为什么sbt运行时会使用Slick的代码生成器抛出重叠的输出目录？

我试图迁移从播放2.3计算机数据库的例子来自anorm于油滑2.我想用油滑的代码生成器。

这是我的 project/build.scala

import sbt._
import Keys._

object build extends Build {

  lazy val mainProject = Project(
    id = "main",
    base = file("."),
    settings = Defaults.coreDefaultSettings ++ Seq(
      scalaVersion := "2.10.4",
      libraryDependencies ++= List(
        "com.typesafe.slick" %% "slick" % "2.0.2",
        "org.slf4j" % "slf4j-nop" % "1.6.4",
        "com.h2database" % "h2" % "1.3.170"
      ),
      // register manual sbt command
      slick <<= slickCodeGenTask,
      // register automatic code generation on every compile, remove for only manual use
      sourceGenerators in Compile <+= slickCodeGenTask
    )
  )

  // Slick's code generation task
  lazy val slick = TaskKey[Seq[File]]("gen-tables")

  lazy val slickCodeGenTask = (sourceManaged, dependencyClasspath in Compile, runner in Compile, streams) map { (dir, cp, r, s) =>
    // place generated files in sbt's managed sources folder
    val outputDir = (dir / "slick").getPath
    // connection info for a pre-populated throw-away, in-memory db for this demo, which is freshly initialized on every run
    val url = "jdbc:h2:mem:test;INIT=runscript from 'conf/sql/create.sql'"
    val jdbcDriver = "org.h2.Driver"
    val slickDriver = "scala.slick.driver.H2Driver"
    val pkg = "demo"
    toError(r.run("scala.slick.model.codegen.SourceCodeGenerator", cp.files, Array(slickDriver, jdbcDriver, url, outputDir, pkg), s.log))
    val fname = outputDir + "/demo/Tables.scala"
    Seq(file(fname))
  }
}

当我尝试运行我的应用程序时，sbt run出现以下错误：

java.lang.RuntimeException: Overlapping output directories:/home/myuser/computer-database/target:
    ProjectRef(file:/home/myuser/computer-database/,main)
    ProjectRef(file:/home/myuser/computer-database/,root)
    at scala.sys.package$.error(package.scala:27)
    at scala.Predef$.error(Predef.scala:142)
    at sbt.Load$$anonfun$apply$8.apply(Load.scala:140)
    at sbt.Load$$anonfun$apply$8.apply(Load.scala:140)
    at scala.Option.foreach(Option.scala:236)
    at sbt.Load$.apply(Load.scala:140)
    at sbt.Load$.defaultLoad(Load.scala:37)
    at sbt.BuiltinCommands$.doLoadProject(Main.scala:473)
    at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:467)
    at sbt.BuiltinCommands$$anonfun$loadProjectImpl$2.apply(Main.scala:467)
    at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:60)
    at sbt.Command$$anonfun$applyEffect$1$$anonfun$apply$2.apply(Command.scala:60)
    at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:62)
    at sbt.Command$$anonfun$applyEffect$2$$anonfun$apply$3.apply(Command.scala:62)
    at sbt.Command$.process(Command.scala:95)
    at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:100)
    at sbt.MainLoop$$anonfun$1$$anonfun$apply$1.apply(MainLoop.scala:100)
    at sbt.State$$anon$1.process(State.scala:179)
    at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:100)
    at sbt.MainLoop$$anonfun$1.apply(MainLoop.scala:100)
    at sbt.ErrorHandling$.wideConvert(ErrorHandling.scala:18)
    at sbt.MainLoop$.next(MainLoop.scala:100)
    at sbt.MainLoop$.run(MainLoop.scala:93)
    at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:71)
    at sbt.MainLoop$$anonfun$runWithNewLog$1.apply(MainLoop.scala:66)
    at sbt.Using.apply(Using.scala:25)
    at sbt.MainLoop$.runWithNewLog(MainLoop.scala:66)
    at sbt.MainLoop$.runAndClearLast(MainLoop.scala:49)
    at sbt.MainLoop$.runLoggedLoop(MainLoop.scala:33)
    at sbt.MainLoop$.runLogged(MainLoop.scala:25)
    at sbt.StandardMain$.runManaged(Main.scala:57)
    at sbt.xMain.run(Main.scala:29)
    at xsbt.boot.Launch$$anonfun$run$1.apply(Launch.scala:109)
    at xsbt.boot.Launch$.withContextLoader(Launch.scala:129)
    at xsbt.boot.Launch$.run(Launch.scala:109)
    at xsbt.boot.Launch$$anonfun$apply$1.apply(Launch.scala:36)
    at xsbt.boot.Launch$.launch(Launch.scala:117)
    at xsbt.boot.Launch$.apply(Launch.scala:19)
    at xsbt.boot.Boot$.runImpl(Boot.scala:44)
    at xsbt.boot.Boot$.main(Boot.scala:20)
    at xsbt.boot.Boot.main(Boot.scala)
[error] Overlapping output directories:/home/myuser/computer-database/target:
[error]     ProjectRef(file:/home/myuser/computer-database/,main)
[error]     ProjectRef(file:/home/myuser/computer-database/,root)
[error] Use 'last' for the full log.

如果我更改id = "main"为id = "root"上一个错误，则不会再触发该错误，而是会触发一个新错误：

java.lang.RuntimeException: No main class detected.
    at scala.sys.package$.error(package.scala:27)
[trace] Stack trace suppressed: run last compile:run for the full output.
[error] (compile:run) No main class detected.
[error] Total time: 1 s, completed 08-Jun-2014 20:22:41

Project ID（无论是什么）似乎都存在问题。我在这里想念什么？