Look at proc-macro attributes when encountering unknown attribute

```
error: cannot find attribute `sede` in this scope
  --> src/main.rs:18:7
   |
18 |     #[sede(untagged)]
   |       ^^^^
   |
help: the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute
   |
18 |     #[serde(untagged)]
   |       ~~~~~

error: cannot find attribute `serde` in this scope
  --> src/main.rs:12:7
   |
12 |     #[serde(untagged)]
   |       ^^^^^
   |
   = note: `serde` is in scope, but it is a crate, not an attribute
help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
   |
10 + #[derive(Serialize, Deserialize)]
11 | struct Foo {
   |
```

Mitigate rust-lang#47608.

Author: estebank

compiler/rustc_resolve/src/diagnostics.rs

@@ -4,7 +4,7 @@ use rustc_ast::ptr::P;
 use rustc_ast::visit::{self, Visitor};
 use rustc_ast::{self as ast, Crate, ItemKind, ModKind, NodeId, Path, CRATE_NODE_ID};
 use rustc_ast_pretty::pprust;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::{
     pluralize, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
 };
@@ -1016,6 +1016,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                 parent_scope,
                                 false,
                                 false,
+                                None,
                             ) {
                                 suggestions.extend(
                                     ext.helper_attrs
@@ -1331,15 +1332,40 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         macro_kind: MacroKind,
         parent_scope: &ParentScope<'a>,
         ident: Ident,
+        sugg_span: Option<Span>,
     ) {
+        // Bring imported but unused `derive` macros into `macro_map` so we ensure they can be used
+        // for suggestions.
+        self.visit_scopes(
+            ScopeSet::Macro(MacroKind::Derive),
+            &parent_scope,
+            ident.span.ctxt(),
+            |this, scope, _use_prelude, _ctxt| {
+                let Scope::Module(m, _) = scope else { return None; };
+                for (_, resolution) in this.resolutions(m).borrow().iter() {
+                    let Some(binding) = resolution.borrow().binding else { continue; };
+                    let Res::Def(
+                        DefKind::Macro(MacroKind::Derive | MacroKind::Attr),
+                        def_id,
+                    ) = binding.res() else { continue; };
+                    // By doing this all *imported* macros get added to the `macro_map` even if they
+                    // are *unused*, which makes the later suggestions find them and work.
+                    let _ = this.get_macro_by_def_id(def_id);
+                }
+                None::<()>
+            },
+        );
+
         let is_expected = &|res: Res| res.macro_kind() == Some(macro_kind);
         let suggestion = self.early_lookup_typo_candidate(
             ScopeSet::Macro(macro_kind),
             parent_scope,
             ident,
             is_expected,
         );
-        self.add_typo_suggestion(err, suggestion, ident.span);
+        if !self.add_typo_suggestion(err, suggestion, ident.span) {
+            self.add_derive_for_attribute(err, sugg_span, ident, parent_scope);
+        }
 
         let import_suggestions =
             self.lookup_import_candidates(ident, Namespace::MacroNS, parent_scope, is_expected);
@@ -1364,14 +1390,20 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             err.help("have you added the `#[macro_use]` on the module/import?");
             return;
         }
+
         if ident.name == kw::Default
             && let ModuleKind::Def(DefKind::Enum, def_id, _) = parent_scope.module.kind
         {
             let span = self.def_span(def_id);
             let source_map = self.tcx.sess.source_map();
             let head_span = source_map.guess_head_span(span);
-            if let Ok(head) = source_map.span_to_snippet(head_span) {
-                err.span_suggestion(head_span, "consider adding a derive", format!("#[derive(Default)]\n{head}"), Applicability::MaybeIncorrect);
+            if let Ok(_) = source_map.span_to_snippet(head_span) {
+                err.span_suggestion(
+                    head_span.shrink_to_lo(),
+                    "consider adding a derive",
+                    format!("#[derive(Default)]\n"),
+                    Applicability::MaybeIncorrect,
+                );
             } else {
                 err.span_help(
                     head_span,
@@ -1494,6 +1526,102 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         true
     }
 
