RFR: JDK-8315248: AssertionError in Name.compareTo

Wed Aug 30 00:32:27 UTC 2023

Please review a small fix to avoid an `AssertionError` coming out of `CharSequence.compare` for two `CharSequence` objects obtained from different instances of the `javax.lang.model` API.

Full details in the JBS issue and comments.

There are some minor cleanup edits as well, and some improvements to the code to throw AssertionError in a few places.

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Commit messages:
 - JDK-8315248: AssertionError in Name.compareTo

Changes: https://git.openjdk.org/jdk/pull/15478/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15478&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315248
  Stats: 153 lines in 2 files changed: 140 ins; 8 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/15478.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15478/head:pull/15478

PR: https://git.openjdk.org/jdk/pull/15478