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)]
   |
```

Mitigate #47608.

Author: estebank

compiler/rustc_resolve/src/diagnostics.rs

@@ -1418,6 +1418,33 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         krate: &Crate,
         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),

compiler/rustc_resolve/src/ident.rs

@@ -463,6 +463,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                                 true,
                                 force,
                                 ignore_import,
+                                None,
                             ) {
                                 Ok((Some(ext), _)) => {
                                     if ext.helper_attrs.contains(&ident.name) {

compiler/rustc_resolve/src/late.rs

@@ -4406,7 +4406,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, '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, None)
+                self.r.resolve_macro_path(&path, None, &self.parent_scope, false, false, None, None)
             {
                 return Ok(Some(PartialRes::new(res)));
             }

compiler/rustc_resolve/src/macros.rs

@@ -396,6 +396,7 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
                         true,
                         force,
                         None,
+                        None,
                     ) {
                         Ok((Some(ext), _)) => {
                             if !ext.helper_attrs.is_empty() {
@@ -693,6 +694,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         trace: bool,
         force: bool,
         ignore_import: Option<Import<'ra>>,
+        suggestion_span: Option<Span>,
     ) -> Result<(Option<Arc<SyntaxExtension>>, Res), Determinacy> {
         self.resolve_macro_or_delegation_path(
             path,
@@ -703,7 +705,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             None,
             None,
             ignore_import,
-            None,
+            suggestion_span,
         )
     }
 

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

@@ -583,18 +583,30 @@ 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)]
+   |
 
 error: cannot find attribute `multipart_suggestion` in this scope
   --> $DIR/diagnostic-derive.rs:647:3
    |
 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)]
+   |
 
 error: cannot find attribute `multipart_suggestion` in this scope
   --> $DIR/diagnostic-derive.rs:651:7
    |
 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:75:8

tests/ui/macros/auxiliary/serde.rs

@@ -0,0 +1,19 @@
+//@ force-host
+//@ no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro_quote)]
+
+extern crate proc_macro;
+
+use proc_macro::*;
+
+#[proc_macro_derive(Serialize, attributes(serde))]
+pub fn serialize(ts: TokenStream) -> TokenStream {
+    quote!{}
+}
+
+#[proc_macro_derive(Deserialize, attributes(serde))]
+pub fn deserialize(ts: TokenStream) -> TokenStream {
+    quote!{}
+}

tests/ui/macros/missing-derive-1.rs

@@ -0,0 +1,33 @@
+//@aux-build:serde.rs
+
+// derive macros imported and used
+
+extern crate serde;
+use serde::{Serialize, Deserialize};
+
+#[serde(untagged)] //~ ERROR cannot find attribute `serde`
+enum A { //~ HELP `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`
+    A,
+    B,
+}
+
+enum B { //~ HELP `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`
+    A,
+    #[serde(untagged)] //~ ERROR cannot find attribute `serde`
+    B,
+}
+
+enum C {
+    A,
+    #[sede(untagged)] //~ ERROR cannot find attribute `sede`
+    B, //~^ HELP the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute
+}
+
+#[derive(Serialize, Deserialize)]
+#[serde(untagged)]
+enum D {
+    A,
+    B,
+}
+
+fn main() {}

tests/ui/macros/missing-derive-1.stderr

@@ -0,0 +1,47 @@
+error: cannot find attribute `serde` in this scope
+  --> $DIR/missing-derive-1.rs:8:3
+   |
+LL | #[serde(untagged)]
+   |   ^^^^^
+   |
+note: `serde` is imported here, but it is a crate, not an attribute
+  --> $DIR/missing-derive-1.rs:5:1
+   |
+LL | extern crate serde;
+   | ^^^^^^^^^^^^^^^^^^^
+help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Serialize, Deserialize)]
+LL | enum A {
+   |
+
+error: cannot find attribute `serde` in this scope
+  --> $DIR/missing-derive-1.rs:16:7
+   |
+LL |     #[serde(untagged)]
+   |       ^^^^^
+   |
+note: `serde` is imported here, but it is a crate, not an attribute
+  --> $DIR/missing-derive-1.rs:5:1
+   |
+LL | extern crate serde;
+   | ^^^^^^^^^^^^^^^^^^^
+help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Serialize, Deserialize)]
+LL | enum B {
+   |
+
+error: cannot find attribute `sede` in this scope
+  --> $DIR/missing-derive-1.rs:22:7
+   |
+LL |     #[sede(untagged)]
+   |       ^^^^
+   |
+help: the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute
+   |
+LL |     #[serde(untagged)]
+   |       ~~~~~
+
+error: aborting due to 3 previous errors
+

tests/ui/macros/missing-derive-2.rs

@@ -0,0 +1,26 @@
+//@aux-build:serde.rs
+
+// derive macros imported but unused
+
+extern crate serde;
+use serde::{Serialize, Deserialize};
+
+#[serde(untagged)] //~ ERROR cannot find attribute `serde`
+enum A { //~ HELP `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`
+    A,
+    B,
+}
+
+enum B { //~ HELP `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`
+    A,
+    #[serde(untagged)] //~ ERROR cannot find attribute `serde`
+    B,
+}
+
+enum C {
+    A,
+    #[sede(untagged)] //~ ERROR cannot find attribute `sede`
+    B, //~^ HELP the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute
+}
+
+fn main() {}

tests/ui/macros/missing-derive-2.stderr

@@ -0,0 +1,47 @@
+error: cannot find attribute `sede` in this scope
+  --> $DIR/missing-derive-2.rs:22:7
+   |
+LL |     #[sede(untagged)]
+   |       ^^^^
+   |
+help: the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute
+   |
+LL |     #[serde(untagged)]
+   |       ~~~~~
+
+error: cannot find attribute `serde` in this scope
+  --> $DIR/missing-derive-2.rs:16:7
+   |
+LL |     #[serde(untagged)]
+   |       ^^^^^
+   |
+note: `serde` is imported here, but it is a crate, not an attribute
+  --> $DIR/missing-derive-2.rs:5:1
+   |
+LL | extern crate serde;
+   | ^^^^^^^^^^^^^^^^^^^
+help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Serialize, Deserialize)]
+LL | enum B {
+   |
+
+error: cannot find attribute `serde` in this scope
+  --> $DIR/missing-derive-2.rs:8:3
+   |
+LL | #[serde(untagged)]
+   |   ^^^^^
+   |
+note: `serde` is imported here, but it is a crate, not an attribute
+  --> $DIR/missing-derive-2.rs:5:1
+   |
+LL | extern crate serde;
+   | ^^^^^^^^^^^^^^^^^^^
+help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute
+   |
+LL + #[derive(Serialize, Deserialize)]
+LL | enum A {
+   |
+
+error: aborting due to 3 previous errors
+