implied_bounds: clarify our assumptions

compiler/rustc_middle/src/query/mod.rs

@@ -765,6 +765,14 @@ rustc_queries! {
         desc { |tcx| "processing `{}`", tcx.def_path_str(key.to_def_id()) }
     }
 
+    /// Returns the types assumed to be well formed while "inside" of the given item.
+    ///
+    /// Note that we've liberated the late bound regions of function signatures, so
+    /// this can not be used to check whether these types are well formed.
+    query assumed_wf_types(key: DefId) -> &'tcx ty::List<Ty<'tcx>> {
+        desc { |tcx| "computing the implied bounds of {}", tcx.def_path_str(key) }
+    }
+
     /// Computes the signature of the function.
     query fn_sig(key: DefId) -> ty::PolyFnSig<'tcx> {
         desc { |tcx| "computing function signature of `{}`", tcx.def_path_str(key) }

compiler/rustc_ty_utils/src/implied_bounds.rs

@@ -0,0 +1,60 @@
+use crate::rustc_middle::ty::DefIdTree;
+use rustc_hir::{def::DefKind, def_id::DefId};
+use rustc_middle::ty::{self, Ty, TyCtxt};
+
+pub fn provide(providers: &mut ty::query::Providers) {
+    *providers = ty::query::Providers { assumed_wf_types, ..*providers };
+}
+
+fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx ty::List<Ty<'tcx>> {
+    match tcx.def_kind(def_id) {
+        DefKind::Fn => {
+            let sig = tcx.fn_sig(def_id);
+            let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
+            liberated_sig.inputs_and_output
+        }
+        DefKind::AssocFn => {
+            let sig = tcx.fn_sig(def_id);
+            let liberated_sig = tcx.liberate_late_bound_regions(def_id, sig);
+            let mut assumed_wf_types: Vec<_> =
+                tcx.assumed_wf_types(tcx.parent(def_id)).as_slice().into();
+            assumed_wf_types.extend(liberated_sig.inputs_and_output);
+            tcx.intern_type_list(&assumed_wf_types)
+        }
+        DefKind::Impl => match tcx.impl_trait_ref(def_id) {
+            Some(trait_ref) => {
+                let types: Vec<_> = trait_ref.substs.types().collect();
+                tcx.intern_type_list(&types)
+            }
+            // Only the impl self type
+            None => tcx.intern_type_list(&[tcx.type_of(def_id)]),
+        },
+        DefKind::AssocConst | DefKind::AssocTy => tcx.assumed_wf_types(tcx.parent(def_id)),
+        DefKind::Mod
+        | DefKind::Struct
+        | DefKind::Union
+        | DefKind::Enum
+        | DefKind::Variant
+        | DefKind::Trait
+        | DefKind::TyAlias
+        | DefKind::ForeignTy
+        | DefKind::TraitAlias
+        | DefKind::TyParam
+        | DefKind::Const
+        | DefKind::ConstParam
+        | DefKind::Static(_)
+        | DefKind::Ctor(_, _)
+        | DefKind::Macro(_)
+        | DefKind::ExternCrate
+        | DefKind::Use
+        | DefKind::ForeignMod
+        | DefKind::AnonConst
+        | DefKind::InlineConst
+        | DefKind::OpaqueTy
+        | DefKind::Field
+        | DefKind::LifetimeParam
+        | DefKind::GlobalAsm
+        | DefKind::Closure
+        | DefKind::Generator => ty::List::empty(),
+    }
+}

compiler/rustc_ty_utils/src/lib.rs

@@ -21,6 +21,7 @@ use rustc_middle::ty::query::Providers;
 mod assoc;
 mod common_traits;
 mod consts;
+mod implied_bounds;
 pub mod instance;
 mod needs_drop;
 pub mod representability;
@@ -30,6 +31,7 @@ pub fn provide(providers: &mut Providers) {
     assoc::provide(providers);
     common_traits::provide(providers);
     consts::provide(providers);
+    implied_bounds::provide(providers);
     needs_drop::provide(providers);
     ty::provide(providers);
     instance::provide(providers);

compiler/rustc_typeck/src/check/compare_method.rs

@@ -1,6 +1,5 @@
 use super::potentially_plural_count;
 use crate::check::regionck::OutlivesEnvironmentExt;
-use crate::check::wfcheck;
 use crate::errors::LifetimesOrBoundsMismatchOnTrait;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticId, ErrorGuaranteed};
@@ -1445,14 +1444,24 @@ pub fn check_type_bounds<'tcx>(
     };
     debug!(?normalize_param_env);
 
