Auto merge of #66233 - cjgillot:constkind, r=oli-obk

Split ConstValue into two enums

Hello,

Issue #59210 appeared abandoned, so I gave it a go.
Some further cleanup and refactoring may be mandated.

I did not test beyond `x.py check`, since my home computer dies compiling librustc.

Fixes #59210

54 files changed, 305 insertions, 274 deletions

diff --git a/src/librustc/infer/canonical/canonicalizer.rs b/src/librustc/infer/canonical/canonicalizer.rs
index 49a2c90bdbf..e782ec59295 100644
--- a/src/librustc/infer/canonical/canonicalizer.rs
+++ b/src/librustc/infer/canonical/canonicalizer.rs
@@ -10,7 +10,6 @@ use crate::infer::canonical::{
     OriginalQueryValues,
 };
 use crate::infer::InferCtxt;
-use crate::mir::interpret::ConstValue;
 use std::sync::atomic::Ordering;
 use crate::ty::fold::{TypeFoldable, TypeFolder};
 use crate::ty::subst::GenericArg;
@@ -441,7 +440,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
         match ct.val {
-            ConstValue::Infer(InferConst::Var(vid)) => {
+            ty::ConstKind::Infer(InferConst::Var(vid)) => {
                 debug!("canonical: const var found with vid {:?}", vid);
                 match self.infcx.unwrap().probe_const_var(vid) {
                     Ok(c) => {
@@ -465,17 +464,17 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
                     }
                 }
             }
-            ConstValue::Infer(InferConst::Fresh(_)) => {
+            ty::ConstKind::Infer(InferConst::Fresh(_)) => {
                 bug!("encountered a fresh const during canonicalization")
             }
-            ConstValue::Bound(debruijn, _) => {
+            ty::ConstKind::Bound(debruijn, _) => {
                 if debruijn >= self.binder_index {
                     bug!("escaping bound type during canonicalization")
                 } else {
                     return ct;
                 }
             }
-            ConstValue::Placeholder(placeholder) => {
+            ty::ConstKind::Placeholder(placeholder) => {
                 return self.canonicalize_const_var(
                     CanonicalVarInfo {
                         kind: CanonicalVarKind::PlaceholderConst(placeholder),
@@ -700,7 +699,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             let var = self.canonical_var(info, const_var.into());
             self.tcx().mk_const(
                 ty::Const {
-                    val: ConstValue::Bound(self.binder_index, var.into()),
+                    val: ty::ConstKind::Bound(self.binder_index, var.into()),
                     ty: self.fold_ty(const_var.ty),
                 }
             )
diff --git a/src/librustc/infer/canonical/mod.rs b/src/librustc/infer/canonical/mod.rs
index d833feeeb09..4e86cbb2cf6 100644
--- a/src/librustc/infer/canonical/mod.rs
+++ b/src/librustc/infer/canonical/mod.rs
@@ -24,7 +24,6 @@
 use crate::infer::{InferCtxt, RegionVariableOrigin, TypeVariableOrigin, TypeVariableOriginKind};
 use crate::infer::{ConstVariableOrigin, ConstVariableOriginKind};
 use crate::infer::region_constraints::MemberConstraint;
-use crate::mir::interpret::ConstValue;
 use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use rustc_serialize::UseSpecializedDecodable;
@@ -447,7 +446,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
                 };
                 self.tcx.mk_const(
                     ty::Const {
-                        val: ConstValue::Placeholder(placeholder_mapped),
+                        val: ty::ConstKind::Placeholder(placeholder_mapped),
                         ty: self.tcx.types.err, // FIXME(const_generics)
                     }
                 ).into()
@@ -510,7 +509,7 @@ impl<'tcx> CanonicalVarValues<'tcx> {
                     GenericArgKind::Const(ct) => {
                         tcx.mk_const(ty::Const {
                             ty: ct.ty,
-                            val: ConstValue::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i)),
+                            val: ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_u32(i)),
                         }).into()
                     }
                 })
diff --git a/src/librustc/infer/canonical/query_response.rs b/src/librustc/infer/canonical/query_response.rs
index 7ad6006012f..825e98cedb9 100644
--- a/src/librustc/infer/canonical/query_response.rs
+++ b/src/librustc/infer/canonical/query_response.rs
@@ -16,7 +16,6 @@ use crate::infer::canonical::{
 use crate::infer::region_constraints::{Constraint, RegionConstraintData};
 use crate::infer::InferCtxtBuilder;
 use crate::infer::{InferCtxt, InferOk, InferResult};
-use crate::mir::interpret::ConstValue;
 use rustc_index::vec::Idx;
 use rustc_index::vec::IndexVec;
 use std::fmt::Debug;
@@ -493,7 +492,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
                     }
                 }
                 GenericArgKind::Const(result_value) => {
-                    if let ty::Const { val: ConstValue::Bound(debrujin, b), .. } = result_value {
+                    if let ty::Const { val: ty::ConstKind::Bound(debrujin, b), .. } = result_value {
                         // ...in which case we would set `canonical_vars[0]` to `Some(const X)`.
 
                         // We only allow a `ty::INNERMOST` index in substitutions.
diff --git a/src/librustc/infer/combine.rs b/src/librustc/infer/combine.rs
index 51ae4e49493..a2f0531f0af 100644
--- a/src/librustc/infer/combine.rs
+++ b/src/librustc/infer/combine.rs
@@ -33,7 +33,6 @@ use super::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
 use super::unify_key::replace_if_possible;
 
 use crate::hir::def_id::DefId;
-use crate::mir::interpret::ConstValue;
 use crate::ty::{IntType, UintType};
 use crate::ty::{self, Ty, TyCtxt, InferConst};
 use crate::ty::error::TypeError;
@@ -137,8 +136,8 @@ impl<'infcx, 'tcx> InferCtxt<'infcx, 'tcx> {
         let a_is_expected = relation.a_is_expected();
 
         match (a.val, b.val) {
-            (ConstValue::Infer(InferConst::Var(a_vid)),
-                ConstValue::Infer(InferConst::Var(b_vid))) => {
+            (ty::ConstKind::Infer(InferConst::Var(a_vid)),
+                ty::ConstKind::Infer(InferConst::Var(b_vid))) => {
                 self.const_unification_table
                     .borrow_mut()
                     .unify_var_var(a_vid, b_vid)
@@ -147,16 +146,16 @@ impl<'infcx, 'tcx> InferCtxt<'infcx, 'tcx> {
             }
 
             // All other cases of inference with other variables are errors.
-            (ConstValue::Infer(InferConst::Var(_)), ConstValue::Infer(_)) |
-            (ConstValue::Infer(_), ConstValue::Infer(InferConst::Var(_))) => {
-                bug!("tried to combine ConstValue::Infer/ConstValue::Infer(InferConst::Var)")
+            (ty::ConstKind::Infer(InferConst::Var(_)), ty::ConstKind::Infer(_)) |
+            (ty::ConstKind::Infer(_), ty::ConstKind::Infer(InferConst::Var(_))) => {
+                bug!("tried to combine ConstKind::Infer/ConstKind::Infer(InferConst::Var)")
             }
 
-            (ConstValue::Infer(InferConst::Var(vid)), _) => {
+            (ty::ConstKind::Infer(InferConst::Var(vid)), _) => {
                 return self.unify_const_variable(a_is_expected, vid, b);
             }
 
-            (_, ConstValue::Infer(InferConst::Var(vid))) => {
+            (_, ty::ConstKind::Infer(InferConst::Var(vid))) => {
                 return self.unify_const_variable(!a_is_expected, vid, a);
             }
 
@@ -603,7 +602,7 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
         assert_eq!(c, c2); // we are abusing TypeRelation here; both LHS and RHS ought to be ==
 
         match c.val {
-            ConstValue::Infer(InferConst::Var(vid)) => {
+            ty::ConstKind::Infer(InferConst::Var(vid)) => {
                 let mut variable_table = self.infcx.const_unification_table.borrow_mut();
                 let var_value = variable_table.probe_value(vid);
                 match var_value.val {
diff --git a/src/librustc/infer/freshen.rs b/src/librustc/infer/freshen.rs
index 1841bd9ea64..32b51da920d 100644
--- a/src/librustc/infer/freshen.rs
+++ b/src/librustc/infer/freshen.rs
@@ -31,7 +31,6 @@
 //! variable only once, and it does so as soon as it can, so it is reasonable to ask what the type
 //! inferencer knows "so far".
 
-use crate::mir::interpret::ConstValue;
 use crate::ty::{self, Ty, TyCtxt, TypeFoldable};
 use crate::ty::fold::TypeFolder;
 use crate::util::nodemap::FxHashMap;
@@ -227,7 +226,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
         match ct.val {
-            ConstValue::Infer(ty::InferConst::Var(v)) => {
+            ty::ConstKind::Infer(ty::InferConst::Var(v)) => {
                 let opt_ct = self.infcx.const_unification_table
                     .borrow_mut()
                     .probe_value(v)
@@ -240,7 +239,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
                     ct.ty,
                 );
             }
-            ConstValue::Infer(ty::InferConst::Fresh(i)) => {
+            ty::ConstKind::Infer(ty::InferConst::Fresh(i)) => {
                 if i >= self.const_freshen_count {
                     bug!(
                         "Encountered a freshend const with id {} \
@@ -252,16 +251,14 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
                 return ct;
             }
 
-            ConstValue::Bound(..) |
-            ConstValue::Placeholder(_) => {
+            ty::ConstKind::Bound(..) |
+            ty::ConstKind::Placeholder(_) => {
                 bug!("unexpected const {:?}", ct)
             }
 
