Plugins and rebuilding of packages
I discovered that when a plugin is enabled, ghc will rebuild all modules even if only the top level one changed.
I created a minimal example to reproduce this issue, see the repo.
If one compiles both modules and then modify the top level one (B.hs) and then recompiles again what ghc will do depends whether a plugin is enabled or not. In the first case it only recompiles the modified module, in the other case it will recompile both modules. I would rather expect that for pure plugins ghc will have the same behaviour when plugins are disabled.