[ty] Reuse expression cache for TypedDict union inference#25643
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charliermarsh merged 1 commit intoJun 4, 2026
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 92.13%. The percentage of expected errors that received a diagnostic held steady at 87.18%. The number of fully passing files held steady at 92/134. |
Memory usage reportMemory usage unchanged ✅ |
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| Contextually checking nested collection literals against a recursive union of `TypedDict`s should | ||
| not repeat the same inference for every union arm at every nesting level. |
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Does the behavior of this test differ on main vs in this PR? This comment (and the PR description) makes it seem like a pure optimization. An mdtest like this won't prevent perf regressions; a benchmark would.
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Summary
When contextually checking a dictionary literal against a union of TypedDicts, we speculatively infer the literal once for each candidate. Recursive fields often give the same nested expression the same type context for every candidate, causing us to repeat the entire nested inference at every level...
This reuses our existing shared expression cache across the candidate checks. We already use the same mechanism during generic-call multi-inference.
The linked issue drops from roughly 1.5s to 0.03s locally.
Closes astral-sh/ty#3663.