interfaces and contracts - new pattern

[Adam D. Ruppe]

On Tuesday, 3 December 2019 at 17:17:15 UTC, Meta wrote:
> Which is still open, but Iain ran into stack corruption issues 
> when compiling with the -m64 flag... and no further progress. 
> So I guess it's just a matter of the bug not being fixed.

That's surprising. It could perhaps just use my pattern 
automatically and have a simpler implementation :)