*  @param t        The type referred to.
     *  @returns        True if the check completed on all attributed classes
     */
    private boolean checkNonCyclicInternal(DiagnosticPosition pos, Type t) {
        boolean complete = true; // was the check complete?
        //- System.err.println("checkNonCyclicInternal("+t+");");//DEBUG
        Symbol c = t.tsym;
        if ((c.flags_field & ACYCLIC) != 0) return true;

        if ((c.flags_field & LOCKED) != 0) {
            noteCyclic(pos, (ClassSymbol)c);
        } else if (!c.type.isErroneous()) {
            try {
                c.flags_field |= LOCKED;
                if (c.type.tag == CLASS) {
                    ClassType clazz = (ClassType)c.type;
                    if (clazz.interfaces_field != null)
                        for (List<Type> l=clazz.interfaces_field; l.nonEmpty(); l=l.tail)
                            complete &= checkNonCyclicInternal(pos, l.head);
                    if (clazz.supertype_field != null) {
                        Type st = clazz.supertype_field;
                        if (st != null && st.tag == CLASS)
                            complete &= checkNonCyclicInternal(pos, st);
                    }
                    if (c.owner.kind == TYP)
                        complete &= checkNonCyclicInternal(pos, c.owner.type);
                }
            } finally {
                c.flags_field &= ~LOCKED;
            }
        }
        if (complete)
            complete = ((c.flags_field & UNATTRIBUTED) == 0) && c.completer == null;
        if (complete) c.flags_field |= ACYCLIC;
        return complete;
    }