The @FamInst@ type: family instance heads
\begin{code}
-{-# OPTIONS_GHC -w #-}
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
--- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
--- for details
-
module FamInst (
- checkFamInstConsistency, tcExtendLocalFamInstEnv
+ checkFamInstConsistency, tcExtendLocalFamInstEnv, tcGetFamInstEnvs
) where
-#include "HsVersions.h"
-
import HscTypes
import FamInstEnv
+import LoadIface
import TcMType
-import TcType
import TcRnMonad
import TyCon
-import Type
import Name
import Module
import SrcLoc
import Outputable
import UniqFM
-import FiniteMap
+import FastString
-import Maybe
-import Monad
+import Maybes
+import Control.Monad
+import Data.Map (Map)
+import qualified Data.Map as Map
\end{code}
be certain that the instances of the two modules have already been checked for
consistency during the compilation of modules that we import.
+Why do we need to check? Consider
+ module X1 where module X2 where
+ data T1 data T2
+ type instance F T1 b = Int type instance F a T2 = Char
+ f1 :: F T1 a -> Int f2 :: Char -> F a T2
+ f1 x = x f2 x = x
+
+Now if we import both X1 and X2 we could make (f2 . f1) :: Int -> Char.
+Notice that neither instance is an orphan.
+
How do we know which pairs of modules have already been checked? Any pair of
modules where both modules occur in the `HscTypes.dep_finsts' set (of the
`HscTypes.Dependencies') of one of our directly imported modules must have
-- Sets of module pairs
--
-type ModulePairSet = FiniteMap ModulePair ()
+type ModulePairSet = Map ModulePair ()
listToSet :: [ModulePair] -> ModulePairSet
-listToSet l = listToFM (zip l (repeat ()))
+listToSet l = Map.fromList (zip l (repeat ()))
checkFamInstConsistency :: [Module] -> [Module] -> TcM ()
checkFamInstConsistency famInstMods directlyImpMods
; (eps, hpt) <- getEpsAndHpt
; let { -- Fetch the iface of a given module. Must succeed as
- -- all imported modules must already have been loaded.
+ -- all directly imported modules must already have been loaded.
modIface mod =
case lookupIfaceByModule dflags hpt (eps_PIT eps) mod of
Nothing -> panic "FamInst.checkFamInstConsistency"
Just iface -> iface
; hmiModule = mi_module . hm_iface
- ; hmiFamInstEnv = mkFamInstEnv . md_fam_insts . hm_details
- ; mkFamInstEnv = extendFamInstEnvList emptyFamInstEnv
- ; hptModInsts = [ (hmiModule hmi, hmiFamInstEnv hmi)
- | hmi <- eltsUFM hpt]
- ; modInstsEnv = eps_mod_fam_inst_env eps -- external modules
- `extendModuleEnvList` -- plus
- hptModInsts -- home package modules
+ ; hmiFamInstEnv = extendFamInstEnvList emptyFamInstEnv
+ . md_fam_insts . hm_details
+ ; hpt_fam_insts = mkModuleEnv [ (hmiModule hmi, hmiFamInstEnv hmi)
+ | hmi <- eltsUFM hpt]
; groups = map (dep_finsts . mi_deps . modIface)
directlyImpMods
; okPairs = listToSet $ concatMap allPairs groups
-- instances of okPairs are consistent
; criticalPairs = listToSet $ allPairs famInstMods
-- all pairs that we need to consider
- ; toCheckPairs = keysFM $ criticalPairs `minusFM` okPairs
+ ; toCheckPairs = Map.keys $ criticalPairs `Map.difference` okPairs
-- the difference gives us the pairs we need to check now
}
- ; mapM_ (check modInstsEnv) toCheckPairs
+ ; mapM_ (check hpt_fam_insts) toCheckPairs
}
where
allPairs [] = []
allPairs (m:ms) = map (ModulePair m) ms ++ allPairs ms
- -- The modules are guaranteed to be in the environment, as they are either
- -- already loaded in the EPS or they are in the HPT.
