Remove Representability.

Its last meaningful uses were removed in rust-lang#153493.

Author: nnethercote

compiler/rustc_middle/src/queries.rs

@@ -588,8 +588,9 @@ rustc_queries! {
     }
 
     /// Checks whether a type is representable or infinitely sized
-    query check_representability(key: LocalDefId) -> rustc_middle::ty::Representability {
+    query check_representability(key: LocalDefId) {
         desc { "checking if `{}` is representable", tcx.def_path_str(key) }
+        // njn: update comment
         // Infinitely sized types will cause a cycle. The custom `FromCycleError` impl for
         // `Representability` will print a custom error about the infinite size and then abort
         // compilation. (In the past we recovered and continued, but in practice that leads to
@@ -604,7 +605,7 @@ rustc_queries! {
 
     /// An implementation detail for the `check_representability` query. See that query for more
     /// details, particularly on the modifiers.
-    query check_representability_adt_ty(key: Ty<'tcx>) -> rustc_middle::ty::Representability {
+    query check_representability_adt_ty(key: Ty<'tcx>) {
         desc { "checking if `{}` is representable", key }
         cycle_delay_bug
         anon

compiler/rustc_middle/src/query/erase.rs

@@ -395,7 +395,6 @@ impl_erasable_for_simple_types! {
     rustc_middle::ty::Destructor,
     rustc_middle::ty::fast_reject::SimplifiedType,
     rustc_middle::ty::ImplPolarity,
-    rustc_middle::ty::Representability,
     rustc_middle::ty::UnusedGenericParams,
     rustc_middle::ty::util::AlwaysRequiresDrop,
     rustc_middle::ty::Visibility<rustc_span::def_id::DefId>,

compiler/rustc_middle/src/ty/adt.rs

@@ -751,8 +751,3 @@ impl<'tcx> AdtDef<'tcx> {
         if self.is_struct() { tcx.adt_sizedness_constraint((self.did(), sizedness)) } else { None }
     }
 }
-
-/// This type exists just so a `FromCycleError` impl can be made for the `check_representability`
-/// query.
-#[derive(Clone, Copy, Debug, HashStable)]
-pub struct Representability;

compiler/rustc_ty_utils/src/representability.rs

@@ -2,7 +2,7 @@ use rustc_hir::def::DefKind;
 use rustc_index::bit_set::DenseBitSet;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, Representability, Ty, TyCtxt};
+use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::LocalDefId;
 
 pub(crate) fn provide(providers: &mut Providers) {
@@ -14,7 +14,7 @@ pub(crate) fn provide(providers: &mut Providers) {
     };
 }
 
-fn check_representability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Representability {
+fn check_representability(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     match tcx.def_kind(def_id) {
         DefKind::Struct | DefKind::Union | DefKind::Enum => {
             for variant in tcx.adt_def(def_id).variants() {
@@ -28,7 +28,6 @@ fn check_representability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Representabili
         }
         def_kind => bug!("unexpected {def_kind:?}"),
     }
-    Representability
 }
 
 fn check_representability_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) {
@@ -67,7 +66,7 @@ fn check_representability_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) {
 // Looking at the query cycle above, we know that `Bar` is representable
 // because `check_representability_adt_ty(Bar<..>)` is in the cycle and
 // `check_representability(Bar)` is *not* in the cycle.
-fn check_representability_adt_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Representability {
+fn check_representability_adt_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) {
     let ty::Adt(adt, args) = ty.kind() else { bug!("expected adt") };
     if let Some(def_id) = adt.did().as_local() {
         let _ = tcx.check_representability(def_id);
@@ -82,7 +81,6 @@ fn check_representability_adt_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Repre
             }
         }
     }
-    Representability
 }
 
 fn params_in_repr(tcx: TyCtxt<'_>, def_id: LocalDefId) -> DenseBitSet<u32> {