-            ConstValue::Param(_) |
-            ConstValue::Scalar(_) |
-            ConstValue::Slice { .. } |
-            ConstValue::ByRef { .. } |
-            ConstValue::Unevaluated(..) => {}
+            ty::ConstKind::Param(_) |
+            ty::ConstKind::Value(_) |
+            ty::ConstKind::Unevaluated(..) => {}
         }
 
         ct.super_fold_with(self)
diff --git a/src/librustc/infer/fudge.rs b/src/librustc/infer/fudge.rs
index e27766f4616..11f86a619b5 100644
--- a/src/librustc/infer/fudge.rs
+++ b/src/librustc/infer/fudge.rs
@@ -1,6 +1,5 @@
 use crate::ty::{self, Ty, TyCtxt, TyVid, IntVid, FloatVid, RegionVid, ConstVid};
 use crate::ty::fold::{TypeFoldable, TypeFolder};
-use crate::mir::interpret::ConstValue;
 
 use super::InferCtxt;
 use super::{RegionVariableOrigin, ConstVariableOrigin};
@@ -198,7 +197,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for InferenceFudger<'a, 'tcx> {
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
-        if let ty::Const { val: ConstValue::Infer(ty::InferConst::Var(vid)), ty } = ct {
+        if let ty::Const { val: ty::ConstKind::Infer(ty::InferConst::Var(vid)), ty } = ct {
             if self.const_vars.0.contains(&vid) {
                 // This variable was created during the fudging.
                 // Recreate it with a fresh variable here.
diff --git a/src/librustc/infer/higher_ranked/mod.rs b/src/librustc/infer/higher_ranked/mod.rs
index 542ac4931ec..49c095c69d6 100644
--- a/src/librustc/infer/higher_ranked/mod.rs
+++ b/src/librustc/infer/higher_ranked/mod.rs
@@ -7,7 +7,6 @@ use super::{HigherRankedType, InferCtxt, PlaceholderMap};
 use crate::infer::CombinedSnapshot;
 use crate::ty::relate::{Relate, RelateResult, TypeRelation};
 use crate::ty::{self, Binder, TypeFoldable};
-use crate::mir::interpret::ConstValue;
 
 impl<'a, 'tcx> CombineFields<'a, 'tcx> {
     pub fn higher_ranked_sub<T>(
@@ -103,7 +102,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         let fld_c = |bound_var: ty::BoundVar, ty| {
             self.tcx.mk_const(
                 ty::Const {
-                    val: ConstValue::Placeholder(ty::PlaceholderConst {
+                    val: ty::ConstKind::Placeholder(ty::PlaceholderConst {
                         universe: next_universe,
                         name: bound_var,
                     }),
diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index e385d576b8c..49fb84a8260 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -14,7 +14,6 @@ use crate::infer::unify_key::{ConstVarValue, ConstVariableValue};
 use crate::middle::free_region::RegionRelations;
 use crate::middle::lang_items;
 use crate::middle::region;
-use crate::mir::interpret::ConstValue;
 use crate::session::config::BorrowckMode;
 use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
 use crate::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
@@ -1662,7 +1661,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
-        if let ty::Const { val: ConstValue::Infer(InferConst::Var(vid)), .. } = ct {
+        if let ty::Const { val: ty::ConstKind::Infer(InferConst::Var(vid)), .. } = ct {
                 self.infcx.const_unification_table
                     .borrow_mut()
                     .probe_value(*vid)
diff --git a/src/librustc/infer/nll_relate/mod.rs b/src/librustc/infer/nll_relate/mod.rs
index d6f76e9ee34..1e0feb6a7da 100644
--- a/src/librustc/infer/nll_relate/mod.rs
+++ b/src/librustc/infer/nll_relate/mod.rs
@@ -29,7 +29,6 @@ use crate::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use crate::ty::subst::GenericArg;
 use crate::ty::{self, Ty, TyCtxt, InferConst};
 use crate::infer::{ConstVariableValue, ConstVarValue};
-use crate::mir::interpret::ConstValue;
 use rustc_data_structures::fx::FxHashMap;
 use std::fmt::Debug;
 
@@ -626,7 +625,7 @@ where
         }
 
         match b.val {
-            ConstValue::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
+            ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
                 // Forbid inference variables in the RHS.
                 bug!("unexpected inference var {:?}", b)
             }
@@ -999,13 +998,13 @@ where
         _: &'tcx ty::Const<'tcx>,
     ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> {
         match a.val {
-            ConstValue::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
+            ty::ConstKind::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
                 bug!(
                     "unexpected inference variable encountered in NLL generalization: {:?}",
                     a
                 );
             }
-            ConstValue::Infer(InferConst::Var(vid)) => {
+            ty::ConstKind::Infer(InferConst::Var(vid)) => {
                 let mut variable_table = self.infcx.const_unification_table.borrow_mut();
                 let var_value = variable_table.probe_value(vid);
                 match var_value.val.known() {
diff --git a/src/librustc/infer/opaque_types/mod.rs b/src/librustc/infer/opaque_types/mod.rs
index bd19a002fe8..dc54a273ed0 100644
--- a/src/librustc/infer/opaque_types/mod.rs
+++ b/src/librustc/infer/opaque_types/mod.rs
@@ -4,7 +4,6 @@ use crate::hir::Node;
 use crate::infer::outlives::free_region_map::FreeRegionRelations;
 use crate::infer::{self, InferCtxt, InferOk, TypeVariableOrigin, TypeVariableOriginKind};
 use crate::middle::region;
-use crate::mir::interpret::ConstValue;
 use crate::traits::{self, PredicateObligation};
 use crate::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder, TypeVisitor};
 use crate::ty::subst::{InternalSubsts, GenericArg, SubstsRef, GenericArgKind};
@@ -945,7 +944,7 @@ impl TypeFolder<'tcx> for ReverseMapper<'tcx> {
         trace!("checking const {:?}", ct);
         // Find a const parameter
         match ct.val {
-            ConstValue::Param(..) => {
+            ty::ConstKind::Param(..) => {
                 // Look it up in the substitution list.
                 match self.map.get(&ct.into()).map(|k| k.unpack()) {
                     // Found it in the substitution list, replace with the parameter from the
diff --git a/src/librustc/infer/resolve.rs b/src/librustc/infer/resolve.rs
index 7c3a338366c..613f66d7ffd 100644
--- a/src/librustc/infer/resolve.rs
+++ b/src/librustc/infer/resolve.rs
@@ -1,6 +1,5 @@
 use super::{InferCtxt, FixupError, FixupResult, Span};
 use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use crate::mir::interpret::ConstValue;
 use crate::ty::{self, Ty, Const, TyCtxt, TypeFoldable, InferConst};
 use crate::ty::fold::{TypeFolder, TypeVisitor};
 
@@ -230,11 +229,11 @@ impl<'a, 'tcx> TypeFolder<'tcx> for FullTypeResolver<'a, 'tcx> {
         } else {
             let c = self.infcx.shallow_resolve(c);
             match c.val {
-                ConstValue::Infer(InferConst::Var(vid)) => {
+                ty::ConstKind::Infer(InferConst::Var(vid)) => {
                     self.err = Some(FixupError::UnresolvedConst(vid));
                     return self.tcx().consts.err;
                 }
-                ConstValue::Infer(InferConst::Fresh(_)) => {
+                ty::ConstKind::Infer(InferConst::Fresh(_)) => {
                     bug!("Unexpected const in full const resolver: {:?}", c);
                 }
                 _ => {}
diff --git a/src/librustc/infer/unify_key.rs b/src/librustc/infer/unify_key.rs
index b0b6d971c60..8ad6990a75d 100644
--- a/src/librustc/infer/unify_key.rs
+++ b/src/librustc/infer/unify_key.rs
@@ -1,5 +1,4 @@
 use crate::ty::{self, FloatVarValue, IntVarValue, Ty, TyCtxt, InferConst};
-use crate::mir::interpret::ConstValue;
 use rustc_data_structures::unify::{NoError, EqUnifyValue, UnifyKey, UnifyValue, UnificationTable};
 use rustc_data_structures::unify::InPlace;
 use syntax_pos::{Span, DUMMY_SP};
@@ -180,7 +179,7 @@ pub fn replace_if_possible(
     mut table: RefMut<'_, UnificationTable<InPlace<ty::ConstVid<'tcx>>>>,
     c: &'tcx ty::Const<'tcx>
 ) -> &'tcx ty::Const<'tcx> {
-    if let ty::Const { val: ConstValue::Infer(InferConst::Var(vid)), .. } = c {
+    if let ty::Const { val: ty::ConstKind::Infer(InferConst::Var(vid)), .. } = c {
         match table.probe_value(*vid).val.known() {
             Some(c) => c,
             None => c,
diff --git a/src/librustc/mir/interpret/value.rs b/src/librustc/mir/interpret/value.rs
index 7b29fb26e74..a0367154b75 100644
--- a/src/librustc/mir/interpret/value.rs
+++ b/src/librustc/mir/interpret/value.rs
@@ -2,10 +2,7 @@ use std::fmt;
 use rustc_macros::HashStable;
 use rustc_apfloat::{Float, ieee::{Double, Single}};
 
-use crate::ty::{Ty, InferConst, ParamConst, layout::{HasDataLayout, Size}, subst::SubstsRef};
-use crate::ty::PlaceholderConst;
-use crate::hir::def_id::DefId;
-use crate::ty::{BoundVar, DebruijnIndex};
+use crate::ty::{Ty, layout::{HasDataLayout, Size}};
 
 use super::{InterpResult, Pointer, PointerArithmetic, Allocation, AllocId, sign_extend, truncate};
 
@@ -23,18 +20,6 @@ pub struct RawConst<'tcx> {
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord,
          RustcEncodable, RustcDecodable, Hash, HashStable)]
 pub enum ConstValue<'tcx> {
-    /// A const generic parameter.
-    Param(ParamConst),
-
-    /// Infer the value of the const.
-    Infer(InferConst<'tcx>),
-
-    /// Bound const variable, used only when preparing a trait query.
-    Bound(DebruijnIndex, BoundVar),
-
-    /// A placeholder const - universally quantified higher-ranked const.
-    Placeholder(PlaceholderConst),
-
     /// Used only for types with `layout::abi::Scalar` ABI and ZSTs.
     ///
     /// Not using the enum `Value` to encode that this must not be `Undef`.
@@ -55,10 +40,6 @@ pub enum ConstValue<'tcx> {
         /// Offset into `alloc`
         offset: Size,
     },
-
-    /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
-    /// variants when the code is monomorphic enough for that.
-    Unevaluated(DefId, SubstsRef<'tcx>),
 }
 
 #[cfg(target_arch = "x86_64")]
@@ -68,26 +49,11 @@ impl<'tcx> ConstValue<'tcx> {
     #[inline]
     pub fn try_to_scalar(&self) -> Option<Scalar> {
         match *self {
-            ConstValue::Param(_) |
-            ConstValue::Infer(_) |
-            ConstValue::Bound(..) |
-            ConstValue::Placeholder(_) |
             ConstValue::ByRef { .. } |
-            ConstValue::Unevaluated(..) |
             ConstValue::Slice { .. } => None,
             ConstValue::Scalar(val) => Some(val),
         }
     }
-
-    #[inline]
-    pub fn try_to_bits(&self, size: Size) -> Option<u128> {
-        self.try_to_scalar()?.to_bits(size).ok()
-    }
-
-    #[inline]
-    pub fn try_to_ptr(&self) -> Option<Pointer> {
-        self.try_to_scalar()?.to_ptr().ok()
-    }
 }
 
 /// A `Scalar` represents an immediate, primitive value existing outside of a
diff --git a/src/librustc/mir/mod.rs b/src/librustc/mir/mod.rs
index fd2063e2da9..39940dca99d 100644
--- a/src/librustc/mir/mod.rs
+++ b/src/librustc/mir/mod.rs
@@ -7,7 +7,7 @@
 use crate::hir::def::{CtorKind, Namespace};
 use crate::hir::def_id::DefId;
 use crate::hir::{self, InlineAsm as HirInlineAsm};
-use crate::mir::interpret::{ConstValue, PanicInfo, Scalar};
+use crate::mir::interpret::{PanicInfo, Scalar};
 use crate::mir::visit::MirVisitable;
 use crate::ty::adjustment::PointerCast;
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
@@ -1506,10 +1506,11 @@ impl<'tcx> TerminatorKind<'tcx> {
                 values
                     .iter()
                     .map(|&u| {
-                        tcx.mk_const(ty::Const {
-                            val: ConstValue::Scalar(Scalar::from_uint(u, size).into()),
-                            ty: switch_ty,
-                        })
+                        ty::Const::from_scalar(
+                            tcx,
+                            Scalar::from_uint(u, size).into(),
+                            switch_ty,
+                        )
                         .to_string()
                         .into()
                     })
diff --git a/src/librustc/ty/_match.rs b/src/librustc/ty/_match.rs
index a0d22789dae..ea8a6ff2b2e 100644
--- a/src/librustc/ty/_match.rs
+++ b/src/librustc/ty/_match.rs
@@ -1,7 +1,6 @@
 use crate::ty::{self, Ty, TyCtxt, InferConst};
 use crate::ty::error::TypeError;
 use crate::ty::relate::{self, Relate, TypeRelation, RelateResult};
-use crate::mir::interpret::ConstValue;
 
