scala/scala — pull request #2579 by vigdorchik (2013-05-22 16:03:09+00:00)
Title: SI-7502 removing non-existent element from ListMap leaves it unchaged.

Current imperative version constructs a new ListMap regardless of
the fact the map doesn't contain the element. Replace it with the
tail-recursive variant that conserves. Also replace some usages with
the invariant now held.