[Bioperl-l] Bio::SeqFeature::Gene::Exon throws exception when encountering split location (Bio::Location::Split)

[Mark Johnson]

    This bit in Bio::SeqFeature::Gene::Exon is causing me some
problems trying to extend Bio::Tools::Glimmer to handle 'wraparound'
genes (circular genomes):

sub location {
   my ($self,$value) = @_;

   if(defined($value) && $value->isa('Bio::Location::SplitLocationI')) {
       $self->throw("split or compound location is not allowed ".
                    "for an object of type " . ref($self));
   }
   return $self->SUPER::location($value);
}

    That seems to be there all the way back to the initial revision
(checked in by Hilmar).  I presume it's there because of code like
this ( from the seq() method in Bio::SeqFeature::Generic):

# assumming our seq object is sensible, it should not have to yank
# the entire sequence out here.

my $seq = $self->{'_gsf_seq'}->trunc($self->start(), $self->end());

    That's not going to work too well with a feature that has a
Bio::Location::Split location.  Fixing it up seems straightforward, if
a bit hackish.  Something like:

my $seq;

if (ref($self->location()) eq 'Bio::Location::Split')) {
    my $seqstring;
    my @sublocs = $self->location()->sub_Location();

    foreach my $subloc (@sublocs) {
        $seqstring .= $self->{'_gsf_seq'}->trunc($subloc->start(),
$subloc->end())->seq();
    }

    my $seq = Bio::Seq->new(
                                          -id =>
$self->{'_gsf_seq'}->display_id(),
                                          -seq => $seqstring
                                         );
}
else {
    $seq = $self->{'_gsf_seq'}->trunc($self->start(), $self->end());
}

    I don't see any companion to trunc() in Bio::PrimarySeqI for
joining sequences.  A join() would be handy, and make the above
cleaner.
    Comments, suggestions, rotten fruit?