Classes transpiled down to es5 can't extend native es6 classes

[fabiospampinato]

TypeScript Version: 3.4.1

Search Terms: extend class transpiled es5

Code

// Part 1
function extender ( myClass ) {
  return class extends myClass { }
}

// Part 2
const Extended = extender ( class {} );
new Extended ();

The following code:

• Works, if transpiled to es6+
• Works, if transpiled to es5 too
• Doesn't work, if the first part gets transpiled to es5 while the second part is still using es6. The first part may very well be a class decorator exported by some third-party package. The problem is that when transpiled down to es5 classes can't extend native classes.

Playground Link: N/A, the playground is too limited for this

[DanielRosenwasser]

I believe this is a duplicate of #17088.

[fabiospampinato]

It looks like it is, thanks.