::{TyCtxt, Ty};
+use rustc_data_structures::fx::FxHashSet;
+
+struct ClauseVisitor<'set, 'a, 'tcx: 'a> {
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    round: &'set mut FxHashSet<Clause<'tcx>>,
+}
+
+impl ClauseVisitor<'set, 'a, 'tcx> {
+    fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, round: &'set mut FxHashSet<Clause<'tcx>>) -> Self {
+        ClauseVisitor {
+            tcx,
+            round,
+        }
+    }
+
+    fn visit_ty(&mut self, _ty: Ty<'tcx>) {
+
+    }
+
+    fn visit_from_env(&mut self, from_env: FromEnv<'tcx>) {
+        match from_env {
+            FromEnv::Trait(predicate) => {
+                self.round.extend(
+                    self.tcx.program_clauses_for(predicate.def_id())
+                        .iter()
+                        .cloned()
+                );
+            }
+
+            FromEnv::Ty(ty) => self.visit_ty(ty),
+        }
+    }
+
+    fn visit_domain_goal(&mut self, domain_goal: DomainGoal<'tcx>) {
+        if let DomainGoal::FromEnv(from_env) = domain_goal {
+            self.visit_from_env(from_env);
+        }
+    }
+
+    fn visit_goal(&mut self, goal: Goal<'tcx>) {
+        match goal {
+            Goal::Implies(clauses, goal) => {
+                for clause in clauses {
+                    self.visit_clause(*clause);
+                }
+                self.visit_goal(*goal);
+            }
+
+            Goal::And(goal1, goal2) => {
+                self.visit_goal(*goal1);
+                self.visit_goal(*goal2);
+            }
+
+            Goal::Not(goal) => self.visit_goal(*goal),
+            Goal::DomainGoal(domain_goal) => self.visit_domain_goal(domain_goal),
+            Goal::Quantified(_, goal) => self.visit_goal(**goal.skip_binder()),
+            Goal::CannotProve => (),
+        }
+    }
+
+    fn visit_program_clause(&mut self, clause: ProgramClause<'tcx>) {
+        self.visit_domain_goal(clause.goal);
+        for goal in clause.hypotheses {
+            self.visit_goal(*goal);
+        }
+    }
+
+    fn visit_clause(&mut self, clause: Clause<'tcx>) {
+        match clause {
+            Clause::Implies(clause) => self.visit_program_clause(clause),
+            Clause::ForAll(clause) => self.visit_program_clause(*clause.skip_binder()),
+        }
+    }
+}
+
+crate fn program_clauses_for_env<'a, 'tcx>(
+    tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    environment: Environment<'tcx>,
+) -> Clauses<'tcx> {
+    debug!("program_clauses_for_env(environment={:?})", environment);
+
+    let mut last_round = FxHashSet();
+    {
+        let mut visitor = ClauseVisitor::new(tcx, &mut last_round);
+        for clause in environment.clauses {
+            visitor.visit_clause(*clause);
+        }
+    }
+
+    let mut closure = last_round.clone();
+    let mut next_round = FxHashSet();
+    while !last_round.is_empty() {
+        let mut visitor = ClauseVisitor::new(tcx, &mut next_round);
+        for clause in last_round {
+            visitor.visit_clause(clause);
+        }
+        last_round = next_round.drain()
+            .filter(|&clause| closure.insert(clause))
+            .collect();
+    }
+
+    debug!("program_clauses_for_env: closure = {:#?}", closure);
+
+    return tcx.mk_clauses(
+        closure.into_iter()
+    );
+}
diff --git a/src/librustc_traits/lowering.rs b/src/librustc_traits/lowering/mod.rs
index 1e3f0a21cef..07a5d6a31dd 100644
--- a/src/librustc_traits/lowering.rs
+++ b/src/librustc_traits/lowering/mod.rs
@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+mod environment;
+
 use rustc::hir::def_id::DefId;
 use rustc::hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc::hir::map::definitions::DefPathData;
@@ -25,8 +27,6 @@ use rustc::traits::{
 };
 use rustc::ty::query::Providers;
 use rustc::ty::{self, List, TyCtxt};
-use rustc_data_structures::fx::FxHashSet;
-use std::mem;
 use syntax::ast;
 
 use std::iter;
@@ -34,7 +34,7 @@ use std::iter;
 crate fn provide(p: &mut Providers) {
     *p = Providers {
         program_clauses_for,
-        program_clauses_for_env,
+        program_clauses_for_env: environment::program_clauses_for_env,
         ..*p
     };
 }
@@ -173,66 +173,6 @@ crate fn program_clauses_for<'a, 'tcx>(
     }
 }
 
-crate fn program_clauses_for_env<'a, 'tcx>(
-    tcx: TyCtxt<'a, 'tcx, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-) -> Clauses<'tcx> {
-    debug!("program_clauses_for_env(param_env={:?})", param_env);
-
-    let mut last_round = FxHashSet();
-    last_round.extend(
-        param_env
-            .caller_bounds
-            .iter()
-            .flat_map(|&p| predicate_def_id(p)),
-    );
-
-    let mut closure = last_round.clone();
-    let mut next_round = FxHashSet();
-    while !last_round.is_empty() {
-        next_round.extend(
-            last_round
-                .drain()
-                .flat_map(|def_id| {
-                    tcx.predicates_of(def_id)
-                        .instantiate_identity(tcx)
-                        .predicates
-                })
-                .flat_map(|p| predicate_def_id(p))
-                .filter(|&def_id| closure.insert(def_id)),
-        );
-        mem::swap(&mut next_round, &mut last_round);
-    }
-
-    debug!("program_clauses_for_env: closure = {:#?}", closure);
-
-    return tcx.mk_clauses(
-        closure
-            .into_iter()
-            .flat_map(|def_id| tcx.program_clauses_for(def_id).iter().cloned()),
-    );
-
-    /// Given that `predicate` is in the environment, returns the
-    /// def-id of something (e.g., a trait, associated item, etc)
-    /// whose predicates can also be assumed to be true. We will
-    /// compute the transitive closure of such things.
-    fn predicate_def_id<'tcx>(predicate: ty::Predicate<'tcx>) -> Option<DefId> {
-        match predicate {
-            ty::Predicate::Trait(predicate) => Some(predicate.def_id()),
-
-            ty::Predicate::Projection(projection) => Some(projection.item_def_id()),
-
-            ty::Predicate::WellFormed(..)
-            | ty::Predicate::RegionOutlives(..)
-            | ty::Predicate::TypeOutlives(..)
-            | ty::Predicate::ObjectSafe(..)
-            | ty::Predicate::ClosureKind(..)
-            | ty::Predicate::Subtype(..)
-            | ty::Predicate::ConstEvaluatable(..) => None,
-        }
-    }
-}
-
 fn program_clauses_for_trait<'a, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     def_id: DefId,
@@ -595,8 +535,8 @@ impl<'a, 'tcx> ClauseDumper<'a, 'tcx> {
             }
 
             if attr.check_name("rustc_dump_env_program_clauses") {
-                let param_env = self.tcx.param_env(def_id);
-                clauses = Some(self.tcx.program_clauses_for_env(param_env));
+                let environment = self.tcx.environment(def_id);
+                clauses = Some(self.tcx.program_clauses_for_env(environment));
             }
 
             if let Some(clauses) = clauses {