Move struct placeholder pt2 #150271

Jamesbarford · 2025-12-22T15:02:51Z

r? ghost

compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs

lcnr · 2025-12-30T09:56:51Z

compiler/rustc_infer/src/infer/region_constraints/mod.rs

 pub enum GenericKind<'tcx> {
    Param(ty::ParamTy),
-    Placeholder(ty::PlaceholderType<'tcx>),
+    Placeholder(ty::PlaceholderType<TyCtxt<'tcx>>),


there are currently a bunch of spurious edits + outdated formatting things here 🤔

Woops, yes, I'm sorting things out bit by bit. I'll squash all the commits when I'm done and remove the odd edits and commented out code.

I'm getting the following error and I'm not too sure why as I'm using #[derive_where(HashStable_NoContext)];

error[E0599]: the method `hash_stable` exists for reference `&binder::BoundRegion`, but its trait bounds were not satisfied --> compiler/rustc_type_ir/src/region_kind.rs:228:19 | 228 | r.hash_stable(hcx, hasher); | ^^^^^^^^^^^ method cannot be called on `&binder::BoundRegion` due to unsatisfied trait bounds | ::: compiler/rustc_type_ir/src/binder.rs:1014:1 | 1014 | pub enum BoundRegionKind<I: Interner> { | ------------------------------------- doesn't satisfy `BoundRegionKind: HashStable<_>` ... 1083 | pub struct BoundRegion<I: Interner> { | ----------------------------------- doesn't satisfy `binder::BoundRegion: HashStable<_>` | = note: trait bound `BoundRegionKind: HashStable<_>` was not satisfied = note: the following trait bounds were not satisfied: `binder::BoundRegion: HashStable<_>` which is required by `&binder::BoundRegion: HashStable<_>` note: the trait `HashStable` must be implemented --> /rust/compiler/rustc_data_structures/src/stable_hasher.rs:44:1 | 44 | pub trait HashStable<CTX> { | ^^^^^^^^^^^^^^^^^^^^^^^^^ error[E0599]: the method `hash_stable` exists for reference `&binder::Placeholder<I, binder::BoundRegion>`, but its trait bounds were not satisfied --> compiler/rustc_type_ir/src/region_kind.rs:237:19 | 237 | r.hash_stable(hcx, hasher); | ^^^^^^^^^^^ method cannot be called on `&binder::Placeholder<I, binder::BoundRegion>` due to unsatisfied trait bounds | ::: compiler/rustc_type_ir/src/binder.rs:969:1 | 969 | pub struct Placeholder<I: Interner, T> { | -------------------------------------- doesn't satisfy `_: HashStable<_>` ... 1083 | pub struct BoundRegion<I: Interner> { | ----------------------------------- doesn't satisfy `binder::BoundRegion: HashStable<_>` | = note: trait bound `binder::BoundRegion: HashStable<_>` was not satisfied = note: the following trait bounds were not satisfied: `binder::Placeholder<I, binder::BoundRegion>: HashStable<_>` which is required by `&binder::Placeholder<I, binder::BoundRegion>: HashStable<_>` note: the trait `HashStable` must be implemented --> /rust/compiler/rustc_data_structures/src/stable_hasher.rs:44:1 | 44 | pub trait HashStable<CTX> { | ^^^^^^^^^^^^^^^^^^^^^^^^^

lcnr · 2026-01-05T15:13:32Z

compiler/rustc_infer/src/infer/outlives/obligations.rs

        origin: infer::SubregionOrigin<'tcx>,
        region: ty::Region<'tcx>,
-        placeholder_ty: ty::PlaceholderType<'tcx>,
+        placeholder_ty: ty::PlaceholderType<TyCtxt<'tcx>>,


unnecessary change

lcnr · 2026-01-05T15:14:00Z

compiler/rustc_middle/src/ty/region.rs

+//    fn new(var: BoundVar, kind: BoundRegionKind) -> Self {
+//        Self { var, kind }
+//    }
+//}


