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-rw-r--r--compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs26
-rw-r--r--compiler/rustc_trait_selection/src/traits/fulfill.rs7
-rw-r--r--compiler/rustc_trait_selection/src/traits/misc.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs69
-rw-r--r--compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs58
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs62
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/confirmation.rs92
-rw-r--r--compiler/rustc_trait_selection/src/traits/select/mod.rs3
-rw-r--r--compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs7
-rw-r--r--compiler/rustc_trait_selection/src/traits/util.rs4
-rw-r--r--compiler/rustc_trait_selection/src/traits/vtable.rs2
-rw-r--r--compiler/rustc_trait_selection/src/traits/wf.rs72
12 files changed, 323 insertions, 81 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
index 617bc87a9d2..d4502be6ccf 100644
--- a/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
+++ b/compiler/rustc_trait_selection/src/traits/dyn_compatibility.rs
@@ -128,8 +128,7 @@ fn sized_trait_bound_spans<'tcx>(
 }
 
 fn get_sized_bounds(tcx: TyCtxt<'_>, trait_def_id: DefId) -> SmallVec<[Span; 1]> {
-    tcx.hir()
-        .get_if_local(trait_def_id)
+    tcx.hir_get_if_local(trait_def_id)
         .and_then(|node| match node {
             hir::Node::Item(hir::Item {
                 kind: hir::ItemKind::Trait(.., generics, bounds, _),
@@ -187,7 +186,10 @@ fn predicates_reference_self(
 fn bounds_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> SmallVec<[Span; 1]> {
     tcx.associated_items(trait_def_id)
         .in_definition_order()
+        // We're only looking at associated type bounds
         .filter(|item| item.kind == ty::AssocKind::Type)
+        // Ignore GATs with `Self: Sized`
+        .filter(|item| !tcx.generics_require_sized_self(item.def_id))
         .flat_map(|item| tcx.explicit_item_bounds(item.def_id).iter_identity_copied())
         .filter_map(|(clause, sp)| {
             // Item bounds *can* have self projections, since they never get
@@ -301,7 +303,7 @@ pub fn dyn_compatibility_violations_for_assoc_item(
         ty::AssocKind::Fn => virtual_call_violations_for_method(tcx, trait_def_id, item)
             .into_iter()
             .map(|v| {
-                let node = tcx.hir().get_if_local(item.def_id);
+                let node = tcx.hir_get_if_local(item.def_id);
                 // Get an accurate span depending on the violation.
                 let span = match (&v, node) {
                     (MethodViolationCode::ReferencesSelfInput(Some(span)), _) => *span,
@@ -346,7 +348,7 @@ fn virtual_call_violations_for_method<'tcx>(
             generics,
             kind: hir::TraitItemKind::Fn(sig, _),
             ..
-        })) = tcx.hir().get_if_local(method.def_id).as_ref()
+        })) = tcx.hir_get_if_local(method.def_id).as_ref()
         {
             let sm = tcx.sess.source_map();
             Some((
@@ -380,7 +382,7 @@ fn virtual_call_violations_for_method<'tcx>(
             let span = if let Some(hir::Node::TraitItem(hir::TraitItem {
                 kind: hir::TraitItemKind::Fn(sig, _),
                 ..
-            })) = tcx.hir().get_if_local(method.def_id).as_ref()
+            })) = tcx.hir_get_if_local(method.def_id).as_ref()
             {
                 Some(sig.decl.inputs[i].span)
             } else {
@@ -418,7 +420,7 @@ fn virtual_call_violations_for_method<'tcx>(
             let span = if let Some(hir::Node::TraitItem(hir::TraitItem {
                 kind: hir::TraitItemKind::Fn(sig, _),
                 ..
-            })) = tcx.hir().get_if_local(method.def_id).as_ref()
+            })) = tcx.hir_get_if_local(method.def_id).as_ref()
             {
                 Some(sig.decl.inputs[0].span)
             } else {
@@ -536,10 +538,10 @@ fn receiver_for_self_ty<'tcx>(
 /// a pointer.
 ///
 /// In practice, we cannot use `dyn Trait` explicitly in the obligation because it would result in
-/// a new check that `Trait` is dyn-compatible, creating a cycle (until dyn_compatible_for_dispatch
-/// is stabilized, see tracking issue <https://github.com/rust-lang/rust/issues/43561>).
-/// Instead, we fudge a little by introducing a new type parameter `U` such that
+/// a new check that `Trait` is dyn-compatible, creating a cycle.
+/// Instead, we emulate a placeholder by introducing a new type parameter `U` such that
 /// `Self: Unsize<U>` and `U: Trait + ?Sized`, and use `U` in place of `dyn Trait`.
+///
 /// Written as a chalk-style query:
 /// ```ignore (not-rust)
 /// forall (U: Trait + ?Sized) {
@@ -570,8 +572,6 @@ fn receiver_is_dispatchable<'tcx>(
 
