How to get the type of an instance of javax.lang.model.element.Element

I'm following Hello World of Annotation Processing in Kotlin and KotlinPoet's documentation and am trying to implement a generic builder for Kotlin. I'd like to generically create a method for every field in an annotated data class and give it's argument the same name and type of the field. The problem is that I cannot find which type the field has, given the instance of javax.lang.model.element.Element that I have. Here's what I managed that far:

fieldsIn(klass.enclosedElements)
            .forEach {
                classBuilder
                        .addProperty(PropertySpec
                                .builder(it.toString(), String::class, KModifier.INTERNAL)
                                .mutable(true)
                                .initializer("\"\"")
                                .build())

                classBuilder
                        .addFunction(FunSpec
                                .builder(it.toString())
                                .addParameter(ParameterSpec
                                        .builder(
                                                it.toString(), 
                                                it.?) // what to use here?
                                        .build())
                                .build())
            }

How can I find the type of the field? I read in the documentation that you should use method asType() but this return an instance of TypeMirror. I can't really see how to continue from here. Any suggestions are welcome.

I ended up using this function:

private fun getClass(it: VariableElement): KClass<*> {
    val type = it.asType()

    return when (type.kind) {
        TypeKind.DECLARED -> Class.forName(type.toString()).kotlin
        TypeKind.BOOLEAN -> Boolean::class
        TypeKind.BYTE -> Byte::class
        TypeKind.SHORT -> Short::class
        TypeKind.INT -> Int::class
        TypeKind.LONG -> Long::class
        TypeKind.CHAR -> Char::class
        TypeKind.FLOAT -> Float::class
        TypeKind.DOUBLE -> Double::class
        else -> throw Exception("Unknown type: $type, kind: ${type.kind}")
    }
}