:: Ord a => [a] -> [a] -package:html-entities -is:exact -package:base -package:statistics -package:extra -package:errors is:exact -package:Cabal -package:Cabal-syntax -package:containers -package:integration -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.