+    let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local());
     let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
     let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs);
 
     tcx.infer_ctxt().enter(move |infcx| {
         let ocx = ObligationCtxt::new(&infcx);
 
+        let assumed_wf_types = tcx.assumed_wf_types(impl_ty.def_id);
+        let mut implied_bounds = FxHashSet::default();
+        let cause = ObligationCause::misc(impl_ty_span, impl_ty_hir_id);
+        for ty in assumed_wf_types {
+            implied_bounds.insert(ty);
+            let normalized = ocx.normalize(cause.clone(), param_env, ty);
+            implied_bounds.insert(normalized);
+        }
+        let implied_bounds = implied_bounds;
+
         let mut selcx = traits::SelectionContext::new(&infcx);
-        let impl_ty_hir_id = tcx.hir().local_def_id_to_hir_id(impl_ty.def_id.expect_local());
         let normalize_cause = ObligationCause::new(
             impl_ty_span,
             impl_ty_hir_id,
@@ -1508,15 +1517,6 @@ pub fn check_type_bounds<'tcx>(
 
         // Finally, resolve all regions. This catches wily misuses of
         // lifetime parameters.
-        let implied_bounds = match impl_ty.container {
-            ty::TraitContainer => FxHashSet::default(),
-            ty::ImplContainer => wfcheck::impl_implied_bounds(
-                tcx,
-                param_env,
-                container_id.expect_local(),
-                impl_ty_span,
-            ),
-        };
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
         outlives_environment.add_implied_bounds(&infcx, implied_bounds, impl_ty_hir_id);
         infcx.check_region_obligations_and_report_errors(

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -10,7 +10,6 @@ use rustc_hir::ItemKind;
 use rustc_infer::infer::outlives::env::{OutlivesEnvironment, RegionBoundPairs};
 use rustc_infer::infer::outlives::obligations::TypeOutlives;
 use rustc_infer::infer::{self, InferCtxt, TyCtxtInferExt};
-use rustc_infer::traits::Normalized;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts, Subst};
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
@@ -24,8 +23,6 @@ use rustc_span::{Span, DUMMY_SP};
 use rustc_trait_selection::autoderef::Autoderef;
 use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
-use rustc_trait_selection::traits::query::normalize::AtExt;
-use rustc_trait_selection::traits::query::NoSolution;
 use rustc_trait_selection::traits::{
     self, ObligationCause, ObligationCauseCode, ObligationCtxt, WellFormedLoc,
 };
@@ -86,18 +83,29 @@ pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
     body_def_id: LocalDefId,
     f: F,
 ) where
-    F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>) -> FxHashSet<Ty<'tcx>>,
+    F: for<'a> FnOnce(&WfCheckingCtxt<'a, 'tcx>),
 {
     let param_env = tcx.param_env(body_def_id);
     let body_id = tcx.hir().local_def_id_to_hir_id(body_def_id);
     tcx.infer_ctxt().enter(|ref infcx| {
         let ocx = ObligationCtxt::new(infcx);
+
+        let assumed_wf_types = tcx.assumed_wf_types(body_def_id);
+        let mut implied_bounds = FxHashSet::default();
+        let cause = ObligationCause::misc(span, body_id);
+        for ty in assumed_wf_types {
+            implied_bounds.insert(ty);
+            let normalized = ocx.normalize(cause.clone(), param_env, ty);
+            implied_bounds.insert(normalized);
+        }
+        let implied_bounds = implied_bounds;
+
         let mut wfcx = WfCheckingCtxt { ocx, span, body_id, param_env };
 
         if !tcx.features().trivial_bounds {
             wfcx.check_false_global_bounds()
         }
-        let wf_tys = f(&mut wfcx);
+        f(&mut wfcx);
         let errors = wfcx.select_all_or_error();
         if !errors.is_empty() {
             infcx.report_fulfillment_errors(&errors, None, false);
@@ -105,7 +113,7 @@ pub(super) fn enter_wf_checking_ctxt<'tcx, F>(
         }
 
         let mut outlives_environment = OutlivesEnvironment::new(param_env);
-        outlives_environment.add_implied_bounds(infcx, wf_tys, body_id);
+        outlives_environment.add_implied_bounds(infcx, implied_bounds, body_id);
         infcx.check_region_obligations_and_report_errors(body_def_id, &outlives_environment);
     })
 }
@@ -976,15 +984,9 @@ fn check_associated_item(
     enter_wf_checking_ctxt(tcx, span, item_id, |wfcx| {
         let item = tcx.associated_item(item_id);
 
-        let (mut implied_bounds, self_ty) = match item.container {
+        let self_ty = match item.container {
-            ty::TraitContainer => (FxHashSet::default(), tcx.types.self_param),
+            ty::TraitContainer => tcx.types.self_param,
-            ty::ImplContainer => {
+            ty::ImplContainer => tcx.type_of(item.container_id(tcx)),
-                let def_id = item.container_id(tcx);
-                (
-                    impl_implied_bounds(tcx, wfcx.param_env, def_id.expect_local(), span),
-                    tcx.type_of(def_id),
-                )
-            }
         };
 
         match item.kind {
@@ -1002,7 +1004,6 @@ fn check_associated_item(
                     sig,
                     hir_sig.decl,
                     item.def_id.expect_local(),
-                    &mut implied_bounds,
                 );
                 check_method_receiver(wfcx, hir_sig, item, self_ty);
             }
@@ -1017,8 +1018,6 @@ fn check_associated_item(
                 }
             }
         }
-
-        implied_bounds
     })
 }
 
@@ -1118,9 +1117,6 @@ fn check_type_defn<'tcx, F>(
         }
 
         check_where_clauses(wfcx, item.span, item.def_id);
-
-        // No implied bounds in a struct definition.
-        FxHashSet::default()
     });
 }
 
@@ -1144,9 +1140,7 @@ fn check_trait(tcx: TyCtxt<'_>, item: &hir::Item<'_>) {
     }
 
     enter_wf_checking_ctxt(tcx, item.span, item.def_id, |wfcx| {
-        check_where_clauses(wfcx, item.span, item.def_id);
+        check_where_clauses(wfcx, item.span, item.def_id)
-
-        FxHashSet::default()
     });
 
     // Only check traits, don't check trait aliases
@@ -1186,9 +1180,7 @@ fn check_item_fn(
 ) {
     enter_wf_checking_ctxt(tcx, span, def_id, |wfcx| {
         let sig = tcx.fn_sig(def_id);
-        let mut implied_bounds = FxHashSet::default();
+        check_fn_or_method(wfcx, ident.span, sig, decl, def_id);
-        check_fn_or_method(wfcx, ident.span, sig, decl, def_id, &mut implied_bounds);
-        implied_bounds
     })
 }
 
@@ -1231,9 +1223,6 @@ fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_fo
                 tcx.require_lang_item(LangItem::Sync, Some(ty_span)),
             );
         }
-
-        // No implied bounds in a const, etc.
-        FxHashSet::default()
     });
 }
 
@@ -1284,8 +1273,6 @@ fn check_impl<'tcx>(
         }
 
         check_where_clauses(wfcx, item.span, item.def_id);
-
-        impl_implied_bounds(tcx, wfcx.param_env, item.def_id, item.span)
     });
 }
 
@@ -1479,7 +1466,6 @@ fn check_fn_or_method<'tcx>(
     sig: ty::PolyFnSig<'tcx>,
     hir_decl: &hir::FnDecl<'_>,
     def_id: LocalDefId,
-    implied_bounds: &mut FxHashSet<Ty<'tcx>>,
 ) {
     let tcx = wfcx.tcx();
     let sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
@@ -1521,15 +1507,8 @@ fn check_fn_or_method<'tcx>(
         );
     }
 
-    implied_bounds.extend(sig.inputs());
-
     wfcx.register_wf_obligation(hir_decl.output.span(), None, sig.output().into());
 
-    // FIXME(#27579) return types should not be implied bounds
-    implied_bounds.insert(sig.output());
-
-    debug!(?implied_bounds);
-
     check_where_clauses(wfcx, span, def_id);
 }
 
