Stop using ty::Const in deref_const and destructure_const in preparation of value trees making such operations on ty::Const obsolete.

Author: oli-obk

compiler/rustc_codegen_ssa/src/mir/constant.rs

@@ -57,15 +57,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) -> (Bx::Value, Ty<'tcx>) {
         constant
             .map(|val| {
-                let field_ty = ty.builtin_index().unwrap();
-                let c = ty::Const::from_value(bx.tcx(), val, ty);
                 let values: Vec<_> = bx
                     .tcx()
-                    .destructure_const(ty::ParamEnv::reveal_all().and(&c))
+                    .destructure_const(ty::ParamEnv::reveal_all().and((val, ty)))
                     .fields
                     .iter()
-                    .map(|field| {
-                        if let Some(prim) = field.val.try_to_scalar() {
+                    .map(|(field, field_ty)| {
+                        if let Some(prim) = field.try_to_scalar() {
                             let layout = bx.layout_of(field_ty);
                             let scalar = match layout.abi {
                                 Abi::Scalar(ref x) => x,
@@ -78,7 +76,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     })
                     .collect();
                 let llval = bx.const_struct(&values, false);
-                (llval, c.ty)
+                (llval, ty)
             })
             .unwrap_or_else(|_| {
                 bx.tcx().sess.span_err(span, "could not evaluate shuffle_indices at compile time");

compiler/rustc_middle/src/mir/mod.rs

@@ -2506,6 +2506,27 @@ impl ConstantKind<'tcx> {
         }
     }
 
+    #[inline]
+    /// Panics if the value cannot be evaluated or doesn't contain a valid integer of the given type.
+    pub fn eval_bits(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        param_env: ty::ParamEnv<'tcx>,
+        ty: Ty<'tcx>,
+    ) -> u128 {
+        match self {
+            Self::Ty(ct) => ct.eval_bits(tcx, param_env, ty),
+            Self::Val(val, t) => {
+                assert_eq!(*t, ty);
+                let size = tcx
+                    .layout_of(param_env.with_reveal_all_normalized(tcx).and(ty))
+                    .expect("could not normalize type")
+                    .size;
+                val.try_to_scalar_int().unwrap().assert_bits(size)
+            }
+        }
+    }
+
     #[inline]
     pub fn try_eval_bool(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Option<bool> {
         match self {

compiler/rustc_middle/src/mir/query.rs

@@ -15,7 +15,7 @@ use smallvec::SmallVec;
 use std::cell::Cell;
 use std::fmt::{self, Debug};
 
-use super::{Field, SourceInfo};
+use super::{interpret::ConstValue, Field, SourceInfo};
 
 #[derive(Copy, Clone, PartialEq, TyEncodable, TyDecodable, HashStable, Debug)]
 pub enum UnsafetyViolationKind {
@@ -386,7 +386,7 @@ pub enum ClosureOutlivesSubject<'tcx> {
 #[derive(Copy, Clone, Debug, HashStable)]
 pub struct DestructuredConst<'tcx> {
     pub variant: Option<VariantIdx>,
-    pub fields: &'tcx [&'tcx ty::Const<'tcx>],
+    pub fields: &'tcx [(ConstValue<'tcx>, Ty<'tcx>)],
 }
 
 /// Coverage information summarized from a MIR if instrumented for source code coverage (see

compiler/rustc_middle/src/mir/type_foldable.rs

@@ -367,3 +367,13 @@ impl<'tcx> TypeFoldable<'tcx> for ConstantKind<'tcx> {
         }
     }
 }
+
+impl<'tcx> TypeFoldable<'tcx> for interpret::ConstValue<'tcx> {
+    fn super_fold_with<F: TypeFolder<'tcx>>(self, _folder: &mut F) -> Self {
+        self
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        ControlFlow::CONTINUE
+    }
+}

compiler/rustc_middle/src/query/mod.rs

@@ -808,16 +808,16 @@ rustc_queries! {
     /// Destructure a constant ADT or array into its variant index and its
     /// field values.
     query destructure_const(
-        key: ty::ParamEnvAnd<'tcx, &'tcx ty::Const<'tcx>>
+        key: ty::ParamEnvAnd<'tcx, (ConstValue<'tcx>, Ty<'tcx>)>
     ) -> mir::DestructuredConst<'tcx> {
         desc { "destructure constant" }
     }
 
