Lilypond bug?

[stefano cucuzzella]

Hello,

how could you put a Trillspan under a Music line? For example if the bottom voice from a polyphony have a trill.

\version "2.12.2"

\relative {

\time 3/8

<< { <d' e>8^\markup {arco} s8 s4 s4 s4 s4 s4 s4 s4} \\

{f,4^\startTrillSpan\> ~ 

\stemUp

f ~ f ~ f ~ f ~ f ~ f ~ \afterGrace f\!( {e16[ f)]} } >>

\mark \default

f'8 r

}