[jdk13u-dev] RFR: 8286444: javac errors after JDK-8251329 are not helpful enough to find root cause

[Yuri Nesterenko]

Useful improvement made by Christoph Langer following JDK-8251329. Regtests run fine; expecting to add JDK-8286855 as a follow-up. Clean backport with only copyright date difference.

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

Commit messages:
 - Backport 29c4b8e80d1860249a79cfd1941354150468fc5b

Changes: https://git.openjdk.org/jdk13u-dev/pull/365/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk13u-dev&pr=365&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286444
  Stats: 7 lines in 1 file changed: 5 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk13u-dev/pull/365.diff
  Fetch: git fetch https://git.openjdk.org/jdk13u-dev pull/365/head:pull/365

PR: https://git.openjdk.org/jdk13u-dev/pull/365