Support for R6 classes in otype() and ftype()

[fangly]

Hi Hadley,

I am surprised that otype() and ftype() do not detect and report when the argument is an R6 object/method... yet. It would be great to have them support R6 in the future.

library(R6)
Person <- R6Class("Person",
  public = list(
    name = NULL,
    hair = NULL,
    initialize = function(name = NA, hair = NA) {
      self$name <- name
      self$hair <- hair
      self$greet()
    },
    set_hair = function(val) {
      self$hair <- val
    },
    greet = function() {
      cat(paste0("Hello, my name is ", self$name, ".\n"))
    }
  )
)
ann <- Person$new("Ann", "black")
otype(ann)

This example should return "R6", not "S3".

Cheers,
Florent