On Fri, 4 Jun 2021 09:46:31 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 one additional > commit since the last revision: > > Fixing typo. I reviewed the `java.base` change namely, SwitchBootstraps.java. Looks good. src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java line 47: > 45: * of the {@code switch}, implicitly numbered sequentially from {@code > [0..N)}. > 46: * > 47: * <p>The bootstrap call site accepts a single parameter of the type of > the It takes 2 parameters (not single parameter). Perhaps you can take out this paragraph since it's specified in the `typeSwitch` method. src/java.base/share/classes/java/lang/runtime/SwitchBootstraps.java line 110: > 108: * @return a {@code CallSite} returning the first matching element > as described above > 109: * > 110: * @throws NullPointerException if any argument is null Suggestion: * @throws NullPointerException if any argument is {@code null} same formatting nit for other occurrenace of "null" ------------- Marked as reviewed by mchung (Reviewer). PR: https://git.openjdk.java.net/jdk/pull/3863
