Pavel Fatin mentioned in http://devnet.jetbrains.net/message/5268071#5268071 "Scala project configuration was redesigned, facets are now obsolete so you may delete them (no additional re-configurations required)."
However, when I load my existing project with Scala facets and try to build it I get:
Information:Note: Some input files use unchecked or unsafe operations.
Information:Note: Recompile with -Xlint:unchecked for details.
Information:Compilation completed with 1 error and 32 warnings
Error:No Scala SDK configured for modules
I could not delete the Facets from the Module Configuration dialog so I removed them from the .iml files by hand. After that I ran File | Invalidate Caches, reopened the project and ran Build | Rebuild Project. The Messages panel still shows the same error as above.
How do I configure a Scala SDK for a module? I don't see it anywhere in the menus or dialogs.