If the key type isn't trivial (there's probably a better word for that), calling
range(..) on a
BTreeSet makes the compiler cry E0283 "type annotations needed", forcing us to specify the collection's key type again, as in this playground example.
Is this a recurring issue with
RangeFull in Rust or a weak spot in the definition of
range? I don't know if or how
T could default to the key type