switch exhaustiveness check not working within deconstruction pattern.

[Jan Lahoda]

Hi,

This should indeed be exhaustive, AFAIK, and javac from JDK 19 seems to be happy with the code:
---
$ ./javac --enable-preview -source 19 /tmp/Main.java
Note: /tmp/Main.java uses preview features of Java SE 19.
Note: Recompile with -Xlint:preview for details.
---

What are the precise steps to reproduce/JDK version?

Thanks,
    Jan

________________________________
From: amber-dev <amber-dev-retn at openjdk.org> on behalf of redio.development at gmail.com <redio.development at gmail.com>
Sent: Sunday, November 13, 2022 6:48 PM
To: amber-dev at openjdk.org <amber-dev at openjdk.org>
Subject: switch exhaustiveness check not working within deconstruction pattern.


package dev.redio;



import static dev.redio.Main.Activity.*;



public class Main {



    public static void main(String[] args) {

        record Pair(boolean weekend, Activity activity) {}

        var pair = new Pair(true, new Sleeping(8));

        var msg = switch (pair) {   // <- A switch expression should have a default case Java(1073743531)

            case Pair(boolean b, Sleeping s) -> "3";

            case Pair(boolean b, Skiing s) -> "4";

            case Pair(boolean b, Coding c) -> "5";

        };



        System.out.println(msg);

    }



    sealed interface Activity {

        record Sleeping(int hours) implements Activity {}

        record Skiing(String resort) implements Activity {}

        record Coding() implements Activity {}

    }



}



This deconstruction should be exhaustive since Pair is a guaranteed match boolean doesn’t have subclasses and Activity is sealed and fully covered.

Null should throw in this case. A default case would never be reached.

(Compiling and running with (dead) default case)
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