google/closure-compiler

Array constructor with length is not eliminated

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#4,046 opened on Jan 22, 2023

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Description

Consider the code:

/** @const {!Array<number>} */
const a = [1];

/** @const {!Array<number>} */
const b = Array(10);
b[0] = 2;

/** @const {!Array<number>} */
const c = [];
c.push(3);

/** @const {!Array<number>} */
const d = Array(10);
d.push(4);

When compiled with

yarn google-closure-compiler -O ADVANCED --js a.js --rewrite_polyfills=false

we get

Array(10)[0]=2;Array(10).push(4);

Arrays created with the Array(len) constructor are not eliminated.

google-closure-compiler version: v20230103

Contributor guide

Research direction
Investigate the DeadCodeElimination pass to see why 'Array(length)' patterns are not being removed, and consider adding a similar case for array constructor with length argument.
Tech stack
javajavascript
Domain
compilers
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
Mostly clear
Prerequisites
JavaScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60