Variable self assignment not removed (x = x)

[Ahnfelt]

Bug report or Feature request?

Feature request.

Version (complete output of terser -V or specific git commit)

Online REPL 5th of October 2021

Complete CLI command or minify() options used

Default options:

{
  module: true,
  compress: {},
  mangle: {},
  output: {},
  parse: {},
  rename: {},
}

terser input

export function f(x) {
    x = x;
}

terser output or error

export function f(f){f=f}

Expected result

export function f(f){}

[jridgewell]

Do you see code like f = f as the output of some build step?

[fabiosantoscode]

Sometimes Terser itself outputs x=x IIRC

[Ahnfelt]

Sometimes Terser itself outputs x=x IIRC

Yeah, e.g. this produces the exact same output:

export function f(x) {
    const y = x;
    const z = y;
    x = z;
}

[jridgewell]

Alright, let's add a simple assignment case.