import HscTypes ( DFunId )
import BasicTypes ( NewOrData(..) )
-import Class ( className, classKey, classTyVars, classSCTheta, Class )
+import Class ( className, classArity, classKey, classTyVars, classSCTheta, Class )
import Subst ( mkTyVarSubst, substTheta )
import ErrUtils ( dumpIfSet_dyn )
import MkId ( mkDictFunId )
-import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon )
+import DataCon ( dataConRepArgTys, dataConOrigArgTys, isNullaryDataCon, isExistentialDataCon )
import Maybes ( maybeToBool, catMaybes )
import Name ( Name, getSrcLoc, nameUnique )
import NameSet
import RdrName ( RdrName )
-import TyCon ( tyConTyVars, tyConDataCons, tyConArity, newTyConRep,
+import TyCon ( tyConTyVars, tyConDataCons, tyConArity,
tyConTheta, maybeTyConSingleCon, isDataTyCon,
isEnumerationTyCon, isRecursiveTyCon, TyCon
)
import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
- tcEqTypes, mkAppTys )
-import Type ( splitAppTys )
+ tcEqTypes, tcSplitAppTys, mkAppTys )
import Var ( TyVar, tyVarKind )
import VarSet ( mkVarSet, subVarSet )
import PrelNames
constraints = extra_constraints ++
[ mkClassPred clas [arg_ty]
| data_con <- tyConDataCons tycon,
- arg_ty <- dataConRepArgTys data_con,
+ arg_ty <- dataConRepArgTys data_con, -- dataConOrigArgTys???
-- Use the same type variables
-- as the type constructor,
-- hence no need to instantiate
= doptM Opt_GlasgowExts `thenM` \ gla_exts ->
if can_derive_via_isomorphism && (gla_exts || standard_instance) then
-- Go ahead and use the isomorphism
+ traceTc (text "newtype deriving:" <+> ppr tycon <+> ppr rep_tys) `thenM_`
new_dfun_name clas tycon `thenM` \ dfun_name ->
returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name,
iBinds = NewTypeDerived rep_tys }))
-- Want to drop 1 arg from (T s a) and (ST s a)
-- to get instance Monad (ST s) => Monad (T s)
- (tyvars, rep_ty) = newTyConRep tycon
- (rep_fn, rep_ty_args) = splitAppTys rep_ty
+ -- Note [newtype representation]
+ -- We must not use newTyConRep to get the representation
+ -- type, because that looks through all intermediate newtypes
+ -- To get the RHS of *this* newtype, just look at the data
+ -- constructor. For example
+ -- newtype B = MkB Int
+ -- newtype A = MkA B deriving( Num )
+ -- We want the Num instance of B, *not* the Num instance of Int,
+ -- when making the Num instance of A!
+ tyvars = tyConTyVars tycon
+ rep_ty = head (dataConOrigArgTys (head (tyConDataCons tycon)))
+ (rep_fn, rep_ty_args) = tcSplitAppTys rep_ty
n_tyvars_to_keep = tyConArity tycon - n_args_to_drop
tyvars_to_drop = drop n_tyvars_to_keep tyvars
can_derive_via_isomorphism
= not (clas `hasKey` readClassKey) -- Never derive Read,Show this way
&& not (clas `hasKey` showClassKey)
+ && length tys + 1 == classArity clas -- Well kinded;
+ -- eg not: newtype T ... deriving( ST )
+ -- because ST needs *2* type params
&& n_tyvars_to_keep >= 0 -- Well kinded;
-- eg not: newtype T = T Int deriving( Monad )
&& n_args_to_keep >= 0 -- Well kinded:
cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep
(vcat [ptext SLIT("too hard for cunning newtype deriving"),
- ppr n_tyvars_to_keep,
- ppr n_args_to_keep,
- ppr eta_ok,
+ ptext SLIT("debug info:") <+> ppr n_tyvars_to_keep <+>
+ ppr n_args_to_keep <+> ppr eta_ok <+>
ppr (isRecursiveTyCon tycon)
])
------------------------------------------------------------------
chk_out :: Class -> TyCon -> [TcType] -> Maybe SDoc
chk_out clas tycon tys
- | notNull tys = Just non_std_why
+ | notNull tys = Just ty_args_why
| not (getUnique clas `elem` derivableClassKeys) = Just non_std_why
| clas `hasKey` enumClassKey && not is_enumeration = Just nullary_why
| clas `hasKey` boundedClassKey && not is_enumeration_or_single = Just single_nullary_why
is_single_con = maybeToBool (maybeTyConSingleCon tycon)
is_enumeration_or_single = is_enumeration || is_single_con
- single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected")
- nullary_why = ptext SLIT("data type with all nullary constructors expected")
- no_cons_why = ptext SLIT("type has no data constructors")
- non_std_why = ptext SLIT("not a derivable class")
- existential_why = ptext SLIT("it has existentially-quantified constructor(s)")
+ single_nullary_why = ptext SLIT("one constructor data type or type with all nullary constructors expected")
+ nullary_why = quotes (ppr tycon) <+> ptext SLIT("has non-nullary constructors")
+ no_cons_why = quotes (ppr tycon) <+> ptext SLIT("has no data constructors")
+ ty_args_why = quotes (ppr pred) <+> ptext SLIT("is not a class")
+ non_std_why = quotes (ppr clas) <+> ptext SLIT("is not a derivable class")
+ existential_why = quotes (ppr tycon) <+> ptext SLIT("has existentially-quantified constructor(s)")
+
+ pred = mkClassPred clas tys
new_dfun_name clas tycon -- Just a simple wrapper
= newDFunName clas [mkTyConApp tycon []] (getSrcLoc tycon)
projects / ghc-hetmet.git / blobdiff