@@ -1924,40 +1903,6 @@ impl<'a, 'tcx> WfCheckingCtxt<'a, 'tcx> {
     }
 }
 
-pub fn impl_implied_bounds<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-    impl_def_id: LocalDefId,
-    span: Span,
-) -> FxHashSet<Ty<'tcx>> {
-    // We completely ignore any obligations caused by normalizing the types
-    // we assume to be well formed. Considering that the user of the implied
-    // bounds will also normalize them, we leave it to them to emit errors
-    // which should result in better causes and spans.
-    tcx.infer_ctxt().enter(|infcx| {
-        let cause = ObligationCause::misc(span, tcx.hir().local_def_id_to_hir_id(impl_def_id));
-        match tcx.impl_trait_ref(impl_def_id) {
-            Some(trait_ref) => {
-                // Trait impl: take implied bounds from all types that
-                // appear in the trait reference.
-                match infcx.at(&cause, param_env).normalize(trait_ref) {
-                    Ok(Normalized { value, obligations: _ }) => value.substs.types().collect(),
-                    Err(NoSolution) => FxHashSet::default(),
-                }
-            }
-
-            None => {
-                // Inherent impl: take implied bounds from the `self` type.
-                let self_ty = tcx.type_of(impl_def_id);
-                match infcx.at(&cause, param_env).normalize(self_ty) {
-                    Ok(Normalized { value, obligations: _ }) => FxHashSet::from_iter([value]),
-                    Err(NoSolution) => FxHashSet::default(),
-                }
-            }
-        }
-    })
-}
-
 fn error_392(
     tcx: TyCtxt<'_>,
     span: Span,

compiler/rustc_typeck/src/impl_wf_check/min_specialization.rs

@@ -66,26 +66,25 @@
 //! on traits with methods can.
 
 use crate::check::regionck::OutlivesEnvironmentExt;
-use crate::check::wfcheck::impl_implied_bounds;
 use crate::constrained_generic_params as cgp;
 use crate::errors::SubstsOnOverriddenImpl;
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
-use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
+use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::specialization_graph::Node;
+use rustc_infer::traits::ObligationCause;
 use rustc_middle::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
 use rustc_span::Span;
-use rustc_trait_selection::traits::{self, translate_substs, wf};
+use rustc_trait_selection::traits::error_reporting::InferCtxtExt;
+use rustc_trait_selection::traits::{self, translate_substs, wf, ObligationCtxt};
 
 pub(super) fn check_min_specialization(tcx: TyCtxt<'_>, impl_def_id: LocalDefId) {
     if let Some(node) = parent_specialization_node(tcx, impl_def_id) {
-        tcx.infer_ctxt().enter(|infcx| {
+        check_always_applicable(tcx, impl_def_id, node);
-            check_always_applicable(&infcx, impl_def_id, node);
-        });
     }
 }
 
@@ -105,16 +104,14 @@ fn parent_specialization_node(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId) -> Opti
 }
 
 /// Check that `impl1` is a sound specialization
-fn check_always_applicable(infcx: &InferCtxt<'_, '_>, impl1_def_id: LocalDefId, impl2_node: Node) {
+fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node) {
-    if let Some((impl1_substs, impl2_substs)) = get_impl_substs(infcx, impl1_def_id, impl2_node) {
+    if let Some((impl1_substs, impl2_substs)) = get_impl_substs(tcx, impl1_def_id, impl2_node) {
         let impl2_def_id = impl2_node.def_id();
         debug!(
             "check_always_applicable(\nimpl1_def_id={:?},\nimpl2_def_id={:?},\nimpl2_substs={:?}\n)",
             impl1_def_id, impl2_def_id, impl2_substs
         );
 
-        let tcx = infcx.tcx;
-
         let parent_substs = if impl2_node.is_from_trait() {
             impl2_substs.to_vec()
         } else {
@@ -124,7 +121,7 @@ fn check_always_applicable(infcx: &InferCtxt<'_, '_>, impl1_def_id: LocalDefId,
         let span = tcx.def_span(impl1_def_id);
         check_static_lifetimes(tcx, &parent_substs, span);
         check_duplicate_params(tcx, impl1_substs, &parent_substs, span);
-        check_predicates(infcx, impl1_def_id, impl1_substs, impl2_node, impl2_substs, span);
+        check_predicates(tcx, impl1_def_id, impl1_substs, impl2_node, impl2_substs, span);
     }
 }
 
