Don Syme

This is a bit different to #629 but I'm merging them, because they are both really about inferring some generic parameters from others

I'm not inclined to this feature * `upcast` and `downcast` are almost at the level of being deprecated in F# and almost never used in samples or tutorial cost. *...

@gusty I don't understand the specific technical proposal here :)

I agree `let mutable` should be usable inside the scope of the object expression Marking this as approved in principle.

Just to note curried application f x .prop The "." binds more tightly than space-as-application, same as f x .prop f x . prop And f x.prop Given F#'s indentation...

@TimLariviere Would the last of these be satisfying enough for your purposes, i.,e. ```fsharp VStack() { Label("Hello") .textColor(Color.Black) .font(size = 12.) .centerHorizontal() } |> _.backgroundColor(Color.Red) |> _.margin(10.) ``` I can...

An alternative is to allow union types to also have a common set of fields: ```fsharp type ShoppingCart = val DiscountCode: string | EmptyCart | CartWithItems of Items: string list...

@forki I note that some Elmish.Fable view models would definitely benefit from this, e.g. ```fsharp type Model = val User : UserData option | HomePageModel | LoginModel of Login.Model |...

@laenas I think the proposal you want it "prefer extension methods to intrinsic properties when arguments are given" Could you provide a code sample too please?

> Updated, but I'm curious about the concept of preference here - in the case that we're defining an extension method on top of an intrinsic property of a function-type,...