Drawing systems...ERROR: In procedure min: ERROR: Wrong type: lilyvartmpbh

[Nick Payne]

This code used to work for me about a year ago, but when I try to build 
it using 2.13.60, I get the weird error shown in the console log output 
at the bottom. Is this a bug or not? I'm running 2.13.60 on Ubuntu 10.04 
amd64.

%===================================
\version "2.13.60"

% e.g. \spanbox #-8 #'(-1 . -1)
spanbox = #(define-music-function (parser location yval shorten) 
(number? pair?) #{
    \once \override TextSpanner #'style = #'line
    \once \override TextSpanner #'bound-details #'left #'text = \markup 
{ \draw-line #'(0 . $yval) }
    \once \override TextSpanner #'bound-details #'right #'text = 
\markup { \draw-line #'(0 . $yval) }
    \once \override TextSpanner #'bound-details #'left #'padding = 
#(car $shorten)
    \once \override TextSpanner #'bound-details #'right #'padding = 
#(cdr $shorten)
#})

\relative c' {
    \spanbox #-8 #'(-1 . -1) c4\startTextSpan c c c\stopTextSpan
}
%===================================

Processing `/home/nick/lilypond/examples/box.ly'
Parsing...
Interpreting music...
Preprocessing graphical objects...
Finding the ideal number of pages...
Fitting music on 1 page...
Drawing systems...ERROR: In procedure min:
ERROR: Wrong type: lilyvartmpbh