F＃upcasting base

Question

当我想将base向上转换为适当的接口类型（即A）时，我得到一个解析错误，这样我就可以在其上调用doA（）。我知道base（http://cs.hubfs.net/topic/None/58670）有点特别，但到目前为止我还没能找到解决这个问题的方法。

有什么建议吗？

type A =
    abstract member doA : unit -> string

type ConcreteA() =
    interface A with
        member this.doA() = "a"

type ExtA() = 
    inherit ConcreteA()


interface A with
    override this.doA() = "ex" // + (base :> A).doA() -> parse error (unexpected symbol ':>' in expression)

((new ExtA()) :> A).doA() // output: ex

工作的C＃等价物：

public interface A
{
    string doA();
}

public class ConcreteA : A {
    public virtual string doA() { return "a"; }
}

public class ExtA : ConcreteA {
    public override string doA() { return "ex" + base.doA(); }
}

new ExtA().doA(); // output: exa

Answer 1

这相当于你的C＃：

type A =
    abstract member doA : unit -> string

type ConcreteA() =
    abstract doA : unit -> string
    default this.doA() = "a"
    interface A with
        member this.doA() = this.doA()

type ExtA() = 
    inherit ConcreteA()
    override this.doA() = "ex" + base.doA()

ExtA().doA() // output: exa

base不能单独使用，仅用于成员访问（因此解析错误）。请参阅Classes on MSDN下的指定继承。