Context information for roxygen2 documentation blocks

[krlmlr]

Last time I looked, the documentation blocks were available as a character vector, without context information. I wonder if we could add context information to each line processed, to support inline parameter documentation and R6 documentation (#306):

#' Some function 
fun <- function(
  a, #' description of argument a
  b = NULL) #' description of argument b
{
  ret <- process_it(a, b)
  ret #' a character vector
}

would be equivalent to

#' Some function
#' @param a description of argument a
#' @param b description of argument b
#' @return a character vector

This came up on the @RDocTaskForce mailing list.

[hadley]

I'm largely in favour of this, as long as it doesn't make the internals a lot more complicated.

[hadley]

I think this is basically done - the roxy_block class stores filename and line number, so you should be able to recreate the context if needed. Once you figure out exactly what you need, I'll be happy to review a PR that extends roxy_block with new fields.