JavaScript: Improve API-graph support for function-style classes.

Author: Max Schaefer

javascript/ql/src/semmle/javascript/ApiGraphs.qll

@@ -547,7 +547,11 @@ module API {
         ref = DataFlow::moduleImport(m)
       )
       or
-      exists(DataFlow::ClassNode cls | nd = MkClassInstance(cls) | ref = cls.getAReceiverNode())
+      exists(DataFlow::ClassNode cls | nd = MkClassInstance(cls) |
+        ref = cls.getAReceiverNode()
+        or
+        ref = cls.(DataFlow::ClassNode::FunctionStyleClass).getAPrototypeReference()
+      )
       or
       nd = MkUse(ref)
       or

javascript/ql/test/ApiGraphs/classes/classes.js

@@ -20,4 +20,8 @@ MyOtherStream.prototype.write = function (data) { /* use (instance (member MyOth
     return this;
 };
 
+MyOtherStream.prototype.instanceProp = 1; /* def (member instanceProp (instance (member MyOtherStream (member exports (module classes))))) */
+
+MyOtherStream.classProp = 1; /* def (member classProp (member MyOtherStream (member exports (module classes)))) */
+
 module.exports.MyOtherStream = MyOtherStream;