draft proposal for Sum Types for D

[jmh530]

On Tuesday, 29 November 2022 at 06:26:20 UTC, Walter Bright wrote:
> Go ahead, Make My Day! Destroy!
>
> https://github.com/WalterBright/DIPs/blob/sumtypes/DIPs/1NNN-(wgb).md

One of the motivations for std.sumtype was that it was an 
alternative to std.variant that has full attribute correctness 
(@nogc/@safe/nothrow/pure) and betterC compatibility (as well as 
handling const/immutable). It would be good to mention whether 
these are also design goals of the DIP.

For that matter, std.variant (or std.typecons.Nullable) or other 
somewhat similar D approaches ([1], [2], [3]) aren't mentioned as 
part of the prior work. I don't think the DIP has to be a 
replacement for all these things, but it can't hurt to look over 
these other projects and see if there is anything in them that 
would be useful to incorporate into the DIP.

[1] 
https://github.com/libmir/mir-core/blob/master/source/mir/algebraic.d
[2] https://code.dlang.org/packages/taggedalgebraic
[3] https://code.dlang.org/packages/expected