[CRATER] probe fallout of dyn overlap

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -391,6 +391,12 @@ fn check_trait_item<'tcx>(
     // Check that an item definition in a subtrait is shadowing a supertrait item.
     lint_item_shadowing_supertrait_item(tcx, def_id);
 
+    for blanket_impl_def_id in tcx.all_impls(def_id.to_def_id()) {
+        if !blanket_impl_def_id.is_local() {
+            tcx.ensure_ok().lint_object_blanket_impl((blanket_impl_def_id, def_id.to_def_id()));
+        }
+    }
+
     let mut res = check_associated_item(tcx, def_id, span, method_sig);
 
     if matches!(trait_item.kind, hir::TraitItemKind::Fn(..)) {

compiler/rustc_hir_analysis/src/impl_wf_check.rs

@@ -10,16 +10,23 @@
 
 use std::assert_matches::debug_assert_matches;
 
-use min_specialization::check_min_specialization;
+use itertools::Itertools;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::codes::*;
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::LocalDefId;
-use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
-use rustc_span::ErrorGuaranteed;
+use rustc_hir::def_id::{DefId, LOCAL_CRATE, LocalDefId};
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_lint_defs::builtin::DYN_OVERLAP;
+use rustc_middle::ty::{
+    self, ExistentialPredicateStableCmpExt, Ty, TyCtxt, TypeVisitableExt, TypingMode, Upcast,
+    elaborate,
+};
+use rustc_span::{DUMMY_SP, ErrorGuaranteed, sym};
+use rustc_trait_selection::traits::{Obligation, ObligationCause, ObligationCtxt};
 
 use crate::constrained_generic_params as cgp;
 use crate::errors::UnconstrainedGenericParameter;
+use crate::impl_wf_check::min_specialization::check_min_specialization;
 
 mod min_specialization;
 
@@ -68,6 +75,22 @@ pub(crate) fn check_impl_wf(
     if tcx.features().min_specialization() {
         res = res.and(check_min_specialization(tcx, impl_def_id));
     }
+
+    if let Some(trait_def_id) = tcx.trait_id_of_impl(impl_def_id.to_def_id()) {
+        for &subtrait_def_id in tcx
+            .crates(())
+            .into_iter()
+            .copied()
+            .chain([LOCAL_CRATE])
+            .flat_map(|cnum| tcx.traits(cnum))
+        {
+            if ty::elaborate::supertrait_def_ids(tcx, subtrait_def_id).contains(&trait_def_id) {
+                tcx.ensure_ok()
+                    .lint_object_blanket_impl((impl_def_id.to_def_id(), subtrait_def_id));
+            }
+        }
+    }
+
     res
 }
 
@@ -234,3 +257,120 @@ pub(crate) fn enforce_impl_non_lifetime_params_are_constrained(
     }
     res
 }
+
+pub(crate) fn lint_object_blanket_impl<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    (impl_def_id, trait_def_id): (DefId, DefId),
+) {
+    if tcx.is_diagnostic_item(sym::Any, trait_def_id) {
+        return;
+    }
+
+    if !tcx.is_dyn_compatible(trait_def_id) {
+        return;
+    }
+
+    let infcx = tcx.infer_ctxt().with_next_trait_solver(true).build(TypingMode::CheckObjectOverlap);
+
+    let principal_trait_args = infcx.fresh_args_for_item(DUMMY_SP, trait_def_id);
+    let principal_trait = ty::TraitRef::new_from_args(tcx, trait_def_id, principal_trait_args);
+
+    let mut needed_associated_types = vec![];
+    let clause: ty::Clause<'tcx> = ty::TraitRef::identity(tcx, trait_def_id).upcast(tcx);
+    for clause in elaborate::elaborate(tcx, [clause]).filter_only_self() {
+        let clause = clause.instantiate_supertrait(tcx, ty::Binder::dummy(principal_trait));
+
+        let bound_predicate = clause.kind();
+        match bound_predicate.skip_binder() {
+            ty::ClauseKind::Trait(pred) => {
+                // FIXME(negative_bounds): Handle this correctly...
+                let trait_ref = tcx.anonymize_bound_vars(bound_predicate.rebind(pred.trait_ref));
+                needed_associated_types.extend(
+                    tcx.associated_items(pred.trait_ref.def_id)
+                        .in_definition_order()
+                        // We only care about associated types.
+                        .filter(|item| item.is_type())
+                        // No RPITITs -- they're not dyn-compatible for now.
+                        .filter(|item| !item.is_impl_trait_in_trait())
+                        // If the associated type has a `where Self: Sized` bound,
+                        // we do not need to constrain the associated type.
+                        .filter(|item| !tcx.generics_require_sized_self(item.def_id))
+                        .map(|item| (item.def_id, trait_ref)),
+                );
+            }
+            _ => (),
+        }
+    }
+
+    let mut data: Vec<_> = [ty::Binder::dummy(ty::ExistentialPredicate::Trait(
+        ty::ExistentialTraitRef::erase_self_ty(tcx, principal_trait),
+    ))]
+    .into_iter()
+    .chain(needed_associated_types.into_iter().map(|(def_id, trait_ref)| {
+        trait_ref.map_bound(|trait_ref| {
+            ty::ExistentialPredicate::Projection(ty::ExistentialProjection::erase_self_ty(
+                tcx,
+                ty::ProjectionPredicate {
+                    projection_term: ty::AliasTerm::new_from_args(tcx, def_id, trait_ref.args),
+                    term: infcx.next_ty_var(DUMMY_SP).into(),
+                },
+            ))
+        })
+    }))
+    .collect();
+    data.sort_by(|a, b| a.skip_binder().stable_cmp(tcx, &b.skip_binder()));
+
+    let self_ty = Ty::new_dynamic(
+        tcx,
+        tcx.mk_poly_existential_predicates(&data),
+        tcx.lifetimes.re_erased,
+        ty::Dyn,
+    );
+
+    let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
+    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(tcx, impl_args);
+
+    let ocx = ObligationCtxt::new(&infcx);
+    let Ok(()) =
+        ocx.eq(&ObligationCause::dummy(), ty::ParamEnv::empty(), principal_trait, impl_trait_ref)
+    else {
+        return;
+    };
+    let Ok(()) =
+        ocx.eq(&ObligationCause::dummy(), ty::ParamEnv::empty(), self_ty, impl_trait_ref.self_ty())
+    else {
+        return;
+    };
+
+    ocx.register_obligations(
+        tcx.predicates_of(impl_def_id).instantiate(tcx, impl_args).into_iter().map(
+            |(clause, _)| {
+                Obligation::new(tcx, ObligationCause::dummy(), ty::ParamEnv::empty(), clause)
+            },
+        ),
+    );
+
+    if !ocx.select_where_possible().is_empty() {
+        return;
+    }
+
+    let local_def_id = if let Some(impl_def_id) = impl_def_id.as_local() {
+        impl_def_id
+    } else if let Some(trait_def_id) = trait_def_id.as_local() {
+        trait_def_id
+    } else {
+        panic!()
+    };
+    let hir_id = tcx.local_def_id_to_hir_id(local_def_id);
+
+    let self_ty = infcx.resolve_vars_if_possible(self_ty);
+
+    tcx.node_span_lint(DYN_OVERLAP, hir_id, tcx.def_span(local_def_id), |diag| {
+        diag.primary_message("hi");
+        diag.span_label(
+            tcx.def_span(trait_def_id),
+            format!("built-in `{self_ty}` implementation for this trait"),
+        );
+        diag.span_label(tcx.def_span(impl_def_id), "overlaps with this blanket impl");
+    });
+}

compiler/rustc_hir_analysis/src/lib.rs

@@ -171,6 +171,7 @@ pub fn provide(providers: &mut Providers) {
         inherit_sig_for_delegation_item: delegation::inherit_sig_for_delegation_item,
         enforce_impl_non_lifetime_params_are_constrained:
             impl_wf_check::enforce_impl_non_lifetime_params_are_constrained,
+        lint_object_blanket_impl: impl_wf_check::lint_object_blanket_impl,
         ..*providers
     };
 }

compiler/rustc_infer/src/infer/mod.rs

@@ -968,6 +968,7 @@ impl<'tcx> InferCtxt<'tcx> {
             // and post-borrowck analysis mode. We may need to modify its uses
             // to support PostBorrowckAnalysis in the old solver as well.
             TypingMode::Coherence
+            | TypingMode::CheckObjectOverlap
             | TypingMode::PostBorrowckAnalysis { .. }
             | TypingMode::PostAnalysis => false,
         }
@@ -1260,6 +1261,7 @@ impl<'tcx> InferCtxt<'tcx> {
                 TypingMode::non_body_analysis()
             }
             mode @ (ty::TypingMode::Coherence
+            | TypingMode::CheckObjectOverlap
             | ty::TypingMode::PostBorrowckAnalysis { .. }
             | ty::TypingMode::PostAnalysis) => mode,
         };

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

@@ -87,7 +87,9 @@ impl<'tcx> InferCtxt<'tcx> {
         let process = |a: Ty<'tcx>, b: Ty<'tcx>| match *a.kind() {
             ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) if def_id.is_local() => {
                 let def_id = def_id.expect_local();
-                if let ty::TypingMode::Coherence = self.typing_mode() {
+                if let ty::TypingMode::Coherence | ty::TypingMode::CheckObjectOverlap =
+                    self.typing_mode()
+                {
                     // See comment on `insert_hidden_type` for why this is sufficient in coherence
                     return Some(self.register_hidden_type(
                         OpaqueTypeKey { def_id, args },
@@ -226,7 +228,7 @@ impl<'tcx> InferCtxt<'tcx> {
         // these are the same span, but not in cases like `-> (impl
         // Foo, impl Bar)`.
         match self.typing_mode() {
-            ty::TypingMode::Coherence => {
+            ty::TypingMode::Coherence | ty::TypingMode::CheckObjectOverlap => {
                 // During intercrate we do not define opaque types but instead always
                 // force ambiguity unless the hidden type is known to not implement
                 // our trait.