 /// A type "A" *matches* "B" if the fresh types in B could be
 /// substituted with values so as to make it equal to A. Matching is
@@ -92,11 +91,11 @@ impl TypeRelation<'tcx> for Match<'tcx> {
         }
 
         match (a.val, b.val) {
-            (_, ConstValue::Infer(InferConst::Fresh(_))) => {
+            (_, ty::ConstKind::Infer(InferConst::Fresh(_))) => {
                 return Ok(a);
             }
 
-            (ConstValue::Infer(_), _) | (_, ConstValue::Infer(_)) => {
+            (ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => {
                 return Err(TypeError::ConstMismatch(relate::expected_found(self, &a, &b)));
             }
 
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index a15acb00c17..2b78221c888 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -886,7 +886,7 @@ impl CanonicalUserType<'tcx> {
                         },
 
                         GenericArgKind::Const(ct) => match ct.val {
-                            ConstValue::Bound(debruijn, b) => {
+                            ty::ConstKind::Bound(debruijn, b) => {
                                 // We only allow a `ty::INNERMOST` index in substitutions.
                                 assert_eq!(debruijn, ty::INNERMOST);
                                 cvar == b
@@ -987,7 +987,7 @@ impl<'tcx> CommonConsts<'tcx> {
 
         CommonConsts {
             err: mk_const(ty::Const {
-                val: ConstValue::Scalar(Scalar::zst()),
+                val: ty::ConstKind::Value(ConstValue::Scalar(Scalar::zst())),
                 ty: types.err,
             }),
         }
@@ -2543,7 +2543,7 @@ impl<'tcx> TyCtxt<'tcx> {
     #[inline]
     pub fn mk_const_var(self, v: ConstVid<'tcx>, ty: Ty<'tcx>) -> &'tcx Const<'tcx> {
         self.mk_const(ty::Const {
-            val: ConstValue::Infer(InferConst::Var(v)),
+            val: ty::ConstKind::Infer(InferConst::Var(v)),
             ty,
         })
     }
@@ -2570,7 +2570,7 @@ impl<'tcx> TyCtxt<'tcx> {
         ty: Ty<'tcx>,
     ) -> &'tcx ty::Const<'tcx> {
         self.mk_const(ty::Const {
-            val: ConstValue::Infer(ic),
+            val: ty::ConstKind::Infer(ic),
             ty,
         })
     }
@@ -2588,7 +2588,7 @@ impl<'tcx> TyCtxt<'tcx> {
         ty: Ty<'tcx>
     ) -> &'tcx Const<'tcx> {
         self.mk_const(ty::Const {
-            val: ConstValue::Param(ParamConst { index, name }),
+            val: ty::ConstKind::Param(ParamConst { index, name }),
             ty,
         })
     }
diff --git a/src/librustc/ty/flags.rs b/src/librustc/ty/flags.rs
index d4b7f37b120..aee0ec7806b 100644
--- a/src/librustc/ty/flags.rs
+++ b/src/librustc/ty/flags.rs
@@ -1,6 +1,5 @@
 use crate::ty::subst::{SubstsRef, GenericArgKind};
 use crate::ty::{self, Ty, TypeFlags, InferConst};
-use crate::mir::interpret::ConstValue;
 
 #[derive(Debug)]
 pub struct FlagComputation {
@@ -232,29 +231,27 @@ impl FlagComputation {
     fn add_const(&mut self, c: &ty::Const<'_>) {
         self.add_ty(c.ty);
         match c.val {
-            ConstValue::Unevaluated(_, substs) => {
+            ty::ConstKind::Unevaluated(_, substs) => {
                 self.add_substs(substs);
                 self.add_flags(TypeFlags::HAS_PROJECTION);
             },
-            ConstValue::Infer(infer) => {
+            ty::ConstKind::Infer(infer) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES | TypeFlags::HAS_CT_INFER);
                 match infer {
                     InferConst::Fresh(_) => {}
                     InferConst::Var(_) => self.add_flags(TypeFlags::KEEP_IN_LOCAL_TCX),
                 }
             }
-            ConstValue::Bound(debruijn, _) => self.add_binder(debruijn),
-            ConstValue::Param(_) => {
+            ty::ConstKind::Bound(debruijn, _) => self.add_binder(debruijn),
+            ty::ConstKind::Param(_) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
                 self.add_flags(TypeFlags::HAS_PARAMS);
             }
-            ConstValue::Placeholder(_) => {
+            ty::ConstKind::Placeholder(_) => {
                 self.add_flags(TypeFlags::HAS_FREE_LOCAL_NAMES);
                 self.add_flags(TypeFlags::HAS_CT_PLACEHOLDER);
             }
-            ConstValue::Scalar(_) => {}
-            ConstValue::Slice { .. } => {}
-            ConstValue::ByRef { .. } => {}
+            ty::ConstKind::Value(_) => {}
         }
     }
 
diff --git a/src/librustc/ty/fold.rs b/src/librustc/ty/fold.rs
index bacf3d42f04..f3480ce5739 100644
--- a/src/librustc/ty/fold.rs
+++ b/src/librustc/ty/fold.rs
@@ -32,7 +32,6 @@
 //! looking for, and does not need to visit anything else.
 
 use crate::hir::def_id::DefId;
-use crate::mir::interpret::ConstValue;
 use crate::ty::{self, Binder, Ty, TyCtxt, TypeFlags, flags::FlagComputation};
 
 use std::collections::BTreeMap;
@@ -521,7 +520,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for BoundVarReplacer<'a, 'tcx> {
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
-        if let ty::Const { val: ConstValue::Bound(debruijn, bound_const), ty } = *ct {
+        if let ty::Const { val: ty::ConstKind::Bound(debruijn, bound_const), ty } = *ct {
             if debruijn == self.current_index {
                 let fld_c = &mut self.fld_c;
                 let ct = fld_c(bound_const, ty);
@@ -568,7 +567,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let fld_t = |bound_ty| self.mk_ty(ty::Bound(ty::INNERMOST, bound_ty));
         let fld_c = |bound_ct, ty| {
             self.mk_const(ty::Const {
-                val: ConstValue::Bound(ty::INNERMOST, bound_ct),
+                val: ty::ConstKind::Bound(ty::INNERMOST, bound_ct),
                 ty,
             })
         };
@@ -801,7 +800,7 @@ impl TypeFolder<'tcx> for Shifter<'tcx> {
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
-        if let ty::Const { val: ConstValue::Bound(debruijn, bound_ct), ty } = *ct {
+        if let ty::Const { val: ty::ConstKind::Bound(debruijn, bound_ct), ty } = *ct {
             if self.amount == 0 || debruijn < self.current_index {
                 ct
             } else {
@@ -813,7 +812,7 @@ impl TypeFolder<'tcx> for Shifter<'tcx> {
                     }
                 };
                 self.tcx.mk_const(ty::Const {
-                    val: ConstValue::Bound(debruijn, bound_ct),
+                    val: ty::ConstKind::Bound(debruijn, bound_ct),
                     ty,
                 })
             }
@@ -919,7 +918,7 @@ impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor {
         // const, as it has types/regions embedded in a lot of other
         // places.
         match ct.val {
-            ConstValue::Bound(debruijn, _) if debruijn >= self.outer_index => true,
+            ty::ConstKind::Bound(debruijn, _) if debruijn >= self.outer_index => true,
             _ => ct.super_visit_with(self),
         }
     }
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index e4ed1cd198e..8aa212ce310 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -63,7 +63,7 @@ pub use self::sty::{InferTy, ParamTy, ParamConst, InferConst, ProjectionTy, Exis
 pub use self::sty::{ClosureSubsts, GeneratorSubsts, UpvarSubsts, TypeAndMut};
 pub use self::sty::{TraitRef, TyKind, PolyTraitRef};
 pub use self::sty::{ExistentialTraitRef, PolyExistentialTraitRef};
-pub use self::sty::{ExistentialProjection, PolyExistentialProjection, Const};
+pub use self::sty::{ExistentialProjection, PolyExistentialProjection, Const, ConstKind};
 pub use self::sty::{BoundRegion, EarlyBoundRegion, FreeRegion, Region};
 pub use self::sty::RegionKind;
 pub use self::sty::{TyVid, IntVid, FloatVid, ConstVid, RegionVid};
diff --git a/src/librustc/ty/print/obsolete.rs b/src/librustc/ty/print/obsolete.rs
index 0389218b61d..7eb774849b1 100644
--- a/src/librustc/ty/print/obsolete.rs
+++ b/src/librustc/ty/print/obsolete.rs
@@ -6,7 +6,6 @@
 //! FIXME(eddyb) implement a custom `PrettyPrinter` for this.
 
 use rustc::hir::def_id::DefId;
-use rustc::mir::interpret::ConstValue;
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::{self, Const, Instance, Ty, TyCtxt};
 use rustc::{bug, hir};
@@ -170,21 +169,16 @@ impl DefPathBasedNames<'tcx> {
     // If `debug` is true, usually-unprintable consts (such as `Infer`) will be printed,
     // as well as the unprintable types of constants (see `push_type_name` for more details).
     pub fn push_const_name(&self, c: &Const<'tcx>, output: &mut String, debug: bool) {
-        match c.val {
-            ConstValue::Scalar(..) | ConstValue::Slice { .. } | ConstValue::ByRef { .. } => {
-                // FIXME(const_generics): we could probably do a better job here.
-                write!(output, "{:?}", c).unwrap()
-            }
-            _ => {
-                if debug {
-                    write!(output, "{:?}", c).unwrap()
-                } else {
-                    bug!(
-                        "DefPathBasedNames: trying to create const name for unexpected const: {:?}",
-                        c,
-                    );
-                }
-            }
+        if let ty::ConstKind::Value(_) = c.val {
+            // FIXME(const_generics): we could probably do a better job here.
+            write!(output, "{:?}", c).unwrap()
+        } else if debug {
+            write!(output, "{:?}", c).unwrap()
+        } else {
+            bug!(
+                "DefPathBasedNames: trying to create const name for unexpected const: {:?}",
+                c,
+            );
         }
         output.push_str(": ");
         self.push_type_name(c.ty, output, debug);
diff --git a/src/librustc/ty/print/pretty.rs b/src/librustc/ty/print/pretty.rs
index fdd3a1faaa9..594550dd967 100644
--- a/src/librustc/ty/print/pretty.rs
+++ b/src/librustc/ty/print/pretty.rs
@@ -699,7 +699,7 @@ pub trait PrettyPrinter<'tcx>:
                 p!(write("["), print(ty), write("; "));
                 if self.tcx().sess.verbose() {
                     p!(write("{:?}", sz));
-                } else if let ConstValue::Unevaluated(..) = sz.val {
+                } else if let ty::ConstKind::Unevaluated(..) = sz.val {
                     // do not try to evalute unevaluated constants. If we are const evaluating an
                     // array length anon const, rustc will (with debug assertions) print the
                     // constant's path. Which will end up here again.
@@ -861,11 +861,9 @@ pub trait PrettyPrinter<'tcx>:
             return Ok(self);
         }
 
