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Disallow 'timeZone' option in Temporal.ZonedDateTime.prototype.toLocaleString - #65391
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…leString Per ECMA-402 Temporal, ZonedDateTime.prototype.toLocaleString rejects the timeZone option because the receiver's timeZoneId is always used. Introduce ZonedDateTimeToLocaleStringOptions extending Omit<Intl.DateTimeFormatOptions, "timeZone"> and update the compiler baselines. Fixes microsoft#64227
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November 8, 2026 08:52
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What changed in this PR
Updates Temporal ZonedDateTime#toLocaleString typing to disallow the timeZone option (aligning with the intended API constraints) and adds regression coverage for #64227.
Changes:
- Introduced
Temporal.ZonedDateTimeToLocaleStringOptionsasOmit<Intl.DateTimeFormatOptions, "timeZone">. - Updated
ZonedDateTime#toLocaleStringsignature to use the new options type. - Added compiler test cases + updated baselines to validate the new typing and expected errors.
| File | Description |
|---|---|
| tsc/testdata/tests/cases/compiler/temporal.ts | Adds regression calls for ZonedDateTime#toLocaleString (including timeZone) to lock in behavior. |
| tsc/internal/bundled/libs/lib.esnext.temporal.d.ts | Introduces a dedicated options type and updates toLocaleString to exclude timeZone. |
| tsc/testdata/baselines/reference/compiler/temporal.types | Baseline updates reflecting the new toLocaleString options type. |
| tsc/testdata/baselines/reference/compiler/temporal.symbols | Baseline updates for symbol binding of the new test block. |
| tsc/testdata/baselines/reference/compiler/temporal.js | Baseline updates for JS emit including the new test block. |
| tsc/testdata/baselines/reference/compiler/temporal.errors.txt | Baseline updates capturing new expected TS2353 errors for timeZone in options. |
Review effort: Lite
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| zdt.toLocaleString(undefined, { timeZone: "Europe/Berlin" }); | ||
| zdt.toLocaleString("en-US", { timeZone: "Europe/Berlin" }); |
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Under ECMA-402 Temporal,
Temporal.ZonedDateTime.prototype.toLocaleStringstrictly disallows passing atimeZoneoption because the receiver's time zone is always used (engines throw aTypeErrorif provided).This PR introduces
Temporal.ZonedDateTimeToLocaleStringOptionsextendingOmit<Intl.DateTimeFormatOptions, "timeZone">, updatesZonedDateTime.prototype.toLocaleString()to use it, and updates compiler baselines.Fixes #64227
(Note: Authored with AI assistance and verified locally against the compiler baseline suite.)