On Tue, 12 Apr 2022 13:18:14 GMT, Jan Lahoda <jlah...@openjdk.org> wrote:
>> This is a (preliminary) patch for javac implementation for the third preview >> of pattern matching for switch (type patterns in switches). >> >> Draft JLS: >> http://cr.openjdk.java.net/~gbierman/PatternSwitchPlusRecordPatterns/PatternSwitchPlusRecordPatterns-20220407/specs/patterns-switch-jls.html >> >> The changes are: >> -there are no guarded patterns anymore, guards are not bound to the >> CaseElement (JLS 15.28) >> -a new contextual keyword `when` is used to add a guard, instead of `&&` >> -`null` selector value is handled on switch level (if a switch has `case >> null`, it is used, otherwise a NPE is thrown), rather than on pattern >> matching level. >> -total patterns are allowed in `instanceof` >> -`java.lang.MatchException` is added for the case where a switch is >> exhaustive (due to sealed types) at compile-time, but not at runtime. >> >> Feedback is welcome! >> >> Thanks! > > Jan Lahoda has updated the pull request incrementally with one additional > commit since the last revision: > > Cleanup. src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java line 177: > 175: allowPatternSwitch = (preview.isEnabled() || > !preview.isPreview(Feature.PATTERN_SWITCH)) && > 176: > Feature.PATTERN_SWITCH.allowedInSource(source); > 177: allowTotalPatternsInstance = (preview.isEnabled() || > !preview.isPreview(Feature.TOTAL_PATTERN_IN_INSTACEOF)) && BTW, do we need to rename total -> unconditional with the recent update in the spec? src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeInfo.java line 1349: > 1347: public static PatternPrimaryType primaryPatternType(JCTree pat) { > 1348: return switch (pat.getTag()) { > 1349: case BINDINGPATTERN -> new > PatternPrimaryType(((JCBindingPattern) pat).type); Cast may be redundant here since the signature of primaryPatternType changed to access JCTrees src/jdk.compiler/share/classes/com/sun/tools/javac/tree/TreeInfo.java line 1377: > 1375: } > 1376: JCExpression guard = ((JCPattern) cse).guard; > 1377: if (guard != null && guard.type.hasTag(BOOLEAN)) { In the spec we see the following: > A pattern case element is said to be unrefined if either (i) it has no > associated when expression, or (ii) it has an associated when expression that > is a constant expression > ([15.29](https://docs.oracle.com/javase/specs/jls/se18/html/jls-15.html#jls-15.29)) > with value true. A case element is unrefined if it is not a pattern case > element or it is an unrefined pattern case element. However, in the definition of `unconditional` I don't see the part for the constant expression. I wonder if the spec should be updated or the code at this point ------------- PR: https://git.openjdk.java.net/jdk/pull/8182
