Demo.kt

package com.cornershopapp.shopper.android.ui

import androidx.lifecycle.ViewModel
import androidx.lifecycle.viewModelScope
import kotlinx.coroutines.*

class Demo : ViewModel() {

    fun login(name: String, pass: String
    ) = viewModelScope.launch {
        val result = requestLogin(name, pass)
        show(result)
    }

    private suspend fun requestLogin(
            name: String, pass: String
    ): Either<Throwable, Boolean> = withContext(Dispatchers.IO) {
        if (name.isNotBlank() && pass.isNotBlank()) {
            return@withContext Either.Right(true)
        } else {
            return@withContext Either.Left(IllegalStateException("Invalid"))
        }
    }

    fun show(result: Either<Throwable, Boolean>) {
        // ...
    }
}

sealed class Either<out A, out B> {
    class Left<A>(val value: A) : Either<A, Nothing>()
    class Right<B>(val value: B) : Either<Nothing, B>()
}