How do I find check if a constructor parameter is ...

# reflect

[dstarcev]

How do I find check if a constructor parameter is also a property?

[udalov]

Manually, i.e. find a property with the same name

[udalov]

We consider being declared in a primary constructor an internal implementation detail of a property, so there's no information in the binary metadata to differentiate between

class A(val x: String)

and

class A(x: String) {
    val x: String = x
}

[dstarcev]

How do I differentiate

class A(x: String) {
    val x: String = x
}

and

class A(x: String) {
    val x: String = "not x"
}

?

[udalov]

You can't do that either, because of the reason I described. Basically, to the outside observer, a class has primary constructor parameters and properties but it cannot tell how they are related. But this is not a bug, it's by design at the moment. Do you have a use case where it's necessary to know if a property is declared in the constructor?

[dstarcev]

Obfuscating a class I want to keep the same names for parameters of the primary constructor and their according properties if such

[dstarcev]

otherwise kotlin reflection will be broken on the class, as @Eugenio said in another thread

[dstarcev]

or at least tools such as Jackson that may rely on these names may break

[udalov]

No, the question in that thread was whether Kotlin reflection would break if the property name differs from the backing field name (at least that's what I was answering :) ). Nothing would break if the property name differs from the "related" primary constructor parameter name, because as I said, there's no information on that relation after the class is compiled, so no tool can rely upon it

[Eugenio]

Isn't there a way to keep the parameter names when compiling for Java8?

[udalov]

There is (-java-parameters), but I don't see how it's relevant to this discussion because here only the Kotlin metadata is affected