build.gradle

apply plugin: 'java'

task allowed(type: MyTask){
  obj = configurations.compile
  obj configurations.compile
  cfg = configurations.compile
}

task broken(type: MyTask){
  cfg configurations.compile
}

class MyTask extends DefaultTask {
  Object obj
  Configuration cfg

  @TaskAction
  def act(){ 
    println "${name}.obj :: ${obj}" 
    println "${name}.cfg :: ${cfg}" 
  }
}

output.txt

/tmp/gradle_test⚡ gradle --stacktrace

FAILURE: Build failed with an exception.

* Where:
Build file '/tmp/gradle_test/build.gradle' line: 10

* What went wrong:
A problem occurred evaluating root project 'gradle_test'.
> Could not find method cfg() for arguments [configuration ':compile'] on root project 'gradle_test'.

* Try:
Run with --info or --debug option to get more log output.

* Exception is:
org.gradle.api.GradleScriptException: A problem occurred evaluating root project 'gradle_test'.
	at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:54)
	at org.gradle.configuration.DefaultScriptPluginFactory$ScriptPluginImpl.apply(DefaultScriptPluginFactory.java:148)
	at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:39)
	at org.gradle.configuration.project.BuildScriptProcessor.execute(BuildScriptProcessor.java:26)
	at org.gradle.configuration.project.ConfigureActionsProjectEvaluator.evaluate(ConfigureActionsProjectEvaluator.java:34)
	at org.gradle.configuration.project.LifecycleProjectEvaluator.evaluate(LifecycleProjectEvaluator.java:59)
	at org.gradle.api.internal.project.AbstractProject.evaluate(AbstractProject.java:504)
	at org.gradle.api.internal.project.AbstractProject.evaluate(AbstractProject.java:83)
	at org.gradle.execution.TaskPathProjectEvaluator.configureHierarchy(TaskPathProjectEvaluator.java:42)
	at org.gradle.configuration.DefaultBuildConfigurer.configure(DefaultBuildConfigurer.java:35)
	at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:129)
	at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:106)
	at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:86)
	at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:80)
	at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:33)
	at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:24)
	at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:36)
	at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:26)
	at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:51)
	at org.gradle.internal.Actions$RunnableActionAdapter.execute(Actions.java:171)
	at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:237)
	at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:210)
	at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:35)
	at org.gradle.launcher.cli.JavaRuntimeValidationAction.execute(JavaRuntimeValidationAction.java:24)
	at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:206)
	at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:169)
	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:33)
	at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
	at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:54)
	at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:35)
	at org.gradle.launcher.GradleMain.main(GradleMain.java:23)
Caused by: org.gradle.api.internal.MissingMethodException: Could not find method cfg() for arguments [configuration ':compile'] on root project 'gradle_test'.
	at org.gradle.api.internal.AbstractDynamicObject.methodMissingException(AbstractDynamicObject.java:68)
	at org.gradle.api.internal.AbstractDynamicObject.invokeMethod(AbstractDynamicObject.java:56)
	at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:172)
	at org.gradle.groovy.scripts.BasicScript.methodMissing(BasicScript.java:79)
	at build_xrr6xq23mr4l2649yr2pehyl$_run_closure2.doCall(/private/tmp/gradle_test/build.gradle:10)
	at org.gradle.api.internal.ClosureBackedAction.execute(ClosureBackedAction.java:63)
	at org.gradle.util.ConfigureUtil.configure(ConfigureUtil.java:130)
	at org.gradle.util.ConfigureUtil.configure(ConfigureUtil.java:110)
	at org.gradle.api.internal.AbstractTask.configure(AbstractTask.java:482)
	at org.gradle.api.internal.project.AbstractProject.task(AbstractProject.java:879)
	at org.gradle.api.internal.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:225)
	at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:129)
	at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:147)
	at org.gradle.groovy.scripts.BasicScript.methodMissing(BasicScript.java:79)
	at build_xrr6xq23mr4l2649yr2pehyl.run(/private/tmp/gradle_test/build.gradle:9)
	at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:52)
	... 32 more