compiler/rustc_infer/src/infer/relate/generalize.rs

@@ -519,7 +519,10 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
                             //
                             // cc trait-system-refactor-initiative#108
                             if self.infcx.next_trait_solver()
-                                && !matches!(self.infcx.typing_mode(), TypingMode::Coherence)
+                                && !matches!(
+                                    self.infcx.typing_mode(),
+                                    TypingMode::Coherence | TypingMode::CheckObjectOverlap
+                                )
                                 && self.in_alias
                             {
                                 inner.type_variables().equate(vid, new_var_id);
@@ -650,7 +653,10 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
                             // See the comment for type inference variables
                             // for more details.
                             if self.infcx.next_trait_solver()
-                                && !matches!(self.infcx.typing_mode(), TypingMode::Coherence)
+                                && !matches!(
+                                    self.infcx.typing_mode(),
+                                    TypingMode::Coherence | TypingMode::CheckObjectOverlap
+                                )
                                 && self.in_alias
                             {
                                 variable_table.union(vid, new_var_id);

compiler/rustc_lint_defs/src/builtin.rs

@@ -37,6 +37,7 @@ declare_lint_pass! {
         DEPRECATED_SAFE_2024,
         DEPRECATED_WHERE_CLAUSE_LOCATION,
         DUPLICATE_MACRO_ATTRIBUTES,
+        DYN_OVERLAP,
         ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
         ELIDED_LIFETIMES_IN_PATHS,
         ELIDED_NAMED_LIFETIMES,
@@ -5067,3 +5068,14 @@ declare_lint! {
         reference: "issue #138762 <https://github.com/rust-lang/rust/issues/138762>",
     };
 }
+
+declare_lint! {
+    /// The `dyn_overlap` lint is one of the lints of all time.
+    ///
+    /// ### Uwu
+    ///
+    /// Owo
+    pub DYN_OVERLAP,
+    Forbid,
+    "owo",
+}

compiler/rustc_middle/src/query/mod.rs

@@ -527,6 +527,10 @@ rustc_queries! {
         anon
     }
 
+    query lint_object_blanket_impl(_: (DefId, DefId)) {
+        desc { "u if wu" }
+    }
+
     /// Set of param indexes for type params that are in the type's representation
     query params_in_repr(key: DefId) -> &'tcx rustc_index::bit_set::DenseBitSet<u32> {
         desc { "finding type parameters in the representation" }

compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs

@@ -380,7 +380,7 @@ where
 
         let mut candidates = vec![];
 
-        if let TypingMode::Coherence = self.typing_mode() {
+        if let TypingMode::Coherence | TypingMode::CheckObjectOverlap = self.typing_mode() {
             if let Ok(candidate) = self.consider_coherence_unknowable_candidate(goal) {
                 return vec![candidate];
             }
@@ -831,7 +831,7 @@ where
         candidates: &mut Vec<Candidate<I>>,
     ) {
         match self.typing_mode() {
-            TypingMode::Coherence => return,
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap => return,
             TypingMode::Analysis { .. }
             | TypingMode::Borrowck { .. }
             | TypingMode::PostBorrowckAnalysis { .. }

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -948,7 +948,8 @@ where
                     GoalSource::TypeRelating
                 }
                 // FIXME(-Znext-solver=coinductive): should these WF goals also be unproductive?
-                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_)) => GoalSource::Misc,
+                ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(_))
+                | ty::PredicateKind::Ambiguous => GoalSource::Misc,
                 p => unreachable!("unexpected nested goal in `relate`: {p:?}"),
             };
             self.add_goal(source, goal);

compiler/rustc_next_trait_solver/src/solve/mod.rs

@@ -339,7 +339,9 @@ where
     fn opaque_type_is_rigid(&self, def_id: I::DefId) -> bool {
         match self.typing_mode() {
             // Opaques are never rigid outside of analysis mode.
-            TypingMode::Coherence | TypingMode::PostAnalysis => false,
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap | TypingMode::PostAnalysis => {
+                false
+            }
             // During analysis, opaques are rigid unless they may be defined by
             // the current body.
             TypingMode::Analysis { defining_opaque_types_and_generators: non_rigid_opaques }

compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs

@@ -240,7 +240,7 @@ where
                         // would be relevant if any of the nested goals refer to the `term`.
                         // This is not the case here and we only prefer adding an ambiguous
                         // nested goal for consistency.
-                        ty::TypingMode::Coherence => {
+                        ty::TypingMode::Coherence | ty::TypingMode::CheckObjectOverlap => {
                             ecx.add_goal(GoalSource::Misc, goal.with(cx, PredicateKind::Ambiguous));
                             return ecx
                                 .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
@@ -280,7 +280,7 @@ where
                         // would be relevant if any of the nested goals refer to the `term`.
                         // This is not the case here and we only prefer adding an ambiguous
                         // nested goal for consistency.
-                        ty::TypingMode::Coherence => {
+                        ty::TypingMode::Coherence | ty::TypingMode::CheckObjectOverlap => {
                             ecx.add_goal(GoalSource::Misc, goal.with(cx, PredicateKind::Ambiguous));
                             return ecx
                                 .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);

compiler/rustc_next_trait_solver/src/solve/normalizes_to/opaque_types.rs

@@ -23,7 +23,7 @@ where
         let expected = goal.predicate.term.as_type().expect("no such thing as an opaque const");
 
         match self.typing_mode() {
-            TypingMode::Coherence => {
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap => {
                 // An impossible opaque type bound is the only way this goal will fail
                 // e.g. assigning `impl Copy := NotCopy`
                 self.add_item_bounds_for_hidden_type(

compiler/rustc_next_trait_solver/src/solve/search_graph.rs

@@ -58,7 +58,7 @@ where
             // example where this would matter. We likely should change these cycles to `NoSolution`
             // even in coherence once this is a bit more settled.
             PathKind::Inductive => match input.typing_mode {
-                TypingMode::Coherence => {
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap => {
                     response_no_constraints(cx, input, Certainty::overflow(false))
                 }
                 TypingMode::Analysis { .. }

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -70,7 +70,7 @@ where
             // In intercrate mode, this is ambiguous. But outside of intercrate,
             // it's not a real impl.
             (ty::ImplPolarity::Reservation, _) => match ecx.typing_mode() {
-                TypingMode::Coherence => Certainty::AMBIGUOUS,
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap => Certainty::AMBIGUOUS,
                 TypingMode::Analysis { .. }
                 | TypingMode::Borrowck { .. }
                 | TypingMode::PostBorrowckAnalysis { .. }
@@ -1257,7 +1257,7 @@ where
         &mut self,
         mut candidates: Vec<Candidate<I>>,
     ) -> Result<(CanonicalResponse<I>, Option<TraitGoalProvenVia>), NoSolution> {
-        if let TypingMode::Coherence = self.typing_mode() {
+        if let TypingMode::Coherence | TypingMode::CheckObjectOverlap = self.typing_mode() {
             let all_candidates: Vec<_> = candidates.into_iter().map(|c| c.result).collect();
             return if let Some(response) = self.try_merge_responses(&all_candidates) {
                 Ok((response, Some(TraitGoalProvenVia::Misc)))
@@ -1360,6 +1360,7 @@ where
                     }
                 }
                 TypingMode::Coherence
+                | TypingMode::CheckObjectOverlap
                 | TypingMode::PostAnalysis
                 | TypingMode::Borrowck { defining_opaque_types: _ }
                 | TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ } => {}

compiler/rustc_pattern_analysis/src/lib.rs

@@ -31,7 +31,7 @@ use crate::constructor::{Constructor, ConstructorSet, IntRange};
 use crate::pat::DeconstructedPat;
 
 pub trait Captures<'a> {}
-impl<'a, T: ?Sized> Captures<'a> for T {}
+impl<'a, T> Captures<'a> for T {}
 
 /// `bool` newtype that indicates whether this is a privately uninhabited field that we should skip
 /// during analysis.

compiler/rustc_trait_selection/src/solve/delegate.rs

@@ -178,6 +178,7 @@ impl<'tcx> rustc_next_trait_solver::delegate::SolverDelegate for SolverDelegate<
             // get a result which isn't correct for all monomorphizations.
             match self.typing_mode() {
                 TypingMode::Coherence
+                | TypingMode::CheckObjectOverlap
                 | TypingMode::Analysis { .. }
                 | TypingMode::Borrowck { .. }
                 | TypingMode::PostBorrowckAnalysis { .. } => false,

compiler/rustc_trait_selection/src/solve/fulfill.rs

@@ -229,6 +229,7 @@ where
                 defining_opaque_types_and_generators
             }
             TypingMode::Coherence
+            | TypingMode::CheckObjectOverlap
             | TypingMode::Borrowck { defining_opaque_types: _ }
             | TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ }
             | TypingMode::PostAnalysis => return Default::default(),

compiler/rustc_trait_selection/src/traits/effects.rs

@@ -24,7 +24,7 @@ pub fn evaluate_host_effect_obligation<'tcx>(
     selcx: &mut SelectionContext<'_, 'tcx>,
     obligation: &HostEffectObligation<'tcx>,
 ) -> Result<ThinVec<PredicateObligation<'tcx>>, EvaluationFailure> {
-    if matches!(selcx.infcx.typing_mode(), TypingMode::Coherence) {
+    if matches!(selcx.infcx.typing_mode(), TypingMode::Coherence | TypingMode::CheckObjectOverlap) {
         span_bug!(
             obligation.cause.span,
             "should not select host obligation in old solver in intercrate mode"

