Record derive helper attributes, resolve them in IDE layer

crates/ide/src/doc_links.rs

@@ -190,7 +190,8 @@ pub(crate) fn resolve_doc_path_for_def(
         | Definition::SelfType(_)
         | Definition::Local(_)
         | Definition::GenericParam(_)
-        | Definition::Label(_) => None,
+        | Definition::Label(_)
+        | Definition::DeriveHelper(_) => None,
     }
     .map(Definition::from)
 }
@@ -515,7 +516,8 @@ fn filename_and_frag_for_def(
         | Definition::GenericParam(_)
         | Definition::Label(_)
         | Definition::BuiltinAttr(_)
-        | Definition::ToolModule(_) => return None,
+        | Definition::ToolModule(_)
+        | Definition::DeriveHelper(_) => return None,
     };
 
     Some((def, res, None))

crates/ide/src/hover/render.rs

@@ -370,6 +370,8 @@ pub(super) fn definition(
         // FIXME: We should be able to show more info about these
         Definition::BuiltinAttr(it) => return render_builtin_attr(db, it),
         Definition::ToolModule(it) => return Some(Markup::fenced_block(&it.name(db))),
+        // FIXME: it.name(db)
+        Definition::DeriveHelper(_it) => ("derive-helper".to_owned(), None),
     };
 
     let docs = match config.documentation {

crates/ide/src/navigation_target.rs

@@ -196,6 +196,8 @@ impl TryToNav for Definition {
             Definition::BuiltinType(_) => None,
             Definition::ToolModule(_) => None,
             Definition::BuiltinAttr(_) => None,
+            // FIXME: The focus range should be set to the helper declaration
+            Definition::DeriveHelper(it) => it.derive().try_to_nav(db),
         }
     }
 }

crates/ide/src/signature_help.rs

@@ -237,7 +237,8 @@ fn signature_help_for_generics(
             | hir::PathResolution::Local(_)
             | hir::PathResolution::TypeParam(_)
             | hir::PathResolution::ConstParam(_)
-            | hir::PathResolution::SelfType(_) => return None,
+            | hir::PathResolution::SelfType(_)
+            | hir::PathResolution::DeriveHelper(_) => return None,
         };
 
         generic_def

crates/ide/src/syntax_highlighting.rs

@@ -107,6 +107,7 @@ pub struct HlRange {
 // builtinType:: Emitted for builtin types like `u32`, `str` and `f32`.
 // comment:: Emitted for comments.
 // constParameter:: Emitted for const parameters.
+// deriveHelper:: Emitted for derive helper attributes.
 // enumMember:: Emitted for enum variants.
 // generic:: Emitted for generic tokens that have no mapping.
 // keyword:: Emitted for keywords.

crates/ide/src/syntax_highlighting/highlight.rs

@@ -472,6 +472,7 @@ fn highlight_def(
         Definition::Label(_) => Highlight::new(HlTag::Symbol(SymbolKind::Label)),
         Definition::BuiltinAttr(_) => Highlight::new(HlTag::Symbol(SymbolKind::BuiltinAttr)),
         Definition::ToolModule(_) => Highlight::new(HlTag::Symbol(SymbolKind::ToolModule)),
+        Definition::DeriveHelper(_) => Highlight::new(HlTag::Symbol(SymbolKind::DeriveHelper)),
     };
 
     let def_crate = def.krate(db);

crates/ide/src/syntax_highlighting/inject.rs

@@ -270,6 +270,7 @@ fn module_def_to_hl_tag(def: Definition) -> HlTag {
         Definition::Label(_) => SymbolKind::Label,
         Definition::BuiltinAttr(_) => SymbolKind::BuiltinAttr,
         Definition::ToolModule(_) => SymbolKind::ToolModule,
+        Definition::DeriveHelper(_) => SymbolKind::DeriveHelper,
     };
     HlTag::Symbol(symbol)
 }

crates/ide/src/syntax_highlighting/tags.rs

@@ -134,6 +134,7 @@ impl HlTag {
                 SymbolKind::Const => "constant",
                 SymbolKind::ConstParam => "const_param",
                 SymbolKind::Derive => "derive",
+                SymbolKind::DeriveHelper => "derive_helper",
                 SymbolKind::Enum => "enum",
                 SymbolKind::Field => "field",
                 SymbolKind::Function => "function",