RFR: 8305971: NPE in JavacProcessingEnvironment for missing enum constructor body [v2]

[Vicente Romero]

> Please review this simple fix that is averting a NPE in JavacProcessingEnvironment if a an annotation processor is used while compiling this erroneous code:
> 
> 
> enum T {
>   ONE("");
> 
>   T(String one);  // missing constructor body
> 
>   final String one;
> }
> 
> the fix is a one liner
> TIA

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  addressing review comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15974/files
  - new: https://git.openjdk.org/jdk/pull/15974/files/4647c9c7..2902b04d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15974&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15974&range=00-01

  Stats: 163 lines in 3 files changed: 111 ins; 45 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/15974.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15974/head:pull/15974

PR: https://git.openjdk.org/jdk/pull/15974