     // the type `U` in the query
     // use a bogus type parameter to mimic a forall(U) query using u32::MAX for now.
-    // FIXME(mikeyhew) this is a total hack. Once dyn_compatible_for_dispatch is stabilized, we can
-    // replace this with `dyn Trait`
     let unsized_self_ty: Ty<'tcx> =
         Ty::new_param(tcx, u32::MAX, rustc_span::sym::RustaceansAreAwesome);
 
@@ -696,11 +696,11 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IllegalSelfTypeVisitor<'tcx> {
                     ControlFlow::Continue(())
                 }
             }
-            ty::Alias(ty::Projection, ref data) if self.tcx.is_impl_trait_in_trait(data.def_id) => {
+            ty::Alias(ty::Projection, data) if self.tcx.is_impl_trait_in_trait(data.def_id) => {
                 // We'll deny these later in their own pass
                 ControlFlow::Continue(())
             }
-            ty::Alias(ty::Projection, ref data) => {
+            ty::Alias(ty::Projection, data) => {
                 match self.allow_self_projections {
                     AllowSelfProjections::Yes => {
                         // This is a projected type `<Foo as SomeTrait>::X`.
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index f2d2dd2f3ce..e39f8e673db 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -1,6 +1,5 @@
 use std::marker::PhantomData;
 
-use rustc_data_structures::captures::Captures;
 use rustc_data_structures::obligation_forest::{
     Error, ForestObligation, ObligationForest, ObligationProcessor, Outcome, ProcessResult,
 };
@@ -900,10 +899,10 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
 }
 
 /// Returns the set of inference variables contained in `args`.
-fn args_infer_vars<'a, 'tcx>(
-    selcx: &SelectionContext<'a, 'tcx>,
+fn args_infer_vars<'tcx>(
+    selcx: &SelectionContext<'_, 'tcx>,
     args: ty::Binder<'tcx, GenericArgsRef<'tcx>>,
-) -> impl Iterator<Item = TyOrConstInferVar> + Captures<'tcx> {
+) -> impl Iterator<Item = TyOrConstInferVar> {
     selcx
         .infcx
         .resolve_vars_if_possible(args)
diff --git a/compiler/rustc_trait_selection/src/traits/misc.rs b/compiler/rustc_trait_selection/src/traits/misc.rs
index 79e178150de..a4b6f330b9d 100644
--- a/compiler/rustc_trait_selection/src/traits/misc.rs
+++ b/compiler/rustc_trait_selection/src/traits/misc.rs
@@ -208,7 +208,7 @@ pub fn all_fields_implement_trait<'tcx>(
             }
 
             let field_span = tcx.def_span(field.did);
-            let field_ty_span = match tcx.hir().get_if_local(field.did) {
+            let field_ty_span = match tcx.hir_get_if_local(field.did) {
                 Some(hir::Node::Field(field_def)) => field_def.ty.span,
                 _ => field_span,
             };
diff --git a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
index 92098e20448..f04a5feba30 100644
--- a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
@@ -2,12 +2,13 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_infer::traits::query::type_op::DropckOutlives;
 use rustc_middle::traits::query::{DropckConstraint, DropckOutlivesResult};
 use rustc_middle::ty::{self, EarlyBinder, ParamEnvAnd, Ty, TyCtxt};
-use rustc_span::{DUMMY_SP, Span};
+use rustc_span::Span;
 use tracing::{debug, instrument};
 
