Why is Scala's type inferencer not able to resolve this?
- by Levi Greenspan
In the code snippet below - why do I have to give a type annotation for Nil?
Welcome to Scala version 2.8.0.RC2 (OpenJDK Server VM, Java 1.6.0_18).
Type in expressions to have them evaluated.
Type :help for more information.
scala> List(Some(1), Some(2), Some(3), None).foldLeft(Nil)((lst, o) => o match { case Some(i) => i::lst; case None => lst })
<console>:6: error: type mismatch;
found : List[Int]
required: object Nil
List(Some(1), Some(2), Some(3), None).foldLeft(Nil)((lst, o) => o match { case Some(i) => i::lst; case None => lst })
^
scala> List(Some(1), Some(2), Some(3), None).foldLeft(Nil:List[Int])((lst, o) => o match { case Some(i) => i::lst; case None => lst })
res1: List[Int] = List(3, 2, 1)
