jshint/jshint

undeclared variable in es6 comprehension

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#1,656 opened on May 4, 2014

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Description

[for (i of [1,2,3]) i]

Jshint will warn that i is undeclared. Should it? This makes the warning go away:

var i;
[for (i of [1,2,3]) i]

but seems dubious. For example, in the traceur-generated code, the two "i"s are different "i"s. The "i" in the comprehension is scoped to the comprehension.

Contributor guide

Research direction
Investigate how jshint's parser handles ES6 array comprehensions and whether the variable 'i' in the comprehension should be scoped internally rather than leaking to the outer scope. Review the ES6 specification for array comprehension scoping and compare with jshint's current behavior.
Tech stack
javascript
Domain
tooling
Issue type
Bug
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.
1-3 hours
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
JavaScriptES6jshint
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60