import FamInstEnv
import TcDeriv
import TcEnv
-import RnEnv ( lookupImportedName )
+import RnEnv ( lookupGlobalOccRn )
import TcHsType
import TcUnify
import TcSimplify
import SrcLoc
import Util
import Outputable
-import Maybes
import Bag
import BasicTypes
import HscTypes
{-# INLINE [2] op1_i #-} -- From the instance decl bindings
op1_i, op2_i :: forall a. C a => forall b. Ix b => [a] -> b -> b
op1_i = /\a. \(d:C a).
- let local_op1 :: forall a. (C a, C [a])
- => forall b. Ix b => [a] -> b -> b
+ let this :: C [a]
+ this = df_i a d
-- Note [Subtle interaction of recursion and overlap]
+
+ local_op1 :: forall b. Ix b => [a] -> b -> b
local_op1 = <rhs>
-- Source code; run the type checker on this
-- NB: Type variable 'a' (but not 'b') is in scope in <rhs>
-- Note [Tricky type variable scoping]
- in local_op1 a d (df_i a d)
+ in local_op1 a d
op2_i = /\a \d:C a. $dmop2 [a] (df_i a d)
inline df_i in it, and that in turn means that (since it'll be a
loop-breaker because df_i isn't), op1_i will ironically never be
inlined. We need to fix this somehow -- perhaps allowing inlining
- of INLINE funcitons inside other INLINE functions.
+ of INLINE functions inside other INLINE functions.
Note [Subtle interaction of recursion and overlap]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
does the same thing; it shows up in module Fraction.hs
Conclusion: when typechecking the methods in a C [a] instance, we want
-to have C [a] available. That is why we have the strange local let in
-the definition of op1_i in the example above. We can typecheck the
-defintion of local_op1, and then supply the "this" argument via an
-explicit call to the dfun (which in turn will be inlined).
+to have C [a] available. That is why we have the strange local
+definition for 'this' in the definition of op1_i in the example above.
+We can typecheck the defintion of local_op1, and when doing tcSimplifyCheck
+we supply 'this' as a given dictionary. Only needed, though, if there
+are some type variales involved; otherwise there can be no overlap and
+none of this arises.
Note [Tricky type variable scoping]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
; let { (local_info,
at_tycons_s) = unzip local_info_tycons
- ; at_idx_tycon = concat at_tycons_s ++ idx_tycons
+ ; at_idx_tycons = concat at_tycons_s ++ idx_tycons
; clas_decls = filter (isClassDecl.unLoc) tycl_decls
- ; implicit_things = concatMap implicitTyThings at_idx_tycon
+ ; implicit_things = concatMap implicitTyThings at_idx_tycons
+ ; aux_binds = mkAuxBinds at_idx_tycons
}
-- (2) Add the tycons of indexed types and their implicit
-- tythings to the global environment
- ; tcExtendGlobalEnv (at_idx_tycon ++ implicit_things) $ do {
+ ; tcExtendGlobalEnv (at_idx_tycons ++ implicit_things) $ do {
-- (3) Instances from generic class declarations
; generic_inst_info <- getGenericInstances clas_decls
-- c) local family instance decls
; addInsts local_info $ do {
; addInsts generic_inst_info $ do {
- ; addFamInsts at_idx_tycon $ do {
+ ; addFamInsts at_idx_tycons $ do {
-- (4) Compute instances from "deriving" clauses;
-- This stuff computes a context for the derived instance
-- more errors still
; (deriv_inst_info, deriv_binds) <- tcDeriving tycl_decls inst_decls
deriv_decls
- ; addInsts deriv_inst_info $ do {
-
- ; gbl_env <- getGblEnv
+ ; gbl_env <- addInsts deriv_inst_info getGblEnv
; return (gbl_env,
generic_inst_info ++ deriv_inst_info ++ local_info,
- deriv_binds)
- }}}}}}
+ aux_binds `plusHsValBinds` deriv_binds)
+ }}}}}
where
-- Make sure that toplevel type instance are not for associated types.
