Normally automatic restart is triggered when you saved a file.
However ,because IntelliJ IDEA does this automatically , you will expect that restart is triggered too.
Well, bad news is .. it doesn't work that way in IntelliJ IDEA. Good news in order to trigger restart you need press Ctrl + F9 (on Windows and Linux ) ,if you have allergy to shortcuts simply go to menu and select Build and then press Make Project.
Enjoy your lighting fast development!