Record Pattern Bug in Java 19

[Clayton Wohl]

This is fixed in Java 20 build 27, 2022-12-09. Awesome! Thank you!

On Wed, Jul 27, 2022 at 3:04 PM Brian Goetz <brian.goetz at oracle.com> wrote:

> Thanks for the bug report!  This is the right place for bug reports like
> this.
>
> I believe this is the same as a bug we're currently working on; the way
> we've specified exhaustiveness is almost, but not quite, right with respect
> to generics.  Stay tuned for an update.
>
> On 7/27/2022 2:26 PM, Clayton Wohl wrote:
>
> // The example given in Brian Goetz's article:
> https://www.infoq.com/articles/data-oriented-programming-java/
> sealed interface Opt<T> {
>     record Some<T>(T value) implements Opt<T> { }
>     record None<T>() implements Opt<T> { }
> }
>
> // This works: Exhaustive switch without default case, but no record
> pattern
> public static void thisWorks1(int value) {
>     Opt<String> optValue = doSomethingThatReturnsOpt(value);
>     switch (optValue) {
>         case Opt.Some<String> some -> System.out.printf("got string:
> %s%n", some.value());
>         case Opt.None<String> none -> System.out.println("got none");
>     };
> }
>
> // This works: record pattern in a switch statement with a default case.
> public static void thisWorks2(int value) {
>     Opt<String> optValue = doSomethingThatReturnsOpt(value);
>     switch (optValue) {
>         case Opt.Some<String>(String v) -> System.out.printf("got string:
> %s%n", v);
>         case Opt.None<String> none -> System.out.println("got none");
>         default -> System.out.printf("default%n");
>     };
> }
>
> // This does NOT compile: Exhaustive switch without default case + record
> pattern
> public static void thisDoesNotWork(int value) {
>     Opt<String> optValue = doSomethingThatReturnsOpt(value);
>     switch (optValue) {
>         case Opt.Some<String>(String v) -> System.out.printf("got string:
> %s%n", v);
>         case Opt.None<String> none -> System.out.println("got none");
>     };
> }
>
> This is with the latest public JDK 19 build: build 19-ea+32-2220
>
> I hope I'm posting to the correct list. If this list is for internal Java
> developers only, I'm sorry.
>
>
>
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