     /// Dereference a constant reference or raw pointer and turn the result into a constant
     /// again.
     query deref_const(
-        key: ty::ParamEnvAnd<'tcx, &'tcx ty::Const<'tcx>>
-    ) -> &'tcx ty::Const<'tcx> {
+        key: ty::ParamEnvAnd<'tcx, (ConstValue<'tcx>, Ty<'tcx>)>
+    ) -> (ConstValue<'tcx>, Ty<'tcx>) {
         desc { "deref constant" }
     }
 

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1190,10 +1190,8 @@ pub trait PrettyPrinter<'tcx>:
             // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
             // correct `ty::ParamEnv` to allow printing *all* constant values.
             (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_param_types_or_consts() => {
-                let contents = self.tcx().destructure_const(
-                    ty::ParamEnv::reveal_all()
-                        .and(self.tcx().mk_const(ty::Const { val: ty::ConstKind::Value(ct), ty })),
-                );
+                let contents =
+                    self.tcx().destructure_const(ty::ParamEnv::reveal_all().and((ct, ty)));
                 let fields = contents.fields.iter().copied();
 
                 match *ty.kind() {

compiler/rustc_middle/src/ty/relate.rs

@@ -515,7 +515,7 @@ pub fn super_relate_consts<R: TypeRelation<'tcx>>(
         (ty::ConstKind::Param(a_p), ty::ConstKind::Param(b_p)) => a_p.index == b_p.index,
         (ty::ConstKind::Placeholder(p1), ty::ConstKind::Placeholder(p2)) => p1 == p2,
         (ty::ConstKind::Value(a_val), ty::ConstKind::Value(b_val)) => {
-            check_const_value_eq(relation, a_val, b_val, a, b)?
+            check_const_value_eq(relation, a_val, b_val, a.ty, b.ty)?
         }
 
         (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu))
@@ -550,10 +550,8 @@ fn check_const_value_eq<R: TypeRelation<'tcx>>(
     relation: &mut R,
     a_val: ConstValue<'tcx>,
     b_val: ConstValue<'tcx>,
-    // FIXME(oli-obk): these arguments should go away with valtrees
-    a: &'tcx ty::Const<'tcx>,
-    b: &'tcx ty::Const<'tcx>,
-    // FIXME(oli-obk): this should just be `bool` with valtrees
+    a_ty: Ty<'tcx>,
+    b_ty: Ty<'tcx>,
 ) -> RelateResult<'tcx, bool> {
     let tcx = relation.tcx();
     Ok(match (a_val, b_val) {
@@ -575,13 +573,19 @@ fn check_const_value_eq<R: TypeRelation<'tcx>>(
         }
 
         (ConstValue::ByRef { .. }, ConstValue::ByRef { .. }) => {
-            let a_destructured = tcx.destructure_const(relation.param_env().and(a));
-            let b_destructured = tcx.destructure_const(relation.param_env().and(b));
+            let a_destructured = tcx.destructure_const(relation.param_env().and((a_val, a_ty)));
+            let b_destructured = tcx.destructure_const(relation.param_env().and((b_val, b_ty)));
 
             // Both the variant and each field have to be equal.
             if a_destructured.variant == b_destructured.variant {
-                for (a_field, b_field) in iter::zip(a_destructured.fields, b_destructured.fields) {
-                    relation.consts(a_field, b_field)?;
+                for (&(a_val, a_ty), &(b_val, b_ty)) in iter::zip(a_destructured.fields, b_destructured.fields)
+                {
+                    let is_match = check_const_value_eq(relation, a_val, b_val, a_ty, b_ty)?;
+                    if !is_match {
+                        let a = ty::Const::from_value(relation.tcx(), a_val, a_ty);
+                        let b = ty::Const::from_value(relation.tcx(), b_val, b_ty);
+                        return Err(TypeError::ConstMismatch(expected_found(relation, a, b)));
+                    }
                 }
 
                 true

compiler/rustc_mir/src/const_eval/mod.rs

@@ -3,7 +3,7 @@
 use std::convert::TryFrom;
 
