type ToOptionString = ToOptionString
with
    static member ($) (_: ToOptionString, l: string) : Option<string> = Some l
    static member ($) (_: ToOptionString, l: Option<string>) : Option<string> = l
    static member ($) (_: ToOptionString, l: Option<int>) : Option<string> =
       l |>> sprintf "%A"

let inline toOptionString v = ToOptionString $ v

let x = toOptionString (Some 1)

A unique overload for method 'op_Dollar' could not be determined based on
type information prior to this program point. A type annotation may be
needed. Candidates:
static member ToOptionString.( $ ) : ToOptionString * l:Option<int> -> Option<string>,
static member ToOptionString.( $ ) : ToOptionString * l:Option<string> -> Option<string>

val toOptionString : v:'a -> '_arg3 (requires member ( $ ))