is there a way in FIR to create a `ConeClassLikeTy...

# compiler

[Zac Sweers]

is there a way in FIR to create a ConeClassLikeType typed with a FirFunctionTypeRef? Essentially I'm trying to add a supertype like Factory<() -> Unit> in a supertype generation extension, but struggling to find an API for parameterizing an FirClassLikeSymbol with one since FirFunctionTypeRef.coneType doesn't work

[Zac Sweers]

basically trying to add an is FirFunctionTypeRef branch to this when statement and use it in the returned parameterized factory type at the end

https://github.com/ZacSweers/metro/blob/main/compiler/src/main/kotlin/dev/zacsweers/metro/compiler/fir/generators/ProvidesFactoryFirGenerator.kt#L319

[dmitriy.novozhilov]

FirFunctionTypeRef is an unresolved functional type, you should not rely on it.
You need something like this:

fun createFunctionNType(arguments: List<ConeTypeProjection>): ConeKotlinType {
    return FunctionTypeKind.Function
        .numberedClassId(arguments.size - 1)
        .toLookupTag()
        .constructClassType(
            arguments.toTypedArray(),
            isMarkedNullable = false
        )
}

[dmitriy.novozhilov]

There are also KFunction, SuspendFunction, KSuspendFunction in the FunctionTypeKind if you need

[Zac Sweers]

I see, where are the arguments coming from in this case?

[dmitriy.novozhilov]

From you

[dmitriy.novozhilov]

If you want just () -> Unit, then pass class like type with kotlin.Unit as lookup tag

[Jacob Applin]

I was playing around with trying to do something similar last week this is what I came up with:

override fun generateTopLevelClassLikeDeclaration(classId: ClassId): FirClassLikeSymbol<*> {
        val functionSymbol: FirNamedFunctionSymbol = functionsToAlias().single {
            it.name == classId.shortClassName
        }

        return buildTypeAlias {
            moduleData = session.moduleData
            origin = Key.origin
            name = classId.shortClassName
            status = functionSymbol.resolvedStatus
            symbol = FirTypeAliasSymbol(classId)

            expandedTypeRef = functionSymbol.valueParameterSymbols.run {
                buildResolvedTypeRef {
                    coneType = ConeClassLikeTypeImpl(
                        lookupTag = StandardClassIds.FunctionN(size).toLookupTag(),
                        typeArguments = arrayOf(
                            *map { it.resolvedReturnType }.toTypedArray(),
                            functionSymbol.resolvedReturnType,
                        ),
                        isMarkedNullable = false,
                    )
                    annotations.addAll(functionSymbol.annotations)
                }
            }
        }.symbol
    }

[Zac Sweers]

Trying to figure out how to get those from the FirFunctionTypeRef I have at that point. Would I need to convert all the parameters + return type ref into ConeTypeProjections first and pass those on from there?

[Jacob Applin]

I got stuck at the point of trying to copy over the annotations from the source methods ie. @Composable to the generated typeliases

[dmitriy.novozhilov]

If you see the FirFunctionalTypeRef instead of FirResolvedTypeRef then you are on too early stage.
There is a service for type resolution in supertype generation extension (which should be used carefully though), but there is nothing to do in class generation

[Zac Sweers]

hm, yes this is during supertype generation and I do have that resolver available. Would the types I pass into that be the parameter refs and return type ref of the functional type ref then?

[Zac Sweers]

got it working 👍 https://github.com/ZacSweers/metro/pull/202/commits/c62220ce68af7764c086b9fe0d9721d574841ef3