+    fn add_derive_for_attribute(
+        &self,
+        err: &mut Diagnostic,
+        sugg_span: Option<Span>,
+        ident: Ident,
+        parent_scope: &ParentScope<'_>,
+    ) {
+        // FIXME: this only works if the macro that has the helper_attr has already
+        // been imported.
+        let mut derives = vec![];
+        let mut all_attrs: FxHashMap<Symbol, Vec<_>> = FxHashMap::default();
+        for (def_id, data) in &self.macro_map {
+            for helper_attr in &data.ext.helper_attrs {
+                let item_name = self.tcx.item_name(*def_id);
+                all_attrs.entry(*helper_attr).or_default().push(item_name);
+                if helper_attr == &ident.name {
+                    // FIXME: we should also do Levenshtein distance checks here.
+                    derives.push(item_name);
+                }
+            }
+        }
+        let kind = MacroKind::Derive.descr();
+        if !derives.is_empty() {
+            derives.sort();
+            derives.dedup();
+            let msg = match &derives[..] {
+                [derive] => format!(" `{derive}`"),
+                [start @ .., last] => format!(
+                    "s {} and `{last}`",
+                    start.iter().map(|d| format!("`{d}`")).collect::<Vec<_>>().join(", ")
+                ),
+                [] => unreachable!("we checked for this to be non-empty 10 lines above!?"),
+            };
+            let msg = format!(
+                "`{}` is an attribute that can be used by the {kind}{msg}, you might be missing a \
+                `derive` attribute",
+                ident.name,
+            );
+            let sugg_span = if let ModuleKind::Def(DefKind::Enum, id, _) = parent_scope.module.kind
+            {
+                let span = self.def_span(id);
+                if span.from_expansion() {
+                    None
+                } else {
+                    // For enum variants, `sugg_span` is empty, but we can get the `enum`'s `Span`.
+                    Some(span.shrink_to_lo())
+                }
+            } else {
+                // For items, this `Span` will be populated, everything else it'll be `None`.
+                sugg_span
+            };
+            match sugg_span {
+                Some(span) => {
+                    err.span_suggestion_verbose(
+                        span,
+                        &msg,
+                        format!(
+                            "#[derive({})]\n",
+                            derives
+                                .iter()
+                                .map(|d| d.to_string())
+                                .collect::<Vec<String>>()
+                                .join(", ")
+                        ),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+                None => {
+                    err.note(&msg);
+                }
+            }
+        } else {
+            let all_attr_names: Vec<Symbol> = all_attrs.keys().cloned().collect();
+            if let Some(best_match) = find_best_match_for_name(&all_attr_names, ident.name, None)
+                && let Some(macros) = all_attrs.get(&best_match)
+                && !macros.is_empty()
+            {
+                let msg = match &macros[..] {
+                    [] => unreachable!("we checked above in the if-let"),
+                    [name] => format!(" `{name}` accepts"),
+                    [start @ .., end] => format!(
+                        "s {} and `{end}` accept",
+                        start.iter().map(|m| format!("`{m}`")).collect::<Vec<_>>().join(", "),
+                    ),
+                };
+                let msg =  format!("the {kind}{msg} the similarly named `{best_match}` attribute");
+                err.span_suggestion_verbose(
+                    ident.span,
+                    &msg,
+                    best_match,
+                    Applicability::MaybeIncorrect,
+                );
+            }
+        }
+    }
+
     fn binding_description(&self, b: &NameBinding<'_>, ident: Ident, from_prelude: bool) -> String {
         let res = b.res();
         if b.span.is_dummy() || !self.tcx.sess.source_map().is_span_accessible(b.span) {

compiler/rustc_resolve/src/ident.rs

@@ -459,6 +459,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                 parent_scope,
                                 true,
                                 force,
+                                None,
                             ) {
                                 Ok((Some(ext), _)) => {
                                     if ext.helper_attrs.contains(&ident.name) {

compiler/rustc_resolve/src/late.rs

@@ -3715,7 +3715,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
             let path_seg = |seg: &Segment| PathSegment::from_ident(seg.ident);
             let path = Path { segments: path.iter().map(path_seg).collect(), span, tokens: None };
             if let Ok((_, res)) =
-                self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false)
+                self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false, None)
             {
                 return Ok(Some(PartialRes::new(res)));
             }

