On Mon, 17 May 2021 19:04:11 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 > > Jan Lahoda has updated the pull request incrementally with three additional > commits since the last revision: > > - Reflecting recent spec changes. > - Reflecting review comments. > - Reflecting review comments on SwitchBootstraps. It's not clear to me if it's the first change and several will follow or not. The code looks good but the metaprotocol is not the right one IMO, i would prefer the one we discuss in April https://mail.openjdk.java.net/pipermail/amber-spec-experts/2021-April/002992.html But this can be tackle in another PR ------------- Marked as reviewed by fo...@github.com (no known OpenJDK username). PR: https://git.openjdk.java.net/jdk/pull/3863
