Private properties are inaccessible from the <template> region

[NullVoxPopuli]

🐞 Describe the Bug

Repro

I expect this to work:

import Component from '@glimmer/component';
import { tracked } from '@glimmer/tracking';
import { on } from '@ember/modifier';

export default class HelloWorld extends Component {
  @tracked count = 0;

  #increment = () => this.count += 1;

  <template>
    <p>You have clicked the button {{this.count}} times.</p>

    <button type="button" {{on "click" this.#increment}}>Click</button>
  </template>
}

but instead we get an implicit undefined replacement

when used wit the on modifier, you get this error:

can't access property "bind", userProvidedCallback is undefined

but if you use a property in the template, i.e.: {{this.#foo}}, undefined renders, and nothing tells you anything is wrong

🌍 Environment

• Ember: 6.8.x