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Cache undefined widening properties per symbol, not per name - #64728
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Max Schwenk (maschwenk) wants to merge 1 commit into
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Max Schwenk (maschwenk) wants to merge 1 commit into
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getUndefinedProperty cached its synthetic `prop?: undefined` symbol by property name. The first object literal to widen a given name won, and its declaration position decided where the property printed in later, unrelated types. So declaration output changed depending on which other files shared a checker, and therefore on --checkers. Key the cache by the source property symbol instead.
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Unless copilot points out something I missed, this fix seems fine |
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🟢 Approval recommended
The focused cache-key correction is consistent with symbol identity and has appropriate regression and baseline coverage.
0 open findings
What changed in this PR
Fixes nondeterministic declaration property ordering by scoping synthetic undefined-property symbols to their source symbols.
Changes:
- Cache undefined properties per source symbol instead of property name.
- Add regression coverage for cross-literal cache contamination.
- Update affected declaration, type, and symbol baselines.
| File | Description |
|---|---|
tsc/internal/checker/checker.go |
Keys undefined-property cache by source symbol. |
tsc/testdata/tests/cases/compiler/undefinedPropertyDeclarationOrder.ts |
Adds the regression case. |
tsc/testdata/baselines/reference/compiler/undefinedPropertyDeclarationOrder.js |
Records declaration output. |
tsc/testdata/baselines/reference/compiler/undefinedPropertyDeclarationOrder.types |
Records inferred types. |
tsc/testdata/baselines/reference/compiler/undefinedPropertyDeclarationOrder.symbols |
Records symbol identities. |
tsc/testdata/baselines/reference/conformance/objectLiteralNormalization.js |
Updates normalized declaration ordering. |
tsc/testdata/baselines/reference/conformance/objectLiteralNormalization.types |
Updates normalized type ordering. |
tsc/testdata/baselines/reference/conformance/objectLiteralNormalization.symbols |
Removes unrelated cached declarations. |
🧠 Review effort: Balanced
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Jake Bailey (jakebailey)
approved these changes
Oct 12, 2026
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Fixes #64727
getUndefinedProperty cached the synthetic
prop?: undefinedsymbol by name, so the first object literal to widen a name decided how that property printed in later, unrelated types. declaration output then depended on which other files shared a checker, and on --checkers.this keys the cache by the source property symbol instead. it's a 4 line change in checker.go.
ai disclosure: written with claude code. i've read the change and will handle review myself.