Ruby: Add MkModuleObject as API node for a module/class

ruby/ql/lib/codeql/ruby/ApiGraphs.qll

@@ -601,7 +601,9 @@ module API {
       /** A use of an API member at the node `nd`. */
       MkUse(DataFlow::Node nd) { isUse(nd) } or
       /** A value that escapes into an external library at the node `nd` */
-      MkDef(DataFlow::Node nd) { isDef(nd) }
+      MkDef(DataFlow::Node nd) { isDef(nd) } or
+      /** A module object seen as a use node. */
+      MkModuleObject(DataFlow::ModuleNode mod)
 
     private string resolveTopLevel(ConstantReadAccess read) {
       result = read.getModule().getQualifiedName() and
@@ -684,7 +686,14 @@ module API {
      * Holds if `ref` is a use of node `nd`.
      */
     cached
-    predicate use(TApiNode nd, DataFlow::Node ref) { nd = MkUse(ref) }
+    predicate use(TApiNode nd, DataFlow::Node ref) {
+      nd = MkUse(ref)
+      or
+      exists(DataFlow::ModuleNode mod |
+        nd = MkModuleObject(mod) and
+        ref = mod.getAnImmediateReference()
+      )
+    }
 
     /**
      * Holds if `rhs` is a RHS of node `nd`.
@@ -802,6 +811,14 @@ module API {
       trackUseNode(use).flowsTo(call.getReceiver())
     }
 
+    /**
+     * Holds if `superclass` is the superclass of `mod`.
+     */
+    pragma[nomagic]
+    private predicate superclassNode(DataFlow::ModuleNode mod, DataFlow::Node superclass) {
+      superclass.asExpr().getExpr() = mod.getADeclaration().(ClassDeclaration).getSuperclassExpr()
+    }
+
     /**
      * Holds if there is an edge from `pred` to `succ` in the API graph that is labeled with `lbl`.
      */
@@ -830,14 +847,11 @@ module API {
         defStep(lbl, trackDefNode(predNode), succNode)
       )
       or
-      // `pred` is a use of class A
-      // `succ` is a use of class B
-      // there exists a class declaration B < A
-      exists(ClassDeclaration c, DataFlow::Node a, DataFlow::Node b |
-        use(pred, a) and
-        use(succ, b) and
-        b.asExpr().getExpr().(ConstantReadAccess).getAQualifiedName() = c.getAQualifiedName() and
-        pragma[only_bind_into](c).getSuperclassExpr() = a.asExpr().getExpr() and
+      exists(DataFlow::Node predNode, DataFlow::Node superclassNode, DataFlow::ModuleNode mod |
+        use(pred, predNode) and
+        trackUseNode(predNode).flowsTo(superclassNode) and
+        superclassNode(mod, superclassNode) and
+        succ = MkModuleObject(mod) and
         lbl = Label::subclass()
       )
       or