MICROSOFT · MICROSOFT / TYPESCRIPT
AvailableNarrowing regression on discriminated tuple unions
TypeScript · Intermediate · 4 days remain · Issue #59871
The brief
A recent control-flow refactor broke narrowing for discriminated unions nested in tuple types. Restore the 5.8 behaviour with a regression test.
Acceptance criteria
- Repro from the issue narrows without assertion errors
- Full baselines pass with zero unexpected diffs
- Regression test added under checker suites
Live status timeline
- 2026-09-06
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Published funded by @ts-maintainer
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0.18 $MSFT
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