Re: Issue 1967 in lilypond: Concurrent slurs that start and end at the same moment should not produce a warning

[lilypond]

Comment #19 on issue 1967 by address@hidden: Concurrent slurs that start and  
end at the same moment should not produce a warning
http://code.google.com/p/lilypond/issues/detail?id=1967

I would agree if this occured just with user input.  However, this occurs  
as a result of _output_ from the part combiner.  The part combiner analyses  
the input and decides whether or not it can combine it into a single  
voice.  This decision should not lead to a warning, ever.

Now one could just tack spanner-ids on every spanner, and be done.   
However, that would mean that when the part combiner has simple input as  
the one we have here, it would always create double slurs.  That does not  
seem right.

I think it is correct that we get just a single slur here, but whatever the  
technical reason behind it, it must not be accompanied by a warning.

So while the _current_ summary title is something that does not necessarily  
constitute a regression, we can't have the partcombiner produce warnings in  
the course of its regular operation and input it accepts as valid.

One cure would be to permit concurrent slurs to fold.