- --
- check modInstsEnv (ModulePair m1 m2)
- = let { instEnv1 = fromJust . lookupModuleEnv modInstsEnv $ m1
- ; instEnv2 = fromJust . lookupModuleEnv modInstsEnv $ m2
- ; insts1 = famInstEnvElts instEnv1
- }
- in
- mapM_ (checkForConflicts (emptyFamInstEnv, instEnv2)) insts1
+ check hpt_fam_insts (ModulePair m1 m2)
+ = do { env1 <- getFamInsts hpt_fam_insts m1
+ ; env2 <- getFamInsts hpt_fam_insts m2
+ ; mapM_ (checkForConflicts (emptyFamInstEnv, env2))
+ (famInstEnvElts env1) }
+
+getFamInsts :: ModuleEnv FamInstEnv -> Module -> TcM FamInstEnv
+getFamInsts hpt_fam_insts mod
+ | Just env <- lookupModuleEnv hpt_fam_insts mod = return env
+ | otherwise = do { _ <- initIfaceTcRn (loadSysInterface doc mod)
+ ; eps <- getEps
+ ; return (expectJust "checkFamInstConsistency" $
+ lookupModuleEnv (eps_mod_fam_inst_env eps) mod) }
+ where
+ doc = ppr mod <+> ptext (sLit "is a family-instance module")
\end{code}
%************************************************************************
-- (since we do unification).
-- We use tcInstSkolType because we don't want to allocate
-- fresh *meta* type variables.
- ; let { tycon = famInstTyCon famInst
- ; ty = case tyConFamInst_maybe tycon of
- Nothing -> panic "FamInst.checkForConflicts"
- Just (tc, tys) -> tc `mkTyConApp` tys
- }
- ; (tvs', _, tau') <- tcInstSkolType FamInstSkol ty
-
- ; let (fam, tys') = tcSplitTyConApp tau'
-
- ; let { matches = lookupFamInstEnvUnify inst_envs fam tys'
- ; conflicts = [ conflictingFamInst
- | match@((conflictingFamInst, _), _) <- matches
- , conflicting tycon match
- ]
- }
+
+ ; skol_tvs <- tcInstSkolTyVars (tyConTyVars (famInstTyCon famInst))
+ ; let conflicts = lookupFamInstEnvConflicts inst_envs famInst skol_tvs
; unless (null conflicts) $
- conflictInstErr famInst (head conflicts)
+ conflictInstErr famInst (fst (head conflicts))
}
where
- -- * In the case of data family instances, any overlap is fundamentally a
- -- conflict (as these instances imply injective type mappings).
- -- * In the case of type family instances, overlap is admitted as long as
- -- the right-hand sides of the overlapping rules coincide under the
- -- overlap substitution. We require that they are syntactically equal;
- -- anything else would be difficult to test for at this stage.
- conflicting tycon1 ((famInst2, _), subst)
- | isAlgTyCon tycon1 = True
- | otherwise = not (rhs1 `tcEqType` rhs2)
- where
- tycon2 = famInstTyCon famInst2
- rhs1 = substTy subst $ synTyConType tycon1
- rhs2 = substTy subst $ synTyConType tycon2
+conflictInstErr :: FamInst -> FamInst -> TcRn ()
conflictInstErr famInst conflictingFamInst
= addFamInstLoc famInst $
- addErr (hang (ptext SLIT("Conflicting family instance declarations:"))
+ addErr (hang (ptext (sLit "Conflicting family instance declarations:"))
2 (pprFamInsts [famInst, conflictingFamInst]))
+addFamInstLoc :: FamInst -> TcRn a -> TcRn a
addFamInstLoc famInst thing_inside
= setSrcSpan (mkSrcSpan loc loc) thing_inside
where
loc = getSrcLoc famInst
+
+tcGetFamInstEnvs :: TcM (FamInstEnv, FamInstEnv)
+-- Gets both the external-package inst-env
+-- and the home-pkg inst env (includes module being compiled)
+tcGetFamInstEnvs
+ = do { eps <- getEps; env <- getGblEnv
+ ; return (eps_fam_inst_env eps, tcg_fam_inst_env env) }
\end{code}
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