Github user willb commented on the pull request:
https://github.com/apache/spark/pull/717#issuecomment-43000971
@rxin, the latest commit adds such a test.
I'll note that the code I have only finds toplevel `return` statements, so
it won't spuriously reject code like that example, but it also won't reject
code like this, which is an invalid use of `return`:
```scala
nums.map {x =>
// this return is invalid since it will transfer control outside the
closure
val foo = {y: Int => return 2; 1 }
foo(x)
}
```
I thought identifying toplevel `return` statements in closures represented
an acceptable tradeoff between complexity and user-friendliness in order to
provide better feedback in the common case (but not necessarily to exhaustively
flag all bogus closures, no matter how pathological). If this isn't the right
tradeoff, I could adapt the code to reject a higher percentage of closures with
nonlocal returns.
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