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

The query expression is kind of similar to safe navigation 
operators [1], but returns true/false instead of the value. I 
like it, but I wonder if it is something that might be useful 
more generally.

[1] https://en.wikipedia.org/wiki/Safe_navigation_operator