Add spans to E0277 for impl/trait type/fn obligation disparity

1 files changed, 52 insertions, 11 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 68e7accd34b..6a4d41ffc1a 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2179,19 +2179,60 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     )
                 });
             }
-            ObligationCauseCode::CompareImplMethodObligation { .. } => {
-                err.note(&format!(
-                    "the requirement `{}` appears on the impl method but not on the corresponding \
-                     trait method",
-                    predicate
-                ));
+            ObligationCauseCode::CompareImplMethodObligation {
+                item_name,
+                trait_item_def_id,
+                ..
+            } => {
+                let msg = format!(
+                    "the requirement `{}` appears on the impl method `{}` but not on the \
+                     corresponding trait method",
+                    predicate, item_name,
+                );
+                let sp = self
+                    .tcx
+                    .opt_item_name(trait_item_def_id)
+                    .map(|i| i.span)
+                    .unwrap_or_else(|| self.tcx.def_span(trait_item_def_id));
+                let mut assoc_span: MultiSpan = sp.into();
+                assoc_span.push_span_label(
+                    sp,
+                    format!("this trait method doesn't have the requirement `{}`", predicate),
+                );
+                if let Some(ident) = self
+                    .tcx
+                    .opt_associated_item(trait_item_def_id)
+                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                {
+                    assoc_span.push_span_label(ident.span, "in this trait".into());
+                }
+                err.span_note(assoc_span, &msg);
             }
-            ObligationCauseCode::CompareImplTypeObligation { .. } => {
-                err.note(&format!(
-                    "the requirement `{}` appears on the associated impl type but not on the \
+            ObligationCauseCode::CompareImplTypeObligation {
+                item_name, trait_item_def_id, ..
+            } => {
+                let msg = format!(
+                    "the requirement `{}` appears on the associated impl type `{}` but not on the \
                      corresponding associated trait type",
-                    predicate
-                ));
+                    predicate, item_name,
+                );
+                let sp = self.tcx.def_span(trait_item_def_id);
+                let mut assoc_span: MultiSpan = sp.into();
+                assoc_span.push_span_label(
+                    sp,
+                    format!(
+                        "this trait associated type doesn't have the requirement `{}`",
+                        predicate,
+                    ),
+                );
+                if let Some(ident) = self
+                    .tcx
+                    .opt_associated_item(trait_item_def_id)
+                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                {
+                    assoc_span.push_span_label(ident.span, "in this trait".into());
+                }
+                err.span_note(assoc_span, &msg);
             }
             ObligationCauseCode::CompareImplConstObligation => {
                 err.note(&format!(