Uglifyjs: Uglification of React 16.7.0-alpha (with hooks) seems to be broken

Created on 8 Nov 2018 · 9Comments · Source: mishoo/UglifyJS

Bug report or feature request?
Bug report

Uglify version (uglifyjs -V)
[email protected] (via [email protected])

The following is React-DOM's 16.7.0-alpha code for pushing updates to their Component Update Queue (in React Fibre):

JavaScript input

function Gg(a, b, c, d) {
    a = {
        tag: a,
        create: b,
        destroy: c,
        inputs: d,
        next: null
    };
    null === R ? (R = {
        callbackList: null,
        lastEffect: null
    }, R.lastEffect = a.next = a) : (b = R.lastEffect, null === b ? R.lastEffect = a.next = a : (c = b.next, b.next = a, a.next = c, R.lastEffect = a));
    return a
}

The uglifyjs CLI command executed or minify() options used.
All the default options

JavaScript output or error produced.

  function Vo(e, t, n, r) {
    return e = {
      tag: e,
      create: t,
      destroy: n,
      inputs: r,
      next: null
    },
    jo.lastEffect = null === jo ? (jo = {
      callbackList: null,
      lastEffect: null
    },
    e.next = e) : null === (t = jo.lastEffect) ? e.next = e : (n = t.next,
    (t.next = e).next = n,
    e),
    e
  }

The error is trying to set lastEffect on the jo object, which has not yet been defined. Perhaps a result of UglifyJS trying to reduce the return statement?

Source