toString and fromString for discriminated unions

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open Microsoft.FSharp.Reflection

let toString (x:'a) = 
    match FSharpValue.GetUnionFields(x, typeof<'a>) with
    | case, _ -> case.Name

let fromString (t:System.Type) (s:string) =
    match FSharpType.GetUnionCases t |> Array.filter (fun case -> case.Name = s) with
    |[|case|] -> Some(FSharpValue.MakeUnion(case,[||]))
    |_ -> None

// Usage:
// type A = X|Y|Z with
//     member this.toString = toString this
//     static member fromString s = fromString typeof<A> s

// > X.toString;;
// val it : string = "X"

// > A.fromString "X";;
// val it : obj option = Some X

// > A.fromString "W";;
// val it : obj option = None

// > toString X;;
// val it : string = "X"

// > fromString typeof<A> "X";;
// val it : obj option = Some X

namespace Microsoft

namespace Microsoft.FSharp

namespace Microsoft.FSharp.Reflection

val toString : x:'a -> string

Full name: Script.toString

val x : 'a

type FSharpValue =
  static member GetExceptionFields : exn:obj * ?bindingFlags:BindingFlags -> obj []
  static member GetRecordField : record:obj * info:PropertyInfo -> obj
  static member GetRecordFields : record:obj * ?bindingFlags:BindingFlags -> obj []
  static member GetTupleField : tuple:obj * index:int -> obj
  static member GetTupleFields : tuple:obj -> obj []
  static member GetUnionFields : value:obj * unionType:Type * ?bindingFlags:BindingFlags -> UnionCaseInfo * obj []
  static member MakeFunction : functionType:Type * implementation:(obj -> obj) -> obj
  static member MakeRecord : recordType:Type * values:obj [] * ?bindingFlags:BindingFlags -> obj
  static member MakeTuple : tupleElements:obj [] * tupleType:Type -> obj
  static member MakeUnion : unionCase:UnionCaseInfo * args:obj [] * ?bindingFlags:BindingFlags -> obj
  ...

Full name: Microsoft.FSharp.Reflection.FSharpValue

static member FSharpValue.GetUnionFields : value:obj * unionType:System.Type * ?allowAccessToPrivateRepresentation:bool -> UnionCaseInfo * obj []
static member FSharpValue.GetUnionFields : value:obj * unionType:System.Type * ?bindingFlags:System.Reflection.BindingFlags -> UnionCaseInfo * obj []

val typeof<'T> : System.Type

Full name: Microsoft.FSharp.Core.Operators.typeof

val case : UnionCaseInfo

property UnionCaseInfo.Name: string

val fromString : t:System.Type -> s:string -> obj option

Full name: Script.fromString

val t : System.Type

namespace System

type Type =
  inherit MemberInfo
  member Assembly : Assembly
  member AssemblyQualifiedName : string
  member Attributes : TypeAttributes
  member BaseType : Type
  member ContainsGenericParameters : bool
  member DeclaringMethod : MethodBase
  member DeclaringType : Type
  member Equals : o:obj -> bool + 1 overload
  member FindInterfaces : filter:TypeFilter * filterCriteria:obj -> Type[]
  member FindMembers : memberType:MemberTypes * bindingAttr:BindingFlags * filter:MemberFilter * filterCriteria:obj -> MemberInfo[]
  ...

Full name: System.Type

val s : string

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

type FSharpType =
  static member GetExceptionFields : exceptionType:Type * ?bindingFlags:BindingFlags -> PropertyInfo []
  static member GetFunctionElements : functionType:Type -> Type * Type
  static member GetRecordFields : recordType:Type * ?bindingFlags:BindingFlags -> PropertyInfo []
  static member GetTupleElements : tupleType:Type -> Type []
  static member GetUnionCases : unionType:Type * ?bindingFlags:BindingFlags -> UnionCaseInfo []
  static member IsExceptionRepresentation : exceptionType:Type * ?bindingFlags:BindingFlags -> bool
  static member IsFunction : typ:Type -> bool
  static member IsModule : typ:Type -> bool
  static member IsRecord : typ:Type * ?bindingFlags:BindingFlags -> bool
  static member IsTuple : typ:Type -> bool
  ...

Full name: Microsoft.FSharp.Reflection.FSharpType

static member FSharpType.GetUnionCases : unionType:System.Type * ?allowAccessToPrivateRepresentation:bool -> UnionCaseInfo []
static member FSharpType.GetUnionCases : unionType:System.Type * ?bindingFlags:System.Reflection.BindingFlags -> UnionCaseInfo []

module Array

from Microsoft.FSharp.Collections

val filter : predicate:('T -> bool) -> array:'T [] -> 'T []

Full name: Microsoft.FSharp.Collections.Array.filter

union case Option.Some: Value: 'T -> Option<'T>

static member FSharpValue.MakeUnion : unionCase:UnionCaseInfo * args:obj [] * ?allowAccessToPrivateRepresentation:bool -> obj
static member FSharpValue.MakeUnion : unionCase:UnionCaseInfo * args:obj [] * ?bindingFlags:System.Reflection.BindingFlags -> obj

union case Option.None: Option<'T>