fn tyi (w :&World, x :Q) -> Ret<Q> {
    let x = input_stream_designator (w, x)?;
    if let Node::Stream(s) = &mut *x.clone().lock().unwrap() {
        //                                  ^^^^^^^
        //                                  Trouble
        if let Some(read) = &s.read {
            if let Some(la) = s.clone().lookahead {
                s.lookahead = None;
                Ok(la.clone()) }
            else {
                //
                // The lock() above must be droped here. How?
                //
                // Otherwise flush will dead lock
                //
                flush (w, x.clone())?;
                let buf = &mut[0 as u8];
                match read.lock().unwrap().read(buf) {
                    Ok(1) =>
                        Ok(makchar (w, buf[0] as char)),
                    Ok(0) =>
                        Ok(w.u.nil.clone()),
                    _ =>
                        error (w, "I/O Error", x.clone()) } } }
        else {
            error (w, "Stream not fit for input", x.clone()) }}
    else {
        error (w, "Not a stream", x.clone()) }}