> I still don't understand why this is necessary. Why must code compiled with GHC 9.6 use base version 4.18.0.0? Why should the binary that is GHC care about which version of the Data.List module the code that it compiles uses?
Because the underlying data types might be different, so if different libraries linking to different `base` implementations pass each other instances of `Data.List`. Imagine for example a Data.List Data.List, could you append the results of functions out of two different libraries to that list?
I'm not suggesting that my library should be able to transitively depend on multiple versions of base.
I'm suggesting that which version of base my library depends on should not be tied to what the GHC version (used to build my library) depends on — unless my library is using the GHC-specific stuff in base.
Oh yeah, I think that's just a convenience thing. New versions of base probably use new features of GHC, so you'd end up with a backwards compatibility matrix. People would get angry either way, and I guess it's more convenient to not put in the work and just have people angry all the time so no one can say they've been misled about GHC's stability.
Because the underlying data types might be different, so if different libraries linking to different `base` implementations pass each other instances of `Data.List`. Imagine for example a Data.List Data.List, could you append the results of functions out of two different libraries to that list?