strip param-env from infcx

src/librustc/infer/combine.rs

@@ -55,6 +55,7 @@ pub struct CombineFields<'infcx, 'gcx: 'infcx+'tcx, 'tcx: 'infcx> {
     pub infcx: &'infcx InferCtxt<'infcx, 'gcx, 'tcx>,
     pub trace: TypeTrace<'tcx>,
     pub cause: Option<ty::relate::Cause>,
+    pub param_env: ty::ParamEnv<'tcx>,
     pub obligations: PredicateObligations<'tcx>,
 }
 
@@ -215,6 +216,7 @@ impl<'infcx, 'gcx, 'tcx> CombineFields<'infcx, 'gcx, 'tcx> {
 
         if needs_wf {
             self.obligations.push(Obligation::new(self.trace.cause.clone(),
+                                                  self.param_env,
                                                   ty::Predicate::WellFormed(b_ty)));
         }
 

src/librustc/infer/mod.rs

@@ -161,8 +161,6 @@ pub struct InferCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     // For region variables.
     region_vars: RegionVarBindings<'a, 'gcx, 'tcx>,
 
-    pub param_env: ty::ParamEnv<'gcx>,
-
     /// Caches the results of trait selection. This cache is used
     /// for things that have to do with the parameters in scope.
     pub selection_cache: traits::SelectionCache<'tcx>,
@@ -400,55 +398,39 @@ impl fmt::Display for FixupError {
 pub trait InferEnv<'a, 'tcx> {
     fn to_parts(self, tcx: TyCtxt<'a, 'tcx, 'tcx>)
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>);
+                    Option<ty::TypeckTables<'tcx>>);
 }
 
-impl<'a, 'tcx> InferEnv<'a, 'tcx> for Reveal {
+impl<'a, 'tcx> InferEnv<'a, 'tcx> for () {
     fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>) {
-        (None, None, ty::ParamEnv::empty(self))
+                    Option<ty::TypeckTables<'tcx>>) {
+        (None, None)
     }
 }
 
-impl<'a, 'tcx> InferEnv<'a, 'tcx> for ty::ParamEnv<'tcx> {
+impl<'a, 'tcx> InferEnv<'a, 'tcx> for &'a ty::TypeckTables<'tcx> {
     fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>) {
-        (None, None, self)
+                    Option<ty::TypeckTables<'tcx>>) {
+        (Some(self), None)
     }
 }
 
-impl<'a, 'tcx> InferEnv<'a, 'tcx> for (&'a ty::TypeckTables<'tcx>, ty::ParamEnv<'tcx>) {
+impl<'a, 'tcx> InferEnv<'a, 'tcx> for ty::TypeckTables<'tcx> {
     fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>) {
-        (Some(self.0), None, self.1)
-    }
-}
-
-impl<'a, 'tcx> InferEnv<'a, 'tcx> for (ty::TypeckTables<'tcx>, ty::ParamEnv<'tcx>) {
-    fn to_parts(self, _: TyCtxt<'a, 'tcx, 'tcx>)
-                -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>) {
-        (None, Some(self.0), self.1)
+                    Option<ty::TypeckTables<'tcx>>) {
+        (None, Some(self))
     }
 }
 
 impl<'a, 'tcx> InferEnv<'a, 'tcx> for hir::BodyId {
     fn to_parts(self, tcx: TyCtxt<'a, 'tcx, 'tcx>)
                 -> (Option<&'a ty::TypeckTables<'tcx>>,
-                    Option<ty::TypeckTables<'tcx>>,
-                    ty::ParamEnv<'tcx>) {
+                    Option<ty::TypeckTables<'tcx>>) {
         let def_id = tcx.hir.body_owner_def_id(self);
-        (Some(tcx.typeck_tables_of(def_id)),
-         None,
-         tcx.param_env(def_id))
+        (Some(tcx.typeck_tables_of(def_id)), None)
     }
 }
 
@@ -460,18 +442,16 @@ pub struct InferCtxtBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     arena: DroplessArena,
     fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
     tables: Option<&'a ty::TypeckTables<'gcx>>,
-    param_env: ty::ParamEnv<'gcx>,
 }
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
     pub fn infer_ctxt<E: InferEnv<'a, 'gcx>>(self, env: E) -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
-        let (tables, fresh_tables, param_env) = env.to_parts(self);
+        let (tables, fresh_tables) = env.to_parts(self);
         InferCtxtBuilder {
             global_tcx: self,
             arena: DroplessArena::new(),
             fresh_tables: fresh_tables.map(RefCell::new),
             tables: tables,
-            param_env: param_env,
         }
     }
 
@@ -480,7 +460,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
     /// If any inference functionality is used, ICEs will occur.
     pub fn borrowck_fake_infer_ctxt(self, body: hir::BodyId)
                                     -> InferCtxt<'a, 'gcx, 'gcx> {
-        let (tables, _, param_env) = body.to_parts(self);
+        let (tables, _) = body.to_parts(self);
         InferCtxt {
             tcx: self,
             tables: InferTables::Interned(tables.unwrap()),
@@ -488,7 +468,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
             int_unification_table: RefCell::new(UnificationTable::new()),
             float_unification_table: RefCell::new(UnificationTable::new()),
             region_vars: RegionVarBindings::new(self),
-            param_env: param_env,
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),
             projection_cache: RefCell::new(traits::ProjectionCache::new()),
@@ -509,7 +488,6 @@ impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
             ref arena,
             ref fresh_tables,
             tables,
-            param_env,
         } = *self;
         let tables = tables.map(InferTables::Interned).unwrap_or_else(|| {
             fresh_tables.as_ref().map_or(InferTables::Missing, InferTables::InProgress)
@@ -522,7 +500,6 @@ impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
             int_unification_table: RefCell::new(UnificationTable::new()),
             float_unification_table: RefCell::new(UnificationTable::new()),
             region_vars: RegionVarBindings::new(tcx),
-            param_env: param_env,
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),
             reported_trait_errors: RefCell::new(FxHashSet()),
@@ -563,7 +540,10 @@ pub struct CombinedSnapshot<'a, 'tcx:'a> {
 /// Helper trait for shortening the lifetimes inside a
 /// value for post-type-checking normalization.
 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
-    fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self;
+    fn trans_normalize<'a, 'tcx>(&self,
+                                 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                 param_env: ty::ParamEnv<'tcx>)
+                                 -> Self;
 }
 
 macro_rules! items { ($($item:item)+) => ($($item)+) }
@@ -571,9 +551,10 @@ macro_rules! impl_trans_normalize {
     ($lt_gcx:tt, $($ty:ty),+) => {
         items!($(impl<$lt_gcx> TransNormalize<$lt_gcx> for $ty {
             fn trans_normalize<'a, 'tcx>(&self,
-                                         infcx: &InferCtxt<'a, $lt_gcx, 'tcx>)
+                                         infcx: &InferCtxt<'a, $lt_gcx, 'tcx>,
+                                         param_env: ty::ParamEnv<'tcx>)
                                          -> Self {
-                infcx.normalize_projections_in(self)
+                infcx.normalize_projections_in(param_env, self)
             }
         })+);
     }
@@ -590,13 +571,16 @@ impl_trans_normalize!('gcx,
 );
 
 impl<'gcx> TransNormalize<'gcx> for LvalueTy<'gcx> {
-    fn trans_normalize<'a, 'tcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self {
+    fn trans_normalize<'a, 'tcx>(&self,
+                                 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                 param_env: ty::ParamEnv<'tcx>)
+                                 -> Self {
         match *self {
-            LvalueTy::Ty { ty } => LvalueTy::Ty { ty: ty.trans_normalize(infcx) },
+            LvalueTy::Ty { ty } => LvalueTy::Ty { ty: ty.trans_normalize(infcx, param_env) },
             LvalueTy::Downcast { adt_def, substs, variant_index } => {
                 LvalueTy::Downcast {
                     adt_def: adt_def,
-                    substs: substs.trans_normalize(infcx),
+                    substs: substs.trans_normalize(infcx, param_env),
                     variant_index: variant_index
                 }
             }
@@ -618,19 +602,23 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
         self.normalize_associated_type(&value)
     }
 
+    /// Fully normalizes any associated types in `value`, using an
+    /// empty environment and `Reveal::All` mode (therefore, suitable
+    /// only for monomorphized code during trans, basically).
     pub fn normalize_associated_type<T>(self, value: &T) -> T
         where T: TransNormalize<'tcx>
     {
         debug!("normalize_associated_type(t={:?})", value);
 
+        let param_env = ty::ParamEnv::empty(Reveal::All);
         let value = self.erase_regions(value);
 
         if !value.has_projection_types() {
             return value;
         }
 
-        self.infer_ctxt(Reveal::All).enter(|infcx| {
-            value.trans_normalize(&infcx)
+        self.infer_ctxt(()).enter(|infcx| {
+            value.trans_normalize(&infcx, param_env)
         })
     }
 
@@ -651,20 +639,20 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
             return value;
         }
 
-        self.infer_ctxt(env.reveal_all()).enter(|infcx| {
-            value.trans_normalize(&infcx)
+        self.infer_ctxt(()).enter(|infcx| {
+            value.trans_normalize(&infcx, env.reveal_all())
        })
     }
 }
 
 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
-    fn normalize_projections_in<T>(&self, value: &T) -> T::Lifted
+    fn normalize_projections_in<T>(&self, param_env: ty::ParamEnv<'tcx>, value: &T) -> T::Lifted
         where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
     {
         let mut selcx = traits::SelectionContext::new(self);
         let cause = traits::ObligationCause::dummy();
         let traits::Normalized { value: result, obligations } =
-            traits::normalize(&mut selcx, cause, value);
+            traits::normalize(&mut selcx, param_env, cause, value);
 
         debug!("normalize_projections_in: result={:?} obligations={:?}",
                 result, obligations);
@@ -803,48 +791,69 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         return variables;
     }
 
-    fn combine_fields(&'a self, trace: TypeTrace<'tcx>)
+    fn combine_fields(&'a self, trace: TypeTrace<'tcx>, param_env: ty::ParamEnv<'tcx>)
                       -> CombineFields<'a, 'gcx, 'tcx> {
         CombineFields {
             infcx: self,
             trace: trace,
             cause: None,
+            param_env,
             obligations: PredicateObligations::new(),
         }
     }
 
-    pub fn equate<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
+    pub fn equate<T>(&'a self,
+                     a_is_expected: bool,
+                     trace: TypeTrace<'tcx>,
+                     param_env: ty::ParamEnv<'tcx>,
+                     a: &T,
+                     b: &T)
         -> InferResult<'tcx, T>
         where T: Relate<'tcx>
     {
-        let mut fields = self.combine_fields(trace);
+        let mut fields = self.combine_fields(trace, param_env);
         let result = fields.equate(a_is_expected).relate(a, b);
         result.map(move |t| InferOk { value: t, obligations: fields.obligations })
     }
 
-    pub fn sub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
+    pub fn sub<T>(&'a self,
+                  a_is_expected: bool,
+                  trace: TypeTrace<'tcx>,
+                  param_env: ty::ParamEnv<'tcx>,
+                  a: &T,
+                  b: &T)
         -> InferResult<'tcx, T>
         where T: Relate<'tcx>
     {
-        let mut fields = self.combine_fields(trace);
+        let mut fields = self.combine_fields(trace, param_env);
         let result = fields.sub(a_is_expected).relate(a, b);
         result.map(move |t| InferOk { value: t, obligations: fields.obligations })
     }
 
-    pub fn lub<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
+    pub fn lub<T>(&'a self,
+                  a_is_expected: bool,
+                  trace: TypeTrace<'tcx>,
+                  param_env: ty::ParamEnv<'tcx>,
+                  a: &T,
+                  b: &T)
         -> InferResult<'tcx, T>
         where T: Relate<'tcx>
     {
-        let mut fields = self.combine_fields(trace);
+        let mut fields = self.combine_fields(trace, param_env);
         let result = fields.lub(a_is_expected).relate(a, b);
         result.map(move |t| InferOk { value: t, obligations: fields.obligations })
     }
 
-    pub fn glb<T>(&'a self, a_is_expected: bool, trace: TypeTrace<'tcx>, a: &T, b: &T)
+    pub fn glb<T>(&'a self,
+                  a_is_expected: bool,
+                  trace: TypeTrace<'tcx>,
+                  param_env: ty::ParamEnv<'tcx>,
+                  a: &T,
+                  b: &T)
         -> InferResult<'tcx, T>
         where T: Relate<'tcx>
     {
-        let mut fields = self.combine_fields(trace);
+        let mut fields = self.combine_fields(trace, param_env);
         let result = fields.glb(a_is_expected).relate(a, b);
         result.map(move |t| InferOk { value: t, obligations: fields.obligations })
     }
@@ -1011,6 +1020,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     pub fn sub_types(&self,
                      a_is_expected: bool,
                      cause: &ObligationCause<'tcx>,
+                     param_env: ty::ParamEnv<'tcx>,
                      a: Ty<'tcx>,
                      b: Ty<'tcx>)
                      -> InferResult<'tcx, ()>
@@ -1018,11 +1028,12 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         debug!("sub_types({:?} <: {:?})", a, b);
         self.commit_if_ok(|_| {
             let trace = TypeTrace::types(cause, a_is_expected, a, b);
-            self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
+            self.sub(a_is_expected, trace, param_env, &a, &b).map(|ok| ok.unit())
         })
     }
 
     pub fn can_sub_types(&self,
+                         param_env: ty::ParamEnv<'tcx>,
                          a: Ty<'tcx>,
                          b: Ty<'tcx>)
                          -> UnitResult<'tcx>
@@ -1030,7 +1041,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.probe(|_| {
             let origin = &ObligationCause::dummy();
             let trace = TypeTrace::types(origin, true, a, b);
-            self.sub(true, trace, &a, &b).map(|InferOk { obligations: _, .. }| {
+            self.sub(true, trace, param_env, &a, &b).map(|InferOk { obligations: _, .. }| {
                 // Ignore obligations, since we are unrolling
                 // everything anyway.
             })
@@ -1040,19 +1051,21 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     pub fn eq_types(&self,
                     a_is_expected: bool,
                     cause: &ObligationCause<'tcx>,
+                    param_env: ty::ParamEnv<'tcx>,
                     a: Ty<'tcx>,
                     b: Ty<'tcx>)
         -> InferResult<'tcx, ()>
     {
         self.commit_if_ok(|_| {
             let trace = TypeTrace::types(cause, a_is_expected, a, b);
-            self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
+            self.equate(a_is_expected, trace, param_env, &a, &b).map(|ok| ok.unit())
         })
     }
 
     pub fn eq_trait_refs(&self,
                          a_is_expected: bool,
                          cause: &ObligationCause<'tcx>,
+                         param_env: ty::ParamEnv<'tcx>,
                          a: ty::TraitRef<'tcx>,
                          b: ty::TraitRef<'tcx>)
         -> InferResult<'tcx, ()>
@@ -1063,21 +1076,24 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 cause: cause.clone(),
                 values: TraitRefs(ExpectedFound::new(a_is_expected, a, b))
             };
-            self.equate(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
+            self.equate(a_is_expected, trace, param_env, &a, &b).map(|ok| ok.unit())
         })
     }
 
     pub fn eq_impl_headers(&self,
                            a_is_expected: bool,
                            cause: &ObligationCause<'tcx>,
+                           param_env: ty::ParamEnv<'tcx>,
                            a: &ty::ImplHeader<'tcx>,
                            b: &ty::ImplHeader<'tcx>)
                            -> InferResult<'tcx, ()>
     {
         debug!("eq_impl_header({:?} = {:?})", a, b);
         match (a.trait_ref, b.trait_ref) {
-            (Some(a_ref), Some(b_ref)) => self.eq_trait_refs(a_is_expected, cause, a_ref, b_ref),
-            (None, None) => self.eq_types(a_is_expected, cause, a.self_ty, b.self_ty),
+            (Some(a_ref), Some(b_ref)) =>
+                self.eq_trait_refs(a_is_expected, cause, param_env, a_ref, b_ref),
+            (None, None) =>
+                self.eq_types(a_is_expected, cause, param_env, a.self_ty, b.self_ty),
             _ => bug!("mk_eq_impl_headers given mismatched impl kinds"),
         }
     }
@@ -1085,6 +1101,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     pub fn sub_poly_trait_refs(&self,
                                a_is_expected: bool,
                                cause: ObligationCause<'tcx>,
+                               param_env: ty::ParamEnv<'tcx>,
                                a: ty::PolyTraitRef<'tcx>,
                                b: ty::PolyTraitRef<'tcx>)
         -> InferResult<'tcx, ()>
@@ -1095,7 +1112,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 cause: cause,
                 values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a, b))
             };
-            self.sub(a_is_expected, trace, &a, &b).map(|ok| ok.unit())
+            self.sub(a_is_expected, trace, param_env, &a, &b).map(|ok| ok.unit())
         })
     }
 
@@ -1109,6 +1126,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     pub fn equality_predicate(&self,
                               cause: &ObligationCause<'tcx>,
+                              param_env: ty::ParamEnv<'tcx>,
                               predicate: &ty::PolyEquatePredicate<'tcx>)
         -> InferResult<'tcx, ()>
     {
@@ -1116,7 +1134,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             let (ty::EquatePredicate(a, b), skol_map) =
                 self.skolemize_late_bound_regions(predicate, snapshot);
             let cause_span = cause.span;
-            let eqty_ok = self.eq_types(false, cause, a, b)?;
+            let eqty_ok = self.eq_types(false, cause, param_env, a, b)?;
             self.leak_check(false, cause_span, &skol_map, snapshot)?;
             self.pop_skolemized(skol_map, snapshot);
             Ok(eqty_ok.unit())
@@ -1125,6 +1143,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     pub fn subtype_predicate(&self,
                              cause: &ObligationCause<'tcx>,
+                             param_env: ty::ParamEnv<'tcx>,
                              predicate: &ty::PolySubtypePredicate<'tcx>)
         -> Option<InferResult<'tcx, ()>>
     {
@@ -1153,7 +1172,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 self.skolemize_late_bound_regions(predicate, snapshot);
 
             let cause_span = cause.span;
-            let ok = self.sub_types(a_is_expected, cause, a, b)?;
+            let ok = self.sub_types(a_is_expected, cause, param_env, a, b)?;
             self.leak_check(false, cause_span, &skol_map, snapshot)?;
             self.pop_skolemized(skol_map, snapshot);
             Ok(ok.unit())
@@ -1555,6 +1574,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
     /// details.
     pub fn match_poly_projection_predicate(&self,
                                            cause: ObligationCause<'tcx>,
+                                           param_env: ty::ParamEnv<'tcx>,
                                            match_a: ty::PolyProjectionPredicate<'tcx>,
                                            match_b: ty::TraitRef<'tcx>)
                                            -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
@@ -1567,7 +1587,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         };
 
         let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref, p.ty));
-        let mut combine = self.combine_fields(trace);
+        let mut combine = self.combine_fields(trace, param_env);
         let result = combine.higher_ranked_match(span, &match_pair, &match_b, true)?;
         Ok(InferOk { value: result, obligations: combine.obligations })
     }
@@ -1586,7 +1606,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.region_vars.verify_generic_bound(origin, kind, a, bound);
     }
 
