F＃lambda与Func的重载分辨率(overload resolution of F# lambda vs Func)

 我将静态构建器方法添加到像这样的记录类型： 
 
type ThingConfig = { url: string; token : string; } with
    static member FromSettings (getSetting : (string -> string)) : ThingConfig =
        {
            url = getSetting "apiUrl";
            token = getSetting "apiToken";
        }
 
 我可以这样称呼它： 
 
let config = ThingConfig.FromSettings mySettingsAccessor
 
 现在，棘手的部分：我想添加第二个重载的构建器从C＃中使用（现在忽略重复的实现）： 
 
static member FromSettings (getSetting : System.Func<string,string>) : ThingConfig =
    {
        url = getSetting.Invoke "apiUrl";
        token = getSetting.Invoke "apiToken";
    }
 
 这适用于C＃，但打破了我以前的F＃调用错误FS0041：无法根据此程序点之前的类型信息确定方法'FromSettings'的唯一重载。 可能需要类型注释。 候选人：静态成员ThingConfig.FromSettings：getSetting：（字符串 - >字符串） - > ThingConfig，静态成员ThingConfig.FromSettings：getSetting：Func - > ThingConfig 
 
 为什么F＃不知道要调用哪一个？ 
 
 那种类型的注释是什么样的？ （我可以注释来自呼叫站点的参数类型吗？） 
 
 这种互操作模式有没有更好的模式？ （重载接受来自C＃和F＃的lambdas） 

I'm adding a static builder method to a record type like this:
 
type ThingConfig = { url: string; token : string; } with
    static member FromSettings (getSetting : (string -> string)) : ThingConfig =
        {
            url = getSetting "apiUrl";
            token = getSetting "apiToken";
        }
 
I can call it like this:
 
let config = ThingConfig.FromSettings mySettingsAccessor
 
Now the tricky part: I'd like to add a second overloaded builder for use from C# (ignore the duplicated implementation for now):
 
static member FromSettings (getSetting : System.Func<string,string>) : ThingConfig =
    {
        url = getSetting.Invoke "apiUrl";
        token = getSetting.Invoke "apiToken";
    }
 
This works for C#, but breaks my earlier F# call with error FS0041: A unique overload for method 'FromSettings' could not be determined based on type information prior to this program point. A type annotation may be needed. Candidates: static member ThingConfig.FromSettings : getSetting:(string -> string) -> ThingConfig, static member ThingConfig.FromSettings : getSetting:Func -> ThingConfig
 
Why can't F# figure out which one to call?
 
What would that type annotation look like? (Can I annotate the parameter type from the call site?)
 
Is there a better pattern for this kind of interop? (overloads accepting lambdas from both C# and F#)

原文：https://stackoverflow.com/questions/49164915