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regression: return is treated as a break in a breakable code #5612

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scabug opened this issue Mar 26, 2012 · 8 comments
Closed

regression: return is treated as a break in a breakable code #5612

scabug opened this issue Mar 26, 2012 · 8 comments
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@scabug scabug commented Mar 26, 2012

Reported by Richard Emberson on scala-user, minimized:

object L extends Enumeration {
  val One, Two, Three = Value
}

class Foo {
  def foo(xs: List[L.Value]) {
    import scala.util.control.Breaks.{break, breakable}
    println("START for " + xs)
    breakable {
      for (x <- xs) {
        x match {
          case L.One => println("ONE"); return
          case L.Two => println("TWO")
          case L.Three => println("THREE"); break
        }
      }
    }
    println("FINISH")
  }
}

object Test {
  def main(args: Array[String]) {
    val f = new Foo()
    val l = List(L.Two, L.Two, L.One, L.Three)
    f.foo(l)
  }
}

in 2.10.0-M2:

START for List(Two, Two, One, Three)
TWO
TWO
ONE

in latest nightly (a532ba):
compiles with warning:

warning: non variable type-argument Unit in type pattern scala.runtime.NonLocalReturnControl[Unit] is unchecked since it is eliminated by erasure

output:

START for List(Two, Two, One, Three)
TWO
TWO
ONE
FINISH
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@scabug scabug commented Mar 26, 2012

Imported From: https://issues.scala-lang.org/browse/SI-5612?orig=1
Reporter: @hubertp
Affected Versions: 2.10.0-M2

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@scabug scabug commented Mar 26, 2012

@hubertp said:
It seems to be caused by this catch block generated during uncurry for NonLocalReturnControl.
The old code:

} catch {
  case (ex @ (_: scala.runtime.NonLocalReturnControl[Foo.this._])) => if (ex.key().eq(nonLocalReturnKey1))
    ex.value().asInstanceOf[Unit]()
  else
    throw ex
}

vs the new one:

} catch {
  case (ex @ (_: scala.runtime.NonLocalReturnControl[Unit])) => if (ex.key().eq(nonLocalReturnKey1))
    ex.value()
  else
    throw ex
}
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@scabug scabug commented Mar 26, 2012

@paulp said:
I already tracked this down and reverted the commit which caused it, but that broke the build and the revert was unreverted.

See 5af2bf54d2 and 3db29dde05 .

The commit which caused it is 19a48510c .

The "non-variable type argument" spurious warning is unrelated.

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@scabug scabug commented Mar 27, 2012

@hubertp said:
Ah, the infamous revert of the revert. Thanks for the info.

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@scabug scabug commented Apr 30, 2012

Richard Emberson (rmemberson) said:
Wow, I guess I am really surprised that 2.10.0-M3 would be
released without first fixing this show-stopper.
I'd like to incorporate some of the new features being
highlighted in the 2.10.0-M3 but can not because a couple
of my libraries have failed to compile for over a month
due to the "fix" 19a48510c.
I kept waiting for this to be addressed so that I could
go back to using the git-head rather than 2.10.0-M2.

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@scabug scabug commented Apr 30, 2012

@SethTisue said:
I don't really know what a "milestone" is or should be, but I would agree that nothing with this bug should be called a release candidate.

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@scabug scabug commented Apr 30, 2012

@paulp said:
In principle milestones are time-based and indifferent to the presence or absence of any particular fix; the only milestone-specific effort is to endeavor to make sure it works with sbt, the ide, etc.

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@scabug scabug commented May 4, 2012

@paulp said:
aad6deae72

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