@@ -139,25 +136,37 @@ fn check_always_applicable(infcx: &InferCtxt<'_, '_>, impl1_def_id: LocalDefId,
 ///
 /// Would return `S1 = [C]` and `S2 = [Vec<C>, C]`.
 fn get_impl_substs<'tcx>(
-    infcx: &InferCtxt<'_, 'tcx>,
+    tcx: TyCtxt<'tcx>,
     impl1_def_id: LocalDefId,
     impl2_node: Node,
 ) -> Option<(SubstsRef<'tcx>, SubstsRef<'tcx>)> {
-    let tcx = infcx.tcx;
+    tcx.infer_ctxt().enter(|ref infcx| {
+        let ocx = ObligationCtxt::new(infcx);
         let param_env = tcx.param_env(impl1_def_id);
+        let impl1_hir_id = tcx.hir().local_def_id_to_hir_id(impl1_def_id);
+
+        let assumed_wf_types = tcx.assumed_wf_types(impl1_def_id);
+        let mut implied_bounds = FxHashSet::default();
+        let cause = ObligationCause::misc(tcx.def_span(impl1_def_id), impl1_hir_id);
+        for ty in assumed_wf_types {
+            implied_bounds.insert(ty);
+            let normalized = ocx.normalize(cause.clone(), param_env, ty);
+            implied_bounds.insert(normalized);
+        }
+        let implied_bounds = implied_bounds;
 
         let impl1_substs = InternalSubsts::identity_for_item(tcx, impl1_def_id.to_def_id());
         let impl2_substs =
             translate_substs(infcx, param_env, impl1_def_id.to_def_id(), impl1_substs, impl2_node);
 
+        let errors = ocx.select_all_or_error();
+        if !errors.is_empty() {
+            ocx.infcx.report_fulfillment_errors(&errors, None, false);
+            return None;
+        }
+
         let mut outlives_env = OutlivesEnvironment::new(param_env);
-    let implied_bounds =
+        outlives_env.add_implied_bounds(infcx, implied_bounds, impl1_hir_id);
-        impl_implied_bounds(infcx.tcx, param_env, impl1_def_id, tcx.def_span(impl1_def_id));
-    outlives_env.add_implied_bounds(
-        infcx,
-        implied_bounds,
-        tcx.hir().local_def_id_to_hir_id(impl1_def_id),
-    );
         infcx.check_region_obligations_and_report_errors(impl1_def_id, &outlives_env);
         let Ok(impl2_substs) = infcx.fully_resolve(impl2_substs) else {
             let span = tcx.def_span(impl1_def_id);
@@ -165,6 +174,7 @@ fn get_impl_substs<'tcx>(
             return None;
         };
         Some((impl1_substs, impl2_substs))
+    })
 }
 
 /// Returns a list of all of the unconstrained subst of the given impl.
@@ -279,14 +289,13 @@ fn check_static_lifetimes<'tcx>(
 /// * a well-formed predicate of a type argument of the trait being implemented,
 ///   including the `Self`-type.
 fn check_predicates<'tcx>(
-    infcx: &InferCtxt<'_, 'tcx>,
+    tcx: TyCtxt<'tcx>,
     impl1_def_id: LocalDefId,
     impl1_substs: SubstsRef<'tcx>,
     impl2_node: Node,
     impl2_substs: SubstsRef<'tcx>,
     span: Span,
 ) {
-    let tcx = infcx.tcx;
     let instantiated = tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs);
     let impl1_predicates: Vec<_> = traits::elaborate_predicates_with_span(
         tcx,
@@ -343,19 +352,23 @@ fn check_predicates<'tcx>(
 
     // Include the well-formed predicates of the type parameters of the impl.
     for arg in tcx.impl_trait_ref(impl1_def_id).unwrap().substs {
-        if let Some(obligations) = wf::obligations(
+        tcx.infer_ctxt().enter(|ref infcx| {
+            let obligations = wf::obligations(
                 infcx,
                 tcx.param_env(impl1_def_id),
                 tcx.hir().local_def_id_to_hir_id(impl1_def_id),
                 0,
                 arg,
                 span,
-        ) {
+            )
+            .unwrap();
+
+            assert!(!obligations.needs_infer());
             impl2_predicates.extend(
                 traits::elaborate_obligations(tcx, obligations)
                     .map(|obligation| obligation.predicate),
             )
-        }
+        })
     }
     impl2_predicates.extend(
         traits::elaborate_predicates_with_span(tcx, always_applicable_traits)

