RFR: 8310314: Misplaced "unnamed classes are a preview feature and are disabled by default" error

[Jan Lahoda]

Consider code like:

$ cat Test.java
void main() {
    System.err.println("Hello!");
}


Currently, the "unnamed classes are a preview feature and are disabled by default" error is put at the end of the file:

$ java Test.java
Test.java:4: error: unnamed classes are a preview feature and are disabled by default.

  (use --enable-preview to enable unnamed classes)
1 error
error: compilation failed


This does not seem to be user friendly. It seems to me that putting the error on the first method/variable in the file would be better:

$ java Test.java
Test.java:1: error: unnamed classes are a preview feature and are disabled by default.
void main() {
^
  (use --enable-preview to enable unnamed classes)
1 error
error: compilation failed


The proposed patch is to simply move the source level check to the place where the top-level method or field is parsed. Calling the method multiple times for a single file should not be a problem - `Log` itself will prevent printing the error multiple times for the same file.

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

Commit messages:
 - Improving test metadata
 - Enhancing test.
 - 8310314: Misplaces "unnamed classes are a preview feature and are disabled by default" error

Changes: https://git.openjdk.org/jdk/pull/14544/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14544&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310314
  Stats: 18 lines in 3 files changed: 16 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/14544.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14544/head:pull/14544

PR: https://git.openjdk.org/jdk/pull/14544