Testing for null reference in F#

Question

Given the following:

[]
type TweetUser = {
    [] Followers:int
    [

        

Answer 1

To cyclically expand on @Tomas' answer ;-]

let name = if not <| obj.ReferenceEquals (tweet.User, null)
              then tweet.User.Name
              else tweet.Sender.Name

or

let inline isNull (x:^T when ^T : not struct) = obj.ReferenceEquals (x, null)

Unchecked.defaultof<_> is doing the right thing and producing nulls for your record types; the issue is that the default equality operator uses generic structural comparison, which expects you to always play by F#'s rules when using F# types. In any case, a null-check really only warrants referential comparison in the first place.