src/test/ui/associated-types/associated-types-for-unimpl-trait.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-for-unimpl-trait.rs:10:40
+  --> $DIR/associated-types-for-unimpl-trait.rs:10:5
    |
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |

src/test/ui/associated-types/associated-types-no-suitable-bound.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `T: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-bound.rs:11:21
+  --> $DIR/associated-types-no-suitable-bound.rs:11:5
    |
 LL |     fn uhoh<T>(foo: <T as Get>::Value) {}
-   |                     ^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `T`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `T`
    |
 help: consider restricting type parameter `T`
    |

src/test/ui/associated-types/associated-types-no-suitable-supertrait-2.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait-2.rs:17:40
+  --> $DIR/associated-types-no-suitable-supertrait-2.rs:17:5
    |
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |

src/test/ui/associated-types/associated-types-no-suitable-supertrait.stderr

@@ -1,14 +1,14 @@
 error[E0277]: the trait bound `(T, U): Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait.rs:22:40
+  --> $DIR/associated-types-no-suitable-supertrait.rs:22:5
    |
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <(T, U) as Get>::Value) {}
-   |                                        ^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `(T, U)`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `(T, U)`
 
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-no-suitable-supertrait.rs:17:40
+  --> $DIR/associated-types-no-suitable-supertrait.rs:17:5
    |
 LL |     fn uhoh<U:Get>(&self, foo: U, bar: <Self as Get>::Value) {}
-   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |

src/test/ui/associated-types/associated-types-projection-to-unrelated-trait-in-method-without-default.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `Self: Get` is not satisfied
-  --> $DIR/associated-types-projection-to-unrelated-trait-in-method-without-default.rs:10:40
+  --> $DIR/associated-types-projection-to-unrelated-trait-in-method-without-default.rs:10:5
    |
 LL |     fn okay<U:Get>(&self, foo: U, bar: <Self as Get>::Value);
-   |                                        ^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Get` is not implemented for `Self`
    |
 help: consider further restricting `Self`
    |

src/test/ui/associated-types/issue-59324.stderr

@@ -45,16 +45,20 @@ LL | pub trait ThriftService<Bug: NotFoo + Foo>:
    |                                     +++++
 
 error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/issue-59324.rs:23:29
+  --> $DIR/issue-59324.rs:23:1
    |
 LL | fn with_factory<H>(factory: dyn ThriftService<()>) {}
-   |                             ^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
 
 error[E0277]: the trait bound `Bug: Foo` is not satisfied
-  --> $DIR/issue-59324.rs:16:8
+  --> $DIR/issue-59324.rs:16:5
    |
-LL |     fn get_service(
+LL | /     fn get_service(
-   |        ^^^^^^^^^^^ the trait `Foo` is not implemented for `Bug`
+LL | |
+LL | |
+LL | |         &self,
+LL | |     ) -> Self::AssocType;
+   | |_________________________^ the trait `Foo` is not implemented for `Bug`
    |
 help: consider further restricting this bound
    |

src/test/ui/issues/issue-18611.stderr

@@ -1,8 +1,10 @@
 error[E0277]: the trait bound `isize: HasState` is not satisfied
-  --> $DIR/issue-18611.rs:1:18
+  --> $DIR/issue-18611.rs:1:1
    |
-LL | fn add_state(op: <isize as HasState>::State) {
+LL | / fn add_state(op: <isize as HasState>::State) {
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HasState` is not implemented for `isize`
+LL | |
+LL | | }
+   | |_^ the trait `HasState` is not implemented for `isize`
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-20831-debruijn.stderr

