tc39/ecma262

Removal of Object type-check from GetIterator() algorithm

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#746 opened on Dec 6, 2016

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good first issueneeds consensusneeds specification text

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Description

The If Type(iterator) is not Object, throw a TypeError exception. step is generally not implemented by engines, see https://jsfiddle.net/gj3uaw1t/ for an example. V8 does implement this step for yield*, but not other uses of GetIterator().

It would be cool if we could remove this from the spec and have common behaviour among implementations (it seems a recent version of SpiderMonkey has added the typecheck, breaking compatibility between FF and Chrome/Safari in this very unlikely situation).

Contributor guide

Research direction
Review the GetIterator algorithm in the ECMAScript specification, check implementations in V8 and SpiderMonkey, and evaluate impact of removing the Object type check step.
Tech stack
javascript
Domain
documentation
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
JavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40