-- !!!TODO: Need to perform this check for the TyThing of type functions,
; mapM_ (checkIndexes clas inst_tys) ats
}
- checkIndexes clas inst_tys (hsAT, ATyCon tycon) =
+ checkIndexes clas inst_tys (hsAT, ATyCon tycon)
-- !!!TODO: check that this does the Right Thing for indexed synonyms, too!
- checkIndexes' clas inst_tys hsAT
- (tyConTyVars tycon,
- snd . fromJust . tyConFamInst_maybe $ tycon)
+ = checkIndexes' clas inst_tys hsAT
+ (tyConTyVars tycon,
+ snd . fromJust . tyConFamInst_maybe $ tycon)
checkIndexes _ _ _ = panic "checkIndexes"
checkIndexes' clas (instTvs, instTys) hsAT (atTvs, atTys)
addErrCtxt (atInstCtxt atName) $
case find ((atName ==) . tyConName) (classATs clas) of
Nothing -> addErrTc $ badATErr clas atName -- not in this class
- Just atDecl ->
- case assocTyConArgPoss_maybe atDecl of
+ Just atycon ->
+ case assocTyConArgPoss_maybe atycon of
Nothing -> panic "checkIndexes': AT has no args poss?!?"
Just poss ->
-- which must be type variables; and (3) variables in AT and
-- instance head will be different `Name's even if their
-- source lexemes are identical.
+ --
+ -- e.g. class C a b c where
+ -- data D b a :: * -> * -- NB (1) b a, omits c
+ -- instance C [x] Bool Char where
+ -- data D Bool [x] v = MkD x [v] -- NB (2) v
+ -- -- NB (3) the x in 'instance C...' have differnt
+ -- -- Names to x's in 'data D...'
--
-- Re (1), `poss' contains a permutation vector to extract the
-- class parameters in the right order.
unionManyBags inst_binds_s
; tcl_env <- getLclEnv -- Default method Ids in here
; return (binds, tcl_env) }
+
+tcInstDecl2 :: InstInfo Name -> TcM (LHsBinds Id)
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds })
+ = recoverM (return emptyLHsBinds) $
+ setSrcSpan loc $
+ addErrCtxt (instDeclCtxt2 (idType dfun_id)) $
+ tc_inst_decl2 dfun_id ibinds
+ where
+ dfun_id = instanceDFunId ispec
+ loc = getSrcSpan dfun_id
\end{code}
\begin{code}
-tcInstDecl2 :: InstInfo Name -> TcM (LHsBinds Id)
+tc_inst_decl2 :: Id -> InstBindings Name -> TcM (LHsBinds Id)
-- Returns a binding for the dfun
------------------------
-- newtype N a = MkN (Tree [a]) deriving( Foo Int )
--
-- The newtype gives an FC axiom looking like
--- axiom CoN a :: N a :=: Tree [a]
+-- axiom CoN a :: N a ~ Tree [a]
-- (see Note [Newtype coercions] in TyCon for this unusual form of axiom)
--
-- So all need is to generate a binding looking like:
-- If there are no superclasses, matters are simpler, because we don't need the case
-- see Note [Newtype deriving superclasses] in TcDeriv.lhs
-tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived })
- = do { let dfun_id = instanceDFunId ispec
- rigid_info = InstSkol
+tc_inst_decl2 dfun_id (NewTypeDerived coi)
+ = do { let rigid_info = InstSkol
origin = SigOrigin rigid_info
inst_ty = idType dfun_id
- ; (tvs, theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty
+ ; (inst_tvs', theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty
-- inst_head_ty is a PredType
; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head_ty
(class_tyvars, sc_theta, _, _) = classBigSig cls
cls_tycon = classTyCon cls
sc_theta' = substTheta (zipOpenTvSubst class_tyvars cls_inst_tys) sc_theta
