This happens consistently and it's easy to reproduce. Just import the project in Eclipse and opening the HelloSlick.scala source. I thought that the empty package was taking a part in this problem, but it turns out it isn't (moving all sources in a proper package doesn't make the wrong error reported by the presentation compiler disappear). As usual with this kind of problems, if the compilation unit containing the definition of `DBIO.seq` is opened, then the presentation compiler correctly typecheck the expression and the error is no longer reported. So, I confirm this is 99% (if not 100%) a presentation compiler issue :-)

Furthermore, if you have Build Automatically **disabled**, when opening the HelloSlick.scala you should also see another error (again only reported by the presentation compiler) saying that both the `Suppliers` and `Coffes` types can't be found. This is likely a different issue, but would be great if this could be fixed as well.

This is https://issues.scala-lang.org/browse/SI-7139.

Slick has a type alias in a package object with the same name as a module in the package:


git grep -E '(object|type) DBIO'
slick/src/main/scala/slick/dbio/DBIOAction.scala:object DBIO {
slick/src/main/scala/slick/dbio/package.scala: type DBIO[+R] = DBIOAction[R, NoStream, Effect.All]
slick/src/main/scala/slick/lifted/Aliases.scala: type DBIO[+R] = dbio.DBIO[R]
slick/src/main/scala/slick/lifted/Aliases.scala: type DBIOAction[+R, +S <: dbio.NoStream, -E <: dbio.Effect] = dbio.DBIOAction[R, S, E]

It could workaround this with:

package dbio {
class DBIOModule /*renamed */ extends ... { def seq.... }
}

package object dbio {
type DBIO[..] = ..
val DBIO: DBIOModule = new DBIOModule
}

@16bytes Unfortunately, it looks like this is a known problem, and Jason said he was unable to fix this one. I'm closing this ticket as there is already an existing ticket for it in the upstream project https://issues.scala-lang.org/browse/SI-7139.