match may not be exhaustive
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Koen Daenen
Apr 29, 2014, 7:37:47 AM4/29/14
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Below 2 very similar classes, F1 and F2
You expect F1 to behave the same as F2[Int], which it does.
The output of Test results in:
A:1
B
C
A:1
B
C
My question/remark is related to the warning of the 2.10 compiler: no warning in F1 but in F2 at "t match { ... }", I got "match may not be exhaustive. It would fail on the following input: C"
Am I missing a detail or is the warning wrong here?
package test
class F1() {
private sealed abstract class T
private case class A(m: Int) extends T
private case class B() extends T
private case object C extends T
// No warnings here
private def foo(t: T) = t match {
case A(m) => println("A:" + m)
case B() => println("B")
case C => println("C")
}
def test(m: Int): Unit = {
foo(A(m))
foo(B())
foo(C)
}
}
class F2[M]() {
private sealed abstract class T
private case class A(m: M) extends T
private case class B() extends T
private case object C extends T
// match may not be exhaustive. It would fail on the following input: C
private def foo(t: T) = t match {
case A(m) => println("A:" + m)
case B() => println("B")
case C => println("C")
}
def test(m: M): Unit = {
foo(A(m))
foo(B())
foo(C)
}
}
object Test {
def main(args: Array[String]): Unit = {
new F1().test(1)
new F2[Int]().test(1)
}
}
You expect F1 to behave the same as F2[Int], which it does.
The output of Test results in:
A:1
B
C
A:1
B
C
My question/remark is related to the warning of the 2.10 compiler: no warning in F1 but in F2 at "t match { ... }", I got "match may not be exhaustive. It would fail on the following input: C"
Am I missing a detail or is the warning wrong here?
package test
class F1() {
private sealed abstract class T
private case class A(m: Int) extends T
private case class B() extends T
private case object C extends T
// No warnings here
private def foo(t: T) = t match {
case A(m) => println("A:" + m)
case B() => println("B")
case C => println("C")
}
def test(m: Int): Unit = {
foo(A(m))
foo(B())
foo(C)
}
}
class F2[M]() {
private sealed abstract class T
private case class A(m: M) extends T
private case class B() extends T
private case object C extends T
// match may not be exhaustive. It would fail on the following input: C
private def foo(t: T) = t match {
case A(m) => println("A:" + m)
case B() => println("B")
case C => println("C")
}
def test(m: M): Unit = {
foo(A(m))
foo(B())
foo(C)
}
}
object Test {
def main(args: Array[String]): Unit = {
new F1().test(1)
new F2[Int]().test(1)
}
}
Som Snytt
Apr 29, 2014, 7:57:02 AM4/29/14
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On 2.11, the warning goes away if you use:
case _: C.type => println("C")
case _: C.type => println("C")
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Jason Zaugg
Apr 29, 2014, 8:21:13 AM4/29/14
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On Tue, Apr 29, 2014 at 1:37 PM, Koen Daenen <koen.daenen.al...@gmail.com> wrote:
Below 2 very similar classes, F1 and F2
You expect F1 to behave the same as F2[Int], which it does.
The output of Test results in:
A:1
B
C
A:1
B
C
My question/remark is related to the warning of the 2.10 compiler: no warning in F1 but in F2 at "t match { ... }", I got "match may not be exhaustive. It would fail on the following input: C"
Am I missing a detail or is the warning wrong here?
The warning is wrong. I've pinpointed the spot where it regressed in the lead up to 2.10.2, and lodged a bug:
Thank you for reporting!
-jason
Koen Daenen
Apr 30, 2014, 2:12:47 AM4/30/14
to scala-l...@googlegroups.com
The warning is wrong. I've pinpointed the spot where it regressed in the lead up to 2.10.2, and lodged a bug:Thank you for reporting!-jason
Thanks for correlating it to the bug reporting.
Some extra info: I ran my test in the Eclipse bundle http://scala-ide.org/download/sdk.html, which I downloaded recently. I came with scala 2.10.4
On 2.11, the warning goes away if you use:
case _: C.type => println("C")
I tried this as well in 2.10.4; the warning stays.
Koen
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