%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcInstUtil]{Utilities for typechecking instance declarations}
The bits common to TcInstDcls and TcDeriv.
\begin{code}
-#include "HsVersions.h"
-
module TcInstUtil (
InstInfo(..),
- mkInstanceRelatedIds,
- buildInstanceEnvs
+ buildInstanceEnv,
+ classDataCon
) where
-IMP_Ubiq()
+#include "HsVersions.h"
-import HsSyn ( MonoBinds, Fake, InPat, Sig )
-import RnHsSyn ( SYN_IE(RenamedMonoBinds), RenamedSig(..),
- RenamedInstancePragmas(..) )
+import RnHsSyn ( RenamedMonoBinds, RenamedSig )
+import CmdLineOpts ( opt_AllowOverlappingInstances )
import TcMonad
-import Inst ( SYN_IE(InstanceMapper) )
-
+import TcEnv ( InstEnv, emptyInstEnv, addToInstEnv )
import Bag ( bagToList, Bag )
-import Class ( GenClass, SYN_IE(ClassInstEnv),
- classBigSig, SYN_IE(Class)
- )
-import CoreSyn ( GenCoreExpr(..), mkValLam, mkTyApp )
-import Id ( GenId, mkDictFunId, mkSysLocal, SYN_IE(Id) )
-import MatchEnv ( nullMEnv, insertMEnv )
+import Class ( Class )
+import Var ( TyVar, Id, idName )
import Maybes ( MaybeErr(..), mkLookupFunDef )
-import Name ( getSrcLoc, Name{--O only-} )
-import PprType ( GenClass, GenType, GenTyVar, pprParendType )
-import Pretty
-import SpecEnv ( SpecEnv, nullSpecEnv, addOneToSpecEnv )
+import Name ( getSrcLoc, nameModule, isLocallyDefined )
import SrcLoc ( SrcLoc )
-import Type ( mkSigmaTy, mkForAllTys, mkDictTy, mkTyVarTys,
- instantiateTy, matchTy, SYN_IE(ThetaType),
- SYN_IE(Type) )
-import TyVar ( GenTyVar, SYN_IE(TyVar) )
-import Unique ( Unique )
-import Util ( equivClasses, zipWithEqual, panic{-, pprTrace-}, Ord3(..) )
-
+import Type ( Type, ClassContext )
+import PprType ( pprConstraint )
+import Class ( classTyCon )
+import DataCon ( DataCon )
+import TyCon ( tyConDataCons )
+import Unique ( Unique, getUnique )
+import Util ( equivClassesByUniq )
import Outputable
\end{code}
= InstInfo
Class -- Class, k
[TyVar] -- Type variables, tvs
- Type -- The type at which the class is being instantiated
- ThetaType -- inst_decl_theta: the original context, c, from the
+ [Type] -- The types at which the class is being instantiated
+ ClassContext -- inst_decl_theta: the original context, c, from the
-- instance declaration. It constrains (some of)
-- the TyVars above
- ThetaType -- dfun_theta: the inst_decl_theta, plus one
- -- element for each superclass; the "Mark
- -- Jones optimisation"
Id -- The dfun id
RenamedMonoBinds -- Bindings, b
SrcLoc -- Source location assoc'd with this instance's defn
[RenamedSig] -- User pragmas recorded for generating specialised instances
\end{code}
+
%************************************************************************
%* *
\subsection{Creating instance related Ids}
%* *
%************************************************************************
-\begin{code}
-mkInstanceRelatedIds :: Name -- Name to use for the dict fun;
- -> Class
- -> [TyVar]
- -> Type
- -> ThetaType
- -> (Id, ThetaType)
-
-mkInstanceRelatedIds dfun_name clas inst_tyvars inst_ty inst_decl_theta
- = (dfun_id, dfun_theta)
- where
- (_, super_classes, _, _, _) = classBigSig clas
- super_class_theta = super_classes `zip` repeat inst_ty
-
- dfun_theta = case inst_decl_theta of
- [] -> [] -- If inst_decl_theta is empty, then we don't
- -- want to have any dict arguments, so that we can
- -- expose the constant methods.
-
- other -> inst_decl_theta ++ super_class_theta
- -- Otherwise we pass the superclass dictionaries to
- -- the dictionary function; the Mark Jones optimisation.
-
- dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_ty)
-
- dfun_id = mkDictFunId dfun_name dfun_ty clas inst_ty
-\end{code}
+A tiny function which doesn't belong anywhere else.
+It makes a nasty mutual-recursion knot if you put it in Class.
+\begin{code}
+classDataCon :: Class -> DataCon
+classDataCon clas = case tyConDataCons (classTyCon clas) of
+ (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr
+\end{code}
%************************************************************************
%* *
%************************************************************************
\begin{code}
-buildInstanceEnvs :: Bag InstInfo
- -> TcM s InstanceMapper
-
-buildInstanceEnvs info
- = let
- icmp :: InstInfo -> InstInfo -> TAG_
- (InstInfo c1 _ _ _ _ _ _ _ _) `icmp` (InstInfo c2 _ _ _ _ _ _ _ _)
- = c1 `cmp` c2
-
- info_by_class = equivClasses icmp (bagToList info)
- in
- mapTc buildInstanceEnv info_by_class `thenTc` \ inst_env_entries ->
- let
- class_lookup_fn = mkLookupFunDef (==) inst_env_entries nullMEnv
- in
- returnTc class_lookup_fn
-\end{code}
+buildInstanceEnv :: Bag InstInfo -> NF_TcM s InstEnv
-\begin{code}
-buildInstanceEnv :: [InstInfo] -- Non-empty, and all for same class
- -> TcM s (Class, ClassInstEnv)
-
-buildInstanceEnv inst_infos@((InstInfo clas _ _ _ _ _ _ _ _) : _)
- = foldlTc addClassInstance
- nullMEnv
- inst_infos `thenTc` \ class_inst_env ->
- returnTc (clas, class_inst_env)
+buildInstanceEnv info = foldrNF_Tc addClassInstance emptyInstEnv (bagToList info)
\end{code}
@addClassInstance@ adds the appropriate stuff to the @ClassInstEnv@
\begin{code}
addClassInstance
- :: ClassInstEnv
- -> InstInfo
- -> TcM s ClassInstEnv
+ :: InstInfo
+ -> InstEnv
+ -> NF_TcM s InstEnv
-addClassInstance class_inst_env
- (InstInfo clas inst_tyvars inst_ty _ _
+addClassInstance
+ (InstInfo clas inst_tyvars inst_tys _
dfun_id _ src_loc _)
+ inst_env
= -- Add the instance to the class's instance environment
- case insertMEnv matchTy class_inst_env inst_ty dfun_id of
- Failed (ty', dfun_id') -> recoverTc (returnTc class_inst_env) $
- dupInstFailure clas (inst_ty, src_loc)
- (ty', getSrcLoc dfun_id');
- Succeeded class_inst_env' -> returnTc class_inst_env'
-
-{- OLD STUFF FOR CONSTANT METHODS
-
- -- If there are any constant methods, then add them to
- -- the SpecEnv of each class op (ie selector)
- --
- -- Example. class Foo a where { op :: Baz b => a -> b; ... }
- -- instance Foo (p,q) where { op (x,y) = ... ; ... }
- --
- -- The class decl means that
- -- op :: forall a. Foo a => forall b. Baz b => a -> b
- --
- -- The constant method from the instance decl will be:
- -- op_Pair :: forall p q b. Baz b => (p,q) -> b
- --
- -- What we put in op's SpecEnv is
- -- (p,q) |--> (\d::Foo (p,q) -> op_Pair p q)
- --
- -- Here, [p,q] are the inst_tyvars, and d is a dict whose only
- -- purpose is to cancel with the dict to which op is applied.
- --
- -- NOTE THAT this correctly deals with the case where there are
- -- constant methods even though there are type variables in the
- -- instance declaration.
-
- tcGetUnique `thenNF_Tc` \ uniq ->
- let
- dict = mkSysLocal SLIT("dict_tpl") uniq (mkDictTy clas inst_ty) src_loc
- -- Slightly disgusting, but it's only a placeholder for
- -- a dictionary to be chucked away.
-
- op_spec_envs' | null const_meth_ids = op_spec_envs
- | otherwise = zipWithEqual "add_const_meth" add_const_meth op_spec_envs const_meth_ids
-
- add_const_meth (op,spec_env) meth_id
- = (op, case addOneToSpecEnv spec_env [inst_ty] rhs of
- Failed (tys', rhs') -> panic "TcInstDecls:add_const_meth"
- Succeeded spec_env' -> spec_env' )
- where
- rhs = mkValLam [dict] (mkTyApp (Var meth_id) (mkTyVarTys inst_tyvars))
- in
- returnTc (class_inst_env', op_spec_envs')
- END OF OLD STUFF -}
-
+ case addToInstEnv opt_AllowOverlappingInstances
+ inst_env clas inst_tyvars inst_tys dfun_id of
+ Failed (tys', dfun_id') -> addErrTc (dupInstErr clas (inst_tys, dfun_id)
+ (tys', dfun_id'))
+ `thenNF_Tc_`
+ returnNF_Tc inst_env
+
+ Succeeded inst_env' -> returnNF_Tc inst_env'
\end{code}
\begin{code}
-dupInstFailure clas info1@(ty1, locn1) info2@(ty2, locn2)
+dupInstErr clas info1@(tys1, dfun1) info2@(tys2, dfun2)
-- Overlapping/duplicate instances for given class; msg could be more glamourous
- = tcAddErrCtxt ctxt $
- failTc (\sty -> ptext SLIT("Duplicate or overlapping instance declarations"))
+ = hang (ptext SLIT("Duplicate or overlapping instance declarations"))
+ 4 (sep [ptext SLIT("for") <+> quotes (pprConstraint clas tys1),
+ nest 4 (sep [ppr_loc dfun1, ptext SLIT("and") <+> ppr_loc dfun2])])
where
- ctxt sty = sep [hsep [ptext SLIT("for"),
- pprQuote sty $ \ sty -> ppr sty clas <+> pprParendType sty ty1],
- nest 4 (sep [ptext SLIT("at") <+> ppr sty locn1,
- ptext SLIT("and") <+> ppr sty locn2])]
+ ppr_loc dfun
+ | isLocallyDefined dfun = ptext SLIT("defined at") <+> ppr (getSrcLoc dfun)
+ | otherwise = ptext SLIT("imported from module") <+> quotes (ppr (nameModule (idName dfun)))
\end{code}
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