On Jun 9, 2017, at 1:45 PM, John Rose <john.r.rose at oracle.com> wrote: > > Allowing <T> in return position to assume <void> will be attractive with new generics. Allowing Map<any K,any V> to assume V=void with no layout footprint derives Set<K>. This is a trick Rust plays successfully. I've always wanted to pull that trick.