Many years ago, back when I was interested compiler design, I briefly worked on F# in an academic setting. I am not sure if anyone uses F# in production but it is a very interesting langauage. I learned a lot about Hindley-Milner type inference, monads, pattern matching and more. Surprisingly I learned about functional programming features from F#.

I recently got more serious about learning rust and have noticed a lot of similarities between the two languages. One major difference is F# is garbage collected (because of C# base). F# is also a lot more forgiving than rust imo.