SBT/Scala: macro implementation not found - scala

Question

I tried my hand on macros, and I keep running into the error
macro implementation not found: W
[error] (the most common reason for that is that you cannot use macro implementations in the same compilation run that defines them)
I believe I've set up a two pass compilation with the macro implementation being compiled first, and the usage second.
Here is part of the /build.sbt:
lazy val root = (project in file(".")).
settings(rootSettings: _*).
settings(name := "Example").
aggregate(macros, core).
dependsOn(macros, core)
lazy val macros = (project in file("src/main/com/example/macros")).
settings(macrosSettings: _*).
settings(name := "Macros")
lazy val core = (project in file("src/main/com/example/core")).
settings(coreSettings: _*).
settings (name := "Core").
dependsOn(macros)
lazy val commonSettings = Seq(
organization := Organization,
version := Version,
scalaVersion := ScalaVersion
)
lazy val rootSettings = commonSettings ++ Seq(
libraryDependencies ++= commonDeps ++ rootDeps ++ macrosDeps ++ coreDeps
)
lazy val macrosSettings = commonSettings ++ Seq(
libraryDependencies ++= commonDeps ++ macrosDeps
)
lazy val coreSettings = commonSettings ++ Seq(
libraryDependencies ++= commonDeps ++ coreDeps
)
The macro implementation looks like this:
/src/main/com/example/macros/Macros.scala
object Macros {
object Color {
def ColorWhite(c: Context): c.Expr[ObjectColor] = c.Expr[ObjectColor](c.universe.reify(ObjectColor(White())).tree)
}
}
The usage looks like this:
/src/main/com/example/core/Main.scala
object Macros {
import com.example.macros.Macros._
def W: ObjectColor = macro Color.ColorWhite
}
object Main extends App {
import Macros._
println(W)
}
Scala 2.11.6. SBT 0.13.8.
What am I doing wrong?
Thanks for your advice!
Fawlty Project:
The Project on Github
Working Project:
Rearranged the projects to a more correct form:
The cleanedup working project

Answer 1

Your macros and core projects don't contain any files, so they don't cause the problem. The error happens when sbt compiles root, which contains both Main.scala and Macros.scala by the virtue of you saying project in file(".") in the sbt build.