#13072: Move large tuples to a separate module in base -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: rwbarton Type: task | Status: new Priority: normal | Milestone: 8.2.1 Component: libraries/base | Version: 8.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
any time the user loaded an interface file with their own type family instances, GHC would read the interface file for GHC.LargeTuple too to make sure there were no conflicts
I don't think so. If M contains a type family instance, that instance should have been checked for consistency with `LargeTuple`. See `FamInst`: {{{ Note [Checking family instance consistency] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ For any two family instance modules that we import directly or indirectly, we check whether the instances in the two modules are consistent, *unless* we can be certain that the instances of the two modules have already been checked for consistency during the compilation of modules that we import. }}} So `M` and `LargeTuple` have already been checked; so importers of `M` won't need to check. Right? To be sure it's a bit of a pain having to load `LargeTuple` for `M`. But you suggested solution sounds ad-hoc and fragile to me. One possibility might be this: rather than a "family instance module" being a boolean flag, keep a list of the type functions it has instances of. Now if A defines instances of FA and B defines instances of FB we don't need to check them against each other. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13072#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler