Upd: I noticed that someone mentioned upthread that OCaml uses this to fit sum types that are either an int or a pointer into a single 64-bit value. F# doesn't

Upd: I noticed that someone mentioned upthread that OCaml uses this to fit sum types that are either an int or a pointer into a single 64-bit value. F# doesn't do that and always stores a separate tag field for sum types. This is marginally less efficient, but doesn't make interop with 99% of languages and data formats in existence awkward.