Tweak E0478

```
error[E0478]: lifetime bound not satisfied
  --> $DIR/point-at-lifetime-obligation-from-trait-in-trait-object.rs:4:27
   |
LL |     broken: Box<dyn Any + 'a>
   |                     ---   ^^ lifetime bound not satisfied
   |                     |
   |                     this requires `'static`
   |
note: lifetime parameter instantiated with the lifetime `'a` as defined here
  --> $DIR/point-at-lifetime-obligation-from-trait-in-trait-object.rs:3:18
   |
LL | struct Something<'a> {
   |                  ^^
   = note: but lifetime parameter must outlive the static lifetime
note: `'static` requirement introduced here
  --> $SRC_DIR/core/src/any.rs:LL:COL
```

Author: estebank

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

@@ -59,7 +59,7 @@ use crate::traits::{
     PredicateObligation,
 };
 
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_errors::{
     codes::*, pluralize, struct_span_code_err, Applicability, Diag, DiagCtxt, DiagStyledString,
     ErrorGuaranteed, IntoDiagArg, MultiSpan,
@@ -2709,7 +2709,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         pub struct HirTraitObjectVisitor<'tcx> {
             pub expected_region: ty::Region<'tcx>,
             pub found_region: ty::Region<'tcx>,
-            pub lifetime_spans: FxHashSet<Span>,
+            pub primary_spans: Vec<Span>,
+            pub secondary_spans: Vec<Span>,
             pub pred_spans: Vec<Span>,
             pub tcx: TyCtxt<'tcx>,
         }
@@ -2727,7 +2728,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     _ => false,
                 } {
                     // We want to keep a span to the lifetime bound on the trait object.
-                    self.lifetime_spans.insert(lt.ident.span);
+                    self.primary_spans.push(lt.ident.span);
                 }
             }
             fn visit_ty(&mut self, t: &'tcx hir::Ty<'tcx>) {
@@ -2753,18 +2754,20 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                                     .filter_map(filter_predicates(self.found_region, |_| true))
                                     .collect();
                                 if !bindings.is_empty() {
-                                    self.lifetime_spans.insert(ptr.span);
+                                    self.secondary_spans.push(ptr.span);
                                     self.pred_spans.extend(bindings);
                                 }
                             }
                         }
                     }
                     // Detect when an associated item is given a lifetime restriction that the
                     // definition of that associated item couldn't meet.
-                    hir::TyKind::Path(hir::QPath::Resolved(Some(_), path)) => {
-                        self.pred_spans = elaborate_predicates_of(self.tcx, path.res.def_id())
-                            .filter_map(filter_predicates(self.found_region, |_| true))
-                            .collect();
+                    hir::TyKind::Path(hir::QPath::Resolved(_, path)) => {
+                        self.pred_spans.extend(
+                            elaborate_predicates_of(self.tcx, path.res.def_id())
+                                .filter_map(filter_predicates(self.found_region, |_| true))
+                                .collect::<Vec<_>>(),
+                        );
                     }
                     _ => {}
                 }
@@ -2774,7 +2777,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let mut visitor = HirTraitObjectVisitor {
             expected_region: sup,
             found_region: sub,
-            lifetime_spans: Default::default(),
+            primary_spans: vec![],
+            secondary_spans: vec![],
             pred_spans: vec![],
             tcx: self.tcx,
         };
@@ -2786,9 +2790,22 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
         }
 
-        #[allow(rustc::potential_query_instability)]
-        let primary_spans: Vec<Span> = visitor.lifetime_spans.into_iter().collect();
-        Some((primary_spans.into(), visitor.pred_spans.into()))
+        visitor.primary_spans.sort();
+        let mut primary_span: MultiSpan = visitor.primary_spans.clone().into();
+        if let Some(last) = visitor.primary_spans.iter().rev().next() {
+            primary_span.push_span_label(
+                *last,
+                format!(
+                    "lifetime bound{s} not satisfied",
+                    s = pluralize!(visitor.primary_spans.len())
+                ),
+            );
+        }
+
+        for span in visitor.secondary_spans {
+            primary_span.push_span_label(span, format!("this requires `{sub}`"));
+        }
+        Some((primary_span, visitor.pred_spans.into()))
     }
 
     /// Determine whether an error associated with the given span and definition

tests/ui/error-codes/E0478.stderr

@@ -2,7 +2,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/E0478.rs:4:37
    |
 LL |     child: Box<dyn Wedding<'kiss> + 'SnowWhite>,
-   |                                     ^^^^^^^^^^
+   |                                     ^^^^^^^^^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'SnowWhite` as defined here
   --> $DIR/E0478.rs:3:22

tests/ui/generic-associated-types/unsatisfied-item-lifetime-bound.stderr

@@ -35,7 +35,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/unsatisfied-item-lifetime-bound.rs:14:20
    |
 LL |     f: <T as X>::Y<'a>,
-   |                    ^^
+   |                    ^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
   --> $DIR/unsatisfied-item-lifetime-bound.rs:13:10
@@ -53,7 +53,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/unsatisfied-item-lifetime-bound.rs:19:20
    |
 LL |     f: <T as X>::Y<'a>,
-   |                    ^^
+   |                    ^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
   --> $DIR/unsatisfied-item-lifetime-bound.rs:18:10
@@ -71,7 +71,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/unsatisfied-item-lifetime-bound.rs:24:21
    |
 LL |     f: <() as X>::Y<'a>,
-   |                     ^^
+   |                     ^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
   --> $DIR/unsatisfied-item-lifetime-bound.rs:23:10

tests/ui/lifetimes/point-at-lifetime-obligation-from-trait-in-trait-object.stderr

@@ -1,8 +1,10 @@
 error[E0478]: lifetime bound not satisfied
-  --> $DIR/point-at-lifetime-obligation-from-trait-in-trait-object.rs:4:21
+  --> $DIR/point-at-lifetime-obligation-from-trait-in-trait-object.rs:4:27
    |
 LL |     broken: Box<dyn Any + 'a>
-   |                     ^^^   ^^
+   |                     ---   ^^ lifetime bound not satisfied
+   |                     |
+   |                     this requires `'static`
    |
 note: lifetime parameter instantiated with the lifetime `'a` as defined here
   --> $DIR/point-at-lifetime-obligation-from-trait-in-trait-object.rs:3:18

tests/ui/regions/region-bounds-on-objects-and-type-parameters.stderr

@@ -8,7 +8,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/region-bounds-on-objects-and-type-parameters.rs:21:23
    |
 LL |     z: Box<dyn Is<'a>+'b+'c>,
-   |                       ^^
+   |                       ^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'b` as defined here
   --> $DIR/region-bounds-on-objects-and-type-parameters.rs:11:15

tests/ui/regions/regions-wf-trait-object.stderr

@@ -2,7 +2,7 @@ error[E0478]: lifetime bound not satisfied
   --> $DIR/regions-wf-trait-object.rs:7:29
    |
 LL |     x: Box<dyn TheTrait<'a>+'b>
-   |                             ^^
+   |                             ^^ lifetime bound not satisfied
    |
 note: lifetime parameter instantiated with the lifetime `'b` as defined here
   --> $DIR/regions-wf-trait-object.rs:6:15