Kotlin 2.0.0 - Typealias declaration is target type when typealias is a Composable function in a different module

[eygraber]

There are 3 commits in this sample project.

The first commit (f451dc8) has a typealias that is a Composable function in foo/src/main/java/com/example/foo/Foo.kt

class FooHolder(
    val foo: Foo,
)

typealias Foo = @Composable ((id: Long) -> Unit) -> Unit

FooHolder is referenced in app/src/main/java/com/example/myapplication.MainActivity.kt

@ExampleAnnotation
abstract class Example {
    abstract val fooHolder: FooHolder
}

The KSP processor looks at the primary constructor of FooHolder and prints out whether it is a typealias, and what the type is:

val symbols = resolver.getSymbolsWithAnnotation(ExampleAnnotation::class.qualifiedName!!)

for (symbol in symbols) {
    if (symbol is KSClassDeclaration) {
        val exampleClass =
            symbol.getAllProperties()
                .first().type.resolve().declaration as KSClassDeclaration

        exampleClass
            .primaryConstructor
            ?.parameters
            ?.find { it.name?.getShortName() == "foo" }
            ?.let { param ->
                logger.error("isTypeAlias(${param.type.resolve().declaration is KSTypeAlias}) - ${param.type}")
            }
    }
}

In this case running ./gradlew assembleDebug prints:

isTypeAlias(false) - Function1<Function1<[@kotlin.ParameterName] Long, Unit>, Unit>

The second commit (cedd6ef) removes the Composable annotation from Foo. Running prints:

isTypeAlias(true) - Foo

The third commit (63e6de2) adds back the Composable annotation to Foo, but moves Foo and FooHolder into the app module. Running prints:

isTypeAlias(true) - Foo

This happens with both KSP1 and KSP2.

There is a separate branch called 1.9.24 (which branches off of the first "broken" commit) that uses Kotlin 1.9.24. Running prints:

isTypeAlias(true) - Foo

It's unclear to me if that's because of something that was introduced in KSP 2.0.0-1.0.21 or because the Compose compiler changed to org.jetbrains.kotlin.plugin.compose (or both).

[julioromano]

FYI: Problem persists with KSP 2.0.0-1.0.22

[eygraber]

Looks like this is fixed in newer versions of KSP / Kotlin.