scala - 2 不同类中具有相同名称的扩展方法在 Scala 3 中不起作用？

Question

我有以下场景:

case class B(v: String)
case class A(bs: Seq[B])

extension(a: A)
  def doit() = a.bs.map(_.doit()) // here is the exception

extension(b: B)
  def doit() = println("OK: ${b.v}")

这给了我以下编译异常:

value doit is not a member of B.
An extension method was tried, but could not be fully constructed:

    _$1

有吗 限制在 中的扩展方法的命名中斯卡拉 3 ?
请参阅此处的示例 Scastie

Answer 1

把评论变成答案，spec说两个扩展都被翻译成 def extension_doit .
显式调用扩展方法:

-- [E044] Cyclic Error: so.scala:7:45 -----------------------
7 |  extension(a: A) def doit() = a.bs.map(b => extension_doit(b)())
  |                                             ^
  |           Overloaded or recursive method extension_doit needs return type

这与调试原始示例时看到的错误相同:

>>>> StoredError: Overloaded or recursive method extension_doit needs return type
[snip]
-- [E008] Not Found Error: so.scala:7:42 --------------------
7 |  extension(a: A) def doit() = a.bs.map(_.doit())
  |                                        ^^^^^^
  |        value doit is not a member of B.
  |        An extension method was tried, but could not be fully constructed:
  |
  |            _$1

Overload resolution已明确改进或扩展以处理这种可能仅在以后的参数列表中区分的正常情况的重载。显然，我们应该意识到脱糖形式已重载。
Scala 2 也提示:

scala> object X { def f(i: Int) = f("") ; def f(s: String) = f(42) }
                                                              ^
       error: overloaded method f needs result type
                                   ^
       error: overloaded method f needs result type