Propagating Errors

[FeepingCreature]

On Friday, 8 March 2019 at 06:09:30 UTC, Nicholas Wilson wrote:
> This works nicely for __traits compiles, I'm not so sure about 
> is expressions (though I'd love to be shown otherwise).

I'm not sure what the problem with `is` is? `is` is also designed 
to return false on compile failure and true on success, so 
replacing its return value with an ErrorObject doesn't seem like 
it *should* break things.