import BasicTypes
import TysWiredIn
import PrelNames
+
-- For generation of representation types
import TcEnv (tcLookupTyCon)
-import TcRnMonad (TcM, newUnique)
+import TcRnMonad
import HscTypes
+import BuildTyCl
import SrcLoc
import Bag
%************************************************************************
\begin{code}
-canDoGenerics :: TyCon -> Bool
+canDoGenerics :: TyCon -> Maybe SDoc
-- Called on source-code data types, to see if we should generate
-- generic functions for them.
+-- Nothing == yes
+-- Just s == no, because of `s`
canDoGenerics tycon
- = let result = not (any bad_con (tyConDataCons tycon)) -- See comment below
- -- We do not support datatypes with context (for now)
- && null (tyConStupidTheta tycon)
- -- We don't like type families
- && not (isFamilyTyCon tycon)
-
- in {- pprTrace "canDoGenerics" (ppr (tycon,result)) -} result
+ = mergeErrors (
+ -- We do not support datatypes with context
+ (if (not (null (tyConStupidTheta tycon)))
+ then (Just (ppr tycon <+> text "must not have a datatype context"))
+ else Nothing)
+ -- We don't like type families
+ : (if (isFamilyTyCon tycon)
+ then (Just (ppr tycon <+> text "must not be a family instance"))
+ else Nothing)
+ -- See comment below
+ : (map bad_con (tyConDataCons tycon)))
where
- bad_con dc = any bad_arg_type (dataConOrigArgTys dc) || not (isVanillaDataCon dc)
- -- If any of the constructor has an unboxed type as argument,
- -- then we can't build the embedding-projection pair, because
- -- it relies on instantiating *polymorphic* sum and product types
- -- at the argument types of the constructors
+ -- If any of the constructor has an unboxed type as argument,
+ -- then we can't build the embedding-projection pair, because
+ -- it relies on instantiating *polymorphic* sum and product types
+ -- at the argument types of the constructors
+ bad_con dc = if (any bad_arg_type (dataConOrigArgTys dc))
+ then (Just (ppr dc <+> text "must not have unlifted or polymorphic arguments"))
+ else (if (not (isVanillaDataCon dc))
+ then (Just (ppr dc <+> text "must be a vanilla data constructor"))
+ else Nothing)
+
-- Nor can we do the job if it's an existential data constructor,
-- Nor if the args are polymorphic types (I don't think)
bad_arg_type ty = isUnLiftedType ty || not (isTauTy ty)
+
+ mergeErrors :: [Maybe SDoc] -> Maybe SDoc
+ mergeErrors [] = Nothing
+ mergeErrors ((Just s):t) = case mergeErrors t of
+ Nothing -> Just s
+ Just s' -> Just (s <> text ", and" $$ s')
+ mergeErrors (Nothing :t) = mergeErrors t
\end{code}
%************************************************************************
(from_alts, to_alts) = mkSum (1 :: US) tycon datacons
--------------------------------------------------------------------------------
+-- The type instance synonym and synonym
+-- type instance Rep (D a b) = Rep_D a b
+-- type Rep_D a b = ...representation type for D ...
+--------------------------------------------------------------------------------
+
+tc_mkRepTyCon :: TyCon -- The type to generate representation for
+ -> MetaTyCons -- Metadata datatypes to refer to
+ -> TcM TyCon -- Generated representation0 type
+tc_mkRepTyCon tycon metaDts =
+-- Consider the example input tycon `D`, where data D a b = D_ a
+ do { -- `rep0` = GHC.Generics.Rep (type family)
+ rep0 <- tcLookupTyCon repTyConName
+
+ -- `rep0Ty` = D1 ... (C1 ... (S1 ... (Rec0 a))) :: * -> *
+ ; rep0Ty <- tc_mkRepTy tycon metaDts
+
+ -- `rep_name` is a name we generate for the synonym
+ ; rep_name <- newImplicitBinder (tyConName tycon) mkGenR
+ ; let -- `tyvars` = [a,b]
+ tyvars = tyConTyVars tycon
+
+ -- rep0Ty has kind * -> *
+ rep_kind = liftedTypeKind `mkArrowKind` liftedTypeKind
+
+ -- `appT` = D a b
+ appT = [mkTyConApp tycon (mkTyVarTys tyvars)]
+
+ ; buildSynTyCon rep_name tyvars (SynonymTyCon rep0Ty) rep_kind
+ NoParentTyCon (Just (rep0, appT)) }
+
+--------------------------------------------------------------------------------
-- Type representation
--------------------------------------------------------------------------------
return (mkD tycon)
-tc_mkRepTyCon :: TyCon -- The type to generate representation for
- -> MetaTyCons -- Metadata datatypes to refer to
- -> TcM TyCon -- Generated representation0 type
-tc_mkRepTyCon tycon metaDts =
--- Consider the example input tycon `D`, where data D a b = D_ a
- do
- uniq1 <- newUnique
- uniq2 <- newUnique
- -- `rep0Ty` = D1 ... (C1 ... (S1 ... (Rec0 a))) :: * -> *
- rep0Ty <- tc_mkRepTy tycon metaDts
- -- `rep0` = GHC.Generics.Rep (type family)
- rep0 <- tcLookupTyCon repTyConName
-
- let modl = nameModule (tyConName tycon)
- loc = nameSrcSpan (tyConName tycon)
- -- `repName` is a name we generate for the synonym
- repName = mkExternalName uniq1 modl (mkGenR0 (nameOccName (tyConName tycon))) loc
- -- `coName` is a name for the coercion
- coName = mkExternalName uniq2 modl (mkGenR0 (nameOccName (tyConName tycon))) loc
- -- `tyvars` = [a,b]
- tyvars = tyConTyVars tycon
- -- `appT` = D a b
- appT = [mkTyConApp tycon (mkTyVarTys tyvars)]
- -- Result
- res = mkSynTyCon repName
- -- rep0Ty has kind `kind of D` -> *
- (tyConKind tycon `mkArrowKind` liftedTypeKind)
- tyvars (SynonymTyCon rep0Ty)
- (FamInstTyCon rep0 appT
- (mkCoercionTyCon coName (tyConArity tycon)
- -- co : forall a b. Rep (D a b) ~ `rep0Ty` a b
- (CoAxiom tyvars (mkTyConApp rep0 appT) rep0Ty)))
-
- return res
-
--------------------------------------------------------------------------------
-- Meta-information
--------------------------------------------------------------------------------
, metaS :: [[TyCon]] }
instance Outputable MetaTyCons where
- ppr (MetaTyCons d c s) = ppr d <+> ppr c <+> ppr s
+ ppr (MetaTyCons d c s) = ppr d $$ vcat (map ppr c) $$ vcat (map ppr (concat s))
metaTyCons2TyCons :: MetaTyCons -> [TyCon]
metaTyCons2TyCons (MetaTyCons d c s) = d : c ++ concat s
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