RFR: 8291769: Translation of switch with record patterns could be improved [v6]

[Jan Lahoda]

On Tue, 27 Sep 2022 23:40:12 GMT, Vicente Romero <vromero at openjdk.org> wrote:

>> Jan Lahoda has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains eight commits:
>> 
>>  - Merge branch 'master' into JDK-8291769
>>  - Merge branch 'master' into JDK-8291769
>>  - Reflecting review feedback.
>>  - Merge branch 'master' into JDK-8291769
>>  - Using a custom record instead of a generic Pair.
>>  - Fixing test.
>>  - Properly handle null record components.
>>  - 8291769: Translation of switch with record patterns could be improved
>
> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TransPatterns.java line 369:
> 
>> 367:             nestedPatterns = nestedPatterns.tail;
>> 368:         }
>> 369:         Assert.check(components.isEmpty() == nestedPatterns.isEmpty());
> 
> is it possible for this assertion not to hold under some conditions? can it be removed?

This is mostly to ensure that if there would be a bug in `Attr` that would not produce an error in case the number of record components, and the number of nested patterns would not match, javac will fail consistently.

> src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TransPatterns.java line 403:
> 
>> 401:                     ? syms.objectType
>> 402:                     : selector.type;
>> 403:             Assert.check(preview.isEnabled());
> 
> side: not part of your patch but, do we need to check if preview is enabled at this point?

The ordinary checks should have happened in the parser and/or `Attr`, this is mostly s safeguard in case some of the checks would be missing for any reason.

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PR: https://git.openjdk.org/jdk/pull/9746