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Read T[keyof T] as unknown for T bound to an unknown-valued record - #1485
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ctate merged 1 commit intoOct 20, 2026
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Inside a generic body Object.entries(t) over T extends Record<string, unknown> types its values 'keyof T extends never ? unknown : T[keyof T]'. An instance whose T maps to the checked-dynamic value now reads both branches as unknown. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Stacked on #1433 (opt/trace-reachable-blockers).
Inside a generic body,
Object.entries(t)overT extends Record<string, unknown>types its elements as[string, keyof T extends never ? unknown : T[keyof T]]. #1433 resolves that conditional, andT[keyof T], against a bound record. An instance whoseTisRecord<string, unknown>, which maps to the checked-dynamic value, still failed with SC2009. NowT[keyof T]over such aTreads as unknown. The conditional also reads as unknown, because both of its branches agree.Evidence
6468-generic-unknown-record-entries.tsis byte-identical to Node in both lanes and fails on the base branch.pnpm lintandpnpm format:checkare clean.pnpm test:ts7 --baselines-onlypasses.🤖 Generated with Claude Code