-    pub fn can_equate<T>(&self, a: &T, b: &T) -> UnitResult<'tcx>
+    pub fn can_equate<T>(&self, param_env: ty::ParamEnv<'tcx>, a: &T, b: &T) -> UnitResult<'tcx>
         where T: Relate<'tcx> + fmt::Debug
     {
         debug!("can_equate({:?}, {:?})", a, b);
@@ -1596,7 +1616,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
             // generic so we don't have to do anything quite this
             // terrible.
             let trace = TypeTrace::dummy(self.tcx);
-            self.equate(true, trace, a, b).map(|InferOk { obligations: _, .. }| {
+            self.equate(true, trace, param_env, a, b).map(|InferOk { obligations: _, .. }| {
                 // We can intentionally ignore obligations here, since
                 // this is part of a simple test for general
                 // "equatability". However, it's not entirely clear
@@ -1617,9 +1637,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         self.resolve_type_vars_or_error(&ty)
     }
 
-    pub fn type_moves_by_default(&self, ty: Ty<'tcx>, span: Span) -> bool {
+    pub fn type_moves_by_default(&self,
+                                 param_env: ty::ParamEnv<'tcx>,
+                                 ty: Ty<'tcx>,
+                                 span: Span)
+                                 -> bool {
         let ty = self.resolve_type_vars_if_possible(&ty);
-        if let Some(ty) = self.tcx.lift_to_global(&ty) {
+        if let Some((param_env, ty)) = self.tcx.lift_to_global(&(param_env, ty)) {
             // Even if the type may have no inference variables, during
             // type-checking closure types are in local tables only.
             let local_closures = match self.tables {
@@ -1627,7 +1651,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 _ => false
             };
             if !local_closures {
-                return ty.moves_by_default(self.tcx.global_tcx(), self.param_env(), span);
+                return ty.moves_by_default(self.tcx.global_tcx(), param_env, span);
             }
         }
 
@@ -1637,17 +1661,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         // rightly refuses to work with inference variables, but
         // moves_by_default has a cache, which we want to use in other
         // cases.
-        !traits::type_known_to_meet_bound(self, ty, copy_def_id, span)
+        !traits::type_known_to_meet_bound(self, param_env, ty, copy_def_id, span)
     }
 
     pub fn upvar_capture(&self, upvar_id: ty::UpvarId) -> Option<ty::UpvarCapture<'tcx>> {
         self.tables.borrow().upvar_capture_map.get(&upvar_id).cloned()
     }
 
-    pub fn param_env(&self) -> ty::ParamEnv<'gcx> {
-        self.param_env
-    }
-
     pub fn closure_kind(&self,
                         def_id: DefId)
                         -> Option<ty::ClosureKind>

src/librustc/infer/sub.rs

@@ -96,6 +96,7 @@ impl<'combine, 'infcx, 'gcx, 'tcx> TypeRelation<'infcx, 'gcx, 'tcx>
                 self.fields.obligations.push(
                     Obligation::new(
                         self.fields.trace.cause.clone(),
+                        self.fields.param_env,
                         ty::Predicate::Subtype(
                             ty::Binder(ty::SubtypePredicate {
                                 a_is_expected: self.a_is_expected,

src/librustc/lib.rs

@@ -47,7 +47,7 @@
 #![cfg_attr(stage0, feature(staged_api))]
 #![cfg_attr(stage0, feature(loop_break_value))]
 
-#![recursion_limit="192"]
+#![recursion_limit="256"]
 
 extern crate arena;
 extern crate core;

src/librustc/middle/expr_use_visitor.rs

@@ -242,6 +242,7 @@ impl OverloadedCallType {
 pub struct ExprUseVisitor<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     mc: mc::MemCategorizationContext<'a, 'gcx, 'tcx>,
     delegate: &'a mut Delegate<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
 }
 
 // If the TYPER results in an error, it's because the type check
@@ -266,24 +267,28 @@ macro_rules! return_if_err {
 impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
     pub fn new(delegate: &'a mut (Delegate<'tcx>+'a),
                region_maps: &'a RegionMaps,
-               infcx: &'a InferCtxt<'a, 'gcx, 'tcx>)
+               infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+               param_env: ty::ParamEnv<'tcx>)
                -> Self
     {
         ExprUseVisitor::with_options(delegate,
                                      infcx,
+                                     param_env,
                                      region_maps,
                                      mc::MemCategorizationOptions::default())
     }
 
     pub fn with_options(delegate: &'a mut (Delegate<'tcx>+'a),
                         infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+                        param_env: ty::ParamEnv<'tcx>,
                         region_maps: &'a RegionMaps,
                         options: mc::MemCategorizationOptions)
                -> Self
     {
         ExprUseVisitor {
             mc: mc::MemCategorizationContext::with_options(infcx, region_maps, options),
-            delegate: delegate
+            delegate,
+            param_env,
         }
     }
 
@@ -318,7 +323,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
         debug!("delegate_consume(consume_id={}, cmt={:?})",
                consume_id, cmt);
 
-        let mode = copy_or_move(self.mc.infcx, &cmt, DirectRefMove);
+        let mode = copy_or_move(self.mc.infcx, self.param_env, &cmt, DirectRefMove);
         self.delegate.consume(consume_id, consume_span, cmt, mode);
     }
 
@@ -797,7 +802,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 PatKind::Binding(hir::BindByRef(..), ..) =>
                     mode.lub(BorrowingMatch),
                 PatKind::Binding(hir::BindByValue(..), ..) => {
-                    match copy_or_move(self.mc.infcx, &cmt_pat, PatBindingMove) {
+                    match copy_or_move(self.mc.infcx, self.param_env, &cmt_pat, PatBindingMove) {
                         Copy => mode.lub(CopyingMatch),
                         Move(..) => mode.lub(MovingMatch),
                     }
@@ -813,10 +818,9 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
     fn walk_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat, match_mode: MatchMode) {
         debug!("walk_pat cmt_discr={:?} pat={:?}", cmt_discr, pat);
 
-        let tcx = &self.tcx();
-        let mc = &self.mc;
+        let tcx = self.tcx();
         let infcx = self.mc.infcx;
-        let delegate = &mut self.delegate;
+        let ExprUseVisitor { ref mc, ref mut delegate, param_env } = *self;
         return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |mc, cmt_pat, pat| {
             if let PatKind::Binding(bmode, def_id, ..) = pat.node {
                 debug!("binding cmt_pat={:?} pat={:?} match_mode={:?}", cmt_pat, pat, match_mode);
@@ -840,7 +844,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                         }
                     }
                     hir::BindByValue(..) => {
-                        let mode = copy_or_move(infcx, &cmt_pat, PatBindingMove);
+                        let mode = copy_or_move(infcx, param_env, &cmt_pat, PatBindingMove);
                         debug!("walk_pat binding consuming pat");
                         delegate.consume_pat(pat, cmt_pat, mode);
                     }
@@ -899,7 +903,10 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                                                                    freevar.def));
                 match upvar_capture {
                     ty::UpvarCapture::ByValue => {
-                        let mode = copy_or_move(self.mc.infcx, &cmt_var, CaptureMove);
+                        let mode = copy_or_move(self.mc.infcx,
+                                                self.param_env,
+                                                &cmt_var,
+                                                CaptureMove);
                         self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
                     }
                     ty::UpvarCapture::ByRef(upvar_borrow) => {
@@ -929,11 +936,12 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
 }
 
 fn copy_or_move<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                param_env: ty::ParamEnv<'tcx>,
                                 cmt: &mc::cmt<'tcx>,
                                 move_reason: MoveReason)
                                 -> ConsumeMode
 {
-    if infcx.type_moves_by_default(cmt.ty, cmt.span) {
+    if infcx.type_moves_by_default(param_env, cmt.ty, cmt.span) {
         Move(move_reason)
     } else {
         Copy

src/librustc/traits/coherence.rs

@@ -10,10 +10,11 @@
 
 //! See `README.md` for high-level documentation
 
-use super::{SelectionContext, Obligation, ObligationCause};
-
 use hir::def_id::{DefId, LOCAL_CRATE};
+use syntax_pos::DUMMY_SP;
+use traits::{self, Normalized, SelectionContext, Obligation, ObligationCause, Reveal};
 use ty::{self, Ty, TyCtxt};
+use ty::subst::Subst;
 
 use infer::{InferCtxt, InferOk};
 
@@ -37,6 +38,28 @@ pub fn overlapping_impls<'cx, 'gcx, 'tcx>(infcx: &InferCtxt<'cx, 'gcx, 'tcx>,
     overlap(selcx, impl1_def_id, impl2_def_id)
 }
 
+fn with_fresh_ty_vars<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
+                                       param_env: ty::ParamEnv<'tcx>,
+                                       impl_def_id: DefId)
+                                       -> ty::ImplHeader<'tcx>
+{
+    let tcx = selcx.tcx();
+    let impl_substs = selcx.infcx().fresh_substs_for_item(DUMMY_SP, impl_def_id);
+
+    let header = ty::ImplHeader {
+        impl_def_id: impl_def_id,
+        self_ty: tcx.type_of(impl_def_id),
+        trait_ref: tcx.impl_trait_ref(impl_def_id),
+        predicates: tcx.predicates_of(impl_def_id).predicates
+    }.subst(tcx, impl_substs);
+
+    let Normalized { value: mut header, obligations } =
+        traits::normalize(selcx, param_env, ObligationCause::dummy(), &header);
+
+    header.predicates.extend(obligations.into_iter().map(|o| o.predicate));
+    header
+}
+
 /// Can both impl `a` and impl `b` be satisfied by a common type (including
 /// `where` clauses)? If so, returns an `ImplHeader` that unifies the two impls.
 fn overlap<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
@@ -48,8 +71,14 @@ fn overlap<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
            a_def_id,
            b_def_id);
 
-    let a_impl_header = ty::ImplHeader::with_fresh_ty_vars(selcx, a_def_id);
-    let b_impl_header = ty::ImplHeader::with_fresh_ty_vars(selcx, b_def_id);
+    // For the purposes of this check, we don't bring any skolemized
+    // types into scope; instead, we replace the generic types with
+    // fresh type variables, and hence we do our evaluations in an
+    // empty environment.
+    let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
+
+    let a_impl_header = with_fresh_ty_vars(selcx, param_env, a_def_id);
+    let b_impl_header = with_fresh_ty_vars(selcx, param_env, b_def_id);
 
     debug!("overlap: a_impl_header={:?}", a_impl_header);
     debug!("overlap: b_impl_header={:?}", b_impl_header);
@@ -57,6 +86,7 @@ fn overlap<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
     // Do `a` and `b` unify? If not, no overlap.
     let obligations = match selcx.infcx().eq_impl_headers(true,
                                                           &ObligationCause::dummy(),
+                                                          param_env,
                                                           &a_impl_header,
                                                           &b_impl_header) {
         Ok(InferOk { obligations, .. }) => {
@@ -75,6 +105,7 @@ fn overlap<'cx, 'gcx, 'tcx>(selcx: &mut SelectionContext<'cx, 'gcx, 'tcx>,
                      .chain(&b_impl_header.predicates)
                      .map(|p| infcx.resolve_type_vars_if_possible(p))
                      .map(|p| Obligation { cause: ObligationCause::dummy(),
+                                           param_env: param_env,
                                            recursion_depth: 0,
                                            predicate: p })
                      .chain(obligations)

src/librustc/traits/error_reporting.rs

@@ -179,12 +179,13 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                     data);
                 let normalized = super::normalize_projection_type(
                     &mut selcx,
+                    obligation.param_env,
                     data.projection_ty,
                     obligation.cause.clone(),
                     0
                 );
                 if let Err(error) = self.eq_types(
-                    false, &obligation.cause,
+                    false, &obligation.cause, obligation.param_env,
                     data.ty, normalized.value
                 ) {
                     values = Some(infer::ValuePairs::Types(ExpectedFound {
@@ -251,7 +252,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                        -> Option<DefId>
     {
         let tcx = self.tcx;
-
+        let param_env = obligation.param_env;
         let trait_ref = tcx.erase_late_bound_regions(&trait_ref);
         let trait_self_ty = trait_ref.self_ty();
 
@@ -268,7 +269,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
                 let impl_self_ty = impl_trait_ref.self_ty();
 
-                if let Ok(..) = self.can_equate(&trait_self_ty, &impl_self_ty) {
+                if let Ok(..) = self.can_equate(param_env, &trait_self_ty, &impl_self_ty) {
                     self_match_impls.push(def_id);
 
                     if trait_ref.substs.types().skip(1)
@@ -578,7 +579,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
                         // Try to report a help message
                         if !trait_ref.has_infer_types() &&
-                            self.predicate_can_apply(trait_ref) {
+                            self.predicate_can_apply(obligation.param_env, trait_ref) {
                             // If a where-clause may be useful, remind the
                             // user that they can add it.
                             //
@@ -607,6 +608,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                     ty::Predicate::Equate(ref predicate) => {
                         let predicate = self.resolve_type_vars_if_possible(predicate);
                         let err = self.equality_predicate(&obligation.cause,
+                                                          obligation.param_env,
                                                           &predicate).err().unwrap();
                         struct_span_err!(self.tcx.sess, span, E0278,
                             "the requirement `{}` is not satisfied (`{}`)",
@@ -936,7 +938,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
     /// Returns whether the trait predicate may apply for *some* assignment
     /// to the type parameters.
-    fn predicate_can_apply(&self, pred: ty::PolyTraitRef<'tcx>) -> bool {
+    fn predicate_can_apply(&self,
+                           param_env: ty::ParamEnv<'tcx>,
+                           pred: ty::PolyTraitRef<'tcx>)
+                           -> bool {
         struct ParamToVarFolder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
             infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
             var_map: FxHashMap<Ty<'tcx>, Ty<'tcx>>
@@ -967,12 +972,14 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
 
             let cleaned_pred = super::project::normalize(
                 &mut selcx,
+                param_env,
                 ObligationCause::dummy(),
                 &cleaned_pred
             ).value;
 
             let obligation = Obligation::new(
                 ObligationCause::dummy(),
+                param_env,
                 cleaned_pred.to_predicate()
             );
 

src/librustc/traits/fulfill.rs

@@ -113,6 +113,7 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> {
     /// `projection_ty` again.
     pub fn normalize_projection_type(&mut self,
                                      infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                     param_env: ty::ParamEnv<'tcx>,
                                      projection_ty: ty::ProjectionTy<'tcx>,
                                      cause: ObligationCause<'tcx>)
                                      -> Ty<'tcx>
@@ -125,7 +126,11 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> {
         // FIXME(#20304) -- cache
 
         let mut selcx = SelectionContext::new(infcx);
-        let normalized = project::normalize_projection_type(&mut selcx, projection_ty, cause, 0);
+        let normalized = project::normalize_projection_type(&mut selcx,
+                                                            param_env,
+                                                            projection_ty,
+                                                            cause,
+                                                            0);
 
         for obligation in normalized.obligations {
             self.register_predicate_obligation(infcx, obligation);
@@ -136,8 +141,12 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> {
         normalized.value
     }
 
+    /// Requires that `ty` must implement the trait with `def_id` in
+    /// the given environment. This trait must not have any type
+    /// parameters (except for `Self`).
     pub fn register_bound(&mut self,
                           infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                          param_env: ty::ParamEnv<'tcx>,
                           ty: Ty<'tcx>,
                           def_id: DefId,
                           cause: ObligationCause<'tcx>)
@@ -149,6 +158,7 @@ impl<'a, 'gcx, 'tcx> FulfillmentContext<'tcx> {
         self.register_predicate_obligation(infcx, Obligation {
             cause: cause,
             recursion_depth: 0,
+            param_env,
             predicate: trait_ref.to_predicate()
         });
     }
@@ -410,7 +420,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
         }
 
         ty::Predicate::Equate(ref binder) => {
-            match selcx.infcx().equality_predicate(&obligation.cause, binder) {
+            match selcx.infcx().equality_predicate(&obligation.cause, obligation.param_env, binder) {
                 Ok(InferOk { obligations, value: () }) => {
                     Ok(Some(obligations))
                 },
@@ -498,7 +508,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
         }
 
         ty::Predicate::WellFormed(ty) => {
-            match ty::wf::obligations(selcx.infcx(), obligation.cause.body_id,
+            match ty::wf::obligations(selcx.infcx(), obligation.param_env, obligation.cause.body_id,
                                       ty, obligation.cause.span) {
                 None => {
                     pending_obligation.stalled_on = vec![ty];
@@ -509,7 +519,7 @@ fn process_predicate<'a, 'gcx, 'tcx>(
         }
 
         ty::Predicate::Subtype(ref subtype) => {
-            match selcx.infcx().subtype_predicate(&obligation.cause, subtype) {
+            match selcx.infcx().subtype_predicate(&obligation.cause, obligation.param_env, subtype) {
                 None => {
                     // none means that both are unresolved
                     pending_obligation.stalled_on = vec![subtype.skip_binder().a,

src/librustc/traits/mod.rs

@@ -68,6 +68,7 @@ mod util;
 #[derive(Clone, PartialEq, Eq)]
 pub struct Obligation<'tcx, T> {
     pub cause: ObligationCause<'tcx>,
+    pub param_env: ty::ParamEnv<'tcx>,
     pub recursion_depth: usize,
     pub predicate: T,
 }
@@ -359,10 +360,11 @@ pub struct VtableFnPointerData<'tcx, N> {
 