lcnr · 2026-01-05T15:14:41Z

compiler/rustc_next_trait_solver/src/placeholder.rs

+    mapped_regions: IndexMap<I::PlaceholderRegion, ty::BoundRegion>,
+    mapped_types: IndexMap<I::PlaceholderTy, ty::BoundTy>,


why does PlaceholderRegion and PlaceholderTy still exist? 🤔

lcnr · 2026-01-05T15:15:55Z

compiler/rustc_type_ir/src/binder.rs

+#[derive_where(Clone, Ord, Hash; I: Interner, T)]
 #[derive_where(PartialOrd; I: Interner, T: Ord)]
 #[derive_where(Copy; I: Interner, T: Copy, T)]
 #[derive_where(Eq; T)]
+#[derive_where(PartialEq; T)]


what's going on there. Why do we sometimes not require I: Interner. Having just T there seems odd and unnecessary?

lcnr · 2026-01-05T15:19:42Z

compiler/rustc_type_ir/src/binder.rs

+
+pub type PlaceholderConst<I: Interner> = ty::Placeholder<I, BoundConst>;
+
+impl<I: Interner> PlaceholderLike<I> for PlaceholderConst<I> {


no longer need the trait, can just use inherent methods now

lcnr · 2026-01-05T15:23:22Z

compiler/rustc_type_ir/src/interner.rs

    type ParamTy: ParamLike;
-    type BoundTy: BoundVarLike<Self>;
-    type PlaceholderTy: PlaceholderLike<Self, Bound = Self::BoundTy>;
+    type PlaceholderTy: PlaceholderLike<Self, Bound = ty::BoundTy<Self>>;


should also be removed

lcnr · 2026-01-05T15:26:13Z

The reason HashStable isn't implemented is kinda stupid.

HashStable_NoContext is a "perfect derive", i.e. we simply add where-clauses that each field implements the trait. This means the derive for BoundRegionKind adds I::DefId: HasHStable<CTX> and I::Symbol: HashStable<CTX>. These are then considered to not hold in the manual impl. Though tbf, I don't get why the manual impl exists at all.

Try to replace the manual impl with a derive and see if anything breaks. If it does break, add I::DefId: HashStable<CTX> and I::Symbol: HashStable<CTX> to the manual impl

implementation of `HashStable`

rust-log-analyzer · 2026-01-15T14:54:34Z

The job aarch64-gnu-llvm-20-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

fmt: checked 6649 files
tidy check
tidy [rustdoc_json (src)]: `rustdoc-json-types` modified, checking format version
tidy: Skipping binary file check, read-only filesystem
tidy [style (compiler)]: /checkout/compiler/rustc_type_ir/src/binder.rs:1027: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy [style (compiler)]: /checkout/compiler/rustc_type_ir/src/binder.rs:1054: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy [style (compiler)]: FAIL
tidy: The following check failed: style (compiler)
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage1-tools-bin/rust-tidy /checkout /checkout/obj/build/aarch64-unknown-linux-gnu/stage0/bin/cargo /checkout/obj/build 4 yarn` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1612:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1357:29

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tests --skip coverage-map --skip coverage-run --skip library --skip tidyselftest`
Build completed unsuccessfully in 0:00:54
  local time: Thu Jan 15 14:50:37 UTC 2026
  network time: Thu, 15 Jan 2026 14:50:38 GMT
##[error]Process completed with exit code 1.

lcnr · 2026-01-15T21:39:31Z

compiler/rustc_public/src/mir/body.rs

 }

-impl Rvalue {
+impl<'tcx> Rvalue<'tcx> {


rustc_public should use owned values everywhere

lcnr · 2026-01-15T21:40:27Z

compiler/rustc_public/src/ty.rs

+pub enum RegionKind<'tcx> {
    ReEarlyParam(EarlyParamRegion),
-    ReBound(DebruijnIndex, BoundRegion),
+    ReBound(DebruijnIndex, BoundRegion<'tcx>),


instead duplicate the BoundRegion struct in rustc_public