Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 462 insertions, 275 deletions

diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index ed60998ec..ccc9f8084 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -9,7 +9,7 @@ use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_session::lint;
 use rustc_span::symbol::{kw, Symbol};
-use rustc_span::Span;
+use rustc_span::{sym, Span};
 
 pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     use rustc_hir::*;
@@ -50,7 +50,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                 // We do not allow generic parameters in anon consts if we are inside
                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
                 None
-            } else if tcx.lazy_normalization() {
+            } else if tcx.features().generic_const_exprs {
                 let parent_node = tcx.hir().get_parent(hir_id);
                 if let Node::Variant(Variant { disr_expr: Some(constant), .. }) = parent_node
                     && constant.hir_id == hir_id
@@ -101,6 +101,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                         param_def_id_to_index,
                         has_self: generics.has_self,
                         has_late_bound_regions: generics.has_late_bound_regions,
+                        host_effect_index: None,
                     };
                 } else {
                     // HACK(eddyb) this provides the correct generics when
@@ -123,9 +124,6 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     {
                         Some(parent_def_id.to_def_id())
                     }
-                    Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
-                        Some(tcx.typeck_root_def_id(def_id.to_def_id()))
-                    }
                     // Exclude `GlobalAsm` here which cannot have generics.
                     Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
                         if asm.operands.iter().any(|(op, _op_sp)| match op {
@@ -142,11 +140,12 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                 }
             }
         }
-        Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
+        Node::ConstBlock(_)
+        | Node::Expr(&hir::Expr { kind: hir::ExprKind::Closure { .. }, .. }) => {
             Some(tcx.typeck_root_def_id(def_id.to_def_id()))
         }
         Node::Item(item) => match item.kind {
-            ItemKind::OpaqueTy(hir::OpaqueTy {
+            ItemKind::OpaqueTy(&hir::OpaqueTy {
                 origin:
                     hir::OpaqueTyOrigin::FnReturn(fn_def_id) | hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
                 in_trait,
@@ -228,10 +227,12 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     let has_self = opt_self.is_some();
     let mut parent_has_self = false;
     let mut own_start = has_self as u32;
+    let mut host_effect_index = None;
     let parent_count = parent_def_id.map_or(0, |def_id| {
         let generics = tcx.generics_of(def_id);
         assert!(!has_self);
         parent_has_self = generics.has_self;
+        host_effect_index = generics.host_effect_index;
         own_start = generics.count() as u32;
         generics.parent_count + generics.params.len()
     });
@@ -253,11 +254,11 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
 
     // Now create the real type and const parameters.
     let type_start = own_start - has_self as u32 + params.len() as u32;
-    let mut i = 0;
+    let mut i: u32 = 0;
     let mut next_index = || {
         let prev = i;
         i += 1;
-        prev as u32 + type_start
+        prev + type_start
     };
 
     const TYPE_DEFAULT_NOT_ALLOWED: &'static str = "defaults for type parameters are only allowed in \
@@ -297,7 +298,13 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
             })
         }
         GenericParamKind::Const { default, .. } => {
-            if !matches!(allow_defaults, Defaults::Allowed) && default.is_some() {
+            let is_host_param = tcx.has_attr(param.def_id, sym::rustc_host);
+
+            if !matches!(allow_defaults, Defaults::Allowed)
+                && default.is_some()
+                // `rustc_host` effect params are allowed to have defaults.
+                && !is_host_param
+            {
                 tcx.sess.span_err(
                     param.span,
                     "defaults for const parameters are only allowed in \
@@ -305,8 +312,18 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                 );
             }
 
+            let index = next_index();
+
+            if is_host_param {
+                if let Some(idx) = host_effect_index {
+                    bug!("parent also has host effect param? index: {idx}, def: {def_id:?}");
+                }
+
+                host_effect_index = Some(parent_count + index as usize);
+            }
+
             Some(ty::GenericParamDef {
-                index: next_index(),
+                index,
                 name: param.name.ident().name,
                 def_id: param.def_id.to_def_id(),
                 pure_wrt_drop: param.pure_wrt_drop,
@@ -339,17 +356,14 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     }
 
     // provide junk type parameter defs for const blocks.
-    if let Node::AnonConst(_) = node {
-        let parent_node = tcx.hir().get_parent(hir_id);
-        if let Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) = parent_node {
-            params.push(ty::GenericParamDef {
-                index: next_index(),
-                name: Symbol::intern("<const_ty>"),
-                def_id: def_id.to_def_id(),
-                pure_wrt_drop: false,
-                kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
-            });
-        }
+    if let Node::ConstBlock(_) = node {
+        params.push(ty::GenericParamDef {
+            index: next_index(),
+            name: Symbol::intern("<const_ty>"),
+            def_id: def_id.to_def_id(),
+            pure_wrt_drop: false,
+            kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
+        });
     }
 
     let param_def_id_to_index = params.iter().map(|param| (param.def_id, param.index)).collect();
@@ -361,6 +375,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
         param_def_id_to_index,
         has_self: has_self || parent_has_self,
         has_late_bound_regions: has_late_bound_regions(tcx, node),
+        host_effect_index,
     }
 }
 
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index 948b903e5..57f74172e 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -1,5 +1,5 @@
 use super::ItemCtxt;
-use crate::astconv::{AstConv, OnlySelfBounds};
+use crate::astconv::{AstConv, PredicateFilter};
 use rustc_hir as hir;
 use rustc_infer::traits::util;
 use rustc_middle::ty::subst::InternalSubsts;
@@ -19,32 +19,34 @@ fn associated_type_bounds<'tcx>(
     assoc_item_def_id: LocalDefId,
     ast_bounds: &'tcx [hir::GenericBound<'tcx>],
     span: Span,
-) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
-    let item_ty = tcx.mk_projection(
+) -> &'tcx [(ty::Clause<'tcx>, Span)] {
+    let item_ty = Ty::new_projection(
+        tcx,
         assoc_item_def_id.to_def_id(),
         InternalSubsts::identity_for_item(tcx, assoc_item_def_id),
     );
 
     let icx = ItemCtxt::new(tcx, assoc_item_def_id);
-    let mut bounds = icx.astconv().compute_bounds(item_ty, ast_bounds, OnlySelfBounds(false));
+    let mut bounds = icx.astconv().compute_bounds(item_ty, ast_bounds, PredicateFilter::All);
     // Associated types are implicitly sized unless a `?Sized` bound is found
     icx.astconv().add_implicitly_sized(&mut bounds, item_ty, ast_bounds, None, span);
 
     let trait_def_id = tcx.local_parent(assoc_item_def_id);
     let trait_predicates = tcx.trait_explicit_predicates_and_bounds(trait_def_id);
 
-    let bounds_from_parent = trait_predicates.predicates.iter().copied().filter(|(pred, _)| {
-        match pred.kind().skip_binder() {
-            ty::PredicateKind::Clause(ty::Clause::Trait(tr)) => tr.self_ty() == item_ty,
-            ty::PredicateKind::Clause(ty::Clause::Projection(proj)) => {
-                proj.projection_ty.self_ty() == item_ty
-            }
-            ty::PredicateKind::Clause(ty::Clause::TypeOutlives(outlives)) => outlives.0 == item_ty,
+    let bounds_from_parent = trait_predicates
+        .predicates
+        .iter()
+        .copied()
+        .filter(|(pred, _)| match pred.kind().skip_binder() {
+            ty::ClauseKind::Trait(tr) => tr.self_ty() == item_ty,
+            ty::ClauseKind::Projection(proj) => proj.projection_ty.self_ty() == item_ty,
+            ty::ClauseKind::TypeOutlives(outlives) => outlives.0 == item_ty,
             _ => false,
-        }
-    });
+        })
+        .map(|(clause, span)| (clause, span));
 
