test262 intl402 tail — 1,076 fails (66.8%) after #5320: missing constructors + Temporal-Intl

[proggeramlug]

Follow-up to #5298 (closed). Honest re-measure with full Intl surface counted: intl402 = 2,163/3,239 = 66.8%, 1,076 fails.

By constructor

Temporal 243 · NumberFormat 192 · DateTimeFormat 161 · Locale 137 · DurationFormat 104 · DisplayNames 51 · RelativeTimeFormat 37 · Segmenter 35

Dominant reasons

• 138× TypeError: undefined is not a constructor — missing Intl constructor(s) (likely DurationFormat / Locale / a sub-form). Highest-ROI: implement the missing constructor(s).
• 106× Cannot read properties of undefined — partial objects (missing methods/getters on Intl instances).
• 84× Insufficient fields — Temporal↔Intl field resolution (the Temporal 243 cluster).
• 27× Expected a TypeError (missed argument-validation negatives), 26× Cannot convert undefined or null.

Suggested order

1. Missing constructor(s) behind the 138 (start with DurationFormat/Locale). 2. Temporal↔Intl field resolution (Temporal 243 / Insufficient fields 84). 3. NumberFormat/DateTimeFormat instance-method gaps (Cannot-read-undefined 106). 4. argument-validation TypeErrors.

Measure: scripts/test262_subset.py --dir intl402 --all-features (node v26). Prompt scaffold: ~/perry-bench/prompts/test262-intl402-gaps.md.

[proggeramlug]

Status update (2026-06-18)

Progress on the intl402 tail since this was filed:

• feat(intl): implement Intl.Locale constructor (#5344) #5359 merged — Intl.Locale constructor (one of the missing constructors behind the 138× undefined is not a constructor).
• feat(intl): implement Intl.DurationFormat (#5344) #5405 merged — Intl.DurationFormat (the DurationFormat 104 cluster, the other top missing constructor).

That completes most of suggested-order step 1 (missing constructors) — the two highest-ROI missing constructors (Locale + DurationFormat) are now in.

Additional Intl surface is in local WIP on fix/intl402-canonical-formattoparts-5298 (getCanonicalLocales, supportedValuesOf, formatToParts + ListFormat / RelativeTimeFormat / PluralRules), not yet a PR.

Remaining (steps 2–4), unchanged:

• Temporal↔Intl field resolution — Temporal 243 / Insufficient fields 84
• NumberFormat / DateTimeFormat instance-method gaps — Cannot read properties of undefined 106
• argument-validation TypeErrors — Expected a TypeError 27

Numbers above are as-of-filing; the authoritative re-measure (scripts/test262_subset.py --dir intl402 --all-features) comes from the bench sweep. Keeping this open as the intl402 tracker.