anchor.diff:      <@ (box true).GetType() @> |> check ((box true).GetType())
       <@ (box 'a').GetType() @> |> check ((box 'a').GetType())
       <@ (box "aaa").GetType() @> |> check ((box "aaa").GetType())
  +    <@ Struct(1).GetType() @> |> check (Struct(1).GetType())
   
     [<TestCase(1, 1)>]
     [<TestCase(1, 2)>]
  
positive.code:     <@ (box true).ToString() @> |> check ((box true).ToString())
      <@ (box 'a').ToString() @> |> check ((box 'a').ToString())
      <@ (box "aaa").ToString() @> |> check ((box "aaa").ToString())
  
    [<Test>]
    let ``value type get type`` () =
  
negative.code:     <@ "aaa".CompareTo(null) @> |> check ("aaa".CompareTo(null))
  
    [<Test>]
    let ``struct equals`` () =
      <@ Struct(1).Equals(Struct(1)) @> |> check (Struct(1).Equals(Struct(1)))
  
    [<Test>]
    let ``value type get type code`` () =
      <@ (1).GetTypeCode() @> |> check ((1).GetTypeCode())
      <@ (true).GetTypeCode() @> |> check ((true).GetTypeCode())
  