-    let all_bounds = tcx.arena.alloc_from_iter(bounds.predicates().chain(bounds_from_parent));
+    let all_bounds = tcx.arena.alloc_from_iter(bounds.clauses().chain(bounds_from_parent));
     debug!(
         "associated_type_bounds({}) = {:?}",
         tcx.def_path_str(assoc_item_def_id.to_def_id()),
@@ -64,33 +66,34 @@ fn opaque_type_bounds<'tcx>(
     ast_bounds: &'tcx [hir::GenericBound<'tcx>],
     item_ty: Ty<'tcx>,
     span: Span,
-) -> &'tcx [(ty::Predicate<'tcx>, Span)] {
+) -> &'tcx [(ty::Clause<'tcx>, Span)] {
     ty::print::with_no_queries!({
         let icx = ItemCtxt::new(tcx, opaque_def_id);
-        let mut bounds = icx.astconv().compute_bounds(item_ty, ast_bounds, OnlySelfBounds(false));
+        let mut bounds = icx.astconv().compute_bounds(item_ty, ast_bounds, PredicateFilter::All);
         // Opaque types are implicitly sized unless a `?Sized` bound is found
         icx.astconv().add_implicitly_sized(&mut bounds, item_ty, ast_bounds, None, span);
         debug!(?bounds);
 
-        tcx.arena.alloc_from_iter(bounds.predicates())
+        tcx.arena.alloc_from_iter(bounds.clauses())
     })
 }
 
 pub(super) fn explicit_item_bounds(
     tcx: TyCtxt<'_>,
     def_id: LocalDefId,
-) -> ty::EarlyBinder<&'_ [(ty::Predicate<'_>, Span)]> {
+) -> ty::EarlyBinder<&'_ [(ty::Clause<'_>, 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 ty::EarlyBinder(opaque_type_bounds(
+            return ty::EarlyBinder::bind(opaque_type_bounds(
                 tcx,
                 opaque_def_id.expect_local(),
                 opaque_ty.bounds,
-                tcx.mk_projection(
+                Ty::new_projection(
+                    tcx,
                     def_id.to_def_id(),
                     ty::InternalSubsts::identity_for_item(tcx, def_id),
                 ),
@@ -116,25 +119,23 @@ pub(super) fn explicit_item_bounds(
         }) => {
             let substs = InternalSubsts::identity_for_item(tcx, def_id);
             let item_ty = if *in_trait && !tcx.lower_impl_trait_in_trait_to_assoc_ty() {
-                tcx.mk_projection(def_id.to_def_id(), substs)
+                Ty::new_projection(tcx, def_id.to_def_id(), substs)
             } else {
-                tcx.mk_opaque(def_id.to_def_id(), substs)
+                Ty::new_opaque(tcx, def_id.to_def_id(), substs)
             };
             opaque_type_bounds(tcx, def_id, bounds, item_ty, *span)
         }
+        hir::Node::Item(hir::Item { kind: hir::ItemKind::TyAlias(..), .. }) => &[],
         _ => bug!("item_bounds called on {:?}", def_id),
     };
-    ty::EarlyBinder(bounds)
+    ty::EarlyBinder::bind(bounds)
 }
 
 pub(super) fn item_bounds(
     tcx: TyCtxt<'_>,
     def_id: DefId,
-) -> ty::EarlyBinder<&'_ ty::List<ty::Predicate<'_>>> {
+) -> ty::EarlyBinder<&'_ ty::List<ty::Clause<'_>>> {
     tcx.explicit_item_bounds(def_id).map_bound(|bounds| {
-        tcx.mk_predicates_from_iter(util::elaborate(
-            tcx,
-            bounds.iter().map(|&(bound, _span)| bound),
-        ))
+        tcx.mk_clauses_from_iter(util::elaborate(tcx, bounds.iter().map(|&(bound, _span)| bound)))
     })
 }
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index e5b5dae55..129366641 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -1,8 +1,8 @@
-use crate::astconv::{AstConv, OnlySelfBounds};
+use crate::astconv::{AstConv, OnlySelfBounds, PredicateFilter};
 use crate::bounds::Bounds;
 use crate::collect::ItemCtxt;
 use crate::constrained_generic_params as cgp;
-use hir::{HirId, Node};
+use hir::{HirId, Lifetime, Node};
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
@@ -10,9 +10,9 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_middle::ty::{GenericPredicates, ToPredicate};
+use rustc_middle::ty::{GenericPredicates, Generics, ImplTraitInTraitData, ToPredicate};
 use rustc_span::symbol::{sym, Ident};
-use rustc_span::{Span, DUMMY_SP};
+use rustc_span::{Span, Symbol, DUMMY_SP};
 
 /// Returns a list of all type predicates (explicit and implicit) for the definition with
 /// ID `def_id`. This includes all predicates returned by `predicates_defined_on`, plus
@@ -62,6 +62,67 @@ pub(super) fn predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericPredic
 fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::GenericPredicates<'_> {
     use rustc_hir::*;
 
+    match tcx.opt_rpitit_info(def_id.to_def_id()) {
+        Some(ImplTraitInTraitData::Trait { opaque_def_id, fn_def_id }) => {
+            let opaque_ty_id = tcx.hir().local_def_id_to_hir_id(opaque_def_id.expect_local());
+            let opaque_ty_node = tcx.hir().get(opaque_ty_id);
+            let Node::Item(&Item { kind: ItemKind::OpaqueTy(OpaqueTy { lifetime_mapping, .. }), .. }) = opaque_ty_node else {
+                bug!("unexpected {opaque_ty_node:?}")
+            };
+
+            let mut predicates = Vec::new();
+
+            // RPITITs should inherit the predicates of their parent. This is
+            // both to ensure that the RPITITs are only instantiated when the
+            // parent predicates would hold, and also so that the param-env
+            // inherits these predicates as assumptions.
+            let identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+            predicates.extend(
+                tcx.explicit_predicates_of(fn_def_id).instantiate_own(tcx, identity_substs),
+            );
+
+            // We also install bidirectional outlives predicates for the RPITIT
+            // to keep the duplicates lifetimes from opaque lowering in sync.
+            compute_bidirectional_outlives_predicates(
+                tcx,
+                def_id,
+                lifetime_mapping.iter().map(|(lifetime, def_id)| {
+                    (*lifetime, (*def_id, lifetime.ident.name, lifetime.ident.span))
+                }),
+                tcx.generics_of(def_id.to_def_id()),
+                &mut predicates,
+            );
+
+            return ty::GenericPredicates {
+                parent: Some(tcx.parent(def_id.to_def_id())),
+                predicates: tcx.arena.alloc_from_iter(predicates),
+            };
+        }
+
+        Some(ImplTraitInTraitData::Impl { fn_def_id }) => {
+            let assoc_item = tcx.associated_item(def_id);
+            let trait_assoc_predicates =
+                tcx.explicit_predicates_of(assoc_item.trait_item_def_id.unwrap());
+
+            let impl_assoc_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+            let impl_def_id = tcx.parent(fn_def_id);
+            let impl_trait_ref_substs =
+                tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity().substs;
+
+            let impl_assoc_substs =
+                impl_assoc_identity_substs.rebase_onto(tcx, impl_def_id, impl_trait_ref_substs);
+
+            let impl_predicates = trait_assoc_predicates.instantiate_own(tcx, impl_assoc_substs);
+
+            return ty::GenericPredicates {
+                parent: Some(impl_def_id),
+                predicates: tcx.arena.alloc_from_iter(impl_predicates),
+            };
+        }
+
+        None => {}
+    }
+
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
     let node = tcx.hir().get(hir_id);
 
