Rollup merge of #136180 - lukas-code:typed-valtree, r=oli-obk

Introduce a wrapper for "typed valtrees" and properly check the type before extracting the value

This PR adds a new wrapper type `ty::Value` to replace the tuple `(Ty, ty::ValTree)` and become the new canonical representation of type-level constant values.

The value extraction methods `try_to_bits`/`try_to_bool`/`try_to_target_usize` are moved to this new type. For `try_to_bits` in particular, this avoids some redundant matches on `ty::ConstKind::Value`. Furthermore, these methods and will now properly check the type before extracting the value, which fixes some ICEs.

The name `ty::Value` was chosen to be consistent with `ty::Expr`.

Commit 1 should be non-functional and commit 2 adds the type check.

---

fixes #131102
supercedes #136130

r? `@oli-obk`
cc `@FedericoBruzzone` `@BoxyUwU`

Author: matthiaskrgr

compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs

@@ -129,12 +129,7 @@ pub(super) fn codegen_simd_intrinsic_call<'tcx>(
                 return;
             }
 
-            let idx = generic_args[2]
-                .expect_const()
-                .try_to_valtree()
-                .expect("expected monomorphic const in codegen")
-                .0
-                .unwrap_branch();
+            let idx = generic_args[2].expect_const().to_value().valtree.unwrap_branch();
 
             assert_eq!(x.layout(), y.layout());
             let layout = x.layout();

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1329,7 +1329,7 @@ fn generic_simd_intrinsic<'ll, 'tcx>(
     }
 
     if name == sym::simd_shuffle_generic {
-        let idx = fn_args[2].expect_const().try_to_valtree().unwrap().0.unwrap_branch();
+        let idx = fn_args[2].expect_const().to_value().valtree.unwrap_branch();
         let n = idx.len() as u64;
 
         let (out_len, out_ty) = require_simd!(ret_ty, SimdReturn);

compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs

@@ -673,25 +673,23 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
         ty::ConstKind::Param(param) => {
             write!(output, "{}", param.name)
         }
-        ty::ConstKind::Value(ty, valtree) => {
-            match ty.kind() {
+        ty::ConstKind::Value(cv) => {
+            match cv.ty.kind() {
                 ty::Int(ity) => {
-                    // FIXME: directly extract the bits from a valtree instead of evaluating an
-                    // already evaluated `Const` in order to get the bits.
-                    let bits = ct
+                    let bits = cv
                         .try_to_bits(tcx, ty::TypingEnv::fully_monomorphized())
                         .expect("expected monomorphic const in codegen");
                     let val = Integer::from_int_ty(&tcx, *ity).size().sign_extend(bits) as i128;
                     write!(output, "{val}")
                 }
                 ty::Uint(_) => {
-                    let val = ct
+                    let val = cv
                         .try_to_bits(tcx, ty::TypingEnv::fully_monomorphized())
                         .expect("expected monomorphic const in codegen");
                     write!(output, "{val}")
                 }
                 ty::Bool => {
-                    let val = ct.try_to_bool().expect("expected monomorphic const in codegen");
+                    let val = cv.try_to_bool().expect("expected monomorphic const in codegen");
                     write!(output, "{val}")
                 }
                 _ => {
@@ -703,9 +701,7 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
                     // avoiding collisions and will make the emitted type names shorter.
                     let hash_short = tcx.with_stable_hashing_context(|mut hcx| {
                         let mut hasher = StableHasher::new();
-                        hcx.while_hashing_spans(false, |hcx| {
-                            (ty, valtree).hash_stable(hcx, &mut hasher)
-                        });
+                        hcx.while_hashing_spans(false, |hcx| cv.hash_stable(hcx, &mut hasher));
                         hasher.finish::<Hash64>()
                     });
 

compiler/rustc_codegen_ssa/src/mir/constant.rs

@@ -43,7 +43,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             mir::Const::Ty(_, c) => match c.kind() {
                 // A constant that came from a const generic but was then used as an argument to
                 // old-style simd_shuffle (passing as argument instead of as a generic param).
-                rustc_type_ir::ConstKind::Value(_, valtree) => return Ok(Ok(valtree)),
+                rustc_type_ir::ConstKind::Value(cv) => return Ok(Ok(cv.valtree)),
                 other => span_bug!(constant.span, "{other:#?}"),
             },
             // We should never encounter `Const::Val` unless MIR opts (like const prop) evaluate

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -345,7 +345,7 @@ where
         Const::Ty(_, ct)
             if matches!(
                 ct.kind(),
-                ty::ConstKind::Param(_) | ty::ConstKind::Error(_) | ty::ConstKind::Value(_, _)
+                ty::ConstKind::Param(_) | ty::ConstKind::Error(_) | ty::ConstKind::Value(_)
             ) =>
         {
             None

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -272,7 +272,8 @@ pub(crate) fn eval_to_valtree<'tcx>(
 
 /// Converts a `ValTree` to a `ConstValue`, which is needed after mir
 /// construction has finished.
-// FIXME Merge `valtree_to_const_value` and `valtree_into_mplace` into one function
+// FIXME(valtrees): Merge `valtree_to_const_value` and `valtree_into_mplace` into one function
+// FIXME(valtrees): Accept `ty::Value` instead of `Ty` and `ty::ValTree` separately.
 #[instrument(skip(tcx), level = "debug", ret)]
 pub fn valtree_to_const_value<'tcx>(
     tcx: TyCtxt<'tcx>,

