Keep an import whose sibling if/else branch assigns a fallback to the same name

[hakancelikdev]

Regression from #350 (stores no longer count as uses), found in the second review of claude/integration.

Problem

import sys
if sys.version_info >= (3, 11):
    import tomllib
else:
    tomllib = None

main kept import tomllib only because tomllib = None counted as a use. After #350 it no longer does, so the import became pass, and from compat import tomllib raised ImportError on 3.11+. The dispatch rule only protected names imported in both branches.

Fix

visit_If now also treats as a dispatch a name imported in one branch and assigned (Assign / AnnAssign with a value) directly in the sibling branch. Assignments are followed through elif chains. This works in both directions, e.g. Missing = None / else: from typing_extensions import Missing.

Tests

The new if_dispatch/fallback_assignment case covers if/else, if/elif/else, and the reversed order. It also includes a negative case where the else branch assigns a different name, and that import is still removed. The case fails before this change. Full suite passes on 3.9 / 3.12 / 3.14, and pre-commit passes.

🤖 Generated with Claude Code

https://claude.ai/code/session_019P9bvuGwAyVCNUdsAYPB1V

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