#12367: Commit adding instances to GHC.Generics regression compiler performance -------------------------------------+------------------------------------- Reporter: bgamari | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: 8.0.2 Component: Compiler | Version: 8.0.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): It turns out that the problem is actually a fair bit worse than described above. While `Foldable` imports `GHC.Generics` in order to provide instances for types in the latter (which should be fairly easy to fix with some reorganization), the other modules import `GHC.Generics merely to derive `Generic` instances for types they themselves define. One example of this is `Data.Monoid`, which defines a number of `newtype`s resembling, {{{#!hs newtype All = All { getAll :: Bool } deriving (Eq, Ord, Read, Show, Bounded, Generic) }}} It seems to me like we may want to consider moving the data types defined in `GHC.Generics` to a new `GHC.Generic.Internal` module. They could then be re-exported in `GHC.Generics`, which could also derive instances for these types. This would also allow us to move the `Foldable` instances for the generics types to `GHC.Generics`, since the latter could likely import `Data.Foldable` without fear of cycles. Really, though, this arguably leaves a large portion of the problem unsolved: users who use `GHC.Generics` (which is increasingly popular) still need to pay the full cost of importing it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12367#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler