CRITICAL: PR #21746 contains unresolved merge conflict markers - cannot merge

[knoal]

Problem - CRITICAL

PR #21746 (Fix list concatenation ignoring outer list type context) contains unresolved merge conflict markers in the actual diff:

<<<<<<< ours
=======
>>>>>>> theirs

The PR CANNOT be merged cleanly as-is. The author pushed a PR without properly resolving merge conflicts.

Impact

• The PR is in a broken non-mergeable state
• The patch as submitted will not parse cleanly
• GitHub's merge button will likely reject the PR
• A real bug fix is being blocked by a botched rebase/merge

What was audited

MCE audit Tmypy21746 (2026-07-19) caught 5 HIGH attacks via F-C:

1. The diff contains unresolved merge conflict markers
2. The new test case x = a + [10] does NOT actually exercise the bug being fixed
3. P3 (Nested lists handled) has no test coverage at all
4. P1 and P2 are stated as if they are results of the PR, but they depend on the merge-conflict-mangled check_op_expr
5. The "failing-first" methodology is violated wholesale

Recommended fix

1. The author should rebase the branch against current main
2. Resolve all merge conflict markers
3. Verify the test actually exercises the bug being fixed
4. Verify the failing-first methodology

Cross-references

• MCE audit: Tmypy21746 (2026-07-19), 0/4 HIT, Brier 0.6
• F-C analysis: /home/alex/.hermes/mce/fc-critiques/Tmypy21746-with-diff.json
• PR: Fix list concatenation ignoring outer list type context #21746

[JelleZijlstra]

Just comment on the PR