facebookarchive/prepack

Prepack emits if-statements with no consequent or alternate code

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#2,220 建立於 2018年7月6日

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 (3 留言) (0 反應) (0 負責人)JavaScript (14,268 star) (520 fork)batch import
Instant Renderenhancementhelp wantedlevel 1 (super easy)priority: lowserializer

描述

This

(function () {
  let n = global.__abstract ? __abstract("number", "23") : 23;
  if (n === 42) {
    let d = Date.now(); // dead pure generator entry
  }
})();

prepacks to

if (23 === 42) {}

which is obviously suboptimal.

During its fixpoint computation, the visitor should not visit the condition until at least one generator entry cannot be omitted.

貢獻者指南

技術棧
javascript
領域
performance
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。
3
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。
1-3 hours
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
JavaScript knowledgeCompiler architecture basics
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。
40
研究方向
Investigate the fixpoint computation and visitor code in Prepack. Look for the relevant visitor logic that handles if statements and generator entries. Determine how to delay visiting the condition until at least one generator entry is confirmed not omitted. The issue suggests a specific fix in the visitor condition traversal.