RFR: 8309093: Underscore with brackets

Tue May 30 14:45:21 UTC 2023

Currently `<type> _[]` passes compilation while it is prohibited by the [spec](https://cr.openjdk.org/~abimpoudis/unnamed/jep443-20230322/specs/unnamed-jls.html#jls-14.14.2). This PR addresses that.

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Commit messages:
 - 8309093: Underscore with brackets

Changes: https://git.openjdk.org/jdk/pull/14217/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14217&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309093
  Stats: 50 lines in 6 files changed: 47 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14217.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14217/head:pull/14217

PR: https://git.openjdk.org/jdk/pull/14217