> 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
Jan Lahoda has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 12 commits: - Post-merge fix - need to include jdk.internal.javac in the list of packages used by jdk.compiler again, as we now (again) have a preview feature in javac. - Correcting LineNumberTable for rule switches. - Merging master into JDK-8262891 - Fixing various error-related bugs. - Avoiding fall-through from the total case to a synthetic default but changing total patterns to default. - Reflecting recent spec changes. - Reflecting review comments. - Reflecting review comments on SwitchBootstraps. - Trailing whitespaces. - Cleanup, reflecting review comments. - ... and 2 more: https://git.openjdk.java.net/jdk/compare/083416d3...fd748501 ------------- Changes: https://git.openjdk.java.net/jdk/pull/3863/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3863&range=04 Stats: 4551 lines in 77 files changed: 4235 ins; 119 del; 197 mod Patch: https://git.openjdk.java.net/jdk/pull/3863.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/3863/head:pull/3863 PR: https://git.openjdk.java.net/jdk/pull/3863
