<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/208266>208266</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang-format] AlignTrailingComments with OverEmptyLines misaligns previously stable file after #206393
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang-format
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          earnol
      </td>
    </tr>
</table>

<pre>
    After bae9ddca423145baf0c35e31898b723aa273f85c (#206393), a previously stable file gets reformatted, because a trailing comment in an enum is shifted to align with trailing comments in a subsequent message block, even though they are separated by a non-trailing block comment.

**Configuration (.clang-format):**
```
---
Language: Proto
BasedOnStyle: Google
AlignConsecutiveAssignments: true
AlignConsecutiveDeclarations: true
AlignTrailingComments:
  Kind: Always
  OverEmptyLines: 4
ColumnLimit: 0
```
**Input (stable before bae9ddca4231, unstable after)**:
```
enum E {
  OK = 0; /* Operation completed successfully. */
}
/* comment */
message M {
  optional uint32 field_a                     = 1; /* Short description of field_a */
  repeated uint32 field_b_long_name_for_align = 2; /* Multi-line
                                                      description */
}
```
**Expected behavior**:
No change — the file is already correctly formatted.

**Actual**:
The trailing comment in the enum is shifted to align with the trailing comments in the message below, despite a non-trailing /* comment */ block separating them.

 **Analysis**:
The new condition added in WhitespaceManager::calculateLineBreakInformation():
```
  (P.NewlinesBefore == 0 || !PP || PP->IsTrailingComment)
```
 changes how IsTrailingComment propagates. The non-trailing block comment (/* comment */ on its own line) is now incorrectly treated in a way that allows the AlignTrailingComments logic with OverEmptyLines: 4  to "see through" it and align comments across unrelated blocks.

Before the patch, the block comment acted as a barrier preventing cross-block trailing comment alignment. After the patch, it no longer does.

**Verified**:
Reverting bae9ddca4231 on current HEAD restores idempotency.

Simplification done with: kiro-cli.


</pre>
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