Michael Snoyman wrote:
Can you give an example of a concrete problem you're expecting to run into?
Package foo uploads a new version with a critical bug fix. As is often the case, this new version also supports updated dependencies, including exceptions. The new exceptions breaks the old SomeException type, so foo is forced to specify a lower bound that excludes the old exceptions. I depend on foo and I need to compile using GHC 7.8. Can I get this critical bug fix for foo? We can't always prevent this kind of scenario. And when it does happen in an isolated case, there are work-arounds. But for a ubiquitous dependency like exceptions, this single breaking change would effectively block future upgrades of a significant proportion of Hackage for GHC 7.8.