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

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),
                 }
             )

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()
                     }
                 })

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.

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 {

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)

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.

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,
                     }),

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)

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() {

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

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);
                 }
                 _ => {}

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,

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