@@ -1,8 +1,14 @@
 error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
-  --> $DIR/issue-20831-debruijn.rs:28:8
+  --> $DIR/issue-20831-debruijn.rs:28:5
    |
-LL |     fn subscribe(&mut self, t : Box<dyn Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
+LL | /     fn subscribe(&mut self, t : Box<dyn Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
-   |        ^^^^^^^^^
+LL | |         // Not obvious, but there is an implicit lifetime here -------^
+LL | |
+LL | |         //
+...  |
+LL | |         self.sub = t;
+LL | |     }
+   | |_____^
    |
 note: first, the lifetime cannot outlive the anonymous lifetime defined here...
   --> $DIR/issue-20831-debruijn.rs:28:58
@@ -15,10 +21,16 @@ note: ...but the lifetime must also be valid for the lifetime `'a` as defined he
 LL | impl<'a> Publisher<'a> for MyStruct<'a> {
    |      ^^
 note: ...so that the types are compatible
-  --> $DIR/issue-20831-debruijn.rs:28:8
+  --> $DIR/issue-20831-debruijn.rs:28:5
    |
-LL |     fn subscribe(&mut self, t : Box<dyn Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
+LL | /     fn subscribe(&mut self, t : Box<dyn Subscriber<Input=<Self as Publisher>::Output> + 'a>) {
-   |        ^^^^^^^^^
+LL | |         // Not obvious, but there is an implicit lifetime here -------^
+LL | |
+LL | |         //
+...  |
+LL | |         self.sub = t;
+LL | |     }
+   | |_____^
    = note: expected `<MyStruct<'a> as Publisher<'_>>`
               found `<MyStruct<'_> as Publisher<'_>>`
 

src/test/ui/issues/issue-35570.rs

@@ -6,7 +6,8 @@ trait Trait2<'a> {
 }
 
 fn _ice(param: Box<dyn for <'a> Trait1<<() as Trait2<'a>>::Ty>>) {
-//~^ the trait bound `for<'a> (): Trait2<'a>` is not satisfied
+    //~^ ERROR the trait bound `for<'a> (): Trait2<'a>` is not satisfied
+    //~| ERROR the trait bound `for<'a> (): Trait2<'a>` is not satisfied
     let _e: (usize, usize) = unsafe{mem::transmute(param)};
 }
 

src/test/ui/issues/issue-35570.stderr

@@ -1,9 +1,19 @@
+error[E0277]: the trait bound `for<'a> (): Trait2<'a>` is not satisfied
+  --> $DIR/issue-35570.rs:8:1
+   |
+LL | / fn _ice(param: Box<dyn for <'a> Trait1<<() as Trait2<'a>>::Ty>>) {
+LL | |
+LL | |
+LL | |     let _e: (usize, usize) = unsafe{mem::transmute(param)};
+LL | | }
+   | |_^ the trait `for<'a> Trait2<'a>` is not implemented for `()`
+
 error[E0277]: the trait bound `for<'a> (): Trait2<'a>` is not satisfied
   --> $DIR/issue-35570.rs:8:40
    |
 LL | fn _ice(param: Box<dyn for <'a> Trait1<<() as Trait2<'a>>::Ty>>) {
    |                                        ^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> Trait2<'a>` is not implemented for `()`
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/nll/normalization-bounds-error.stderr

@@ -1,8 +1,8 @@
 error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'d` due to conflicting requirements
-  --> $DIR/normalization-bounds-error.rs:12:4
+  --> $DIR/normalization-bounds-error.rs:12:1
    |
 LL | fn visit_seq<'d, 'a: 'd>() -> <&'a () as Visitor<'d>>::Value {}
-   |    ^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: first, the lifetime cannot outlive the lifetime `'d` as defined here...
   --> $DIR/normalization-bounds-error.rs:12:14
@@ -15,10 +15,10 @@ note: ...but the lifetime must also be valid for the lifetime `'a` as defined he
 LL | fn visit_seq<'d, 'a: 'd>() -> <&'a () as Visitor<'d>>::Value {}
    |                  ^^
 note: ...so that the types are compatible
-  --> $DIR/normalization-bounds-error.rs:12:4
+  --> $DIR/normalization-bounds-error.rs:12:1
    |
 LL | fn visit_seq<'d, 'a: 'd>() -> <&'a () as Visitor<'d>>::Value {}
-   |    ^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: expected `Visitor<'d>`
               found `Visitor<'_>`
 

src/test/ui/regions/regions-implied-bounds-projection-gap-hr-1.rs

@@ -19,7 +19,8 @@ trait Trait2<'a, 'b> {
 // since for it to be WF, we would need to know that `'y: 'x`, but we
 // do not infer that.
 fn callee<'x, 'y, T>(t: &'x dyn for<'z> Trait1< <T as Trait2<'y, 'z>>::Foo >)
-    //~^ the trait bound `for<'z> T: Trait2<'y, 'z>` is not satisfied
+    //~^ ERROR the trait bound `for<'z> T: Trait2<'y, 'z>` is not satisfied
+    //~| ERROR the trait bound `for<'z> T: Trait2<'y, 'z>` is not satisfied
 {
 }
 

