Github user tdas commented on the pull request:
https://github.com/apache/spark/pull/783#issuecomment-43161420
Just to explain further, `ControlThrowable`s like `NonLocalReturnControl`
is used by the scala runtime for legit control flow. For example, here is a
example,
```
def foo(l: List[Int]): Int = {
l.foreach { (i) =>
println(i)
return 5
}
return 10
}
```
The `return 5` is supposed to return from the function `foo`. But if you
think how scala compiles this, the foreach function is essentially another anon
class, and simple `return` inside it would only return from the `foreach`
function and not the method `foo`. So what scala does is throw this
`NonLocalReturnControl` throwable, to get out of the foreach function and then
return from the method `foo`. This is the normal control flow and therefore is
expected to occur and should neither be ignored, nor be logged.
@marmbrus I hope I explained this right. He explained this to me and
@aarondav
Example stolen from
http://dev.bizo.com/2010/01/scala-supports-non-local-returns.html
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