Generics 如何防止推断类型为obj（或错误）

下面的代码让我有些头疼

type Config() = class end
type ProgressA<'a>(v: 'a) = class end
type DoneA<'a>(v:'a) = class end

type Foo () = class end

type ProgressX = ProgressA<Foo>
type DoneX = DoneA<Foo>

let somethingElse = 1

type Foo with
    static member inline Validate (_:Config) (p:ProgressX) : Option<ProgressX> = Some p


let inline validatex c p =
    (^T : (static member Validate: ^V -> ^P -> Option<ProgressA< ^T>>) c, p)

let p1: ProgressX = Unchecked.defaultof<_>
let v1: Config = Unchecked.defaultof<_>

let c = validatex v1 p1

到

---

告诉我无法为

p1

找到方法

Validate

，噢，我的天哪！我找到了解决方案…
一句话：元组

问题似乎是，只有在成员函数的参数是单元组参数的情况下，类型推断器才能在这种情况下正确运行

type Foo with
                                  //see the double parens
    static member inline Validate ((_:Config, p:ProgressX)): Option<ProgressX> = Some p

//And then you need a lot of parens here as well
let inline validatex c p =
    (^T : (static member Validate: (^V * ProgressA< ^T>) -> Option<ProgressA< ^T>>) ((c, p)))

使用
//看到双帕伦夫妇了吗
静态成员内联验证（（：Config，p:ProgressX））：Option=Some p
//然后你也需要很多父母
让我们内联验证excp=
（^T:（静态成员验证：（^V*ProgressA<^T>）->Option>）（（c，p）））

let inline validatex c p =
    (^T : (static member Validate: ^V -> ProgressA< ^T> -> Option<ProgressA< ^T>>) c, p)

let c = validatex v1 p1

type Foo with
                                  //see the double parens
    static member inline Validate ((_:Config, p:ProgressX)): Option<ProgressX> = Some p

//And then you need a lot of parens here as well
let inline validatex c p =
    (^T : (static member Validate: (^V * ProgressA< ^T>) -> Option<ProgressA< ^T>>) ((c, p)))