#4583 Odd interaction between slur and tuplet number

[Simon Albrecht]

Reported by Daniel Rosen in http://lists.gnu.org/archive/html/bug-lilypond/2015-08/msg00140.html:

.avoid-slur = #'outside
here moves the TupletNumber in quite a peculiar manner, where it should have stayed just in the default position.

:::Lilypond
\version "2.19.25"
\relative c'' {
  \tupletUp
  \override TupletNumber.avoid-slur = #'outside
  \tuplet 3/2 { b8( b b) }
}