Imported From: https://issues.scala-lang.org/browse/SI-4290?orig=1
Reporter: @paulp
See #4288

@paulp said:
I can feel my brain sprouting cracks so I'll just leave this for now. Given some high level documentation of how the pieces are supposed to fit together, and a believable strategy for keeping all the classes in sync, I imagine I can implement it. Until then there are too many question marks for me to want to dive in. I wouldn't even have stuck a toe in were it not for ListBuffer using a *Forwarder in a fundamental way.

@paulp said:
I add the 2+2=4 observation that in the absence of other bugs and inconsistencies, given that the Forwarder implements Traversable, all the methods must get where they're going one way or another. Problems like this one emerge when there are outright inconsistencies in how methods are implemented (like slice in Traversable vs. slice everywhere else.) And there is no indication why some methods are forwarded and not others. Technically all you have to forward is foreach, right? So beyond that one method, what is driving the selection?

@paulp said:
In the end, I'll say the real story is that there are 25 concrete implementations of slice in the collections. TWENTY-FIVE. Suddenly it's less than surprising that there are at least three distinct behaviors around the corners.

We are not exactly hitting it out of the park if we can't manage with fewer than 25 variations of slice.

@retronym said:
See also SynchronizedQueue from #4916

@retronym said:
Mirco outlines the serious issues with SynchronizedXxx in the (closed as duplicate) #7925:

Synchronized collections are broken in their design and, even worst, they currently don't fullfil their contract, i.e., most of the methods aren't synchronized!
Here is a comment in SynchronizedMap that should definitely make you nervous:
todo: also add all other methods.
Similar comments can be found in the other Synchronized collection traits.
Furthermore, these traits are broken in design as ticket https://issues.scala-lang.org/browse/SI-6087 demonstrates.
For the above reasons, I'd highly recommend to 1) add the missing synchronized methods, and 2) deprecate all Synchronized collection traits before shipping 2.11.
However, I realize that providing synchronized collections may still be desiderable (not everyone may be happy to migrate toward a concurrent collection - though, I'd like to know what's the argument for that). For this reason, I think we could provide Synchronized wrappers like Java does. This won't help people that were mixing a Synchronized trait with other collection traits, but I really don't see how we could allow that, and still prevent users from shooting themselves in the foot. If you have a great idea, please do share it.
This ticket is based on the following discussion https://groups.google.com/forum/#!topic/scala-internals/1gCbqTRCxAQ

@retronym said:
Forwarders and Proxies have been deprecated: scala/scala#3103

That change doesn't offer a plan for ListBuffer, though.

@Ichoran said:
Closing as wontfix since we've deprecated instead. Opening a new ticket to migrate ListBuffer.

@Ichoran said:
Maintenance burden is too great to maintain all of these manually. Deprecated instead of fixing.