Allocator-aware @safe reference counting is still not possible

[Paul Backus]

On Monday, 23 January 2023 at 07:06:04 UTC, Richard (Rikki) 
Andrew Cattermole wrote:
> On 23/01/2023 10:31 AM, Paul Backus wrote:
>> Can you explain more about @localsafe? I don't understand how 
>> this is different from Dukc's proposal in the linked thread.
>
> Its @safe except you can call non-safe functions. Same goes for 
> nogc and pure.

In this context, that makes it no different from @trusted.

The problem is that, in a generic allocator-aware container, if 
you write a @trusted/@localsafe call to RCAllocator.deallocate, 
there is nothing to stop someone from writing a custom allocator 
with a deallocate function like this:

struct NaughtyAllocator
{
     // ...

     @system void deallocate(void[] block)
     {
          corruptMemory();
     }
}

...and then RCAllocator.deallocate will dispatch to this 
function, and you will end up corrupting memory in @safe code.