+use crate::solve::NextSolverError;
 use crate::traits::query::NoSolution;
 use crate::traits::query::normalize::QueryNormalizeExt;
-use crate::traits::{Normalized, ObligationCause, ObligationCtxt};
+use crate::traits::{FromSolverError, Normalized, ObligationCause, ObligationCtxt};
 
 /// This returns true if the type `ty` is "trivial" for
 /// dropck-outlives -- that is, if it doesn't require any types to
@@ -93,6 +94,20 @@ pub fn compute_dropck_outlives_inner<'tcx>(
     goal: ParamEnvAnd<'tcx, DropckOutlives<'tcx>>,
     span: Span,
 ) -> Result<DropckOutlivesResult<'tcx>, NoSolution> {
+    match compute_dropck_outlives_with_errors(ocx, goal, span) {
+        Ok(r) => Ok(r),
+        Err(_) => Err(NoSolution),
+    }
+}
+
+pub fn compute_dropck_outlives_with_errors<'tcx, E>(
+    ocx: &ObligationCtxt<'_, 'tcx, E>,
+    goal: ParamEnvAnd<'tcx, DropckOutlives<'tcx>>,
+    span: Span,
+) -> Result<DropckOutlivesResult<'tcx>, Vec<E>>
+where
+    E: FromSolverError<'tcx, NextSolverError<'tcx>>,
+{
     let tcx = ocx.infcx.tcx;
     let ParamEnvAnd { param_env, value: DropckOutlives { dropped_ty } } = goal;
 
@@ -149,11 +164,11 @@ pub fn compute_dropck_outlives_inner<'tcx>(
         dtorck_constraint_for_ty_inner(
             tcx,
             ocx.infcx.typing_env(param_env),
-            DUMMY_SP,
+            span,
             depth,
             ty,
             &mut constraints,
-        )?;
+        );
 
         // "outlives" represent types/regions that may be touched
         // by a destructor.
@@ -173,11 +188,20 @@ pub fn compute_dropck_outlives_inner<'tcx>(
         // do not themselves define a destructor", more or less. We have
         // to push them onto the stack to be expanded.
         for ty in constraints.dtorck_types.drain(..) {
-            let Normalized { value: ty, obligations } =
-                ocx.infcx.at(&cause, param_env).query_normalize(ty)?;
-            ocx.register_obligations(obligations);
+            let ty = if let Ok(Normalized { value: ty, obligations }) =
+                ocx.infcx.at(&cause, param_env).query_normalize(ty)
+            {
+                ocx.register_obligations(obligations);
+
+                debug!("dropck_outlives: ty from dtorck_types = {:?}", ty);
+                ty
+            } else {
+                ocx.deeply_normalize(&cause, param_env, ty)?;
 
-            debug!("dropck_outlives: ty from dtorck_types = {:?}", ty);
+                let errors = ocx.select_where_possible();
+                debug!("normalize errors: {ty} ~> {errors:#?}");
+                return Err(errors);
+            };
 
             match ty.kind() {
                 // All parameters live for the duration of the
@@ -213,14 +237,14 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
     depth: usize,
     ty: Ty<'tcx>,
     constraints: &mut DropckConstraint<'tcx>,
-) -> Result<(), NoSolution> {
+) {
     if !tcx.recursion_limit().value_within_limit(depth) {
         constraints.overflows.push(ty);
-        return Ok(());
+        return;
     }
 
     if trivial_dropck_outlives(tcx, ty) {
-        return Ok(());
+        return;
     }
 
     match ty.kind() {
@@ -244,22 +268,20 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             // single-element containers, behave like their element
             rustc_data_structures::stack::ensure_sufficient_stack(|| {
                 dtorck_constraint_for_ty_inner(tcx, typing_env, span, depth + 1, *ety, constraints)
-            })?;
+            });
         }
 
