public static <S extends Declaration,S2 extends S>SymbolReference<S> unsolved(Class<S2> clazz){
  return new SymbolReference(Optional.<S>empty());
}

public static < S extends Declaration , S2 extends S > SymbolReference < S > unsolved ( Class < S2 > clazz ) { return new SymbolReference ( Optional . < S > empty ( ) ) ; }
create an unsolved reference specifying the type of the value expected .