@@ -75,7 +136,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
 
     // We use an `IndexSet` to preserve order of insertion.
     // Preserving the order of insertion is important here so as not to break UI tests.
-    let mut predicates: FxIndexSet<(ty::Predicate<'_>, Span)> = FxIndexSet::default();
+    let mut predicates: FxIndexSet<(ty::Clause<'_>, Span)> = FxIndexSet::default();
 
     let ast_generics = match node {
         Node::TraitItem(item) => item.generics,
@@ -125,8 +186,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     if let Some(self_bounds) = is_trait {
         predicates.extend(
             icx.astconv()
-                .compute_bounds(tcx.types.self_param, self_bounds, OnlySelfBounds(false))
-                .predicates(),
+                .compute_bounds(tcx.types.self_param, self_bounds, PredicateFilter::All)
+                .clauses(),
         );
     }
 
@@ -175,22 +236,24 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     param.span,
                 );
                 trace!(?bounds);
-                predicates.extend(bounds.predicates());
+                predicates.extend(bounds.clauses());
                 trace!(?predicates);
             }
             GenericParamKind::Const { .. } => {
                 let name = param.name.ident().name;
                 let param_const = ty::ParamConst::new(index, name);
 
-                let ct_ty = tcx.type_of(param.def_id.to_def_id()).subst_identity();
+                let ct_ty = tcx
+                    .type_of(param.def_id.to_def_id())
+                    .no_bound_vars()
+                    .expect("const parameters cannot be generic");
 
-                let ct = tcx.mk_const(param_const, ct_ty);
+                let ct = ty::Const::new_param(tcx, param_const, ct_ty);
 
-                let predicate = ty::Binder::dummy(ty::PredicateKind::Clause(
-                    ty::Clause::ConstArgHasType(ct, ct_ty),
-                ))
-                .to_predicate(tcx);
-                predicates.insert((predicate, param.span));
+                predicates.insert((
+                    ty::ClauseKind::ConstArgHasType(ct, ct_ty).to_predicate(tcx),
+                    param.span,
+                ));
 
                 index += 1;
             }
@@ -219,7 +282,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     } else {
                         let span = bound_pred.bounded_ty.span;
                         let predicate = ty::Binder::bind_with_vars(
-                            ty::PredicateKind::WellFormed(ty.into()),
+                            ty::ClauseKind::WellFormed(ty.into()),
                             bound_vars,
                         );
                         predicates.insert((predicate.to_predicate(tcx), span));
@@ -234,7 +297,7 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                     bound_vars,
                     OnlySelfBounds(false),
                 );
-                predicates.extend(bounds.predicates());
+                predicates.extend(bounds.clauses());
             }
 
             hir::WherePredicate::RegionPredicate(region_pred) => {
@@ -246,11 +309,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
                         }
                         _ => bug!(),
                     };
-                    let pred = ty::Binder::dummy(ty::PredicateKind::Clause(
-                        ty::Clause::RegionOutlives(ty::OutlivesPredicate(r1, r2)),
-                    ))
-                    .to_predicate(icx.tcx);
-
+                    let pred = ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(r1, r2))
+                        .to_predicate(icx.tcx);
                     (pred, span)
                 }))
             }
@@ -293,39 +353,22 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             bug!("unexpected {opaque_ty_node:?}")
         };
         debug!(?lifetimes);
-        for (arg, duplicate) in std::iter::zip(lifetimes, ast_generics.params) {
-            let hir::GenericArg::Lifetime(arg) = arg else { bug!() };
-            let orig_region = icx.astconv().ast_region_to_region(&arg, None);
-            if !matches!(orig_region.kind(), ty::ReEarlyBound(..)) {
-                // Only early-bound regions can point to the original generic parameter.
-                continue;
-            }
 
-            let hir::GenericParamKind::Lifetime { .. } = duplicate.kind else { continue };
-            let dup_def = duplicate.def_id.to_def_id();
-
-            let Some(dup_index) = generics.param_def_id_to_index(tcx, dup_def) else { bug!() };
-
-            let dup_region = tcx.mk_re_early_bound(ty::EarlyBoundRegion {
-                def_id: dup_def,
-                index: dup_index,
-                name: duplicate.name.ident().name,
-            });
-            predicates.push((
-                ty::Binder::dummy(ty::PredicateKind::Clause(ty::Clause::RegionOutlives(
-                    ty::OutlivesPredicate(orig_region, dup_region),
-                )))
-                .to_predicate(icx.tcx),
-                duplicate.span,
-            ));
-            predicates.push((
-                ty::Binder::dummy(ty::PredicateKind::Clause(ty::Clause::RegionOutlives(
-                    ty::OutlivesPredicate(dup_region, orig_region),
-                )))
-                .to_predicate(icx.tcx),
-                duplicate.span,
-            ));
-        }
+        let lifetime_mapping = std::iter::zip(lifetimes, ast_generics.params)
+            .map(|(arg, dup)| {
+                let hir::GenericArg::Lifetime(arg) = arg else { bug!() };
+                (**arg, dup)
+            })
+            .filter(|(_, dup)| matches!(dup.kind, hir::GenericParamKind::Lifetime { .. }))
+            .map(|(lifetime, dup)| (lifetime, (dup.def_id, dup.name.ident().name, dup.span)));
+
+        compute_bidirectional_outlives_predicates(
+            tcx,
+            def_id,
+            lifetime_mapping,
+            generics,
+            &mut predicates,
+        );
         debug!(?predicates);
     }
 
@@ -335,13 +378,53 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     }
 }
 
+/// Opaques have duplicated lifetimes and we need to compute bidirectional outlives predicates to
+/// enforce that these lifetimes stay in sync.
+fn compute_bidirectional_outlives_predicates<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    item_def_id: LocalDefId,
+    lifetime_mapping: impl Iterator<Item = (Lifetime, (LocalDefId, Symbol, Span))>,
+    generics: &Generics,
+    predicates: &mut Vec<(ty::Clause<'tcx>, Span)>,
+) {
+    let icx = ItemCtxt::new(tcx, item_def_id);
+
+    for (arg, (dup_def, name, span)) in lifetime_mapping {
+        let orig_region = icx.astconv().ast_region_to_region(&arg, None);
+        if !matches!(orig_region.kind(), ty::ReEarlyBound(..)) {
+            // There is no late-bound lifetime to actually match up here, since the lifetime doesn't
+            // show up in the opaque's parent's substs.
+            continue;
+        }
+
+        let Some(dup_index) = generics.param_def_id_to_index(icx.tcx, dup_def.to_def_id()) else { bug!() };
+
+        let dup_region = ty::Region::new_early_bound(
+            tcx,
+            ty::EarlyBoundRegion { def_id: dup_def.to_def_id(), index: dup_index, name },
+        );
+
+        predicates.push((
+            ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(orig_region, dup_region))
+                .to_predicate(tcx),
+            span,
+        ));
+
+        predicates.push((
+            ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(dup_region, orig_region))
+                .to_predicate(tcx),
+            span,
+        ));
+    }
+}
+
 fn const_evaluatable_predicates_of(
     tcx: TyCtxt<'_>,
     def_id: LocalDefId,
-) -> FxIndexSet<(ty::Predicate<'_>, Span)> {
+) -> FxIndexSet<(ty::Clause<'_>, Span)> {
     struct ConstCollector<'tcx> {
         tcx: TyCtxt<'tcx>,
-        preds: FxIndexSet<(ty::Predicate<'tcx>, Span)>,
+        preds: FxIndexSet<(ty::Clause<'tcx>, Span)>,
     }
 
