Hello, I just noticed that the public Hackage server has started refusing to accept packages that do not have an upper bound on "base". I think that this crosses the line of useful static checking and, instead of helping package maintainers, it creates more work for them. (A warning to the same effect would be just fine.) Why do I think that? Choosing a conservative upper bound for the 'base' dependency of a library does not really lead to more stable builds---while it ensures that your library will build correctly, it tends to cause failures in the building of applications that use your library (because there is no set of packages that satisfies the combined dependencies). This is particularly true for the case of "base" because all packages depend on it. So placing a conservative constraint automatically makes your library incompatible with any package that might use a feature that was introduced after the constraint. While, in principle, "base" could completely change in the future, in practice there is a fairly large set of functions that are quite stable and it is not hard to write fairly future proof code. I think that it should be up to the maintainer to decide if they have an upper bound or not, just like with any other package. -Iavor