Unexpected token ! in JSON at position 0

undefined:1
!undefined
^

SyntaxError: Unexpected token ! in JSON at position 0
    at JSON.parse (<anonymous>)
    at MethodParser.getUnaryExpression (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\AbstractParser.js:372:16)
    at MethodParser.getValue (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\AbstractParser.js:399:21)
    at MethodParser.getParam (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:39:26)
    at C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:58:27
    at Array.map (<anonymous>)
    at MethodParser.getParams (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:58:8)
    at MethodParser.parseMethodProperty (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:74:25)
    at C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:66:16
    at Array.forEach (<anonymous>)
    at MethodParser.parseObjectExpression (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:63:21)
    at MethodParser.parse (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\AbstractParser.js:51:14)
    at MethodParser.parse (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\MethodParser.js:21:13)
    at ScriptParser.parseFeature (C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\ScriptParser.js:622:14)
    at C:\Users\johan\dev\hy-elements\node_modules\@vuedoc\parser\lib\parser\ScriptParser.js:364:39
    at Array.forEach (<anonymous>)

The same error like again like in my other issue, but this time it comes from this a default value als param:

// ...
methods: {
  togglePaused(doPause = !this.paused) { // <- error

  },
},
// ...

its also not possible to use the this reference in data() e.g.

data() {
  return {
    name: 'foo',
    name2: this.name,
  };
},