public static R failure <R, L>(Either <R, L> either, R noneValue) => either.Failure(noneValue);
public static R failure <L, R>(Either <L, R> either, R noneValue) => either.Failure(noneValue);
public static R failure <R, L>(Either <R, L> either, Func <R> None) => either.Failure(None);
public static R failure <L, R>(Either <L, R> either, Func <R> None) => either.Failure(None);