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_borrowck/src/diagnostics/conflict_errors.rs

@@ -702,7 +702,7 @@ fn suggest_borrow_fn_like(
                 .copied()
                 .find_map(find_fn_kind_from_did),
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => tcx
-                .bound_explicit_item_bounds(def_id)
+                .explicit_item_bounds(def_id)
                 .subst_iter_copied(tcx, substs)
                 .find_map(find_fn_kind_from_did),
             ty::Closure(_, substs) => match substs.as_closure().kind() {

compiler/rustc_hir_analysis/src/check/check.rs

@@ -320,7 +320,7 @@ fn visit_ty(&mut self, arg: &'tcx hir::Ty<'tcx>) {
         };
         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 @@ fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'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 @@ fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<!> {
                 }
             });
             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.explicit_item_bounds(def_id).map_bound(|bounds| {
-        tcx,
+        tcx.mk_predicates_from_iter(util::elaborate(
-        tcx.explicit_item_bounds(def_id).iter().map(|&(bound, _span)| bound),
+            tcx,
-    ));
+            bounds.iter().map(|&(bound, _span)| bound),
-    ty::EarlyBinder(bounds)
+        ))
+    })
 }

compiler/rustc_hir_analysis/src/variance/mod.rs

@@ -153,8 +153,7 @@ fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
     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() {
+    for (pred, _) in tcx.explicit_item_bounds(item_def_id).subst_iter_copied(tcx, id_substs) {
-        let pred = pred.map_bound(|(pred, _)| *pred).subst(tcx, id_substs);
         debug!(?pred);
 
         // We only ignore opaque type substs if the opaque type is the outermost type.

compiler/rustc_hir_typeck/src/_match.rs

@@ -530,7 +530,7 @@ pub(crate) fn opt_suggest_box_span(
                 for ty in [first_ty, second_ty] {
                     for (pred, _) in self
                         .tcx
-                        .bound_explicit_item_bounds(rpit_def_id)
+                        .explicit_item_bounds(rpit_def_id)
                         .subst_iter_copied(self.tcx, substs)
                     {
                         let pred = pred.kind().rebind(match pred.kind().skip_binder() {

compiler/rustc_hir_typeck/src/closure.rs

@@ -172,7 +172,7 @@ fn deduce_closure_signature(
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => self
                 .deduce_closure_signature_from_predicates(
                     expected_ty,
-                    self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs),
+                    self.tcx.explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs),
                 ),
             ty::Dynamic(ref object_type, ..) => {
                 let sig = object_type.projection_bounds().find_map(|pb| {
@@ -713,13 +713,13 @@ fn deduce_future_output_from_obligations(
             }
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => self
                 .tcx
-                .bound_explicit_item_bounds(def_id)
+                .explicit_item_bounds(def_id)
                 .subst_iter_copied(self.tcx, substs)
                 .find_map(|(p, s)| get_future_output(p, s))?,
             ty::Error(_) => return None,
             ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => self
                 .tcx
-                .bound_explicit_item_bounds(proj.def_id)
+                .explicit_item_bounds(proj.def_id)
                 .subst_iter_copied(self.tcx, proj.substs)
                 .find_map(|(p, s)| get_future_output(p, s))?,
             _ => span_bug!(

compiler/rustc_hir_typeck/src/generator_interior/mod.rs

@@ -571,7 +571,7 @@ fn check_must_not_suspend_ty<'tcx>(
         // FIXME: support adding the attribute to TAITs
         ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
             let mut has_emitted = false;
-            for &(predicate, _) in fcx.tcx.explicit_item_bounds(def) {
+            for &(predicate, _) in fcx.tcx.explicit_item_bounds(def).skip_binder() {
                 // We only look at the `DefId`, so it is safe to skip the binder here.
                 if let ty::PredicateKind::Clause(ty::Clause::Trait(ref poly_trait_predicate)) =
                     predicate.kind().skip_binder()

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

@@ -402,7 +402,7 @@ pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
         let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
         let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
 
-        self.tcx.bound_explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
+        self.tcx.explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
             |(predicate, _)| {
                 predicate
                     .kind()

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -540,7 +540,7 @@ fn register_hidden_type(
                 .obligations;
         }
 
-        let item_bounds = tcx.bound_explicit_item_bounds(def_id.to_def_id());
+        let item_bounds = tcx.explicit_item_bounds(def_id);
 
         for (predicate, _) in item_bounds.subst_iter_copied(tcx, substs) {
             let predicate = predicate.fold_with(&mut BottomUpFolder {

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -74,7 +74,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
         // For every projection predicate in the opaque type's explicit bounds,
         // check that the type that we're assigning actually satisfies the bounds
         // of the associated type.
-        for &(pred, pred_span) in cx.tcx.explicit_item_bounds(def_id) {
+        for (pred, pred_span) in cx.tcx.explicit_item_bounds(def_id).subst_identity_iter_copied() {
             // Liberate bound regions in the predicate since we
             // don't actually care about lifetimes in this check.
             let predicate = cx.tcx.liberate_late_bound_regions(def_id, pred.kind());
@@ -112,7 +112,7 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) {
             // with `impl Send: OtherTrait`.
             for (assoc_pred, assoc_pred_span) in cx
                 .tcx
-                .bound_explicit_item_bounds(proj.projection_ty.def_id)
+                .explicit_item_bounds(proj.projection_ty.def_id)
                 .subst_iter_copied(cx.tcx, &proj.projection_ty.substs)
             {
                 let assoc_pred = assoc_pred.fold_with(proj_replacer);

compiler/rustc_lint/src/unused.rs

@@ -254,7 +254,7 @@ fn is_ty_must_use<'tcx>(
                 }
                 ty::Adt(def, _) => is_def_must_use(cx, def.did(), span),
                 ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
-                    elaborate(cx.tcx, cx.tcx.explicit_item_bounds(def).iter().cloned())
+                    elaborate(cx.tcx, cx.tcx.explicit_item_bounds(def).subst_identity_iter_copied())
                         // We only care about self bounds for the impl-trait
                         .filter_only_self()
                         .find_map(|(pred, _span)| {

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -23,7 +23,7 @@
 use rustc_middle::ty::codec::TyDecoder;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::GeneratorDiagnosticData;
-use rustc_middle::ty::{self, ParameterizedOverTcx, Ty, TyCtxt, Visibility};
+use rustc_middle::ty::{self, ParameterizedOverTcx, Predicate, Ty, TyCtxt, Visibility};
 use rustc_serialize::opaque::MemDecoder;
 use rustc_serialize::{Decodable, Decoder};
 use rustc_session::cstore::{
@@ -857,6 +857,20 @@ fn load_proc_macro(self, id: DefIndex, sess: &Session) -> SyntaxExtension {
         )
     }
 
+    fn get_explicit_item_bounds(
+        self,
+        index: DefIndex,
+        tcx: TyCtxt<'tcx>,
+    ) -> ty::EarlyBinder<&'tcx [(Predicate<'tcx>, Span)]> {
+        let lazy = self.root.tables.explicit_item_bounds.get(self, index);
+        let output = if lazy.is_default() {
+            &mut []
+        } else {
+            tcx.arena.alloc_from_iter(lazy.decode((self, tcx)))
+        };
+        ty::EarlyBinder(&*output)
+    }
+
     fn get_variant(self, kind: &DefKind, index: DefIndex, parent_did: DefId) -> ty::VariantDef {
         let adt_kind = match kind {
             DefKind::Variant => ty::AdtKind::Enum,

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -203,7 +203,7 @@ fn into_args(self) -> (DefId, SimplifiedType) {
 }
 
 provide! { tcx, def_id, other, cdata,
-    explicit_item_bounds => { table_defaulted_array }
+    explicit_item_bounds => { cdata.get_explicit_item_bounds(def_id.index, tcx) }
     explicit_predicates_of => { table }
     generics_of => { table }
     inferred_outlives_of => { table_defaulted_array }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1423,7 +1423,7 @@ fn encode_info_for_mod(&mut self, local_def_id: LocalDefId) {
 
     fn encode_explicit_item_bounds(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_explicit_item_bounds({:?})", def_id);
-        let bounds = self.tcx.explicit_item_bounds(def_id);
+        let bounds = self.tcx.explicit_item_bounds(def_id).skip_binder();
         record_defaulted_array!(self.tables.explicit_item_bounds[def_id] <- bounds);
     }
 

compiler/rustc_middle/src/query/mod.rs

@@ -251,7 +251,7 @@
     /// `key` is the `DefId` of the associated type or opaque type.
     ///
     /// Bounds from the parent (e.g. with nested impl trait) are not included.
-    query explicit_item_bounds(key: DefId) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
+    query explicit_item_bounds(key: DefId) -> ty::EarlyBinder<&'tcx [(ty::Predicate<'tcx>, Span)]> {
         desc { |tcx| "finding item bounds for `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern

compiler/rustc_middle/src/ty/context.rs

@@ -1603,7 +1603,7 @@ pub fn ty_is_opaque_future(self, ty: Ty<'_>) -> bool {
         let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = ty.kind() else { return false };
         let future_trait = self.require_lang_item(LangItem::Future, None);
 
-        self.explicit_item_bounds(def_id).iter().any(|(predicate, _)| {
+        self.explicit_item_bounds(def_id).skip_binder().iter().any(|&(predicate, _)| {
             let ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) = predicate.kind().skip_binder() else {
                 return false;
             };

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -914,7 +914,7 @@ fn pretty_print_opaque_impl_type(
 
         // Grab the "TraitA + TraitB" from `impl TraitA + TraitB`,
         // by looking up the projections associated with the def_id.
-        let bounds = tcx.bound_explicit_item_bounds(def_id);
+        let bounds = tcx.explicit_item_bounds(def_id);
 
         let mut traits = FxIndexMap::default();
         let mut fn_traits = FxIndexMap::default();

compiler/rustc_middle/src/ty/subst.rs

@@ -612,6 +612,12 @@ pub fn subst_iter(
     ) -> SubstIter<'s, 'tcx, I> {
         SubstIter { it: self.0.into_iter(), tcx, substs }
     }
+
+    /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
+    /// but on an iterator of `TypeFoldable` values.
+    pub fn subst_identity_iter(self) -> I::IntoIter {
+        self.0.into_iter()
+    }
 }
 
 pub struct SubstIter<'s, 'tcx, I: IntoIterator> {
@@ -664,6 +670,12 @@ pub fn subst_iter_copied(
     ) -> SubstIterCopied<'s, 'tcx, I> {
         SubstIterCopied { it: self.0.into_iter(), tcx, substs }
     }
+
+    /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
+    /// but on an iterator of values that deref to a `TypeFoldable`.
+    pub fn subst_identity_iter_copied(self) -> impl Iterator<Item = <I::Item as Deref>::Target> {
+        self.0.into_iter().map(|v| *v)
+    }
 }
 
 pub struct SubstIterCopied<'a, 'tcx, I: IntoIterator> {

compiler/rustc_middle/src/ty/util.rs

@@ -701,13 +701,6 @@ pub fn try_expand_impl_trait_type(
         if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
     }
 
-    pub fn bound_explicit_item_bounds(
-        self,
-        def_id: DefId,
-    ) -> ty::EarlyBinder<&'tcx [(ty::Predicate<'tcx>, rustc_span::Span)]> {
-        ty::EarlyBinder(self.explicit_item_bounds(def_id))
-    }
-
     /// Returns names of captured upvars for closures and generators.
     ///
     /// Here are some examples:

compiler/rustc_mir_transform/src/generator.rs

@@ -1800,7 +1800,7 @@ fn check_must_not_suspend_ty<'tcx>(
         // FIXME: support adding the attribute to TAITs
         ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
             let mut has_emitted = false;
-            for &(predicate, _) in tcx.explicit_item_bounds(def) {
+            for &(predicate, _) in tcx.explicit_item_bounds(def).skip_binder() {
                 // We only look at the `DefId`, so it is safe to skip the binder here.
                 if let ty::PredicateKind::Clause(ty::Clause::Trait(ref poly_trait_predicate)) =
                     predicate.kind().skip_binder()