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -793,7 +793,11 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
         stalled_on: &mut Vec<TyOrConstInferVar>,
     ) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
         let infcx = self.selcx.infcx;
-        if obligation.predicate.is_global() && !matches!(infcx.typing_mode(), TypingMode::Coherence)
+        if obligation.predicate.is_global()
+            && !matches!(
+                infcx.typing_mode(),
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap
+            )
         {
             // no type variables present, can use evaluation for better caching.
             // FIXME: consider caching errors too.
@@ -848,7 +852,11 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
     ) -> ProcessResult<PendingPredicateObligation<'tcx>, FulfillmentErrorCode<'tcx>> {
         let tcx = self.selcx.tcx();
         let infcx = self.selcx.infcx;
-        if obligation.predicate.is_global() && !matches!(infcx.typing_mode(), TypingMode::Coherence)
+        if obligation.predicate.is_global()
+            && !matches!(
+                infcx.typing_mode(),
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap
+            )
         {
             // no type variables present, can use evaluation for better caching.
             // FIXME: consider caching errors too.

compiler/rustc_trait_selection/src/traits/normalize.rs

@@ -135,6 +135,7 @@ pub(super) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>(
     match infcx.typing_mode() {
         // FIXME(#132279): We likely want to reveal opaques during post borrowck analysis
         TypingMode::Coherence
+        | TypingMode::CheckObjectOverlap
         | TypingMode::Analysis { .. }
         | TypingMode::Borrowck { .. }
         | TypingMode::PostBorrowckAnalysis { .. } => flags.remove(ty::TypeFlags::HAS_TY_OPAQUE),
@@ -389,6 +390,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                 match self.selcx.infcx.typing_mode() {
                     // FIXME(#132279): We likely want to reveal opaques during post borrowck analysis
                     TypingMode::Coherence
+                    | TypingMode::CheckObjectOverlap
                     | TypingMode::Analysis { .. }
                     | TypingMode::Borrowck { .. }
                     | TypingMode::PostBorrowckAnalysis { .. } => ty.super_fold_with(self),

compiler/rustc_trait_selection/src/traits/project.rs

@@ -938,6 +938,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
                             // get a result which isn't correct for all monomorphizations.
                             match selcx.infcx.typing_mode() {
                                 TypingMode::Coherence
+                                | TypingMode::CheckObjectOverlap
                                 | TypingMode::Analysis { .. }
                                 | TypingMode::Borrowck { .. }
                                 | TypingMode::PostBorrowckAnalysis { .. } => {

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -215,6 +215,7 @@ impl<'a, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'a, 'tcx> {
                 // Only normalize `impl Trait` outside of type inference, usually in codegen.
                 match self.infcx.typing_mode() {
                     TypingMode::Coherence
+                    | TypingMode::CheckObjectOverlap
                     | TypingMode::Analysis { .. }
                     | TypingMode::Borrowck { .. }
                     | TypingMode::PostBorrowckAnalysis { .. } => ty.try_super_fold_with(self)?,

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -779,7 +779,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                         //
                         // Note that this is only sound as projection candidates of opaque types
                         // are always applicable for auto traits.
-                    } else if let TypingMode::Coherence = self.infcx.typing_mode() {
+                    } else if let TypingMode::Coherence | TypingMode::CheckObjectOverlap =
+                        self.infcx.typing_mode()
+                    {
                         // We do not emit auto trait candidates for opaque types in coherence.
                         // Doing so can result in weird dependency cycles.
                         candidates.ambiguous = true;

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -1004,8 +1004,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         previous_stack: TraitObligationStackList<'o, 'tcx>,
         mut obligation: PolyTraitObligation<'tcx>,
     ) -> Result<EvaluationResult, OverflowError> {
-        if !matches!(self.infcx.typing_mode(), TypingMode::Coherence)
-            && obligation.is_global()
+        if !matches!(
+            self.infcx.typing_mode(),
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap
+        ) && obligation.is_global()
             && obligation.param_env.caller_bounds().iter().all(|bound| bound.has_param())
         {
             // If a param env has no global bounds, global obligations do not
@@ -1449,7 +1451,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     fn is_knowable<'o>(&mut self, stack: &TraitObligationStack<'o, 'tcx>) -> Result<(), Conflict> {
         let obligation = &stack.obligation;
         match self.infcx.typing_mode() {
-            TypingMode::Coherence => {}
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap => {}
             TypingMode::Analysis { .. }
             | TypingMode::Borrowck { .. }
             | TypingMode::PostBorrowckAnalysis { .. }
@@ -1488,7 +1490,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // the master cache. Since coherence executes pretty quickly,
             // it's not worth going to more trouble to increase the
             // hit-rate, I don't think.
-            TypingMode::Coherence => false,
+            TypingMode::Coherence | TypingMode::CheckObjectOverlap => false,
             // Avoid using the global cache when we're defining opaque types
             // as their hidden type may impact the result of candidate selection.
             //
@@ -2509,7 +2511,10 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         nested_obligations.extend(obligations);
 
         if impl_trait_header.polarity == ty::ImplPolarity::Reservation
-            && !matches!(self.infcx.typing_mode(), TypingMode::Coherence)
+            && !matches!(
+                self.infcx.typing_mode(),
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap
+            )
         {
             debug!("reservation impls only apply in intercrate mode");
             return Err(());

compiler/rustc_ty_utils/src/instance.rs

@@ -156,6 +156,7 @@ fn resolve_associated_item<'tcx>(
                 // get a result which isn't correct for all monomorphizations.
                 match typing_env.typing_mode {
                     ty::TypingMode::Coherence
+                    | ty::TypingMode::CheckObjectOverlap
                     | ty::TypingMode::Analysis { .. }
                     | ty::TypingMode::Borrowck { .. }
                     | ty::TypingMode::PostBorrowckAnalysis { .. } => false,

compiler/rustc_type_ir/src/infer_ctxt.rs

@@ -67,21 +67,27 @@ pub enum TypingMode<I: Interner> {
     ///     let x: <() as Assoc>::Output = true;
     /// }
     /// ```
-    Analysis { defining_opaque_types_and_generators: I::LocalDefIds },
+    Analysis {
+        defining_opaque_types_and_generators: I::LocalDefIds,
+    },
     /// The behavior during MIR borrowck is identical to `TypingMode::Analysis`
     /// except that the initial value for opaque types is the type computed during
     /// HIR typeck with unique unconstrained region inference variables.
     ///
     /// This is currently only used with by the new solver as it results in new
     /// non-universal defining uses of opaque types, which is a breaking change.
     /// See tests/ui/impl-trait/non-defining-use/as-projection-term.rs.
-    Borrowck { defining_opaque_types: I::LocalDefIds },
+    Borrowck {
+        defining_opaque_types: I::LocalDefIds,
+    },
     /// Any analysis after borrowck for a given body should be able to use all the
     /// hidden types defined by borrowck, without being able to define any new ones.
     ///
     /// This is currently only used by the new solver, but should be implemented in
     /// the old solver as well.
-    PostBorrowckAnalysis { defined_opaque_types: I::LocalDefIds },
+    PostBorrowckAnalysis {
+        defined_opaque_types: I::LocalDefIds,
+    },
     /// After analysis, mostly during codegen and MIR optimizations, we're able to
     /// reveal all opaque types. As the concrete type should *never* be observable
     /// directly by the user, this should not be used by checks which may expose
@@ -91,6 +97,11 @@ pub enum TypingMode<I: Interner> {
     /// always run in `PostAnalysis` mode, even when used during analysis. This exposes
     /// some information about the underlying type to users, but not the type itself.
     PostAnalysis,
+
+    // Hack modes:
+
+    // TODUwU:
+    CheckObjectOverlap,
 }
 
 impl<I: Interner> TypingMode<I> {

compiler/rustc_type_ir/src/relate/combine.rs

@@ -132,7 +132,7 @@ where
                 // equal to any other type. This is an
                 // extremely heavy hammer, but can be relaxed in a forwards-compatible
                 // way later.
-                TypingMode::Coherence => {
+                TypingMode::Coherence | TypingMode::CheckObjectOverlap => {
                     relation.register_predicates([ty::Binder::dummy(ty::PredicateKind::Ambiguous)]);
                     Ok(a)
                 }
@@ -143,6 +143,15 @@ where
             }
         }
 
+        (ty::Dynamic(a_data, _, a_kind), ty::Dynamic(b_data, _, b_kind))
+            if a_data.principal_def_id() == b_data.principal_def_id()
+                && a_kind == b_kind
+                && matches!(infcx.typing_mode(), TypingMode::CheckObjectOverlap) =>
+        {
+            relation.register_predicates([ty::Binder::dummy(ty::PredicateKind::Ambiguous)]);
+            Ok(a)
+        }
+
         _ => structurally_relate_tys(relation, a, b),
     }
 }

library/std/src/io/buffered/bufreader.rs

@@ -579,7 +579,7 @@ impl<R: ?Sized + Seek> Seek for BufReader<R> {
     }
 }
 
-impl<T: ?Sized> SizeHint for BufReader<T> {
+impl<T> SizeHint for BufReader<T> {
     #[inline]
     fn lower_bound(&self) -> usize {
         SizeHint::lower_bound(self.get_ref()) + self.buffer().len()

library/std/src/io/mod.rs

@@ -3151,7 +3151,7 @@ trait SizeHint {
     }
 }
 
-impl<T: ?Sized> SizeHint for T {
+impl<T> SizeHint for T {
     #[inline]
     default fn lower_bound(&self) -> usize {
         0

tests/ui/associated-consts/assoc-const-eq-bound-var-in-ty-not-wf.stderr

@@ -21,5 +21,15 @@ LL | fn take(
    = note: `Project` would have to be implemented for the type `for<'a> fn(&'a str) -> &'a str`
    = note: ...but `Project` is actually implemented for the type `fn(&'0 str) -> &'0 str`, for some specific lifetime `'0`
 
