Dead code not removed.

[underfin]

Description

The dead code not removed. I found similar issue #598, but it not same case.

Input

var flag_A = 1 << 0
var flag_B = 1 << 1
var flag_C = 1 << 2

const used = flag_A | flag_B

if(used & flag_A) {
    console.log('flagA')
    a()
}
if(used & flag_B) {
    console.log('flagB')
}
if(used & flag_C) {
    console.log('flagC')
    a()
}

function a () {
 console.log('2322')
}

Output

(() => {
  // input.js
  var flag_A = 1 << 0;
  var flag_B = 1 << 1;
  var flag_C = 1 << 2;
  var used = flag_A | flag_B;
  if (used & flag_A) {
    console.log("flagA");
    a();
  }
  if (used & flag_B) {
    console.log("flagB");
  }
  if (used & flag_C) {
    console.log("flagC");
    a();
  }
  function a() {
    console.log("2322");
  }
})();

Expected Output

This is output emited by terser.

function o(){console.log("2322")}console.log("flagA"),o(),console.log("flagB");

[evanw]

This isn't currently supported. If you want to do constant propagation like this, you can run Terser on the output of esbuild.

[underfin]

Thanks for your reply, i will use terser before esbuild support it.

[evanw]

Closing this issue since your example should work now that #1981 has been fixed, at least as long as you use const instead of var. That code now minifies to this when tree-shaking is active:

console.log("flagA"),l();console.log("flagB");function l(){console.log("2322")}