[dmd-concurrency] there is no escape

[Andrei Alexandrescu]

It looks like there is agreement that there is no escaping of any 
reference to an object's fields from within a method of a synchronized 
class. Inside a method of a synchronized class, effectively all members 
are transitively scoped.

This is quite restrictive, but it's the right thing to do with the 
expressive abilities we now have. I think it's possible D3 will add some 
capabilities, but for the time being it looks this is it.

One possible improvement is, as discussed, defining "scope" as a storage 
class for function parameters. I now remember a number of additional 
difficulties related to that when Walter and I discussed things a few 
months ago. One issue was that the storage class has to be transitive, 
which makes it an odd beast. Making scope a qualifier would be the right 
thing to do, but then too many qualifiers make the language quite baroque.

As we already knew, shared/synchronized limit quite drastically the 
range of lock-based designs without casts. Fortunately, using a class 
reference member inside a synchronized object will be possible 
because... well I'll explain in the text.

I continue to believe this is the right bet to make, but I expect push 
back from experienced lock-based programmers.


Andrei