 /// Creates predicate obligations from the generic bounds.
 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
+                                     param_env: ty::ParamEnv<'tcx>,
                                      generic_bounds: &ty::InstantiatedPredicates<'tcx>)
                                      -> PredicateObligations<'tcx>
 {
-    util::predicates_for_generics(cause, 0, generic_bounds)
+    util::predicates_for_generics(cause, 0, param_env, generic_bounds)
 }
 
 /// Determines whether the type `ty` is known to meet `bound` and
@@ -371,6 +373,7 @@ pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
 /// conservative towards *no impl*, which is the opposite of the
 /// `evaluate` methods).
 pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                                param_env: ty::ParamEnv<'tcx>,
                                                 ty: Ty<'tcx>,
                                                 def_id: DefId,
                                                 span: Span)
@@ -385,6 +388,7 @@ pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx
         substs: infcx.tcx.mk_substs_trait(ty, &[]),
     };
     let obligation = Obligation {
+        param_env,
         cause: ObligationCause::misc(span, ast::DUMMY_NODE_ID),
         recursion_depth: 0,
         predicate: trait_ref.to_predicate(),
@@ -408,7 +412,7 @@ pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx
         // anyhow).
         let cause = ObligationCause::misc(span, ast::DUMMY_NODE_ID);
 
-        fulfill_cx.register_bound(infcx, ty, def_id, cause);
+        fulfill_cx.register_bound(infcx, param_env, ty, def_id, cause);
 
         // Note: we only assume something is `Copy` if we can
         // *definitively* show that it implements `Copy`. Otherwise,
@@ -480,9 +484,11 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let elaborated_env = ty::ParamEnv::new(tcx.intern_predicates(&predicates),
                                            unnormalized_env.reveal);
 
-    tcx.infer_ctxt(elaborated_env).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
         let predicates = match fully_normalize(
-                &infcx, cause,
+            &infcx,
+            cause,
+            elaborated_env,
             // You would really want to pass infcx.param_env.caller_bounds here,
             // but that is an interned slice, and fully_normalize takes &T and returns T, so
             // without further refactoring, a slice can't be used. Luckily, we still have the
@@ -495,7 +501,7 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             Err(errors) => {
                 infcx.report_fulfillment_errors(&errors);
                 // An unnormalized env is better than nothing.
-                return infcx.param_env;
+                return elaborated_env;
             }
         };
 
@@ -517,13 +523,13 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 // all things considered.
                 tcx.sess.span_err(span, &fixup_err.to_string());
                 // An unnormalized env is better than nothing.
-                return infcx.param_env;
+                return elaborated_env;
             }
         };
 
         let predicates = match tcx.lift_to_global(&predicates) {
             Some(predicates) => predicates,
-            None => return infcx.param_env
+            None => return elaborated_env,
         };
 
         debug!("normalize_param_env_or_error: resolved predicates={:?}",
@@ -535,6 +541,7 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
 pub fn fully_normalize<'a, 'gcx, 'tcx, T>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
                                           cause: ObligationCause<'tcx>,
+                                          param_env: ty::ParamEnv<'tcx>,
                                           value: &T)
                                           -> Result<T, Vec<FulfillmentError<'tcx>>>
     where T : TypeFoldable<'tcx>
@@ -558,7 +565,7 @@ pub fn fully_normalize<'a, 'gcx, 'tcx, T>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
     let mut fulfill_cx = FulfillmentContext::new();
 
     let Normalized { value: normalized_value, obligations } =
-        project::normalize(selcx, cause, value);
+        project::normalize(selcx, param_env, cause, value);
     debug!("fully_normalize: normalized_value={:?} obligations={:?}",
            normalized_value,
            obligations);
@@ -580,10 +587,10 @@ pub fn fully_normalize<'a, 'gcx, 'tcx, T>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
     Ok(resolved_value)
 }
 
-/// Normalizes the predicates and checks whether they hold.  If this
-/// returns false, then either normalize encountered an error or one
-/// of the predicates did not hold. Used when creating vtables to
-/// check for unsatisfiable methods.
+/// Normalizes the predicates and checks whether they hold in an empty
+/// environment. If this returns false, then either normalize
+/// encountered an error or one of the predicates did not hold. Used
+/// when creating vtables to check for unsatisfiable methods.
 pub fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                predicates: Vec<ty::Predicate<'tcx>>)
                                                -> bool
@@ -591,17 +598,18 @@ pub fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     debug!("normalize_and_test_predicates(predicates={:?})",
            predicates);
 
-    tcx.infer_ctxt(Reveal::All).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
+        let param_env = ty::ParamEnv::empty(Reveal::All);
         let mut selcx = SelectionContext::new(&infcx);
         let mut fulfill_cx = FulfillmentContext::new();
         let cause = ObligationCause::dummy();
         let Normalized { value: predicates, obligations } =
-            normalize(&mut selcx, cause.clone(), &predicates);
+            normalize(&mut selcx, param_env, cause.clone(), &predicates);
         for obligation in obligations {
             fulfill_cx.register_predicate_obligation(&infcx, obligation);
         }
         for predicate in predicates {
-            let obligation = Obligation::new(cause.clone(), predicate);
+            let obligation = Obligation::new(cause.clone(), param_env, predicate);
             fulfill_cx.register_predicate_obligation(&infcx, obligation);
         }
 
@@ -663,30 +671,33 @@ pub fn get_vtable_methods<'a, 'tcx>(
 
 impl<'tcx,O> Obligation<'tcx,O> {
     pub fn new(cause: ObligationCause<'tcx>,
-               trait_ref: O)
+               param_env: ty::ParamEnv<'tcx>,
+               predicate: O)
                -> Obligation<'tcx, O>
     {
-        Obligation { cause: cause,
-                     recursion_depth: 0,
-                     predicate: trait_ref }
+        Obligation { cause, param_env, recursion_depth: 0, predicate }
     }
 
     fn with_depth(cause: ObligationCause<'tcx>,
                   recursion_depth: usize,
-                  trait_ref: O)
+                  param_env: ty::ParamEnv<'tcx>,
+                  predicate: O)
                   -> Obligation<'tcx, O>
     {
-        Obligation { cause: cause,
-                     recursion_depth: recursion_depth,
-                     predicate: trait_ref }
+        Obligation { cause, param_env, recursion_depth, predicate }
     }
 
-    pub fn misc(span: Span, body_id: ast::NodeId, trait_ref: O) -> Obligation<'tcx, O> {
-        Obligation::new(ObligationCause::misc(span, body_id), trait_ref)
+    pub fn misc(span: Span,
+                body_id: ast::NodeId,
+                param_env: ty::ParamEnv<'tcx>,
+                trait_ref: O)
+                -> Obligation<'tcx, O> {
+        Obligation::new(ObligationCause::misc(span, body_id), param_env, trait_ref)
     }
 
     pub fn with<P>(&self, value: P) -> Obligation<'tcx,P> {
         Obligation { cause: self.cause.clone(),
+                     param_env: self.param_env,
                      recursion_depth: self.recursion_depth,
                      predicate: value }
     }

src/librustc/traits/project.rs

@@ -168,7 +168,8 @@ fn project_and_unify_type<'cx, 'gcx, 'tcx>(
 
     let Normalized { value: normalized_ty, mut obligations } =
         match opt_normalize_projection_type(selcx,
-                                            obligation.predicate.projection_ty.clone(),
+                                            obligation.param_env,
+                                            obligation.predicate.projection_ty,
                                             obligation.cause.clone(),
                                             obligation.recursion_depth) {
             Some(n) => n,
@@ -180,7 +181,11 @@ fn project_and_unify_type<'cx, 'gcx, 'tcx>(
            obligations);
 
     let infcx = selcx.infcx();
-    match infcx.eq_types(true, &obligation.cause, normalized_ty, obligation.predicate.ty) {
+    match infcx.eq_types(true,
+                         &obligation.cause,
+                         obligation.param_env,
+                         normalized_ty,
+                         obligation.predicate.ty) {
         Ok(InferOk { obligations: inferred_obligations, value: () }) => {
             obligations.extend(inferred_obligations);
             Ok(Some(obligations))
@@ -194,17 +199,19 @@ fn project_and_unify_type<'cx, 'gcx, 'tcx>(
 /// combines the normalized result and any additional obligations that
 /// were incurred as result.
 pub fn normalize<'a, 'b, 'gcx, 'tcx, T>(selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+                                        param_env: ty::ParamEnv<'tcx>,
                                         cause: ObligationCause<'tcx>,
                                         value: &T)
                                         -> Normalized<'tcx, T>
     where T : TypeFoldable<'tcx>
 {
-    normalize_with_depth(selcx, cause, 0, value)
+    normalize_with_depth(selcx, param_env, cause, 0, value)
 }
 
 /// As `normalize`, but with a custom depth.
 pub fn normalize_with_depth<'a, 'b, 'gcx, 'tcx, T>(
     selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     cause: ObligationCause<'tcx>,
     depth: usize,
     value: &T)
@@ -213,7 +220,7 @@ pub fn normalize_with_depth<'a, 'b, 'gcx, 'tcx, T>(
     where T : TypeFoldable<'tcx>
 {
     debug!("normalize_with_depth(depth={}, value={:?})", depth, value);
-    let mut normalizer = AssociatedTypeNormalizer::new(selcx, cause, depth);
+    let mut normalizer = AssociatedTypeNormalizer::new(selcx, param_env, cause, depth);
     let result = normalizer.fold(value);
     debug!("normalize_with_depth: depth={} result={:?} with {} obligations",
            depth, result, normalizer.obligations.len());
@@ -227,6 +234,7 @@ pub fn normalize_with_depth<'a, 'b, 'gcx, 'tcx, T>(
 
 struct AssociatedTypeNormalizer<'a, 'b: 'a, 'gcx: 'b+'tcx, 'tcx: 'b> {
     selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     cause: ObligationCause<'tcx>,
     obligations: Vec<PredicateObligation<'tcx>>,
     depth: usize,
@@ -234,12 +242,14 @@ struct AssociatedTypeNormalizer<'a, 'b: 'a, 'gcx: 'b+'tcx, 'tcx: 'b> {
 
 impl<'a, 'b, 'gcx, 'tcx> AssociatedTypeNormalizer<'a, 'b, 'gcx, 'tcx> {
     fn new(selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+           param_env: ty::ParamEnv<'tcx>,
            cause: ObligationCause<'tcx>,
            depth: usize)
            -> AssociatedTypeNormalizer<'a, 'b, 'gcx, 'tcx>
     {
         AssociatedTypeNormalizer {
             selcx: selcx,
+            param_env: param_env,
             cause: cause,
             obligations: vec![],
             depth: depth,
@@ -305,6 +315,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for AssociatedTypeNormalizer<'a,
 
                 let Normalized { value: normalized_ty, obligations } =
                     normalize_projection_type(self.selcx,
+                                              self.param_env,
                                               data.clone(),
                                               self.cause.clone(),
                                               self.depth);
@@ -344,12 +355,13 @@ impl<'tcx,T> Normalized<'tcx,T> {
 /// obligation `<T as Trait>::Item == $X` for later.
 pub fn normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
     selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     projection_ty: ty::ProjectionTy<'tcx>,
     cause: ObligationCause<'tcx>,
     depth: usize)
     -> NormalizedTy<'tcx>
 {
-    opt_normalize_projection_type(selcx, projection_ty.clone(), cause.clone(), depth)
+    opt_normalize_projection_type(selcx, param_env, projection_ty.clone(), cause.clone(), depth)
         .unwrap_or_else(move || {
             // if we bottom out in ambiguity, create a type variable
             // and a deferred predicate to resolve this when more type
@@ -366,7 +378,7 @@ pub fn normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
                 ty: ty_var
             });
             let obligation = Obligation::with_depth(
-                cause, depth + 1, projection.to_predicate());
+                cause, depth + 1, param_env, projection.to_predicate());
             Normalized {
                 value: ty_var,
                 obligations: vec![obligation]
@@ -380,6 +392,7 @@ pub fn normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
 /// which indicates that there are unbound type variables.
 fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
     selcx: &'a mut SelectionContext<'b, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     projection_ty: ty::ProjectionTy<'tcx>,
     cause: ObligationCause<'tcx>,
     depth: usize)
@@ -449,6 +462,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
             let recursion_limit = selcx.tcx().sess.recursion_limit.get();
             let obligation = Obligation::with_depth(cause.clone(),
                                                     recursion_limit,
+                                                    param_env,
                                                     projection_ty);
             selcx.infcx().report_overflow_error(&obligation, false);
         }
@@ -464,11 +478,11 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
         Err(ProjectionCacheEntry::Error) => {
             debug!("opt_normalize_projection_type: \
                     found error");
-            return Some(normalize_to_error(selcx, projection_ty, cause, depth));
+            return Some(normalize_to_error(selcx, param_env, projection_ty, cause, depth));
         }
     }
 
-    let obligation = Obligation::with_depth(cause.clone(), depth, projection_ty.clone());
+    let obligation = Obligation::with_depth(cause.clone(), depth, param_env, projection_ty);
     match project_type(selcx, &obligation) {
         Ok(ProjectedTy::Progress(Progress { ty: projected_ty,
                                             mut obligations,
@@ -489,7 +503,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
                    cacheable);
 
             let result = if projected_ty.has_projection_types() {
-                let mut normalizer = AssociatedTypeNormalizer::new(selcx, cause, depth+1);
+                let mut normalizer = AssociatedTypeNormalizer::new(selcx, param_env, cause, depth+1);
                 let normalized_ty = normalizer.fold(&projected_ty);
 
                 debug!("opt_normalize_projection_type: \
@@ -540,7 +554,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
 
             infcx.projection_cache.borrow_mut()
                                   .error(projection_ty);
-            Some(normalize_to_error(selcx, projection_ty, cause, depth))
+            Some(normalize_to_error(selcx, param_env, projection_ty, cause, depth))
         }
     }
 }
@@ -565,6 +579,7 @@ fn opt_normalize_projection_type<'a, 'b, 'gcx, 'tcx>(
 /// because it contains `[type error]`. Yuck! (See issue #29857 for
 /// one case where this arose.)
 fn normalize_to_error<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tcx>,
+                                      param_env: ty::ParamEnv<'tcx>,
                                       projection_ty: ty::ProjectionTy<'tcx>,
                                       cause: ObligationCause<'tcx>,
                                       depth: usize)
@@ -573,6 +588,7 @@ fn normalize_to_error<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tc
     let trait_ref = projection_ty.trait_ref.to_poly_trait_ref();
     let trait_obligation = Obligation { cause: cause,
                                         recursion_depth: depth,
+                                        param_env,
                                         predicate: trait_ref.to_predicate() };
     let tcx = selcx.infcx().tcx;
     let def_id = tcx.associated_items(projection_ty.trait_ref.def_id).find(|i|
@@ -746,13 +762,12 @@ fn assemble_candidates_from_param_env<'cx, 'gcx, 'tcx>(
     candidate_set: &mut ProjectionTyCandidateSet<'tcx>)
 {
     debug!("assemble_candidates_from_param_env(..)");
-    let env_predicates = selcx.param_env().caller_bounds.iter().cloned();
     assemble_candidates_from_predicates(selcx,
                                         obligation,
                                         obligation_trait_ref,
                                         candidate_set,
                                         ProjectionTyCandidate::ParamEnv,
-                                        env_predicates);
+                                        obligation.param_env.caller_bounds.iter().cloned());
 }
 
 /// In the case of a nested projection like <<A as Foo>::FooT as Bar>::BarT, we may find
@@ -807,7 +822,7 @@ fn assemble_candidates_from_predicates<'cx, 'gcx, 'tcx, I>(
     candidate_set: &mut ProjectionTyCandidateSet<'tcx>,
     ctor: fn(ty::PolyProjectionPredicate<'tcx>) -> ProjectionTyCandidate<'tcx>,
     env_predicates: I)
-    where I: Iterator<Item=ty::Predicate<'tcx>>
+    where I: IntoIterator<Item=ty::Predicate<'tcx>>
 {
     debug!("assemble_candidates_from_predicates(obligation={:?})",
            obligation);
@@ -827,6 +842,7 @@ fn assemble_candidates_from_predicates<'cx, 'gcx, 'tcx, I>(
                         obligation_trait_ref.to_poly_trait_ref();
                     infcx.sub_poly_trait_refs(false,
                                               obligation.cause.clone(),
+                                              obligation.param_env,
                                               data_poly_trait_ref,
                                               obligation_poly_trait_ref)
                         .map(|InferOk { obligations: _, value: () }| {
@@ -936,7 +952,7 @@ fn assemble_candidates_from_impls<'cx, 'gcx, 'tcx>(
                 // get a result which isn't correct for all monomorphizations.
                 let new_candidate = if !is_default {
                     Some(ProjectionTyCandidate::Select)
-                } else if selcx.projection_mode() == Reveal::All {
+                } else if obligation.param_env.reveal == Reveal::All {
                     assert!(!poly_trait_ref.needs_infer());
                     if !poly_trait_ref.needs_subst() {
                         Some(ProjectionTyCandidate::Select)
@@ -1096,6 +1112,7 @@ fn confirm_object_candidate<'cx, 'gcx, 'tcx>(
             selcx.infcx().probe(|_| {
                 selcx.infcx().sub_poly_trait_refs(false,
                                                   obligation.cause.clone(),
+                                                  obligation.param_env,
                                                   data_poly_trait_ref,
                                                   obligation_poly_trait_ref).is_ok()
             })
@@ -1143,6 +1160,7 @@ fn confirm_closure_candidate<'cx, 'gcx, 'tcx>(
         value: closure_type,
         obligations
     } = normalize_with_depth(selcx,
+                             obligation.param_env,
                              obligation.cause.clone(),
                              obligation.recursion_depth+1,
                              &closure_type);
@@ -1203,8 +1221,9 @@ fn confirm_param_env_candidate<'cx, 'gcx, 'tcx>(
 {
     let infcx = selcx.infcx();
     let cause = obligation.cause.clone();
+    let param_env = obligation.param_env;
     let trait_ref = obligation.predicate.trait_ref;
-    match infcx.match_poly_projection_predicate(cause, poly_projection, trait_ref) {
+    match infcx.match_poly_projection_predicate(cause, param_env, poly_projection, trait_ref) {
         Ok(InferOk { value: ty_match, obligations }) => {
             Progress {
                 ty: ty_match.value,
@@ -1233,6 +1252,7 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
     let VtableImplData { substs, nested, impl_def_id } = impl_vtable;
 
     let tcx = selcx.tcx();
+    let param_env = obligation.param_env;
     let assoc_ty = assoc_ty_def(selcx, impl_def_id, obligation.predicate.item_name(tcx));
 
     let ty = if !assoc_ty.item.defaultness.has_value() {
@@ -1247,7 +1267,7 @@ fn confirm_impl_candidate<'cx, 'gcx, 'tcx>(
     } else {
         tcx.type_of(assoc_ty.item.def_id)
     };
-    let substs = translate_substs(selcx.infcx(), impl_def_id, substs, assoc_ty.node);
+    let substs = translate_substs(selcx.infcx(), param_env, impl_def_id, substs, assoc_ty.node);
     Progress {
         ty: ty.subst(tcx, substs),
         obligations: nested,

src/librustc/traits/select.rs

@@ -21,7 +21,6 @@ use super::{PredicateObligation, TraitObligation, ObligationCause};
 use super::{ObligationCauseCode, BuiltinDerivedObligation, ImplDerivedObligation};
 use super::{SelectionError, Unimplemented, OutputTypeParameterMismatch};
 use super::{ObjectCastObligation, Obligation};
-use super::Reveal;
 use super::TraitNotObjectSafe;
 use super::Selection;
 use super::SelectionResult;
@@ -315,18 +314,10 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         self.infcx.tcx
     }
 
