Typecheck for argument/dictionary field default values

[saschanaz]

interface mixin Mixin {
  void op(optional boolean arg = 3); // no!
};

dictionary Dict {
  DOMString str = true; // no!
};

See also whatwg/webidl#750 (comment).

[TG1999]

Hi I will like to work on this issue, can you explain how can I solve this issue ?

[saschanaz]

I think this one is rather complex and not adequate for first contributions because we should make sure typedefs and unions are correctly examined. We'll want to modify *validate() in lib/productions/argument.js and check whether the argument type allows the value type.

Note for me: Maybe some helper functions:

• valueToType(defaultValue): Receives a default value and returns the possible type(s) of it.
• includesType(baseType, targetType): Receives two types and returns a boolean that indicates the baseType includes targetType or not. Should include some caching to prevent infinite recursion (fix(validation): prevent infinite recursion #362 😁).