Tagged unions [Was: What's wrong with std.variant.Variant?]

[Paul Backus]

On Monday, 15 June 2020 at 21:48:19 UTC, Dukc wrote:
>> Is there a way I can improve SumType's documentation to make 
>> its behavior in this regard clearer?
>
> It's not documentations fault. But if you want to supersede 
> Taggedalgebraic really hard, you can try convincing Mike to let 
> you write a project highlight in the D blog, to raise awareness 
> for thickskulls like me :D.

That's an interesting idea. I'll look into it after the upcoming 
1.0.0 release.

>> In Rust's `enum` types you cannot access the tag directly.
>
> Again bad research from my part. But it's something I want to 
> do. Why? `final switch` statements. I may want to `return` or 
> `break` directly from the switch, and in that case I can't use 
> pattern matching without extra thinking. Well, on D anyway. I 
> don't know about Rust.

If it's not too much trouble, can you give an example of the kind 
of thing you'd like to be able to do? I suspect it's possible 
with SumType, but it may not be obvious how, which makes it a 
good candidate for the documentation's "examples" section.