-        let u8 = self.tcx().types.u8;
-
         match (ct.val, &ct.ty.kind) {
             (_,  ty::FnDef(did, substs)) => p!(print_value_path(*did, substs)),
-            (ConstValue::Unevaluated(did, substs), _) => {
+            (ty::ConstKind::Unevaluated(did, substs), _) => {
                 match self.tcx().def_kind(did) {
                     | Some(DefKind::Static)
                     | Some(DefKind::Const)
@@ -882,8 +880,33 @@ pub trait PrettyPrinter<'tcx>:
                     },
                 }
             },
-            (ConstValue::Infer(..), _) =>  p!(write("_: "), print(ct.ty)),
-            (ConstValue::Param(ParamConst { name, .. }), _) => p!(write("{}", name)),
+            (ty::ConstKind::Infer(..), _) =>  p!(write("_: "), print(ct.ty)),
+            (ty::ConstKind::Param(ParamConst { name, .. }), _) => p!(write("{}", name)),
+            (ty::ConstKind::Value(value), _) => return self.pretty_print_const_value(value, ct.ty),
+
+            _ => {
+                // fallback
+                p!(write("{:?} : ", ct.val), print(ct.ty))
+            }
+        };
+        Ok(self)
+    }
+
+    fn pretty_print_const_value(
+        mut self,
+        ct: ConstValue<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> Result<Self::Const, Self::Error> {
+        define_scoped_cx!(self);
+
+        if self.tcx().sess.verbose() {
+            p!(write("ConstValue({:?}: {:?})", ct, ty));
+            return Ok(self);
+        }
+
+        let u8 = self.tcx().types.u8;
+
+        match (ct, &ty.kind) {
             (ConstValue::Scalar(Scalar::Raw { data, .. }), ty::Bool) =>
                 p!(write("{}", if data == 0 { "false" } else { "true" })),
             (ConstValue::Scalar(Scalar::Raw { data, .. }), ty::Float(ast::FloatTy::F32)) =>
@@ -907,7 +930,7 @@ pub trait PrettyPrinter<'tcx>:
                 let min = 1u128 << (bit_size - 1);
                 let max = min - 1;
 
-                let ty = self.tcx().lift(&ct.ty).unwrap();
+                let ty = self.tcx().lift(&ty).unwrap();
                 let size = self.tcx().layout_of(ty::ParamEnv::empty().and(ty))
                     .unwrap()
                     .size;
@@ -929,8 +952,8 @@ pub trait PrettyPrinter<'tcx>:
                 p!(print_value_path(instance.def_id(), instance.substs));
             },
             _ => {
-                let printed = if let ty::Ref(_, ref_ty, _) = ct.ty.kind {
-                    let byte_str = match (ct.val, &ref_ty.kind) {
+                let printed = if let ty::Ref(_, ref_ty, _) = ty.kind {
+                    let byte_str = match (ct, &ref_ty.kind) {
                         (ConstValue::Scalar(Scalar::Ptr(ptr)), ty::Array(t, n)) if *t == u8 => {
                             let n = n.eval_usize(self.tcx(), ty::ParamEnv::empty());
                             Some(self.tcx()
@@ -957,7 +980,7 @@ pub trait PrettyPrinter<'tcx>:
                         p!(write("\""));
                         true
                     } else if let (ConstValue::Slice { data, start, end }, ty::Str) =
-                        (ct.val, &ref_ty.kind)
+                        (ct, &ref_ty.kind)
                     {
                         // The `inspect` here is okay since we checked the bounds, and there are no
                         // relocations (we have an active `str` reference here). We don't use this
@@ -975,7 +998,7 @@ pub trait PrettyPrinter<'tcx>:
                 };
                 if !printed {
                     // fallback
-                    p!(write("{:?} : ", ct.val), print(ct.ty))
+                    p!(write("{:?} : ", ct), print(ty))
                 }
             }
         };
diff --git a/src/librustc/ty/relate.rs b/src/librustc/ty/relate.rs
index 9b5cdc489a8..28bd43b3ee5 100644
--- a/src/librustc/ty/relate.rs
+++ b/src/librustc/ty/relate.rs
@@ -561,51 +561,59 @@ pub fn super_relate_consts<R: TypeRelation<'tcx>>(
     // and those that derive both `PartialEq` and `Eq`, corresponding
     // to `structural_match` types.
     let new_const_val = match (eagerly_eval(a), eagerly_eval(b)) {
-        (ConstValue::Infer(_), _) | (_, ConstValue::Infer(_)) => {
+        (ty::ConstKind::Infer(_), _) | (_, ty::ConstKind::Infer(_)) => {
             // The caller should handle these cases!
             bug!("var types encountered in super_relate_consts: {:?} {:?}", a, b)
         }
-        (ConstValue::Param(a_p), ConstValue::Param(b_p)) if a_p.index == b_p.index => {
+        (ty::ConstKind::Param(a_p), ty::ConstKind::Param(b_p)) if a_p.index == b_p.index => {
             return Ok(a);
         }
-        (ConstValue::Placeholder(p1), ConstValue::Placeholder(p2)) if p1 == p2 => {
+        (ty::ConstKind::Placeholder(p1), ty::ConstKind::Placeholder(p2)) if p1 == p2 => {
             return Ok(a);
         }
-        (ConstValue::Scalar(a_val), ConstValue::Scalar(b_val)) if a.ty == b.ty => {
-            if a_val == b_val {
-                Ok(ConstValue::Scalar(a_val))
-            } else if let ty::FnPtr(_) = a.ty.kind {
-                let alloc_map = tcx.alloc_map.lock();
-                let a_instance = alloc_map.unwrap_fn(a_val.to_ptr().unwrap().alloc_id);
-                let b_instance = alloc_map.unwrap_fn(b_val.to_ptr().unwrap().alloc_id);
-                if a_instance == b_instance {
-                    Ok(ConstValue::Scalar(a_val))
-                } else {
-                    Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
+        (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => {
+            let new_val = match (a_val, b_val) {
+                (ConstValue::Scalar(a_val), ConstValue::Scalar(b_val)) if a.ty == b.ty => {
+                    if a_val == b_val {
+                        Ok(ConstValue::Scalar(a_val))
+                    } else if let ty::FnPtr(_) = a.ty.kind {
+                        let alloc_map = tcx.alloc_map.lock();
+                        let a_instance = alloc_map.unwrap_fn(a_val.to_ptr().unwrap().alloc_id);
+                        let b_instance = alloc_map.unwrap_fn(b_val.to_ptr().unwrap().alloc_id);
+                        if a_instance == b_instance {
+                            Ok(ConstValue::Scalar(a_val))
+                        } else {
+                            Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
+                        }
+                    } else {
+                        Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
+                    }
                 }
-            } else {
-                Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
-            }
-        }
 
-        (a_val @ ConstValue::Slice { .. }, b_val @ ConstValue::Slice { .. }) => {
-            let a_bytes = get_slice_bytes(&tcx, a_val);
-            let b_bytes = get_slice_bytes(&tcx, b_val);
-            if a_bytes == b_bytes {
-                Ok(a_val)
-            } else {
-                Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
-            }
-        }
+                (a_val @ ConstValue::Slice { .. }, b_val @ ConstValue::Slice { .. }) => {
+                    let a_bytes = get_slice_bytes(&tcx, a_val);
+                    let b_bytes = get_slice_bytes(&tcx, b_val);
+                    if a_bytes == b_bytes {
+                        Ok(a_val)
+                    } else {
+                        Err(TypeError::ConstMismatch(expected_found(relation, &a, &b)))
+                    }
+                }
+
+                // FIXME(const_generics): handle `ConstValue::ByRef`.
+
+                _ =>  Err(TypeError::ConstMismatch(expected_found(relation, &a, &b))),
+            };
 
-        // FIXME(const_generics): handle `ConstValue::ByRef`.
+            new_val.map(ty::ConstKind::Value)
+        },
 
         // FIXME(const_generics): this is wrong, as it is a projection
-        (ConstValue::Unevaluated(a_def_id, a_substs),
-            ConstValue::Unevaluated(b_def_id, b_substs)) if a_def_id == b_def_id => {
+        (ty::ConstKind::Unevaluated(a_def_id, a_substs),
+            ty::ConstKind::Unevaluated(b_def_id, b_substs)) if a_def_id == b_def_id => {
             let substs =
                 relation.relate_with_variance(ty::Variance::Invariant, &a_substs, &b_substs)?;
-            Ok(ConstValue::Unevaluated(a_def_id, &substs))
+            Ok(ty::ConstKind::Unevaluated(a_def_id, &substs))
         }
         _ =>  Err(TypeError::ConstMismatch(expected_found(relation, &a, &b))),
     };
diff --git a/src/librustc/ty/structural_impls.rs b/src/librustc/ty/structural_impls.rs
index 5d78d563e9a..dd92898e434 100644
--- a/src/librustc/ty/structural_impls.rs
+++ b/src/librustc/ty/structural_impls.rs
@@ -5,7 +5,6 @@
 
 use crate::hir::def::Namespace;
 use crate::mir::ProjectionKind;
-use crate::mir::interpret::ConstValue;
 use crate::ty::{self, Lift, Ty, TyCtxt, InferConst};
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use crate::ty::print::{FmtPrinter, Printer};
@@ -1378,26 +1377,25 @@ impl<'tcx> TypeFoldable<'tcx> for &'tcx ty::Const<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<'tcx> for ConstValue<'tcx> {
+impl<'tcx> TypeFoldable<'tcx> for ty::ConstKind<'tcx> {
     fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
         match *self {
-            ConstValue::Infer(ic) => ConstValue::Infer(ic.fold_with(folder)),
-            ConstValue::Param(p) => ConstValue::Param(p.fold_with(folder)),
-            ConstValue::Unevaluated(did, substs)
-                => ConstValue::Unevaluated(did, substs.fold_with(folder)),
-            ConstValue::ByRef { .. } | ConstValue::Bound(..) | ConstValue::Placeholder(..)
-            | ConstValue::Scalar(..) | ConstValue::Slice { .. } => *self,
-
+            ty::ConstKind::Infer(ic) => ty::ConstKind::Infer(ic.fold_with(folder)),
+            ty::ConstKind::Param(p) => ty::ConstKind::Param(p.fold_with(folder)),
+            ty::ConstKind::Unevaluated(did, substs)
+                => ty::ConstKind::Unevaluated(did, substs.fold_with(folder)),
+            ty::ConstKind::Value(_) | ty::ConstKind::Bound(..)
+            | ty::ConstKind::Placeholder(..) => *self,
         }
     }
 
     fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
         match *self {
-            ConstValue::Infer(ic) => ic.visit_with(visitor),
-            ConstValue::Param(p) => p.visit_with(visitor),
-            ConstValue::Unevaluated(_, substs) => substs.visit_with(visitor),
-            ConstValue::ByRef { .. } | ConstValue::Bound(..) | ConstValue::Placeholder(_)
-            | ConstValue::Scalar(_) | ConstValue::Slice { .. } => false,
+            ty::ConstKind::Infer(ic) => ic.visit_with(visitor),
+            ty::ConstKind::Param(p) => p.visit_with(visitor),
+            ty::ConstKind::Unevaluated(_, substs) => substs.visit_with(visitor),
+            ty::ConstKind::Value(_) | ty::ConstKind::Bound(..)
+            | ty::ConstKind::Placeholder(_) => false,
         }
     }
 }
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 51cf7550c30..8f6fc02ab4b 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -2257,17 +2257,17 @@ impl<'tcx> TyS<'tcx> {
 pub struct Const<'tcx> {
     pub ty: Ty<'tcx>,
 