src/test/ui/regions/regions-implied-bounds-projection-gap-hr-1.stderr

@@ -1,3 +1,18 @@
+error[E0277]: the trait bound `for<'z> T: Trait2<'y, 'z>` is not satisfied
+  --> $DIR/regions-implied-bounds-projection-gap-hr-1.rs:21:1
+   |
+LL | / fn callee<'x, 'y, T>(t: &'x dyn for<'z> Trait1< <T as Trait2<'y, 'z>>::Foo >)
+LL | |
+LL | |
+LL | | {
+LL | | }
+   | |_^ the trait `for<'z> Trait2<'y, 'z>` is not implemented for `T`
+   |
+help: consider restricting type parameter `T`
+   |
+LL | fn callee<'x, 'y, T: for<'z> Trait2<'y, 'z>>(t: &'x dyn for<'z> Trait1< <T as Trait2<'y, 'z>>::Foo >)
+   |                    ++++++++++++++++++++++++
+
 error[E0277]: the trait bound `for<'z> T: Trait2<'y, 'z>` is not satisfied
   --> $DIR/regions-implied-bounds-projection-gap-hr-1.rs:21:49
    |
@@ -9,6 +24,6 @@ help: consider restricting type parameter `T`
 LL | fn callee<'x, 'y, T: for<'z> Trait2<'y, 'z>>(t: &'x dyn for<'z> Trait1< <T as Trait2<'y, 'z>>::Foo >)
    |                    ++++++++++++++++++++++++
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

src/test/ui/specialization/min_specialization/issue-79224.stderr

@@ -1,8 +1,12 @@
 error[E0277]: the trait bound `B: Clone` is not satisfied
-  --> $DIR/issue-79224.rs:18:17
+  --> $DIR/issue-79224.rs:18:1
    |
-LL | impl<B: ?Sized> Display for Cow<'_, B> {
+LL | / impl<B: ?Sized> Display for Cow<'_, B> {
-   |                 ^^^^^^^ the trait `Clone` is not implemented for `B`
+LL | |     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+LL | |         write!(f, "foo")
+LL | |     }
+LL | | }
+   | |_^ the trait `Clone` is not implemented for `B`
    |
    = note: required because of the requirements on the impl of `ToOwned` for `B`
 help: consider further restricting this bound
@@ -11,10 +15,12 @@ LL | impl<B: ?Sized + std::clone::Clone> Display for Cow<'_, B> {
    |                +++++++++++++++++++
 
 error[E0277]: the trait bound `B: Clone` is not satisfied
-  --> $DIR/issue-79224.rs:19:12
+  --> $DIR/issue-79224.rs:19:5
    |
-LL |     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+LL | /     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-   |            ^^^^^ the trait `Clone` is not implemented for `B`
+LL | |         write!(f, "foo")
+LL | |     }
+   | |_____^ the trait `Clone` is not implemented for `B`
    |
    = note: required because of the requirements on the impl of `ToOwned` for `B`
 help: consider further restricting this bound

src/test/ui/traits/issue-91594.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `Foo: HasComponent<()>` is not satisfied
-  --> $DIR/issue-91594.rs:10:6
+  --> $DIR/issue-91594.rs:10:1
    |
 LL | impl HasComponent<<Foo as Component<Foo>>::Interface> for Foo {}
-   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HasComponent<()>` is not implemented for `Foo`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `HasComponent<()>` is not implemented for `Foo`
    |
    = help: the trait `HasComponent<<Foo as Component<Foo>>::Interface>` is implemented for `Foo`
 note: required because of the requirements on the impl of `Component<Foo>` for `Foo`

src/test/ui/wf/wf-foreign-fn-decl-ret.stderr

@@ -1,8 +1,8 @@
 error[E0277]: the trait bound `(): Foo` is not satisfied
-  --> $DIR/wf-foreign-fn-decl-ret.rs:11:25
+  --> $DIR/wf-foreign-fn-decl-ret.rs:11:5
    |
 LL |     pub fn lint_me() -> <() as Foo>::Assoc;
-   |                         ^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `()`
 
 error[E0277]: the trait bound `u32: Unsatisfied` is not satisfied
   --> $DIR/wf-foreign-fn-decl-ret.rs:14:32