I’ve got the same issue as stated by Gryu.
Same Intellij 2018 3.3
I was able to start my project by setting (like stated by Grigoriy)
File->Project Structure->Modules ->> Language level to 8 ( my maven project was set to 1.8 java)
AND
File -> Settings -> Build, Execution, Deployment -> Compiler -> Java Compiler -> 8 also there
I hope it would be useful