SE-0266 — Synthesized Comparable conformance for enum types

[xwu (Xiaodi Wu)]

@David_Sweeris

So whether or not people "care", it's a property that people can rely on if they wish. Given that Comparable and CaseIterable both effectively would define total orders among the cases, I think it would be actively harmful for those orders to be different.

Oh, my mistake, I hadn't realized that the order for that was documented behavior. Also, I agree that it would be bad if they were ordered differently.

Late to the party, but this brings up a potential footgun not discussed yet:

If the user has elected to provide a custom implementation of CaseIterable conformance, potentially reordering the cases, then it can be unexpected if Comparable is synthesized using source order, introducing two (or if RawRepresentable, potentially three) definitions of total order among cases without warning.

It may be reasonable to consider not synthesizing Comparable for enums with custom CaseIterable implementations.