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`

2 files changed, 7 insertions, 11 deletions

diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index 869798d8be1..d766ae37e5b 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/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>()
                     });
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/constant.rs b/compiler/rustc_codegen_ssa/src/mir/constant.rs
index 7676e1e171a..eafc551501c 100644
--- a/compiler/rustc_codegen_ssa/src/mir/constant.rs
+++ b/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