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 use an old version of Kotlin plugin?
This time I helped myself with the following:
Read moreHow do I find my kotlin version?
You can check the Kotlin version in Tools | Kotlin | Configure Kotlin Plugin Updates . If you have projects created with earlier Kotlin versions, change the Kotlin version in your projects and update kotlinx libraries if necessary – check the recommended versions.
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