     impl<'tcx> intravisit::Visitor<'tcx> for ConstCollector<'tcx> {
@@ -349,11 +432,8 @@ fn const_evaluatable_predicates_of(
             let ct = ty::Const::from_anon_const(self.tcx, c.def_id);
             if let ty::ConstKind::Unevaluated(_) = ct.kind() {
                 let span = self.tcx.def_span(c.def_id);
-                self.preds.insert((
-                    ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(ct))
-                        .to_predicate(self.tcx),
-                    span,
-                ));
+                self.preds
+                    .insert((ty::ClauseKind::ConstEvaluatable(ct).to_predicate(self.tcx), span));
             }
         }
 
@@ -441,13 +521,9 @@ pub(super) fn explicit_predicates_of<'tcx>(
             .iter()
             .copied()
             .filter(|(pred, _)| match pred.kind().skip_binder() {
-                ty::PredicateKind::Clause(ty::Clause::Trait(tr)) => !is_assoc_item_ty(tr.self_ty()),
-                ty::PredicateKind::Clause(ty::Clause::Projection(proj)) => {
-                    !is_assoc_item_ty(proj.projection_ty.self_ty())
-                }
-                ty::PredicateKind::Clause(ty::Clause::TypeOutlives(outlives)) => {
-                    !is_assoc_item_ty(outlives.0)
-                }
+                ty::ClauseKind::Trait(tr) => !is_assoc_item_ty(tr.self_ty()),
+                ty::ClauseKind::Projection(proj) => !is_assoc_item_ty(proj.projection_ty.self_ty()),
+                ty::ClauseKind::TypeOutlives(outlives) => !is_assoc_item_ty(outlives.0),
                 _ => true,
             })
             .collect();
@@ -460,7 +536,7 @@ pub(super) fn explicit_predicates_of<'tcx>(
             }
         }
     } else {
-        if matches!(def_kind, DefKind::AnonConst) && tcx.lazy_normalization() {
+        if matches!(def_kind, DefKind::AnonConst) && tcx.features().generic_const_exprs {
             let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
             let parent_def_id = tcx.hir().get_parent_item(hir_id);
 
@@ -488,9 +564,7 @@ pub(super) fn explicit_predicates_of<'tcx>(
                     .predicates
                     .into_iter()
                     .filter(|(pred, _)| {
-                        if let ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(ct, _)) =
-                            pred.kind().skip_binder()
-                        {
+                        if let ty::ClauseKind::ConstArgHasType(ct, _) = pred.kind().skip_binder() {
                             match ct.kind() {
                                 ty::ConstKind::Param(param_const) => {
                                     let defaulted_param_idx = tcx
@@ -544,19 +618,6 @@ pub(super) fn explicit_predicates_of<'tcx>(
     }
 }
 
-#[derive(Copy, Clone, Debug)]
-pub enum PredicateFilter {
-    /// All predicates may be implied by the trait
-    All,
-
-    /// Only traits that reference `Self: ..` are implied by the trait
-    SelfOnly,
-
-    /// Only traits that reference `Self: ..` and define an associated type
-    /// with the given ident are implied by the trait
-    SelfThatDefines(Ident),
-}
-
 /// Ensures that the super-predicates of the trait with a `DefId`
 /// of `trait_def_id` are converted and stored. This also ensures that
 /// the transitive super-predicates are converted.
@@ -578,11 +639,15 @@ pub(super) fn implied_predicates_of(
     tcx: TyCtxt<'_>,
     trait_def_id: LocalDefId,
 ) -> ty::GenericPredicates<'_> {
-    if tcx.is_trait_alias(trait_def_id.to_def_id()) {
-        implied_predicates_with_filter(tcx, trait_def_id.to_def_id(), PredicateFilter::All)
-    } else {
-        tcx.super_predicates_of(trait_def_id)
-    }
+    implied_predicates_with_filter(
+        tcx,
+        trait_def_id.to_def_id(),
+        if tcx.is_trait_alias(trait_def_id.to_def_id()) {
+            PredicateFilter::All
+        } else {
+            PredicateFilter::SelfAndAssociatedTypeBounds
+        },
+    )
 }
 
 /// Ensures that the super-predicates of the trait with a `DefId`
@@ -615,48 +680,18 @@ pub(super) fn implied_predicates_with_filter(
     let icx = ItemCtxt::new(tcx, trait_def_id);
 
     let self_param_ty = tcx.types.self_param;
-    let (superbounds, where_bounds_that_match) = match filter {
-        PredicateFilter::All => (
-            // Convert the bounds that follow the colon (or equal in trait aliases)
-            icx.astconv().compute_bounds(self_param_ty, bounds, OnlySelfBounds(false)),
-            // Also include all where clause bounds
-            icx.type_parameter_bounds_in_generics(
-                generics,
-                item.owner_id.def_id,
-                self_param_ty,
-                OnlySelfBounds(false),
-                None,
-            ),
-        ),
-        PredicateFilter::SelfOnly => (
-            // Convert the bounds that follow the colon (or equal in trait aliases)
-            icx.astconv().compute_bounds(self_param_ty, bounds, OnlySelfBounds(true)),
-            // Include where clause bounds for `Self`
-            icx.type_parameter_bounds_in_generics(
-                generics,
-                item.owner_id.def_id,
-                self_param_ty,
-                OnlySelfBounds(true),
-                None,
-            ),
-        ),
-        PredicateFilter::SelfThatDefines(assoc_name) => (
-            // Convert the bounds that follow the colon (or equal) that reference the associated name
-            icx.astconv().compute_bounds_that_match_assoc_item(self_param_ty, bounds, assoc_name),
-            // Include where clause bounds for `Self` that reference the associated name
-            icx.type_parameter_bounds_in_generics(
-                generics,
-                item.owner_id.def_id,
-                self_param_ty,
-                OnlySelfBounds(true),
-                Some(assoc_name),
-            ),
-        ),
-    };
+    let superbounds = icx.astconv().compute_bounds(self_param_ty, bounds, filter);
+
+    let where_bounds_that_match = icx.type_parameter_bounds_in_generics(
+        generics,
+        item.owner_id.def_id,
+        self_param_ty,
+        filter,
+    );
 
     // Combine the two lists to form the complete set of superbounds:
     let implied_bounds =
-        &*tcx.arena.alloc_from_iter(superbounds.predicates().chain(where_bounds_that_match));
+        &*tcx.arena.alloc_from_iter(superbounds.clauses().chain(where_bounds_that_match));
     debug!(?implied_bounds);
 
