On Wed, 4 May 2022 09:59:33 GMT, Maurizio Cimadamore <mcimadam...@openjdk.org> wrote:
>> 8262889: Compiler implementation for Record Patterns >> >> A first version of a patch that introduces record patterns into javac as a >> preview feature. For the specification, please see: >> http://cr.openjdk.java.net/~gbierman/jep427+405/jep427+405-20220426/specs/patterns-switch-record-patterns-jls.html >> >> There are two notable tricky parts: >> -in the parser, it was necessary to improve the `analyzePattern` method to >> handle nested/record patterns, while still keeping error recovery reasonable >> -in the `TransPatterns`, the desugaring of the record patterns is very >> straightforward - effectivelly the record patterns are desugared into >> guards/conditions. This will likely be improved in some future >> version/preview >> >> `MatchException` has been extended to cover additional cases related to >> record patterns. > > src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Attr.java line 4180: > >> 4178: type = attribTree(tree.var.vartype, env, varInfo); >> 4179: } else { >> 4180: type = resultInfo.pt; > > Looks good - infers the binging var type from the record component being > processed. If not in a record, then I suspect resultInfo.pt is just the > target expression type (e.g. var in toplevel environment). That said, I'm not sure how this connects with `instanceof`. This patch doesn't seem to alter `visitTypeTest`. In the current code I can see this: if (tree.pattern.getTag() == BINDINGPATTERN || tree.pattern.getTag() == PARENTHESIZEDPATTERN) { attribTree(tree.pattern, env, unknownExprInfo); ... This seems wrong for two reasons: * it doesn't take into account the new pattern tag * it uses an "unknown" result info when attributing, meaning that any toplevel `var` pattern will not be attributed correctly But we seem to have tests covering record patterns and instanceof. so I'm wondering if I'm missing some code update? ------------- PR: https://git.openjdk.java.net/jdk/pull/8516