-    pub fn param_env(&self) -> ty::ParamEnv<'gcx> {
-        self.infcx.param_env()
-    }
-
     pub fn closure_typer(&self) -> &'cx InferCtxt<'cx, 'gcx, 'tcx> {
         self.infcx
     }
 
-    pub fn projection_mode(&self) -> Reveal {
-        self.param_env().reveal
-    }
-
     /// Wraps the inference context's in_snapshot s.t. snapshot handling is only from the selection
     /// context's self.
     fn in_snapshot<R, F>(&mut self, f: F) -> R
@@ -540,7 +531,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::Predicate::Equate(ref p) => {
                 // does this code ever run?
-                match self.infcx.equality_predicate(&obligation.cause, p) {
+                match self.infcx.equality_predicate(&obligation.cause, obligation.param_env, p) {
                     Ok(InferOk { obligations, .. }) => {
                         self.inferred_obligations.extend(obligations);
                         EvaluatedToOk
@@ -551,7 +542,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::Predicate::Subtype(ref p) => {
                 // does this code ever run?
-                match self.infcx.subtype_predicate(&obligation.cause, p) {
+                match self.infcx.subtype_predicate(&obligation.cause, obligation.param_env, p) {
                     Some(Ok(InferOk { obligations, .. })) => {
                         self.inferred_obligations.extend(obligations);
                         EvaluatedToOk
@@ -562,7 +553,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             }
 
             ty::Predicate::WellFormed(ty) => {
-                match ty::wf::obligations(self.infcx, obligation.cause.body_id,
+                match ty::wf::obligations(self.infcx, obligation.param_env, obligation.cause.body_id,
                                           ty, obligation.cause.span) {
                     Some(obligations) =>
                         self.evaluate_predicates_recursively(previous_stack, obligations.iter()),
@@ -628,7 +619,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         let stack = self.push_stack(previous_stack, obligation);
         let fresh_trait_ref = stack.fresh_trait_ref;
-        if let Some(result) = self.check_evaluation_cache(fresh_trait_ref) {
+        if let Some(result) = self.check_evaluation_cache(obligation.param_env, fresh_trait_ref) {
             debug!("CACHE HIT: EVAL({:?})={:?}",
                    fresh_trait_ref,
                    result);
@@ -640,7 +631,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         debug!("CACHE MISS: EVAL({:?})={:?}",
                fresh_trait_ref,
                result);
-        self.insert_evaluation_cache(fresh_trait_ref, result);
+        self.insert_evaluation_cache(obligation.param_env, fresh_trait_ref, result);
 
         result
     }
@@ -751,10 +742,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         result
     }
 
-    fn check_evaluation_cache(&self, trait_ref: ty::PolyTraitRef<'tcx>)
+    fn check_evaluation_cache(&self,
+                              param_env: ty::ParamEnv<'tcx>,
+                              trait_ref: ty::PolyTraitRef<'tcx>)
                               -> Option<EvaluationResult>
     {
-        if self.can_use_global_caches() {
+        if self.can_use_global_caches(param_env) {
             let cache = self.tcx().evaluation_cache.hashmap.borrow();
             if let Some(cached) = cache.get(&trait_ref) {
                 return Some(cached.clone());
@@ -764,6 +757,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     }
 
     fn insert_evaluation_cache(&mut self,
+                               param_env: ty::ParamEnv<'tcx>,
                                trait_ref: ty::PolyTraitRef<'tcx>,
                                result: EvaluationResult)
     {
@@ -778,7 +772,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             return;
         }
 
-        if self.can_use_global_caches() {
+        if self.can_use_global_caches(param_env) {
             let mut cache = self.tcx().evaluation_cache.hashmap.borrow_mut();
             if let Some(trait_ref) = self.tcx().lift_to_global(&trait_ref) {
                 cache.insert(trait_ref, result);
@@ -819,7 +813,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                stack);
         assert!(!stack.obligation.predicate.has_escaping_regions());
 
-        if let Some(c) = self.check_candidate_cache(&cache_fresh_trait_pred) {
+        if let Some(c) = self.check_candidate_cache(stack.obligation.param_env,
+                                                    &cache_fresh_trait_pred) {
             debug!("CACHE HIT: SELECT({:?})={:?}",
                    cache_fresh_trait_pred,
                    c);
@@ -832,7 +827,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         if self.should_update_candidate_cache(&cache_fresh_trait_pred, &candidate) {
             debug!("CACHE MISS: SELECT({:?})={:?}",
                    cache_fresh_trait_pred, candidate);
-            self.insert_candidate_cache(cache_fresh_trait_pred, candidate.clone());
+            self.insert_candidate_cache(stack.obligation.param_env,
+                                        cache_fresh_trait_pred,
+                                        candidate.clone());
         }
 
         candidate
@@ -995,7 +992,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     /// Returns true if the global caches can be used.
     /// Do note that if the type itself is not in the
     /// global tcx, the local caches will be used.
-    fn can_use_global_caches(&self) -> bool {
+    fn can_use_global_caches(&self, param_env: ty::ParamEnv<'tcx>) -> bool {
         // If there are any where-clauses in scope, then we always use
         // a cache local to this particular scope. Otherwise, we
         // switch to a global cache. We used to try and draw
@@ -1003,7 +1000,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         // annoying and weird bugs like #22019 and #18290. This simple
         // rule seems to be pretty clearly safe and also still retains
         // a very high hit rate (~95% when compiling rustc).
-        if !self.param_env().caller_bounds.is_empty() {
+        if !param_env.caller_bounds.is_empty() {
             return false;
         }
 
@@ -1023,11 +1020,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     }
 
     fn check_candidate_cache(&mut self,
+                             param_env: ty::ParamEnv<'tcx>,
                              cache_fresh_trait_pred: &ty::PolyTraitPredicate<'tcx>)
                              -> Option<SelectionResult<'tcx, SelectionCandidate<'tcx>>>
     {
         let trait_ref = &cache_fresh_trait_pred.0.trait_ref;
-        if self.can_use_global_caches() {
+        if self.can_use_global_caches(param_env) {
             let cache = self.tcx().selection_cache.hashmap.borrow();
             if let Some(cached) = cache.get(&trait_ref) {
                 return Some(cached.clone());
@@ -1037,11 +1035,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     }
 
     fn insert_candidate_cache(&mut self,
+                              param_env: ty::ParamEnv<'tcx>,
                               cache_fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
                               candidate: SelectionResult<'tcx, SelectionCandidate<'tcx>>)
     {
         let trait_ref = cache_fresh_trait_pred.0.trait_ref;
-        if self.can_use_global_caches() {
+        if self.can_use_global_caches(param_env) {
             let mut cache = self.tcx().selection_cache.hashmap.borrow_mut();
             if let Some(trait_ref) = self.tcx().lift_to_global(&trait_ref) {
                 if let Some(candidate) = self.tcx().lift_to_global(&candidate) {
@@ -1099,6 +1098,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     {
         let TraitObligationStack { obligation, .. } = *stack;
         let ref obligation = Obligation {
+            param_env: obligation.param_env,
             cause: obligation.cause.clone(),
             recursion_depth: obligation.recursion_depth,
             predicate: self.infcx().resolve_type_vars_if_possible(&obligation.predicate)
@@ -1272,6 +1272,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let cause = obligation.cause.clone();
         match self.infcx.sub_poly_trait_refs(false,
                                              cause,
+                                             obligation.param_env,
                                              trait_bound.clone(),
                                              ty::Binder(skol_trait_ref.clone())) {
             Ok(InferOk { obligations, .. }) => {
@@ -1296,7 +1297,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                stack.obligation);
 
         let all_bounds =
-            self.param_env().caller_bounds
+            stack.obligation.param_env.caller_bounds
                                       .iter()
                                       .filter_map(|o| o.to_opt_poly_trait_ref());
 
@@ -1953,6 +1954,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     }
 
     fn collect_predicates_for_types(&mut self,
+                                    param_env: ty::ParamEnv<'tcx>,
                                     cause: ObligationCause<'tcx>,
                                     recursion_depth: usize,
                                     trait_def_id: DefId,
@@ -1981,11 +1983,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     this.infcx().skolemize_late_bound_regions(&ty, snapshot);
                 let Normalized { value: normalized_ty, mut obligations } =
                     project::normalize_with_depth(this,
+                                                  param_env,
                                                   cause.clone(),
                                                   recursion_depth,
                                                   &skol_ty);
                 let skol_obligation =
-                    this.tcx().predicate_for_trait_def(
+                    this.tcx().predicate_for_trait_def(param_env,
                                                        cause.clone(),
                                                        trait_def_id,
                                                        recursion_depth,
@@ -2131,7 +2134,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             };
 
             let cause = obligation.derived_cause(BuiltinDerivedObligation);
-            self.collect_predicates_for_types(cause,
+            self.collect_predicates_for_types(obligation.param_env,
+                                              cause,
                                               obligation.recursion_depth+1,
                                               trait_def,
                                               nested)
@@ -2175,6 +2179,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         let cause = obligation.derived_cause(BuiltinDerivedObligation);
         let mut obligations = self.collect_predicates_for_types(
+            obligation.param_env,
             cause,
             obligation.recursion_depth+1,
             trait_def_id,
@@ -2187,6 +2192,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             let cause = obligation.derived_cause(ImplDerivedObligation);
             this.impl_or_trait_obligations(cause,
                                            obligation.recursion_depth + 1,
+                                           obligation.param_env,
                                            trait_def_id,
                                            &trait_ref.substs,
                                            skol_map,
@@ -2220,9 +2226,13 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                                   snapshot);
             debug!("confirm_impl_candidate substs={:?}", substs);
             let cause = obligation.derived_cause(ImplDerivedObligation);
-            this.vtable_impl(impl_def_id, substs, cause,
+            this.vtable_impl(impl_def_id,
+                             substs,
+                             cause,
                              obligation.recursion_depth + 1,
-                             skol_map, snapshot)
+                             obligation.param_env,
+                             skol_map,
+                             snapshot)
         })
     }
 
@@ -2231,6 +2241,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                    mut substs: Normalized<'tcx, &'tcx Substs<'tcx>>,
                    cause: ObligationCause<'tcx>,
                    recursion_depth: usize,
+                   param_env: ty::ParamEnv<'tcx>,
                    skol_map: infer::SkolemizationMap<'tcx>,
                    snapshot: &infer::CombinedSnapshot)
                    -> VtableImplData<'tcx, PredicateObligation<'tcx>>
@@ -2244,6 +2255,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let mut impl_obligations =
             self.impl_or_trait_obligations(cause,
                                            recursion_depth,
+                                           param_env,
                                            impl_def_id,
                                            &substs.value,
                                            skol_map,
@@ -2345,6 +2357,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             .map_bound(|(trait_ref, _)| trait_ref);
 
         self.confirm_poly_trait_refs(obligation.cause.clone(),
+                                     obligation.param_env,
                                      obligation.predicate.to_poly_trait_ref(),
                                      trait_ref)?;
         Ok(VtableFnPointerData { fn_ty: self_ty, nested: vec![] })
@@ -2374,11 +2387,13 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                obligations);
 
         self.confirm_poly_trait_refs(obligation.cause.clone(),
+                                     obligation.param_env,
                                      obligation.predicate.to_poly_trait_ref(),
                                      trait_ref)?;
 
         obligations.push(Obligation::new(
             obligation.cause.clone(),
+            obligation.param_env,
             ty::Predicate::ClosureKind(closure_def_id, kind)));
 
         Ok(VtableClosureData {
@@ -2415,6 +2430,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     /// report an error to the user.
     fn confirm_poly_trait_refs(&mut self,
                                obligation_cause: ObligationCause<'tcx>,
+                               obligation_param_env: ty::ParamEnv<'tcx>,
                                obligation_trait_ref: ty::PolyTraitRef<'tcx>,
                                expected_trait_ref: ty::PolyTraitRef<'tcx>)
                                -> Result<(), SelectionError<'tcx>>
@@ -2422,6 +2438,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let obligation_trait_ref = obligation_trait_ref.clone();
         self.infcx.sub_poly_trait_refs(false,
                                        obligation_cause.clone(),
+                                       obligation_param_env,
                                        expected_trait_ref.clone(),
                                        obligation_trait_ref.clone())
             .map(|InferOk { obligations, .. }| self.inferred_obligations.extend(obligations))
@@ -2458,7 +2475,11 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let new_trait = tcx.mk_dynamic(
                     ty::Binder(tcx.mk_existential_predicates(iter)), r_b);
                 let InferOk { obligations, .. } =
-                    self.infcx.eq_types(false, &obligation.cause, new_trait, target)
+                    self.infcx.eq_types(false,
+                                        &obligation.cause,
+                                        obligation.param_env,
+                                        new_trait,
+                                        target)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
 
@@ -2469,6 +2490,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let outlives = ty::OutlivesPredicate(r_a, r_b);
                 nested.push(Obligation::with_depth(cause,
                                                    obligation.recursion_depth + 1,
+                                                   obligation.param_env,
                                                    ty::Binder(outlives).to_predicate()));
             }
 
@@ -2488,6 +2510,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 let mut push = |predicate| {
                     nested.push(Obligation::with_depth(cause.clone(),
                                                        obligation.recursion_depth + 1,
+                                                       obligation.param_env,
                                                        predicate));
                 };
 
@@ -2517,7 +2540,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             // [T; n] -> [T].
             (&ty::TyArray(a, _), &ty::TySlice(b)) => {
                 let InferOk { obligations, .. } =
-                    self.infcx.eq_types(false, &obligation.cause, a, b)
+                    self.infcx.eq_types(false, &obligation.cause, obligation.param_env, a, b)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
             }
@@ -2580,12 +2603,17 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 });
                 let new_struct = tcx.mk_adt(def, tcx.mk_substs(params));
                 let InferOk { obligations, .. } =
-                    self.infcx.eq_types(false, &obligation.cause, new_struct, target)
+                    self.infcx.eq_types(false,
+                                        &obligation.cause,
+                                        obligation.param_env,
+                                        new_struct,
+                                        target)
                     .map_err(|_| Unimplemented)?;
                 self.inferred_obligations.extend(obligations);
 
                 // Construct the nested Field<T>: Unsize<Field<U>> predicate.
                 nested.push(tcx.predicate_for_trait_def(
+                    obligation.param_env,
                     obligation.cause.clone(),
                     obligation.predicate.def_id(),
                     obligation.recursion_depth + 1,
@@ -2655,6 +2683,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         let impl_trait_ref =
             project::normalize_with_depth(self,
+                                          obligation.param_env,
                                           obligation.cause.clone(),
                                           obligation.recursion_depth + 1,
                                           &impl_trait_ref);
@@ -2669,6 +2698,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let InferOk { obligations, .. } =
             self.infcx.eq_trait_refs(false,
                                      &obligation.cause,
+                                     obligation.param_env,
                                      impl_trait_ref.value.clone(),
                                      skol_obligation_trait_ref)
             .map_err(|e| {
@@ -2742,6 +2772,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         self.infcx.sub_poly_trait_refs(false,
                                        obligation.cause.clone(),
+                                       obligation.param_env,
                                        poly_trait_ref,
                                        obligation.predicate.to_poly_trait_ref())
             .map(|InferOk { obligations, .. }| self.inferred_obligations.extend(obligations))
@@ -2809,6 +2840,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         // A closure signature can contain associated types which
         // must be normalized.
         normalize_with_depth(self,
+                             obligation.param_env,
                              obligation.cause.clone(),
                              obligation.recursion_depth+1,
                              &trait_ref)
@@ -2821,6 +2853,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     fn impl_or_trait_obligations(&mut self,
                                  cause: ObligationCause<'tcx>,
                                  recursion_depth: usize,
+                                 param_env: ty::ParamEnv<'tcx>,
                                  def_id: DefId, // of impl or trait
                                  substs: &Substs<'tcx>, // for impl or trait
                                  skol_map: infer::SkolemizationMap<'tcx>,
@@ -2847,12 +2880,13 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
         let predicates = tcx.predicates_of(def_id);
         assert_eq!(predicates.parent, None);
         let predicates = predicates.predicates.iter().flat_map(|predicate| {
-            let predicate = normalize_with_depth(self, cause.clone(), recursion_depth,
+            let predicate = normalize_with_depth(self, param_env, cause.clone(), recursion_depth,
                                                  &predicate.subst(tcx, substs));
             predicate.obligations.into_iter().chain(
                 Some(Obligation {
                     cause: cause.clone(),
                     recursion_depth: recursion_depth,
+                    param_env,
                     predicate: predicate.value
                 }))
         }).collect();

src/librustc/traits/specialize/mod.rs

@@ -41,6 +41,7 @@ pub struct OverlapError {
 /// Given a subst for the requested impl, translate it to a subst
 /// appropriate for the actual item definition (whether it be in that impl,
 /// a parent impl, or the trait).
+///
 /// When we have selected one impl, but are actually using item definitions from
 /// a parent impl providing a default, we need a way to translate between the
 /// type parameters of the two impls. Here the `source_impl` is the one we've
@@ -73,6 +74,7 @@ pub struct OverlapError {
 /// *fulfillment* to relate the two impls, requiring that all projections are
 /// resolved.
 pub fn translate_substs<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                        param_env: ty::ParamEnv<'tcx>,
                                         source_impl: DefId,
                                         source_substs: &'tcx Substs<'tcx>,
                                         target_node: specialization_graph::Node)
@@ -91,7 +93,8 @@ pub fn translate_substs<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
                 return source_substs;
             }
 
