inout(shared) as a thing?

[Nicholas Wilson]

I was reading 
https://github.com/rikkimax/stdc-signatures/blob/master/stdc/graphic/image.d#L54 as part of https://github.com/rikkimax/DIPs/blob/master/DIPs/DIP1xxx-RC.md and it struck me that the duplication of `IFoo` and `ISharedFoo` might be made redundant `with inout(shared)` as `inout` (->`inout(const)`? so that one can write `inout(shared,const)`. obviously no need to deprecate plain inout) is to mutable/const/immutable.

I think this would work for "declarations" like 
interfaces/signatures/contraints, I'm not so sure about 
implementations as the acquisition of ownership needs to occur to 
take place in order to avoid data races.

Maybe inout(shared=(T t){...}) where (T t){...} is a lamda (or 
some other builtin) that ensures that t (or this) is owned by by 
the executing thread. could also have inout(shared=synchronized), 
inout(shared=synchronized(a)) where a is a variable in scope 
(e.g. parameter, member,...), inout(shared=atomic) or some 
wrapper that atomically loads t or this. Just throwing out ideas.

I don't think this would work on the return value of functions.

Thoughts? Worthy of a DIP?

Nic