Couldn't find whether it was brought up earlier, but it seems that empty? predicate is broken for transient collections
The workaround is to use (zero? (count (transient ...))) check instead.
Cause: empty? is based on seqability, which transients don't implement.
Proposed Add a branch to empty? for counted? colls. Transients implement Counted so gain support via this branch. Other colls that are counted are faster. Seq branch continues to work for seqs.
|p||0.72 ms||0.08 ms||much faster when empty|
|p1||0.15 ms||0.13 ms||slightly faster when not empty|
|t||error||0.19 ms||no longer errors|
|t1||error||0.20 ms||no longer errors|
Not sure if doc string should be tweaked to be more generic, particularly the "same as (not (seq coll))" which is now only true for Seqable but not Counted. I think the advise to use (seq coll) for seq checks is still good there.
I did a skim for other types that are Counted but not seqs/Seqable and didn't find much other than internal things like ChunkBuffer. Many are both and would thus use the counted path instead (all the persistent colls for example and any kind of IndexedSeq).
I guess another option would be just to fully switch empty? to be about (zero? (bounded-count 1 coll)) and lean on count's polymorphism completely.