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