Feature Request: Support trait types as a type parameter

[acioc]

Currently, we have a custom datatype MyDataType<T> = SomeValue(value: T) | NoValue(msg: string)

I wanted to have a custom trait, like

  trait {:extern "MyTrait"} MyTrait {
    method {:extern "SomeMethod"} SomeMethod()
  }

Essentially, we can implement MyTrait multiple ways and allow MyDataType to take in any of them (like we would with an interface in other languages). Although VSCode codes not (currently) show any errors, when compiling I get error : compilation does not support trait types as a type parameter; consider introducing a ghost

I was hoping this functionality could be supported, so we don't need to create custom
datatype MyDataTypeForMyTrait<T> = SomeValue(value: MyTrait) | NoValue(msg: string)
For every custom trait we create

[seebees]

@robin-aws I think that this is closed by #1499?