compiler/rustc_privacy/src/lib.rs

@@ -269,7 +269,7 @@ fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<V::BreakTy> {
                     // and are visited by shallow visitors.
                     self.visit_predicates(ty::GenericPredicates {
                         parent: None,
-                        predicates: tcx.explicit_item_bounds(def_id),
+                        predicates: tcx.explicit_item_bounds(def_id).skip_binder(),
                     })?;
                 }
             }
@@ -1784,7 +1784,7 @@ fn predicates(&mut self) -> &mut Self {
     fn bounds(&mut self) -> &mut Self {
         self.visit_predicates(ty::GenericPredicates {
             parent: None,
-            predicates: self.tcx.explicit_item_bounds(self.item_def_id),
+            predicates: self.tcx.explicit_item_bounds(self.item_def_id).skip_binder(),
         });
         self
     }

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -297,8 +297,8 @@ fn predicates_reference_self(
     tcx.associated_items(trait_def_id)
         .in_definition_order()
         .filter(|item| item.kind == ty::AssocKind::Type)
-        .flat_map(|item| tcx.explicit_item_bounds(item.def_id))
+        .flat_map(|item| tcx.explicit_item_bounds(item.def_id).subst_identity_iter_copied())
-        .filter_map(|pred_span| predicate_references_self(tcx, *pred_span))
+        .filter_map(|pred_span| predicate_references_self(tcx, pred_span))
         .collect()
 }
 

compiler/rustc_traits/src/chalk/db.rs

@@ -50,12 +50,11 @@ fn bounds_for<T>(&self, def_id: DefId, bound_vars: SubstsRef<'tcx>) -> Vec<T>
     where
         ty::Predicate<'tcx>: LowerInto<'tcx, std::option::Option<T>>,
     {
-        let bounds = self.interner.tcx.bound_explicit_item_bounds(def_id);
+        self.interner
-        bounds
+            .tcx
-            .0
+            .explicit_item_bounds(def_id)
-            .iter()
+            .subst_iter_copied(self.interner.tcx, &bound_vars)
-            .map(|(bound, _)| bounds.rebind(*bound).subst(self.interner.tcx, &bound_vars))
+            .filter_map(|(bound, _)| LowerInto::<Option<_>>::lower_into(bound, self.interner))
-            .filter_map(|bound| LowerInto::<Option<_>>::lower_into(bound, self.interner))
             .collect()
     }
 }
@@ -506,15 +505,11 @@ fn opaque_ty_data(
 
         let identity_substs = InternalSubsts::identity_for_item(self.interner.tcx, opaque_ty_id.0);
 
-        let explicit_item_bounds = self.interner.tcx.bound_explicit_item_bounds(opaque_ty_id.0);
+        let explicit_item_bounds = self.interner.tcx.explicit_item_bounds(opaque_ty_id.0);
         let bounds =
             explicit_item_bounds
-                .0
+                .subst_iter_copied(self.interner.tcx, &bound_vars)
-                .iter()
                 .map(|(bound, _)| {
-                    explicit_item_bounds.rebind(*bound).subst(self.interner.tcx, &bound_vars)
-                })
-                .map(|bound| {
                     bound.fold_with(&mut ReplaceOpaqueTyFolder {
                         tcx: self.interner.tcx,
                         opaque_ty_id,

src/librustdoc/clean/mod.rs

@@ -422,8 +422,8 @@ fn clean_projection<'tcx>(
         let bounds = cx
             .tcx
             .explicit_item_bounds(ty.skip_binder().def_id)
-            .iter()
+            .subst_iter_copied(cx.tcx, ty.skip_binder().substs)
-            .map(|(bound, _)| EarlyBinder(*bound).subst(cx.tcx, ty.skip_binder().substs))
+            .map(|(pred, _)| pred)
             .collect::<Vec<_>>();
         return clean_middle_opaque_bounds(cx, bounds);
     }
@@ -1315,10 +1315,11 @@ fn param_eq_arg(param: &GenericParamDef, arg: &GenericArg) -> bool {
             }
 
