Casting issues with dynamic object

[Freymaurer]

So this is more or less a collection of things i found missing and i am not sure if these are even possible/how to implement them.

1. Downcasting dynamic objects. Found this issue, when i played around with the DynamicObj.ofJson function i added. It will return a DynamicObj which cannot be downcaster to any type inheriten DynamicObj. The workaround is to use CopyDynamicPropertiesTo on the inerhiting type.

type Logger() =
    inherit DynamicObj()

let logger = Logger()
logger.SetValue ("key", "value")

let dynObj : DynamicObj = DynamicObj()
dynObj.SetValue ("key", "value")

// upcast
let d2 = logger :> DynamicObj // upcast works without issue
d2.TryGetValue "key" // Some "value"

// downcast
dynObj :?> Logger 
// Error: System.InvalidCastException: Unable to cast object of type 'DynamicObj.DynamicObj' to type 'Logger'.

//workaround
dynObj.CopyDynamicPropertiesTo logger 

2. Cast DynamicObj to (anonymous) record type. This could be especially nice for the TryGetTypedValue member.

type MyRecordType = {|
    key: string
|}

let dynObj : DynamicObj = DynamicObj()
dynObj.SetValue ("key", "value")

dynObj :?> MyRecordType
// Type constraint mismatch. The type 'MyRecordType'  is not compatible with type 'DynamicObj

[Freymaurer]

Soo just made up this poc example, the following could be used in the style of DynamicObj.TryGetTypedValue.

#r "nuget: DynamicObj, 1.0.1"

open DynamicObj

type MyType = {
    Key: string
    Port: int
}

open FSharp.Reflection

type Logger() =
    inherit DynamicObj()

    member inline this.getAsRecordType<'a>() =
        let t = typeof<'a>
        match FSharpType.IsRecord(t) with
        | true -> 
            let fieldValues = 
                FSharpType.GetRecordFields(t) 
                |> Array.map (fun x -> 
                    let vo = this.TryGetValue x.Name
                    if vo.IsNone then failwithf "Field %A does not exist." x.Name else vo.Value
                )
            FSharpValue.MakeRecord(t, fieldValues) :?> 'a
        | false ->
            failwithf "%A is not a record type." t.FullName

let dynObj = Logger()
dynObj.SetValue("Key", "Test Value")
dynObj.SetValue("Port", 8080)

let res = dynObj.getAsRecordType<MyType>()