Revert "introduce `UniverseIndex` into `ParamEnv`"

This reverts commit d4df52cacbee5d95e912a43188192a5054d36b4f.

5 files changed, 9 insertions, 62 deletions

diff --git a/src/librustc/ich/impls_ty.rs b/src/librustc/ich/impls_ty.rs
index 9a442e05299..594adfca6b3 100644
--- a/src/librustc/ich/impls_ty.rs
+++ b/src/librustc/ich/impls_ty.rs
@@ -1111,7 +1111,6 @@ for ty::steal::Steal<T>
 
 impl_stable_hash_for!(struct ty::ParamEnv<'tcx> {
     caller_bounds,
-    universe,
     reveal
 });
 
@@ -1282,15 +1281,6 @@ for traits::VtableGeneratorData<'gcx, N> where N: HashStable<StableHashingContex
     }
 }
 
-impl<'a> HashStable<StableHashingContext<'a>>
-for ty::UniverseIndex {
-    fn hash_stable<W: StableHasherResult>(&self,
-                                          hcx: &mut StableHashingContext<'a>,
-                                          hasher: &mut StableHasher<W>) {
-        self.depth().hash_stable(hcx, hasher);
-    }
-}
-
 impl_stable_hash_for!(
     impl<'tcx, V> for struct infer::canonical::Canonical<'tcx, V> {
         variables, value
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index a0ba88f7d55..6716d27aa1c 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -610,8 +610,7 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
            predicates);
 
     let elaborated_env = ty::ParamEnv::new(tcx.intern_predicates(&predicates),
-                                           unnormalized_env.reveal,
-                                           unnormalized_env.universe);
+                                           unnormalized_env.reveal);
 
     tcx.infer_ctxt().enter(|infcx| {
         // FIXME. We should really... do something with these region
@@ -685,9 +684,7 @@ pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         debug!("normalize_param_env_or_error: resolved predicates={:?}",
                predicates);
 
-        ty::ParamEnv::new(tcx.intern_predicates(&predicates),
-                          unnormalized_env.reveal,
-                          unnormalized_env.universe)
+        ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal)
     })
 }
 
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 6f113250003..0942fa2567b 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -1338,7 +1338,9 @@ pub struct UniverseIndex(u32);
 impl UniverseIndex {
     /// The root universe, where things that the user defined are
     /// visible.
-    pub const ROOT: UniverseIndex = UniverseIndex(0);
+    pub fn root() -> UniverseIndex {
+        UniverseIndex(0)
+    }
 
     /// A "subuniverse" corresponds to being inside a `forall` quantifier.
     /// So, for example, suppose we have this type in universe `U`:
@@ -1354,13 +1356,6 @@ impl UniverseIndex {
     pub fn subuniverse(self) -> UniverseIndex {
         UniverseIndex(self.0 + 1)
     }
-
-    /// Gets the "depth" of this universe in the universe tree. This
-    /// is not really useful except for e.g. the `HashStable`
-    /// implementation
-    pub fn depth(&self) -> u32 {
-        self.0
-    }
 }
 
 /// When type checking, we use the `ParamEnv` to track
@@ -1377,17 +1372,6 @@ pub struct ParamEnv<'tcx> {
     /// want `Reveal::All` -- note that this is always paired with an
     /// empty environment. To get that, use `ParamEnv::reveal()`.
     pub reveal: traits::Reveal,
-
-    /// What is the innermost universe we have created? Starts out as
-    /// `UniverseIndex::root()` but grows from there as we enter
-    /// universal quantifiers.
-    ///
-    /// NB: At present, we exclude the universal quantifiers on the
-    /// item we are type-checking, and just consider those names as
-    /// part of the root universe. So this would only get incremented
-    /// when we enter into a higher-ranked (`for<..>`) type or trait
-    /// bound.
-    pub universe: UniverseIndex,
 }
 
 impl<'tcx> ParamEnv<'tcx> {
@@ -2707,8 +2691,7 @@ fn param_env<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     // sure that this will succeed without errors anyway.
 
     let unnormalized_env = ty::ParamEnv::new(tcx.intern_predicates(&predicates),
-                                             traits::Reveal::UserFacing,
-                                             ty::UniverseIndex::ROOT);
+                                             traits::Reveal::UserFacing);
 
     let body_id = tcx.hir.as_local_node_id(def_id).map_or(DUMMY_NODE_ID, |id| {
         tcx.hir.maybe_body_owned_by(id).map_or(id, |body| body.node_id)
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index c9a69d5405c..05818b578ec 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -279,7 +279,6 @@ impl<'a, 'tcx> Lift<'tcx> for ty::ParamEnv<'a> {
         tcx.lift(&self.caller_bounds).map(|caller_bounds| {
             ty::ParamEnv {
                 reveal: self.reveal,
-                universe: self.universe,
                 caller_bounds,
             }
         })
@@ -737,29 +736,8 @@ 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),
-            universe: self.universe.fold_with(folder),
-        }
-    }
-
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
-        let &ty::ParamEnv { reveal: _, ref universe, ref caller_bounds } = self;
-        universe.super_visit_with(visitor) || caller_bounds.super_visit_with(visitor)
-    }
-}
-
-impl<'tcx> TypeFoldable<'tcx> for ty::UniverseIndex {
-    fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, _folder: &mut F) -> Self {
-        *self
-    }
-
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool {
-        false
-    }
+BraceStructTypeFoldableImpl! {
+    impl<'tcx> TypeFoldable<'tcx> for ty::ParamEnv<'tcx> { reveal, caller_bounds }
 }
 
 impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Slice<ty::ExistentialPredicate<'tcx>> {
diff --git a/src/librustc_typeck/check/compare_method.rs b/src/librustc_typeck/check/compare_method.rs
index 60ac31ac8eb..e1e3dea9a2a 100644
--- a/src/librustc_typeck/check/compare_method.rs
+++ b/src/librustc_typeck/check/compare_method.rs
@@ -218,8 +218,7 @@ fn compare_predicate_entailment<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     // the new hybrid bounds we computed.
     let normalize_cause = traits::ObligationCause::misc(impl_m_span, impl_m_node_id);
     let param_env = ty::ParamEnv::new(tcx.intern_predicates(&hybrid_preds.predicates),
-                                      Reveal::UserFacing,
-                                      ty::UniverseIndex::ROOT);
+                                      Reveal::UserFacing);
     let param_env = traits::normalize_param_env_or_error(tcx,
                                                          impl_m.def_id,
                                                          param_env,