Prototype of Ownership/Borrowing System for D

[Walter Bright]

On 11/19/2019 11:49 PM, Manu wrote:
> I haven't read thoroughly yet, although I have been following along
> the way and understand the goals... but I really can't not say
> straight up that I think `@live` is very upsetting to me.
> I hate to bike-shed, but at face value `@live` is a very unintuitive
> name. It offers me no intuition what to expect, and I have at no point
> along this process has any idea what it means or why you chose that
> word, and I think that's an immediate ref flag.

The "live" refers to the data flow analysis which discovers which pointers are 
"live" or "dead" at any point in the flow graph. This is critical for what O/B 
is trying to do.

`@ownerBorrow` just seems a little awkward :-)

Andrei proposed `@live`, and I like it. It's short, sweet, and sounds good.

> Are you really certain there's no way to do this without adding yet
> more attributes?

We'll never be able to compile C-like code if we force an O/B system on all the 
code. There has to be a way to distinguish, like what `pure` does. D would be 
unusable if everything had to be `pure`. My understanding of O/B is you're going 
to have to redesign code and data structures to use it effectively. I.e. it'll 
break everything. Rust has a powerful enough marketing machine to convince 
people that redesigning your programs is a Good Thing (tm) and perhaps it is, 
but we don't have the muscle to do that.

> It would be better if an attribute was not required
> for this... we're already way overloaded in that department.
> Timon appeared to have a competing proposal which didn't add an
> attribute. I never saw your critique of his work, how do your relative
> approaches compare?

I don't have a good understanding of Timon's work yet.