Bug report

Version (complete output of terser -V or specific git commit): https://try.terser.org/ / terser 5.7.0

Complete CLI command or minify() options used

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

terser input

function breaks_terser() {
  const t = [];
  (Math.random() < 0.5 ? t : []).push("lengthisnownolongerzero")
  return 1 <= t.length
}
const possible_outputs = [];
for (let i = 0; i < 100; i++) {
  possible_outputs.push(breaks_terser());
}
console.log([...new Set(possible_outputs)]);

terser output or error

function n(){const n=[];return(Math.random()<.5?n:[]).push("lengthisnownolongerzero"),!1}const o=[];for(let e=0;e<100;e++)o.push(n());console.log([...new Set(o)]);

Output when ran: [false]

Expected result

Expected code output: function n(){const n=[];return(Math.random()<.5?n:[]).push("lengthisnownolongerzero"),1<=n.length}const o=[];for(let e=0;e<100;e++)o.push(n());console.log([...new Set(o)]); (same as without unsafe compress option)

Expected output when ran: [true, false] or [false, true]

Context

I wondered today why my slider is not loading the images behind the viewport after the images in the viewport has loaded in production but does so in development. The example code here is really dumbed down to demonstrate the issue. But basically terser assumes the length of the array is going to be zero because it doesn't understand that the ternary statement can change its length.

If the ternary statement is converted to a normal if statement like this the terser output is as expected:

function breaks_terser() {
  const t = [];
  if (Math.random() < 0.5) {
    t.push("lengthisnownolongerzero")
  } else {
    [].push("lengthisnownolongerzero");
  }
  return 1 <= t.length
}
const possible_outputs = [];
for (let i = 0; i < 100; i++) {
  possible_outputs.push(breaks_terser());
}
console.log([...new Set(possible_outputs)]);

According to my interpretation of this: https://github.com/terser/terser#the-unsafe-compress-option using the ternary statement should not break the output when using the unsafe option.