sumtypes for D

[max haughton]

On Monday, 28 November 2022 at 21:52:20 UTC, Per Nordlöw wrote:
> On Monday, 28 November 2022 at 21:44:01 UTC, Per Nordlöw wrote:
>> Sum-types is the one feature I miss the most in D.
>
> Or rather the builtin feature I missed the most having 
> standardized with a template-free `match()` enabling fine-tuned 
> diagnostics.

Yes. You can do match as a template, fairly well even, but when 
it goes even slightly wrong it goes kaboom.

The current C++ proposal defines semantics for deferring to 
existing library code, even, so the semantics could still be 
preserved but under error messages we can be proud of.