generics - 由于 "ambiguity"，F# 通用约束不起作用

Question

我有一个应用程序，它呈现钢琴谱，因此我必须将一些乐谱概念抽象成记录结构。为了节省一些输入，我有时会添加成员 FromTuple到某些记录类型。

我还介绍了运营商!> ，它接受一个元组并返回适当的元组。
但是，我确实有以下问题:

FS0332: Could not resolve the ambiguity inherent in the use of the operator 'FromTuple' at or near this program point. Consider using type annotations to resolve the ambiguity.

我找不到我的错误的实际来源(我首先想到可能在多种记录类型中定义/使用了某些记录字段名称，但似乎并非如此)。

类型定义:

type xyz =
    {
        // some record fields
        Field1 : int
        Field2 : bool
        Field3 : string * string
    }
    with
        static member FromTuple (a, b, c) = { Field1 = a; Field2 = b; Field3 = c }

// more types defined like `xyz`

[<AutoOpen>]
module Globals =
    let inline (!>) x = (^b : (static member FromTuple : ^a -> ^b) x)

错误行(在单独的文件中):

//ERROR
let my_xyz : xyz = !> (315, false, ("foo", "bar"))

Answer 1

您的 xyz.FromTuple方法采用三个单独的参数:a: int , b: bool , 和 c: string * string ;相反，您需要它来获取单个 int * bool * (string * string) .通过将参数包装在另一组括号中来执行此操作:

static member FromTuple ((a, b, c)) = { Field1 = a; Field2 = b; Field3 = c }