George Russell wrote:
> This scheme is not the cleverest that could be devised. For example it is
> still necessary to recompile whole chains of modules if you add an import
> declaration. (Not to a system library, imports from those are counted as
> "stable" in GHCs and my system.) To fix this you would need to keep more
> information in the .hi file.
Actually we can catch most of these cases too. Alter algorithm A so that
if we have no changes to instances declarations in this file, the version
numbers in directly imported modules are all the same, and the only change
is that we import some modules we didn't import before, then only bump the
version number if the import leads to new modules being imported which contain
instance declarations. I think you can compute this at very close to zero
cost at the start of compilation, when you are doing the imports.
