fix(intl): #5582 — emit timeZoneName part for Temporal.Instant in formatToParts

[proggeramlug]

Follow-up to #5770 addressing a CodeRabbit review comment that arrived after that PR merged.

Problem

The timeZoneName-part guard added in #5770 (append_time_zone_name_part) skipped every Temporal value:

if crate::temporal::is_temporal_value(value) { return; }

Temporal.Instant is anchored to the timeline, so — like a Date/number — formatToParts should render a zone label for it when timeZoneName is requested. Only the plain Temporal kinds (PlainDate/PlainTime/PlainDateTime/PlainYearMonth/PlainMonthDay) are zoneless and must stay suppressed. (ZonedDateTime/Duration are rejected upstream by date_arg_to_clipped_ms and never reach this path.)

Fix

Suppress only for the plain kinds via temporal_kind, letting an Instant (and the Date/number path) emit the part.

Validation

scripts/test262_subset.py --dir intl402/DateTimeFormat: pass 145, runtime-fail 78 — unchanged from #5770 (the in-scope temporal-*-formatting-timezonename cases use only plain Temporal types, so this is a correctness fix with no test-count delta).

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Improved timeZoneName handling for Temporal values so it now works for Temporal types with an associated time zone.
  • Plain Temporal types without a time zone continue to skip timeZoneName, while other supported date and time inputs still display it when enabled.
  • Updated related behavior notes to match the new formatting rules.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: af695706-e927-4b39-befa-771fcd2ee20f

📥 Commits

Reviewing files that changed from the base of the PR and between 2412d05 and 1a412c6.

📒 Files selected for processing (1)

• crates/perry-runtime/src/intl/date_collator.rs

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📝 Walkthrough

Walkthrough

In append_time_zone_name_part, the early-return guard that previously blocked timeZoneName emission for any Temporal value is replaced with a targeted check using temporal_kind. Only the five "plain" Temporal types (PlainDate, PlainTime, PlainDateTime, PlainYearMonth, PlainMonthDay) now cause an early return; all other Temporal kinds and non-Temporal values proceed normally.

Changes

timeZoneName plain-Temporal guard

Layer / File(s)	Summary
Narrow plain-Temporal early-return crates/perry-runtime/src/intl/date_collator.rs	Replaces is_temporal_value(...) guard with temporal_kind(...) check; returns early only for the five plain Temporal kinds, expanding timeZoneName emission to zone-aware Temporal types and non-Temporal values.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related issues

• test262 intl402/Temporal toLocaleString — 61 fails (dateStyle/timeStyle rendering) #5580: This PR directly addresses timeZoneName handling for Temporal values in Intl.DateTimeFormat, which aligns with the issue's focus on timeZoneName behavior for Temporal inputs.

Possibly related PRs

• PerryTS/perry#5770: Both PRs modify date_collator.rs to adjust when timeZoneName parts are emitted for Temporal inputs in formatToParts.

Poem

🐇 Hoppity-hop through the calendar maze,
Plain dates stay quiet, but zoned ones get praise!
No longer rejected for bearing a zone,
The Temporal types with time zones have grown.
I twitched my nose and the guard became wise —
Only the plain ones get early goodbyes! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is specific and accurately summarizes the main change: emitting timeZoneName for Temporal.Instant in formatToParts.
Description check	✅ Passed	The description covers the problem, fix, related issue, and validation; it is mostly complete despite not following every template subsection.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/5582-dtf-instant-tzname

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