RFR: 8332463: Byte conditional pattern case element dominates short constant case element

[David Alayachew]

I understand the first 2 cases, but not the third. How is byte -> Integer
not unconditionally exact? What possible scenario could occur where one
would lose data?

On Mon, May 20, 2024, 4:31 AM Aggelos Biboudis <abimpoudis at openjdk.org>
wrote:

> It seems that the compiler introduced a rule that does not exist in the
> spec. The fix is simple, and it will fix the behaviour of JDK 23 according
> to the spec. For example the following is accepted by JDK 22 and needs to
> continue to be accepted by JDK 23:
>
>
> public static int test() {
>     Byte i = (byte) 42;
>     return switch (i) {
>         case Byte ib   -> 1;
>         case (short) 0 -> 2; // OK - not dominated
>     };
> }
>
>
> Similarly for primitive type patterns:
>
>
> public static int test() {
>     Byte i = (byte) 42;
>     return switch (i) {
>         case Byte ib  -> 1;
>         case short s  -> 2; // Also not dominated since there is no
> unconditionally exact conversion from short to Byte
>     };
> }
>
> public static int test() {
>     int i = 42;
>     return switch (i) {
>         case Integer ib -> 1;
>         case byte ip    -> 2; // Also not dominated since there is no
> unconditionally exact conversion from byte to Integer
>     };
> }
>
> -------------
>
> Commit messages:
>  - 8332463: Byte conditional pattern case element dominates short constant
> case element
>
> Changes: https://git.openjdk.org/jdk/pull/19301/files
>   Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19301&range=00
>   Issue: https://bugs.openjdk.org/browse/JDK-8332463
>   Stats: 104 lines in 5 files changed: 94 ins; 7 del; 3 mod
>   Patch: https://git.openjdk.org/jdk/pull/19301.diff
>   Fetch: git fetch https://git.openjdk.org/jdk.git
> pull/19301/head:pull/19301
>
> PR: https://git.openjdk.org/jdk/pull/19301
>
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