Define an order for allMembers traits

[Paul Backus]

On Wednesday, 23 August 2023 at 16:28:27 UTC, Andrey Zherikov 
wrote:
> On Wednesday, 23 August 2023 at 15:32:02 UTC, Paul Backus wrote:
>> For this use case, you should use `.tupleof` instead of 
>> `__traits(allMembers)`, which [is guaranteed by the spec to 
>> give the fields in declaration order][1].
>>
>> [1]: https://dlang.org/spec/class.html#class_properties
>
> This link says "The order of the fields in the tuple matches 
> the order in which the fields are declared" for the classes. I 
> don't see such statement for structs 
> [here](https://dlang.org/spec/struct.html#struct_instance_properties).

The spec isn't totally clear, but I believe the intent is to say 
that it works the same way for structs unless otherwise stated. 
Certainly, in practice, the fields are always in declaration 
order.