-            fulfill_implication(infcx, source_trait_ref, target_impl).unwrap_or_else(|_| {
+            fulfill_implication(infcx, param_env, source_trait_ref, target_impl)
+                .unwrap_or_else(|_| {
                     bug!("When translating substitutions for specialization, the expected \
                           specializaiton failed to hold")
                 })
@@ -122,9 +125,10 @@ pub fn find_associated_item<'a, 'tcx>(
     let ancestors = trait_def.ancestors(tcx, impl_data.impl_def_id);
     match ancestors.defs(tcx, item.name, item.kind).next() {
         Some(node_item) => {
-            let substs = tcx.infer_ctxt(Reveal::All).enter(|infcx| {
+            let substs = tcx.infer_ctxt(()).enter(|infcx| {
+                let param_env = ty::ParamEnv::empty(Reveal::All);
                 let substs = substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
-                let substs = translate_substs(&infcx, impl_data.impl_def_id,
+                let substs = translate_substs(&infcx, param_env, impl_data.impl_def_id,
                                               substs, node_item.node);
                 let substs = infcx.tcx.erase_regions(&substs);
                 tcx.lift(&substs).unwrap_or_else(|| {
@@ -184,11 +188,14 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let impl1_trait_ref = tcx.impl_trait_ref(impl1_def_id).unwrap();
 
     // Create a infcx, taking the predicates of impl1 as assumptions:
-    let result = tcx.infer_ctxt(penv).enter(|infcx| {
+    let result = tcx.infer_ctxt(()).enter(|infcx| {
         // Normalize the trait reference. The WF rules ought to ensure
         // that this always succeeds.
         let impl1_trait_ref =
-            match traits::fully_normalize(&infcx, ObligationCause::dummy(), &impl1_trait_ref) {
+            match traits::fully_normalize(&infcx,
+                                          ObligationCause::dummy(),
+                                          penv,
+                                          &impl1_trait_ref) {
                 Ok(impl1_trait_ref) => impl1_trait_ref,
                 Err(err) => {
                     bug!("failed to fully normalize {:?}: {:?}", impl1_trait_ref, err);
@@ -196,7 +203,7 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             };
 
         // Attempt to prove that impl2 applies, given all of the above.
-        fulfill_implication(&infcx, impl1_trait_ref, impl2_def_id).is_ok()
+        fulfill_implication(&infcx, penv, impl1_trait_ref, impl2_def_id).is_ok()
     });
 
     tcx.specializes_cache.borrow_mut().insert(impl1_def_id, impl2_def_id, result);
@@ -209,18 +216,21 @@ pub fn specializes<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 /// `source_trait_ref` and those whose identity is determined via a where
 /// clause in the impl.
 fn fulfill_implication<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                       param_env: ty::ParamEnv<'tcx>,
                                        source_trait_ref: ty::TraitRef<'tcx>,
                                        target_impl: DefId)
                                        -> Result<&'tcx Substs<'tcx>, ()> {
     let selcx = &mut SelectionContext::new(&infcx);
     let target_substs = infcx.fresh_substs_for_item(DUMMY_SP, target_impl);
     let (target_trait_ref, mut obligations) = impl_trait_ref_and_oblig(selcx,
+                                                                       param_env,
                                                                        target_impl,
                                                                        target_substs);
 
     // do the impls unify? If not, no specialization.
     match infcx.eq_trait_refs(true,
                               &ObligationCause::dummy(),
+                              param_env,
                               source_trait_ref,
                               target_trait_ref) {
         Ok(InferOk { obligations: o, .. }) => {
@@ -250,7 +260,7 @@ fn fulfill_implication<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
                        source_trait_ref,
                        target_trait_ref,
                        errors,
-                       infcx.param_env.caller_bounds);
+                       param_env.caller_bounds);
                 Err(())
             }
 

src/librustc/traits/specialize/specialization_graph.rs

@@ -11,7 +11,7 @@
 use super::{OverlapError, specializes};
 
 use hir::def_id::DefId;
-use traits::{self, Reveal};
+use traits;
 use ty::{self, TyCtxt, TypeFoldable};
 use ty::fast_reject::{self, SimplifiedType};
 use std::rc::Rc;
@@ -109,7 +109,7 @@ impl<'a, 'gcx, 'tcx> Children {
             let possible_sibling = *slot;
 
             let tcx = tcx.global_tcx();
-            let (le, ge) = tcx.infer_ctxt(Reveal::UserFacing).enter(|infcx| {
+            let (le, ge) = tcx.infer_ctxt(()).enter(|infcx| {
                 let overlap = traits::overlapping_impls(&infcx,
                                                         possible_sibling,
                                                         impl_def_id);

src/librustc/traits/structural_impls.rs

@@ -341,6 +341,7 @@ impl<'tcx, O: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::Obligation<'tcx
             cause: self.cause.clone(),
             recursion_depth: self.recursion_depth,
             predicate: self.predicate.fold_with(folder),
+            param_env: self.param_env.fold_with(folder),
         }
     }
 

src/librustc/traits/trans/mod.rs

@@ -46,12 +46,14 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
 
             // Do the initial selection for the obligation. This yields the
             // shallow result we are looking for -- that is, what specific impl.
-            self.infer_ctxt(Reveal::All).enter(|infcx| {
+            self.infer_ctxt(()).enter(|infcx| {
                 let mut selcx = SelectionContext::new(&infcx);
 
+                let param_env = ty::ParamEnv::empty(Reveal::All);
                 let obligation_cause = ObligationCause::misc(span,
                                                              ast::DUMMY_NODE_ID);
                 let obligation = Obligation::new(obligation_cause,
+                                                 param_env,
                                                  trait_ref.to_poly_trait_predicate());
 
                 let selection = match selcx.select(&obligation) {

src/librustc/traits/util.rs

@@ -358,6 +358,7 @@ impl<'tcx,I:Iterator<Item=ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
 /// returning the resulting trait ref and all obligations that arise.
 /// The obligations are closed under normalization.
 pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tcx>,
+                                                param_env: ty::ParamEnv<'tcx>,
                                                 impl_def_id: DefId,
                                                 impl_substs: &Substs<'tcx>)
                                                 -> (ty::TraitRef<'tcx>,
@@ -368,14 +369,14 @@ pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a,
     let impl_trait_ref =
         impl_trait_ref.subst(selcx.tcx(), impl_substs);
     let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 } =
-        super::normalize(selcx, ObligationCause::dummy(), &impl_trait_ref);
+        super::normalize(selcx, param_env, ObligationCause::dummy(), &impl_trait_ref);
 
     let predicates = selcx.tcx().predicates_of(impl_def_id);
     let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
     let Normalized { value: predicates, obligations: normalization_obligations2 } =
-        super::normalize(selcx, ObligationCause::dummy(), &predicates);
+        super::normalize(selcx, param_env, ObligationCause::dummy(), &predicates);
     let impl_obligations =
-        predicates_for_generics(ObligationCause::dummy(), 0, &predicates);
+        predicates_for_generics(ObligationCause::dummy(), 0, param_env, &predicates);
 
     let impl_obligations: Vec<_> =
         impl_obligations.into_iter()
@@ -389,6 +390,7 @@ pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a,
 /// See `super::obligations_for_generics`
 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
                                      recursion_depth: usize,
+                                     param_env: ty::ParamEnv<'tcx>,
                                      generic_bounds: &ty::InstantiatedPredicates<'tcx>)
                                      -> Vec<PredicateObligation<'tcx>>
 {
@@ -398,18 +400,21 @@ pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
     generic_bounds.predicates.iter().map(|predicate| {
         Obligation { cause: cause.clone(),
                      recursion_depth: recursion_depth,
+                     param_env: param_env,
                      predicate: predicate.clone() }
     }).collect()
 }
 
 pub fn predicate_for_trait_ref<'tcx>(
     cause: ObligationCause<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     trait_ref: ty::TraitRef<'tcx>,
     recursion_depth: usize)
     -> PredicateObligation<'tcx>
 {
     Obligation {
         cause: cause,
+        param_env: param_env,
         recursion_depth: recursion_depth,
         predicate: trait_ref.to_predicate(),
     }
@@ -417,6 +422,7 @@ pub fn predicate_for_trait_ref<'tcx>(
 
 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     pub fn predicate_for_trait_def(self,
+                                   param_env: ty::ParamEnv<'tcx>,
                                    cause: ObligationCause<'tcx>,
                                    trait_def_id: DefId,
                                    recursion_depth: usize,
@@ -428,7 +434,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             def_id: trait_def_id,
             substs: self.mk_substs_trait(param_ty, ty_params)
         };
-        predicate_for_trait_ref(cause, trait_ref, recursion_depth)
+        predicate_for_trait_ref(cause, param_env, trait_ref, recursion_depth)
     }
 
     /// Cast a trait reference into a reference to one of its super

src/librustc/ty/context.rs

@@ -765,6 +765,18 @@ pub trait Lift<'tcx> {
     fn lift_to_tcx<'a, 'gcx>(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>) -> Option<Self::Lifted>;
 }
 
+impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
+    type Lifted = ty::ParamEnv<'tcx>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<ty::ParamEnv<'tcx>> {
+        self.caller_bounds.lift_to_tcx(tcx).and_then(|caller_bounds| {
+            Some(ty::ParamEnv {
+                reveal: self.reveal,
+                caller_bounds,
+            })
+        })
+    }
+}
+
 impl<'a, 'tcx> Lift<'tcx> for Ty<'a> {
     type Lifted = Ty<'tcx>;
     fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<Ty<'tcx>> {
@@ -851,6 +863,25 @@ impl<'a, 'tcx> Lift<'tcx> for &'a Slice<ExistentialPredicate<'a>> {
     }
 }
 
+impl<'a, 'tcx> Lift<'tcx> for &'a Slice<Predicate<'a>> {
+    type Lifted = &'tcx Slice<Predicate<'tcx>>;
+    fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>)
+        -> Option<&'tcx Slice<Predicate<'tcx>>> {
+        if self.is_empty() {
+            return Some(Slice::empty());
+        }
+        if tcx.interners.arena.in_arena(*self as *const _) {
+            return Some(unsafe { mem::transmute(*self) });
+        }
+        // Also try in the global tcx if we're not that.
+        if !tcx.is_global() {
+            self.lift_to_tcx(tcx.global_tcx())
+        } else {
+            None
+        }
+    }
+}
+
 pub mod tls {
     use super::{CtxtInterners, GlobalCtxt, TyCtxt};
 

src/librustc/ty/mod.rs

@@ -158,29 +158,6 @@ pub struct ImplHeader<'tcx> {
     pub predicates: Vec<Predicate<'tcx>>,
 }
 
-impl<'a, 'gcx, 'tcx> ImplHeader<'tcx> {
-    pub fn with_fresh_ty_vars(selcx: &mut traits::SelectionContext<'a, 'gcx, 'tcx>,
-                              impl_def_id: DefId)
-                              -> ImplHeader<'tcx>
-    {
-        let tcx = selcx.tcx();
-        let impl_substs = selcx.infcx().fresh_substs_for_item(DUMMY_SP, impl_def_id);
-
-        let header = ImplHeader {
-            impl_def_id: impl_def_id,
-            self_ty: tcx.type_of(impl_def_id),
-            trait_ref: tcx.impl_trait_ref(impl_def_id),
-            predicates: tcx.predicates_of(impl_def_id).predicates
-        }.subst(tcx, impl_substs);
-
-        let traits::Normalized { value: mut header, obligations } =
-            traits::normalize(selcx, traits::ObligationCause::dummy(), &header);
-
-        header.predicates.extend(obligations.into_iter().map(|o| o.predicate));
-        header
-    }
-}
-
 #[derive(Copy, Clone, Debug)]
 pub struct AssociatedItem {
     pub def_id: DefId,

src/librustc/ty/structural_impls.rs

@@ -466,6 +466,20 @@ impl<'tcx, T:TypeFoldable<'tcx>> TypeFoldable<'tcx> for ty::Binder<T> {
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for ty::ParamEnv<'tcx> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        ty::ParamEnv {
+            reveal: self.reveal,
+            caller_bounds: self.caller_bounds.fold_with(folder),
+        }
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        let &ty::ParamEnv { reveal: _, ref caller_bounds } = self;
+        caller_bounds.super_visit_with(visitor)
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Slice<ty::ExistentialPredicate<'tcx>> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         let v = self.iter().map(|p| p.fold_with(folder)).collect::<AccumulateVec<[_; 8]>>();
@@ -771,6 +785,17 @@ impl<'tcx> TypeFoldable<'tcx> for ty::GenericPredicates<'tcx> {
     }
 }
 
+impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Slice<ty::Predicate<'tcx>> {
+    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
+        let v = self.iter().map(|p| p.fold_with(folder)).collect::<AccumulateVec<[_; 8]>>();
+        folder.tcx().intern_predicates(&v)
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
+        self.iter().any(|p| p.visit_with(visitor))
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for ty::Predicate<'tcx> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         match *self {

src/librustc/ty/util.rs

@@ -170,11 +170,12 @@ impl<'tcx> ty::ParamEnv<'tcx> {
         ty::ParamEnv { reveal: Reveal::All, ..self }
     }
 
-    pub fn can_type_implement_copy<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
+    pub fn can_type_implement_copy<'a>(self,
+                                       tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                        self_type: Ty<'tcx>, span: Span)
-                                       -> Result<(), CopyImplementationError> {
+                                       -> Result<(), CopyImplementationError<'tcx>> {
         // FIXME: (@jroesch) float this code up
-        tcx.infer_ctxt(self.clone()).enter(|infcx| {
+        tcx.infer_ctxt(()).enter(|infcx| {
             let (adt, substs) = match self_type.sty {
                 ty::TyAdt(adt, substs) => (adt, substs),
                 _ => return Err(CopyImplementationError::NotAnAdt),
@@ -182,8 +183,8 @@ impl<'tcx> ty::ParamEnv<'tcx> {
 
             let field_implements_copy = |field: &ty::FieldDef| {
                 let cause = traits::ObligationCause::dummy();
-                match traits::fully_normalize(&infcx, cause, &field.ty(tcx, substs)) {
-                    Ok(ty) => !infcx.type_moves_by_default(ty, span),
+                match traits::fully_normalize(&infcx, cause, self, &field.ty(tcx, substs)) {
+                    Ok(ty) => !infcx.type_moves_by_default(self, ty, span),
                     Err(..) => false,
                 }
             };
@@ -963,8 +964,12 @@ fn is_copy_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 {
     let (param_env, ty) = query.into_parts();
     let trait_def_id = tcx.require_lang_item(lang_items::CopyTraitLangItem);
-    tcx.infer_ctxt(param_env)
-       .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
+    tcx.infer_ctxt(())
+       .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
+                                                       param_env,
+                                                       ty,
+                                                       trait_def_id,
+                                                       DUMMY_SP))
 }
 
 fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -973,8 +978,12 @@ fn is_sized_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 {
     let (param_env, ty) = query.into_parts();
     let trait_def_id = tcx.require_lang_item(lang_items::SizedTraitLangItem);
-    tcx.infer_ctxt(param_env)
-       .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
+    tcx.infer_ctxt(())
+       .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
+                                                       param_env,
+                                                       ty,
+                                                       trait_def_id,
+                                                       DUMMY_SP))
 }
 
 fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -983,8 +992,12 @@ fn is_freeze_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 {
     let (param_env, ty) = query.into_parts();
     let trait_def_id = tcx.require_lang_item(lang_items::FreezeTraitLangItem);
-    tcx.infer_ctxt(param_env)
-       .enter(|infcx| traits::type_known_to_meet_bound(&infcx, ty, trait_def_id, DUMMY_SP))
+    tcx.infer_ctxt(())
+       .enter(|infcx| traits::type_known_to_meet_bound(&infcx,
+                                                       param_env,
+                                                       ty,
+                                                       trait_def_id,
+                                                       DUMMY_SP))
 }
 
 fn needs_drop_raw<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,

src/librustc/ty/wf.rs

@@ -26,12 +26,14 @@ use middle::lang_items;
 /// make any progress at all. This is to prevent "livelock" where we
 /// say "$0 is WF if $0 is WF".
 pub fn obligations<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                   param_env: ty::ParamEnv<'tcx>,
                                    body_id: ast::NodeId,
                                    ty: Ty<'tcx>,
                                    span: Span)
                                    -> Option<Vec<traits::PredicateObligation<'tcx>>>
 {
     let mut wf = WfPredicates { infcx: infcx,
+                                param_env: param_env,
                                 body_id: body_id,
                                 span: span,
                                 out: vec![] };
@@ -50,23 +52,25 @@ pub fn obligations<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
 /// `trait Set<K:Eq>`, then the trait reference `Foo: Set<Bar>` is WF
 /// if `Bar: Eq`.
 pub fn trait_obligations<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                         param_env: ty::ParamEnv<'tcx>,
                                          body_id: ast::NodeId,
                                          trait_ref: &ty::TraitRef<'tcx>,
                                          span: Span)
                                          -> Vec<traits::PredicateObligation<'tcx>>
 {
-    let mut wf = WfPredicates { infcx: infcx, body_id: body_id, span: span, out: vec![] };
+    let mut wf = WfPredicates { infcx, param_env, body_id, span, out: vec![] };
     wf.compute_trait_ref(trait_ref);
     wf.normalize()
 }
 
 pub fn predicate_obligations<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
+                                             param_env: ty::ParamEnv<'tcx>,
                                              body_id: ast::NodeId,
                                              predicate: &ty::Predicate<'tcx>,
                                              span: Span)
                                              -> Vec<traits::PredicateObligation<'tcx>>
 {
-    let mut wf = WfPredicates { infcx: infcx, body_id: body_id, span: span, out: vec![] };
+    let mut wf = WfPredicates { infcx, param_env, body_id, span, out: vec![] };
 
