Sum Type by Struct

[Richard (Rikki) Andrew Cattermole]

On 13/09/2024 10:25 PM, IchorDev wrote:
> On Thursday, 12 September 2024 at 11:28:56 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> The layout of the sumtype is variable size, allowing for copy 
>> constructors, destructors and no value (if size zero).
> 
> So this would enable variable-sized stack return? Do you have any plans 
> for how that might be implemented?
> Also this might be the only way to create a zero-sized type! (Hurray!)

It is not variable sized in that sense.

A specific sumtype would be fixed at compile time based upon the 
constraint set. The value you get from ``.sizeof`` is the size in assembly.

The variable size layout enables eliding aspects of it like destructors 
which are not used by a given constraint set.

> Also how costly do you think this version of sum types will be for 
> compile times?

Each of the three designs require a declaration to define a sumtype.

There is no inline declarations, so I expect that all three will be at 
the same cost.

Mostly dependent upon the set operations.

So as long as the constraint set is kept small, shouldn't be noticeable 
I would think.