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