[jdk17] RFR: 8269146: Missing unreported constraints on pattern and other case label combination [v2]

[Jan Lahoda]

> There is a number of constraints on the case label forms - patterns cannot be combined with patterns, etc. Currently, the checks are implemented by checking if there are clashing bindings. But this misses some of the cases which should lead to errors. This patch proposes to implement explicit checks on the structure of the case labels in `Attr.handleSwitch`, rather than relying on clashing bindings.

Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:

  Fixing fallthrough.

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Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/194/files
  - new: https://git.openjdk.java.net/jdk17/pull/194/files/780a4189..3034355c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=194&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=194&range=00-01

  Stats: 31 lines in 2 files changed: 29 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/194.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/194/head:pull/194

PR: https://git.openjdk.java.net/jdk17/pull/194