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We just landed a new (experimental) feature for v12 - nested record definitions! Records is a corner stone in ReScript. However, they can't be nested without explicit definitions. Until now! Will be especially useful for deeply nested records (like options objects) not intended to be reused.

20/3/25, 5:37 pm5 reposts24 likes

Jeroen Engels

@jfmengels.bsky.social

21 Mar 2025

That sounds great. I'm curious, why was there this limitation before?

Florian

@fham.dev

22 Mar 2025

It was inherited from OCaml, but in v12 we removed OCaml syntax support and finally even have our own AST now. Or so I think at least, but @z-th.bsky.social implemented it, so he may know more.

Gabriel Nordeborn

@z-th.bsky.social

22 Mar 2025

Yes, it's inherited from OCaml. But I'm sure there's good reason for it looking that way (one type definition per level). What we've been bothered by is the ergonomics primarily. This first implementation still uses individual records for each level, just hides it to the user in practice. 1/2

Gabriel Nordeborn

@z-th.bsky.social

22 Mar 2025

But since we're gradually moving away from the OCaml AST to our own AST it's possible for us to first-class this in the AST if we want to, and if the experiment proves fruitful. Side note - nested definitions has always been possible with structural objects, but not with records. 2/2

Dan

@danbowles.com

20 Mar 2025

Well that's mighty awesome 😎