title: at scala project, compiler error - Cannot resolve symbol List?
body: <p>I'm completely newly at Scala.<br>
  I installed java, sbt and scala on Ubuntu 12.04:</p>
  
  <pre><code>nazar_art@nazar-desctop:~$ sbt sbt-version
  [warn] Alternative project directory .sbt (/home/nazar_art/.sbt) has been deprecated since sbt 0.12.0.
  [warn]   Please use the standard location: /home/nazar_art/project
  [info] Loading project definition from /home/nazar_art/.sbt
  [info] Set current project to default-5b9232 (in build file:/home/nazar_art/)
  [info] 0.12.4
  nazar_art@nazar-desctop:~$ scala -version
  Scala code runner version 2.10.2 -- Copyright 2002-2013, LAMP/EPFL
  nazar_art@nazar-desctop:~$ java -version
  java version "1.7.0_40"
  Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
  Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode)
  </code></pre>
  
  <p>I installed scala and sbt plugins to Idea.</p>
  
  <p>And when I tried irst example project I see next error:</p>
  
  <p>Cannot resolve symbol List, after next lines:</p>
  
  <pre><code>package example    
  import common._
  
  object Lists {      
    def sum(xs: List[Int]): Int = {   // &lt;== here underline for List
      if (xs.isEmpty) 0
      else xs.head + sumList(xs.tail)
    }    
  }
  </code></pre>
  
  <p>I couldn't figure out what exactly is wrong?
  IDEA suggest me importing <code>java.util.List</code> - but this class doesn't have any <code>isEmpthy()</code> method.<br>
  Any suggestion?</p>
  
  <ul>
  <li><strong><em>How to solve this trouble?</em></strong></li>
  </ul>
  
  <p><strong>Update:</strong></p>
  
  <ul>
  <li>I reinstalled newly version of <a href="http://confluence.jetbrains.com/display/IDEADEV/IDEA+13+EAP" rel="noreferrer">IntelliJ IDEA 13 Community
  Edition</a>
  instead of # 12. Untared in <code>/usr/local/Idea</code>.</li>
  <li>Removed sbt - <code>sudo apt-get purge sbt</code>. And reinstall accord <a href="https://github.com/paulp/sbt-extras" rel="noreferrer">this
  script</a>.</li>
  <li><p>I went to <code>/MyProjectDirectory/project/</code> and created 'plugin.sbt'
  with content:</p>
  
  <p><code>addSbtPlugin("com.github.mpeltonen" % "sbt-idea" % "1.5.1")</code></p></li>
  <li><p>After this I type from my project directory <code>sbt gen-idea</code>.   It
  rebuild project for Idea.</p></li>
  <li>And opened this project with idea greeting window (Open Paroject). Of course,
  installed <code>sbt</code> and <code>scala</code> plugins.</li>
  </ul>
  
  <p>It should be enough but it shown again:</p>
  
  <pre><code>Cannot resolve symbol List
  </code></pre>
  
  <p>and suggesting import <code>import scala.collection.immutable.List</code>. But this isn't helpful. It keep being underlined with red line.
  <img src="https://i.stack.imgur.com/BSP95.png" alt="enter image description here"></p>