in lib/src/file.dart [371:387]
SourceSpan union(SourceSpan other) {
if (other is! FileSpan) return super.union(other);
final span = expand(other);
if (other is _FileSpan) {
if (_start > other._end || other._start > _end) {
throw ArgumentError('Spans $this and $other are disjoint.');
}
} else {
if (_start > other.end.offset || other.start.offset > _end) {
throw ArgumentError('Spans $this and $other are disjoint.');
}
}
return span;
}