private void noteCyclic(DiagnosticPosition pos, ClassSymbol c) {
        log.error(pos, "cyclic.inheritance", c);
        for (List<Type> l=types.interfaces(c.type); l.nonEmpty(); l=l.tail)
            l.head = types.createErrorType((ClassSymbol)l.head.tsym, Type.noType);
        Type st = types.supertype(c.type);
        if (st.tag == CLASS)
            ((ClassType)c.type).supertype_field = types.createErrorType((ClassSymbol)st.tsym, Type.noType);
        c.type = types.createErrorType(c, c.type);
        c.flags_field |= ACYCLIC;
    }