F# Question 1

F# question 1

// I like to create class type that accepts a generic enhancer function
// I tried 3 variants and nothing gives me the result I need
// Anyone has any ideas?

// warning FS0064: This construct causes code to be less generic than indicated by
//  the type annotations. The type variable 'U has been constrained to be type 'obj'.
type MyTest1<'T>(enhancer : 'U->'U) =
    let whatever = 3

type MyTest2<'T>() =
    // warning FS0064: This construct causes code to be less generic than indicated by
    //  the type annotations. The type variable 'U has been constrained to be type 'obj'.
    let mutable enhancer : 'U->'U = fun x -> x
    member x.Enhancer
        with get () = enhancer
        and set e   = enhancer <- e

    member x.Enhance (u : 'U) : 'U = enhancer u

type IEnhancer =
    interface
        abstract Enhance : 'U -> 'U
    end

type MyTest3<'T>(enhancer : IEnhancer) =

    member x.Enhance (u : 'U) : 'U = enhancer.Enhance u

let Create3<'T> (enhancer : 'U->'U) =
    let e =
        {
            new IEnhancer with
                // error FS0670: This code is not sufficiently generic. The type variable
                //  'a could not be generalized because it would escape its scope.
                member x.Enhance (u : 'U) : 'U = enhancer u
        }
    MyTest3<'T> (e)

[<EntryPoint>]
let main argv =
    0