launch is only available since Kotlin 1.3 and cannot be used in Kotlin 1.2

Question

I'm trying to run the simplest example with coroutines:

    import kotlinx.coroutines.*

    fun main() {
        GlobalScope.launch {
            delay(1000L)
            println("${Thread.currentThread().name}: World")
        }
        println("${Thread.currentThread().name}: Hello")
        Thread.sleep(2000L)
        println("${Thread.currentThread().name}: Finish!")
    }

And my build.gradle file looks like this:

buildscript {
    // Consider moving these values to `gradle.properties`
    ext.kotlin_version = '1.3.0-rc-146'
    ext.kotlin_gradle_plugin_version = '1.3.0-rc-198'
    ext.kotlinx_coroutines = '1.0.0-RC1'

    repositories {
        maven { url "https://kotlin.bintray.com/kotlin-eap" }
        mavenCentral()
        jcenter()
        google()
    }
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.51"
    }
}

plugins {
    id 'org.jetbrains.kotlin.jvm' version "1.1.51"
}

apply plugin: 'idea'
apply plugin: 'application'
group 'by.kotlin'
version '1.0-SNAPSHOT'

mainClassName = 'MainKt'

repositories {
    maven { url "https://kotlin.bintray.com/kotlin-eap" }
    mavenCentral()
    jcenter()
    google()
}

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
    implementation "org.jetbrains.kotlin:kotlin-stdlib-common:$kotlin_version"
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$kotlinx_coroutines"   
}

compileKotlin {
    kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
    kotlinOptions.jvmTarget = "1.8"
}

But when I run this example, I've got the following errors:

e: ...Main.kt: (6, 17): 'launch(CoroutineContext = ..., CoroutineStart = ..., [ERROR : Bad suspend function in metadata with constructor: Function2]<CoroutineScope, Continuation<Unit>, Any?>): Job' is only available since Kotlin 1.3 and cannot be used in Kotlin 1.2
e: ...Main.kt: (7, 9): Suspend function 'delay' should be called only from a coroutine or another suspend function
e: ...Main.kt: (7, 9): 'delay(Long): Unit' is only available since Kotlin 1.3 and cannot be used in Kotlin 1.2
> Task :compileKotlin FAILED

Why do these errors occur? I'm completely confused, because the first error says that launch "is only available since Kotlin 1.3 and cannot be used in Kotlin 1.2", but I use Kotlin 1.3 in my build.gradle file (in particular, '1.3.0-rc-146')...

UPD

It seems that the reason of problem is in IntelliJ IDEA Settings:

But how to fix it, if the latest language version, which can be selected there, is 1.2, not 1.3?

Answer 1

Make sure you have updated Kotlin to 1.3. You can do this from Preference->Lanugage & Framework->Kotlin Updates

Then change the version of kotlin.jvm plugin to 1.3.0 in gradle. (https://plugins.gradle.org/plugin/org.jetbrains.kotlin.jvm)

plugins {
    id 'org.jetbrains.kotlin.jvm' version "1.3.0"
}

And for including coroutines

repositories {
    mavenCentral()
}

dependencies {
    compile group: 'org.jetbrains.kotlinx', name: 'kotlinx-coroutines-core', version: '1.0.0'
}

It should be fine now.