getDefaultProps() breaks the native class model of Ember Components.

[ariesshrimp]

BUG REPORT

• [ x ] I have ensured that the issue isn't already reported
• [ x ] I have confirmed that the issue is reproducible with the latest released version
• [ x ] I have deleted the FEATURE REQUEST / CODE CHANGE section

Summary

getDefaultProps() breaks the native class model of Ember Components.

Expected Behavior

class Example extends Component {
  layout = hbs`<p>{{this.example}}</p>`
  propTypes = {
    example: PropTypes.string
  }
  getDefautProps() {
    return {
      example: "this string should be set as the value of this.example"
    }
  }
}

{{-- <p>this string should be set as the value of this.example</p> --}}
<Example/>

{{-- <p>something else</p> --}}
<Example @example="something else"/>

Actual Behavior

{{-- TypeError --}}
<Example @example="something else"/>

prop-types.js:112 Uncaught (in promise) TypeError: defaults.forEach is not a function
    at Example.init (prop-types.js:112)
    at Example.superWrapper (utils.js:366)
    at Example.init (component-prop-types.js:21)
    at Example.superWrapper [as init] (utils.js:366)
    at initialize (core_object.js:87)
    at Function.create (core_object.js:684)
    at FactoryManager.create (container.js:545)
    at CurlyComponentManager.create (glimmer.js:5437)
    at Object.evaluate (runtime.js:1494)
    at AppendOpcodes.evaluate (runtime.js:70)

Possible Solution

Steps to Reproduce

https://codesandbox.io/embed/54ojpz0rox

ember new my-app -b @ember/octane-app-blueprint
cd my-app && ember install ember-prop-types
# add component as shown in above examples
ember serve # runtime error in browser

---

• [ x ] Include the contents of your package.json file
• [ x ] Steps to reproduce:

Context

I want type checking of props passed to my components in templates. Static type checking is not there yet for ember templates. So it's gotta be run-time. But I don't want to be forced to choose between run-time checks and class syntax

Environment

• [ x ] I am using the latest released version (can check with npm ls <package-name>)
• I am using these browsers:
  • [ x ] Latest Chrome
• [ x ] My version of Node is: v10.15.2
• [ x ] My version of npm is: 6.4.1
• [ x ] My OS is: linux-gnu
• [ x ] Include the contents of your package.json file

[EWhite613]

We moved off this in native class model as we just use typescript to define the interface and

class Example extends Component {
  layout = hbs`<p>{{this.example}}</p>`
  @argument example: string = "this string should be set as the value of this.example"
}

and the glimmer approach is to go through args so we have something like

interface ExampleArgs {
  example: string
}
class Example extends Component<ExampleArgs> {
  layout = hbs`<p>{{this.example}}</p>`
  example: string

  get example (): string {
  return this.args.example ?? 'this string should be set as the value of this.example'
  }
}