Singleton classes can't have subclasses.

brixen · brixen · commit 20938ee86dcb · 2016-04-24T21:13:04.000-07:00
diff --git a/machine/builtin/module.cpp b/machine/builtin/module.cpp
@@ -490,10 +490,13 @@ namespace rubinius {
   }
 
   Object* Module::track_subclass(STATE, Module* mod) {
+    if(try_as<SingletonClass>(mod)) return cNil;
+
     if(hierarchy_subclasses()->nil_p()) {
       hierarchy_subclasses(state, Array::create(state, 4));
     }
     hierarchy_subclasses()->append(state, WeakRef::create(state, mod));
+
     return cNil;
   }
 

Original file line number	Diff line number	Diff line change
`@@ -490,10 +490,13 @@ namespace rubinius {`
`490`	`490`	`}`
`491`	`491`
`492`	`492`	`Object* Module::track_subclass(STATE, Module* mod) {`
	`493`	`+ if(try_as<SingletonClass>(mod)) return cNil;`
	`494`	`+`
`493`	`495`	`if(hierarchy_subclasses()->nil_p()) {`
`494`	`496`	`hierarchy_subclasses(state, Array::create(state, 4));`
`495`	`497`	`}`
`496`	`498`	`hierarchy_subclasses()->append(state, WeakRef::create(state, mod));`
	`499`	`+`
`497`	`500`	`return cNil;`
`498`	`501`	`}`
`499`	`502`