Failed to build Kotlin code but no errors in IDE

I am trying to implement facebook login written in kotlin. The following code works fine:

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import com.facebook.*
import com.facebook.login.LoginResult
import com.facebook.login.LoginManager
import com.facebook.login.widget.LoginButton
import org.json.JSONObject
import java.util.*


class MainActivity : AppCompatActivity() {
    private var callbackManager: CallbackManager? = null

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

        callbackManager = CallbackManager.Factory.create()
        var loginBtn: LoginButton = findViewById(R.id.login_button) as LoginButton
        loginBtn.setReadPermissions(Arrays.asList("public_profile","email","user_photos"))
        loginBtn.registerCallback(callbackManager, object : FacebookCallback<LoginResult> {
            override fun onCancel() {
                TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
            }


            override fun onError(error: FacebookException) {
                print("error" +error.message)
            }

            override fun onSuccess(result: LoginResult) {
                GraphRequest.newMeRequest(result.accessToken, GraphRequest.GraphJSONObjectCallback {
                    obj: JSONObject, response: GraphResponse ->
                    println(obj.toString())
                    println(obj.getString("email"))})
                println("successful" + result.accessToken)
            }
        })
    }



    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        callbackManager!!.onActivityResult(requestCode, resultCode, data)
    }

}

I am trying to implement facebook login written in kotlin. The following code works fine:

package social.social

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import com.facebook.*
import com.facebook.login.LoginResult
import com.facebook.login.LoginManager
import com.facebook.login.widget.LoginButton
import org.json.JSONObject
import java.util.*

class MainActivity : AppCompatActivity() {
private var callbackManager: CallbackManager? = null

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

    callbackManager = CallbackManager.Factory.create()
    var loginBtn: LoginButton = findViewById(R.id.login_button) as LoginButton
    loginBtn.setReadPermissions(Arrays.asList("public_profile","email","user_photos"))
    loginBtn.registerCallback(callbackManager, object : FacebookCallback<LoginResult> {
        override fun onCancel() {
            TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
        }


        override fun onError(error: FacebookException) {
            print("error" +error.message)
        }

        override fun onSuccess(result: LoginResult) {
            GraphRequest.newMeRequest(result.accessToken, GraphRequest.GraphJSONObjectCallback {
                obj: JSONObject, response: GraphResponse ->
                println(obj.toString())
                println(obj.getString("email"))})
            println("successful" + result.accessToken)
        }
    })
}



override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    callbackManager!!.onActivityResult(requestCode, resultCode, data)
}

}
I tried to add parameters to GraphRequest so I needed to store it into a variable like so:

val request: GraphRequest = GraphRequest.newMeRequest(result.accessToken, GraphRequest.GraphJSONObjectCallback {
                    obj: JSONObject, response: GraphResponse ->
                    println(obj.toString())
                    println(obj.getString("email"))})
                request.executeAsync()

but now it fails build and I can’t figure out why

Error:Execution failed for task ':app:compileDebugJavaWithJavac'.

Unable to read class file: 'C:\projects\social\app\build\tmp\kotlin-classes\debug\social\social\MainActivity$onCreate$1$onSuccess$1.class'