RFC: scope and borrowing

[Steven Schveighoffer via Digitalmars-d]

On 9/23/14 7:11 AM, bearophile wrote:
> Steven Schveighoffer:
>
>>> int[] foo(unique int[] a) pure {
>> ...
>> I don't think so. Strong pure function optimizations would not work
>> for something like:
>>
>> auto x = foo(a) ~ foo(a);
>
> This is similar to:
>
> unique x1 = foo(a);
> unique x2 = foo(a);
> unique x = x1 ~ x2;
>
> When the call to the first foo ends you have a x1 reference to the array
> data. Such reference x1 is unique, so now 'a' is not usable any more,
> you can't pass 'a' to foo once more.
> I need to learn more about such stuff of linear typing.

This begs the question, what is the point of having "strong purity" if 
you can't optimize based on it?

-Steve