-error: aborting due to 3 previous errors
+error: hi
+  --> $DIR/assoc-const-eq-bound-var-in-ty-not-wf.rs:23:1
+   |
+LL | trait Discard { type Out; }
+   | ------------- built-in `dyn Discard<Out = _>` implementation for this trait
+LL | impl<T: ?Sized> Discard for T { type Out = (); }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 4 previous errors
 

tests/ui/associated-type-bounds/cant-see-copy-bound-from-child-rigid-2.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/cant-see-copy-bound-from-child-rigid-2.rs:4:1
+   |
+LL | trait Id {
+   | -------- built-in `dyn Id<This = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Id for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0382]: use of moved value: `x`
   --> $DIR/cant-see-copy-bound-from-child-rigid-2.rs:14:9
    |
@@ -8,6 +19,6 @@ LL |     (x, x)
    |      |
    |      value moved here
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

tests/ui/associated-types/associated-types-coherence-failure.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/associated-types-coherence-failure.rs:15:1
+   |
+LL | pub trait IntoCow<'a, B: ?Sized> {
+   | -------------------------------- built-in `dyn IntoCow<'_, _>` implementation for this trait
+...
+LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:21:1
    |
@@ -16,6 +27,6 @@ LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwn
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for &'a B where B: ToOwned {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/borrowck/ice-mutability-error-slicing-121807.stderr

@@ -23,6 +23,12 @@ LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
    = note: for more information, see issue #41686 <https://github.com/rust-lang/rust/issues/41686>
    = note: `#[warn(anonymous_parameters)]` on by default
 
+error[E0220]: associated type `Assoc` not found for `Self`
+  --> $DIR/ice-mutability-error-slicing-121807.rs:7:36
+   |
+LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
+   |                                    ^^^^^ associated type `Assoc` not found
+
 error[E0185]: method `read_dword` has a `&self` declaration in the impl, but not in the trait
   --> $DIR/ice-mutability-error-slicing-121807.rs:17:5
    |
@@ -41,12 +47,6 @@ LL |     extern "C" fn read_word(&mut self) -> u8;
 LL | impl MemoryUnit for ROM {
    | ^^^^^^^^^^^^^^^^^^^^^^^ missing `read_word` in implementation
 
-error[E0220]: associated type `Assoc` not found for `Self`
-  --> $DIR/ice-mutability-error-slicing-121807.rs:7:36
-   |
-LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
-   |                                    ^^^^^ associated type `Assoc` not found
-
 error: aborting due to 4 previous errors; 1 warning emitted
 
 Some errors have detailed explanations: E0046, E0185, E0220, E0261.

tests/ui/borrowck/trait-impl-argument-difference-ice.stderr

@@ -8,6 +8,12 @@ LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
    = note: for more information, see issue #41686 <https://github.com/rust-lang/rust/issues/41686>
    = note: `#[warn(anonymous_parameters)]` on by default
 
+error[E0220]: associated type `Assoc` not found for `Self`
+  --> $DIR/trait-impl-argument-difference-ice.rs:4:36
+   |
+LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
+   |                                    ^^^^^ associated type `Assoc` not found
+
 error[E0185]: method `read_dword` has a `&self` declaration in the impl, but not in the trait
   --> $DIR/trait-impl-argument-difference-ice.rs:14:5
    |
@@ -26,12 +32,6 @@ LL |     extern "C" fn read_word(&mut self) -> u8;
 LL | impl MemoryUnit for ROM {
    | ^^^^^^^^^^^^^^^^^^^^^^^ missing `read_word` in implementation
 
-error[E0220]: associated type `Assoc` not found for `Self`
-  --> $DIR/trait-impl-argument-difference-ice.rs:4:36
-   |
-LL |     extern "C" fn read_dword(Self::Assoc<'_>) -> u16;
-   |                                    ^^^^^ associated type `Assoc` not found
-
 error[E0596]: cannot borrow `*self` as mutable, as it is behind a `&` reference
   --> $DIR/trait-impl-argument-difference-ice.rs:16:19
    |

tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.current.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:14:1
+   |
+LL | trait Id {
+   | -------- built-in `dyn Id<Id = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Id for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: lifetime may not live long enough
   --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
    |
@@ -11,5 +22,5 @@ LL |     let _send = unsend as *const S<dyn Cat<'static>>;
    = note: the struct `S<T>` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 

tests/ui/cast/ptr-to-trait-obj-different-regions-id-trait.next.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:14:1
+   |
+LL | trait Id {
+   | -------- built-in `dyn Id<Id = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Id for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: lifetime may not live long enough
   --> $DIR/ptr-to-trait-obj-different-regions-id-trait.rs:24:27
    |
@@ -11,5 +22,5 @@ LL |     let _send = unsend as *const S<dyn Cat<'static>>;
    = note: the struct `S<T>` is invariant over the parameter `T`
    = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 

tests/ui/coherence/coherence-error-suppression.stderr

@@ -4,6 +4,17 @@ error[E0412]: cannot find type `DoesNotExist` in this scope
 LL | impl Foo for DoesNotExist {}
    |              ^^^^^^^^^^^^ not found in this scope
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/coherence-error-suppression.rs:9:1
+   |
+LL | trait Foo {}
+   | --------- built-in `dyn Foo` implementation for this trait
+...
+LL | impl Foo for DoesNotExist {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/coherence/coherence-impl-trait-for-marker-trait-negative.stderr

@@ -58,6 +58,16 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i
 LL | impl !Send for dyn Object + Marker2 {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
 
+error: hi
+  --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:32:1
+   |
+LL | auto trait Marker3 {}
+   | ------------------ built-in `dyn Marker3` implementation for this trait
+LL | impl<T: ?Sized> !Marker3 for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T`
   --> $DIR/coherence-impl-trait-for-marker-trait-negative.rs:32:1
    |
@@ -66,7 +76,7 @@ LL | impl<T: ?Sized> !Marker3 for T {}
    |
    = note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0117, E0321, E0371.
 For more information about an error, try `rustc --explain E0117`.

tests/ui/coherence/coherence-impl-trait-for-marker-trait-positive.stderr

@@ -58,6 +58,16 @@ error[E0321]: cross-crate traits with a default impl, like `Send`, can only be i
 LL | unsafe impl Send for dyn Object + Marker2 {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't implement cross-crate trait with a default impl for non-struct/enum type
 
+error: hi
+  --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:32:1
+   |
+LL | auto trait Marker3 {}
+   | ------------------ built-in `dyn Marker3` implementation for this trait
+LL | impl<T: ?Sized> Marker3 for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0321]: traits with a default impl, like `Marker3`, cannot be implemented for generic type `T`
   --> $DIR/coherence-impl-trait-for-marker-trait-positive.rs:32:1
    |
@@ -66,7 +76,7 @@ LL | impl<T: ?Sized> Marker3 for T {}
    |
    = note: a trait object implements `Marker3` if and only if `Marker3` is one of the trait object's trait bounds
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0117, E0321, E0371.
 For more information about an error, try `rustc --explain E0117`.

tests/ui/coherence/coherence-impl-trait-for-trait.stderr

@@ -10,12 +10,23 @@ error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the
 LL | impl Bar for dyn Baz { }
    | ^^^^^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Bar`
 
+error: hi
+  --> $DIR/coherence-impl-trait-for-trait.rs:13:1
+   |
+LL | trait Baz: Bar { }
+   | -------------- built-in `dyn Baz` implementation for this trait
+...
+LL | impl Baz for dyn Baz { }
+   | ^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0371]: the object type `(dyn Baz + 'static)` automatically implements the trait `Baz`
   --> $DIR/coherence-impl-trait-for-trait.rs:13:1
    |
 LL | impl Baz for dyn Baz { }
    | ^^^^^^^^^^^^^^^^^^^^ `(dyn Baz + 'static)` automatically implements trait `Baz`
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0371`.

tests/ui/coherence/indirect-impl-for-trait-obj-coherence.next.stderr

@@ -1,9 +1,20 @@
+error: hi
+  --> $DIR/indirect-impl-for-trait-obj-coherence.rs:15:1
+   |
+LL | trait Object<U> {
+   | --------------- built-in `dyn Object<_, Output = _>` implementation for this trait
+...
+LL | impl<T: ?Sized, U> Object<U> for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0284]: type annotations needed: cannot normalize `<dyn Object<U, Output = T> as Object<U>>::Output`
   --> $DIR/indirect-impl-for-trait-obj-coherence.rs:25:41
    |
 LL |     foo::<dyn Object<U, Output = T>, U>(x)
    |                                         ^ cannot normalize `<dyn Object<U, Output = T> as Object<U>>::Output`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0284`.

tests/ui/coherence/occurs-check/associated-type.next.stderr

@@ -14,6 +14,7 @@ LL | |     for<'a> *const T: ToUnit<'a>,
    |
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?3t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
 error[E0284]: type annotations needed: cannot normalize `<for<'a> fn(&'a (), ()) as Overlap<for<'a> fn(&'a (), ())>>::Assoc`
   --> $DIR/associated-type.rs:45:59
    |

tests/ui/coherence/occurs-check/associated-type.old.stderr

@@ -14,6 +14,7 @@ LL | |     for<'a> *const T: ToUnit<'a>,
    |
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?3t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
 error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/const-generics/min_const_generics/forbid-self-no-normalize.stderr

@@ -1,3 +1,23 @@
+error: hi
+  --> $DIR/forbid-self-no-normalize.rs:4:1
+   |
+LL | trait AlwaysApplicable {
+   | ---------------------- built-in `dyn AlwaysApplicable<Assoc = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> AlwaysApplicable for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: hi
+  --> $DIR/forbid-self-no-normalize.rs:11:1
+   |
+LL | trait BindsParam<T> {
+   | ------------------- built-in `dyn BindsParam<_, ArrayTy = _>` implementation for this trait
+...
+LL | impl<T> BindsParam<T> for <T as AlwaysApplicable>::Assoc {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
 error: generic `Self` types are currently not permitted in anonymous constants
   --> $DIR/forbid-self-no-normalize.rs:12:25
    |
@@ -10,5 +30,5 @@ note: not a concrete type
 LL | impl<T> BindsParam<T> for <T as AlwaysApplicable>::Assoc {
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 3 previous errors
 

tests/ui/const-generics/wrong-normalization.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/wrong-normalization.rs:10:1
+   |
+LL | pub trait Identity {
+   | ------------------ built-in `dyn Identity<Identity = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Identity for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0118]: no nominal type found for inherent implementation
   --> $DIR/wrong-normalization.rs:16:1
    |
@@ -6,6 +17,6 @@ LL | impl <I8<{i8::MIN}> as Identity>::Identity {
    |
    = note: either implement a trait on it or create a newtype to wrap it instead
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0118`.