compiler/rustc_resolve/src/lib.rs

@@ -975,9 +975,9 @@ pub struct Resolver<'a, 'tcx> {
     proc_macro_stubs: FxHashSet<LocalDefId>,
     /// Traces collected during macro resolution and validated when it's complete.
     single_segment_macro_resolutions:
-        Vec<(Ident, MacroKind, ParentScope<'a>, Option<&'a NameBinding<'a>>)>,
+        Vec<(Ident, MacroKind, ParentScope<'a>, Option<&'a NameBinding<'a>>, Option<Span>)>,
     multi_segment_macro_resolutions:
-        Vec<(Vec<Segment>, Span, MacroKind, ParentScope<'a>, Option<Res>)>,
+        Vec<(Vec<Segment>, Span, MacroKind, ParentScope<'a>, Option<Res>, Option<Span>)>,
     builtin_attrs: Vec<(Ident, ParentScope<'a>)>,
     /// `derive(Copy)` marks items they are applied to so they are treated specially later.
     /// Derive macros cannot modify the item themselves and have to store the markers in the global

compiler/rustc_resolve/src/macros.rs

@@ -277,6 +277,14 @@ impl<'a, 'tcx> ResolverExpand for Resolver<'a, 'tcx> {
         let parent_scope = &ParentScope { derives, ..parent_scope };
         let supports_macro_expansion = invoc.fragment_kind.supports_macro_expansion();
         let node_id = invoc.expansion_data.lint_node_id;
+        let sugg_span = match &invoc.kind {
+            InvocationKind::Attr { item: Annotatable::Item(item), .. }
+                if !item.span.from_expansion() =>
+            {
+                Some(item.span.shrink_to_lo())
+            }
+            _ => None,
+        };
         let (ext, res) = self.smart_resolve_macro_path(
             path,
             kind,
@@ -286,6 +294,7 @@ impl<'a, 'tcx> ResolverExpand for Resolver<'a, 'tcx> {
             node_id,
             force,
             soft_custom_inner_attributes_gate(path, invoc),
+            sugg_span,
         )?;
 
         let span = invoc.span();
@@ -370,6 +379,7 @@ impl<'a, 'tcx> ResolverExpand for Resolver<'a, 'tcx> {
                         &parent_scope,
                         true,
                         force,
+                        None,
                     ) {
                         Ok((Some(ext), _)) => {
                             if !ext.helper_attrs.is_empty() {
@@ -486,14 +496,15 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         node_id: NodeId,
         force: bool,
         soft_custom_inner_attributes_gate: bool,
+        sugg_span: Option<Span>,
     ) -> Result<(Lrc<SyntaxExtension>, Res), Indeterminate> {
-        let (ext, res) = match self.resolve_macro_path(path, Some(kind), parent_scope, true, force)
-        {
-            Ok((Some(ext), res)) => (ext, res),
-            Ok((None, res)) => (self.dummy_ext(kind), res),
-            Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
-            Err(Determinacy::Undetermined) => return Err(Indeterminate),
-        };
+        let (ext, res) =
+            match self.resolve_macro_path(path, Some(kind), parent_scope, true, force, sugg_span) {
+                Ok((Some(ext), res)) => (ext, res),
+                Ok((None, res)) => (self.dummy_ext(kind), res),
+                Err(Determinacy::Determined) => (self.dummy_ext(kind), Res::Err),
+                Err(Determinacy::Undetermined) => return Err(Indeterminate),
+            };
 
         // Report errors for the resolved macro.
         for segment in &path.segments {
@@ -603,6 +614,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         parent_scope: &ParentScope<'a>,
         trace: bool,
         force: bool,
+        sugg_span: Option<Span>,
     ) -> Result<(Option<Lrc<SyntaxExtension>>, Res), Determinacy> {
         let path_span = path.span;
         let mut path = Segment::from_path(path);
@@ -634,6 +646,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     kind,
                     *parent_scope,
                     res.ok(),
+                    sugg_span,
                 ));
             }
 
