Implementations of functions which have been introduced in R since version 3.0.0. The backports are conditionally exported which results in R resolving the function names to the version shipped with R (if available) and uses the implemented backports as fallback. This way package developers can make use of the new functions without worrying about the minimum required R version.
hasName()for R versions prior to 3.4.0
file.info()with backport for argument
file.mode()for R versions prior to 3.2.0