         ty::Tuple(tys) => rustc_data_structures::stack::ensure_sufficient_stack(|| {
             for ty in tys.iter() {
-                dtorck_constraint_for_ty_inner(tcx, typing_env, span, depth + 1, ty, constraints)?;
+                dtorck_constraint_for_ty_inner(tcx, typing_env, span, depth + 1, ty, constraints);
             }
-            Ok::<_, NoSolution>(())
-        })?,
+        }),
 
         ty::Closure(_, args) => rustc_data_structures::stack::ensure_sufficient_stack(|| {
             for ty in args.as_closure().upvar_tys() {
-                dtorck_constraint_for_ty_inner(tcx, typing_env, span, depth + 1, ty, constraints)?;
+                dtorck_constraint_for_ty_inner(tcx, typing_env, span, depth + 1, ty, constraints);
             }
-            Ok::<_, NoSolution>(())
-        })?,
+        }),
 
         ty::CoroutineClosure(_, args) => {
             rustc_data_structures::stack::ensure_sufficient_stack(|| {
@@ -271,10 +293,9 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
                         depth + 1,
                         ty,
                         constraints,
-                    )?;
+                    );
                 }
-                Ok::<_, NoSolution>(())
-            })?
+            })
         }
 
         ty::Coroutine(_, args) => {
@@ -313,7 +334,7 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
 
         ty::Adt(def, args) => {
             let DropckConstraint { dtorck_types, outlives, overflows } =
-                tcx.at(span).adt_dtorck_constraint(def.did())?;
+                tcx.at(span).adt_dtorck_constraint(def.did());
             // FIXME: we can try to recursively `dtorck_constraint_on_ty`
             // there, but that needs some way to handle cycles.
             constraints
@@ -346,9 +367,7 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
         ty::Placeholder(..) | ty::Bound(..) | ty::Infer(..) | ty::Error(_) => {
             // By the time this code runs, all type variables ought to
             // be fully resolved.
-            return Err(NoSolution);
+            tcx.dcx().span_delayed_bug(span, format!("Unresolved type in dropck: {:?}.", ty));
         }
     }
-
-    Ok(())
 }
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
index e8c2528aa6e..2f6bbd7f4cf 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/normalize.rs
@@ -2,7 +2,7 @@ use std::fmt;
 
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::NoSolution;
-pub use rustc_middle::traits::query::type_op::Normalize;
+pub use rustc_middle::traits::query::type_op::{DeeplyNormalize, Normalize};
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::{self, Lift, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::Span;
@@ -28,12 +28,53 @@ where
     }
 
     fn perform_locally_with_next_solver(
+        _ocx: &ObligationCtxt<'_, 'tcx>,
+        key: ParamEnvAnd<'tcx, Self>,
+        _span: Span,
+    ) -> Result<Self::QueryResponse, NoSolution> {
+        Ok(key.value.value)
+    }
+}
+
+impl<'tcx, T> super::QueryTypeOp<'tcx> for DeeplyNormalize<T>
+where
+    T: Normalizable<'tcx> + 'tcx,
+{
+    type QueryResponse = T;
+
+    fn try_fast_path(_tcx: TyCtxt<'tcx>, key: &ParamEnvAnd<'tcx, Self>) -> Option<T> {
+        if !key.value.value.has_aliases() { Some(key.value.value) } else { None }
+    }
+
+    fn perform_query(
+        tcx: TyCtxt<'tcx>,
+        canonicalized: CanonicalQueryInput<'tcx, ParamEnvAnd<'tcx, Self>>,
+    ) -> Result<CanonicalQueryResponse<'tcx, Self::QueryResponse>, NoSolution> {
+        T::type_op_method(
+            tcx,
+            CanonicalQueryInput {
+                typing_mode: canonicalized.typing_mode,
+                canonical: canonicalized.canonical.unchecked_map(
+                    |ty::ParamEnvAnd { param_env, value }| ty::ParamEnvAnd {
+                        param_env,
+                        value: Normalize { value: value.value },
+                    },
+                ),
+            },
+        )
+    }
+
+    fn perform_locally_with_next_solver(
         ocx: &ObligationCtxt<'_, 'tcx>,
         key: ParamEnvAnd<'tcx, Self>,
         span: Span,
     ) -> Result<Self::QueryResponse, NoSolution> {
-        // FIXME(-Znext-solver): shouldn't be using old normalizer
-        Ok(ocx.normalize(&ObligationCause::dummy_with_span(span), key.param_env, key.value.value))
+        ocx.deeply_normalize(
+            &ObligationCause::dummy_with_span(span),
+            key.param_env,
+            key.value.value,
+        )
+        .map_err(|_| NoSolution)
     }
 }
 
