failed try on structural automapping

traverse_ShapeCombination_expr.fs

open System
open System.Reflection
open System.Collections
open Microsoft.FSharp.Reflection
open Microsoft.FSharp.Quotations
open Microsoft.FSharp.Quotations.ExprShape
open Microsoft.FSharp.Quotations.DerivedPatterns

let dump tag s = (string s).Dump(string tag); s

let getMethodInfo ( expr: Expr<'T> ) ( target: Type ) =
    let rec traverse quotation =
        match quotation with
        | SpecificCall expr ( e, types, exprs ) -> 
            ( expr, e, types, expr ) |> Dump
            Expr.Call ( Option.get e, null, exprs )
        | ShapeVar v -> Expr.Var v |> dump "ShapeVar"
        | ShapeLambda ( v, expr ) -> Expr.Lambda ( v, traverse expr ) |> dump "ShapeLambda"
        | ShapeCombination ( o, exprs ) ->
            RebuildShapeCombination ( o, List.map traverse exprs ) |> dump "ShapComb"
    match traverse expr with
    | Patterns.Call ( _, mi, _ ) -> Some mi
    | _ -> None

type CustomizedEntity () = class end
with
    member inline this.String = ""
    static member inline Parse ( _: string ) = CustomizedEntity ()

let private (|CustomEntityString|_|) o =
    let target = o.GetType ()
    let dummy = CustomizedEntity ()
    match getMethodInfo <@ dummy.String @> target with
    | Some meth ->
        meth.Invoke ( o, [||] ) |> Some
    | _ -> None
    
let writeObject = function
    | CustomEntityString value ->
        Some value
    | _ -> None    

module Option =

    let ofTupleBool (b, v) =
        if b
        then Some v else None

    let either orSome orNone = function
        | Some s -> orSome s
        | _ -> orNone
        
type Url = Url of System.Uri | Invalid
with
    member inline this.IsValid = ( function | Url _ -> true | _ -> false ) this
    member inline this.String = ( function | Url u -> string u | _ -> "" ) this
    member inline this.Value = ( function | Url u -> u | _ -> failwith "invalid" ) this
    static member inline Parse (s: string) =
        Uri.TryCreate ( s, UriKind.Absolute )
        |> Option.ofTupleBool |> Option.either Url Invalid
    static member inline empty = Invalid

writeObject ( Url.Parse "http://test" ) |> Dump