:: Ord a => [a] -> [a] -package:list-t -package:incipit-base -package:errors -package:Cabal-syntax -package:safe -package:integration -package:extra -package:witherable -package:mono-traversable -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.