Contextual metaprogramming, query the parent type.

[Nick Treleaven]

On Friday, 4 February 2022 at 15:56:05 UTC, Nick Treleaven wrote:
> I think you can do this but users would need to use a string 
> mixin when defining the field. A function can obtain the parent 
> symbol name using this trick:

Sorry, that doesn't work. But hopefully you get the idea - the 
string mixin produces something that obtains the parent type name:

```d
struct Parent
{
     pragma(msg, __traits(parent, {}).stringof); // Parent
}
```