Yuck. This is the kind of terse, impenetrable code that everybody would point to as evidence of being a terrible programming language if this were C.
I was all prepared to excoriate people for not using a separate assert(vecs.len >= i), but then a little alarm went off in my brain.
Sadly, I suspect this is necessitated by the fact that assert() is not guaranteed to get removed under different release levels and has semantics that you might not expect by virtue of being a function…
See discussion here: Key semantics of std.debug.assert
That’s doesn’t mean I still don’t consider it yucky …
I think this is pointing back to the need for an @assert() built-in for hot-paths that is guaranteed to disappear in -DReleaseFast or -DReleaseSmall …