code: static boolean isBivariantType(JSType type) {
      ObjectType objType = type.toObjectType();
      return objType != null
          // && objType.isNativeObjectType()
          && BIVARIANT_TYPES.contains(objType.getReferenceName());
    }
docs: Determines if the supplied type should be checked as a bivariant
  templatized type rather the standard invariant templatized type
  rules.