Can we just have struct inheritence already?

[Exil]

On Friday, 14 June 2019 at 00:35:10 UTC, Timon Gehr wrote:
> On 13.06.19 23:45, Walter Bright wrote:
>> On 6/13/2019 12:51 PM, Timon Gehr wrote:
>>> On 13.06.19 21:44, Walter Bright wrote:
>>>> On 6/13/2019 4:30 AM, Timon Gehr wrote:
>>>>> Yes. IMHO this shouldn't be a @safe pure operation.
>>>>
>>>> D regards converting a pointer to an int as safe, but not 
>>>> the other way around.
>>>
>>> I know, and that is fine, but casting a pointer to int is not 
>>> pure. It glances into the global state maintained by the 
>>> memory allocator.
>> 
>> We had a discussion a while back about whether allocating 
>> memory via new was pure or not, since a different value was 
>> produced each time. We eventually took the pragmatic route 
>> that pure functions would be next to useless if this was not 
>> allowed.
>
> It is obvious that allocation has to be pure. However, 
> accessing the address of your data is impure.
> The runtime systems of pure functional languages also allocate 
> memory, but the addresses are not exposed to the pure user code.

And you can't return the pointer to something in those languages. 
It is entirely dependent on the language, this is not a 
functional language. You can return pointers. What do you do when 
you expect two calls to have different allocated objects that 
have the same value? Does the compiler simply produce one object, 
or two or more?