Gradle vs Devkit

There are two ways to create a plugin project. Gradle is the preferred way and this is what I chose.

But in this way if I try to follow this tutorial:http://www.jetbrains.org/intellij/sdk/docs/tutorials/custom_language_support/folding_builder.html

The IDE can't find PsiLiteralExpression and the class doesn't compile. What did I miss?