Strange Bug _ember_modifier__WEBPACK_IMPORTED_MODULE_1__.setModifierManager is not a function

[luxzeitlos]

This is a very strange bug, and I'm not really sure where this should belong.
But we have a reproduction.

It occurs if:

• @ember/modifier'; is imported in routes/application.js
  • import { on } from '@ember/modifier';
• ember-autofocus-modifier/modifiers/autofocus'; is indirectly imported routes/application.js
  • import import Navigation from 'my-app/components/navigation'; is present in routes/application.js
  • import autofocus from 'ember-autofocus-modifier/modifiers/autofocus'; in components/navigation.js
• "ember-modifier": "^4.0.0", is present in package.json, no import necessary

Then the app fails to boot with:

Uncaught TypeError: _ember_modifier__WEBPACK_IMPORTED_MODULE_1__.setModifierManager is not a function

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