Fw: JEP 455: Non-enhanced switch statements
Maurizio Cimadamore
maurizio.cimadamore at oracle.com
Fri Oct 27 14:29:59 UTC 2023
Sure - but this logic is only applied to switch expression featuring
enums AFAIK - switch statements with enums are non-exhaustive (and I
think that will have to stay that way).
Maurizio
On 27/10/2023 15:28, Brian Goetz wrote:
>
>>
>> Unfortunately enum is that one case where compatibility dictates that
>> we can't be exhaustive, which is a little sad... but I think that's
>> the best we can do?
>>
>
> What we do for enums is do exhaustiveness checking based on the
> compile-time state of the world, and generate a synthetic default
> clause that deals with separately-compiled changes. (Same with sealed
> types.) This works pretty well, as it lets us type-check a (new)
> switch like
>
> int wavelengthNm = switch (trafficLightColor) {
> case RED -> 700;
> case YELLOW -> 580;
> case GREEN -> 540;
> }
>
> and not require a "silly" default, while offering runtime protection
> against novel colors showing up at runtime, and notifying the user at
> a subsequent compile if something unexpectedly changed.
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