title: How can I change version of Scala that is used by Play, SBT and its plugins?
body: <p>Is it necessary to change version of Scala that is used by SBT and its plugins ?</p>
  
  <p>I'm using Play Framework 2.1.1-RC2. I want to create new project that will use Scala 2.10.1. To achieve that I did following</p>
  
  <ul>
  <li>added dependency <code>"org.scala-lang" % "scala-compiler" % "2.10.1"</code> in <code>Build.scala</code></li>
  <li>initialized variable <code>scalaVersion</code> to 2.10.1 in <code>Build.scala</code> </li>
  </ul>
  
  <p>Then I ran <code>play about</code> command and got following output</p>
  
  <pre><code>[test2] $ about
  Getting Scala 2.10.1 ...
  downloading http://repo1.maven.org/maven2/org/scala-lang/scala-compiler/2.10.1/scala-compiler-2.10.1.jar ...
          [SUCCESSFUL ] org.scala-lang#scala-compiler;2.10.1!scala-compiler.jar (7401ms)
  downloading http://repo1.maven.org/maven2/org/scala-lang/scala-library/2.10.1/scala-library-2.10.1.jar ...
          [SUCCESSFUL ] org.scala-lang#scala-library;2.10.1!scala-library.jar (4309ms)
  downloading http://repo1.maven.org/maven2/org/scala-lang/scala-reflect/2.10.1/scala-reflect-2.10.1.jar ...
          [SUCCESSFUL ] org.scala-lang#scala-reflect;2.10.1!scala-reflect.jar (2144ms)
  downloading http://repo1.maven.org/maven2/org/scala-lang/jline/2.10.1/jline-2.10.1.jar ...
          [SUCCESSFUL ] org.scala-lang#jline;2.10.1!jline.jar (201ms)
  :: retrieving :: org.scala-sbt#boot-scala
          confs: [default]
          5 artifacts copied, 0 already retrieved (24386kB/58ms)
  [info] This is sbt 0.12.2
  [info] The current project is {file:/C:/work/test_projects/test2/}test2
  [info] The current project is built against Scala 2.10.1
  [info] Available Plugins: play.Project, sbt.PlayProject, com.typesafe.sbteclipse.plugin.EclipsePlugin, com.typesafe.sbtidea.SbtIdeaPlugin
  [info] sbt, sbt plugins, and build definitions are using Scala 2.9.2
  </code></pre>
  
  <p>Last line is what concerns me. It says Scala 2.9.2 is used. How can I change that ? Will it affect what version will be used to compile <strong>my</strong> code ?</p>
  
  <p><strong>Update:</strong> Looks like this way of changing version of compiler didn't work properly. After I run my app I've got following warnings in play console:</p>
  
  <pre><code>[warn] Potentially incompatible versions of dependencies of {file:/C:/work/test_projects/test2/}test2:
  [warn]    org.scala-lang: 2.10.1, 2.10.0
  [info] Compiling 5 Scala sources and 1 Java source to C:\work\test_projects\test2\target\scala-2.10\classes...
  [info] 'compiler-interface' not yet compiled for Scala 2.10.1. Compiling...
  [info]   Compilation completed in 8.608 s
  [warn] Potentially incompatible versions of dependencies of {file:/C:/work/test_projects/test2/}test2:
  [warn]    org.scala-lang: 2.10.1, 2.10.0
  [info] play - Application started (Dev)
  [warn] Potentially incompatible versions of dependencies of {file:/C:/work/test_projects/test2/}test2:
  [warn]    org.scala-lang: 2.10.1, 2.10.0
  </code></pre>