@@ -81,3 +122,14 @@ impl<'tcx> Normalizable<'tcx> for ty::FnSig<'tcx> {
         tcx.type_op_normalize_fn_sig(canonicalized)
     }
 }
+
+/// This impl is not needed, since we never normalize type outlives predicates
+/// in the old solver, but is required by trait bounds to be happy.
+impl<'tcx> Normalizable<'tcx> for ty::PolyTypeOutlivesPredicate<'tcx> {
+    fn type_op_method(
+        _tcx: TyCtxt<'tcx>,
+        _canonicalized: CanonicalQueryInput<'tcx, ParamEnvAnd<'tcx, Normalize<Self>>>,
+    ) -> Result<CanonicalQueryResponse<'tcx, Self>, NoSolution> {
+        unreachable!("we never normalize PolyTypeOutlivesPredicate")
+    }
+}
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index e495bdbf782..11b6b826efe 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -102,6 +102,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 self.assemble_candidate_for_tuple(obligation, &mut candidates);
             } else if tcx.is_lang_item(def_id, LangItem::FnPtrTrait) {
                 self.assemble_candidates_for_fn_ptr_trait(obligation, &mut candidates);
+            } else if tcx.is_lang_item(def_id, LangItem::BikeshedGuaranteedNoDrop) {
+                self.assemble_candidates_for_bikeshed_guaranteed_no_drop_trait(
+                    obligation,
+                    &mut candidates,
+                );
             } else {
                 if tcx.is_lang_item(def_id, LangItem::Clone) {
                     // Same builtin conditions as `Copy`, i.e., every type which has builtin support
@@ -854,13 +859,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                         }
 
                         if let Some(principal) = data.principal() {
-                            if !self.infcx.tcx.features().dyn_compatible_for_dispatch() {
-                                principal.with_self_ty(self.tcx(), self_ty)
-                            } else if self.tcx().is_dyn_compatible(principal.def_id()) {
-                                principal.with_self_ty(self.tcx(), self_ty)
-                            } else {
-                                return;
-                            }
+                            principal.with_self_ty(self.tcx(), self_ty)
                         } else {
                             // Only auto trait bounds exist.
                             return;
@@ -920,11 +919,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         //     T: Trait
         // so it seems ok if we (conservatively) fail to accept that `Unsize`
         // obligation above. Should be possible to extend this in the future.
-        let Some(source) = obligation.self_ty().no_bound_vars() else {
+        let Some(trait_pred) = obligation.predicate.no_bound_vars() else {
             // Don't add any candidates if there are bound regions.
             return;
         };
-        let target = obligation.predicate.skip_binder().trait_ref.args.type_at(1);
+        let source = trait_pred.self_ty();
+        let target = trait_pred.trait_ref.args.type_at(1);
 
         debug!(?source, ?target, "assemble_candidates_for_unsizing");
 
