title: sbt, intellij jar in external library but not found when compile
body: <p>encounter a very strange problem.
  I'm trying to use reactivemongo. And after update build.sbt
  I can see that the jar is in the external library. However the compilation failed because not found object reactivemongo.
  <a href="https://i.stack.imgur.com/wHV57.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/wHV57.png" alt="enter image description here"></a></p>
  
  <p>my build.sbt is:</p>
  
  <p><code>here</code>enter code here<code>lazy val commonSettings = Seq(</code>
    <code>here</code>organization := "emmettng.com",<code>
  </code> here<code>version := "0.0.1",</code>
    <code>scalaVersion := "2.11.8"</code>
  <code>)</code></p>
  
  <p><code>here</code>resolvers += "Typesafe Repo" at<code></code>"<a href="http://repo.typesafe.com/typesafe/releases/" rel="nofollow noreferrer">http://repo.typesafe.com/typesafe/releases/</a>"<code>
  </code>resolvers += "Typesafe repository releases" at<code></code>"<a href="http://repo.typesafe.com/typesafe/releases/" rel="nofollow noreferrer">http://repo.typesafe.com/typesafe/releases/</a>"`</p>
  
  <p><code>libraryDependencies ++= Seq(</code>
    <code>"org.scala-lang" % "scala-reflect" % "2.11.8",</code>
    <code>"org.scala-lang.modules" % "scala-xml_2.11" % "1.0.4",</code>
    ``"org.scalatest" %% "scalatest" % "3.0.0" % "test",<code>
    "com.typesafe.play" %% "play-json" % "2.4.0-M3",</code>
    "org.scalaz" %% "scalaz-core" % "7.2.5",<code>
    "junit" % "junit" % "4.10" % "test",</code>
    "org.reactivemongo" %% "reactivemongo" % "0.11.14"<code>
  )</code></p>