code: public static GenericsType buildWildcardType(final ClassNode... types) {
          ClassNode base = ClassHelper.makeWithoutCaching("?");
          GenericsType gt = new GenericsType(base, types, null);
          gt.setWildcard(true);
          return gt;
      }
docs: Generates a wildcard generic type in order to be used for checks against class nodes.
  See {@link GenericsType#isCompatibleWith(org.codehaus.groovy.ast.ClassNode)}.
  
  @param types the type to be used as the wildcard upper bound
  @return a wildcard generics type