There was a lot of debate regarding possible improvements, but it didn't make it into 2.10.

The issue basically revolves around getting rid of the mutable field in favor of an immutable approach.

Example with default configuration:

Array(1,2,3).par.map(...)

Current tasksupport API:

val array = Array(1,2,3).par
array.tasksupport = otherTaskSupport
array.map(...)

An additional issue is that this API also breaks the “flow” of operations.

The proposed improvements are along the lines of something like:

Array(1,2,3).parWith(otherTaskSupport).map(...)

Considering that the library has already shipped with 2.10, the current API probably needs to be deprecated before it can be removed.

Old discussion: https://groups.google.com/d/topic/scala-internals/lzxVlexkqEg/discussion

Old pull request: scala/scala#930