@@ -1183,4 +1183,48 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
         }
     }
+
+    fn assemble_candidates_for_bikeshed_guaranteed_no_drop_trait(
+        &mut self,
+        obligation: &PolyTraitObligation<'tcx>,
+        candidates: &mut SelectionCandidateSet<'tcx>,
+    ) {
+        match obligation.predicate.self_ty().skip_binder().kind() {
+            ty::Ref(..)
+            | ty::Adt(..)
+            | ty::Tuple(_)
+            | ty::Array(..)
+            | ty::FnDef(..)
+            | ty::FnPtr(..)
+            | ty::Error(_)
+            | ty::Uint(_)
+            | ty::Int(_)
+            | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+            | ty::Bool
+            | ty::Float(_)
+            | ty::Char
+            | ty::RawPtr(..)
+            | ty::Never
+            | ty::Pat(..)
+            | ty::Dynamic(..)
+            | ty::Str
+            | ty::Slice(_)
+            | ty::Foreign(..)
+            | ty::Alias(..)
+            | ty::Param(_)
+            | ty::Placeholder(..)
+            | ty::Closure(..)
+            | ty::CoroutineClosure(..)
+            | ty::Coroutine(..)
+            | ty::UnsafeBinder(_)
+            | ty::CoroutineWitness(..)
+            | ty::Bound(..) => {
+                candidates.vec.push(BikeshedGuaranteedNoDropCandidate);
+            }
+
+            ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+                candidates.ambiguous = true;
+            }
+        }
+    }
 }
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index eb4adde716a..32cbb97e314 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -20,6 +20,7 @@ use rustc_middle::ty::{self, GenericArgsRef, Ty, TyCtxt, Upcast};
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
 use rustc_type_ir::elaborate;
+use thin_vec::thin_vec;
 use tracing::{debug, instrument};
 
 use super::SelectionCandidate::{self, *};
@@ -130,6 +131,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             TraitUpcastingUnsizeCandidate(idx) => {
                 self.confirm_trait_upcasting_unsize_candidate(obligation, idx)?
             }
+
+            BikeshedGuaranteedNoDropCandidate => {
+                self.confirm_bikeshed_guaranteed_no_drop_candidate(obligation)
+            }
         };
 
         // The obligations returned by confirmation are recursively evaluated
@@ -1346,6 +1351,93 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             _ => bug!("source: {source}, target: {target}"),
         })
     }
+
+    fn confirm_bikeshed_guaranteed_no_drop_candidate(
+        &mut self,
+        obligation: &PolyTraitObligation<'tcx>,
+    ) -> ImplSource<'tcx, PredicateObligation<'tcx>> {
+        let mut obligations = thin_vec![];
+
+        let tcx = self.tcx();
+        let self_ty = obligation.predicate.self_ty();
+        match *self_ty.skip_binder().kind() {
+            // `&mut T` and `&T` always implement `BikeshedGuaranteedNoDrop`.
+            ty::Ref(..) => {}
+            // `ManuallyDrop<T>` always implements `BikeshedGuaranteedNoDrop`.
+            ty::Adt(def, _) if def.is_manually_drop() => {}
+            // Arrays and tuples implement `BikeshedGuaranteedNoDrop` only if
+            // their constituent types implement `BikeshedGuaranteedNoDrop`.
+            ty::Tuple(tys) => {
+                obligations.extend(tys.iter().map(|elem_ty| {
+                    obligation.with(
+                        tcx,
+                        self_ty.rebind(ty::TraitRef::new(
+                            tcx,
+                            obligation.predicate.def_id(),
+                            [elem_ty],
+                        )),
+                    )
+                }));
+            }
+            ty::Array(elem_ty, _) => {
+                obligations.push(obligation.with(
+                    tcx,
+                    self_ty.rebind(ty::TraitRef::new(
+                        tcx,
+                        obligation.predicate.def_id(),
+                        [elem_ty],
+                    )),
+                ));
+            }
+
+            // All other types implement `BikeshedGuaranteedNoDrop` only if
+            // they implement `Copy`. We could be smart here and short-circuit
+            // some trivially `Copy`/`!Copy` types, but there's no benefit.
+            ty::FnDef(..)
+            | ty::FnPtr(..)
+            | ty::Error(_)
+            | ty::Uint(_)
+            | ty::Int(_)
+            | ty::Infer(ty::IntVar(_) | ty::FloatVar(_))
+            | ty::Bool
+            | ty::Float(_)
+            | ty::Char
+            | ty::RawPtr(..)
+            | ty::Never
+            | ty::Pat(..)
+            | ty::Dynamic(..)
+            | ty::Str
+            | ty::Slice(_)
+            | ty::Foreign(..)
+            | ty::Adt(..)
+            | ty::Alias(..)
+            | ty::Param(_)
+            | ty::Placeholder(..)
+            | ty::Closure(..)
+            | ty::CoroutineClosure(..)
+            | ty::Coroutine(..)
+            | ty::UnsafeBinder(_)
+            | ty::CoroutineWitness(..)
+            | ty::Bound(..) => {
+                obligations.push(obligation.with(
+                    tcx,
+                    self_ty.map_bound(|ty| {
+                        ty::TraitRef::new(
+                            tcx,
+                            tcx.require_lang_item(LangItem::Copy, Some(obligation.cause.span)),
+                            [ty],
+                        )
+                    }),
+                ));
+            }
+
+            ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_)) => {
+                panic!("unexpected type `{self_ty:?}`")
+            }
+        }
+
+        ImplSource::Builtin(BuiltinImplSource::Misc, obligations)
+    }
 }
 
