It is not recommended to use procedure-like syntax for methods. It is inconsistent, may lead to errors and will be deprecated in future versions of Scala.

* Reference: The talk "Scala with Style" by Martin Odersky at ScalaDays 2013

Hint: You can use Analyze / Run Inspection by Name (Ctrl+Alt+Shift+I) to apply this inspection to the whole project

Before:

class Impl {
  def method() {
    // ...
  }
}

After:
class Impl {
  def method(): Unit = {
    // ...
  }
}