Static duck-typing in F#

gistfile1.fs

let inline inTheForest (a: ^a) = 
    (^a : (member Quack: unit -> unit) (a))
    (^a : (member Feathers: unit -> unit) (a))
    ()
 
type Duck() =
    member x.Quack() = printfn "Quaaaaaack!"
    member x.Feathers() = printfn "The duck has white and gray feathers."
 
type Person() =
    member x.Quack() = printfn "The person imitates a duck."
    member x.Feathers() = printfn "The person takes a feather from the ground and shows it."
 
type Dove() =
    member x.Feathers() = printfn "The pidgin has white feathers"
 
inTheForest(new Duck())
inTheForest(new Person())
inTheForest(new Dove()) //Compile error: The type 'Dove' does not support the operator 'Quack'.