:: Ord a => [a] -> [a] is:exact -package:stm-containers -package:extra -package:mono-traversable -package:Cabal-syntax -package:base-prelude -package:basement -package:incipit-base -package:safe -package:Cabal -package:statistics -package:ghc package:parsers
Take a parser that may consume input, and on failure, go back to where
we started and fail as if we didn't consume input.