Optional comparison revisited

Evolution Discussion
15

This table presents all sane possibilities how comparing some to none can work:

some>none   some<none   none>none   none<none   comment
false       false       false       false       // as Float.nan
true        false       false       false       // "something is more than nothing"
false       true        false       false       // "something is less than nothing"
nil         nil         nil         nil         // Optional<Boolean>

Float.nan would be "compatible" with Float's nan, "something is more/less and than nothing" :arrow_down: would give some reasonable sort order, although strictly speaking it's not necessary. Optional<Boolean> (returning nil) is perhaps the most "safe" option (although it won't meet Comparable conformance that needs bare Bool).

⮕ As Ben has pointed out above, "something is more/less than nothing" is the behaviour we have with "normal" enum types:

enum MyOptional1: Comparable {
    case none
    case some(Int)
}

enum MyOptional2: Comparable {
    case some(Int)
    case none
}

MyOptional1.some(0) > .none // true
MyOptional1.some(0) < .none // false
MyOptional1.none > .none    // false
MyOptional1.none < .none    // false

MyOptional2.some(0) > .none // false
MyOptional2.some(0) < .none // true
MyOptional2.none > .none    // false
MyOptional2.none < .none    // false