Rollup merge of #117205 - weiznich:multiple_notes_for_on_unimplemented, r=compiler-errors

Allows `#[diagnostic::on_unimplemented]` attributes to have multiple

notes

This commit extends the `#[diagnostic::on_unimplemented]` (and `#[rustc_on_unimplemented]`) attributes to allow multiple `note` options. This enables emitting multiple notes for custom error messages. For now I've opted to not change any of the existing usages of `#[rustc_on_unimplemented]` and just updated the relevant compile tests.

r? `@compiler-errors`

I'm happy to adjust any of the existing changed location to emit the old error message if that's desired.

2 files changed, 24 insertions, 22 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
index c96e41b88bd..a5508c74134 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
@@ -319,7 +319,7 @@ pub struct OnUnimplementedDirective {
     pub subcommands: Vec<OnUnimplementedDirective>,
     pub message: Option<OnUnimplementedFormatString>,
     pub label: Option<OnUnimplementedFormatString>,
-    pub note: Option<OnUnimplementedFormatString>,
+    pub notes: Vec<OnUnimplementedFormatString>,
     pub parent_label: Option<OnUnimplementedFormatString>,
     pub append_const_msg: Option<AppendConstMessage>,
 }
@@ -329,7 +329,7 @@ pub struct OnUnimplementedDirective {
 pub struct OnUnimplementedNote {
     pub message: Option<String>,
     pub label: Option<String>,
-    pub note: Option<String>,
+    pub notes: Vec<String>,
     pub parent_label: Option<String>,
     // If none, should fall back to a generic message
     pub append_const_msg: Option<AppendConstMessage>,
@@ -399,7 +399,7 @@ impl<'tcx> OnUnimplementedDirective {
 
         let mut message = None;
         let mut label = None;
-        let mut note = None;
+        let mut notes = Vec::new();
         let mut parent_label = None;
         let mut subcommands = vec![];
         let mut append_const_msg = None;
@@ -415,10 +415,12 @@ impl<'tcx> OnUnimplementedDirective {
                     label = parse_value(label_)?;
                     continue;
                 }
-            } else if item.has_name(sym::note) && note.is_none() {
+            } else if item.has_name(sym::note) {
                 if let Some(note_) = item.value_str() {
-                    note = parse_value(note_)?;
-                    continue;
+                    if let Some(note) = parse_value(note_)? {
+                        notes.push(note);
+                        continue;
+                    }
                 }
             } else if item.has_name(sym::parent_label)
                 && parent_label.is_none()
@@ -432,7 +434,7 @@ impl<'tcx> OnUnimplementedDirective {
                 && is_root
                 && message.is_none()
                 && label.is_none()
-                && note.is_none()
+                && notes.is_empty()
                 && !is_diagnostic_namespace_variant
             // FIXME(diagnostic_namespace): disallow filters for now
             {
@@ -487,7 +489,7 @@ impl<'tcx> OnUnimplementedDirective {
                 subcommands,
                 message,
                 label,
-                note,
+                notes,
                 parent_label,
                 append_const_msg,
             }))
@@ -505,12 +507,14 @@ impl<'tcx> OnUnimplementedDirective {
                     if let Some(aggr) = aggr {
                         let mut subcommands = aggr.subcommands;
                         subcommands.extend(directive.subcommands);
+                        let mut notes = aggr.notes;
+                        notes.extend(directive.notes);
                         Ok(Some(Self {
                             condition: aggr.condition.or(directive.condition),
                             subcommands,
                             message: aggr.message.or(directive.message),
                             label: aggr.label.or(directive.label),
-                            note: aggr.note.or(directive.note),
+                            notes,
                             parent_label: aggr.parent_label.or(directive.parent_label),
                             append_const_msg: aggr.append_const_msg.or(directive.append_const_msg),
                         }))
@@ -543,7 +547,7 @@ impl<'tcx> OnUnimplementedDirective {
                         value,
                         attr.span,
                     )?),
-                    note: None,
+                    notes: Vec::new(),
                     parent_label: None,
                     append_const_msg: None,
                 }))
@@ -600,7 +604,7 @@ impl<'tcx> OnUnimplementedDirective {
     ) -> OnUnimplementedNote {
         let mut message = None;
         let mut label = None;
-        let mut note = None;
+        let mut notes = Vec::new();
         let mut parent_label = None;
         let mut append_const_msg = None;
         info!("evaluate({:?}, trait_ref={:?}, options={:?})", self, trait_ref, options);
@@ -637,9 +641,7 @@ impl<'tcx> OnUnimplementedDirective {
                 label = Some(label_.clone());
             }
 
-            if let Some(ref note_) = command.note {
-                note = Some(note_.clone());
-            }
+            notes.extend(command.notes.clone());
 
             if let Some(ref parent_label_) = command.parent_label {
                 parent_label = Some(parent_label_.clone());
@@ -651,7 +653,7 @@ impl<'tcx> OnUnimplementedDirective {
         OnUnimplementedNote {
             label: label.map(|l| l.format(tcx, trait_ref, &options_map)),
             message: message.map(|m| m.format(tcx, trait_ref, &options_map)),
-            note: note.map(|n| n.format(tcx, trait_ref, &options_map)),
+            notes: notes.into_iter().map(|n| n.format(tcx, trait_ref, &options_map)).collect(),
             parent_label: parent_label.map(|e_s| e_s.format(tcx, trait_ref, &options_map)),
             append_const_msg,
         }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
index a697c6650b2..f9ce81ce165 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/type_err_ctxt_ext.rs
@@ -445,7 +445,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         let OnUnimplementedNote {
                             message,
                             label,
-                            note,
+                            notes,
                             parent_label,
                             append_const_msg,
                         } = self.on_unimplemented_note(trait_ref, &obligation);
@@ -453,21 +453,21 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         let is_try_conversion = self.is_try_conversion(span, trait_ref.def_id());
                         let is_unsize =
                             Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait();
-                        let (message, note, append_const_msg) = if is_try_conversion {
+                        let (message, notes, append_const_msg) = if is_try_conversion {
                             (
                                 Some(format!(
                                     "`?` couldn't convert the error to `{}`",
                                     trait_ref.skip_binder().self_ty(),
                                 )),
-                                Some(
+                                vec![
                                     "the question mark operation (`?`) implicitly performs a \
                                      conversion on the error value using the `From` trait"
                                         .to_owned(),
-                                ),
+                                ],
                                 Some(AppendConstMessage::Default),
                             )
                         } else {
-                            (message, note, append_const_msg)
+                            (message, notes, append_const_msg)
                         };
 
                         let err_msg = self.get_standard_error_message(
@@ -588,9 +588,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         if let Some((msg, span)) = type_def {
                             err.span_label(span, msg);
                         }
-                        if let Some(s) = note {
+                        for note in notes {
                             // If it has a custom `#[rustc_on_unimplemented]` note, let's display it
-                            err.note(s);
+                            err.note(note);
                         }
                         if let Some(s) = parent_label {
                             let body = obligation.cause.body_id;