immutable set that preserves order

[scabug]

see #8184

Would be nice to have an efficient collection.immutable.LinkedSet analogous to mutable.LinkedHashSet in that it preserves ordering

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-8234?orig=1
Reporter: @adriaanm
See #8184

[scabug]

@Ichoran said:
How nice would it be? The naive implementations have horrible runtime performance, and the ones with less horrible performance are still not great and are not terribly simple. (You basically need to create a set with two underlying sets, one HashSet and one SortedSet, where the latter keeps track of insertion order.)

[SethTisue]

@Ichoran did this happen in strawman?

[jvican]

(I think having this would be really nice.)

[SethTisue]

2.13 adds SeqMap (and implementations such as VectorMap)

no SeqSet was added at the same time, for no obvious reason; ticket is scala/scala-library-next#22

I'm going to close this regardless, since the scala-library-next ticket exists (and since scala/bug is generally for actual bugs)