scala - Scala 2.10.2 隐含的可能错误

Question

我在使用 Scala 隐式解析时遇到了意外的行为，我想知道这个错误是在我的理解中还是在 Scala 编译器中。这是代码：

trait Trait1[A]

implicit def trait1ToList[A](trait1: Trait1[A]): List[A] = ???

trait Trait2[C]

{
  implicit def trait2Implicit[A, C <% List[A]]: Trait2[C] = ???

  // Compiles, as expected.
  implicitly[Trait2[Trait1[Int]]]
}

{
  implicit def trait2Pimp[A, C <% List[A]](int: Int): Trait2[C] = ???

  // Compiles, as expected.
  implicitly[Int => Trait2[Trait1[Int]]]

  // Does not compile, which is unexpected.
  // This is weird, because the fact the previous line compiles
  // implies the implicit conversion is in scope.
  2: Trait2[Trait1[Int]]
}

编译错误是：

[error] /Users/eric/Dropbox/t/2013_q1/billy/src/test/scala/billy/experiments/wideBaseline/testWideBaselineExperiment.scala:56: No implicit view available from Trait1[Int] => List[A].
[error]       2: Trait2[Trait1[Int]]
[error]       ^

Answer 1

是的，这是 scala 编译器中的一个错误，已在 2.11 中修复。