:: Ord a => [a] -> [a] -package:list-t -package:Cabal-syntax -package:imports -package:containers -package:errors -package:incipit-base -package:basement -package:lifted-base -package:integration -package:Cabal is:exact -package:extra 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.