Optional monitors suggestion

[Andrej Mitrovic via Digitalmars-d]

On Thursday, 22 May 2014 at 17:25:30 UTC, Steven Schveighoffer 
wrote:
> A possible path is to introduce the change, but put @monitor on 
> Object. This will allow all current code to compile as-is.
>
> Then users who are concerned about their code being affected 
> would be able to remove @monitor from Object, recompile 
> druntime and phobos (once we make it work) and allow people to 
> see how their code breaks without being left hanging (the 
> shipping compiler would still have @monitor).
>
> Then eventually, we can remove @monitor from Object, and users 
> who still wish to force @monitor on Object can do so (recompile 
> druntime and phobos with @monitor added).

This sounds like a reasonable deprecation stage.

Anyway it seems like we're all mostly on the same page here 
(remove the monitor) except the final part: potential implicit 
performance penalty vs code breakage after a deprecation stage. 
Either way we chose there's a pull ready[1] that's going stale.

Can we get an update from both Andrei & Walter to get going with 
this?

[1]: https://github.com/D-Programming-Language/dmd/pull/3547