     // Now require that immediate supertraits are converted, which will, in
@@ -665,7 +700,7 @@ pub(super) fn implied_predicates_with_filter(
     if matches!(filter, PredicateFilter::SelfOnly) {
         for &(pred, span) in implied_bounds {
             debug!("superbound: {:?}", pred);
-            if let ty::PredicateKind::Clause(ty::Clause::Trait(bound)) = pred.kind().skip_binder()
+            if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()
                 && bound.polarity == ty::ImplPolarity::Positive
             {
                 tcx.at(span).super_predicates_of(bound.def_id());
@@ -684,6 +719,7 @@ pub(super) fn type_param_predicates(
     (item_def_id, def_id, assoc_name): (LocalDefId, LocalDefId, Ident),
 ) -> ty::GenericPredicates<'_> {
     use rustc_hir::*;
+    use rustc_middle::ty::Ty;
 
     // In the AST, bounds can derive from two places. Either
     // written inline like `<T: Foo>` or in a where-clause like
@@ -693,7 +729,7 @@ pub(super) fn type_param_predicates(
     let param_owner = tcx.hir().ty_param_owner(def_id);
     let generics = tcx.generics_of(param_owner);
     let index = generics.param_def_id_to_index[&def_id.to_def_id()];
-    let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(def_id));
+    let ty = Ty::new_param(tcx, index, tcx.hir().ty_param_name(def_id));
 
     // Don't look for bounds where the type parameter isn't in scope.
     let parent = if item_def_id == param_owner {
@@ -721,7 +757,7 @@ pub(super) fn type_param_predicates(
                 ItemKind::Fn(.., generics, _)
                 | ItemKind::Impl(&hir::Impl { generics, .. })
                 | ItemKind::TyAlias(_, generics)
-                | ItemKind::OpaqueTy(OpaqueTy {
+                | ItemKind::OpaqueTy(&OpaqueTy {
                     generics,
                     origin: hir::OpaqueTyOrigin::TyAlias { .. },
                     ..
@@ -757,12 +793,11 @@ pub(super) fn type_param_predicates(
             ast_generics,
             def_id,
             ty,
-            OnlySelfBounds(true),
-            Some(assoc_name),
+            PredicateFilter::SelfThatDefines(assoc_name),
         )
         .into_iter()
         .filter(|(predicate, _)| match predicate.kind().skip_binder() {
-            ty::PredicateKind::Clause(ty::Clause::Trait(data)) => data.self_ty().is_param(index),
+            ty::ClauseKind::Trait(data) => data.self_ty().is_param(index),
             _ => false,
         }),
     );
@@ -782,9 +817,8 @@ impl<'tcx> ItemCtxt<'tcx> {
         ast_generics: &'tcx hir::Generics<'tcx>,
         param_def_id: LocalDefId,
         ty: Ty<'tcx>,
-        only_self_bounds: OnlySelfBounds,
-        assoc_name: Option<Ident>,
-    ) -> Vec<(ty::Predicate<'tcx>, Span)> {
+        filter: PredicateFilter,
+    ) -> Vec<(ty::Clause<'tcx>, Span)> {
         let mut bounds = Bounds::default();
 
         for predicate in ast_generics.predicates {
@@ -792,9 +826,23 @@ impl<'tcx> ItemCtxt<'tcx> {
                 continue;
             };
 
+            let (only_self_bounds, assoc_name) = match filter {
+                PredicateFilter::All | PredicateFilter::SelfAndAssociatedTypeBounds => {
+                    (OnlySelfBounds(false), None)
+                }
+                PredicateFilter::SelfOnly => (OnlySelfBounds(true), None),
+                PredicateFilter::SelfThatDefines(assoc_name) => {
+                    (OnlySelfBounds(true), Some(assoc_name))
+                }
+            };
+
+            // Subtle: If we're collecting `SelfAndAssociatedTypeBounds`, then we
+            // want to only consider predicates with `Self: ...`, but we don't want
+            // `OnlySelfBounds(true)` since we want to collect the nested associated
+            // type bound as well.
             let bound_ty = if predicate.is_param_bound(param_def_id.to_def_id()) {
                 ty
-            } else if !only_self_bounds.0 {
+            } else if matches!(filter, PredicateFilter::All) {
                 self.to_ty(predicate.bounded_ty)
             } else {
                 continue;
@@ -813,7 +861,7 @@ impl<'tcx> ItemCtxt<'tcx> {
             );
         }
 
-        bounds.predicates().collect()
+        bounds.clauses().collect()
     }
 
     #[instrument(level = "trace", skip(self))]
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 794812a5c..acd0bcd8e 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -22,7 +22,7 @@ use rustc_middle::ty::{self, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_session::lint;
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
-use rustc_span::Span;
+use rustc_span::{Span, DUMMY_SP};
 use std::fmt;
 
 use crate::errors;
@@ -338,7 +338,17 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
 
                 Scope::TraitRefBoundary { .. } => {
                     // We should only see super trait lifetimes if there is a `Binder` above
-                    assert!(supertrait_bound_vars.is_empty());
+                    // though this may happen when we call `poly_trait_ref_binder_info` with
+                    // an (erroneous, #113423) associated return type bound in an impl header.
+                    if !supertrait_bound_vars.is_empty() {
+                        self.tcx.sess.delay_span_bug(
+                            DUMMY_SP,
+                            format!(
+                                "found supertrait lifetimes without a binder to append \
+                                them to: {supertrait_bound_vars:?}"
+                            ),
+                        );
+                    }
                     break (vec![], BinderScopeType::Normal);
                 }
 
@@ -556,7 +566,7 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     });
                 }
             }
-            hir::ItemKind::OpaqueTy(hir::OpaqueTy {
+            hir::ItemKind::OpaqueTy(&hir::OpaqueTy {
                 origin: hir::OpaqueTyOrigin::FnReturn(parent) | hir::OpaqueTyOrigin::AsyncFn(parent),
                 generics,
                 ..
@@ -1344,12 +1354,10 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                 Scope::Binder {
                     where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
                 } => {
-                    let mut err = self.tcx.sess.struct_span_err(
-                        lifetime_ref.ident.span,
-                        "`impl Trait` can only mention lifetimes bound at the fn or impl level",
-                    );
-                    err.span_note(self.tcx.def_span(region_def_id), "lifetime declared here");
-                    err.emit();
+                    self.tcx.sess.emit_err(errors::LateBoundInApit::Lifetime {
+                        span: lifetime_ref.ident.span,
+                        param_span: self.tcx.def_span(region_def_id),
+                    });
                     return;
                 }
                 Scope::Root { .. } => break,
@@ -1379,6 +1387,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
         let mut late_depth = 0;
         let mut scope = self.scope;
         let mut crossed_anon_const = false;
+
         let result = loop {
             match *scope {
                 Scope::Body { s, .. } => {
@@ -1446,6 +1455,50 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             return;
         }
 