 /// Compute a goal that some RPITIT (right now, only RPITITs corresponding to Futures)
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 6b1e1774f03..436ce3dddd9 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1949,7 +1949,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 | TraitAliasCandidate
                 | TraitUpcastingUnsizeCandidate(_)
                 | BuiltinObjectCandidate
-                | BuiltinUnsizeCandidate => false,
+                | BuiltinUnsizeCandidate
+                | BikeshedGuaranteedNoDropCandidate => false,
                 // Non-global param candidates have already been handled, global
                 // where-bounds get ignored.
                 ParamCandidate(_) | ImplCandidate(_) => true,
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
index f39c611d19f..19d3561dd59 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
@@ -200,15 +200,12 @@ impl<'tcx> Children {
     }
 }
 
-fn iter_children(children: &Children) -> impl Iterator<Item = DefId> + '_ {
+fn iter_children(children: &Children) -> impl Iterator<Item = DefId> {
     let nonblanket = children.non_blanket_impls.iter().flat_map(|(_, v)| v.iter());
     children.blanket_impls.iter().chain(nonblanket).cloned()
 }
 
-fn filtered_children(
-    children: &mut Children,
-    st: SimplifiedType,
-) -> impl Iterator<Item = DefId> + '_ {
+fn filtered_children(children: &mut Children, st: SimplifiedType) -> impl Iterator<Item = DefId> {
     let nonblanket = children.non_blanket_impls.entry(st).or_default().iter();
     children.blanket_impls.iter().chain(nonblanket).cloned()
 }
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index d30363ec158..15f5cf916a4 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -47,11 +47,11 @@ pub fn expand_trait_aliases<'tcx>(
                     queue.extend(
                         tcx.explicit_super_predicates_of(trait_pred.def_id())
                             .iter_identity_copied()
-                            .map(|(clause, span)| {
+                            .map(|(super_clause, span)| {
                                 let mut spans = spans.clone();
                                 spans.push(span);
                                 (
-                                    clause.instantiate_supertrait(
+                                    super_clause.instantiate_supertrait(
                                         tcx,
                                         clause.kind().rebind(trait_pred.trait_ref),
                                     ),
diff --git a/compiler/rustc_trait_selection/src/traits/vtable.rs b/compiler/rustc_trait_selection/src/traits/vtable.rs
index 0024316b877..165174c0bcc 100644
--- a/compiler/rustc_trait_selection/src/traits/vtable.rs
+++ b/compiler/rustc_trait_selection/src/traits/vtable.rs
@@ -196,7 +196,7 @@ fn own_existential_vtable_entries(tcx: TyCtxt<'_>, trait_def_id: DefId) -> &[Def
 fn own_existential_vtable_entries_iter(
     tcx: TyCtxt<'_>,
     trait_def_id: DefId,
-) -> impl Iterator<Item = DefId> + '_ {
+) -> impl Iterator<Item = DefId> {
     let trait_methods = tcx
         .associated_items(trait_def_id)
         .in_definition_order()
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index 96051ad0aa5..18906a6a8ce 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -8,8 +8,9 @@ use rustc_middle::ty::{
     self, GenericArg, GenericArgKind, GenericArgsRef, Ty, TyCtxt, TypeSuperVisitable,
     TypeVisitable, TypeVisitableExt, TypeVisitor,
 };
-use rustc_span::Span;
+use rustc_session::parse::feature_err;
 use rustc_span::def_id::{DefId, LocalDefId};
+use rustc_span::{Span, sym};
 use tracing::{debug, instrument, trace};
 
