Fix sorting when using a TreePathViewerSorter in AbstractTreeViewer

[FlorianKroiss]

Fixes #3900

I tried to minimize code duplication by making the outer if clause include both cases and then checking for the actual type again

[FlorianKroiss]

@akurtakov I tested this change locally with the affected LSP4E version and the test passed again when using CommonViewerSorter.

[merks]

The baseline errors look kind of bogus and seem to be related to signed versus unsigned.

[github-actions]

Test Results

   852 files  ±0     852 suites  ±0   53m 38s ⏱️ - 5m 26s
 7 913 tests +2   7 670 ✅ +2  243 💤 ±0  0 ❌ ±0 
20 241 runs  +6  19 586 ✅ +6  655 💤 ±0  0 ❌ ±0 

Results for commit 9ea0a5e. ± Comparison against base commit b7b54fc.

♻️ This comment has been updated with latest results.

[akurtakov]

Looks good to me but I'll not merge it now to give sometime for the verification issue to be investigated.

[merks]

Is this PR based on master? @laeubi suggested this signing problem looks like one caused by being out of sync with master. Or maybe @HannesWell made build changes. Something is obviously fishy here...

[HannesWell]

Or maybe @HannesWell made build changes. Something is obviously fishy here...

Not explicitly, but that it only affects tests is noticeable.

Error:  Failed to execute goal org.eclipse.tycho.extras:tycho-p2-extras-plugin:5.0.3-SNAPSHOT:compare-version-with-baselines (compare-attached-artifacts-with-release) on project org.eclipse.e4.core.commands.tests: Baseline and reactor have the same fully qualified version, but different content
Error:  different
Error:     META-INF/ECLIPSE_.RSA: present in baseline only
Error:     META-INF/ECLIPSE_.SF: present in baseline only

Maybe it's because of the recent removal of tests from the p2 repository. But as far as I know artifacts missing in the baseline are ignored.
But because that removal was only very recently, it could be that there are still older builds in the I-build composite that still contain the tests. And thus the baseline comparison sees an older version of the tests?

[HannesWell]

made build changes. Something is obviously fishy here...

Since this happens in almost all repositories I've created a dedicated issue for that now:

• Baseline comparision failes for tests removed from Eclipse P2-repository eclipse.platform.releng.aggregator#3784

[vogella]

Nit: the switch with an unreachable default -> throw new IllegalStateException() is awkward. The sibling method internalCompare at
AbstractTreeViewer.java:654-663 already handles the same dual-type case cleanly with two instanceof checks. Mirroring that pattern here
would be more consistent and drop the dead branch:

  if (comparator instanceof TreePathViewerSorter sorter) {                                                                                  
      sorter.sort(this, path, result);                                                                                                      
  } else if (comparator instanceof TreePathViewerComparator tpvc) {                                                                         
      tpvc.sort(this, path, result);                                                                                                        
  }  

[FlorianKroiss]

Thanks @vogella for taking a look. I adjusted the code accordingly.

I also added tests to make sure both cases work as expected.

[iloveeclipse]

Thanks!