Proposed implementation of 'unlift' on Function...

Proposed implementation of 'unlift' on Function1, the inverse function
of PartialFunction#lift. Review by rytz and other interested parties.
References #3825, but not closing until this is further considered.

1 files changed, 25 insertions, 0 deletions

diff --git a/test/files/run/lift-and-unlift.scala b/test/files/run/lift-and-unlift.scala
new file mode 100644
index 0000000000..859ec02f99
--- /dev/null
+++ b/test/files/run/lift-and-unlift.scala
@@ -0,0 +1,25 @@
+object Test {
+  def evens1(x: Int) = if (x % 2 == 0) Some(x) else None
+  def evens2: PartialFunction[Int, Int] = {
+    case x if x % 2 == 0  => x
+  }
+
+  def main(args: Array[String]): Unit = {
+    val f1 = evens1 _
+    val f2 = evens2.lift
+
+    assert(1 to 10 forall (x => f1(x) == f2(x)))
+
+    val f3 = f1.unlift
+    val f4 = f2.unlift
+
+    assert(1 to 10 forall { x =>
+      if (!f3.isDefinedAt(x)) !f4.isDefinedAt(x)
+      else f3(x) == f4(x)
+    })
+
+    assert(f1 eq f3.lift)
+    // Hmm, why is this not true:
+    // assert(f2 eq f4.lift)
+  }
+}