hey, so i’m currently in the process of writing a ...

# arrow-meta

[appmattus]

hey, so i’m currently in the process of writing a kotlin compiler plugin using meta, although struggling with my approach for modifying IR.

[appmattus]

the gist of what i’m trying to do is to alter a function call, someFunction in this example, to automagically specify a missing parameter, as an example:

class MyClass : ViewModel() {
    val result = viewModelScope.someFunction()
}

fun CoroutineScope.someFunction(value: String? = null) {
    println(value)
}

With the idea being I can populate the value in someFunction based on something else in the class - for example the class name.

Intercepting the IrCall seems easy enough as well as adding the additional argument to the call:

private val Meta.somePlugin: CliPlugin
    get() = "Some Plugin" {
        meta(
            irCall { irCall ->
                if (irCall.symbol.owner.kotlinFqName.asString() == "someFunction") {
                    // do the magic argument adding
                 }
            }
        )

The problem I’m having though is there seems no obvious way to figure out the parent of an `IrCall`; unlike IrFunction there is no parentClassOrNull

Is there a better approach for being able to figure out where the IrCall came from or performing the transformation?

I’m assuming I should be looking at using transformChildren although just not 100% sure what type of IrElement I should apply that to!

[raulraja]

Hi @appmattus, Instead of intercepting irCall you could intercept irDeclaration (the parent) and the on each intercepted declaration search inside for calls

[appmattus]

ah thanks, got it working

i first tried irDeclaration but noticed the IrCall was found twice, once for the property and the other for the backing field of the property.

now i’m specifically using transformChildren on irProperty. it’s great to see the class file transformed 🙂

meta has certainly made the process of creating a compiler plugin seem pretty trivial, great work

[raulraja]

We hope to improve it once the new FIR K2 is stable and we can develop utilities for it like the ones we will port to meta from our tests at arrow-reflection https://github.com/arrow-kt/arrow-reflection/tree/main/arrow-reflect-annotations/src/main/kotlin/arrow/meta/samples

[raulraja]

If it all goes well this would add macro suport to the frontend or similar features that can interop with IDEA as compiler plugins.