What is the reason that Kotlin Fir visitors use `Nothing?` to denote “no data” rather than `Unit`? ...

# compiler

[Marc Knaup]

What is the reason that Kotlin Fir visitors use Nothing? to denote “no data” rather than Unit?

https://github.com/JetBrains/kotlin/blob/0e4e5ac287c3836ca4434c2c6f626b9145c284e5/compiler/fir/tree/gen/org/jetbrains/kotlin/fir/visitors/FirVisitorVoid.kt#L128

[dmitriy.novozhilov]

there is no sematic difference, but pass null to element.accept(visitor, null) is easier than Unit

[Marc Knaup]

Thanks!
I was hoping that there's a "right way" for defining a parameter as irrelevant, like Unit for function returns. 😁

But if both are equally okay then also good.