Go to Intellij Preferences -> Build, Execution, Deployment -> Kotlin Compiler . Update Language version and Api version to the one you wish. This should be the accepted answer.
Read moreHow do I change my Kotlin plugin version?
You can follow these instructions to install the preview version of the Kotlin Plugin for IntelliJ IDEA or Android Studio.
Read moreWhat is the Kotlin plugin?
The Kotlin plugin provides language support in IntelliJ IDEA and Android Studio . Getting Started in IntelliJ IDEA. Getting Started in Android Studio. Public Slack. Issue tracker.
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