RCArray is unsafe

[Walter Bright via Digitalmars-d]

On 3/2/2015 12:42 PM, Walter Bright wrote:
> On 3/2/2015 12:37 PM, Steven Schveighoffer wrote:
>> Not exactly. Note that we are taking by reference S, which is NOT reference
>> counted. So you are passing indirectly a reference to an RC object. You aren't
>> "borrowing" that reference.
>
> It's seems that to solve the problem, it has to be borrowed, in that a static
> check will be needed that what it points to cannot be modified/deleted through
> other references to the same data.


I looked at how Rust does it. I was hoping it was something clever, but it 
isn't. A copy is made of the object to which a borrowed reference is taken - in 
other words, the reference count is incremented.

For D structs, that means, if there's a postblit, a copy must be made. For D ref 
counted classes, a ref count increment must be done.

I was hoping to avoid that, but apparently there's no way.

There are cases where this can be avoided, like calling pure functions. Another 
win for pure functions!