Rests with stem tremolo cause LilyPond to fail silently

[Trevor Bača]

Hi,

While "c4:32" correctly expresses a quarter note stem tremolo slashes,
typing (badly-formed) "r4:32" probably only happens when a user is editing
a source file and changes a note to a rest without regard for the stem
tremolo suffix.

However, rather than raising some type of error or warning, Lily fails
silently on this type of badly-formed construction.

Rests shorter than the duration of a whole note cause LilyPond to fail
silently at system drawing:

%%% BEGIN 1 %%%

\version "2.19.83"
\new Staff { r4:32 }

%%% END %%%

Output:

GNU LilyPond 2.19.83
Processing `test.ly'
Parsing...
Interpreting music...
Preprocessing graphical objects...
Finding the ideal number of pages...
Fitting music on 1 page...
Drawing systems...
*[no more output]*

Longer rests cause Lily to fail even more laconically:

%%% BEGIN 2 %%%

\version "2.19.83"
\new Staff { r1:32 }

%%% END %%%

GNU LilyPond 2.19.83
Processing `test.ly'
Parsing...
Interpreting music...
Preprocessing graphical objects...
*[no more output]*


Rather than failing silently, Lily should raise an error or warning:
imagine a large input file failing for no apparent reason and then having
to bisect the entire thing find a single instance of something like
"r4:32".

Thanks,

Trevor.

-- 
Trevor Bača
www.trevorbaca.com
soundcloud.com/trevorbaca