From 3.9.1 a compiler bug?

Reproduction: https://github.com/igneosaur/sveltejs-template/tree/terser-compress-await-bug

@igneosaur opened https://github.com/sveltejs/template/issues/59 thinking it was terser.

If you clone and change sveltejs from 3.9.1 to 3.9.0 it works fine.

[Conduitry]

It looks to me like a terser bug involving invalid inlining of a function call.

  let current_component;
  // ...
  function get_current_component() {
    if (!current_component)
    throw new Error(`Function called outside component initialization`);
    return current_component;
  }

is turning into

      const n = function () {
        if (!n) throw new Error('Function called outside component initialization');
        return n
      }();

I haven’t tracked down what about the output changed between Svelte 3.9.0 and 3.9.1 to cause this to happen, but it does appear to be a bug in Terser.

[Conduitry]

The Terser bug was fixed in 4.3.2.