-    pub val: ConstValue<'tcx>,
+    pub val: ConstKind<'tcx>,
 }
 
 #[cfg(target_arch = "x86_64")]
-static_assert_size!(Const<'_>, 40);
+static_assert_size!(Const<'_>, 48);
 
 impl<'tcx> Const<'tcx> {
     #[inline]
     pub fn from_scalar(tcx: TyCtxt<'tcx>, val: Scalar, ty: Ty<'tcx>) -> &'tcx Self {
         tcx.mk_const(Self {
-            val: ConstValue::Scalar(val),
+            val: ConstKind::Value(ConstValue::Scalar(val)),
             ty,
         })
     }
@@ -2317,7 +2317,7 @@ impl<'tcx> Const<'tcx> {
         // FIXME(const_generics): this doesn't work right now,
         // because it tries to relate an `Infer` to a `Param`.
         match self.val {
-            ConstValue::Unevaluated(did, substs) => {
+            ConstKind::Unevaluated(did, substs) => {
                 // if `substs` has no unresolved components, use and empty param_env
                 let (param_env, substs) = param_env.with_reveal_all().and(substs).into_parts();
                 // try to resolve e.g. associated constants to their definition on an impl
@@ -2363,6 +2363,49 @@ impl<'tcx> Const<'tcx> {
 
 impl<'tcx> rustc_serialize::UseSpecializedDecodable for &'tcx Const<'tcx> {}
 
+/// Represents a constant in Rust.
+#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord,
+         RustcEncodable, RustcDecodable, Hash, HashStable)]
+pub enum ConstKind<'tcx> {
+    /// A const generic parameter.
+    Param(ParamConst),
+
+    /// Infer the value of the const.
+    Infer(InferConst<'tcx>),
+
+    /// Bound const variable, used only when preparing a trait query.
+    Bound(DebruijnIndex, BoundVar),
+
+    /// A placeholder const - universally quantified higher-ranked const.
+    Placeholder(ty::PlaceholderConst),
+
+    /// Used in the HIR by using `Unevaluated` everywhere and later normalizing to one of the other
+    /// variants when the code is monomorphic enough for that.
+    Unevaluated(DefId, SubstsRef<'tcx>),
+
+    /// Used to hold computed value.
+    Value(ConstValue<'tcx>),
+}
+
+#[cfg(target_arch = "x86_64")]
+static_assert_size!(ConstKind<'_>, 40);
+
+impl<'tcx> ConstKind<'tcx> {
+    #[inline]
+    pub fn try_to_scalar(&self) -> Option<Scalar> {
+        if let ConstKind::Value(val) = self {
+            val.try_to_scalar()
+        } else {
+            None
+        }
+    }
+
+    #[inline]
+    pub fn try_to_bits(&self, size: ty::layout::Size) -> Option<u128> {
+        self.try_to_scalar()?.to_bits(size).ok()
+    }
+}
+
 /// An inference variable for a const, for use in const generics.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd,
          Ord, RustcEncodable, RustcDecodable, Hash, HashStable)]
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
index 29721979099..8ba8622704a 100644
--- a/src/librustc/ty/subst.rs
+++ b/src/librustc/ty/subst.rs
@@ -4,7 +4,6 @@ use crate::hir::def_id::DefId;
 use crate::infer::canonical::Canonical;
 use crate::ty::{self, Lift, List, Ty, TyCtxt, ParamConst};
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
-use crate::mir::interpret::ConstValue;
 use crate::ty::sty::{ClosureSubsts, GeneratorSubsts};
 
 use rustc_serialize::{self, Encodable, Encoder, Decodable, Decoder};
@@ -234,7 +233,7 @@ impl<'a, 'tcx> InternalSubsts<'tcx> {
 
                 ty::GenericParamDefKind::Const => {
                     tcx.mk_const(ty::Const {
-                        val: ConstValue::Bound(ty::INNERMOST, ty::BoundVar::from(param.index)),
+                        val: ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from(param.index)),
                         ty: tcx.type_of(def_id),
                     }).into()
                 }
@@ -578,7 +577,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for SubstFolder<'a, 'tcx> {
             return c;
         }
 
-        if let ConstValue::Param(p) = c.val {
+        if let ty::ConstKind::Param(p) = c.val {
             self.const_for_param(p, c)
         } else {
             c.super_fold_with(self)
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index d46320abff2..76afba220ce 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -12,7 +12,6 @@ use crate::ty::subst::{Subst, InternalSubsts, SubstsRef, GenericArgKind};
 use crate::ty::query::TyCtxtAt;
 use crate::ty::TyKind::*;
 use crate::ty::layout::{Integer, IntegerExt};
-use crate::mir::interpret::ConstValue;
 use crate::util::common::ErrorReported;
 use crate::middle::lang_items;
 
@@ -566,7 +565,7 @@ impl<'tcx> TyCtxt<'tcx> {
                         !impl_generics.type_param(pt, self).pure_wrt_drop
                     }
                     GenericArgKind::Const(&ty::Const {
-                        val: ConstValue::Param(ref pc),
+                        val: ty::ConstKind::Param(ref pc),
                         ..
                     }) => {
                         !impl_generics.const_param(pc, self).pure_wrt_drop
diff --git a/src/librustc/ty/walk.rs b/src/librustc/ty/walk.rs
index f5b1902e3cc..8d0f9a47162 100644
--- a/src/librustc/ty/walk.rs
+++ b/src/librustc/ty/walk.rs
@@ -3,7 +3,6 @@
 
 use crate::ty::{self, Ty};
 use smallvec::{self, SmallVec};
-use crate::mir::interpret::ConstValue;
 
 // The TypeWalker's stack is hot enough that it's worth going to some effort to
 // avoid heap allocations.
@@ -75,7 +74,7 @@ fn push_subtypes<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent_ty: Ty<'tcx>) {
         ty::Placeholder(..) | ty::Bound(..) | ty::Foreign(..) => {
         }
         ty::Array(ty, len) => {
-            if let ConstValue::Unevaluated(_, substs) = len.val {
+            if let ty::ConstKind::Unevaluated(_, substs) = len.val {
                 stack.extend(substs.types().rev());
             }
             stack.push(len.ty);
diff --git a/src/librustc/ty/wf.rs b/src/librustc/ty/wf.rs
index f9e7a8030a6..aa0456b78af 100644
--- a/src/librustc/ty/wf.rs
+++ b/src/librustc/ty/wf.rs
@@ -8,7 +8,6 @@ use std::iter::once;
 use syntax::symbol::{kw, Ident};
 use syntax_pos::Span;
 use crate::middle::lang_items;
-use crate::mir::interpret::ConstValue;
 
 /// Returns the set of obligations needed to make `ty` well-formed.
 /// If `ty` contains unresolved inference variables, this may include
@@ -363,7 +362,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     /// Pushes the obligations required for an array length to be WF
     /// into `self.out`.
     fn compute_array_len(&mut self, constant: ty::Const<'tcx>) {
-        if let ConstValue::Unevaluated(def_id, substs) = constant.val {
+        if let ty::ConstKind::Unevaluated(def_id, substs) = constant.val {
             let obligations = self.nominal_obligations(def_id, substs);
             self.out.extend(obligations);
 
diff --git a/src/librustc_codegen_llvm/consts.rs b/src/librustc_codegen_llvm/consts.rs
index fd7054a5a0a..bcf0154e3f8 100644
--- a/src/librustc_codegen_llvm/consts.rs
+++ b/src/librustc_codegen_llvm/consts.rs
@@ -88,9 +88,9 @@ pub fn codegen_static_initializer(
     let static_ = cx.tcx.const_eval(param_env.and(cid))?;
 
     let alloc = match static_.val {
-        ConstValue::ByRef {
+        ty::ConstKind::Value(ConstValue::ByRef {
             alloc, offset,
-        } if offset.bytes() == 0 => {
+        }) if offset.bytes() == 0 => {
             alloc
         },
         _ => bug!("static const eval returned {:#?}", static_),
diff --git a/src/librustc_codegen_ssa/mir/constant.rs b/src/librustc_codegen_ssa/mir/constant.rs
index d06359ab0ce..181787e3985 100644
--- a/src/librustc_codegen_ssa/mir/constant.rs
+++ b/src/librustc_codegen_ssa/mir/constant.rs
@@ -14,7 +14,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         constant: &mir::Constant<'tcx>,
     ) -> Result<&'tcx ty::Const<'tcx>, ErrorHandled> {
         match constant.literal.val {
-            mir::interpret::ConstValue::Unevaluated(def_id, ref substs) => {
+            ty::ConstKind::Unevaluated(def_id, ref substs) => {
                 let substs = self.monomorphize(substs);
                 let instance = ty::Instance::resolve(
                     self.cx.tcx(), ty::ParamEnv::reveal_all(), def_id, substs,
diff --git a/src/librustc_codegen_ssa/mir/operand.rs b/src/librustc_codegen_ssa/mir/operand.rs
index ba5e47aeede..78d09f834c6 100644
--- a/src/librustc_codegen_ssa/mir/operand.rs
+++ b/src/librustc_codegen_ssa/mir/operand.rs
@@ -75,12 +75,12 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
             return OperandRef::new_zst(bx, layout);
         }
 