@@ -660,6 +673,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     kind,
                     *parent_scope,
                     binding.ok(),
+                    sugg_span,
                 ));
             }
 
@@ -706,7 +720,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         };
 
         let macro_resolutions = mem::take(&mut self.multi_segment_macro_resolutions);
-        for (mut path, path_span, kind, parent_scope, initial_res) in macro_resolutions {
+        for (mut path, path_span, kind, parent_scope, initial_res, _sugg_span) in macro_resolutions
+        {
             // FIXME: Path resolution will ICE if segment IDs present.
             for seg in &mut path {
                 seg.id = None;
@@ -731,9 +746,13 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             let exclamation_span = sm.next_point(span);
                             suggestion = Some((
                                 vec![(exclamation_span, "".to_string())],
-                                    format!("{} is not a macro, but a {}, try to remove `!`", Segment::names_to_string(&path), partial_res.base_res().descr()),
-                                    Applicability::MaybeIncorrect
-                                ));
+                                format!(
+                                    "{} is not a macro, but a {}, try to remove `!`",
+                                    Segment::names_to_string(&path),
+                                    partial_res.base_res().descr(),
+                                ),
+                                Applicability::MaybeIncorrect,
+                            ));
                         }
                         (span, label)
                     } else {
@@ -756,7 +775,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
 
         let macro_resolutions = mem::take(&mut self.single_segment_macro_resolutions);
-        for (ident, kind, parent_scope, initial_binding) in macro_resolutions {
+        for (ident, kind, parent_scope, initial_binding, sugg_span) in macro_resolutions {
             match self.early_resolve_ident_in_lexical_scope(
                 ident,
                 ScopeSet::Macro(kind),
@@ -789,9 +808,15 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 }
                 Err(..) => {
                     let expected = kind.descr_expected();
-                    let msg = format!("cannot find {} `{}` in this scope", expected, ident);
+                    let msg = format!("cannot find {expected} `{ident}` in this scope");
                     let mut err = self.tcx.sess.struct_span_err(ident.span, &msg);
-                    self.unresolved_macro_suggestions(&mut err, kind, &parent_scope, ident);
+                    self.unresolved_macro_suggestions(
+                        &mut err,
+                        kind,
+                        &parent_scope,
+                        ident,
+                        sugg_span,
+                    );
                     err.emit();
                 }
             }

tests/ui-fulldeps/session-diagnostic/diagnostic-derive.stderr

@@ -613,18 +613,32 @@ error: cannot find attribute `multipart_suggestion` in this scope
    |
 LL | #[multipart_suggestion(no_crate_suggestion)]
    |   ^^^^^^^^^^^^^^^^^^^^
+   |
+help: `multipart_suggestion` is an attribute that can be used by the derive macro `Subdiagnostic`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Subdiagnostic)]
+LL | struct MultipartSuggestion {
+   |
 
 error: cannot find attribute `multipart_suggestion` in this scope
   --> $DIR/diagnostic-derive.rs:642:3
    |
 LL | #[multipart_suggestion()]
    |   ^^^^^^^^^^^^^^^^^^^^
+   |
+help: `multipart_suggestion` is an attribute that can be used by the derive macro `Subdiagnostic`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Subdiagnostic)]
+LL | struct MultipartSuggestion {
+   |
 
 error: cannot find attribute `multipart_suggestion` in this scope
   --> $DIR/diagnostic-derive.rs:646:7
    |
 LL |     #[multipart_suggestion(no_crate_suggestion)]
    |       ^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `multipart_suggestion` is an attribute that can be used by the derive macro `Subdiagnostic`, you might be missing a `derive` attribute
 
 error[E0425]: cannot find value `nonsense` in module `crate::fluent_generated`
   --> $DIR/diagnostic-derive.rs:69:8

tests/ui/enum/suggest-default-attribute.stderr

@@ -7,7 +7,7 @@ LL |     #[default]
 help: consider adding a derive
    |
 LL + #[derive(Default)]
-LL ~ pub enum Test {
+LL | pub enum Test {
    |
 
 error: aborting due to previous error