draft proposal for Sum Types for D

[Paul Backus]

On Tuesday, 29 November 2022 at 20:18:02 UTC, H. S. Teoh wrote:
> Supporting ctors, postblits, and dtors does increase the 
> complexity of the implementation.  Perhaps that can be left as 
> a future extension?  In any case, eventually we should support 
> it; otherwise sumtypes will be too limited in their usefulness.

Such support is already implemented in std.sumtype, so you can 
review the code yourself if you would like to see how much 
complexity it adds to the implementation.

Off the top of my head, I can tell you that most of the code 
volume comes from having to copy and paste each function 4 times 
to handle different mutability qualifiers (mutable, const, 
immutable, inout). Which is tedious (and a symptom of a missing 
language feature IMO), but not exactly complex.