Blog Post: Beating std::visit Without Really Trying

[Paul Backus]

On Saturday, 5 October 2019 at 13:58:52 UTC, Seb wrote:
> On Saturday, 5 October 2019 at 06:40:35 UTC, Arun 
> Chandrasekaran wrote:
>> Good one. Any plans to push SumType as a replacement of 
>> Phobo's Algebraic?
>
> Phobos is essentially dead/frozen (feature-wise). Though if 
> someone ever manages to get v2 of the ground, SumType would be 
> the obvious choice.
>
> Anyhow, currently we would have to name it differently (e.g. 
> dts - https://github.com/wilzbach/dts). Maybe the upcoming SAoC 
> project will change this and allow multiple versions of a 
> library to co-exist in a binary.

I actually would like to submit SumType to Phobos, albeit as an 
alternative to Algebraic rather than a replacement for it. Given 
how dramatic the improvement is, I think it's worth the 
awkwardness of having two sum type implementations in the 
standard library.

Currently, the main thing blocking me is bugzilla issue #19458 
[1], which (for somewhat complicated reasons [2]) makes it 
impossible for SumType to support members with @disabled and 
non-const opEquals overloads.

[1] https://issues.dlang.org/show_bug.cgi?id=19458
[2] https://github.com/pbackus/sumtype/issues/16