             if let ty::TraitContainer = assoc_item.container {
-                let bounds = tcx.explicit_item_bounds(assoc_item.def_id);
+                let bounds =
+                    tcx.explicit_item_bounds(assoc_item.def_id).subst_identity_iter_copied();
                 let predicates = tcx.explicit_predicates_of(assoc_item.def_id).predicates;
                 let predicates =
-                    tcx.arena.alloc_from_iter(bounds.into_iter().chain(predicates).copied());
+                    tcx.arena.alloc_from_iter(bounds.chain(predicates.iter().copied()));
                 let mut generics = clean_ty_generics(
                     cx,
                     tcx.generics_of(assoc_item.def_id),
@@ -1845,8 +1846,8 @@ pub(crate) fn clean_middle_ty<'tcx>(
             let bounds = cx
                 .tcx
                 .explicit_item_bounds(def_id)
-                .iter()
+                .subst_iter_copied(cx.tcx, substs)
-                .map(|(bound, _)| EarlyBinder(*bound).subst(cx.tcx, substs))
+                .map(|(bound, _)| bound)
                 .collect::<Vec<_>>();
             clean_middle_opaque_bounds(cx, bounds)
         }

src/tools/clippy/clippy_lints/src/future_not_send.rs

@@ -4,7 +4,7 @@
 use rustc_hir::{Body, FnDecl};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::{self, AliasTy, Clause, EarlyBinder, PredicateKind};
+use rustc_middle::ty::{self, AliasTy, Clause, PredicateKind};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span};
@@ -66,8 +66,7 @@ fn check_fn(
         if let ty::Alias(ty::Opaque, AliasTy { def_id, substs, .. }) = *ret_ty.kind() {
             let preds = cx.tcx.explicit_item_bounds(def_id);
             let mut is_future = false;
-            for &(p, _span) in preds {
+            for (p, _span) in preds.subst_iter_copied(cx.tcx, substs) {
-                let p = EarlyBinder(p).subst(cx.tcx, substs);
                 if let Some(trait_pred) = p.to_opt_poly_trait_pred() {
                     if Some(trait_pred.skip_binder().trait_ref.def_id) == cx.tcx.lang_items().future_trait() {
                         is_future = true;

src/tools/clippy/clippy_utils/src/ty.rs

@@ -90,7 +90,7 @@ fn contains_ty_adt_constructor_opaque_inner<'tcx>(
                         return false;
                     }
 
-                    for &(predicate, _span) in cx.tcx.explicit_item_bounds(def_id) {
+                    for (predicate, _span) in cx.tcx.explicit_item_bounds(def_id).subst_identity_iter_copied() {
                         match predicate.kind().skip_binder() {
                             // For `impl Trait<U>`, it will register a predicate of `T: Trait<U>`, so we go through
                             // and check substituions to find `U`.
@@ -267,7 +267,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         },
         ty::Tuple(substs) => substs.iter().any(|ty| is_must_use_ty(cx, ty)),
         ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
-            for (predicate, _) in cx.tcx.explicit_item_bounds(*def_id) {
+            for (predicate, _) in cx.tcx.explicit_item_bounds(def_id).skip_binder() {
                 if let ty::PredicateKind::Clause(ty::Clause::Trait(trait_predicate)) = predicate.kind().skip_binder() {
                     if cx.tcx.has_attr(trait_predicate.trait_ref.def_id, sym::must_use) {
                         return true;
@@ -743,7 +743,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: AliasTy<'tcx>) -> Option
 
     for (pred, _) in cx
         .tcx
-        .bound_explicit_item_bounds(ty.def_id)
+        .explicit_item_bounds(ty.def_id)
         .subst_iter_copied(cx.tcx, ty.substs)
     {
         match pred.kind().skip_binder() {