For JDK 10 you will need Gradle 4.7+ which is not used by default in IntelliJ IDEA (current version IntelliJ IDEA 2018.1.4).
To fix this issue install latest Gradle for your OS (Install guide). For MacOS you can use Homebrew:
brew install gradle
Go to your project directory:
cd ~/path/to/your/project/
Generate Gradle Wrapper script with the version you installed (in my case it is 4.8):
gradle wrapper --gradle-version 4.8
This command is going to download Gradle 4.8, create scripts gradlew and gradlew.bat for your current project. From this point, you should use these scripts in the command-line.
Next step, is to make sure that IntelliJ IDEA uses those, instead of built-in Gradle distribution and you can do this by opening IntelliJ preferences and search for “gradle” (this will be in “Build, Execution, Deployment / Build Tools / Gradle”).
In this section of the settings select:
Select “Use gradle ‘wrapper’ task configuration”
Apply changes, press ok and re-build (re-sync) Gradle and everything should be fine. I hope this helps.