F#：如何将 Dotnet 对象的方法的特定重载作为第一类对象访问

Question

我可以做到（F# FSI）：

let o = Object()
let m = o.GetHashCode;; //[1]
val o : Object
val m : (unit -> int)

这使得方法 GetHashCode 可以作为绑定 m 的一流函数访问和调用：

m ();;
val it : int = 12345678

如果有问题的方法存在重载，我将如何执行此操作，比如额外的Object.GetHashCode(int whateverParameter)？我现在只能得到“第一个”（最短的？）方法。我可以在调用1 中提供额外的参数类型信息来指定我想要的重载吗？

编辑

感谢您迄今为止的意见。类型注释似乎是要走的路。尽管如此，对于我更复杂的示例，我仍然无法弄清楚如何正确地做到这一点。

这是我正在处理的类型的具体方法签名（它来自 octokit.net 库，因此您的 fsi 中需要类似 #r "nuget:include=Octokit" 的东西 [with /langversion:preview]）。

我有兴趣检索GetAllForRepository 的特定重载，顺便提一下，列出的第一个：GetAllForRepository(string, string)。

open Octokit
let client = GitHubClient(...)
client.Issue.GetType().GetMethods()
|> Seq.filter (fun methodInfo -> methodInfo.Name.StartsWith("GetAllForRepository"))
|> Seq.map (fun methodInfo -> (methodInfo.GetParameters(), methodInfo.ReturnType))
|> Seq.map (fun (parameterInfos, returnType) ->
    (parameterInfos |> Seq.map (fun parameterInfo -> parameterInfo.ParameterType.FullName), returnType.FullName))

val it : seq<seq<string> * string> =
  seq
    [(seq ["System.String"; "System.String"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq ["System.Int64"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq ["System.String"; "System.String"; "Octokit.ApiOptions"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq ["System.Int64"; "Octokit.ApiOptions"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq ["System.String"; "System.String"; "Octokit.RepositoryIssueRequest"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq ["System.Int64"; "Octokit.RepositoryIssueRequest"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq
        ["System.String"; "System.String"; "Octokit.RepositoryIssueRequest";
         "Octokit.ApiOptions"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]");
     (seq
        ["System.Int64"; "Octokit.RepositoryIssueRequest";
         "Octokit.ApiOptions"],
      "System.Threading.Tasks.Task`1[[System.Collections.Generic.IReadOnlyList`1[[Octokit.Issue, Octokit, Version=0.48.0.0, Culture=neutral, PublicKeyToken=null]], System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]")]

现在，“最短”签名需要一个 int64 参数：

let m = client.Issue.GetAllForRepository;;
val m :
  (int64 ->
     System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>)

我可以显式声明签名并接收相同的方法：

let m: (int64 -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;
val m :
  (int64 ->
     System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>)

但是访问(string, string) 版本给了我：

let m: (string -> string -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;

  let m: (string -> string -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;
  --------------------------------------------------------------------------------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

stdin(33,117): error FS0193: Type constraint mismatch. The type
    'string'
is not compatible with type
    'int64'

尝试访问具有多个参数的任何其他重载时会发生类似错误：

let m: (int64 -> Octokit.RepositoryIssueRequest -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;

  let m: (int64 -> Octokit.RepositoryIssueRequest -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;
  -------------------------------------------------------------------------------------------------------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

stdin(37,140): error FS0001: This expression was expected to have type
    'Octokit.RepositoryIssueRequest -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>'
but here has type
    'System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>'

let m: (int64 -> Octokit.RepositoryIssueRequest -> Octokit.ApiOptions -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.- GetAllForRepository;;

  let m: (int64 -> Octokit.RepositoryIssueRequest -> Octokit.ApiOptions -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>) = client.Issue.GetAllForRepository;;
  -----------------------------------------------------------------------------------------------------------------------------------------------------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

stdin(36,162): error FS0001: This expression was expected to have type
    'Octokit.RepositoryIssueRequest -> Octokit.ApiOptions -> System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>'
but here has type
    'System.Threading.Tasks.Task<System.Collections.Generic.IReadOnlyList<Octokit.Issue>>'

那么，我在类型注释方面做错了吗？

Answer 1

是的，类型注释将允许您选择所需的方法覆盖：

type MyClass() =
    member __.MyMethod() = 1
    member __.MyMethod(x : int) = 2

let o = MyClass()
let m1 : (unit -> int) = o.MyMethod
let m2 : (int -> int) = o.MyMethod
printfn "%A" <| m1 ()
printfn "%A" <| m2 0

Answer 2

响应您的编辑，该方法的输入是 string * string，而不是 string -> string（即 uncurried 与 curried），所以我认为这会起作用：

let m : (string * string -> _) = client.Issue.GetAllForRepository