In fourmolu/fourmolu#357 (comment), it took a bit before realizing that NoImplicitPrelude is causing Prelude operators from getting the correct fixity. Is there some way we can make debugging this easier, e.g. when --debug is turned on? Perhaps when --debug is turned on, show warnings when operators from base are detected with different fixity info? I think base is an important enough package to special case this logic. Or perhaps show the warning if any operators have different fixity than in the Hackage fixity map? Since this would only show up with --debug, I think being a bit noisy with false positives is better than otherwise