title: Gradle Fails to Compile Basic Scala Project
body: <p>I cannot seem to get gradle to properly compile a simple Scala project. The directory looks like:</p>
  
  <pre><code>.
  ├── build.gradle
  └── src
      └── Main.scala
  </code></pre>
  
  <p>The <code>build.gradle</code> is simply:</p>
  
  <pre><code>apply plugin: 'scala'
  
  sourceSets {
      main {
          scala {
              srcDir 'src'
          }
      }
  }
  </code></pre>
  
  <p>It fails with this charming little error:</p>
  
  <pre><code>* Exception is:
  org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':compileScala'.
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:68)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
          at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:34)
          at org.gradle.api.internal.changedetection.CacheLockHandlingTaskExecuter$1.run(CacheLockHandlingTaskExecuter.java:34)
          at org.gradle.internal.Factories$1.create(Factories.java:22)
          at org.gradle.cache.internal.DefaultCacheAccess.longRunningOperation(DefaultCacheAccess.java:179)
          at org.gradle.cache.internal.DefaultCacheAccess.longRunningOperation(DefaultCacheAccess.java:232)
          at org.gradle.cache.internal.DefaultPersistentDirectoryStore.longRunningOperation(DefaultPersistentDirectoryStore.java:138)
          at org.gradle.api.internal.changedetection.DefaultTaskArtifactStateCacheAccess.longRunningOperation(DefaultTaskArtifactStateCacheAccess.java:83)
          at org.gradle.api.internal.changedetection.CacheLockHandlingTaskExecuter.execute(CacheLockHandlingTaskExecuter.java:32)
          at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:55)
          at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:57)
          at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:41)
          at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:51)
          at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:52)
          at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:42)
          at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:247)
          at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.executeTask(DefaultTaskPlanExecutor.java:52)
          at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.processTask(DefaultTaskPlanExecutor.java:38)
          at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:30)
          at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:83)
          at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:29)
          at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
          at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
          at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:67)
          at org.gradle.api.internal.changedetection.TaskCacheLockHandlingBuildExecuter$1.run(TaskCacheLockHandlingBuildExecuter.java:31)
          at org.gradle.internal.Factories$1.create(Factories.java:22)
          at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:124)
          at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:112)
          at org.gradle.cache.internal.DefaultPersistentDirectoryStore.useCache(DefaultPersistentDirectoryStore.java:130)
          at org.gradle.api.internal.changedetection.DefaultTaskArtifactStateCacheAccess.useCache(DefaultTaskArtifactStateCacheAccess.java:79)
          at org.gradle.api.internal.changedetection.TaskCacheLockHandlingBuildExecuter.execute(TaskCacheLockHandlingBuildExecuter.java:29)
          at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
          at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
          at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:67)
          at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
          at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
          at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:54)
          at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:158)
          at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:113)
          at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:81)
          at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:38)
          at org.gradle.launcher.exec.InProcessGradleLauncherActionExecuter.execute(InProcessGradleLauncherActionExecuter.java:39)
          at org.gradle.launcher.exec.InProcessGradleLauncherActionExecuter.execute(InProcessGradleLauncherActionExecuter.java:25)
          at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:50)
          at org.gradle.api.internal.Actions$RunnableActionAdapter.execute(Actions.java:137)
          at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:201)
          at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:174)
          at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:170)
          at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:139)
          at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
          at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
          at org.gradle.launcher.Main.doAction(Main.java:48)
          at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
          at org.gradle.launcher.Main.main(Main.java:39)
          at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:50)
          at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:32)
          at org.gradle.launcher.GradleMain.main(GradleMain.java:26)
  Caused by: java.lang.NullPointerException: Cannot invoke method withInputStream() on null object
          at org.gradle.api.internal.project.AntBuilderDelegate.taskdef(DefaultIsolatedAntBuilder.groovy:136)
          at org.gradle.api.internal.tasks.scala.AntScalaCompiler$_execute_closure1.doCall(AntScalaCompiler.groovy:62)
          at org.gradle.api.internal.ClosureBackedAction.execute(ClosureBackedAction.java:58)
          at org.gradle.util.ConfigureUtil.configure(ConfigureUtil.java:130)
          at org.gradle.util.ConfigureUtil.configure(ConfigureUtil.java:91)
          at org.gradle.util.ConfigureUtil$configure.call(Unknown Source)
          at org.gradle.api.internal.project.DefaultIsolatedAntBuilder.execute(DefaultIsolatedAntBuilder.groovy:112)
          at org.gradle.api.internal.project.IsolatedAntBuilder$execute.call(Unknown Source)
          at org.gradle.api.internal.tasks.scala.AntScalaCompiler.execute(AntScalaCompiler.groovy:61)
          at org.gradle.api.internal.tasks.scala.AntScalaCompiler.execute(AntScalaCompiler.groovy)
          at org.gradle.api.internal.tasks.scala.DefaultScalaJavaJointCompiler.execute(DefaultScalaJavaJointCompiler.java:35)
          at org.gradle.api.internal.tasks.scala.DefaultScalaJavaJointCompiler.execute(DefaultScalaJavaJointCompiler.java:25)
          at org.gradle.api.internal.tasks.scala.DelegatingScalaCompiler.execute(DelegatingScalaCompiler.java:31)
          at org.gradle.api.internal.tasks.scala.DelegatingScalaCompiler.execute(DelegatingScalaCompiler.java:22)
          at org.gradle.api.internal.tasks.compile.IncrementalJavaCompilerSupport.execute(IncrementalJavaCompilerSupport.java:33)
          at org.gradle.api.internal.tasks.compile.IncrementalJavaCompilerSupport.execute(IncrementalJavaCompilerSupport.java:23)
          at org.gradle.api.tasks.scala.ScalaCompile.compile(ScalaCompile.java:131)
          at org.gradle.api.internal.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:216)
          at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:122)
          at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:147)
          at org.gradle.api.tasks.scala.ScalaCompile_Decorated.invokeMethod(Unknown Source)
          at org.gradle.util.ReflectionUtil.invoke(ReflectionUtil.groovy:23)
          at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$4.execute(AnnotationProcessingTaskFactory.java:161)
          at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$4.execute(AnnotationProcessingTaskFactory.java:156)
          at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:472)
          at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:461)
          at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:60)
          ... 57 more
  
  
  BUILD FAILED
  </code></pre>
  
  <p>My <code>gradle --version</code> is:</p>
  
  <pre><code>------------------------------------------------------------
  Gradle 1.3
  ------------------------------------------------------------
  
  Gradle build time: Tuesday, November 20, 2012 11:37:38 AM UTC
  Groovy: 1.8.6
  Ant: Apache Ant(TM) version 1.8.4 compiled on May 22 2012
  Ivy: 2.2.0
  JVM: 1.6.0_24 (Sun Microsystems Inc. 20.0-b12)
  OS: Linux 3.2.0-29-generic amd64
  </code></pre>
  
  <p>What in the world is going wrong?</p>