Support resolution of #[macro_use] extern crate

crates/ra_syntax/src/ast/generated.rs

@@ -934,6 +934,7 @@ impl AstNode for ExternCrateItem {
         &self.syntax
     }
 }
+impl ast::AttrsOwner for ExternCrateItem {}
 impl ExternCrateItem {
     pub fn name_ref(&self) -> Option<NameRef> {
         AstChildren::new(&self.syntax).next()

crates/ra_syntax/src/grammar.ron

@@ -669,6 +669,7 @@ Grammar(
             collections: [("use_trees", "UseTree")]
         ),
         "ExternCrateItem": (
+            traits: ["AttrsOwner"],
             options: ["NameRef", "Alias"],
         ),
         "ArgList": (