Tweak output to account for alternative bindings in the same pattern

Author: estebank

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -192,26 +192,23 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     is_loop_move = true;
                 }
 
-                self.suggest_ref_or_clone(
-                    mpi,
-                    move_span,
-                    &mut err,
-                    &mut seen_spans,
-                    &mut in_pattern,
-                );
+                if !seen_spans.contains(&move_span) {
+                    self.suggest_ref_or_clone(mpi, move_span, &mut err, &mut in_pattern);
 
-                self.explain_captures(
-                    &mut err,
-                    span,
-                    move_span,
-                    move_spans,
-                    *moved_place,
-                    partially_str,
-                    loop_message,
-                    move_msg,
-                    is_loop_move,
-                    maybe_reinitialized_locations.is_empty(),
-                );
+                    self.explain_captures(
+                        &mut err,
+                        span,
+                        move_span,
+                        move_spans,
+                        *moved_place,
+                        partially_str,
+                        loop_message,
+                        move_msg,
+                        is_loop_move,
+                        maybe_reinitialized_locations.is_empty(),
+                    );
+                }
+                seen_spans.insert(move_span);
             }
 
             use_spans.var_path_only_subdiag(&mut err, desired_action);
@@ -312,7 +309,6 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         mpi: MovePathIndex,
         move_span: Span,
         err: &mut DiagnosticBuilder<'_, ErrorGuaranteed>,
-        seen_spans: &mut FxHashSet<Span>,
         in_pattern: &mut bool,
     ) {
         struct ExpressionFinder<'hir> {
@@ -436,15 +432,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     }
                 }
             }
-            if let Some(pat) = finder.pat && !seen_spans.contains(&pat.span) {
+            if let Some(pat) = finder.pat {
                 *in_pattern = true;
                 err.span_suggestion_verbose(
                     pat.span.shrink_to_lo(),
                     "borrow this binding in the pattern to avoid moving the value",
                     "ref ".to_string(),
                     Applicability::MachineApplicable,
                 );
-                seen_spans.insert(pat.span);
             }
         }
     }

src/test/ui/borrowck/bindings-after-at-or-patterns-slice-patterns-box-patterns.stderr

@@ -76,10 +76,7 @@ LL | fn bindings_after_at_or_patterns_move(x: Option<Test>) {
    |                                       - move occurs because `x` has type `Option<Test>`, which does not implement the `Copy` trait
 LL |     match x {
 LL |         foo @ Some(Test::Foo | Test::Bar) => (),
-   |         ---
-   |         |
-   |         value moved here
-   |         value moved here
+   |         --- value moved here
 ...
 LL |     &x;
    |     ^^ value borrowed here after move
@@ -132,10 +129,7 @@ LL | fn bindings_after_at_slice_patterns_or_patterns_moves(x: [Option<Test>; 4])
    |                                                       - move occurs because `x` has type `[Option<Test>; 4]`, which does not implement the `Copy` trait
 LL |     match x {
 LL |         a @ [.., Some(Test::Foo | Test::Bar)] => (),
-   |         -
-   |         |
-   |         value moved here
-   |         value moved here
+   |         - value moved here
 ...
 LL |     &x;
    |     ^^ value borrowed here after move