tests/ui/dropck/drop-on-non-struct.stderr

@@ -22,7 +22,18 @@ error[E0120]: the `Drop` trait may only be implemented for local structs, enums,
 LL | impl<'a> Drop for &'a mut isize {
    |                   ^^^^^^^^^^^^^ must be a struct, enum, or union in the current crate
 
-error: aborting due to 3 previous errors
+error: hi
+  --> $DIR/drop-on-non-struct.rs:9:1
+   |
+LL | impl Drop for Nonexistent {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/ops/drop.rs:LL:COL
+   |
+   = note: built-in `dyn Drop` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0117, E0120, E0412.
 For more information about an error, try `rustc --explain E0117`.

tests/ui/dyn-compatibility/almost-supertrait-associated-type.stderr

@@ -15,6 +15,17 @@ LL |     fn transmute(&self, t: T) -> <Self as Super<NotActuallySuper>>::Assoc;
    |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...because method `transmute` references the `Self` type in its return type
    = help: consider moving `transmute` to another trait
 
+error: hi
+  --> $DIR/almost-supertrait-associated-type.rs:39:1
+   |
+LL | trait Mirror {
+   | ------------ built-in `dyn Mirror<Assoc = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Mirror for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0038]: the trait `Foo` is not dyn compatible
   --> $DIR/almost-supertrait-associated-type.rs:7:27
    |
@@ -50,6 +61,6 @@ LL |     fn transmute(&self, t: T) -> <Self as Super<NotActuallySuper>>::Assoc;
    = help: consider moving `transmute` to another trait
    = note: required for the cast from `&PhantomData<T>` to `&dyn Foo<T, U>`
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/higher-ranked/structually-relate-aliases.stderr

@@ -1,4 +1,5 @@
  WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [?1t, '^0.Named(DefId(0:15 ~ structually_relate_aliases[de75]::{impl#1}::'a), "'a")], def_id: DefId(0:5 ~ structually_relate_aliases[de75]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [?2t, '^0.Named(DefId(0:15 ~ structually_relate_aliases[de75]::{impl#1}::'a), "'a")], def_id: DefId(0:5 ~ structually_relate_aliases[de75]::ToUnit::Unit), .. }
 error[E0277]: the trait bound `for<'a> T: ToUnit<'a>` is not satisfied
   --> $DIR/structually-relate-aliases.rs:13:36
    |

tests/ui/impl-trait/where-allowed.stderr

@@ -378,6 +378,17 @@ LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
    = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
    = note: `#[deny(invalid_type_param_default)]` on by default
 
+error: hi
+  --> $DIR/where-allowed.rs:172:1
+   |
+LL | impl PartialEq<()> for impl Debug {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/cmp.rs:LL:COL
+   |
+   = note: built-in `dyn PartialEq<()>` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
   --> $DIR/where-allowed.rs:239:7
    |
@@ -431,7 +442,7 @@ LL | type InTypeAlias<R> = impl Debug;
    |
    = note: `InTypeAlias` must be used in combination with a concrete type within the same crate
 
-error: aborting due to 50 previous errors
+error: aborting due to 51 previous errors
 
 Some errors have detailed explanations: E0053, E0118, E0283, E0562, E0658, E0666.
 For more information about an error, try `rustc --explain E0053`.

tests/ui/issues/issue-20939.stderr

@@ -1,9 +1,20 @@
+error: hi
+  --> $DIR/issue-20939.rs:3:1
+   |
+LL | trait Foo {}
+   | --------- built-in `dyn Foo` implementation for this trait
+LL |
+LL | impl<'a> Foo for dyn Foo + 'a {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0371]: the object type `(dyn Foo + 'a)` automatically implements the trait `Foo`
   --> $DIR/issue-20939.rs:3:1
    |
 LL | impl<'a> Foo for dyn Foo + 'a {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn Foo + 'a)` automatically implements trait `Foo`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0371`.

tests/ui/issues/issue-30589.stderr

@@ -4,6 +4,17 @@ error[E0412]: cannot find type `DecoderError` in this scope
 LL | impl fmt::Display for DecoderError {
    |                       ^^^^^^^^^^^^ not found in this scope
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/issue-30589.rs:3:1
+   |
+LL | impl fmt::Display for DecoderError {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
+   |
+   = note: built-in `dyn std::fmt::Display` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/issues/issue-36836.stderr

@@ -4,6 +4,17 @@ error[E0412]: cannot find type `Bar` in this scope
 LL | impl<T> Foo for Bar<T> {}
    |                 ^^^ not found in this scope
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/issue-36836.rs:13:1
+   |
+LL | trait Foo {}
+   | --------- built-in `dyn Foo` implementation for this trait
+LL |
+LL | impl<T> Foo for Bar<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/lazy-type-alias/unconstrained-params-in-impl.stderr

@@ -4,6 +4,16 @@ error[E0207]: the type parameter `T` is not constrained by the impl trait, self
 LL | impl<T> NotInjective<T> {}
    |      ^ unconstrained type parameter
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/unconstrained-params-in-impl.rs:10:1
+   |
+LL | trait Discard { type Out; }
+   | ------------- built-in `dyn Discard<Out = _>` implementation for this trait
+LL | impl<T: ?Sized> Discard for T { type Out = (); }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0207`.

tests/ui/lint/lint-ctypes-fn.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/lint-ctypes-fn.rs:12:1
+   |
+LL | trait Mirror { type It: ?Sized; }
+   | ------------ built-in `dyn Mirror<It = _>` implementation for this trait
+LL |
+LL | impl<T: ?Sized> Mirror for T { type It = Self; }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: `extern` fn uses type `[u32]`, which is not FFI-safe
   --> $DIR/lint-ctypes-fn.rs:70:33
    |
@@ -184,5 +195,5 @@ LL | pub extern "C" fn used_generic5<T>() -> Vec<T> {
    = help: consider adding a `#[repr(C)]` or `#[repr(transparent)]` attribute to this struct
    = note: this struct has unspecified layout
 
-error: aborting due to 20 previous errors
+error: aborting due to 21 previous errors
 

tests/ui/lint/lint-ctypes.stderr

@@ -1,3 +1,13 @@
+error: hi
+  --> $DIR/lint-ctypes.rs:12:1
+   |
+LL | trait Mirror { type It: ?Sized; }
+   | ------------ built-in `dyn Mirror<It = _>` implementation for this trait
+LL | impl<T: ?Sized> Mirror for T { type It = Self; }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: `extern` block uses type `Foo`, which is not FFI-safe
   --> $DIR/lint-ctypes.rs:47:28
    |
@@ -258,5 +268,5 @@ LL |     pub static static_u128_array_type: [u128; 16];
    |
    = note: 128-bit integers don't currently have a known stable ABI
 
-error: aborting due to 27 previous errors
+error: aborting due to 28 previous errors
 

tests/ui/lint/recommend-literal.stderr

@@ -94,6 +94,16 @@ LL | impl Stuff for short {}
    |                not found in this scope
    |                help: perhaps you intended to use this type: `i16`
 
-error: aborting due to 9 previous errors
+error: hi
+  --> $DIR/recommend-literal.rs:40:1
+   |
+LL | trait Stuff {}
+   | ----------- built-in `dyn Stuff` implementation for this trait
+LL | impl Stuff for short {}
+   | ^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 10 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/lint/unaligned_references.current.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/unaligned_references.rs:62:5
+   |
+LL |     trait Mirror {
+   |     ------------ built-in `dyn Mirror<Assoc = _>` implementation for this trait
+...
+LL |     impl<T: ?Sized> Mirror for T {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0793]: reference to packed field is unaligned
   --> $DIR/unaligned_references.rs:32:13
    |
@@ -128,6 +139,6 @@ LL |         let _ref = &m2.1.a;
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
-error: aborting due to 13 previous errors
+error: aborting due to 14 previous errors
 
 For more information about this error, try `rustc --explain E0793`.

tests/ui/lint/unaligned_references.next.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/unaligned_references.rs:62:5
+   |
+LL |     trait Mirror {
+   |     ------------ built-in `dyn Mirror<Assoc = _>` implementation for this trait
+...
+LL |     impl<T: ?Sized> Mirror for T {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0793]: reference to packed field is unaligned
   --> $DIR/unaligned_references.rs:32:13
    |
@@ -128,6 +139,6 @@ LL |         let _ref = &m2.1.a;
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
-error: aborting due to 13 previous errors
+error: aborting due to 14 previous errors
 
 For more information about this error, try `rustc --explain E0793`.

tests/ui/methods/method-deref-to-same-trait-object-with-separate-params.stderr

@@ -7,6 +7,17 @@ LL | #![feature(unsized_locals, unsized_fn_params)]
    = note: see issue #48055 <https://github.com/rust-lang/rust/issues/48055> for more information
    = note: `#[warn(incomplete_features)]` on by default
 
+error: hi
+  --> $DIR/method-deref-to-same-trait-object-with-separate-params.rs:73:5
+   |
+LL |     pub trait NuisanceFoo {
+   |     --------------------- built-in `dyn NuisanceFoo` implementation for this trait
+...
+LL |     impl<T: ?Sized> NuisanceFoo for T {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0308]: mismatched types
   --> $DIR/method-deref-to-same-trait-object-with-separate-params.rs:89:24
    |
@@ -84,7 +95,7 @@ LL |     let _seetype: () = z;
    |                   |
    |                   expected due to this
 
-error: aborting due to 6 previous errors; 1 warning emitted
+error: aborting due to 7 previous errors; 1 warning emitted
 
 Some errors have detailed explanations: E0034, E0308.
 For more information about an error, try `rustc --explain E0034`.

