+ /// If the given `DefId` describes an item belonging to a trait,
+ /// returns the `DefId` of the trait that the trait item belongs to;
+ /// otherwise, returns `None`.
+ pub fn trait_of_item(self, def_id: DefId) -> Option<DefId> {
+ if let DefKind::AssocConst | DefKind::AssocFn | DefKind::AssocTy = self.def_kind(def_id) {
+ let parent = self.parent(def_id);
+ if let DefKind::Trait | DefKind::TraitAlias = self.def_kind(parent) {
+ return Some(parent);
+ }
+ }
+ None
+ }
+