title: Why does Kotlin byte code reference java.util.function.BiConsumer?
body: <p>From what I understand Kotlin should be able to run using JRE 6.  But this code with a <code>foreach</code> on a map fails because of a reference to a Java 8 class (<code>java/util/function/BiConsumer</code>)</p>
  
  <p>CompilerTest.kt:</p>
  
  <pre><code>fun main(args: Array&lt;String&gt;) {
    val aMap = mapOf("bar" to "bat")
    aMap.forEach { k, v -&gt; println("$k -&gt; $v")}
  }
  </code></pre>
  
  <p>Compile the Kotlin code:</p>
  
  <pre><code>» kotlinc CompilerTest.kt -jvm-target 1.6 -include-runtime -d compilerTest.jar
  </code></pre>
  
  <p>Testing the compiled code on JRE 6:</p>
  
  <pre><code>» docker run --rm -v "$PWD":/usr/src/myapp -w /usr/src/myapp openjdk:6-jdk-slim java -jar compilerTest.jar
  Exception in thread "main" java.lang.NoClassDefFoundError: java/util/function/BiConsumer
      at java.lang.ClassLoader.defineClass1(Native Method)
      at java.lang.ClassLoader.defineClass(ClassLoader.java:643)
      at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
      at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
      at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
      at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
      at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
      at CompilerTestKt.main(CompilerTest.kt:5)
  Caused by: java.lang.ClassNotFoundException: java.util.function.BiConsumer
      at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
      at java.security.AccessController.doPrivileged(Native Method)
      at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
      at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
      ... 12 more
  </code></pre>
  
  <p>Version Information:</p>
  
  <pre><code>» kotlinc -version         
  info: kotlinc-jvm 1.1.4-3 (JRE 1.8.0_131-b11)
  </code></pre>