hax Prefer using `rustc_middle::ty` types over `rustc

A number of rustc types have two versions: one in the HIR, the other in rustc_middle::ty. For example GenericParam vs GenericParamDef or WherePredicate vs Predicate. The HIR version is more syntactic, the ty version is more semantic.

We often copy both versions in the frontend, because they happen to show up in other types we need. I propose that when possible we substitute the ty version for the HIR one, as I suspect the ty ones are more convenient to use for our purposes.

Aug 14 '24 08:08 Nadrieril

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Oct 14 '24 02:10 github-actions[bot]

Still relevant

Oct 14 '24 07:10 W95Psp

List of types we can migrate this way:

hir::GenericParam -> ty::GenericParam
hir::Generics -> ty::GenericArg
hir::Ty -> we should never interact with this, only ty::Ty
hir::FieldDef -> ty::FieldDef
hir::FnSig -> ty::PolyFnSig

After that, the most powerful change we could do would be to migrate from hir::Item to hax::FullDef. This would transitively allow removing ~30 hir::* types without needing to add any new ones.

List of `hir::*` types that are only used transitively by one of the above types:

hir::AnonConst
hir::AssocItemKind
hir::ConstArg
hir::ConstArgKind
hir::Constness
hir::EnumDef
hir::FnDecl
hir::FnHeader
hir::FnRetTy
hir::ForeignItem
hir::ForeignItemKind
hir::ForeignItemRef
hir::GenericBounds
hir::GenericParamKind
hir::Impl
hir::ImplItem
hir::ImplItemKind
hir::ImplItemRef
hir::ImplPolarity
hir::IsAsync
hir::IsAuto
hir::ItemId
hir::ItemKind
hir::LifetimeParamKind
hir::Mod
hir::OpaqueTy
hir::OpaqueTyOrigin
hir::ParamName
hir::PathSegment
hir::PrimTy
hir::TraitItem
hir::TraitItemKind
hir::TraitItemRef
hir::UseKind
hir::UsePath
hir::Variant
hir::VariantData

Oct 16 '24 15:10 Nadrieril

This issue has been marked as stale due to a lack of activity for 60 days. If you believe this issue is still relevant, please provide an update or comment to keep it open. Otherwise, it will be closed in 7 days.

Dec 17 '24 02:12 github-actions[bot]

This issue has been marked as stale due to a lack of activity for 60 days. If you believe this issue is still relevant, please provide an update or comment to keep it open. Otherwise, it will be closed in 7 days.

May 15 '25 00:05 github-actions[bot]

We won't implement that, instead we'll switch to FullDef in our Rust engine, and drop the OCaml one along with those HIR types

Jul 03 '25 06:07 W95Psp

Prefer using `rustc_middle::ty` types over `rustc_hir` ones