scala/scala — pull request #1097 by rklaehn (2012-08-09 02:07:32+00:00)
Title: Si 6198

Create a HashSet1 instead of a HashSetCollision1 if the list of colliding keys has only one entry.

To do this efficiently it was necessary to change ListSet so that head and tail are both O(1) with low overhead.

Based on 2.10.x this time.