Allocator-aware @safe reference counting is still not possible

[Nick Treleaven]

On Sunday, 22 January 2023 at 21:11:31 UTC, RTM wrote:
> On Sunday, 22 January 2023 at 15:28:53 UTC, Atila Neves wrote:
>> I'm pretty much convinced we need isolated.
> Seems redundant to dip1021 (@live).

 From the @live docs:

> Multiple borrower pointers can simultaneously exist if all of 
> them are pointers to read only (const or immutable) data

AFAIU isolated needs to guarantee no other references point to 
the data, so that we can call `free` on it without dangling 
references. That applies even if the data is immutable, so we can 
put immutable data on the heap.