Reports instance main methods that are declared inside nested classes.

The invocation of main method within nested classes is not handled directly by Groovy; however, it is possible by delegating the execution to Java. In such a scenario, the code will be executed successfully only if the Java version is enough. Consider the following example:

class Outer {
  static class Nested {
    void main() {
      println 'Hello from nested'
    }
  }
}