+        // We may fail to resolve higher-ranked ty/const vars that are mentioned by APIT.
+        // AST-based resolution does not care for impl-trait desugaring, which are the
+        // responsibility of lowering. This may create a mismatch between the resolution
+        // AST found (`param_def_id`) which points to HRTB, and what HIR allows.
+        // ```
+        // fn foo(x: impl for<T> Trait<Assoc = impl Trait2<T>>) {}
+        // ```
+        //
+        // In such case, walk back the binders to diagnose it properly.
+        let mut scope = self.scope;
+        loop {
+            match *scope {
+                Scope::Binder {
+                    where_bound_origin: Some(hir::PredicateOrigin::ImplTrait), ..
+                } => {
+                    let guar = self.tcx.sess.emit_err(match self.tcx.def_kind(param_def_id) {
+                        DefKind::TyParam => errors::LateBoundInApit::Type {
+                            span: self.tcx.hir().span(hir_id),
+                            param_span: self.tcx.def_span(param_def_id),
+                        },
+                        DefKind::ConstParam => errors::LateBoundInApit::Const {
+                            span: self.tcx.hir().span(hir_id),
+                            param_span: self.tcx.def_span(param_def_id),
+                        },
+                        kind => {
+                            bug!("unexpected def-kind: {}", kind.descr(param_def_id.to_def_id()))
+                        }
+                    });
+                    self.map.defs.insert(hir_id, ResolvedArg::Error(guar));
+                    return;
+                }
+                Scope::Root { .. } => break,
+                Scope::Binder { s, .. }
+                | Scope::Body { s, .. }
+                | Scope::Elision { s, .. }
+                | Scope::ObjectLifetimeDefault { s, .. }
+                | Scope::Supertrait { s, .. }
+                | Scope::TraitRefBoundary { s, .. }
+                | Scope::AnonConstBoundary { s } => {
+                    scope = s;
+                }
+            }
+        }
+
         self.tcx.sess.delay_span_bug(
             self.tcx.hir().span(hir_id),
             format!("could not resolve {param_def_id:?}"),
@@ -1761,7 +1814,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
                 let bound_predicate = pred.kind();
                 match bound_predicate.skip_binder() {
-                    ty::PredicateKind::Clause(ty::Clause::Trait(data)) => {
+                    ty::ClauseKind::Trait(data) => {
                         // The order here needs to match what we would get from `subst_supertrait`
                         let pred_bound_vars = bound_predicate.bound_vars();
                         let mut all_bound_vars = bound_vars.clone();
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index 8e082d3c5..3755342ae 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -16,6 +16,7 @@ mod opaque;
 
 fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
     use hir::*;
+    use rustc_middle::ty::Ty;
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
 
     let Node::AnonConst(_) = tcx.hir().get(hir_id) else { panic!() };
@@ -25,21 +26,15 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
 
     let (generics, arg_idx) = match parent_node {
         // Easy case: arrays repeat expressions.
-        Node::Ty(&Ty { kind: TyKind::Array(_, ref constant), .. })
+        Node::Ty(&hir::Ty { kind: TyKind::Array(_, ref constant), .. })
         | Node::Expr(&Expr { kind: ExprKind::Repeat(_, ref constant), .. })
             if constant.hir_id() == hir_id =>
         {
             return tcx.types.usize
         }
-        Node::Ty(&Ty { kind: TyKind::Typeof(ref e), .. }) if e.hir_id == hir_id => {
+        Node::Ty(&hir::Ty { kind: TyKind::Typeof(ref e), .. }) if e.hir_id == hir_id => {
             return tcx.typeck(def_id).node_type(e.hir_id)
         }
-        Node::Expr(&Expr { kind: ExprKind::ConstBlock(ref anon_const), .. })
-            if anon_const.hir_id == hir_id =>
-        {
-            let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
-            return substs.as_inline_const().ty()
-        }
         Node::Expr(&Expr { kind: ExprKind::InlineAsm(asm), .. })
         | Node::Item(&Item { kind: ItemKind::GlobalAsm(asm), .. })
             if asm.operands.iter().any(|(op, _op_sp)| match op {
@@ -73,7 +68,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             ) =>
         {
             let Some(trait_def_id) = trait_ref.trait_def_id() else {
-                return tcx.ty_error_with_message(tcx.def_span(def_id), "Could not find trait");
+                return Ty::new_error_with_message(tcx,tcx.def_span(def_id), "Could not find trait");
             };
             let assoc_items = tcx.associated_items(trait_def_id);
             let assoc_item = assoc_items.find_by_name_and_kind(
@@ -85,7 +80,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
                     .expect("const parameter types cannot be generic")
             } else {
                 // FIXME(associated_const_equality): add a useful error message here.
-                tcx.ty_error_with_message(tcx.def_span(def_id), "Could not find associated const on trait")
+                Ty::new_error_with_message(tcx,tcx.def_span(def_id), "Could not find associated const on trait")
             }
         }
 
@@ -105,7 +100,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
         // arm would handle this.
         //
         // I believe this match arm is only needed for GAT but I am not 100% sure - BoxyUwU
-        Node::Ty(hir_ty @ Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => {
+        Node::Ty(hir_ty @ hir::Ty { kind: TyKind::Path(QPath::TypeRelative(_, segment)), .. }) => {
             // Find the Item containing the associated type so we can create an ItemCtxt.
             // Using the ItemCtxt convert the HIR for the unresolved assoc type into a
             // ty which is a fully resolved projection.
@@ -143,7 +138,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
                 (generics, arg_index)
             } else {
                 // I dont think it's possible to reach this but I'm not 100% sure - BoxyUwU
-                return tcx.ty_error_with_message(
+                return Ty::new_error_with_message(tcx,
                     tcx.def_span(def_id),
                     "unexpected non-GAT usage of an anon const",
                 );
@@ -160,7 +155,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             // As there is no relevant param for `def_id`, we simply return
             // `None` here.
             let Some(type_dependent_def) = tables.type_dependent_def_id(parent_node_id) else {
-                return tcx.ty_error_with_message(
+                return Ty::new_error_with_message(tcx,
                     tcx.def_span(def_id),
                     format!("unable to find type-dependent def for {:?}", parent_node_id),
                 );
@@ -180,12 +175,12 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             (tcx.generics_of(type_dependent_def), idx)
         }
 
-        Node::Ty(&Ty { kind: TyKind::Path(_), .. })
+        Node::Ty(&hir::Ty { kind: TyKind::Path(_), .. })
         | Node::Expr(&Expr { kind: ExprKind::Path(_) | ExprKind::Struct(..), .. })
         | Node::TraitRef(..)
         | Node::Pat(_) => {
             let path = match parent_node {
-                Node::Ty(&Ty { kind: TyKind::Path(QPath::Resolved(_, path)), .. })
+                Node::Ty(&hir::Ty { kind: TyKind::Path(QPath::Resolved(_, path)), .. })
                 | Node::TraitRef(&TraitRef { path, .. }) => &*path,
                 Node::Expr(&Expr {
                     kind:
@@ -201,14 +196,14 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
                     if let Some(path) = get_path_containing_arg_in_pat(pat, hir_id) {
                         path
                     } else {
-                        return tcx.ty_error_with_message(
+                        return Ty::new_error_with_message(tcx,
                             tcx.def_span(def_id),
                             format!("unable to find const parent for {} in pat {:?}", hir_id, pat),
                         );
                     }
                 }
                 _ => {
-                    return tcx.ty_error_with_message(
+                    return Ty::new_error_with_message(tcx,
                         tcx.def_span(def_id),
                         format!("unexpected const parent path {:?}", parent_node),
                     );
@@ -230,7 +225,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
                     .position(|ct| ct.hir_id == hir_id)
                     .map(|idx| (idx, seg)))
             }) else {
-                return tcx.ty_error_with_message(
+                return Ty::new_error_with_message(tcx,
                     tcx.def_span(def_id),
                     "no arg matching AnonConst in path",
                 );
@@ -239,7 +234,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             let generics = match tcx.res_generics_def_id(segment.res) {
                 Some(def_id) => tcx.generics_of(def_id),
                 None => {
-                    return tcx.ty_error_with_message(
+                    return Ty::new_error_with_message(tcx,
                         tcx.def_span(def_id),
                         format!("unexpected anon const res {:?} in path: {:?}", segment.res, path),
                     );
@@ -249,7 +244,7 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
             (generics, arg_index)
         }
 
