CodeGeneration.kt

    // continued from above
    if (summables.isEmpty()) {
        return
    }

    val fileSpec = FileSpec.builder(
        packageName = packageName,
        fileName = classDeclaration.simpleName.asString() + "Ext"
    ).apply {
        addFunction(
            FunSpec.builder("sumInts")
                .receiver(ksType.toTypeName(TypeParameterResolver.EMPTY))
                .returns(Int::class)
                .addStatement("val sum = %L", summables.joinToString(" + "))
                .addStatement("return sum")
                .build()
        )
    }.build()

    fileSpec.writeTo(codeGenerator = codeGenerator, aggregating = false)
}