public static Validation <MonoidFail, Fail, A> headOrInvalid <MonoidFail, Fail, A>(Seq <A> list, Fail fail) where MonoidFail : struct, Monoid <Fail>, Eq <Fail> => list.HeadOrInvalid <MonoidFail, Fail, A>(fail);
public static Validation <Fail, A> headOrInvalid <Fail, A>(Seq <A> list, Fail fail) => list.HeadOrInvalid(fail);