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 https://github.com/rust-lang/rust/issues/131102
supercedes https://github.com/rust-lang/rust/pull/136130

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

3 files changed, 10 insertions, 4 deletions

diff --git a/compiler/rustc_const_eval/src/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/check_consts/qualifs.rs
index e244b50a4b5..5d368b600a0 100644
--- a/compiler/rustc_const_eval/src/check_consts/qualifs.rs
+++ b/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
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index 4ff8aa9a3b4..4d625f76aba 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/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>,
diff --git a/compiler/rustc_const_eval/src/lib.rs b/compiler/rustc_const_eval/src/lib.rs
index b5adf06b300..ecf9745b779 100644
--- a/compiler/rustc_const_eval/src/lib.rs
+++ b/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)