Thanks! I'm afraid I don't know of any way to make the existential types hack neater. If you find one, I'm all ears! There is an issue open with the F# compil

Thanks! I'm afraid I don't know of any way to make the existential types hack neater. If you find one, I'm all ears! There is an issue open with the F# compiler (https://github.com/fsharp/fslang-suggestions/issues/567 https://github.com/fsharp/fslang-suggestions/issues/567) to allow higher-ranked types, but there are (well-founded) objections that this could be a pretty big jump in language complexity.