Record Pattern Bug in Java 19

[Brian Goetz]

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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