chakra-core/ChakraCore

Hoisting a var declaration past a lexical declaration of the same name should be a SyntaxError

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#357 opened on Feb 19, 2016

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 (4 comments) (0 reactions) (0 assignees)JavaScript (1,374 forks)batch import
BugSeverity: 2help wanted

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Description

Second bullet point of block static semantics and similarly for function body static semantics.

E.g.

let x;
{
    var x; // error (already works)
    let y;
    var y; // should be an error (doesn't work)
    {
        var y; // should also be an error (doesn't work)
    }
}

This applies for var declarations hoisting past all lexical declarations, i.e. let, const, class, function (and generators and async functions).

Contributor guide

Research direction
Study the ECMAScript spec for block level early errors and locate where similar checks are implemented (e.g., for var x inside a block with let x). Then add the missing check for var declarations hoisting past lexical declarations of the same name.
Tech stack
javascript
Domain
compilers
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.
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
JavaScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65