Ruby: go to local source in load-store steps

Author: asgerf

ruby/ql/lib/codeql/ruby/typetracking/TypeTracker.qll

@@ -171,7 +171,7 @@ private module Cached {
     )
     or
     exists(TypeTrackerContent loadContent, TypeTrackerContent storeContent |
-      basicLoadStoreStep(nodeFrom, nodeTo, loadContent, storeContent) and
+      flowsToLoadStoreStep(nodeFrom, nodeTo, loadContent, storeContent) and
       summary = LoadStoreStep(loadContent, storeContent)
     )
   }
@@ -218,6 +218,18 @@ private predicate flowsToStoreStep(
   exists(Node obj | nodeTo.flowsTo(obj) and basicStoreStep(nodeFrom, obj, content))
 }
 
+/**
+ * Holds if `loadContent` is loaded from `nodeFrom` and written to `storeContent` of `nodeTo`.
+ */
+predicate flowsToLoadStoreStep(
+  Node nodeFrom, TypeTrackingNode nodeTo, TypeTrackerContent loadContent,
+  TypeTrackerContent storeContent
+) {
+  exists(Node obj |
+    nodeTo.flowsTo(obj) and basicLoadStoreStep(nodeFrom, obj, loadContent, storeContent)
+  )
+}
+
 /**
  * INTERNAL: Use `TypeTracker` or `TypeBackTracker` instead.
  *