Rollup merge of #127557 - linyihai:issue-126694, r=compiler-errors

Add a label to point to the lacking macro name definition

Fixes https://github.com/rust-lang/rust/issues/126694, but adopts the suggestion from https://github.com/rust-lang/rust/issues/118295

```
 --> src/main.rs:1:14
  |
1 | macro_rules! {
  |            ^ put a macro name here
```

2 files changed, 5 insertions, 2 deletions

diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 046ae5fc593..df80f4df5b9 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -1448,7 +1448,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         );
 
         if macro_kind == MacroKind::Bang && ident.name == sym::macro_rules {
-            err.subdiagnostic(MaybeMissingMacroRulesName { span: ident.span });
+            let label_span = ident.span.shrink_to_hi();
+            let mut spans = MultiSpan::from_span(label_span);
+            spans.push_span_label(label_span, "put a macro name here");
+            err.subdiagnostic(MaybeMissingMacroRulesName { spans: spans });
             return;
         }
 
diff --git a/compiler/rustc_resolve/src/errors.rs b/compiler/rustc_resolve/src/errors.rs
index 0a68231c6fe..698147765b3 100644
--- a/compiler/rustc_resolve/src/errors.rs
+++ b/compiler/rustc_resolve/src/errors.rs
@@ -669,7 +669,7 @@ pub(crate) struct MacroSuggMovePosition {
 #[note(resolve_missing_macro_rules_name)]
 pub(crate) struct MaybeMissingMacroRulesName {
     #[primary_span]
-    pub(crate) span: Span,
+    pub(crate) spans: MultiSpan,
 }
 
 #[derive(Subdiagnostic)]