I have Playframework 2 project with Scala (very small one). It uses Scala Anorm library.
I have the code like this:
package models
..
import anorm.SqlPar
First download source code :
1.) Click on this link : http://www.scala-lang.org/download/all.html
2.) Choose any scala version.
3.) Now in the last section 'Other Resources' you can see 'Sources' link. Click on it to download. In my case (https://codeload.github.com/scala/scala/tar.gz/v2.11.7)
Now point to this Source Code from IntelliJ.
1.) Open Project Structure in IntelliJ. Shorcut (Cmd + DownArrow)
2.) Select Global Libraries from the left section.
3.) Then on right side, Under 'Scala Library' section. Click '+' and point to source directory. See the screenshot.