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-rw-r--r--compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs31
1 files changed, 22 insertions, 9 deletions
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 864510bb650..eab4addf970 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -4,6 +4,7 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
+use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
 use rustc_middle::ty::print::{FmtPrinter, Printer};
 use rustc_middle::ty::{self, suggest_constraining_type_param, Ty};
 use rustc_span::def_id::DefId;
@@ -313,11 +314,15 @@ impl<T> Trait<T> for X {
                     (ty::Dynamic(t, _, ty::DynKind::Dyn), _)
                         if let Some(def_id) = t.principal_def_id() =>
                     {
-                        let mut impl_def_ids = vec![];
+                        let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.found, |did| {
-                            impl_def_ids.push(did)
+                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                                .types_may_unify(values.found, tcx.type_of(did).skip_binder())
+                            {
+                                has_matching_impl = true;
+                            }
                         });
-                        if let [_] = &impl_def_ids[..] {
+                        if has_matching_impl {
                             let trait_name = tcx.item_name(def_id);
                             diag.help(format!(
                                 "`{}` implements `{trait_name}` so you could box the found value \
@@ -330,11 +335,15 @@ impl<T> Trait<T> for X {
                     (_, ty::Dynamic(t, _, ty::DynKind::Dyn))
                         if let Some(def_id) = t.principal_def_id() =>
                     {
-                        let mut impl_def_ids = vec![];
+                        let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.expected, |did| {
-                            impl_def_ids.push(did)
+                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                                .types_may_unify(values.expected, tcx.type_of(did).skip_binder())
+                            {
+                                has_matching_impl = true;
+                            }
                         });
-                        if let [_] = &impl_def_ids[..] {
+                        if has_matching_impl {
                             let trait_name = tcx.item_name(def_id);
                             diag.help(format!(
                                 "`{}` implements `{trait_name}` so you could change the expected \
@@ -346,11 +355,15 @@ impl<T> Trait<T> for X {
                     (ty::Dynamic(t, _, ty::DynKind::DynStar), _)
                         if let Some(def_id) = t.principal_def_id() =>
                     {
-                        let mut impl_def_ids = vec![];
+                        let mut has_matching_impl = false;
                         tcx.for_each_relevant_impl(def_id, values.found, |did| {
-                            impl_def_ids.push(did)
+                            if DeepRejectCtxt::new(tcx, TreatParams::ForLookup)
+                                .types_may_unify(values.found, tcx.type_of(did).skip_binder())
+                            {
+                                has_matching_impl = true;
+                            }
                         });
-                        if let [_] = &impl_def_ids[..] {
+                        if has_matching_impl {
                             let trait_name = tcx.item_name(def_id);
                             diag.help(format!(
                                 "`{}` implements `{trait_name}`, `#[feature(dyn_star)]` is likely \