*  @param t             The type to be checked.
     */
    Type checkReifiableReferenceType(DiagnosticPosition pos, Type t) {
        if (t.tag != CLASS && t.tag != ARRAY && t.tag != ERROR) {
            return typeTagError(pos,
                                diags.fragment("type.req.class.array"),
                                t);
        } else if (!types.isReifiable(t)) {
            log.error(pos, "illegal.generic.type.for.instof");
            return types.createErrorType(t);
        } else {
            return t;
        }
    }