Attempt at expressing form input a little more concisely

formdata.kt

import android.databinding.BindingAdapter
import android.support.design.widget.TextInputEditText
import android.support.design.widget.TextInputLayout

data class FormData<out D, R>(
    val data: D,
    val reason: R?,
    private val _reasonToString: (R?) -> String = { "$it" }
) {
    val isValid = reason != null
    val reasonToString by lazy { _reasonToString(reason) }
}

@BindingAdapter("formData")
fun <D, R> bindTextInputLayoutFormData(textInputLayout: TextInputLayout, formData: FormData<D, R>) {
    textInputLayout.isErrorEnabled = formData.isValid
    textInputLayout.error = formData.reasonToString
}

@BindingAdapter("formData")
fun <R> bindTextInputEditTextFormData(textInputEditText: TextInputEditText, formData: FormData<String, R>) {
    textInputEditText.setText(formData.data)
}
// BindingAdapter <insert view here> -- takes data and applies to whatever

fun Collection<FormData<Any, out Any>>.isFormValid() = all { it.isValid }