On Thu, 5 May 2022 11:57:34 GMT, Aggelos Biboudis <abimpou...@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. > > src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java line 783: > >> 781: } >> 782: for (Entry<Symbol, List<JCDeconstructionPattern>> e : >> categorizedDeconstructionPatterns.entrySet()) { >> 783: if (coversDeconstructionStartingFromComponent(pos, >> targetType, e.getValue(), 0)) { > > Here, the result of `e.getValue` is a reversed list of the observed patterns. > > For the switch below, > > > switch (r) { > case R(A a, A b) -> 1; > case R(A a, B b) -> 2; > case R(B a, A b) -> 3; > case R(B a, B b) -> 4; > } > > > The 0th element of that list is the `R(B a, B b)` pattern, the 1st the `R(B > a, A b)`. I am 99% sure that this is not a problem but I am pointing it out > regardless, in case there is any underlying danger to that. Order doesn't matter. I triple checked. ------------- PR: https://git.openjdk.java.net/jdk/pull/8516
