Invert reference type null checks

[surma]

• I've read the contributing guidelines

(This is my first PR digging into the compiler and I’m not 100% sure I did this right. Please point out anything you’d like changed.)

I was playing with reference types and notices that code like this behaves exactly inverted:

if(!someExternref) {
  // This is executed when `someExternref` is *not* `null`
}

It seems like the logic in makeIsTrueish was just using ref.is_null, which would explain the inversion. This PR flips thats logic.

However, I couldn’t run the full tests as the tests still failed with Feature 'gc' is not enabled. despite setting ASC_FEATURES="*". I guess that is the world of experimental features.

PTAL!

[surma]

Accidentally submitted this in the middle of writing the description. Now ready to review :)

[SebastianSpeitel]

Accidentally submitted this in the middle of writing the description. Now ready to review :)

GitHub has draft pull requests.

[surma]

GitHub has draft pull requests.

I know, thank you. I just pressed Cmd+Enter by accident.

[dcodeIO]

Thanks again! :)