On Tue, 4 May 2021 16:41:44 GMT, Jan Lahoda <jlah...@openjdk.org> wrote:
> This is a preview of a patch implementing JEP 406: Pattern Matching for > switch (Preview): > https://bugs.openjdk.java.net/browse/JDK-8213076 > > The current draft of the specification is here: > http://cr.openjdk.java.net/~gbierman/jep406/jep406-20210430/specs/patterns-switch-jls.html > > A summary of notable parts of the patch: > -to support cases expressions and patterns in cases, there is a new common > superinterface for expressions and patterns, `CaseLabelTree`, which > expressions and patterns implement, and a list of case labels is returned > from `CaseTree.getLabels()`. > -to support `case default`, there is an implementation of `CaseLabelTree` > that represents it (`DefaultCaseLabelTree`). It is used also to represent the > conventional `default` internally and in the newly added methods. > -in the parser, parenthesized patterns and expressions need to be > disambiguated when parsing case labels. > -Lower has been enhanced to handle `case null` for ordinary (boxed-primitive, > String, enum) switches. This is a bit tricky for boxed primitives, as there > is no value that is not part of the input domain so that could be used to > represent `case null`. Requires a bit shuffling with values. > -TransPatterns has been enhanced to handle the pattern matching switch. It > produces code that delegates to a new bootstrap method, that will classify > the input value to the switch and return the case number, to which the switch > then jumps. To support guards, the switches (and the bootstrap method) are > restartable. The bootstrap method as such is written very simply so far, but > could be much more optimized later. > -nullable type patterns are `case String s, null`/`case null, String s`/`case > null: case String s:`/`case String s: case null:`, handling of these required > a few tricks in `Attr`, `Flow` and `TransPatterns`. > > The specdiff for the change is here (to be updated): > http://cr.openjdk.java.net/~jlahoda/8265981/specdiff.preview.01/overview-summary.html This pull request has now been integrated. Changeset: 908aca29 Author: Jan Lahoda <jlah...@openjdk.org> URL: https://git.openjdk.java.net/jdk/commit/908aca29ca60f5f251df8c6a31b2543929be12fc Stats: 4940 lines in 79 files changed: 4621 ins; 118 del; 201 mod 8262891: Compiler implementation for Pattern Matching for switch (Preview) Co-authored-by: Brian Goetz <briango...@openjdk.org> Co-authored-by: Mandy Chung <mch...@openjdk.org> Co-authored-by: Jan Lahoda <jlah...@openjdk.org> Reviewed-by: mcimadamore, forax, godin, psandoz, mchung ------------- PR: https://git.openjdk.java.net/jdk/pull/3863
