[afrisch]

Well, OCaml is indeed rather popular for implementing compilers for new languages (sometimes later bootstrapped), including ones which became rather popular. I can think of F#, Rust, Elm, Haxe, FlowType for instance.

[pera]

Was Elm originally implemented in OCaml? I thought it was Haskell.

Another two relatively popular languages implemented in Haskell are Idris and Agda.

[specializeded]

They might have meant ReasonML, both it and Elm interop w/ JS

https://github.com/facebook/reason

[afrisch]

I could have added reasonml to the list indeed, but reasonml really is (a different syntax for) ocaml.

[Shoop]

Elm is still implemented in Haskell. Self-hosting isn't a goal.

[afrisch]

Yes sorry, Elm is indeed implemented in Haskell.

[ecnahc515]

There's also a project for implementing a prolog like interpreter for doing type checking and other logic for Rust, I think it works on the MIR level, but could be wrong on that.