tc39/ecma262

Index conversion in ArrayAccumulation

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#1,095 opened on Feb 9, 2018

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good first issueneeds consensusneeds test262 testsnormative change

Description

ArrayAccumulation computes the array index via ToString(ToUint32(nextIndex+padding)). This means the index may become 2^32-1. But that's not a valid array index anymore since it is the max value of the length property.

Contributor guide

Tech stack
javascript
Domain
documentation
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
ECMAScript spec understandingarray index semantics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
The issue concerns the ArrayAccumulation algorithm in the ECMAScript specification. To investigate, read the algorithm at the linked section, understand how index conversion using ToUint32 and ToString works, and verify whether the resulting index can be 2^32-1 (which is not a valid array index). Then propose a fix, such as capping the index or adjusting the algorithm to handle edge cases. Refer to the spec text and any related discussions in the issue comments.
Index conversion in ArrayAccumulation · tc39/ecma262#1095 | Good First Issue