 use rustc_hir::Mutability;
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::{
     mir::{self, interpret::ConstAlloc},
     ty::ScalarInt,
@@ -139,14 +139,15 @@ fn const_to_valtree_inner<'tcx>(
 pub(crate) fn destructure_const<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    val: &'tcx ty::Const<'tcx>,
+    val: ConstValue<'tcx>,
+    ty: Ty<'tcx>,
 ) -> mir::DestructuredConst<'tcx> {
     trace!("destructure_const: {:?}", val);
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
-    let op = ecx.const_to_op(val, None).unwrap();
+    let op = ecx.const_val_to_op(val, ty, None).unwrap();
 
     // We go to `usize` as we cannot allocate anything bigger anyway.
-    let (field_count, variant, down) = match val.ty.kind() {
+    let (field_count, variant, down) = match op.layout.ty.kind() {
         ty::Array(_, len) => (usize::try_from(len.eval_usize(tcx, param_env)).unwrap(), None, op),
         ty::Adt(def, _) if def.variants.is_empty() => {
             return mir::DestructuredConst { variant: None, fields: &[] };
@@ -163,7 +164,7 @@ pub(crate) fn destructure_const<'tcx>(
     let fields_iter = (0..field_count).map(|i| {
         let field_op = ecx.operand_field(&down, i).unwrap();
         let val = op_to_const(&ecx, &field_op);
-        ty::Const::from_value(tcx, val, field_op.layout.ty)
+        (val, field_op.layout.ty)
     });
     let fields = tcx.arena.alloc_from_iter(fields_iter);
 
@@ -173,11 +174,12 @@ pub(crate) fn destructure_const<'tcx>(
 pub(crate) fn deref_const<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
-    val: &'tcx ty::Const<'tcx>,
-) -> &'tcx ty::Const<'tcx> {
+    val: ConstValue<'tcx>,
+    ty: Ty<'tcx>,
+) -> (ConstValue<'tcx>, Ty<'tcx>) {
     trace!("deref_const: {:?}", val);
     let ecx = mk_eval_cx(tcx, DUMMY_SP, param_env, false);
-    let op = ecx.const_to_op(val, None).unwrap();
+    let op = ecx.const_val_to_op(val, ty, None).unwrap();
     let mplace = ecx.deref_operand(&op).unwrap();
     if let Scalar::Ptr(ptr) = mplace.ptr {
         assert_eq!(
@@ -203,5 +205,5 @@ pub(crate) fn deref_const<'tcx>(
         },
     };
 
-    tcx.mk_const(ty::Const { val: ty::ConstKind::Value(op_to_const(&ecx, &mplace.into())), ty })
+    (op_to_const(&ecx, &mplace.into()), ty)
 }

compiler/rustc_mir/src/lib.rs

@@ -62,15 +62,15 @@ pub fn provide(providers: &mut Providers) {
     providers.mir_callgraph_reachable = transform::inline::cycle::mir_callgraph_reachable;
     providers.mir_inliner_callees = transform::inline::cycle::mir_inliner_callees;
     providers.destructure_const = |tcx, param_env_and_value| {
-        let (param_env, value) = param_env_and_value.into_parts();
-        const_eval::destructure_const(tcx, param_env, value)
+        let (param_env, (value, ty)) = param_env_and_value.into_parts();
+        const_eval::destructure_const(tcx, param_env, value, ty)
     };
     providers.const_to_valtree = |tcx, param_env_and_value| {
         let (param_env, raw) = param_env_and_value.into_parts();
         const_eval::const_to_valtree(tcx, param_env, raw)
     };
     providers.deref_const = |tcx, param_env_and_value| {
-        let (param_env, value) = param_env_and_value.into_parts();
-        const_eval::deref_const(tcx, param_env, value)
+        let (param_env, (value, ty)) = param_env_and_value.into_parts();
+        const_eval::deref_const(tcx, param_env, value, ty)
     };
 }