tests/ui/mir/ice-mir-const-qualif-125837.stderr

@@ -24,6 +24,17 @@ help: add missing generic argument
 LL | impl<Item, D: Debug + Clone> Foo<Item> for D {
    |                                 ++++++
 
+error: hi
+  --> $DIR/ice-mir-const-qualif-125837.rs:8:1
+   |
+LL | trait Foo<Item> {}
+   | --------------- built-in `dyn Foo<{type error}>` implementation for this trait
+LL |
+LL | impl<Item, D: Debug + Clone> Foo for D {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0572]: return statement outside of function body
   --> $DIR/ice-mir-const-qualif-125837.rs:12:17
    |
@@ -35,7 +46,7 @@ LL | |
 LL | |     }
    | |_____- ...not the enclosing function body
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0107, E0407, E0572.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/mir/validate/validate-unsize-cast.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/validate-unsize-cast.rs:10:1
+   |
+LL | pub trait CastTo<U: ?Sized>: Unsize<U> {}
+   | -------------------------------------- built-in `dyn CastTo<_>` implementation for this trait
+...
+LL | impl<T: ?Sized, U: ?Sized> CastTo<U> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the trait bound `T: Unsize<U>` is not satisfied
   --> $DIR/validate-unsize-cast.rs:10:42
    |
@@ -15,6 +26,6 @@ help: consider further restricting type parameter `T` with unstable trait `Unsiz
 LL | impl<T: ?Sized + std::marker::Unsize<U>, U: ?Sized> CastTo<U> for T {}
    |                ++++++++++++++++++++++++
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/privacy/issue-111220-2-tuple-struct-fields-projection.stderr

@@ -1,9 +1,20 @@
+error: hi
+  --> $DIR/issue-111220-2-tuple-struct-fields-projection.rs:22:1
+   |
+LL | trait Trait<T> {
+   | -------------- built-in `dyn Trait<_>` implementation for this trait
+...
+LL | impl<T: Id> Trait<T> for <T as Id>::Assoc {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0603]: tuple struct constructor `A` is private
   --> $DIR/issue-111220-2-tuple-struct-fields-projection.rs:27:13
    |
 LL |         let Self(a) = self;
    |             ^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0603`.

tests/ui/recursion/issue-26548-recursion-via-normalize.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/issue-26548-recursion-via-normalize.rs:11:1
+   |
+LL | trait Mirror {
+   | ------------ built-in `dyn Mirror<It = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Mirror for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0391]: cycle detected when computing layout of `core::option::Option<S>`
    |
    = note: ...which requires computing layout of `S`...
@@ -6,6 +17,6 @@ error[E0391]: cycle detected when computing layout of `core::option::Option<S>`
    = note: cycle used when computing layout of `core::option::Option<<S as Mirror>::It>`
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0391`.

tests/ui/repr/repr-transparent.stderr

@@ -7,6 +7,16 @@ LL | struct MultipleNonZst(u8, u8);
    | |                     this field has non-zero size or requires alignment
    | needs at most one field with non-trivial size or alignment, but has 2
 
+error: hi
+  --> $DIR/repr-transparent.rs:29:1
+   |
+LL | trait Mirror { type It: ?Sized; }
+   | ------------ built-in `dyn Mirror<It = _>` implementation for this trait
+LL | impl<T: ?Sized> Mirror for T { type It = Self; }
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0690]: transparent struct needs at most one field with non-trivial size or alignment, but has 2
   --> $DIR/repr-transparent.rs:32:1
    |
@@ -98,7 +108,7 @@ LL |     u: u32,
 LL |     s: i32
    |     ------ this field has non-zero size or requires alignment
 
-error: aborting due to 11 previous errors
+error: aborting due to 12 previous errors
 
 Some errors have detailed explanations: E0084, E0690, E0731.
 For more information about an error, try `rustc --explain E0084`.

tests/ui/resolve/dont-compute-arg-names-for-non-fn.stderr

@@ -9,6 +9,19 @@ help: you might have meant to use the associated type
 LL | impl Foo for Self::Bar {}
    |              ++++++
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/dont-compute-arg-names-for-non-fn.rs:8:1
+   |
+LL | impl Foo for Bar {}
+   | ^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+  ::: $DIR/auxiliary/foreign-trait-with-assoc.rs:1:1
+   |
+LL | pub trait Foo {
+   | ------------- built-in `dyn Foo<Bar = _>` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/resolve/issue-3214.stderr

@@ -22,7 +22,18 @@ note: struct defined here, with 0 generic parameters
 LL |     struct Foo {
    |            ^^^
 
-error: aborting due to 2 previous errors
+error: hi
+  --> $DIR/issue-3214.rs:6:5
+   |
+LL |     impl<T> Drop for Foo<T> {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/ops/drop.rs:LL:COL
+   |
+   = note: built-in `dyn Drop` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 3 previous errors
 
 Some errors have detailed explanations: E0107, E0401.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/resolve/resolve-self-in-impl.stderr

@@ -28,6 +28,26 @@ LL | trait Tr<T = u8> {
    | ^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
+error: hi
+  --> $DIR/resolve-self-in-impl.rs:14:1
+   |
+LL | trait Tr<T = u8> {
+   | ---------------- built-in `dyn Tr<{type error}, A = _>` implementation for this trait
+...
+LL | impl Tr for Self {}
+   | ^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: hi
+  --> $DIR/resolve-self-in-impl.rs:15:1
+   |
+LL | trait Tr<T = u8> {
+   | ---------------- built-in `dyn Tr<{type error}, A = _>` implementation for this trait
+...
+LL | impl Tr for S<Self> {}
+   | ^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
 error: `Self` is not valid in the self type of an impl block
   --> $DIR/resolve-self-in-impl.rs:16:6
    |
@@ -52,6 +72,6 @@ LL | impl (Self, Self) {}
    |
    = note: replace `Self` with a different type
 
-error: aborting due to 6 previous errors
+error: aborting due to 8 previous errors
 
 For more information about this error, try `rustc --explain E0391`.

tests/ui/specialization/coherence/default-item-normalization-ambig-1.stderr

@@ -8,6 +8,17 @@ LL | #![feature(specialization)]
    = help: consider using `min_specialization` instead, which is more stable and complete
    = note: `#[warn(incomplete_features)]` on by default
 
+error: hi
+  --> $DIR/default-item-normalization-ambig-1.rs:19:1
+   |
+LL | trait Y {
+   | ------- built-in `dyn Y` implementation for this trait
+...
+LL | impl Y for <() as X>::U {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0119]: conflicting implementations of trait `Y` for type `<() as X>::U`
   --> $DIR/default-item-normalization-ambig-1.rs:20:1
    |
@@ -16,6 +27,15 @@ LL | impl Y for <() as X>::U {}
 LL | impl Y for <i32 as X>::U {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<() as X>::U`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: hi
+  --> $DIR/default-item-normalization-ambig-1.rs:20:1
+   |
+LL | trait Y {
+   | ------- built-in `dyn Y` implementation for this trait
+...
+LL | impl Y for <i32 as X>::U {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: aborting due to 3 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/specialization/issue-51892.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/issue-51892.rs:9:1
+   |
+LL | pub trait Trait {
+   | --------------- built-in `dyn Trait<Type = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Trait for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error: unconstrained generic constant
   --> $DIR/issue-51892.rs:14:17
    |
@@ -9,5 +20,5 @@ help: try adding a `where` bound
 LL |     type Type = [u8; std::mem::size_of::<<T as Trait>::Type>()] where [(); std::mem::size_of::<<T as Trait>::Type>()]:;
    |                                                                 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 

tests/ui/specialization/min_specialization/impl-on-nonexisting.stderr

@@ -4,6 +4,16 @@ error[E0412]: cannot find type `NonExistent` in this scope
 LL | impl Trait for NonExistent {}
    |                ^^^^^^^^^^^ not found in this scope
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/impl-on-nonexisting.rs:4:1
+   |
+LL | trait Trait {}
+   | ----------- built-in `dyn Trait` implementation for this trait
+LL | impl Trait for NonExistent {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0412`.

tests/ui/specialization/specialization-default-items-drop-coherence.current.stderr

@@ -7,6 +7,17 @@ LL | impl Overlap for u32 {
 LL | impl Overlap for <u32 as Default>::Id {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/specialization-default-items-drop-coherence.rs:26:1
+   |
+LL | trait Overlap {
+   | ------------- built-in `dyn Overlap<Assoc = _>` implementation for this trait
+...
+LL | impl Overlap for <u32 as Default>::Id {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/specialization/specialization-default-items-drop-coherence.next.stderr

@@ -7,6 +7,17 @@ LL | impl Overlap for u32 {
 LL | impl Overlap for <u32 as Default>::Id {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/specialization-default-items-drop-coherence.rs:26:1
+   |
+LL | trait Overlap {
+   | ------------- built-in `dyn Overlap<Assoc = _>` implementation for this trait
+...
+LL | impl Overlap for <u32 as Default>::Id {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/specialization/specialization-overlap-projection.stderr

@@ -25,6 +25,26 @@ LL | impl Foo for u32 {}
 LL | impl Foo for <u16 as Assoc>::Output {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
 
-error: aborting due to 2 previous errors; 1 warning emitted
+error: hi
+  --> $DIR/specialization-overlap-projection.rs:20:1
+   |
+LL | trait Foo {}
+   | --------- built-in `dyn Foo` implementation for this trait
+LL | impl Foo for u32 {}
+LL | impl Foo for <u8 as Assoc>::Output {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: hi
+  --> $DIR/specialization-overlap-projection.rs:22:1
+   |
+LL | trait Foo {}
+   | --------- built-in `dyn Foo` implementation for this trait
+...
+LL | impl Foo for <u16 as Assoc>::Output {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: aborting due to 4 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/suggestions/box-future-wrong-output.stderr