 use crate::infer::InferCtxt;
@@ -288,7 +289,7 @@ fn extend_cause_with_original_assoc_item_obligation<'tcx>(
             && let Some(impl_item) =
                 items.iter().find(|item| item.id.owner_id.to_def_id() == impl_item_id)
         {
-            Some(tcx.hir().impl_item(impl_item.id).expect_type().span)
+            Some(tcx.hir_impl_item(impl_item.id).expect_type().span)
         } else {
             None
         }
@@ -704,8 +705,47 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                 ));
             }
 
-            ty::Pat(subty, _) => {
+            ty::Pat(subty, pat) => {
                 self.require_sized(subty, ObligationCauseCode::Misc);
+                match *pat {
+                    ty::PatternKind::Range { start, end, include_end: _ } => {
+                        let mut check = |c| {
+                            let cause = self.cause(ObligationCauseCode::Misc);
+                            self.out.push(traits::Obligation::with_depth(
+                                tcx,
+                                cause.clone(),
+                                self.recursion_depth,
+                                self.param_env,
+                                ty::Binder::dummy(ty::PredicateKind::Clause(
+                                    ty::ClauseKind::ConstArgHasType(c, subty),
+                                )),
+                            ));
+                            if !tcx.features().generic_pattern_types() {
+                                if c.has_param() {
+                                    if self.span.is_dummy() {
+                                        self.tcx().dcx().delayed_bug(
+                                            "feature error should be reported elsewhere, too",
+                                        );
+                                    } else {
+                                        feature_err(
+                                            &self.tcx().sess,
+                                            sym::generic_pattern_types,
+                                            self.span,
+                                            "wraparound pattern type ranges cause monomorphization time errors",
+                                        )
+                                        .emit();
+                                    }
+                                }
+                            }
+                        };
+                        if let Some(start) = start {
+                            check(start)
+                        }
+                        if let Some(end) = end {
+                            check(end)
+                        }
+                    }
+                }
             }
 
             ty::Tuple(tys) => {
@@ -841,7 +881,10 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                         ty.map_bound(|ty| {
                             ty::TraitRef::new(
                                 self.tcx(),
-                                self.tcx().require_lang_item(LangItem::Copy, Some(self.span)),
+                                self.tcx().require_lang_item(
+                                    LangItem::BikeshedGuaranteedNoDrop,
+                                    Some(self.span),
+                                ),
                                 [ty],
                             )
                         }),
@@ -861,19 +904,14 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for WfPredicates<'a, 'tcx> {
                 // FIXME(#27579) RFC also considers adding trait
                 // obligations that don't refer to Self and
                 // checking those
-
-                let defer_to_coercion = tcx.features().dyn_compatible_for_dispatch();
-
-                if !defer_to_coercion {
-                    if let Some(principal) = data.principal_def_id() {
-                        self.out.push(traits::Obligation::with_depth(
-                            tcx,
-                            self.cause(ObligationCauseCode::WellFormed(None)),
-                            self.recursion_depth,
-                            self.param_env,
-                            ty::Binder::dummy(ty::PredicateKind::DynCompatible(principal)),
-                        ));
-                    }
+                if let Some(principal) = data.principal_def_id() {
+                    self.out.push(traits::Obligation::with_depth(
+                        tcx,
+                        self.cause(ObligationCauseCode::WellFormed(None)),
+                        self.recursion_depth,
+                        self.param_env,
+                        ty::Binder::dummy(ty::PredicateKind::DynCompatible(principal)),
+                    ));
                 }
             }