slurs/accidentals across barlines

[David Bobroff]

The following code illustrates what I believe is a bug:

\version "2.5.30"

\score {
  \relative c'' {
    \key as \major
    a1-(
    as-)
  }
}


The output looks like a pair of tied 'a's but is, in fact a slur from an
a to an a-flat.  To be sure, LilyPond *does* make a visual difference
between slurs and ties, but when reading music the output from the above
will not clearly communicate that the second note is an a-flat.  I think
LilyPond should recognize such situations and force a courtesy
accidental.

-David