[jdk21u-dev] RFR: 8242564: javadoc crashes:: class cast exception com.sun.tools.javac.code.Symtab$6 [v2]

[Todd V. Jonker]

> This is a clean backport of https://github.com/openjdk/jdk/commit/64c3642c57719940855b220025b33758950b3980 originally authored by @vpa1977 and reviewed by @jonathan-gibbons 
> 
> Additional testing:
> - [x] New regression test fails without the fix, passes with it
> - [x] linux-x86_64-server-release: `make test TEST=test/langtools/jdk/javadoc`

Todd V. Jonker has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into jdoc-crash for testing
 - Backport 64c3642c57719940855b220025b33758950b3980

-------------

Changes:
  - all: https://git.openjdk.org/jdk21u-dev/pull/856/files
  - new: https://git.openjdk.org/jdk21u-dev/pull/856/files/fed8bbdb..f4b7f310

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=856&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=856&range=00-01

  Stats: 5796 lines in 130 files changed: 2630 ins; 1925 del; 1241 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/856.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/856/head:pull/856

PR: https://git.openjdk.org/jdk21u-dev/pull/856