Why oh why the brackets? Obfuscates currying too much.

    let make ::message ::extraGreeting=? _children => ...
    let make = (~message, ~extraGreeting=?, _children) => ...

Plain OCaml:

    let make ~message ?extraGreeting _children = ...

Fortunately bucklescript is a completely separate project. After this change I might ditch Reason and just write OCaml. There were some little improvements with Reason vs OCaml but now OCaml appears to be a clear winner!