Hi! Thank you for your interest (and for potentially reading this).

Yes, F# is a very nice language, however, it seems to me that I am making a somewhat forced comparison between OCaml and F# in the following section: https://xvw.lol/en/articles/why-ocaml.html#ocaml-and-f

You can hack up GADTs in F# - for example, https://github.com/Smaug123/WoofWare.Incremental/blob/9b8181... (which uses https://github.com/G-Research/TypeEquality ). (The other missing features I agree are missing.)

Yes, the trick is expanded here: https://libres.uncg.edu/ir/asu/f/Johann_Patricia_2008_Founda... (if you have `Eq a b = Refl : a a eq` you should be able to encode every useful GADTs. But having a compiler support is nice for specifics reason like being able to "try" to detect unreachable cases in match branches for examples.

I've used equality witnesses in F# before, they kinda work but can't match proper GADTs. First you'll need identity conversion methods on the witness, because patterns can't introduce type equalities, then you'll realise you can't refute unreachable branches for the same reason, so you still need to use exceptions.

Thanks, that was an interesting read for sure!

It's always weird when Microsoft pulls an "embrace, extend, extinguish" but the "extinguish" part happens without their involvement or desire and then we're all stuck wondering how Microsoft got left holding the bag.