non-strict convert()

[lawremi]

It would be nice to have the equivalent of methods::as(strict = FALSE), which ensures that from inherits from to but does not force from to be an instance of to (stripping any extra properties).

Maybe this is a different function, like convert_lazy() or ensure_inherits().

[hadley]

Your proposal is basically equivalent to this S3 code, right?

if (!is.data.frame(x)) {
  x <- as.data.frame(x)
}