RFR: 8262889: Compiler implementation for Record Patterns [v4]

[Vicente Romero]

On Mon, 9 May 2022 14:37:35 GMT, Jan Lahoda <jlahoda at openjdk.org> wrote:

>> 8262889: Compiler implementation for Record Patterns
>> 
>> A first version of a patch that introduces record patterns into javac as a preview feature. For the specification, please see:
>> http://cr.openjdk.java.net/~gbierman/jep427+405/jep427+405-20220426/specs/patterns-switch-record-patterns-jls.html
>> 
>> There are two notable tricky parts:
>> -in the parser, it was necessary to improve the `analyzePattern` method to handle nested/record patterns, while still keeping error recovery reasonable
>> -in the `TransPatterns`, the desugaring of the record patterns is very straightforward - effectivelly the record patterns are desugared into guards/conditions. This will likely be improved in some future version/preview
>> 
>> `MatchException` has been extended to cover additional cases related to record patterns.
>
> 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 'type-pattern-third' into patterns-record-deconstruction3
>  - Using Type.isRaw instead of checking the AST structure.
>  - Exhaustiveness should accept supertypes of the specified type.
>  - Renaming the features from deconstruction pattern to record pattern.
>  - Fixing guards after record patterns.
>  - Raw types are not allowed in record patterns.
>  - Reflecting review feedback.
>  - 8262889: Compiler implementation for Record Patterns

I've noticed that this code:

class Test {
    String e(E e) {
        return switch (e) {
            case A -> "42";
        };
    }

    enum E {
        A, B;
    }
}

fails with:

Test.java:3: error: the switch expression does not cover all possible input values
        return switch (e) {
               ^
1 error

before this change but gets accepted with no error message after it

-------------

PR: https://git.openjdk.java.net/jdk/pull/8516