-        _ => return tcx.ty_error_with_message(
+        _ => return Ty::new_error_with_message(tcx,
             tcx.def_span(def_id),
             format!("unexpected const parent in type_of(): {parent_node:?}"),
         ),
@@ -275,7 +270,8 @@ fn anon_const_type_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Ty<'tcx> {
     {
         tcx.type_of(param_def_id).no_bound_vars().expect("const parameter types cannot be generic")
     } else {
-        return tcx.ty_error_with_message(
+        return Ty::new_error_with_message(
+            tcx,
             tcx.def_span(def_id),
             format!("const generic parameter not found in {generics:?} at position {arg_idx:?}"),
         );
@@ -311,6 +307,9 @@ fn get_path_containing_arg_in_pat<'hir>(
 }
 
 pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty<'_>> {
+    use rustc_hir::*;
+    use rustc_middle::ty::Ty;
+
     // If we are computing `type_of` the synthesized associated type for an RPITIT in the impl
     // side, use `collect_return_position_impl_trait_in_trait_tys` to infer the value of the
     // associated type in the impl.
@@ -323,7 +322,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                 return map[&assoc_item.trait_item_def_id.unwrap()];
             }
             Err(_) => {
-                return ty::EarlyBinder(tcx.ty_error_with_message(
+                return ty::EarlyBinder::bind(Ty::new_error_with_message(
+                    tcx,
                     DUMMY_SP,
                     "Could not collect return position impl trait in trait tys",
                 ));
@@ -331,8 +331,6 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
         }
     }
 
-    use rustc_hir::*;
-
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
 
     let icx = ItemCtxt::new(tcx, def_id);
@@ -341,13 +339,18 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
         Node::TraitItem(item) => match item.kind {
             TraitItemKind::Fn(..) => {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                tcx.mk_fn_def(def_id.to_def_id(), substs)
+                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
             }
             TraitItemKind::Const(ty, body_id) => body_id
                 .and_then(|body_id| {
                     is_suggestable_infer_ty(ty).then(|| {
                         infer_placeholder_type(
-                            tcx, def_id, body_id, ty.span, item.ident, "constant",
+                            tcx,
+                            def_id,
+                            body_id,
+                            ty.span,
+                            item.ident,
+                            "associated constant",
                         )
                     })
                 })
@@ -361,11 +364,18 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
         Node::ImplItem(item) => match item.kind {
             ImplItemKind::Fn(..) => {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                tcx.mk_fn_def(def_id.to_def_id(), substs)
+                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
             }
             ImplItemKind::Const(ty, body_id) => {
                 if is_suggestable_infer_ty(ty) {
-                    infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident, "constant")
+                    infer_placeholder_type(
+                        tcx,
+                        def_id,
+                        body_id,
+                        ty.span,
+                        item.ident,
+                        "associated constant",
+                    )
                 } else {
                     icx.to_ty(ty)
                 }
@@ -411,31 +421,31 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                             span: spans.into(),
                             note: (),
                         });
-                        tcx.ty_error(guar)
+                        Ty::new_error(tcx, guar)
                     }
                     _ => icx.to_ty(*self_ty),
                 },
                 ItemKind::Fn(..) => {
                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                    tcx.mk_fn_def(def_id.to_def_id(), substs)
+                    Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
                 }
                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
                     let def = tcx.adt_def(def_id);
                     let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                    tcx.mk_adt(def, substs)
+                    Ty::new_adt(tcx, def, substs)
                 }
                 ItemKind::OpaqueTy(OpaqueTy {
                     origin: hir::OpaqueTyOrigin::TyAlias { .. },
                     ..
                 }) => opaque::find_opaque_ty_constraints_for_tait(tcx, def_id),
                 // Opaque types desugared from `impl Trait`.
-                ItemKind::OpaqueTy(OpaqueTy {
+                ItemKind::OpaqueTy(&OpaqueTy {
                     origin:
                         hir::OpaqueTyOrigin::FnReturn(owner) | hir::OpaqueTyOrigin::AsyncFn(owner),
                     in_trait,
                     ..
                 }) => {
-                    if in_trait && !tcx.impl_defaultness(owner).has_value() {
+                    if in_trait && !tcx.defaultness(owner).has_value() {
                         span_bug!(
                             tcx.def_span(def_id),
                             "tried to get type of this RPITIT with no definition"
@@ -463,10 +473,10 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
         Node::ForeignItem(foreign_item) => match foreign_item.kind {
             ForeignItemKind::Fn(..) => {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                tcx.mk_fn_def(def_id.to_def_id(), substs)
+                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
             }
             ForeignItemKind::Static(t, _) => icx.to_ty(t),
-            ForeignItemKind::Type => tcx.mk_foreign(def_id.to_def_id()),
+            ForeignItemKind::Type => Ty::new_foreign(tcx, def_id.to_def_id()),
         },
 
         Node::Ctor(def) | Node::Variant(Variant { data: def, .. }) => match def {
@@ -475,7 +485,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
             }
             VariantData::Tuple(..) => {
                 let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                tcx.mk_fn_def(def_id.to_def_id(), substs)
+                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
             }
         },
 
@@ -487,6 +497,11 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
 
         Node::AnonConst(_) => anon_const_type_of(tcx, def_id),
 
+        Node::ConstBlock(_) => {
+            let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
+            substs.as_inline_const().ty()
+        }
+
         Node::GenericParam(param) => match &param.kind {
             GenericParamKind::Type { default: Some(ty), .. }
             | GenericParamKind::Const { ty, .. } => icx.to_ty(ty),
@@ -497,7 +512,7 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
             bug!("unexpected sort of node in type_of(): {:?}", x);
         }
     };
-    ty::EarlyBinder(output)
+    ty::EarlyBinder::bind(output)
 }
 
 fn infer_placeholder_type<'a>(
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
index f7c5b4467..957a6bb34 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of/opaque.rs
@@ -1,3 +1,4 @@
+use rustc_errors::StashKey;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{self as hir, Expr, ImplItem, Item, Node, TraitItem};
@@ -5,7 +6,7 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::DUMMY_SP;
 
-use crate::errors::UnconstrainedOpaqueType;
+use crate::errors::{TaitForwardCompat, UnconstrainedOpaqueType};
 
 /// Checks "defining uses" of opaque `impl Trait` types to ensure that they meet the restrictions
 /// laid for "higher-order pattern unification".
@@ -59,7 +60,20 @@ pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: Local
         }
     }
 