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

@@ -2,6 +2,7 @@ use rustc_hir as hir;
 use rustc_index::vec::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::mir::Field;
+use rustc_middle::mir::interpret::ConstValue;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
 use rustc_session::lint;
@@ -248,11 +249,13 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
 
     fn field_pats(
         &self,
-        vals: impl Iterator<Item = &'tcx ty::Const<'tcx>>,
+        vals: impl Iterator<Item = (ConstValue<'tcx>, Ty<'tcx>)>,
     ) -> Result<Vec<FieldPat<'tcx>>, FallbackToConstRef> {
+        let tcx = self.tcx();
         vals.enumerate()
-            .map(|(idx, val)| {
+            .map(|(idx, (val, ty))| {
                 let field = Field::new(idx);
+                let val = ty::Const::from_value(tcx, val, ty);
                 Ok(FieldPat { field, pattern: self.recur(val, false)? })
             })
             .collect()
@@ -356,7 +359,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 PatKind::Wild
             }
             ty::Adt(adt_def, substs) if adt_def.is_enum() => {
-                let destructured = tcx.destructure_const(param_env.and(cv));
+                let destructured = tcx.destructure_const(param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)));
                 PatKind::Variant {
                     adt_def,
                     substs,
@@ -367,15 +370,15 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 }
             }
             ty::Tuple(_) | ty::Adt(_, _) => {
-                let destructured = tcx.destructure_const(param_env.and(cv));
+                let destructured = tcx.destructure_const(param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)));
                 PatKind::Leaf { subpatterns: self.field_pats(destructured.fields.iter().copied())? }
             }
             ty::Array(..) => PatKind::Array {
                 prefix: tcx
-                    .destructure_const(param_env.and(cv))
+                    .destructure_const(param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)))
                     .fields
                     .iter()
-                    .map(|val| self.recur(val, false))
+                    .map(|&(val, ty)| self.recur(ty::Const::from_value(tcx, val, ty), false))
                     .collect::<Result<_, _>>()?,
                 slice: None,
                 suffix: Vec::new(),
@@ -403,15 +406,15 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 // arrays.
                 ty::Array(..) if !self.treat_byte_string_as_slice => {
                     let old = self.behind_reference.replace(true);
-                    let array = tcx.deref_const(self.param_env.and(cv));
+                    let array = tcx.deref_const(self.param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)));
                     let val = PatKind::Deref {
                         subpattern: Pat {
                             kind: Box::new(PatKind::Array {
                                 prefix: tcx
                                     .destructure_const(param_env.and(array))
                                     .fields
                                     .iter()
-                                    .map(|val| self.recur(val, false))
+                                    .map(|&(val, ty)| self.recur(ty::Const::from_value(tcx, val, ty), false))
                                     .collect::<Result<_, _>>()?,
                                 slice: None,
                                 suffix: vec![],
@@ -429,15 +432,15 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 // pattern.
                 ty::Slice(elem_ty) => {
                     let old = self.behind_reference.replace(true);
-                    let array = tcx.deref_const(self.param_env.and(cv));
+                    let array = tcx.deref_const(self.param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)));
                     let val = PatKind::Deref {
                         subpattern: Pat {
                             kind: Box::new(PatKind::Slice {
                                 prefix: tcx
                                     .destructure_const(param_env.and(array))
                                     .fields
                                     .iter()
-                                    .map(|val| self.recur(val, false))
+                                    .map(|&(val, ty)| self.recur(ty::Const::from_value(tcx, val, ty), false))
                                     .collect::<Result<_, _>>()?,
                                 slice: None,
                                 suffix: vec![],
@@ -492,7 +495,9 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                     // we fall back to a const pattern. If we do not do this, we may end up with
                     // a !structural-match constant that is not of reference type, which makes it
                     // very hard to invoke `PartialEq::eq` on it as a fallback.
-                    let val = match self.recur(tcx.deref_const(self.param_env.and(cv)), false) {
+                    let (val, ty) = tcx.deref_const(self.param_env.and((cv.val.eval(tcx, param_env).try_to_value().unwrap(), cv.ty)));
+                    let deref_cv = ty::Const::from_value(tcx, val, ty);
+                    let val = match self.recur(deref_cv, false) {
                         Ok(subpattern) => PatKind::Deref { subpattern },
                         Err(_) => PatKind::Constant { value: cv },
                     };