copy from upstream #15528 to make branch mergeable

merge commits are not allowed upstream, so I manually copied the changes

crates/ide-db/src/search.rs

@@ -221,7 +221,6 @@ impl Definition {
         }
 
         // def is crate root
-        // FIXME: We don't do searches for crates currently, as a crate does not actually have a single name
         if let &Definition::Module(module) = self {
             if module.is_crate_root() {
                 return SearchScope::reverse_dependencies(db, module.krate());
@@ -400,7 +399,10 @@ impl<'a> FindUsages<'a> {
             match self.def {
                 // special case crate modules as these do not have a proper name
                 Definition::Module(module) if module.is_crate_root() => {
-                    // FIXME: This assumes the crate name is always equal to its display name when it really isn't
+                    // FIXME: This assumes the crate name is always equal to its display name when it
+                    // really isn't
+                    // we should instead look at the dependency edge name and recursively search our way
+                    // up the ancestors
                     let name = module
                         .krate()
                         .display_name(self.sema.db)