:: Ord a => [a] -> [a] -package:html-entities -package:Cabal-syntax -package:imports -package:integration -package:ghc -is:exact -package:mono-traversable -package:extra -package:containers -package:safe -package:lifted-base package:parsers is:exact
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.