test262 built-ins tails — 827 fails (95.5%): RegExp/Object/Array/Promise/Function/String/Proxy #5347

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1. proggeramlug

   added 5 commits that reference this issue on Jun 18, 2026

   fix(runtime): reject Symbol argArray in Function.prototype.apply (#5347…

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   15e0a22

   fix(hir): throw TypeError for Reflect.apply with omitted argumentsList (

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   a70c34f

   fix(runtime): throw TypeError for Object.setPrototypeOf on non-extens…

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   f863afd

   fix(runtime): walk prototype chain for Reflect.get accessor receiver …

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   38d7dda

   fix(runtime): Array.from on a raw ArrayBuffer yields an empty array (#…

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   0efe48d
2. proggeramlug commented on Jun 18, 2026

   

   proggeramlug

   on Jun 18, 2026

   ContributorAuthor

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   Status update (2026-06-18)

   Progress on the built-ins tails since this was filed:

   • fix(runtime): reject Symbol argArray in Function.prototype.apply (#5347) #5360 merged — reject Symbol argArray in Function.prototype.apply (Function tail / missed-negative).
   • fix(hir): throw TypeError for Reflect.apply with omitted argumentsList (#5347) #5392 merged — Reflect.apply with omitted argumentsList throws TypeError.
   • fix(runtime): throw TypeError for Object.setPrototypeOf on non-extensible target (#5347) #5396 merged — Object.setPrototypeOf on a non-extensible target throws TypeError.
   • fix(runtime): walk prototype chain for Reflect.get accessor receiver rebind (#5347) #5399 merged — Reflect.get walks the prototype chain for accessor receiver rebind.
   • fix(runtime): Array.from on a raw ArrayBuffer yields an empty array (#5347) #5404 merged — Array.from on a raw ArrayBuffer/SharedArrayBuffer yields an empty array (not array-like) — test262 Array/from/items-is-arraybuffer.

   These chip the Expected a TypeError 84 (missed-negatives) and Object/Array/Function/Reflect clusters.

   Remaining (umbrella), unchanged:

   • RegExp 115 — property-escapes tail (~80) + regexp-v-flag (not yet measured/implemented)
   • Temporal 106 (self-validate)
   • Object / Array / Promise / Function / String / Proxy method tails
   • the (no output) 83 cluster — needs per-case look (silent wrong-result / early exit)

   This is an umbrella tracker (95.5%); keeping it open and splitting per-constructor work as picked up. Authoritative numbers from scripts/test262_subset.py --dir built-ins.
3. proggeramlug

   added 4 commits that reference this issue on Jun 18, 2026

   fix(codegen): unknown builtin-namespace member reads as undefined, no…

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   2927c09

   fix(codegen): unknown builtin-namespace member reads as undefined, no…

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   2a52cf1

   fix(codegen): unknown builtin-namespace member reads as undefined, no…

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   12884ec

   fix(string): #5347 — substr coerces args via ToIntegerOrInfinity (#5523)

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   996453e
4. proggeramlug commented on Jun 21, 2026

   

   proggeramlug

   on Jun 21, 2026

   ContributorAuthor

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   Status update (2026-06-21)

   • fix(string): #5347 — substr coerces args via ToIntegerOrInfinity #5523 merged — String.prototype.substr now coerces both args via ToIntegerOrInfinity (ECMA-262 Annex B.2.3.1) instead of a raw fptosi on the NaN-box. Fixes the missed valueOf/Symbol negatives (length-to-int-err, start-to-int-err) and the silent wrong-results (length-falsey, length-undef, start-and-length-as-numbers).

   annexB/built-ins/String/prototype/substr: 8 → 13 of 14 pass. The lone remaining surrogate-pairs case needs lone-surrogate / WTF-8 support (the known categorical gap), so it stays out of scope here. Chips the String tail + the Expected a TypeError missed-negatives cluster.

   Umbrella stays open; remaining per-constructor tails (RegExp / Temporal / Object / Array / Promise / Function / Proxy + the (no output) cluster) unchanged.
5. proggeramlug

   added 2 commits that reference this issue on Jun 22, 2026

   fix(object): #5347 — Object.assign/spread with an array source no lon…

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   21abc74

   fix(object): #5347 — Object.assign/spread with an array source no lon…

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   31c24f6
6. proggeramlug commented on Jun 23, 2026

   

   proggeramlug

   on Jun 23, 2026

   Last edited by proggeramlug

   ContributorAuthor

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   Re-measured 2026-06-23 on an internal Linux sweep host (perry 0.5.1204): built-ins persistent standing gap 805 (regression #5579 excluded). Closing this umbrella in favor of concrete per-constructor tickets:

   • test262 built-ins/RegExp — 94 fails (property-escapes + exec internals) #5586 RegExp (113)
   • test262 built-ins/Temporal — 61 fails (range/precision validation + missed-negatives) #5587 Temporal (106, self-validate)
   • test262 built-ins/Object — 48 fails (ToObject boxing / assign / descriptors) #5588 Object (79)
   • test262 built-ins/Array — 67 fails (exotic length/index, prototype-as-receiver) #5589 Array (71)
   • test262 built-ins/Promise — 38 fails (all/allSettled capability + then-iteration) #5590 Promise (60)
   • test262 built-ins tail — 133 fails (String/Function.toString/Proxy/JSON/TypedArray/AsyncFromSyncIterator) #5591 tail: String/Function.toString/Proxy/JSON/AsyncFromSyncIterator (210)

   Cross-cutting reason clusters map to existing tickets: missed arg-validation TypeErrors → #3146; missed-negatives → #3570/#3571; Object boxing → #3986.
7. proggeramlug

   closed this as completedon Jun 23, 2026