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why am I getting `Unresolved reference 'copy'.` in the code below :
<https://play.kotlinlang.org/#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|https://play.kotlinlang.org/#eyJ2ZXJzaW9uIjoiMi4wLjAiLCJwbGF0Zm9ybSI6ImphdmEiLCJhcmdzIj[…]50bG4oY2NjMSlcbiAgICAvL3ByaW50bG4oZGRkMSlcbiAgICBcbn0ifQ==>

Because `Result` is not a data class. Thus, it doesn't have a `copy` method.

Make sense. In this case is it possible to get the inner data class??

Not without casting.  For what its worth, this doesn't seem like a good pattern.   Using subclasses for this will complicate things.  You can try it <https://play.kotlinlang.org/#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|this way>, depending on what your goal is.