@@ -1,3 +1,13 @@
+error: hi
+  --> $DIR/box-future-wrong-output.rs:9:1
+   |
+LL | impl<T: ?Sized> FutureExt for T where T: Future {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+LL | trait FutureExt: Future {
+   | ----------------------- built-in `dyn FutureExt<Output = _>` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0308]: mismatched types
   --> $DIR/box-future-wrong-output.rs:20:39
    |
@@ -9,6 +19,6 @@ LL |     let _: BoxFuture<'static, bool> = async {}.boxed();
    = note: expected struct `Pin<Box<(dyn Future<Output = bool> + Send + 'static)>>`
               found struct `Pin<Box<dyn Future<Output = ()> + Send>>`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0308`.

tests/ui/suggestions/suggest-blanket-impl-local-trait.stderr

@@ -62,6 +62,17 @@ LL - impl<E> GenericTrait<E> for LocalTraitOne {}
 LL + impl<E, T: LocalTraitOne> GenericTrait<E> for T {}
    |
 
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:13:1
+   |
+LL | trait LocalTraitTwo { }
+   | ------------------- built-in `dyn LocalTraitTwo` implementation for this trait
+...
+LL | impl LocalTraitTwo for LocalTraitOne {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0782]: expected a type, found a trait
   --> $DIR/suggest-blanket-impl-local-trait.rs:18:23
    |
@@ -73,6 +84,15 @@ help: you can add the `dyn` keyword if you want a trait object
 LL | impl fmt::Display for dyn LocalTraitOne {
    |                       +++
 
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:18:1
+   |
+LL | impl fmt::Display for LocalTraitOne {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
+   |
+   = note: built-in `dyn std::fmt::Display` implementation for this trait
+
 error[E0782]: expected a type, found a trait
   --> $DIR/suggest-blanket-impl-local-trait.rs:26:23
    |
@@ -84,6 +104,42 @@ help: you can add the `dyn` keyword if you want a trait object
 LL | impl fmt::Display for dyn LocalTraitTwo + Send {
    |                       +++
 
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:26:1
+   |
+LL | impl fmt::Display for LocalTraitTwo + Send {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
+   |
+   = note: built-in `dyn std::fmt::Display` implementation for this trait
+
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:34:1
+   |
+LL | trait LocalTraitOne { }
+   | ------------------- built-in `dyn LocalTraitOne` implementation for this trait
+...
+LL | impl LocalTraitOne for fmt::Display {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:40:1
+   |
+LL | trait LocalTraitOne { }
+   | ------------------- built-in `dyn LocalTraitOne` implementation for this trait
+...
+LL | impl LocalTraitOne for fmt::Display + Send {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:46:1
+   |
+LL | trait GenericTrait<T> {}
+   | --------------------- built-in `dyn GenericTrait<_>` implementation for this trait
+...
+LL | impl<E> GenericTrait<E> for LocalTraitOne {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
 error[E0782]: expected a type, found a trait
   --> $DIR/suggest-blanket-impl-local-trait.rs:53:35
    |
@@ -100,6 +156,15 @@ LL - impl<T, E> GenericTraitTwo<E> for GenericTrait<T> {}
 LL + impl<T, E, U: GenericTrait<T>> GenericTraitTwo<E> for U {}
    |
 
-error: aborting due to 7 previous errors
+error: hi
+  --> $DIR/suggest-blanket-impl-local-trait.rs:53:1
+   |
+LL | trait GenericTraitTwo<T> {}
+   | ------------------------ built-in `dyn GenericTraitTwo<_>` implementation for this trait
+LL |
+LL | impl<T, E> GenericTraitTwo<E> for GenericTrait<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: aborting due to 14 previous errors
 
 For more information about this error, try `rustc --explain E0782`.

tests/ui/traits/associated_type_bound/116464-invalid-assoc-type-suggestion-in-trait-impl.stderr

@@ -127,7 +127,17 @@ note: struct defined here, with 1 generic parameter: `T`
 LL | struct Struct<T: Trait<u32, String>> {
    |        ^^^^^^ -
 
-error: aborting due to 9 previous errors
+error: hi
+  --> $DIR/116464-invalid-assoc-type-suggestion-in-trait-impl.rs:40:1
+   |
+LL | trait YetAnotherTrait {}
+   | --------------------- built-in `dyn YetAnotherTrait` implementation for this trait
+LL | impl<T: Trait<u32, Assoc=String>, U> YetAnotherTrait for Struct<T, U> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0107, E0207.
 For more information about an error, try `rustc --explain E0107`.

tests/ui/traits/deny-builtin-object-impl.current.stderr

@@ -4,6 +4,17 @@ error[E0322]: explicit impls for the `NotImplYesObject` trait are not permitted
 LL | impl NotImplYesObject for () {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of `NotImplYesObject` not allowed
 
+error: hi
+  --> $DIR/deny-builtin-object-impl.rs:24:1
+   |
+LL | trait YesImplNotObject2 {}
+   | ----------------------- built-in `dyn YesImplNotObject2` implementation for this trait
+...
+LL | impl YesImplNotObject2 for dyn YesImplNotObject2 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the trait bound `dyn NotImplNotObject: NotImplNotObject` is not satisfied
   --> $DIR/deny-builtin-object-impl.rs:37:32
    |
@@ -38,7 +49,7 @@ note: required by a bound in `test_yes_impl_not_object`
 LL | fn test_yes_impl_not_object<T: YesImplNotObject + ?Sized>() {}
    |                                ^^^^^^^^^^^^^^^^ required by this bound in `test_yes_impl_not_object`
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0277, E0322.
 For more information about an error, try `rustc --explain E0277`.

tests/ui/traits/deny-builtin-object-impl.next.stderr

@@ -4,6 +4,17 @@ error[E0322]: explicit impls for the `NotImplYesObject` trait are not permitted
 LL | impl NotImplYesObject for () {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ impl of `NotImplYesObject` not allowed
 
+error: hi
+  --> $DIR/deny-builtin-object-impl.rs:24:1
+   |
+LL | trait YesImplNotObject2 {}
+   | ----------------------- built-in `dyn YesImplNotObject2` implementation for this trait
+...
+LL | impl YesImplNotObject2 for dyn YesImplNotObject2 {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the trait bound `dyn NotImplNotObject: NotImplNotObject` is not satisfied
   --> $DIR/deny-builtin-object-impl.rs:37:32
    |
@@ -38,7 +49,7 @@ note: required by a bound in `test_yes_impl_not_object`
 LL | fn test_yes_impl_not_object<T: YesImplNotObject + ?Sized>() {}
    |                                ^^^^^^^^^^^^^^^^ required by this bound in `test_yes_impl_not_object`
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0277, E0322.
 For more information about an error, try `rustc --explain E0277`.

tests/ui/traits/impl-for-module.stderr

@@ -7,6 +7,17 @@ LL | trait A {
 LL | impl A for a {
    |            ^ help: a trait with a similar name exists: `A`
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/impl-for-module.rs:7:1
+   |
+LL | trait A {
+   | ------- built-in `dyn A` implementation for this trait
+...
+LL | impl A for a {
+   | ^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0573`.

tests/ui/traits/issue-33140-hack-boundaries.stderr

@@ -30,6 +30,17 @@ LL | impl Trait3<dyn Sync> for dyn Send {}
 LL | impl Trait3<dyn Sync> for dyn Send {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Send + 'static)`
 
+error: hi
+  --> $DIR/issue-33140-hack-boundaries.rs:38:1
+   |
+LL | trait Trait4a {}
+   | ------------- built-in `dyn Trait4a` implementation for this trait
+LL |
+LL | impl<T: ?Sized> Trait4a for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0119]: conflicting implementations of trait `Trait4a` for type `(dyn Send + 'static)`
   --> $DIR/issue-33140-hack-boundaries.rs:39:1
    |
@@ -70,7 +81,7 @@ LL | impl Trait5 for dyn Send {}
 LL | impl Trait5 for dyn Send where u32: Copy {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Send + 'static)`
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors
 
 Some errors have detailed explanations: E0119, E0751.
 For more information about an error, try `rustc --explain E0119`.

tests/ui/traits/issue-78372.stderr

@@ -56,6 +56,17 @@ LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
    = help: add `#![feature(dispatch_from_dyn)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
+error: hi
+  --> $DIR/issue-78372.rs:3:1
+   |
+LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+  --> $SRC_DIR/core/src/ops/unsize.rs:LL:COL
+   |
+   = note: built-in `dyn DispatchFromDyn<Smaht<{type error}, {type error}>>` implementation for this trait
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0307]: invalid `self` parameter type: `Smaht<Self, T>`
   --> $DIR/issue-78372.rs:9:18
    |
@@ -71,7 +82,7 @@ error[E0377]: the trait `DispatchFromDyn` may only be implemented for a coercion
 LL | impl<T> DispatchFromDyn<Smaht<U, MISC>> for T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 7 previous errors
+error: aborting due to 8 previous errors
 
 Some errors have detailed explanations: E0307, E0377, E0412, E0658.
 For more information about an error, try `rustc --explain E0307`.

tests/ui/traits/next-solver/alias-relate/alias_eq_substs_eq_not_intercrate.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/alias_eq_substs_eq_not_intercrate.rs:13:1
+   |
+LL | trait Overlaps<T> {}
+   | ----------------- built-in `dyn Overlaps<Box<_>>` implementation for this trait
+LL |
+LL | impl<T: TraitB> Overlaps<Box<T>> for <T as TraitB>::Assoc {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0119]: conflicting implementations of trait `Overlaps<Box<_>>` for type `<_ as TraitB>::Assoc`
   --> $DIR/alias_eq_substs_eq_not_intercrate.rs:14:1
    |
@@ -8,6 +19,15 @@ LL | impl<U: TraitB> Overlaps<U> for <U as TraitB>::Assoc {}
    |
    = note: downstream crates may implement trait `TraitB` for type `std::boxed::Box<_>`
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/alias_eq_substs_eq_not_intercrate.rs:14:1
+   |
+LL | trait Overlaps<T> {}
+   | ----------------- built-in `dyn Overlaps<_>` implementation for this trait
+...
+LL | impl<U: TraitB> Overlaps<U> for <U as TraitB>::Assoc {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/traits/next-solver/coherence/trait_ref_is_knowable-norm-overflow.stderr

