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f# - 为什么这个 F# 引用在运行时失败？

问题描述

我试图理解为什么这个 F# 脚本在运行时失败。

#r "nuget: FsToolkit.ErrorHandling, 2.2.0"

open System
open FsToolkit.ErrorHandling

<@@ async {
        return!
          asyncResult {
            return! (Result.Ok true)
          }
} @@>

错误：

$ dotnet fsi ./Quotations.fsx

System.InvalidOperationException: Could not bind function AsyncResultBuilder.Source in type FsToolkit.ErrorHandling.AsyncResultCEExtensions
   at Microsoft.FSharp.Quotations.PatternsModule.fail@1118[a](Type ty, String nm, Unit unitVar0) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1118
   at Microsoft.FSharp.Quotations.PatternsModule.bindModuleFunctionWithCallSiteArgs$cont@1110(Type ty, String nm, Type[] argTypes, Type[] tyArgs, Unit unitVar) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1169
   at Microsoft.FSharp.Quotations.PatternsModule.bindModuleFunctionWithCallSiteArgs(Type ty, String nm, FSharpList`1 argTypes, FSharpList`1 tyArgs) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1105
   at Microsoft.FSharp.Quotations.PatternsModule.u_ModuleDefn@1572-1.Invoke(FSharpList`1 argTypes, FSharpList`1 tyargs) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1576
   at Microsoft.FSharp.Quotations.PatternsModule.u_constSpec@1636.Invoke(FSharpList`1 argTypes, FSharpList`1 tyargs) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1636
   at Microsoft.FSharp.Quotations.PatternsModule.u_Expr@1492.Invoke(BindingEnv env) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1501
   at Microsoft.FSharp.Primitives.Basics.List.mapToFreshConsTail[a,b](FSharpList`1 cons, FSharpFunc`2 f, FSharpList`1 x) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\local.fs:line 239
   at Microsoft.FSharp.Primitives.Basics.List.map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 x) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\local.fs:line 247
   at Microsoft.FSharp.Quotations.PatternsModule.u_Expr@1492.Invoke(BindingEnv env) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1493
   at Microsoft.FSharp.Quotations.PatternsModule.u_Expr@1508-2.Invoke(BindingEnv env) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\quotations.fs:line 1508
   at Microsoft.FSharp.Primitives.Basics.List.mapToFreshConsTail[a,b](FSharpList`1 cons, FSharpFunc`2 f, FSharpList`1 x) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\local.fs:line 239
   at Microsoft.FSharp.Primitives.Basics.List.map[T,TResult](FSharpFunc`2 mapping, FSharpList`1 x) in F:\workspace\_work\1\s\src\fsharp\FSharp.Core\local.fs:line 247
...

这是 F# 引用的问题吗？还是FsToolkit.ErrorHandling包裹？

请解释错误信息及其发生原因。

标签： f#quotations

解决方案

正如上面的答案所述，它可能是由于报价中的过载解决而发生的。但是您可以通过将 builder 包装在一个函数中来解决这个问题，然后将其传递给一个引号：

let returnResult =
  asyncResult {
    return! (Result.Ok true)
  }
      
let quotation =
  <@@
    async {
      return! returnResult
    }
  @@>
  
...

这里returnResult将是一个返回的ValueOp内部。ValueWithNamereturnResult FSharpFunc

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