     // (*) ok to skip binders, because wf code is prepared for it
     match *predicate {
@@ -126,6 +130,7 @@ pub enum ImpliedBound<'tcx> {
 /// the `ImpliedBound` type for more details.
 pub fn implied_bounds<'a, 'gcx, 'tcx>(
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     body_id: ast::NodeId,
     ty: Ty<'tcx>,
     span: Span)
@@ -148,7 +153,7 @@ pub fn implied_bounds<'a, 'gcx, 'tcx>(
         // than the ultimate set. (Note: normally there won't be
         // unresolved inference variables here anyway, but there might be
         // during typeck under some circumstances.)
-        let obligations = obligations(infcx, body_id, ty, span).unwrap_or(vec![]);
+        let obligations = obligations(infcx, param_env, body_id, ty, span).unwrap_or(vec![]);
 
         // From the full set of obligations, just filter down to the
         // region relationships.
@@ -231,6 +236,7 @@ fn implied_bounds_from_components<'tcx>(sub_region: ty::Region<'tcx>,
 
 struct WfPredicates<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
     body_id: ast::NodeId,
     span: Span,
     out: Vec<traits::PredicateObligation<'tcx>>,
@@ -244,11 +250,12 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
     fn normalize(&mut self) -> Vec<traits::PredicateObligation<'tcx>> {
         let cause = self.cause(traits::MiscObligation);
         let infcx = &mut self.infcx;
+        let param_env = self.param_env;
         self.out.iter()
                 .inspect(|pred| assert!(!pred.has_escaping_regions()))
                 .flat_map(|pred| {
                     let mut selcx = traits::SelectionContext::new(infcx);
-                    let pred = traits::normalize(&mut selcx, cause.clone(), pred);
+                    let pred = traits::normalize(&mut selcx, param_env, cause.clone(), pred);
                     once(pred.value).chain(pred.obligations)
                 })
                 .collect()
@@ -261,10 +268,12 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
         self.out.extend(obligations);
 
         let cause = self.cause(traits::MiscObligation);
+        let param_env = self.param_env;
         self.out.extend(
             trait_ref.substs.types()
                             .filter(|ty| !ty.has_escaping_regions())
                             .map(|ty| traits::Obligation::new(cause.clone(),
+                                                              param_env,
                                                               ty::Predicate::WellFormed(ty))));
     }
 
@@ -280,7 +289,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
         if !data.has_escaping_regions() {
             let predicate = data.trait_ref.to_predicate();
             let cause = self.cause(traits::ProjectionWf(data));
-            self.out.push(traits::Obligation::new(cause, predicate));
+            self.out.push(traits::Obligation::new(cause, self.param_env, predicate));
         }
     }
 
@@ -291,7 +300,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                 def_id: self.infcx.tcx.require_lang_item(lang_items::SizedTraitLangItem),
                 substs: self.infcx.tcx.mk_substs_trait(subty, &[]),
             };
-            self.out.push(traits::Obligation::new(cause, trait_ref.to_predicate()));
+            self.out.push(traits::Obligation::new(cause, self.param_env, trait_ref.to_predicate()));
         }
     }
 
@@ -301,6 +310,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
     /// in which case we are not able to simplify at all.
     fn compute(&mut self, ty0: Ty<'tcx>) -> bool {
         let mut subtys = ty0.walk();
+        let param_env = self.param_env;
         while let Some(ty) = subtys.next() {
             match ty.sty {
                 ty::TyBool |
@@ -350,6 +360,7 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                         self.out.push(
                             traits::Obligation::new(
                                 cause,
+                                param_env,
                                 ty::Predicate::TypeOutlives(
                                     ty::Binder(
                                         ty::OutlivesPredicate(mt.ty, r)))));
@@ -389,12 +400,12 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
                     // checking those
 
                     let cause = self.cause(traits::MiscObligation);
-
                     let component_traits =
                         data.auto_traits().chain(data.principal().map(|p| p.def_id()));
                     self.out.extend(
                         component_traits.map(|did| traits::Obligation::new(
                             cause.clone(),
+                            param_env,
                             ty::Predicate::ObjectSafe(did)
                         ))
                     );
@@ -422,7 +433,9 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
 
                         let cause = self.cause(traits::MiscObligation);
                         self.out.push( // ...not the type we started from, so we made progress.
-                            traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
+                            traits::Obligation::new(cause,
+                                                    self.param_env,
+                                                    ty::Predicate::WellFormed(ty)));
                     } else {
                         // Yes, resolved, proceed with the
                         // result. Should never return false because
@@ -448,7 +461,9 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
         let cause = self.cause(traits::ItemObligation(def_id));
         predicates.predicates
                   .into_iter()
-                  .map(|pred| traits::Obligation::new(cause.clone(), pred))
+                  .map(|pred| traits::Obligation::new(cause.clone(),
+                                                      self.param_env,
+                                                      pred))
                   .filter(|pred| !pred.has_escaping_regions())
                   .collect()
     }
@@ -497,7 +512,9 @@ impl<'a, 'gcx, 'tcx> WfPredicates<'a, 'gcx, 'tcx> {
             for implicit_bound in implicit_bounds {
                 let cause = self.cause(traits::ObjectTypeBound(ty, explicit_bound));
                 let outlives = ty::Binder(ty::OutlivesPredicate(explicit_bound, implicit_bound));
-                self.out.push(traits::Obligation::new(cause, outlives.to_predicate()));
+                self.out.push(traits::Obligation::new(cause,
+                                                      self.param_env,
+                                                      outlives.to_predicate()));
             }
         }
     }

src/librustc_borrowck/borrowck/check_loans.rs

@@ -90,7 +90,7 @@ struct CheckLoanCtxt<'a, 'tcx: 'a> {
     dfcx_loans: &'a LoanDataFlow<'a, 'tcx>,
     move_data: &'a move_data::FlowedMoveData<'a, 'tcx>,
     all_loans: &'a [Loan<'tcx>],
-    param_env: &'a ty::ParamEnv<'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
 }
 
 impl<'a, 'tcx> euv::Delegate<'tcx> for CheckLoanCtxt<'a, 'tcx> {
@@ -191,15 +191,17 @@ pub fn check_loans<'a, 'b, 'c, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                                      body: &hir::Body) {
     debug!("check_loans(body id={})", body.value.id);
 
+    let def_id = bccx.tcx.hir.body_owner_def_id(body.id());
     let infcx = bccx.tcx.borrowck_fake_infer_ctxt(body.id());
+    let param_env = bccx.tcx.param_env(def_id);
     let mut clcx = CheckLoanCtxt {
         bccx: bccx,
         dfcx_loans: dfcx_loans,
         move_data: move_data,
         all_loans: all_loans,
-        param_env: &infcx.param_env
+        param_env,
     };
-    euv::ExprUseVisitor::new(&mut clcx, &bccx.region_maps, &infcx).consume_body(body);
+    euv::ExprUseVisitor::new(&mut clcx, &bccx.region_maps, &infcx, param_env).consume_body(body);
 }
 
 #[derive(PartialEq)]

src/librustc_borrowck/borrowck/gather_loans/mod.rs

@@ -38,9 +38,10 @@ mod move_error;
 
 pub fn gather_loans_in_fn<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                                     body: hir::BodyId)
-                                    -> (Vec<Loan<'tcx>>,
-                                        move_data::MoveData<'tcx>) {
+                                    -> (Vec<Loan<'tcx>>, move_data::MoveData<'tcx>) {
+    let def_id = bccx.tcx.hir.body_owner_def_id(body);
     let infcx = bccx.tcx.borrowck_fake_infer_ctxt(body);
+    let param_env = bccx.tcx.param_env(def_id);
     let mut glcx = GatherLoanCtxt {
         bccx: bccx,
         infcx: &infcx,
@@ -51,7 +52,7 @@ pub fn gather_loans_in_fn<'a, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
     };
 
     let body = glcx.bccx.tcx.hir.body(body);
-    euv::ExprUseVisitor::new(&mut glcx, &bccx.region_maps, &infcx).consume_body(body);
+    euv::ExprUseVisitor::new(&mut glcx, &bccx.region_maps, &infcx, param_env).consume_body(body);
 
     glcx.report_potential_errors();
     let GatherLoanCtxt { all_loans, move_data, .. } = glcx;

src/librustc_borrowck/borrowck/mod.rs

@@ -526,7 +526,7 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                      lp: &LoanPath<'tcx>,
                                      the_move: &move_data::Move,
                                      moved_lp: &LoanPath<'tcx>,
-                                     _param_env: &ty::ParamEnv<'tcx>) {
+                                     _param_env: ty::ParamEnv<'tcx>) {
         let (verb, verb_participle) = match use_kind {
             MovedInUse => ("use", "used"),
             MovedInCapture => ("capture", "captured"),

src/librustc_const_eval/check_match.rs

@@ -517,11 +517,11 @@ fn check_legality_of_move_bindings(cx: &MatchVisitor,
 ///
 /// FIXME: this should be done by borrowck.
 fn check_for_mutation_in_guard(cx: &MatchVisitor, guard: &hir::Expr) {
-    cx.tcx.infer_ctxt((cx.tables, cx.param_env)).enter(|infcx| {
+    cx.tcx.infer_ctxt(cx.tables).enter(|infcx| {
         let mut checker = MutationChecker {
             cx: cx,
         };
-        ExprUseVisitor::new(&mut checker, cx.region_maps, &infcx).walk_expr(guard);
+        ExprUseVisitor::new(&mut checker, cx.region_maps, &infcx, cx.param_env).walk_expr(guard);
     });
 }
 

src/librustc_const_eval/eval.rs

@@ -483,9 +483,11 @@ fn resolve_trait_associated_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     debug!("resolve_trait_associated_const: trait_ref={:?}",
            trait_ref);
 
-    tcx.infer_ctxt(Reveal::UserFacing).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
+        let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
         let mut selcx = traits::SelectionContext::new(&infcx);
         let obligation = traits::Obligation::new(traits::ObligationCause::dummy(),
+                                                 param_env,
                                                  trait_ref.to_poly_trait_predicate());
         let selection = match selcx.select(&obligation) {
             Ok(Some(vtable)) => vtable,

src/librustc_lint/builtin.rs

@@ -951,12 +951,13 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnconditionalRecursion {
                     let trait_ref = ty::TraitRef::from_method(tcx, trait_def_id, callee_substs);
                     let trait_ref = ty::Binder(trait_ref);
                     let span = tcx.hir.span(expr_id);
+                    let param_env = tcx.param_env(method.def_id);
                     let obligation =
                         traits::Obligation::new(traits::ObligationCause::misc(span, expr_id),
+                                                param_env,
                                                 trait_ref.to_poly_trait_predicate());
 
-                    let param_env = tcx.param_env(method.def_id);
-                    tcx.infer_ctxt(param_env).enter(|infcx| {
+                    tcx.infer_ctxt(()).enter(|infcx| {
                         let mut selcx = traits::SelectionContext::new(&infcx);
                         match selcx.select(&obligation) {
                             // The method comes from a `T: Trait` bound.

src/librustc_mir/build/mod.rs

@@ -171,8 +171,7 @@ fn create_constructor_shim<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 {
     let span = tcx.hir.span(ctor_id);
     if let hir::VariantData::Tuple(ref fields, ctor_id) = *v {
-        let pe = tcx.param_env(tcx.hir.local_def_id(ctor_id));
-        tcx.infer_ctxt(pe).enter(|infcx| {
+        tcx.infer_ctxt(()).enter(|infcx| {
             let (mut mir, src) =
                 shim::build_adt_ctor(&infcx, ctor_id, fields, span);
 

src/librustc_mir/hair/cx/mod.rs

@@ -35,6 +35,7 @@ use std::rc::Rc;
 pub struct Cx<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     tcx: TyCtxt<'a, 'gcx, 'tcx>,
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+    pub param_env: ty::ParamEnv<'tcx>,
     pub region_maps: Rc<RegionMaps>,
 
     /// This is `Constness::Const` if we are compiling a `static`,
@@ -64,6 +65,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
         let src_id = src.item_id();
         let src_def_id = tcx.hir.local_def_id(src_id);
 
+        let param_env = tcx.param_env(src_def_id);
         let region_maps = tcx.region_maps(src_def_id);
 
         let attrs = tcx.hir.attrs(src_id);
@@ -80,7 +82,7 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
         // Constants and const fn's always need overflow checks.
         check_overflow |= constness == hir::Constness::Const;
 
-        Cx { tcx, infcx, region_maps, constness, src, check_overflow }
+        Cx { tcx, infcx, param_env, region_maps, constness, src, check_overflow }
     }
 }
 
@@ -169,12 +171,12 @@ impl<'a, 'gcx, 'tcx> Cx<'a, 'gcx, 'tcx> {
     }
 
     pub fn needs_drop(&mut self, ty: Ty<'tcx>) -> bool {
-        let ty = self.tcx.lift_to_global(&ty).unwrap_or_else(|| {
-            bug!("MIR: Cx::needs_drop({}) got \
+        let (ty, param_env) = self.tcx.lift_to_global(&(ty, self.param_env)).unwrap_or_else(|| {
+            bug!("MIR: Cx::needs_drop({:?}, {:?}) got \
                   type with inference types/regions",
-                 ty);
+                 ty, self.param_env);
         });
-        ty.needs_drop(self.tcx.global_tcx(), self.infcx.param_env)
+        ty.needs_drop(self.tcx.global_tcx(), param_env)
     }
 
     pub fn tcx(&self) -> TyCtxt<'a, 'gcx, 'tcx> {

src/librustc_mir/transform/qualify_consts.rs

@@ -998,10 +998,13 @@ impl MirPass for QualifyAndPromoteConstants {
         // Statics must be Sync.
         if mode == Mode::Static {
             let ty = mir.return_ty;
-            tcx.infer_ctxt(Reveal::UserFacing).enter(|infcx| {
+            tcx.infer_ctxt(()).enter(|infcx| {
+                let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
                 let cause = traits::ObligationCause::new(mir.span, id, traits::SharedStatic);
                 let mut fulfillment_cx = traits::FulfillmentContext::new();
-                fulfillment_cx.register_bound(&infcx, ty,
+                fulfillment_cx.register_bound(&infcx,
+                                              param_env,
+                                              ty,
                                               tcx.require_lang_item(lang_items::SyncTraitLangItem),
                                               cause);
                 if let Err(err) = fulfillment_cx.select_all_or_error(&infcx) {

src/librustc_mir/transform/type_check.rs

@@ -320,6 +320,7 @@ impl<'a, 'b, 'gcx, 'tcx> TypeVerifier<'a, 'b, 'gcx, 'tcx> {
 
 pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+    param_env: ty::ParamEnv<'gcx>,
     fulfillment_cx: traits::FulfillmentContext<'tcx>,
     last_span: Span,
     body_id: ast::NodeId,
@@ -327,12 +328,16 @@ pub struct TypeChecker<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 }
 
 impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
-    fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>, body_id: ast::NodeId) -> Self {
+    fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
+           body_id: ast::NodeId,
+           param_env: ty::ParamEnv<'gcx>)
+           -> Self {
         TypeChecker {
             infcx: infcx,
             fulfillment_cx: traits::FulfillmentContext::new(),
             last_span: DUMMY_SP,
-            body_id: body_id,
+            body_id,
+            param_env,
             reported_errors: FxHashSet(),
         }
     }
@@ -351,14 +356,14 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
     fn sub_types(&mut self, sup: Ty<'tcx>, sub: Ty<'tcx>)
                  -> infer::UnitResult<'tcx>
     {
-        self.infcx.sub_types(false, &self.misc(self.last_span), sup, sub)
+        self.infcx.sub_types(false, &self.misc(self.last_span), self.param_env, sup, sub)
             .map(|ok| self.register_infer_ok_obligations(ok))
     }
 
     fn eq_types(&mut self, span: Span, a: Ty<'tcx>, b: Ty<'tcx>)
                 -> infer::UnitResult<'tcx>
     {
-        self.infcx.eq_types(false, &self.misc(span), a, b)
+        self.infcx.eq_types(false, &self.misc(span), self.param_env, a, b)
             .map(|ok| self.register_infer_ok_obligations(ok))
     }
 
@@ -665,7 +670,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
 
         let span = local_decl.source_info.span;
         let ty = local_decl.ty;
-        if !ty.is_sized(self.tcx().global_tcx(), self.infcx.param_env(), span) {
+        if !ty.is_sized(self.tcx().global_tcx(), self.param_env, span) {
             // in current MIR construction, all non-control-flow rvalue
             // expressions evaluate through `as_temp` or `into` a return
             // slot or local, so to find all unsized rvalues it is enough
@@ -706,7 +711,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
         let mut selcx = traits::SelectionContext::new(self.infcx);
         let cause = traits::ObligationCause::misc(self.last_span, ast::CRATE_NODE_ID);
         let traits::Normalized { value, obligations } =
-            traits::normalize(&mut selcx, cause, value);
+            traits::normalize(&mut selcx, self.param_env, cause, value);
 
         debug!("normalize: value={:?} obligations={:?}",
                value,
@@ -752,8 +757,8 @@ impl MirPass for TypeckMir {
             return;
         }
         let param_env = tcx.param_env(def_id);
-        tcx.infer_ctxt(param_env).enter(|infcx| {
-            let mut checker = TypeChecker::new(&infcx, item_id);
+        tcx.infer_ctxt(()).enter(|infcx| {
+            let mut checker = TypeChecker::new(&infcx, item_id, param_env);
             {
                 let mut verifier = TypeVerifier::new(&mut checker, mir);
                 verifier.visit_mir(mir);

src/librustc_passes/consts.rs

@@ -139,10 +139,10 @@ impl<'a, 'tcx> Visitor<'tcx> for CheckCrateVisitor<'a, 'tcx> {
         }
 
         let outer_penv = self.tcx.infer_ctxt(body_id).enter(|infcx| {
-            let param_env = infcx.param_env.clone();
+            let param_env = self.tcx.param_env(item_def_id);
             let outer_penv = mem::replace(&mut self.param_env, param_env);
             let region_maps = &self.tcx.region_maps(item_def_id);
-            euv::ExprUseVisitor::new(self, region_maps, &infcx).consume_body(body);
+            euv::ExprUseVisitor::new(self, region_maps, &infcx, param_env).consume_body(body);
             outer_penv
         });
 

src/librustc_trans/context.rs

@@ -23,12 +23,12 @@ use monomorphize::Instance;
 use partitioning::CodegenUnit;
 use type_::Type;
 use rustc_data_structures::base_n;
+use rustc::session::config::{self, NoDebugInfo};
+use rustc::session::Session;
 use rustc::ty::subst::Substs;
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::layout::{LayoutCx, LayoutError, LayoutTyper, TyLayout};
-use session::config::{self, NoDebugInfo};
-use session::Session;
-use util::nodemap::{NodeSet, DefIdMap, FxHashMap};
+use rustc::util::nodemap::{NodeSet, DefIdMap, FxHashMap};
 
 use std::ffi::{CStr, CString};
 use std::cell::{Cell, RefCell};

src/librustc_typeck/check/autoderef.rs

@@ -118,13 +118,16 @@ impl<'a, 'gcx, 'tcx> Autoderef<'a, 'gcx, 'tcx> {
         let cause = traits::ObligationCause::misc(self.span, self.fcx.body_id);
 
         let mut selcx = traits::SelectionContext::new(self.fcx);
-        let obligation = traits::Obligation::new(cause.clone(), trait_ref.to_predicate());
+        let obligation = traits::Obligation::new(cause.clone(),
+                                                 self.fcx.param_env,
+                                                 trait_ref.to_predicate());
         if !selcx.evaluate_obligation(&obligation) {
             debug!("overloaded_deref_ty: cannot match obligation");
             return None;
         }
 
         let normalized = traits::normalize_projection_type(&mut selcx,
+                                                           self.fcx.param_env,
                                                            ty::ProjectionTy::from_ref_and_name(
                                                                tcx,
                                                                trait_ref,

src/librustc_typeck/check/cast.rs

@@ -555,6 +555,6 @@ impl<'a, 'gcx, 'tcx> CastCheck<'tcx> {
 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     fn type_is_known_to_be_sized(&self, ty: Ty<'tcx>, span: Span) -> bool {
         let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem);
-        traits::type_known_to_meet_bound(self, ty, lang_item, span)
+        traits::type_known_to_meet_bound(self, self.param_env, ty, lang_item, span)
     }
 }

src/librustc_typeck/check/closure.rs

@@ -81,9 +81,11 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         let fn_sig = self.liberate_late_bound_regions(expr_def_id, &sig);
         let fn_sig = self.inh.normalize_associated_types_in(body.value.span,
-                                                            body.value.id, &fn_sig);
+                                                            body.value.id,
+                                                            self.param_env,
+                                                            &fn_sig);
 
-        check_fn(self, fn_sig, decl, expr.id, body);
+        check_fn(self, self.param_env, fn_sig, decl, expr.id, body);
 
         // Tuple up the arguments and insert the resulting function type into
         // the `closures` table.

src/librustc_typeck/check/coercion.rs

@@ -137,9 +137,9 @@ impl<'f, 'gcx, 'tcx> Coerce<'f, 'gcx, 'tcx> {
         self.commit_if_ok(|_| {
             let trace = TypeTrace::types(&self.cause, false, a, b);
             if self.use_lub {
-                self.lub(false, trace, &a, &b)
+                self.lub(false, trace, self.fcx.param_env, &a, &b)
             } else {
-                self.sub(false, trace, &a, &b)
+                self.sub(false, trace, self.fcx.param_env, &a, &b)
             }
         })
     }
@@ -511,9 +511,12 @@ impl<'f, 'gcx, 'tcx> Coerce<'f, 'gcx, 'tcx> {
 
         // Create an obligation for `Source: CoerceUnsized<Target>`.
         let cause = ObligationCause::misc(self.cause.span, self.body_id);
-        queue.push_back(self.tcx
-            .predicate_for_trait_def(cause, coerce_unsized_did, 0,
-                                     coerce_source, &[coerce_target]));
+        queue.push_back(self.tcx.predicate_for_trait_def(self.fcx.param_env,
+                                                         cause,
+                                                         coerce_unsized_did,
+                                                         0,
+                                                         coerce_source,
+                                                         &[coerce_target]));
 
         // Keep resolving `CoerceUnsized` and `Unsize` predicates to avoid
         // emitting a coercion in cases like `Foo<$1>` -> `Foo<$2>`, where
@@ -775,13 +778,13 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         match (&prev_ty.sty, &new_ty.sty) {
             (&ty::TyFnDef(a_def_id, a_substs, a_fty), &ty::TyFnDef(b_def_id, b_substs, b_fty)) => {
                 // The signature must always match.
-                let fty = self.lub(true, trace.clone(), &a_fty, &b_fty)
+                let fty = self.lub(true, trace.clone(), self.param_env, &a_fty, &b_fty)
                               .map(|ok| self.register_infer_ok_obligations(ok))?;
 
                 if a_def_id == b_def_id {
                     // Same function, maybe the parameters match.
                     let substs = self.commit_if_ok(|_| {
-                        self.lub(true, trace.clone(), &a_substs, &b_substs)
+                        self.lub(true, trace.clone(), self.param_env, &a_substs, &b_substs)
                             .map(|ok| self.register_infer_ok_obligations(ok))
                     });
 
@@ -850,7 +853,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
             if !noop {
                 return self.commit_if_ok(|_| {
-                    self.lub(true, trace.clone(), &prev_ty, &new_ty)
+                    self.lub(true, trace.clone(), self.param_env, &prev_ty, &new_ty)
                         .map(|ok| self.register_infer_ok_obligations(ok))
                 });
             }
@@ -863,7 +866,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     Err(e)
                 } else {
                     self.commit_if_ok(|_| {
-                        self.lub(true, trace, &prev_ty, &new_ty)
+                        self.lub(true, trace, self.param_env, &prev_ty, &new_ty)
                             .map(|ok| self.register_infer_ok_obligations(ok))
                     })
                 }
@@ -1106,7 +1109,7 @@ impl<'gcx, 'tcx, 'exprs, E> CoerceMany<'gcx, 'tcx, 'exprs, E>
             // Another example is `break` with no argument expression.
             assert!(expression_ty.is_nil());
             assert!(expression_ty.is_nil(), "if let hack without unit type");
-            fcx.eq_types(label_expression_as_expected, cause, expression_ty, self.merged_ty())
+            fcx.eq_types(label_expression_as_expected, cause, fcx.param_env, expression_ty, self.merged_ty())
                .map(|infer_ok| {
                    fcx.register_infer_ok_obligations(infer_ok);
                    expression_ty

src/librustc_typeck/check/compare_method.rs

@@ -219,12 +219,12 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                          param_env,
                                                          normalize_cause.clone());
 
-    tcx.infer_ctxt(param_env).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
         let inh = Inherited::new(infcx, impl_m.def_id);
         let infcx = &inh.infcx;
 
         debug!("compare_impl_method: caller_bounds={:?}",
-               infcx.param_env.caller_bounds);
+               param_env.caller_bounds);
 
         let mut selcx = traits::SelectionContext::new(&infcx);
 
@@ -234,10 +234,10 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                        &ty::Binder(impl_m_own_bounds.predicates));
         for predicate in impl_m_own_bounds {
             let traits::Normalized { value: predicate, obligations } =
-                traits::normalize(&mut selcx, normalize_cause.clone(), &predicate);
+                traits::normalize(&mut selcx, param_env, normalize_cause.clone(), &predicate);
 
             inh.register_predicates(obligations);
-            inh.register_predicate(traits::Obligation::new(cause.clone(), predicate));
+            inh.register_predicate(traits::Obligation::new(cause.clone(), param_env, predicate));
         }
 
         // We now need to check that the signature of the impl method is
@@ -270,6 +270,7 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         let impl_sig =
             inh.normalize_associated_types_in(impl_m_span,
                                               impl_m_node_id,
+                                              param_env,
                                               &impl_sig);
         let impl_fty = tcx.mk_fn_ptr(ty::Binder(impl_sig));
         debug!("compare_impl_method: impl_fty={:?}", impl_fty);
@@ -282,12 +283,13 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         let trait_sig =
             inh.normalize_associated_types_in(impl_m_span,
                                               impl_m_node_id,
+                                              param_env,
                                               &trait_sig);
         let trait_fty = tcx.mk_fn_ptr(ty::Binder(trait_sig));
 
         debug!("compare_impl_method: trait_fty={:?}", trait_fty);
 
-        let sub_result = infcx.sub_types(false, &cause, impl_fty, trait_fty)
+        let sub_result = infcx.sub_types(false, &cause, param_env, impl_fty, trait_fty)
                               .map(|InferOk { obligations, .. }| {
                                   inh.register_predicates(obligations);
                               });
@@ -298,6 +300,7 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                    trait_fty);
 
             let (impl_err_span, trait_err_span) = extract_spans_for_error_reporting(&infcx,
+                                                                                    param_env,
                                                                                     &terr,
                                                                                     &cause,
                                                                                     impl_m,
@@ -345,11 +348,10 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             // pass around temporarily.
             let region_maps = RegionMaps::new();
             let mut free_regions = FreeRegionMap::new();
-            free_regions.relate_free_regions_from_predicates(
-                &infcx.param_env.caller_bounds);
+            free_regions.relate_free_regions_from_predicates(&param_env.caller_bounds);
             infcx.resolve_regions_and_report_errors(impl_m.def_id, &region_maps, &free_regions);
         } else {
-            let fcx = FnCtxt::new(&inh, impl_m_node_id);
+            let fcx = FnCtxt::new(&inh, param_env, impl_m_node_id);
             fcx.regionck_item(impl_m_node_id, impl_m_span, &[]);
         }
 
@@ -400,6 +402,7 @@ fn check_region_bounds_on_impl_method<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 }
 
 fn extract_spans_for_error_reporting<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a, 'gcx, 'tcx>,
+                                                     param_env: ty::ParamEnv<'tcx>,
                                                      terr: &TypeError,
                                                      cause: &ObligationCause<'tcx>,
                                                      impl_m: &ty::AssociatedItem,
@@ -458,14 +461,21 @@ fn extract_spans_for_error_reporting<'a, 'gcx, 'tcx>(infcx: &infer::InferCtxt<'a
                          .zip(impl_m_iter)
                          .zip(trait_m_iter)
                          .filter_map(|(((impl_arg_ty, trait_arg_ty), impl_arg), trait_arg)| {
-                             match infcx.sub_types(true, &cause, trait_arg_ty, impl_arg_ty) {
+                             match infcx.sub_types(true,
+                                                   &cause,
+                                                   param_env,
+                                                   trait_arg_ty,
+                                                   impl_arg_ty) {
                                  Ok(_) => None,
                                  Err(_) => Some((impl_arg.span, Some(trait_arg.span))),
                              }
                          })
                          .next()
                          .unwrap_or_else(|| {
-                             if infcx.sub_types(false, &cause, impl_sig.output(),
+                             if infcx.sub_types(false,
+                                                &cause,
+                                                param_env,
+                                                impl_sig.output(),
                                                 trait_sig.output())
                                      .is_err() {
                                          (impl_m_output.span(), Some(trait_m_output.span()))
@@ -714,7 +724,8 @@ pub fn compare_const_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                     impl_trait_ref: ty::TraitRef<'tcx>) {
     debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
 
-    tcx.infer_ctxt(Reveal::UserFacing).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
+        let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
         let inh = Inherited::new(infcx, impl_c.def_id);
         let infcx = &inh.infcx;
 
@@ -737,17 +748,19 @@ pub fn compare_const_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // There is no "body" here, so just pass dummy id.
         let impl_ty = inh.normalize_associated_types_in(impl_c_span,
                                                         impl_c_node_id,
+                                                        param_env,
                                                         &impl_ty);
 
         debug!("compare_const_impl: impl_ty={:?}", impl_ty);
 
         let trait_ty = inh.normalize_associated_types_in(impl_c_span,
                                                          impl_c_node_id,
+                                                         param_env,
                                                          &trait_ty);
 
         debug!("compare_const_impl: trait_ty={:?}", trait_ty);
 
-        let err = infcx.sub_types(false, &cause, impl_ty, trait_ty)
+        let err = infcx.sub_types(false, &cause, param_env, impl_ty, trait_ty)
             .map(|ok| inh.register_infer_ok_obligations(ok));
 
         if let Err(terr) = err {
@@ -795,7 +808,7 @@ pub fn compare_const_impl<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             return;
         }
 
-        let fcx = FnCtxt::new(&inh, impl_c_node_id);
+        let fcx = FnCtxt::new(&inh, param_env, impl_c_node_id);
         fcx.regionck_item(impl_c_node_id, impl_c_span, &[]);
     });
 }

src/librustc_typeck/check/demand.rs

@@ -27,7 +27,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     // they don't.
     pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
         let cause = self.misc(sp);
-        match self.sub_types(false, &cause, actual, expected) {
+        match self.sub_types(false, &cause, self.param_env, actual, expected) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
             },
@@ -54,7 +54,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                                      cause: &ObligationCause<'tcx>,
                                      expected: Ty<'tcx>,
                                      actual: Ty<'tcx>) -> Option<DiagnosticBuilder<'tcx>> {
-        match self.eq_types(false, cause, actual, expected) {
+        match self.eq_types(false, cause, self.param_env, actual, expected) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
                 None

src/librustc_typeck/check/dropck.rs

@@ -79,8 +79,8 @@ fn ensure_drop_params_and_item_params_correspond<'a, 'tcx>(
 
     // check that the impl type can be made to match the trait type.
 
+    tcx.infer_ctxt(()).enter(|ref infcx| {
         let impl_param_env = tcx.param_env(self_type_did);
-    tcx.infer_ctxt(impl_param_env).enter(|ref infcx| {
         let tcx = infcx.tcx;
         let mut fulfillment_cx = traits::FulfillmentContext::new();
 
@@ -92,7 +92,7 @@ fn ensure_drop_params_and_item_params_correspond<'a, 'tcx>(
         let fresh_impl_self_ty = drop_impl_ty.subst(tcx, fresh_impl_substs);
 
         let cause = &ObligationCause::misc(drop_impl_span, drop_impl_node_id);
-        match infcx.eq_types(true, cause, named_type, fresh_impl_self_ty) {
+        match infcx.eq_types(true, cause, impl_param_env, named_type, fresh_impl_self_ty) {
             Ok(InferOk { obligations, .. }) => {
                 fulfillment_cx.register_predicate_obligations(infcx, obligations);
             }

src/librustc_typeck/check/method/confirm.rs

@@ -340,7 +340,7 @@ impl<'a, 'gcx, 'tcx> ConfirmContext<'a, 'gcx, 'tcx> {
     }
 
     fn unify_receivers(&mut self, self_ty: Ty<'tcx>, method_self_ty: Ty<'tcx>) {
-        match self.sub_types(false, &self.misc(self.span), self_ty, method_self_ty) {
+        match self.sub_types(false, &self.misc(self.span), self.param_env, self_ty, method_self_ty) {
             Ok(InferOk { obligations, value: () }) => {
                 self.register_predicates(obligations);
             }

src/librustc_typeck/check/method/mod.rs

@@ -205,7 +205,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // Construct an obligation
         let poly_trait_ref = trait_ref.to_poly_trait_ref();
         let obligation =
-            traits::Obligation::misc(span, self.body_id, poly_trait_ref.to_predicate());
+            traits::Obligation::misc(span,
+                                     self.body_id,
+                                     self.param_env,
+                                     poly_trait_ref.to_predicate());
 
         // Now we want to know if this can be matched
         let mut selcx = traits::SelectionContext::new(self);
@@ -262,14 +265,18 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         assert!(!bounds.has_escaping_regions());
 
         let cause = traits::ObligationCause::misc(span, self.body_id);
-        obligations.extend(traits::predicates_for_generics(cause.clone(), &bounds));
+        obligations.extend(traits::predicates_for_generics(cause.clone(),
+                                                           self.param_env,
+                                                           &bounds));
 
         // Also add an obligation for the method type being well-formed.
         let method_ty = tcx.mk_fn_ptr(ty::Binder(fn_sig));
         debug!("lookup_in_trait_adjusted: matched method method_ty={:?} obligation={:?}",
                method_ty,
                obligation);
-        obligations.push(traits::Obligation::new(cause, ty::Predicate::WellFormed(method_ty)));
+        obligations.push(traits::Obligation::new(cause,
+                                                 self.param_env,
+                                                 ty::Predicate::WellFormed(method_ty)));
 
         let callee = MethodCallee {
             def_id: def_id,

src/librustc_typeck/check/method/probe.rs

@@ -540,7 +540,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
             let mut selcx = &mut traits::SelectionContext::new(self.fcx);
             let traits::Normalized { value: xform_self_ty, obligations } =
-                traits::normalize(selcx, cause, &xform_self_ty);
+                traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
             debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}",
                    xform_self_ty);
 
@@ -679,7 +679,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                     let output = fty.output().subst(self.tcx, substs);
                     let (output, _) = self.replace_late_bound_regions_with_fresh_var(
                         self.span, infer::FnCall, &output);
-                    self.can_sub_types(output, expected).is_ok()
+                    self.can_sub_types(self.param_env, output, expected).is_ok()
                 })
             }
             _ => false,
@@ -751,7 +751,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             let cause = traits::ObligationCause::misc(self.span, self.body_id);
             let mut selcx = &mut traits::SelectionContext::new(self.fcx);
             let traits::Normalized { value: xform_self_ty, obligations } =
-                traits::normalize(selcx, cause, &xform_self_ty);
+                traits::normalize(selcx, self.param_env, cause, &xform_self_ty);
 
             debug!("xform_self_ty={:?}", xform_self_ty);
 
@@ -885,7 +885,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
                        substs,
                        bound);
 
-                if self.can_equate(&step.self_ty, &bound.self_ty()).is_ok() {
+                if self.can_equate(self.param_env, &step.self_ty, &bound.self_ty()).is_ok() {
                     let xform_self_ty = self.xform_self_ty(&item, bound.self_ty(), bound.substs);
 
                     debug!("assemble_projection_candidates: bound={:?} xform_self_ty={:?}",
@@ -1145,6 +1145,7 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             // First check that the self type can be related.
             let sub_obligations = match self.sub_types(false,
                                                        &ObligationCause::dummy(),
+                                                       self.param_env,
                                                        self_ty,
                                                        probe.xform_self_ty) {
                 Ok(InferOk { obligations, value: () }) => obligations,
@@ -1182,10 +1183,10 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
             let impl_bounds = self.tcx.predicates_of(impl_def_id);
             let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
             let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
-                traits::normalize(selcx, cause.clone(), &impl_bounds);
+                traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
 