compiler/rustc_const_eval/src/lib.rs

@@ -46,8 +46,13 @@ pub fn provide(providers: &mut Providers) {
     };
     providers.hooks.try_destructure_mir_constant_for_user_output =
         const_eval::try_destructure_mir_constant_for_user_output;
-    providers.valtree_to_const_val = |tcx, (ty, valtree)| {
-        const_eval::valtree_to_const_value(tcx, ty::TypingEnv::fully_monomorphized(), ty, valtree)
+    providers.valtree_to_const_val = |tcx, cv| {
+        const_eval::valtree_to_const_value(
+            tcx,
+            ty::TypingEnv::fully_monomorphized(),
+            cv.ty,
+            cv.valtree,
+        )
     };
     providers.check_validity_requirement = |tcx, (init_kind, param_env_and_ty)| {
         util::check_validity_requirement(tcx, init_kind, param_env_and_ty)

compiler/rustc_infer/src/infer/freshen.rs

@@ -170,7 +170,7 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for TypeFreshener<'a, 'tcx> {
             }
 
             ty::ConstKind::Param(_)
-            | ty::ConstKind::Value(_, _)
+            | ty::ConstKind::Value(_)
             | ty::ConstKind::Unevaluated(..)
             | ty::ConstKind::Expr(..)
             | ty::ConstKind::Error(_) => ct.super_fold_with(self),

compiler/rustc_infer/src/infer/mod.rs

@@ -1055,7 +1055,7 @@ impl<'tcx> InferCtxt<'tcx> {
             | ty::ConstKind::Bound(_, _)
             | ty::ConstKind::Placeholder(_)
             | ty::ConstKind::Unevaluated(_)
-            | ty::ConstKind::Value(_, _)
+            | ty::ConstKind::Value(_)
             | ty::ConstKind::Error(_)
             | ty::ConstKind::Expr(_) => ct,
         }

compiler/rustc_middle/src/mir/consts.rs

@@ -250,7 +250,7 @@ impl<'tcx> Const<'tcx> {
                     // Dont use the outer ty as on invalid code we can wind up with them not being the same.
                     // this then results in allowing const eval to add `1_i64 + 1_usize` in cases where the mir
                     // was originally `({N: usize} + 1_usize)` under `generic_const_exprs`.
-                    ty::ConstKind::Value(ty, _) => ty,
+                    ty::ConstKind::Value(cv) => cv.ty,
                     _ => *ty,
                 }
             }
@@ -264,7 +264,7 @@ impl<'tcx> Const<'tcx> {
     pub fn is_required_const(&self) -> bool {
         match self {
             Const::Ty(_, c) => match c.kind() {
-                ty::ConstKind::Value(_, _) => false, // already a value, cannot error
+                ty::ConstKind::Value(_) => false, // already a value, cannot error
                 _ => true,
             },
             Const::Val(..) => false, // already a value, cannot error
@@ -276,11 +276,11 @@ impl<'tcx> Const<'tcx> {
     pub fn try_to_scalar(self) -> Option<Scalar> {
         match self {
             Const::Ty(_, c) => match c.kind() {
-                ty::ConstKind::Value(ty, valtree) if ty.is_primitive() => {
+                ty::ConstKind::Value(cv) if cv.ty.is_primitive() => {
                     // A valtree of a type where leaves directly represent the scalar const value.
                     // Just checking whether it is a leaf is insufficient as e.g. references are leafs
                     // but the leaf value is the value they point to, not the reference itself!
-                    Some(valtree.unwrap_leaf().into())
+                    Some(cv.valtree.unwrap_leaf().into())
                 }
                 _ => None,
             },
@@ -295,9 +295,7 @@ impl<'tcx> Const<'tcx> {
         match self {
             Const::Val(ConstValue::Scalar(Scalar::Int(x)), _) => Some(x),
             Const::Ty(_, c) => match c.kind() {
-                ty::ConstKind::Value(ty, valtree) if ty.is_primitive() => {
-                    Some(valtree.unwrap_leaf())
-                }
+                ty::ConstKind::Value(cv) if cv.ty.is_primitive() => Some(cv.valtree.unwrap_leaf()),
                 _ => None,
             },
             _ => None,
@@ -328,7 +326,7 @@ impl<'tcx> Const<'tcx> {
                 }
 
                 match c.kind() {
-                    ConstKind::Value(ty, val) => Ok(tcx.valtree_to_const_val((ty, val))),
+                    ConstKind::Value(cv) => Ok(tcx.valtree_to_const_val(cv)),
                     ConstKind::Expr(_) => {
                         bug!("Normalization of `ty::ConstKind::Expr` is unimplemented")
                     }
@@ -353,13 +351,13 @@ impl<'tcx> Const<'tcx> {
         typing_env: ty::TypingEnv<'tcx>,
     ) -> Option<Scalar> {
         if let Const::Ty(_, c) = self
-            && let ty::ConstKind::Value(ty, val) = c.kind()
-            && ty.is_primitive()
+            && let ty::ConstKind::Value(cv) = c.kind()
+            && cv.ty.is_primitive()
         {
             // Avoid the `valtree_to_const_val` query. Can only be done on primitive types that
             // are valtree leaves, and *not* on references. (References should return the
             // pointer here, which valtrees don't represent.)
-            Some(val.unwrap_leaf().into())
+            Some(cv.valtree.unwrap_leaf().into())
         } else {
             self.eval(tcx, typing_env, DUMMY_SP).ok()?.try_to_scalar()
         }
@@ -473,7 +471,7 @@ impl<'tcx> Const<'tcx> {
                 // A valtree may be a reference. Valtree references correspond to a
                 // different allocation each time they are evaluated. Valtrees for primitive
                 // types are fine though.
-                ty::ConstKind::Value(ty, _) => ty.is_primitive(),
+                ty::ConstKind::Value(cv) => cv.ty.is_primitive(),
                 ty::ConstKind::Unevaluated(..) | ty::ConstKind::Expr(..) => false,
                 // This can happen if evaluation of a constant failed. The result does not matter
                 // much since compilation is doomed.