-        let val = match val.val {
-            ConstValue::Unevaluated(..) => bug!("unevaluated constant in `OperandRef::from_const`"),
-            ConstValue::Param(_) => bug!("encountered a ConstValue::Param in codegen"),
-            ConstValue::Infer(_) => bug!("encountered a ConstValue::Infer in codegen"),
-            ConstValue::Bound(..) => bug!("encountered a ConstValue::Bound in codegen"),
-            ConstValue::Placeholder(_) => bug!("encountered a ConstValue::Placeholder in codegen"),
+        let val_val = match val.val {
+            ty::ConstKind::Value(val_val) => val_val,
+            _ => bug!("encountered bad ConstKind in codegen"),
+        };
+
+        let val = match val_val {
             ConstValue::Scalar(x) => {
                 let scalar = match layout.abi {
                     layout::Abi::Scalar(ref x) => x,
diff --git a/src/librustc_codegen_ssa/mir/place.rs b/src/librustc_codegen_ssa/mir/place.rs
index 3e7c4ef49fb..d4e33ee8b6f 100644
--- a/src/librustc_codegen_ssa/mir/place.rs
+++ b/src/librustc_codegen_ssa/mir/place.rs
@@ -480,7 +480,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 let layout = cx.layout_of(self.monomorphize(&ty));
                 match bx.tcx().const_eval(param_env.and(cid)) {
                     Ok(val) => match val.val {
-                        mir::interpret::ConstValue::ByRef { alloc, offset } => {
+                        ty::ConstKind::Value(mir::interpret::ConstValue::ByRef {
+                            alloc, offset
+                        }) => {
                             bx.cx().from_const_alloc(layout, alloc, offset)
                         }
                         _ => bug!("promoteds should have an allocation: {:?}", val),
diff --git a/src/librustc_codegen_utils/symbol_names/legacy.rs b/src/librustc_codegen_utils/symbol_names/legacy.rs
index 66e1b6d949e..1597f98771c 100644
--- a/src/librustc_codegen_utils/symbol_names/legacy.rs
+++ b/src/librustc_codegen_utils/symbol_names/legacy.rs
@@ -253,7 +253,7 @@ impl Printer<'tcx> for SymbolPrinter<'tcx> {
         ct: &'tcx ty::Const<'tcx>,
     ) -> Result<Self::Const, Self::Error> {
         // only print integers
-        if let ConstValue::Scalar(Scalar::Raw { .. }) = ct.val {
+        if let ty::ConstKind::Value(ConstValue::Scalar(Scalar::Raw { .. })) = ct.val {
             if ct.ty.is_integral() {
                 return self.pretty_print_const(ct);
             }
diff --git a/src/librustc_mir/borrow_check/nll/type_check/mod.rs b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
index 37fc0b09e5b..cdfbca65e7e 100644
--- a/src/librustc_mir/borrow_check/nll/type_check/mod.rs
+++ b/src/librustc_mir/borrow_check/nll/type_check/mod.rs
@@ -27,7 +27,7 @@ use rustc::infer::canonical::QueryRegionConstraints;
 use rustc::infer::outlives::env::RegionBoundPairs;
 use rustc::infer::{InferCtxt, InferOk, LateBoundRegionConversionTime, NLLRegionVariableOrigin};
 use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc::mir::interpret::{ConstValue, PanicInfo};
+use rustc::mir::interpret::PanicInfo;
 use rustc::mir::tcx::PlaceTy;
 use rustc::mir::visit::{PlaceContext, Visitor, NonMutatingUseContext};
 use rustc::mir::*;
@@ -309,7 +309,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 );
             }
         } else {
-            if let ConstValue::Unevaluated(def_id, substs) = constant.literal.val {
+            if let ty::ConstKind::Unevaluated(def_id, substs) = constant.literal.val {
                 if let Err(terr) = self.cx.fully_perform_op(
                     location.to_locations(),
                     ConstraintCategory::Boring,
diff --git a/src/librustc_mir/const_eval.rs b/src/librustc_mir/const_eval.rs
index f280ea7aa46..0ff9d1b4af0 100644
--- a/src/librustc_mir/const_eval.rs
+++ b/src/librustc_mir/const_eval.rs
@@ -128,7 +128,7 @@ fn op_to_const<'tcx>(
             }
         },
     };
-    ecx.tcx.mk_const(ty::Const { val, ty: op.layout.ty })
+    ecx.tcx.mk_const(ty::Const { val: ty::ConstKind::Value(val), ty: op.layout.ty })
 }
 
 // Returns a pointer to where the result lives
@@ -516,7 +516,7 @@ pub fn const_caller_location<'tcx>(
     intern_const_alloc_recursive(&mut ecx, None, loc_place).unwrap();
     let loc_const = ty::Const {
         ty: loc_ty,
-        val: ConstValue::Scalar(loc_place.ptr.into()),
+        val: ty::ConstKind::Value(ConstValue::Scalar(loc_place.ptr.into())),
     };
 
     tcx.mk_const(loc_const)
@@ -577,10 +577,10 @@ fn validate_and_turn_into_const<'tcx>(
         if tcx.is_static(def_id) || cid.promoted.is_some() {
             let ptr = mplace.ptr.to_ptr()?;
             Ok(tcx.mk_const(ty::Const {
-                val: ConstValue::ByRef {
+                val: ty::ConstKind::Value(ConstValue::ByRef {
                     alloc: ecx.tcx.alloc_map.lock().unwrap_memory(ptr.alloc_id),
                     offset: ptr.offset,
-                },
+                }),
                 ty: mplace.layout.ty,
             }))
         } else {
diff --git a/src/librustc_mir/hair/constant.rs b/src/librustc_mir/hair/constant.rs
index b9e75a576ca..1abdcde10ab 100644
--- a/src/librustc_mir/hair/constant.rs
+++ b/src/librustc_mir/hair/constant.rs
@@ -56,7 +56,7 @@ crate fn lit_to_const<'tcx>(
         LitKind::Char(c) => ConstValue::Scalar(Scalar::from_char(c)),
         LitKind::Err(_) => unreachable!(),
     };
-    Ok(tcx.mk_const(ty::Const { val: lit, ty }))
+    Ok(tcx.mk_const(ty::Const { val: ty::ConstKind::Value(lit), ty }))
 }
 
 fn parse_float<'tcx>(
diff --git a/src/librustc_mir/hair/cx/expr.rs b/src/librustc_mir/hair/cx/expr.rs
index 2ff690b7ccc..92c9c702c7a 100644
--- a/src/librustc_mir/hair/cx/expr.rs
+++ b/src/librustc_mir/hair/cx/expr.rs
@@ -5,7 +5,7 @@ use crate::hair::cx::to_ref::ToRef;
 use crate::hair::util::UserAnnotatedTyHelpers;
 use rustc_index::vec::Idx;
 use rustc::hir::def::{CtorOf, Res, DefKind, CtorKind};
-use rustc::mir::interpret::{GlobalId, ErrorHandled, ConstValue};
+use rustc::mir::interpret::{GlobalId, ErrorHandled};
 use rustc::ty::{self, AdtKind, Ty};
 use rustc::ty::adjustment::{Adjustment, Adjust, AutoBorrow, AutoBorrowMutability, PointerCast};
 use rustc::ty::subst::{InternalSubsts, SubstsRef};
@@ -692,7 +692,7 @@ fn make_mirror_unadjusted<'a, 'tcx>(
                             // and not the beginning of discriminants (which is always `0`)
                             let substs = InternalSubsts::identity_for_item(cx.tcx(), did);
                             let lhs = mk_const(cx.tcx().mk_const(ty::Const {
-                                val: ConstValue::Unevaluated(did, substs),
+                                val: ty::ConstKind::Unevaluated(did, substs),
                                 ty: var_ty,
                             }));
                             let bin = ExprKind::Binary {
@@ -914,7 +914,7 @@ fn convert_path_expr<'a, 'tcx>(
             let local_def_id = cx.tcx.hir().local_def_id(hir_id);
             let index = generics.param_def_id_to_index[&local_def_id];
             let name = cx.tcx.hir().name(hir_id);
-            let val = ConstValue::Param(ty::ParamConst::new(index, name));
+            let val = ty::ConstKind::Param(ty::ParamConst::new(index, name));
             ExprKind::Literal {
                 literal: cx.tcx.mk_const(
                     ty::Const {
@@ -932,7 +932,7 @@ fn convert_path_expr<'a, 'tcx>(
             debug!("convert_path_expr: (const) user_ty={:?}", user_ty);
             ExprKind::Literal {
                 literal: cx.tcx.mk_const(ty::Const {
-                    val: ConstValue::Unevaluated(def_id, substs),
+                    val: ty::ConstKind::Unevaluated(def_id, substs),
                     ty: cx.tables().node_type(expr.hir_id),
                 }),
                 user_ty,
diff --git a/src/librustc_mir/hair/pattern/_match.rs b/src/librustc_mir/hair/pattern/_match.rs
index 8e574cc961b..84a3923c7b2 100644
--- a/src/librustc_mir/hair/pattern/_match.rs
+++ b/src/librustc_mir/hair/pattern/_match.rs
@@ -313,7 +313,10 @@ impl PatternFolder<'tcx> for LiteralExpander<'tcx> {
             (
                 &ty::Ref(_, rty, _),
                 &PatKind::Constant {
-                    value: Const { val, ty: ty::TyS { kind: ty::Ref(_, crty, _), .. } },
+                    value: Const {
+                        val: ty::ConstKind::Value(val),
+                        ty: ty::TyS { kind: ty::Ref(_, crty, _), .. }
+                    },
                 },
             ) => Pat {
                 ty: pat.ty,
@@ -324,13 +327,23 @@ impl PatternFolder<'tcx> for LiteralExpander<'tcx> {
                         span: pat.span,
                         kind: box PatKind::Constant {
                             value: self.tcx.mk_const(Const {
-                                val: self.fold_const_value_deref(*val, rty, crty),
+                                val: ty::ConstKind::Value(
+                                    self.fold_const_value_deref(*val, rty, crty)
+                                ),
                                 ty: rty,
                             }),
                         },
                     },
                 },
             },
+
+            (
+                &ty::Ref(_, rty, _),
+                &PatKind::Constant {
+                    value: Const { val, ty: ty::TyS { kind: ty::Ref(_, crty, _), .. } },
+                },
+            ) => bug!("cannot deref {:#?}, {} -> {}", val, crty, rty),
+
             (_, &PatKind::Binding { subpattern: Some(ref s), .. }) => s.fold_with(self),
             _ => pat.super_fold_with(self),
         }
@@ -1283,7 +1296,9 @@ impl<'tcx> IntRange<'tcx> {
     ) -> Option<IntRange<'tcx>> {
         if let Some((target_size, bias)) = Self::integral_size_and_signed_bias(tcx, value.ty) {
             let ty = value.ty;
-            let val = if let ConstValue::Scalar(Scalar::Raw { data, size }) = value.val {
+            let val = if let ty::ConstKind::Value(ConstValue::Scalar(
+                Scalar::Raw { data, size }
+            )) = value.val {
                 // For this specific pattern we can skip a lot of effort and go
                 // straight to the result, after doing a bit of checking. (We
                 // could remove this branch and just use the next branch, which
@@ -1776,7 +1791,19 @@ fn slice_pat_covered_by_const<'tcx>(
     suffix: &[Pat<'tcx>],
     param_env: ty::ParamEnv<'tcx>,
 ) -> Result<bool, ErrorReported> {
-    let data: &[u8] = match (const_val.val, &const_val.ty.kind) {
+    let const_val_val = if let ty::ConstKind::Value(val) = const_val.val {
+        val
+    } else {
+        bug!(
+            "slice_pat_covered_by_const: {:#?}, {:#?}, {:#?}, {:#?}",
+            const_val,
+            prefix,
+            slice,
+            suffix,
+        )
+    };
+
+    let data: &[u8] = match (const_val_val, &const_val.ty.kind) {
         (ConstValue::ByRef { offset, alloc, .. }, ty::Array(t, n)) => {
             assert_eq!(*t, tcx.types.u8);
             let n = n.eval_usize(tcx, param_env);
@@ -2049,7 +2076,8 @@ fn split_grouped_constructors<'p, 'tcx>(
                                     max_fixed_len =
                                         cmp::max(max_fixed_len, n.eval_usize(tcx, param_env))
                                 }
-                                (ConstValue::Slice { start, end, .. }, ty::Slice(_)) => {
+                                (ty::ConstKind::Value(ConstValue::Slice { start, end, .. }),
+                                 ty::Slice(_)) => {
                                     max_fixed_len = cmp::max(max_fixed_len, (end - start) as u64)
                                 }
                                 _ => {}
@@ -2256,17 +2284,17 @@ fn specialize_one_pattern<'p, 'a: 'p, 'q: 'p, 'tcx>(
             // is when they are subslices of nonzero slices.
             let (alloc, offset, n, ty) = match value.ty.kind {
                 ty::Array(t, n) => match value.val {
-                    ConstValue::ByRef { offset, alloc, .. } => {
+                    ty::ConstKind::Value(ConstValue::ByRef { offset, alloc, .. }) => {
                         (alloc, offset, n.eval_usize(cx.tcx, cx.param_env), t)
                     }
                     _ => span_bug!(pat.span, "array pattern is {:?}", value,),
                 },
                 ty::Slice(t) => {
                     match value.val {
-                        ConstValue::Slice { data, start, end } => {
+                        ty::ConstKind::Value(ConstValue::Slice { data, start, end }) => {
                             (data, Size::from_bytes(start as u64), (end - start) as u64, t)
                         }
-                        ConstValue::ByRef { .. } => {
+                        ty::ConstKind::Value(ConstValue::ByRef { .. }) => {
                             // FIXME(oli-obk): implement `deref` for `ConstValue`
                             return None;
                         }
diff --git a/src/librustc_mir/hair/pattern/mod.rs b/src/librustc_mir/hair/pattern/mod.rs
index f613f6f4b99..3d97ed6bf9b 100644
--- a/src/librustc_mir/hair/pattern/mod.rs
+++ b/src/librustc_mir/hair/pattern/mod.rs
@@ -1197,9 +1197,10 @@ pub fn compare_const_vals<'tcx>(
 