             // Convert the bounds into obligations.
-            let obligations = traits::predicates_for_generics(cause.clone(), &impl_bounds);
+            let obligations = traits::predicates_for_generics(cause.clone(), self.param_env, &impl_bounds);
             debug!("impl_obligations={:?}", obligations);
 
             // Evaluate those obligations to see if they might possibly hold.

src/librustc_typeck/check/method/suggest.rs

@@ -57,7 +57,10 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                         let trait_ref = ty::TraitRef::new(fn_once, fn_once_substs);
                         let poly_trait_ref = trait_ref.to_poly_trait_ref();
                         let obligation =
-                            Obligation::misc(span, self.body_id, poly_trait_ref.to_predicate());
+                            Obligation::misc(span,
+                                             self.body_id,
+                                             self.param_env,
+                                             poly_trait_ref.to_predicate());
                         SelectionContext::new(self).evaluate_obligation(&obligation)
                     })
                 })

src/librustc_typeck/check/mod.rs

@@ -450,6 +450,14 @@ impl<'gcx, 'tcx> EnclosingBreakables<'gcx, 'tcx> {
 pub struct FnCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     body_id: ast::NodeId,
 
+    /// The parameter environment used for proving trait obligations
+    /// in this function. This can change when we descend into
+    /// closures (as they bring new things into scope), hence it is
+    /// not part of `Inherited` (as of the time of this writing,
+    /// closures do not yet change the environment, but they will
+    /// eventually).
+    param_env: ty::ParamEnv<'tcx>,
+
     // Number of errors that had been reported when we started
     // checking this function. On exit, if we find that *more* errors
     // have been reported, we will skip regionck and other work that
@@ -528,9 +536,8 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
     pub fn build(tcx: TyCtxt<'a, 'gcx, 'gcx>, def_id: DefId)
                  -> InheritedBuilder<'a, 'gcx, 'tcx> {
         let tables = ty::TypeckTables::empty();
-        let param_env = tcx.param_env(def_id);
         InheritedBuilder {
-            infcx: tcx.infer_ctxt((tables, param_env)),
+            infcx: tcx.infer_ctxt(tables),
             def_id,
         }
     }
@@ -590,16 +597,18 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
     fn normalize_associated_types_in<T>(&self,
                                         span: Span,
                                         body_id: ast::NodeId,
+                                        param_env: ty::ParamEnv<'tcx>,
                                         value: &T) -> T
         where T : TypeFoldable<'tcx>
     {
-        let ok = self.normalize_associated_types_in_as_infer_ok(span, body_id, value);
+        let ok = self.normalize_associated_types_in_as_infer_ok(span, body_id, param_env, value);
         self.register_infer_ok_obligations(ok)
     }
 
     fn normalize_associated_types_in_as_infer_ok<T>(&self,
                                                     span: Span,
                                                     body_id: ast::NodeId,
+                                                    param_env: ty::ParamEnv<'tcx>,
                                                     value: &T)
                                                     -> InferOk<'tcx, T>
         where T : TypeFoldable<'tcx>
@@ -608,7 +617,7 @@ impl<'a, 'gcx, 'tcx> Inherited<'a, 'gcx, 'tcx> {
         let mut selcx = traits::SelectionContext::new(self);
         let cause = ObligationCause::misc(span, body_id);
         let traits::Normalized { value, obligations } =
-            traits::normalize(&mut selcx, cause, value);
+            traits::normalize(&mut selcx, param_env, cause, value);
         debug!("normalize_associated_types_in: result={:?} predicates={:?}",
             value,
             obligations);
@@ -797,6 +806,7 @@ fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let body = tcx.hir.body(body_id);
 
     Inherited::build(tcx, def_id).enter(|inh| {
+        let param_env = tcx.param_env(def_id);
         let fcx = if let Some(decl) = fn_decl {
             let fn_sig = tcx.type_of(def_id).fn_sig();
 
@@ -806,11 +816,14 @@ fn typeck_tables_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             let fn_sig =
                 inh.liberate_late_bound_regions(def_id, &fn_sig);
             let fn_sig =
-                inh.normalize_associated_types_in(body.value.span, body_id.node_id, &fn_sig);
+                inh.normalize_associated_types_in(body.value.span,
+                                                  body_id.node_id,
+                                                  param_env,
+                                                  &fn_sig);
 
-            check_fn(&inh, fn_sig, decl, id, body)
+            check_fn(&inh, param_env, fn_sig, decl, id, body)
         } else {
-            let fcx = FnCtxt::new(&inh, body.value.id);
+            let fcx = FnCtxt::new(&inh, param_env, body.value.id);
             let expected_type = tcx.type_of(def_id);
             let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
             fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
@@ -919,6 +932,7 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for GatherLocalsVisitor<'a, 'gcx, 'tcx> {
 /// * ...
 /// * inherited: other fields inherited from the enclosing fn (if any)
 fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
+                            param_env: ty::ParamEnv<'tcx>,
                             fn_sig: ty::FnSig<'tcx>,
                             decl: &'gcx hir::FnDecl,
                             fn_id: ast::NodeId,
@@ -927,11 +941,11 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
 {
     let mut fn_sig = fn_sig.clone();
 
-    debug!("check_fn(sig={:?}, fn_id={})", fn_sig, fn_id);
+    debug!("check_fn(sig={:?}, fn_id={}, param_env={:?})", fn_sig, fn_id, param_env);
 
     // Create the function context.  This is either derived from scratch or,
     // in the case of function expressions, based on the outer context.
-    let mut fcx = FnCtxt::new(inherited, body.value.id);
+    let mut fcx = FnCtxt::new(inherited, param_env, body.value.id);
     *fcx.ps.borrow_mut() = UnsafetyState::function(fn_sig.unsafety, fn_id);
 
     let ret_ty = fn_sig.output();
@@ -1633,10 +1647,12 @@ enum TupleArgumentsFlag {
 
 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     pub fn new(inh: &'a Inherited<'a, 'gcx, 'tcx>,
+               param_env: ty::ParamEnv<'tcx>,
                body_id: ast::NodeId)
                -> FnCtxt<'a, 'gcx, 'tcx> {
         FnCtxt {
             body_id: body_id,
+            param_env,
             err_count_on_creation: inh.tcx.sess.err_count(),
             ret_coercion: None,
             ps: RefCell::new(UnsafetyState::function(hir::Unsafety::Normal,
@@ -1870,7 +1886,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                     // Require that the predicate holds for the concrete type.
                     let cause = traits::ObligationCause::new(span, self.body_id,
                                                              traits::ReturnType);
-                    self.register_predicate(traits::Obligation::new(cause, predicate));
+                    self.register_predicate(traits::Obligation::new(cause,
+                                                                    self.param_env,
+                                                                    predicate));
                 }
 
                 ty_var
@@ -1883,15 +1901,14 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     fn normalize_associated_types_in<T>(&self, span: Span, value: &T) -> T
         where T : TypeFoldable<'tcx>
     {
-        let ok = self.normalize_associated_types_in_as_infer_ok(span, value);
-        self.register_infer_ok_obligations(ok)
+        self.inh.normalize_associated_types_in(span, self.body_id, self.param_env, value)
     }
 
     fn normalize_associated_types_in_as_infer_ok<T>(&self, span: Span, value: &T)
                                                     -> InferOk<'tcx, T>
         where T : TypeFoldable<'tcx>
     {
-        self.inh.normalize_associated_types_in_as_infer_ok(span, self.body_id, value)
+        self.inh.normalize_associated_types_in_as_infer_ok(span, self.body_id, self.param_env, value)
     }
 
     pub fn write_nil(&self, node_id: ast::NodeId) {
@@ -1929,7 +1946,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                           cause: traits::ObligationCause<'tcx>)
     {
         self.fulfillment_cx.borrow_mut()
-            .register_bound(self, ty, def_id, cause);
+                           .register_bound(self, self.param_env, ty, def_id, cause);
     }
 
     pub fn to_ty(&self, ast_t: &hir::Ty) -> Ty<'tcx> {
@@ -1970,7 +1987,9 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
     {
         // WF obligations never themselves fail, so no real need to give a detailed cause:
         let cause = traits::ObligationCause::new(span, self.body_id, code);
-        self.register_predicate(traits::Obligation::new(cause, ty::Predicate::WellFormed(ty)));
+        self.register_predicate(traits::Obligation::new(cause,
+                                                        self.param_env,
+                                                        ty::Predicate::WellFormed(ty)));
     }
 
     pub fn register_old_wf_obligation(&self,
@@ -2023,7 +2042,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         debug!("add_obligations_for_parameters(predicates={:?})",
                predicates);
 
-        for obligation in traits::predicates_for_generics(cause, predicates) {
+        for obligation in traits::predicates_for_generics(cause, self.param_env, predicates) {
             self.register_predicate(obligation);
         }
     }
@@ -2704,7 +2723,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 // is polymorphic) and the expected return type.
                 // No argument expectations are produced if unification fails.
                 let origin = self.misc(call_span);
-                let ures = self.sub_types(false, &origin, formal_ret, ret_ty);
+                let ures = self.sub_types(false, &origin, self.param_env, formal_ret, ret_ty);
 
                 // FIXME(#15760) can't use try! here, FromError doesn't default
                 // to identity so the resulting type is not constrained.
@@ -4199,7 +4218,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             _ => return,
         };
         let last_expr_ty = self.expr_ty(last_expr);
-        if self.can_sub_types(last_expr_ty, expected_ty).is_err() {
+        if self.can_sub_types(self.param_env, last_expr_ty, expected_ty).is_err() {
             return;
         }
         let original_span = original_sp(last_stmt.span, blk.span);
@@ -4459,7 +4478,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
             let ty = self.tcx.type_of(impl_def_id);
 
             let impl_ty = self.instantiate_type_scheme(span, &substs, &ty);
-            match self.sub_types(false, &self.misc(span), self_ty, impl_ty) {
+            match self.sub_types(false, &self.misc(span), self.param_env, self_ty, impl_ty) {
                 Ok(ok) => self.register_infer_ok_obligations(ok),
                 Err(_) => {
                     span_bug!(span,

src/librustc_typeck/check/op.rs

@@ -238,9 +238,15 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                             lhs_ty);
 
                         if let TypeVariants::TyRef(_, ref ty_mut) = lhs_ty.sty {
-                            if !self.infcx.type_moves_by_default(ty_mut.ty, lhs_expr.span) &&
-                                self.lookup_op_method(ty_mut.ty, &[rhs_ty],
-                                                      Op::Binary(op, is_assign)).is_ok() {
+                            if {
+                                !self.infcx.type_moves_by_default(self.param_env,
+                                                                  ty_mut.ty,
+                                                                  lhs_expr.span) &&
+                                    self.lookup_op_method(ty_mut.ty,
+                                                          &[rhs_ty],
+                                                          Op::Binary(op, is_assign))
+                                        .is_ok()
+                            } {
                                 err.note(
                                     &format!(
                                         "this is a reference to a type that `{}` can be applied \

src/librustc_typeck/check/regionck.rs

@@ -386,7 +386,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
         for &ty in fn_sig_tys {
             let ty = self.resolve_type(ty);
             debug!("relate_free_regions(t={:?})", ty);
-            let implied_bounds = ty::wf::implied_bounds(self, body_id, ty, span);
+            let implied_bounds = ty::wf::implied_bounds(self, self.fcx.param_env, body_id, ty, span);
 
             // Record any relations between free regions that we observe into the free-region-map.
             self.free_region_map.relate_free_regions_from_implied_bounds(&implied_bounds);
@@ -1660,7 +1660,7 @@ impl<'a, 'gcx, 'tcx> RegionCtxt<'a, 'gcx, 'tcx> {
 
                     // check whether this predicate applies to our current projection
                     let cause = self.fcx.misc(span);
-                    match self.eq_types(false, &cause, ty, outlives.0) {
+                    match self.eq_types(false, &cause, self.fcx.param_env, ty, outlives.0) {
                         Ok(ok) => {
                             self.register_infer_ok_obligations(ok);
                             Ok(outlives.1)

src/librustc_typeck/check/upvar.rs

@@ -166,9 +166,11 @@ impl<'a, 'gcx, 'tcx> AdjustBorrowKind<'a, 'gcx, 'tcx> {
         {
             let body_owner_def_id = self.fcx.tcx.hir.body_owner_def_id(body.id());
             let region_maps = &self.fcx.tcx.region_maps(body_owner_def_id);
+            let param_env = self.fcx.param_env;
             let mut euv =
                 euv::ExprUseVisitor::with_options(self,
                                                   self.fcx,
+                                                  param_env,
                                                   region_maps,
                                                   mc::MemCategorizationOptions {
                                                       during_closure_kind_inference: true

src/librustc_typeck/check/wfcheck.rs

@@ -37,7 +37,8 @@ struct CheckWfFcxBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     inherited: super::InheritedBuilder<'a, 'gcx, 'tcx>,
     code: ObligationCauseCode<'gcx>,
     id: ast::NodeId,
-    span: Span
+    span: Span,
+    param_env: ty::ParamEnv<'tcx>,
 }
 
 impl<'a, 'gcx, 'tcx> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
@@ -48,8 +49,9 @@ impl<'a, 'gcx, 'tcx> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
         let code = self.code.clone();
         let id = self.id;
         let span = self.span;
+        let param_env = self.param_env;
         self.inherited.enter(|inh| {
-            let fcx = FnCtxt::new(&inh, id);
+            let fcx = FnCtxt::new(&inh, param_env, id);
             let wf_tys = f(&fcx, &mut CheckTypeWellFormedVisitor {
                 tcx: fcx.tcx.global_tcx(),
                 code: code
@@ -206,11 +208,13 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
 
     fn for_id<'tcx>(&self, id: ast::NodeId, span: Span)
                     -> CheckWfFcxBuilder<'a, 'gcx, 'tcx> {
+        let def_id = self.tcx.hir.local_def_id(id);
         CheckWfFcxBuilder {
-            inherited: Inherited::build(self.tcx, self.tcx.hir.local_def_id(id)),
+            inherited: Inherited::build(self.tcx, def_id),
             code: self.code.clone(),
             id: id,
-            span: span
+            span: span,
+            param_env: self.tcx.param_env(def_id),
         }
     }
 
@@ -374,6 +378,7 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
                             ast_trait_ref.path.span, &trait_ref);
                     let obligations =
                         ty::wf::trait_obligations(fcx,
+                                                  fcx.param_env,
                                                   fcx.body_id,
                                                   &trait_ref,
                                                   ast_trait_ref.path.span);
@@ -405,6 +410,7 @@ impl<'a, 'gcx> CheckTypeWellFormedVisitor<'a, 'gcx> {
             predicates.predicates
                       .iter()
                       .flat_map(|p| ty::wf::predicate_obligations(fcx,
+                                                                  fcx.param_env,
                                                                   fcx.body_id,
                                                                   p,
                                                                   span));

src/librustc_typeck/coherence/builtin.rs

@@ -208,7 +208,7 @@ pub fn coerce_unsized_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
            source,
            target);
 
-    tcx.infer_ctxt(param_env).enter(|infcx| {
+    tcx.infer_ctxt(()).enter(|infcx| {
         let cause = ObligationCause::misc(span, impl_node_id);
         let check_mutbl = |mt_a: ty::TypeAndMut<'tcx>,
                            mt_b: ty::TypeAndMut<'tcx>,
@@ -308,7 +308,7 @@ pub fn coerce_unsized_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                         // we may have to evaluate constraint
                         // expressions in the course of execution.)
                         // See e.g. #41936.
-                        if let Ok(ok) = infcx.eq_types(false, &cause, b, a) {
+                        if let Ok(ok) = infcx.eq_types(false, &cause, param_env, b, a) {
                             if ok.obligations.is_empty() {
                                 return None;
                             }
@@ -376,7 +376,12 @@ pub fn coerce_unsized_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         // Register an obligation for `A: Trait<B>`.
         let cause = traits::ObligationCause::misc(span, impl_node_id);
-        let predicate = tcx.predicate_for_trait_def(cause, trait_def_id, 0, source, &[target]);
+        let predicate = tcx.predicate_for_trait_def(param_env,
+                                                    cause,
+                                                    trait_def_id,
+                                                    0,
+                                                    source,
+                                                    &[target]);
         fulfill_cx.register_predicate_obligation(&infcx, predicate);
 
         // Check that all transitive obligations are satisfied.
@@ -387,8 +392,7 @@ pub fn coerce_unsized_info<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // Finally, resolve all regions.
         let region_maps = RegionMaps::new();
         let mut free_regions = FreeRegionMap::new();
-        free_regions.relate_free_regions_from_predicates(&infcx.param_env
-            .caller_bounds);
+        free_regions.relate_free_regions_from_predicates(&param_env.caller_bounds);
         infcx.resolve_regions_and_report_errors(impl_did, &region_maps, &free_regions);
 
         CoerceUnsizedInfo {

src/librustc_typeck/coherence/inherent_impls_overlap.rs

@@ -11,7 +11,7 @@
 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use rustc::hir;
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
-use rustc::traits::{self, Reveal};
+use rustc::traits;
 use rustc::ty::{self, TyCtxt};
 
 pub fn crate_inherent_impls_overlap_check<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
@@ -70,7 +70,7 @@ impl<'a, 'tcx> InherentOverlapChecker<'a, 'tcx> {
 
         for (i, &impl1_def_id) in impls.iter().enumerate() {
             for &impl2_def_id in &impls[(i + 1)..] {
-                self.tcx.infer_ctxt(Reveal::UserFacing).enter(|infcx| {
+                self.tcx.infer_ctxt(()).enter(|infcx| {
                     if traits::overlapping_impls(&infcx, impl1_def_id, impl2_def_id).is_some() {
                         self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id)
                     }

src/librustc_typeck/lib.rs

@@ -155,9 +155,10 @@ fn require_same_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                 expected: Ty<'tcx>,
                                 actual: Ty<'tcx>)
                                 -> bool {
-    tcx.infer_ctxt(Reveal::UserFacing).enter(|ref infcx| {
+    tcx.infer_ctxt(()).enter(|ref infcx| {
+        let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
         let mut fulfill_cx = FulfillmentContext::new();
-        match infcx.eq_types(false, &cause, expected, actual) {
+        match infcx.eq_types(false, &cause, param_env, expected, actual) {
             Ok(InferOk { obligations, .. }) => {
                 fulfill_cx.register_predicate_obligations(infcx, obligations);
             }