+ # lookup vt to build layout with
+ var vts = new HashMap[MClass, Set[MVirtualTypeProp]]
+ for mclass in mclasses do
+ vts[mclass] = new HashSet[MVirtualTypeProp]
+ for mprop in self.mainmodule.properties(mclass) do
+ if mprop isa MVirtualTypeProp then
+ vts[mclass].add(mprop)
+ end
+ end
+ end
+