     if let ty::Str = ty.kind {
         match (a.val, b.val) {
-            (ConstValue::Slice { .. }, ConstValue::Slice { .. }) => {
-                let a_bytes = get_slice_bytes(&tcx, a.val);
-                let b_bytes = get_slice_bytes(&tcx, b.val);
+            (ty::ConstKind::Value(a_val @ ConstValue::Slice { .. }),
+             ty::ConstKind::Value(b_val @ ConstValue::Slice { .. })) => {
+                let a_bytes = get_slice_bytes(&tcx, a_val);
+                let b_bytes = get_slice_bytes(&tcx, b_val);
                 return from_bool(a_bytes == b_bytes);
             }
             _ => (),
diff --git a/src/librustc_mir/interpret/intrinsics.rs b/src/librustc_mir/interpret/intrinsics.rs
index 66b6d4ac12c..6117cf4038a 100644
--- a/src/librustc_mir/interpret/intrinsics.rs
+++ b/src/librustc_mir/interpret/intrinsics.rs
@@ -54,11 +54,11 @@ crate fn eval_nullary_intrinsic<'tcx>(
         "type_name" => {
             let alloc = type_name::alloc_type_name(tcx, tp_ty);
             tcx.mk_const(ty::Const {
-                val: ConstValue::Slice {
+                val: ty::ConstKind::Value(ConstValue::Slice {
                     data: alloc,
                     start: 0,
                     end: alloc.len(),
-                },
+                }),
                 ty: tcx.mk_static_str(),
             })
         },
diff --git a/src/librustc_mir/interpret/operand.rs b/src/librustc_mir/interpret/operand.rs
index 79762b87b0a..4d2ccdc20da 100644
--- a/src/librustc_mir/interpret/operand.rs
+++ b/src/librustc_mir/interpret/operand.rs
@@ -545,23 +545,27 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             Scalar::Raw { data, size } => Scalar::Raw { data, size },
         };
         // Early-return cases.
-        match val.val {
-            ConstValue::Param(_) =>
+        let val_val = match val.val {
+            ty::ConstKind::Param(_) =>
                 throw_inval!(TooGeneric),
-            ConstValue::Unevaluated(def_id, substs) => {
+            ty::ConstKind::Unevaluated(def_id, substs) => {
                 let instance = self.resolve(def_id, substs)?;
                 return Ok(OpTy::from(self.const_eval_raw(GlobalId {
                     instance,
                     promoted: None,
                 })?));
             }
-            _ => {}
-        }
+            ty::ConstKind::Infer(..) |
+            ty::ConstKind::Bound(..) |
+            ty::ConstKind::Placeholder(..) =>
+                bug!("eval_const_to_op: Unexpected ConstKind {:?}", val),
+            ty::ConstKind::Value(val_val) => val_val,
+        };
         // Other cases need layout.
         let layout = from_known_layout(layout, || {
             self.layout_of(val.ty)
         })?;
-        let op = match val.val {
+        let op = match val_val {
             ConstValue::ByRef { alloc, offset } => {
                 let id = self.tcx.alloc_map.lock().create_memory_alloc(alloc);
                 // We rely on mutability being set correctly in that allocation to prevent writes
@@ -583,12 +587,6 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     self,
                 ))
             }
-            ConstValue::Param(..) |
-            ConstValue::Infer(..) |
-            ConstValue::Bound(..) |
-            ConstValue::Placeholder(..) |
-            ConstValue::Unevaluated(..) =>
-                bug!("eval_const_to_op: Unexpected ConstValue {:?}", val),
         };
         Ok(OpTy { op, layout })
     }
diff --git a/src/librustc_mir/monomorphize/collector.rs b/src/librustc_mir/monomorphize/collector.rs
index 49cdd914234..49f27a8117e 100644
--- a/src/librustc_mir/monomorphize/collector.rs
+++ b/src/librustc_mir/monomorphize/collector.rs
@@ -1284,15 +1284,15 @@ fn collect_const<'tcx>(
     );
 
     match substituted_constant.val {
-        ConstValue::Scalar(Scalar::Ptr(ptr)) =>
+        ty::ConstKind::Value(ConstValue::Scalar(Scalar::Ptr(ptr))) =>
             collect_miri(tcx, ptr.alloc_id, output),
-        ConstValue::Slice { data: alloc, start: _, end: _ } |
-        ConstValue::ByRef { alloc, .. } => {
+        ty::ConstKind::Value(ConstValue::Slice { data: alloc, start: _, end: _ }) |
+        ty::ConstKind::Value(ConstValue::ByRef { alloc, .. }) => {
             for &((), id) in alloc.relocations().values() {
                 collect_miri(tcx, id, output);
             }
         }
-        ConstValue::Unevaluated(def_id, substs) => {
+        ty::ConstKind::Unevaluated(def_id, substs) => {
             let instance = ty::Instance::resolve(tcx,
                                                 param_env,
                                                 def_id,
diff --git a/src/librustc_mir/transform/check_consts/qualifs.rs b/src/librustc_mir/transform/check_consts/qualifs.rs
index 496a5679067..595ef2aad49 100644
--- a/src/librustc_mir/transform/check_consts/qualifs.rs
+++ b/src/librustc_mir/transform/check_consts/qualifs.rs
@@ -1,7 +1,6 @@
 //! A copy of the `Qualif` trait in `qualify_consts.rs` that is suitable for the new validator.
 
 use rustc::mir::*;
-use rustc::mir::interpret::ConstValue;
 use rustc::ty::{self, Ty};
 use syntax_pos::DUMMY_SP;
 
@@ -118,7 +117,7 @@ pub trait Qualif {
             Operand::Move(ref place) => Self::in_place(cx, per_local, place.as_ref()),
 
             Operand::Constant(ref constant) => {
-                if let ConstValue::Unevaluated(def_id, _) = constant.literal.val {
+                if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     // Don't peek inside trait associated constants.
                     if cx.tcx.trait_of_item(def_id).is_some() {
                         Self::in_any_value_of_ty(cx, constant.literal.ty)
diff --git a/src/librustc_mir/transform/promote_consts.rs b/src/librustc_mir/transform/promote_consts.rs
index 48a58f1d0ee..a7f48162f9b 100644
--- a/src/librustc_mir/transform/promote_consts.rs
+++ b/src/librustc_mir/transform/promote_consts.rs
@@ -14,7 +14,6 @@
 
 use rustc::hir::def_id::DefId;
 use rustc::mir::*;
-use rustc::mir::interpret::ConstValue;
 use rustc::mir::visit::{PlaceContext, MutatingUseContext, MutVisitor, Visitor};
 use rustc::mir::traversal::ReversePostorder;
 use rustc::ty::{self, List, TyCtxt, TypeFoldable};
@@ -584,7 +583,7 @@ impl<'tcx> Validator<'_, 'tcx> {
             Operand::Move(place) => self.validate_place(place.as_ref()),
 
             Operand::Constant(constant) => {
-                if let ConstValue::Unevaluated(def_id, _) = constant.literal.val {
+                if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     if self.tcx.trait_of_item(def_id).is_some() {
                         // Don't peek inside trait associated constants.
                         // (see below what we do for other consts, for now)
diff --git a/src/librustc_mir/transform/qualify_consts.rs b/src/librustc_mir/transform/qualify_consts.rs
index 255e71db89d..fd30be807b9 100644
--- a/src/librustc_mir/transform/qualify_consts.rs
+++ b/src/librustc_mir/transform/qualify_consts.rs
@@ -14,7 +14,6 @@ use rustc::ty::{self, TyCtxt, Ty, TypeFoldable};
 use rustc::ty::cast::CastTy;
 use rustc::ty::query::Providers;
 use rustc::mir::*;
-use rustc::mir::interpret::ConstValue;
 use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext, NonMutatingUseContext};
 use rustc::middle::lang_items;
 use rustc::session::config::nightly_options;
@@ -251,7 +250,7 @@ trait Qualif {
             Operand::Move(ref place) => Self::in_place(cx, place.as_ref()),
 
