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Fix false negatives in walrus vs inference fallback logic - #20622
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ilevkivskyi merged 1 commit intoJan 20, 2026
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
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hauntsaninja
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Jan 20, 2026
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Looks like this is worth 2% on self check. https://github.com/mypyc/mypyc-benchmark-results/blob/master/reports/benchmarks/mypy_self_check.md Maybe we can add some special case support for contextmanager in mypyc... |
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@hauntsaninja Yes, this is kind of a known thing. I raised priority for mypyc/mypyc#905 |
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This was referenced Oct 8, 2026
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Fixes #20606
This fixes couple edge cases where walrus interferes with type inference fallback logic. This is not a complete fix, but I think it is OK for now as these are probably rare situations. Most changes in binder.py are a pure performance optimization to compensate the fact that frame_context() will be more hot now. I also leave a TODO explaining a more proper fix for the assignment case (and other possible cases), return case should be already good (it is simpler since we don't need to apply any of the narrowing).