fix: add types.UnionType support to comparator

[aseembits93]

Summary

• The comparator did not handle types.UnionType (the type produced by Python 3.10+ X | Y union syntax), causing it to log "Unknown comparator input type" and return False for valid equal unions.
• Conditionally adds types.UnionType to the equality-checked types tuple (guarded by getattr for Python 3.9 compatibility).
• Adds 7 tests covering equality, inequality, order independence, multi-arg unions, nested containers, and None comparison.

Test plan

• All 7 new TestUnionType tests pass
• Full comparator test suite passes (139 passed, 43 skipped)
• Ruff linting passes on comparator.py
• Python 3.9 compatible (conditional inclusion via getattr)

🤖 Generated with Claude Code

[claude]

PR Review Summary

Prek Checks

✅ All checks passed (ruff check, ruff format) — no issues found.

Mypy

✅ No new mypy errors introduced by this PR. All reported errors are pre-existing on main.

Code Review

✅ No critical bugs, security vulnerabilities, or breaking API changes found.

Notes:

• The _equality_types tuple is rebuilt on every comparator() call due to the runtime getattr + walrus operator pattern. This is functionally correct and the overhead is negligible, but it could be moved to module level for a minor efficiency gain.
• The getattr(types, "UnionType", None) guard correctly handles Python 3.9 compatibility.
• Tests are well-structured with appropriate skipif for Python < 3.10.

Test Coverage

File	Stmts (PR)	Miss (PR)	Cover (PR)	Cover (main)	Delta
codeflash/verification/comparator.py	379	163	57%	56%	+1%
tests/test_comparator.py	3315	1354	59%	59%	0%

• ✅ All new lines in comparator.py (lines 148-169) are covered by tests
• ✅ All 7 new TestUnionType tests pass (139 passed, 43 skipped total)
• ✅ No coverage regressions — slight improvement (+1%) on comparator.py

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Last updated: 2026-02-20