             Operand::Constant(ref constant) => {
-                if let ConstValue::Unevaluated(def_id, _) = constant.literal.val {
+                if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     // Don't peek inside trait associated constants.
                     if cx.tcx.trait_of_item(def_id).is_some() {
                         Self::in_any_value_of_ty(cx, constant.literal.ty).unwrap_or(false)
diff --git a/src/librustc_traits/chalk_context/mod.rs b/src/librustc_traits/chalk_context/mod.rs
index 8d136a1b65c..d9f0b8550bb 100644
--- a/src/librustc_traits/chalk_context/mod.rs
+++ b/src/librustc_traits/chalk_context/mod.rs
@@ -37,7 +37,6 @@ use rustc::ty::{self, TyCtxt};
 use rustc::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use rustc::ty::query::Providers;
 use rustc::ty::subst::{GenericArg, GenericArgKind};
-use rustc::mir::interpret::ConstValue;
 use syntax_pos::DUMMY_SP;
 
 use std::fmt::{self, Debug};
@@ -286,7 +285,7 @@ impl context::ContextOps<ChalkArenas<'tcx>> for ChalkContext<'tcx> {
                     _ => false,
                 },
                 GenericArgKind::Const(ct) => match ct.val {
-                    ConstValue::Bound(debruijn, bound_ct) => {
+                    ty::ConstKind::Bound(debruijn, bound_ct) => {
                         debug_assert_eq!(debruijn, ty::INNERMOST);
                         cvar == bound_ct
                     }
diff --git a/src/librustc_traits/chalk_context/resolvent_ops.rs b/src/librustc_traits/chalk_context/resolvent_ops.rs
index 49d76681196..b8893d65ced 100644
--- a/src/librustc_traits/chalk_context/resolvent_ops.rs
+++ b/src/librustc_traits/chalk_context/resolvent_ops.rs
@@ -19,7 +19,6 @@ use rustc::traits::{
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::subst::GenericArg;
 use rustc::ty::relate::{Relate, RelateResult, TypeRelation};
-use rustc::mir::interpret::ConstValue;
 use syntax_pos::DUMMY_SP;
 
 use super::{ChalkInferenceContext, ChalkArenas, ChalkExClause, ConstrainedSubst};
@@ -287,7 +286,7 @@ impl TypeRelation<'tcx> for AnswerSubstitutor<'cx, 'tcx> {
         a: &'tcx ty::Const<'tcx>,
         b: &'tcx ty::Const<'tcx>,
     ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> {
-        if let ty::Const { val: ConstValue::Bound(debruijn, bound_ct), .. } = a {
+        if let ty::Const { val: ty::ConstKind::Bound(debruijn, bound_ct), .. } = a {
             if *debruijn == self.binder_index {
                 self.unify_free_answer_var(*bound_ct, b.into())?;
                 return Ok(b);
@@ -296,8 +295,8 @@ impl TypeRelation<'tcx> for AnswerSubstitutor<'cx, 'tcx> {
 
         match (a, b) {
             (
-                ty::Const { val: ConstValue::Bound(a_debruijn, a_bound), .. },
-                ty::Const { val: ConstValue::Bound(b_debruijn, b_bound), .. },
+                ty::Const { val: ty::ConstKind::Bound(a_debruijn, a_bound), .. },
+                ty::Const { val: ty::ConstKind::Bound(b_debruijn, b_bound), .. },
             ) => {
                 assert_eq!(a_debruijn, b_debruijn);
                 assert_eq!(a_bound, b_bound);
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 5c661513382..ee3ebd691e4 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -18,7 +18,6 @@ use rustc::ty::{self, DefIdTree, Ty, TyCtxt, Const, ToPredicate, TypeFoldable};
 use rustc::ty::{GenericParamDef, GenericParamDefKind};
 use rustc::ty::subst::{self, Subst, InternalSubsts, SubstsRef};
 use rustc::ty::wf::object_region_bounds;
-use rustc::mir::interpret::ConstValue;
 use rustc_target::spec::abi;
 use crate::require_c_abi_if_c_variadic;
 use smallvec::SmallVec;
@@ -2226,7 +2225,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let def_id = tcx.hir().local_def_id(ast_const.hir_id);
 
         let mut const_ = ty::Const {
-            val: ConstValue::Unevaluated(
+            val: ty::ConstKind::Unevaluated(
                 def_id,
                 InternalSubsts::identity_for_item(tcx, def_id),
             ),
@@ -2243,7 +2242,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let generics = tcx.generics_of(item_def_id);
             let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
             let name = tcx.hir().name(hir_id);
-            const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
+            const_.val = ty::ConstKind::Param(ty::ParamConst::new(index, name));
         }
 
         tcx.mk_const(const_)
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 72b5018589c..2363dbc5303 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1688,7 +1688,7 @@ fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: DefId, span: Span)
     };
     let param_env = ty::ParamEnv::reveal_all();
     if let Ok(static_) = tcx.const_eval(param_env.and(cid)) {
-        let alloc = if let ConstValue::ByRef { alloc, .. } = static_.val {
+        let alloc = if let ty::ConstKind::Value(ConstValue::ByRef { alloc, .. }) = static_.val {
             alloc
         } else {
             bug!("Matching on non-ByRef static")
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 5b25d8f25a9..fd97493b591 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -6,7 +6,6 @@ use rustc::traits::{self, ObligationCauseCode};
 use rustc::ty::{self, Ty, TyCtxt, GenericParamDefKind, TypeFoldable, ToPredicate};
 use rustc::ty::subst::{Subst, InternalSubsts};
 use rustc::util::nodemap::{FxHashSet, FxHashMap};
-use rustc::mir::interpret::ConstValue;
 use rustc::middle::lang_items;
 use rustc::infer::opaque_types::may_define_opaque_type;
 
@@ -536,7 +535,7 @@ fn check_where_clauses<'tcx, 'fcx>(
             }
 
             fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool {
-                if let ConstValue::Param(param) = c.val {
+                if let ty::ConstKind::Param(param) = c.val {
                     self.params.insert(param.index);
                 }
                 c.super_visit_with(self)
@@ -705,7 +704,7 @@ fn check_opaque_types<'fcx, 'tcx>(
                                 }
 
                                 ty::subst::GenericArgKind::Const(ct) => match ct.val {
-                                    ConstValue::Param(_) => {}
+                                    ty::ConstKind::Param(_) => {}
                                     _ => {
                                         tcx.sess
                                             .struct_span_err(
diff --git a/src/librustc_typeck/constrained_generic_params.rs b/src/librustc_typeck/constrained_generic_params.rs
index 1fdf49fde55..0523de56512 100644
--- a/src/librustc_typeck/constrained_generic_params.rs
+++ b/src/librustc_typeck/constrained_generic_params.rs
@@ -1,7 +1,6 @@
 use rustc::ty::{self, Ty, TyCtxt};
 use rustc::ty::fold::{TypeFoldable, TypeVisitor};
 use rustc::util::nodemap::FxHashSet;
-use rustc::mir::interpret::ConstValue;
 use syntax::source_map::Span;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
@@ -77,7 +76,7 @@ impl<'tcx> TypeVisitor<'tcx> for ParameterCollector {
     }
 
     fn visit_const(&mut self, c: &'tcx ty::Const<'tcx>) -> bool {
-        if let ConstValue::Param(data) = c.val {
+        if let ty::ConstKind::Param(data) = c.val {
             self.parameters.push(Parameter::from(data));
         }
         false
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 3d42d5bb0ca..4d8d0040cdc 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -16,7 +16,7 @@ use rustc::infer::region_constraints::{RegionConstraintData, Constraint};
 use rustc::middle::resolve_lifetime as rl;
 use rustc::middle::lang_items;
 use rustc::middle::stability;
-use rustc::mir::interpret::{GlobalId, ConstValue};
+use rustc::mir::interpret::GlobalId;
 use rustc::hir;
 use rustc::hir::def::{CtorKind, DefKind, Res};
 use rustc::hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX, LOCAL_CRATE};
@@ -3075,7 +3075,7 @@ impl<'tcx> Clean<Type> for Ty<'tcx> {
             ty::Slice(ty) => Slice(box ty.clean(cx)),
             ty::Array(ty, n) => {
                 let mut n = cx.tcx.lift(&n).expect("array lift failed");
-                if let ConstValue::Unevaluated(def_id, substs) = n.val {
+                if let ty::ConstKind::Unevaluated(def_id, substs) = n.val {
                     let param_env = cx.tcx.param_env(def_id);
                     let cid = GlobalId {
                         instance: ty::Instance::new(def_id, substs),
@@ -4234,7 +4234,7 @@ fn name_from_pat(p: &hir::Pat) -> String {
 
 fn print_const(cx: &DocContext<'_>, n: &ty::Const<'_>) -> String {
     match n.val {
-        ConstValue::Unevaluated(def_id, _) => {
+        ty::ConstKind::Unevaluated(def_id, _) => {
             if let Some(hir_id) = cx.tcx.hir().as_local_hir_id(def_id) {
                 print_const_expr(cx, cx.tcx.hir().body_owned_by(hir_id))
             } else {
diff --git a/src/test/mir-opt/const_prop/const_prop_fails_gracefully.rs b/src/test/mir-opt/const_prop/const_prop_fails_gracefully.rs
index 85ed8d55b24..34d4a534ad9 100644
--- a/src/test/mir-opt/const_prop/const_prop_fails_gracefully.rs
+++ b/src/test/mir-opt/const_prop/const_prop_fails_gracefully.rs
@@ -25,7 +25,7 @@ fn main() {
 //      ...
 //      _4 = const Scalar(AllocId(1).0x0) : &i32;
 //      _3 = const Scalar(AllocId(1).0x0) : &i32;
-//      _2 = const Scalar(AllocId(1).0x0) : *const i32;
+//      _2 = const Value(Scalar(AllocId(1).0x0)) : *const i32;
 //      ...
 //      _1 = move _2 as usize (Misc);
 //      ...
diff --git a/src/test/ui/symbol-names/impl1.legacy.stderr b/src/test/ui/symbol-names/impl1.legacy.stderr
index b27df10e750..c9495b597eb 100644
--- a/src/test/ui/symbol-names/impl1.legacy.stderr
+++ b/src/test/ui/symbol-names/impl1.legacy.stderr
@@ -46,13 +46,13 @@ error: def-path(bar::<impl foo::Foo>::baz)
 LL |         #[rustc_def_path]
    |         ^^^^^^^^^^^^^^^^^
 
-error: symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17h61b0fcb05ebeeb79E)
+error: symbol-name(_ZN209_$LT$$u5b$$RF$dyn$u20$impl1..Foo$u2b$Assoc$u20$$u3d$$u20$extern$u20$$u22$C$u22$$u20$fn$LP$$RF$u8$C$$u20$...$RP$$u2b$impl1..AutoTrait$u3b$$u20$_$u5d$$u20$as$u20$impl1..main..$u7b$$u7b$closure$u7d$$u7d$..Bar$GT$6method17h92c563325b7ff21aE)
   --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]
    |             ^^^^^^^^^^^^^^^^^^^^
 
-error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method::h61b0fcb05ebeeb79)
+error: demangling(<[&dyn impl1::Foo+Assoc = extern "C" fn(&u8, ::.)+impl1::AutoTrait; _] as impl1::main::{{closure}}::Bar>::method::h92c563325b7ff21a)
   --> $DIR/impl1.rs:61:13
    |
 LL |             #[rustc_symbol_name]