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kotlinlang

hey! I'm trying to write a generic function to set a default value on a nullable property of an immutable object and I have two obstacles:
- can I constraint a type so it is a data class (implements a copy constructor)?
- can I address the right property in the copy constructor using the KProperty?

This is what I have so far:
```
    fun &lt;T: ???, R&gt; T.setDefault(prop: KProperty1&lt;T, R&gt;, defaultValue: R): T =
        prop.get(this)?.let { this } ?: copy(??? = defaultValue)
```
P.S. maybe this I'm trying to do is stupid/not worth it, feel free to point it out

I assume the default can't be defined on the data class definition  itself?

Data classes do not define a copy constructor, only a copy function, and the generated copy functions for different classes are not guarunteed to have the same signature. There's nothing (from a definition/signature standpoint) that is common among all data classes, so restricting to data classes isn't possible (and wouldn't be useful if it was possible).

`data` is a compiler code generation feature. At runtime, there is nothing special about data classes.

I understand, thanks, so there's no way to make this generic, right?