Allow designated initialization of struct

[Nick Treleaven]

On Saturday, 2 November 2024 at 18:01:45 UTC, IchorDev wrote:
> Nope, not even close. That medal has to go to integer promotion.

That seems off-topic for this DIP thread.

> ```d
> short x = 127;
> short y = x / 2 + 1; //Error: integer promotion screwed you 
> over again!

Actually that example compiles fine due to VRP.
https://dlang.org/spec/type.html#vrp