A simple implementation of ButterKnife in Kotlin using reflection

MainActivity.kt

package io.aoriani.simplebutterknife

import android.os.Bundle
import android.support.annotation.IdRes
import android.support.v7.app.AppCompatActivity
import android.view.View
import android.widget.Button
import android.widget.TextView
import kotlin.reflect.KMutableProperty1
import kotlin.reflect.full.declaredMemberProperties
import kotlin.reflect.full.findAnnotation
import kotlin.reflect.jvm.isAccessible

@Target(AnnotationTarget.PROPERTY)
@Retention(AnnotationRetention.RUNTIME)
annotation class IdForView(@IdRes val id: Int)

class MainActivity : AppCompatActivity() {

    @IdForView(R.id.textView)
    private lateinit var textView: TextView

    @IdForView(R.id.button)
    private lateinit var button: Button

    private var counter = 0

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        bind(this)

        button.setOnClickListener { textView.text = (++counter).toString() }
    }
}

fun bind(activity: AppCompatActivity) {
    activity::class.declaredMemberProperties.asSequence()
            .filter { it is KMutableProperty1 && it.annotations.any { it is IdForView } }
            .forEach {
                val viewId = it.findAnnotation<IdForView>()?.id!! // It cannot be null due above check
                val view = activity.findViewById<View>(viewId)
                it as KMutableProperty1<AppCompatActivity, View>
                it.isAccessible = true
                it.set(activity, view)
            }
}