I want to do that allows partial implementations n...

# language-proposals

[zsqw123]

I want to do that allows partial implementations not actually written in class, eg:

class Foo {
    api fun bar(): String
}

// write in another file
impl fun Foo.bar() = "bar"

The reason I want to implement this is that I want the actual implementation of the bar function to be implemented by KSP generated code, and I want it to be a member function that does not require import and does not need to wait for KspDebug to finish executing before calling to

[hfhbd]

What about the existing inheritance options, interface or even an open/abstract class?
Alternatively you could do it with an compiler plugin, so afaik there is no need to change the language.

[zsqw123]

Maybe kotlin language advocate final rather than open/abstract.😂 and I don't really want it to have subclasses. Using KCP also requires synchronous development of IDE plugins to avoid IDE errors for not implemented, and many languages actually have similar api and implementations separate logic(like header)
And, api separation is actually a way to explicitly declare api. it is also a easy way to optimizing compiler's tracking of abi changes for incremental compile.
It also provide a simple way to compare the api changes between old and new versions.
Also, if adding a new keyword doesn't good, can we consider existing external keyword? Not just for interacting with native, but also for this additional api/impl seperation?

[ephemient]

class Foo {
    fun bar(): String = barImpl()
}

internal fun Foo.barImpl() = "bar"

[asdf asdf]

Seems a lot like expect/actual , although might be sort of weird to use it on just a single platform

[zsqw123]

yeah!👍 it is expect/actual, but I want to use it in single sourceset(platform), and maybe when no actual impl, it will not show the ide error

[Derek Peirce]

This has value over an interface because you can declare a constructor that your other classes can access directly, while still generating the implementation of some methods. You can't do the same for a purely generated implementation class.