Rollup merge of #110556 - kylematsuda:earlybinder-explicit-item-bounds, r=compiler-errors

Switch to `EarlyBinder` for `explicit_item_bounds`

Part of the work to finish https://github.com/rust-lang/rust/issues/105779.

This PR adds `EarlyBinder` to the return type of the `explicit_item_bounds` query and removes `bound_explicit_item_bounds`.

r? `@compiler-errors` (hope it's okay to request you, since you reviewed #110299 and #110498 😃)

compiler/rustc_hir_analysis/src/check/check.rs

@@ -320,7 +320,7 @@ pub(super) fn check_opaque_for_inheriting_lifetimes(
         };
         let prohibit_opaque = tcx
             .explicit_item_bounds(def_id)
-            .iter()
+            .subst_identity_iter_copied()
             .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
 
         if let Some(ty) = prohibit_opaque.break_value() {

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -839,7 +839,7 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'_, 'tcx> {
             });
             self.types.insert(proj.def_id, (infer_ty, proj.substs));
             // Recurse into bounds
-            for (pred, pred_span) in self.interner().bound_explicit_item_bounds(proj.def_id).subst_iter_copied(self.interner(), proj.substs) {
+            for (pred, pred_span) in self.interner().explicit_item_bounds(proj.def_id).subst_iter_copied(self.interner(), proj.substs) {
                 let pred = pred.fold_with(self);
                 let pred = self.ocx.normalize(
                     &ObligationCause::misc(self.span, self.body_id),
@@ -2023,7 +2023,7 @@ pub(super) fn check_type_bounds<'tcx>(
     };
 
     let obligations: Vec<_> = tcx
-        .bound_explicit_item_bounds(trait_ty.def_id)
+        .explicit_item_bounds(trait_ty.def_id)
         .subst_iter_copied(tcx, rebased_substs)
         .map(|(concrete_ty_bound, span)| {
             debug!("check_type_bounds: concrete_ty_bound = {:?}", concrete_ty_bound);

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -360,7 +360,9 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRe
                             tcx,
                             param_env,
                             item_def_id,
-                            tcx.explicit_item_bounds(item_def_id).to_vec(),
+                            tcx.explicit_item_bounds(item_def_id)
+                                .subst_identity_iter_copied()
+                                .collect::<Vec<_>>(),
                             &FxIndexSet::default(),
                             gat_def_id.def_id,
                             gat_generics,
@@ -1125,7 +1127,7 @@ fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocIt
     let bounds = wfcx.tcx().explicit_item_bounds(item.def_id);
 
     debug!("check_associated_type_bounds: bounds={:?}", bounds);
-    let wf_obligations = bounds.iter().flat_map(|&(bound, bound_span)| {
+    let wf_obligations = bounds.subst_identity_iter_copied().flat_map(|(bound, bound_span)| {
         let normalized_bound = wfcx.normalize(span, None, bound);
         traits::wf::predicate_obligations(
             wfcx.infcx,
@@ -1588,7 +1590,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
                 }
             });
             for (bound, bound_span) in tcx
-                .bound_explicit_item_bounds(opaque_ty.def_id)
+                .explicit_item_bounds(opaque_ty.def_id)
                 .subst_iter_copied(tcx, opaque_ty.substs)
             {
                 let bound = self.wfcx.normalize(bound_span, None, bound);

compiler/rustc_hir_analysis/src/collect/item_bounds.rs

@@ -79,14 +79,14 @@ fn opaque_type_bounds<'tcx>(
 pub(super) fn explicit_item_bounds(
     tcx: TyCtxt<'_>,
     def_id: LocalDefId,
-) -> &'_ [(ty::Predicate<'_>, Span)] {
+) -> ty::EarlyBinder<&'_ [(ty::Predicate<'_>, Span)]> {
     match tcx.opt_rpitit_info(def_id.to_def_id()) {
         // RPITIT's bounds are the same as opaque type bounds, but with
         // a projection self type.
         Some(ty::ImplTraitInTraitData::Trait { opaque_def_id, .. }) => {
             let item = tcx.hir().get_by_def_id(opaque_def_id.expect_local()).expect_item();
             let opaque_ty = item.expect_opaque_ty();
-            return opaque_type_bounds(
+            return ty::EarlyBinder(opaque_type_bounds(
                 tcx,
                 opaque_def_id.expect_local(),
                 opaque_ty.bounds,
@@ -95,7 +95,7 @@ pub(super) fn explicit_item_bounds(
                     ty::InternalSubsts::identity_for_item(tcx, def_id),
                 ),
                 item.span,
-            );
+            ));
         }
         // These should have been fed!
         Some(ty::ImplTraitInTraitData::Impl { .. }) => unreachable!(),
@@ -103,7 +103,7 @@ pub(super) fn explicit_item_bounds(
     }
 
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
-    match tcx.hir().get(hir_id) {
+    let bounds = match tcx.hir().get(hir_id) {
         hir::Node::TraitItem(hir::TraitItem {
             kind: hir::TraitItemKind::Type(bounds, _),
             span,
@@ -123,16 +123,18 @@ pub(super) fn explicit_item_bounds(
             opaque_type_bounds(tcx, def_id, bounds, item_ty, *span)
         }
         _ => bug!("item_bounds called on {:?}", def_id),
-    }
+    };
+    ty::EarlyBinder(bounds)
 }
 
 pub(super) fn item_bounds(
     tcx: TyCtxt<'_>,
     def_id: DefId,
 ) -> ty::EarlyBinder<&'_ ty::List<ty::Predicate<'_>>> {
-    let bounds = tcx.mk_predicates_from_iter(util::elaborate(
-        tcx,
-        tcx.explicit_item_bounds(def_id).iter().map(|&(bound, _span)| bound),
-    ));
-    ty::EarlyBinder(bounds)
+    tcx.explicit_item_bounds(def_id).map_bound(|bounds| {
+        tcx.mk_predicates_from_iter(util::elaborate(
+            tcx,
+            bounds.iter().map(|&(bound, _span)| bound),
+        ))
+    })
 }

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -153,8 +153,7 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
     let mut collector =
         OpaqueTypeLifetimeCollector { tcx, root_def_id: item_def_id.to_def_id(), variances };
     let id_substs = ty::InternalSubsts::identity_for_item(tcx, item_def_id);
-    for pred in tcx.bound_explicit_item_bounds(item_def_id.to_def_id()).transpose_iter() {
-        let pred = pred.map_bound(|(pred, _)| *pred).subst(tcx, id_substs);
+    for (pred, _) in tcx.explicit_item_bounds(item_def_id).subst_iter_copied(tcx, id_substs) {
         debug!(?pred);
 
         // We only ignore opaque type substs if the opaque type is the outermost type.