babel-plugin-minify-dead-code-elimination `SequenceExpression` use case

SequenceExpression in ExpressionStatement containing UnaryExpression(void 0) does not remove dead code.

I realize this is a small use case, but if an ExpressionStatement contains a SequenceExpression with void 0 it can be removed with no worry of side-effects.

  a, b, c, d, void 0;

should be:

  a, b, c, d;

Thanks for reading!

-Josh

[boopathi]

It’s an unsafe transformation -

function f1() {
  return 1, 2, void 0;
}

function f2() {
  return 1, 2;
}

console.log(f1(), f2()); // will print undefined, 2

[kangax]

This is similar to https://github.com/babel/babili/pull/197 where we remove undefined only when it’s in a “safe” context.