@@ -10,6 +10,17 @@ LL | impl Trait for <LocalTy as Overflow>::Assoc {}
    = note: overflow evaluating the requirement `_ == <LocalTy as Overflow>::Assoc`
    = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`trait_ref_is_knowable_norm_overflow`)
 
-error: aborting due to 1 previous error
+error: hi
+  --> $DIR/trait_ref_is_knowable-norm-overflow.rs:20:1
+   |
+LL | trait Trait {}
+   | ----------- built-in `dyn Trait` implementation for this trait
+...
+LL | impl Trait for <LocalTy as Overflow>::Assoc {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0119`.

tests/ui/traits/next-solver/cycles/coinduction/incompleteness-unstable-result.with.stderr

@@ -1,3 +1,48 @@
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:25:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, u8>` implementation for this trait
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, u8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:26:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, i8>` implementation for this trait
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, u8> for T {}
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, i8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:27:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, i16>` implementation for this trait
+...
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, i16> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:30:1
+   |
+LL | trait ImplGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------- built-in `dyn ImplGuidance<u32, u8>` implementation for this trait
+LL | impl<T: ?Sized> ImplGuidance<u32, u8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:31:1
+   |
+LL | trait ImplGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------- built-in `dyn ImplGuidance<i32, i8>` implementation for this trait
+LL | impl<T: ?Sized> ImplGuidance<u32, u8> for T {}
+LL | impl<T: ?Sized> ImplGuidance<i32, i8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
 error[E0277]: the trait bound `A<X>: Trait<_, _, _>` is not satisfied
   --> $DIR/incompleteness-unstable-result.rs:65:19
    |
@@ -21,6 +66,6 @@ note: required by a bound in `impls_trait`
 LL | fn impls_trait<T: ?Sized + Trait<U, V, D>, U: ?Sized, V: ?Sized, D: ?Sized>() {}
    |                            ^^^^^^^^^^^^^^ required by this bound in `impls_trait`
 
-error: aborting due to 1 previous error
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/traits/next-solver/cycles/coinduction/incompleteness-unstable-result.without.stderr

@@ -1,3 +1,48 @@
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:25:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, u8>` implementation for this trait
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, u8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:26:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, i8>` implementation for this trait
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, u8> for T {}
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, i8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:27:1
+   |
+LL | trait IncompleteGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------------- built-in `dyn IncompleteGuidance<_, i16>` implementation for this trait
+...
+LL | impl<T: ?Sized, U: ?Sized + 'static> IncompleteGuidance<U, i16> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:30:1
+   |
+LL | trait ImplGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------- built-in `dyn ImplGuidance<u32, u8>` implementation for this trait
+LL | impl<T: ?Sized> ImplGuidance<u32, u8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
+error: hi
+  --> $DIR/incompleteness-unstable-result.rs:31:1
+   |
+LL | trait ImplGuidance<T: ?Sized, V: ?Sized> {}
+   | ---------------------------------------- built-in `dyn ImplGuidance<i32, i8>` implementation for this trait
+LL | impl<T: ?Sized> ImplGuidance<u32, u8> for T {}
+LL | impl<T: ?Sized> ImplGuidance<i32, i8> for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+
 error[E0277]: the trait bound `A<X>: Trait<_, _, _>` is not satisfied
   --> $DIR/incompleteness-unstable-result.rs:65:19
    |
@@ -21,6 +66,6 @@ note: required by a bound in `impls_trait`
 LL | fn impls_trait<T: ?Sized + Trait<U, V, D>, U: ?Sized, V: ?Sized, D: ?Sized>() {}
    |                            ^^^^^^^^^^^^^^ required by this bound in `impls_trait`
 
-error: aborting due to 1 previous error
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/traits/next-solver/issue-118950-root-region.stderr

@@ -26,6 +26,7 @@ LL | trait ToUnit<'a> {
    | ^^^^^^^^^^^^^^^^
 
  WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a), "'a"), ?1t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a), "'a"), ?2t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc), .. }
 error[E0277]: the trait bound `for<'a> *const T: ToUnit<'a>` is not satisfied
   --> $DIR/issue-118950-root-region.rs:19:9
    |

tests/ui/traits/object/with-self-in-projection-output-bad.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/with-self-in-projection-output-bad.rs:27:1
+   |
+LL | trait ConstI32 {
+   | -------------- built-in `dyn ConstI32<Out = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> ConstI32 for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0191]: the value of the associated type `Output` in `Base` must be specified
   --> $DIR/with-self-in-projection-output-bad.rs:45:21
    |
@@ -16,6 +27,6 @@ LL |     type Output;
 LL |     let _y: Box<dyn NormalizableHelper<Target=i32>> = Box::new(2u32);
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: specify the associated type: `NormalizableHelper<Target=i32, Output = Type>`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0191`.

tests/ui/traits/trait-upcasting/cyclic-trait-resolution.stderr

@@ -12,20 +12,6 @@ LL | trait A: B + A {}
    | ^^^^^^^^^^^^^^^^^
    = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
 
-error[E0391]: cycle detected when computing the implied predicates of `A`
-  --> $DIR/cyclic-trait-resolution.rs:1:14
-   |
-LL | trait A: B + A {}
-   |              ^
-   |
-   = note: ...which immediately requires computing the implied predicates of `A` again
-note: cycle used when checking that `<impl at $DIR/cyclic-trait-resolution.rs:7:1: 7:14>` is well-formed
-  --> $DIR/cyclic-trait-resolution.rs:7:1
-   |
-LL | impl A for () {}
-   | ^^^^^^^^^^^^^
-   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
-
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0391`.

tests/ui/traits/trait-upcasting/illegal-upcast-from-impl.current.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/illegal-upcast-from-impl.rs:11:1
+   |
+LL | trait Super {
+   | ----------- built-in `dyn Super<Assoc = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Super for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0308]: mismatched types
   --> $DIR/illegal-upcast-from-impl.rs:15:66
    |
@@ -9,6 +20,6 @@ LL | fn illegal(x: &dyn Sub<Assoc = ()>) -> &dyn Super<Assoc = i32> { x }
    = note: expected reference `&dyn Super<Assoc = i32>`
               found reference `&dyn Sub<Assoc = ()>`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0308`.

tests/ui/traits/trait-upcasting/illegal-upcast-from-impl.next.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/illegal-upcast-from-impl.rs:11:1
+   |
+LL | trait Super {
+   | ----------- built-in `dyn Super<Assoc = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> Super for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0308]: mismatched types
   --> $DIR/illegal-upcast-from-impl.rs:15:66
    |
@@ -9,6 +20,6 @@ LL | fn illegal(x: &dyn Sub<Assoc = ()>) -> &dyn Super<Assoc = i32> { x }
    = note: expected reference `&dyn Super<Assoc = i32>`
               found reference `&dyn Sub<Assoc = ()>`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0308`.

tests/ui/traits/trivial_impl_sized.stderr

@@ -21,6 +21,17 @@ note: the lint level is defined here
 LL | #[deny(dead_code)]
    |        ^^^^^^^^^
 
+error: hi
+  --> $DIR/trivial_impl_sized.rs:39:1
+   |
+LL | trait Trait {
+   | ----------- built-in `dyn Trait` implementation for this trait
+...
+LL | impl<T: ?Sized> Trait for T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0046]: not all trait items implemented, missing: `foo`
   --> $DIR/trivial_impl_sized.rs:39:1
    |
@@ -32,6 +43,6 @@ LL |   }
 LL |   impl<T: ?Sized> Trait for T {}
    |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `foo` in implementation
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0046`.

tests/ui/unsized/issue-71659.current.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/issue-71659.rs:13:1
+   |
+LL | pub trait CastTo<T: ?Sized>: Unsize<T> {
+   | -------------------------------------- built-in `dyn CastTo<_>` implementation for this trait
+...
+LL | impl<T: ?Sized, U: ?Sized + Unsize<T>> CastTo<T> for U {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the trait bound `dyn Foo: CastTo<[i32]>` is not satisfied
   --> $DIR/issue-71659.rs:34:15
    |
@@ -13,6 +24,6 @@ LL |     where
 LL |         Self: CastTo<T>,
    |               ^^^^^^^^^ required by this bound in `Cast::cast`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/unsized/issue-71659.next.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/issue-71659.rs:13:1
+   |
+LL | pub trait CastTo<T: ?Sized>: Unsize<T> {
+   | -------------------------------------- built-in `dyn CastTo<_>` implementation for this trait
+...
+LL | impl<T: ?Sized, U: ?Sized + Unsize<T>> CastTo<T> for U {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the trait bound `dyn Foo: CastTo<[i32]>` is not satisfied
   --> $DIR/issue-71659.rs:34:15
    |
@@ -13,6 +24,6 @@ LL |     where
 LL |         Self: CastTo<T>,
    |               ^^^^^^^^^ required by this bound in `Cast::cast`
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/wf/wf-normalization-sized.next.stderr

@@ -1,3 +1,14 @@
+error: hi
+  --> $DIR/wf-normalization-sized.rs:15:1
+   |
+LL | trait WellUnformed {
+   | ------------------ built-in `dyn WellUnformed<RequestNormalize = _>` implementation for this trait
+...
+LL | impl<T: ?Sized> WellUnformed for T {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ overlaps with this blanket impl
+   |
+   = note: `#[forbid(dyn_overlap)]` on by default
+
 error[E0277]: the size for values of type `[[[[[u8]]]]]` cannot be known at compilation time
   --> $DIR/wf-normalization-sized.rs:19:11
    |
@@ -17,6 +28,6 @@ LL | const _: <Vec<str> as WellUnformed>::RequestNormalize = ();
 note: required by an implicit `Sized` bound in `Vec`
   --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.