Question

我经常使用详细语法来创建通常为几行的单行表达式。通常我这样做，所以我可以使用Alt+'将整个表达式发送到F＃interactive。例如，我可能会这样做：

let longLength list = let rec helper result = function [] -> result | _ :: t -> helper (result + 1L) t in helper 0L list

对于示例代码，假设已打开这些名称空间：

open System
open System.Collections
open System.Collections.Generic

我想将此对象表达式转换为单行：

let emptyEnumerator = {
    new IEnumerator<int> with member t.Current = raise(InvalidOperationException())
    interface IEnumerator with
        member t.MoveNext() = false
        member t.Reset() = ()
        member t.Current = raise(InvalidOperationException())
    interface IDisposable with member t.Dispose() = ()
    }

我发现我只能使用详细语法来完成它。通常，详细语法代码也会在轻量级语法下编译，但在这里，它不会。我也尝试使用相同的实现创建一个命名类，并且几乎相同的代码在轻量级和详细语法下编译：

open System
open System.Collections
open System.Collections.Generic

#light "off"
type A() = class interface IEnumerator<int> with member t.Current = raise(InvalidOperationException()) end interface IEnumerator with member t.MoveNext() = false member t.Reset() = () member t.Current = raise(InvalidOperationException()) end interface IDisposable with member t.Dispose() = () end end
let b = { new IEnumerator<int> with member t.Current = raise(InvalidOperationException()) end interface IEnumerator with member t.MoveNext() = false member t.Reset() = () member t.Current = raise(InvalidOperationException()) end interface IDisposable with member t.Dispose() = () end end }

#light "on"
type C() = class interface IEnumerator<int> with member t.Current = raise(InvalidOperationException()) end interface IEnumerator with member t.MoveNext() = false member t.Reset() = () member t.Current = raise(InvalidOperationException()) end interface IDisposable with member t.Dispose() = () end end
let d = { new IEnumerator<int> with member t.Current = raise(InvalidOperationException()) end interface IEnumerator with member t.MoveNext() = false member t.Reset() = () member t.Current = raise(InvalidOperationException()) end interface IDisposable with member t.Dispose() = () end end }

两个类定义都成功，但最后一行失败，带有“~vsB756.fsx（29,150）：错误FS0010：表达式中的意外关键字'member'。在此点或其他标记之前或之前的预期不完整结构化构造。”

问题似乎出现在一系列成员定义中。 Visual Studio突出显示定义member部分中的第二个和第三个IEnumerator关键字，作为FS0010错误的原因。（换句话说，突出显示的member关键字是引入IEnumerator.Reset()和IEnumerator.Current定义的关键字。）

Visual Studio还会在end实现之前的开放式大括号（不匹配的“{”）和IDisposable关键字上报告“let”（不完整的值或函数定义）上的错误，但是我怀疑这是因为它未能识别IEnumerator实现中的三个成员，这导致它尝试解析其他成员作为第一个成员定义的一部分。

我是否忽略了语法中的某些内容？这是编译器中的错误吗？

对象表达式，接口实现，详细语法

0 个答案: