Hi there. When I try to serialise an F# union with settings TypeNameHandling=TypeNameHandling.All the type name info is not saved as with other types:

type Tree =
    | Leaf of int
    | Branch of Tree[]

let x = Leaf 5
let json = JsonConvert.SerializeObject(x,
                   JsonSerializerSettings(TypeNameHandling=TypeNameHandling.All))

// json = """{"Case":"Leaf","Fields":[5]}"""

With F# records and classes, the type name is correctly saved.

I'm using Newtonsoft.Json v9.0.1, please tell me if you need any other info.

Cheers!