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Answer Error.prototype for Object.getPrototypeOf of an Error - #2058
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An Error's view had no prototype or a holder of its default name and message, so Object.getPrototypeOf(new Error()) was Object.prototype or a fresh object. A view of an error built as an Error, whose prototype is still the one its view starts with, now answers Error.prototype. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Verification for 1b5c905 (rebased onto origin/main 4206155). Differential. Corpus Zero-cost gate against main 4206155, full sets: bench, self and the TypeScript corpus.
No typed benchmark changes. The gate's FAIL verdict on the corpus set comes from those 56 programs alone: the gate ran without |
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Object.getPrototypeOf of an Error answers Error.prototype when the error's view was built from its fields and its prototype is still the object the view was built with. After Object.setPrototypeOf(error, {}), it answers the object that was set.
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Natively,
Object.getPrototypeOf(new Error())answeredObject.prototypeor a fresh holder object instead ofError.prototype. The view of an error built as an Error, while its prototype is still the one the view starts with, now answersError.prototype. Other error kinds keep their current behavior, because their prototypes are not modeled.The change is runtime-only, in
scr_dyn_get_prototype(scr_json.c).Evidence: corpus
8115-error-prototype-identity.js, with its order baseline and CI cost recorded. It fails on main and matches Node in the plain and sanitized lanes.Zero-cost gate against main, full sets (bench, self and the TypeScript corpus): bench and self are identical. 56 corpus programs that reach
scr_dyn_get_prototypechange in their release executable only, from +0 to +8.5 KB (median +288 B). IR and LLVM are identical everywhere. Details are in the verification comment.🤖 Generated with Claude Code