Fix Proxy construct trap receiving Array-constructor-mangled arguments#2670
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The [[Construct]] internal method built the trap's argumentsList via the Array constructor, so a single numeric argument hit Array(length) semantics: `new proxy(42)` handed the construct trap an empty array with length 42 instead of [42], and `new proxy(1.5)` threw a spurious RangeError (invalid array length). Per spec step 7 (https://tc39.es/ecma262/#sec-proxy-object-internal-methods-and-internal-slots-construct-argumentslist-newtarget) the list must be created with CreateArrayFromList; use ConstructFast like the [[Call]]/apply path already does. test262 misses this because built-ins/Proxy/construct/call-parameters.js constructs with two arguments. V8 (node 24) confirms the fixed behavior: new p(42) -> args [42], new p(1.5) -> args [1.5]. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01EsHuKuE4UihKZp5HYapDHE
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This was referenced Jul 15, 2026
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JsProxy.[[Construct]]built the trap'sargumentsListwithArray.Construct, i.e. JSArray(...)constructor semantics. A single numeric argument therefore hit theArray(length)path:Per spec step 7 the list must be created with CreateArrayFromList — now uses
ConstructFast, the same helper the[[Call]]/apply path already uses.test262 misses this because
built-ins/Proxy/construct/call-parameters.jsconstructs with two arguments. Cross-checked against node 24 / V8.🤖 Generated with Claude Code
https://claude.ai/code/session_01EsHuKuE4UihKZp5HYapDHE