RFR: 8357185: Redundant local variables with unconditionally matching primitive patterns [v2]

[Aggelos Biboudis]

On Thu, 3 Jul 2025 15:31:01 GMT, Chen Liang <liach at openjdk.org> wrote:

>> A commit in the implementation of JEP 455, https://github.com/openjdk/jdk/pull/15638/commits/ceee1e4c08457a0793fdfb556db99e057a947af1, added redundant synthetic local variable for trivial `instanceof int`-ish type conversion operations in the javac AST. Such conversions have been present since the introduction of record patterns, and previously they consistently lower to the part before `instanceof`. With this change, the introduced redundant variable is visible in the class file, as seen in the JBS issue.
>> 
>> Testing: langtools/tools/javac
>
> Chen Liang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Further improvements and testing per suggestions

test/langtools/tools/javac/patterns/PrimitiveUnconditionallyExactTest.java line 86:

> 84:     @Test
> 85:     public void testExpressionExecution() {
> 86:         int a = 0;

I wonder, should we also include a test that uses assignment to a reference type? 

e.g., `Long` so that we generate both the `null` check and the ECS call. I am 95% sure that everything will be fine. Up to you @liach

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PR Review Comment: https://git.openjdk.org/jdk/pull/26107#discussion_r2183595443