chakra-core/ChakraCore

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

Open

#357 建立於 2016年2月19日

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 (4 留言) (0 反應) (0 負責人)JavaScript (9,000 star) (1,374 fork)batch import
BugSeverity: 2help wanted

描述

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).

貢獻者指南

技術棧
javascriptcpp
領域
backend
議題類型
bug
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
4
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
3-5 days
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
JavaScriptC++parser knowledgeECMAScript spec
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
30
研究方向
Study the ECMAScript spec's static semantics for blocks and function bodies, specifically the second bullet point. Examine ChakraCore's parser implementation to understand how early errors for variable declarations are currently handled. Look for where `var` declarations are checked against lexical declarations, and add the missing error when a `var` hoists past a `let`, `const`, `class`, or function declaration. The relevant files are likely in the parser directory, e.g., 'lib/Parser/Parse.cpp' or similar. Review existing tests for similar errors to understand the pattern.