-    let Some(hidden) = locator.found else {
+    if let Some(hidden) = locator.found {
+        // Only check against typeck if we didn't already error
+        if !hidden.ty.references_error() {
+            for concrete_type in locator.typeck_types {
+                if concrete_type.ty != tcx.erase_regions(hidden.ty)
+                    && !(concrete_type, hidden).references_error()
+                {
+                    hidden.report_mismatch(&concrete_type, def_id, tcx).emit();
+                }
+            }
+        }
+
+        hidden.ty
+    } else {
         let reported = tcx.sess.emit_err(UnconstrainedOpaqueType {
             span: tcx.def_span(def_id),
             name: tcx.item_name(tcx.local_parent(def_id).to_def_id()),
@@ -70,21 +84,8 @@ pub(super) fn find_opaque_ty_constraints_for_tait(tcx: TyCtxt<'_>, def_id: Local
                 _ => "item",
             },
         });
-        return tcx.ty_error(reported);
-    };
-
-    // Only check against typeck if we didn't already error
-    if !hidden.ty.references_error() {
-        for concrete_type in locator.typeck_types {
-            if concrete_type.ty != tcx.erase_regions(hidden.ty)
-                && !(concrete_type, hidden).references_error()
-            {
-                hidden.report_mismatch(&concrete_type, def_id, tcx).emit();
-            }
-        }
+        Ty::new_error(tcx, reported)
     }
-
-    hidden.ty
 }
 
 struct TaitConstraintLocator<'tcx> {
@@ -127,16 +128,41 @@ impl TaitConstraintLocator<'_> {
         // ```
         let tables = self.tcx.typeck(item_def_id);
         if let Some(guar) = tables.tainted_by_errors {
-            self.found = Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: self.tcx.ty_error(guar) });
+            self.found =
+                Some(ty::OpaqueHiddenType { span: DUMMY_SP, ty: Ty::new_error(self.tcx, guar) });
             return;
         }
-        let Some(&typeck_hidden_ty) = tables.concrete_opaque_types.get(&self.def_id) else {
+
+        let mut constrained = false;
+        for (&opaque_type_key, &hidden_type) in &tables.concrete_opaque_types {
+            if opaque_type_key.def_id != self.def_id {
+                continue;
+            }
+            constrained = true;
+            if !self.tcx.opaque_types_defined_by(item_def_id).contains(&self.def_id) {
+                self.tcx.sess.emit_err(TaitForwardCompat {
+                    span: hidden_type.span,
+                    item_span: self
+                        .tcx
+                        .def_ident_span(item_def_id)
+                        .unwrap_or_else(|| self.tcx.def_span(item_def_id)),
+                });
+            }
+            let concrete_type =
+                self.tcx.erase_regions(hidden_type.remap_generic_params_to_declaration_params(
+                    opaque_type_key,
+                    self.tcx,
+                    true,
+                ));
+            if self.typeck_types.iter().all(|prev| prev.ty != concrete_type.ty) {
+                self.typeck_types.push(concrete_type);
+            }
+        }
+
+        if !constrained {
             debug!("no constraints in typeck results");
             return;
         };
-        if self.typeck_types.iter().all(|prev| prev.ty != typeck_hidden_ty.ty) {
-            self.typeck_types.push(typeck_hidden_ty);
-        }
 
         // Use borrowck to get the type with unerased regions.
         let concrete_opaque_types = &self.tcx.mir_borrowck(item_def_id).concrete_opaque_types;
@@ -146,7 +172,7 @@ impl TaitConstraintLocator<'_> {
             if let Some(prev) = &mut self.found {
                 if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() {
                     let guar = prev.report_mismatch(&concrete_type, self.def_id, self.tcx).emit();
-                    prev.ty = self.tcx.ty_error(guar);
+                    prev.ty = Ty::new_error(self.tcx, guar);
                 }
             } else {
                 self.found = Some(concrete_type);
@@ -190,17 +216,45 @@ impl<'tcx> intravisit::Visitor<'tcx> for TaitConstraintLocator<'tcx> {
     }
 }
 
-pub(super) fn find_opaque_ty_constraints_for_rpit(
-    tcx: TyCtxt<'_>,
+pub(super) fn find_opaque_ty_constraints_for_rpit<'tcx>(
+    tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
     owner_def_id: LocalDefId,
 ) -> Ty<'_> {
-    let concrete = tcx.mir_borrowck(owner_def_id).concrete_opaque_types.get(&def_id).copied();
+    let tables = tcx.typeck(owner_def_id);
 
-    if let Some(concrete) = concrete {
+    // Check that all of the opaques we inferred during HIR are compatible.
+    // FIXME: We explicitly don't check that the types inferred during HIR
+    // typeck are compatible with the one that we infer during borrowck,
+    // because that one actually sometimes has consts evaluated eagerly so
+    // using strict type equality will fail.
+    let mut hir_opaque_ty: Option<ty::OpaqueHiddenType<'tcx>> = None;
+    if tables.tainted_by_errors.is_none() {
+        for (&opaque_type_key, &hidden_type) in &tables.concrete_opaque_types {
+            if opaque_type_key.def_id != def_id {
+                continue;
+            }
+            let concrete_type = tcx.erase_regions(
+                hidden_type.remap_generic_params_to_declaration_params(opaque_type_key, tcx, true),
+            );
+            if let Some(prev) = &mut hir_opaque_ty {
+                if concrete_type.ty != prev.ty && !(concrete_type, prev.ty).references_error() {
+                    prev.report_mismatch(&concrete_type, def_id, tcx).stash(
+                        tcx.def_span(opaque_type_key.def_id),
+                        StashKey::OpaqueHiddenTypeMismatch,
+                    );
+                }
+            } else {
+                hir_opaque_ty = Some(concrete_type);
+            }
+        }
+    }
+
+    let mir_opaque_ty = tcx.mir_borrowck(owner_def_id).concrete_opaque_types.get(&def_id).copied();
+    if let Some(mir_opaque_ty) = mir_opaque_ty {
         let scope = tcx.hir().local_def_id_to_hir_id(owner_def_id);
         debug!(?scope);
-        let mut locator = RpitConstraintChecker { def_id, tcx, found: concrete };
+        let mut locator = RpitConstraintChecker { def_id, tcx, found: mir_opaque_ty };
 
         match tcx.hir().get(scope) {
             Node::Item(it) => intravisit::walk_item(&mut locator, it),
@@ -208,27 +262,28 @@ pub(super) fn find_opaque_ty_constraints_for_rpit(
             Node::TraitItem(it) => intravisit::walk_trait_item(&mut locator, it),
             other => bug!("{:?} is not a valid scope for an opaque type item", other),
         }
-    }
 
-    concrete.map(|concrete| concrete.ty).unwrap_or_else(|| {
-        let table = tcx.typeck(owner_def_id);
-        if let Some(guar) = table.tainted_by_errors {
-            // Some error in the
-            // owner fn prevented us from populating
+        mir_opaque_ty.ty
+    } else {
+        if let Some(guar) = tables.tainted_by_errors {
+            // Some error in the owner fn prevented us from populating
             // the `concrete_opaque_types` table.
-            tcx.ty_error(guar)
+            Ty::new_error(tcx, guar)
         } else {
-            table.concrete_opaque_types.get(&def_id).map(|ty| ty.ty).unwrap_or_else(|| {
+            // Fall back to the RPIT we inferred during HIR typeck
+            if let Some(hir_opaque_ty) = hir_opaque_ty {
+                hir_opaque_ty.ty
+            } else {
                 // We failed to resolve the opaque type or it
                 // resolves to itself. We interpret this as the
                 // no values of the hidden type ever being constructed,
                 // so we can just make the hidden type be `!`.
                 // For backwards compatibility reasons, we fall back to
                 // `()` until we the diverging default is changed.
-                tcx.mk_diverging_default()
-            })
+                Ty::new_diverging_default(tcx)
+            }
         }
-    })
+    }
 }
 
 struct RpitConstraintChecker<'tcx> {