💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

const noop = (val) => val; 
let hasX;

@noop
class Foo {
  static {
    hasX = o => #x in o;
  }
  #x;
}

console.log(hasX(new Foo));

REPL

Configuration file name

No response

Configuration

{
  "plugins": [["@babel/plugin-proposal-decorator", { "version": "2023-05" }]]
}

Current and expected behavior

Actual: The output code throws syntax error: "Private field '#x' must be declared in an enclosing class".
Expected: It prints true.

Environment

REPL

Possible solution

This is an inherent limit of our current "class separation" approach, where we move non-static elements into a new class. It does ensure that class brand check is still working when defined in the static element, but the instance brand check is broken as the private element is defined in the inner class.

Since a class decorator can mutate the class this value, we might have to partially transform every features involved with class this: private accesses, private brand checks, and all this expresssions and class bindings.

Additional context

No response