On 6/21/2019 5:07 AM, Manu wrote:
> There is no "between threads" unless you have already entered @trusted land.
> The reason for my proposal in the OP is precisely to prevent passing
> data to other threads, that's the key that makes this promotion safe.
Scope doesn't do that. I keep saying this. But the premise is strange, anyway,
as why would you want to convert a reference to shared if not to bass it to
another thread?
Because it's safe to do from the calling scope's perspective, and that's the needed entry vector into a @trusted solution.
It is also useful too in some cases to reduce needlessly overloading methods which have a threadsafe implementation.
> Can you show how you managed to get a ref to another thread without
> entering @trusted?
There's no such thing as a ref to another thread. You can pass a ref to another
thread in a scope function, as long as the ref doesn't survive the scope of foo().
The compiler cannot check that, though, and so cannot bless the implicit
conversion to shared. I've said this 4 or 5 times now.
Compiler is not required to check the users work in @trusted code. It assumes the user conformed with language requirements.