-
Just (initial_cls_inst_tys, last_ty) = snocView cls_inst_tys
- (nt_tycon, tc_args) = tcSplitTyConApp last_ty -- Can't fail
- rep_ty = newTyConInstRhs nt_tycon tc_args
- rep_pred = mkClassPred cls (initial_cls_inst_tys ++ [rep_ty])
- -- In our example, rep_pred is (Foo Int (Tree [a]))
- the_coercion = make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args
- -- Coercion of kind (Foo Int (Tree [a]) ~ Foo Int (N a)
+ (rep_ty, wrapper)
+ = case coi of
+ IdCo -> (last_ty, idHsWrapper)
+ ACo co -> (snd (coercionKind co), WpCast (mk_full_coercion co))
+
+ -----------------------
+ -- mk_full_coercion
+ -- The inst_head looks like (C s1 .. sm (T a1 .. ak))
+ -- But we want the coercion (C s1 .. sm (sym (CoT a1 .. ak)))
+ -- with kind (C s1 .. sm (T a1 .. ak) ~ C s1 .. sm <rep_ty>)
+ -- where rep_ty is the (eta-reduced) type rep of T
+ -- So we just replace T with CoT, and insert a 'sym'
+ -- NB: we know that k will be >= arity of CoT, because the latter fully eta-reduced
+
+ mk_full_coercion co = mkTyConApp cls_tycon
+ (initial_cls_inst_tys ++ [mkSymCoercion co])
+ -- Full coercion : (Foo Int (Tree [a]) ~ Foo Int (N a)
+
+ rep_pred = mkClassPred cls (initial_cls_inst_tys ++ [rep_ty])
+ -- In our example, rep_pred is (Foo Int (Tree [a]))
- ; inst_loc <- getInstLoc origin
; sc_loc <- getInstLoc InstScOrigin
- ; dfun_dicts <- newDictBndrs inst_loc theta
; sc_dicts <- newDictBndrs sc_loc sc_theta'
- ; this_dict <- newDictBndr inst_loc (mkClassPred cls cls_inst_tys)
+ ; inst_loc <- getInstLoc origin
+ ; dfun_dicts <- newDictBndrs inst_loc theta
; rep_dict <- newDictBndr inst_loc rep_pred
+ ; this_dict <- newDictBndr inst_loc (mkClassPred cls cls_inst_tys)
-- Figure out bindings for the superclass context from dfun_dicts
-- Don't include this_dict in the 'givens', else
- -- wanted_sc_insts get bound by just selecting from this_dict!!
+ -- sc_dicts get bound by just selecting from this_dict!!
; sc_binds <- addErrCtxt superClassCtxt $
- tcSimplifySuperClasses inst_loc dfun_dicts (rep_dict:sc_dicts)
+ tcSimplifySuperClasses inst_loc this_dict dfun_dicts
+ (rep_dict:sc_dicts)
- ; let coerced_rep_dict = wrapId the_coercion (instToId rep_dict)
+ -- It's possible that the superclass stuff might unified something
+ -- in the envt with one of the clas_tyvars
+ ; checkSigTyVars inst_tvs'
+
+ ; let coerced_rep_dict = wrapId wrapper (instToId rep_dict)
; body <- make_body cls_tycon cls_inst_tys sc_dicts coerced_rep_dict
; let dict_bind = noLoc $ VarBind (instToId this_dict) (noLoc body)
; return (unitBag $ noLoc $
- AbsBinds tvs (map instToVar dfun_dicts)
- [(tvs, dfun_id, instToId this_dict, [])]
+ AbsBinds inst_tvs' (map instToVar dfun_dicts)
+ [(inst_tvs', dfun_id, instToId this_dict, [])]
(dict_bind `consBag` sc_binds)) }
where
-----------------------
- -- make_coercion
- -- The inst_head looks like (C s1 .. sm (T a1 .. ak))
- -- But we want the coercion (C s1 .. sm (sym (CoT a1 .. ak)))
- -- with kind (C s1 .. sm (T a1 .. ak) :=: C s1 .. sm <rep_ty>)
- -- where rep_ty is the (eta-reduced) type rep of T
- -- So we just replace T with CoT, and insert a 'sym'
- -- NB: we know that k will be >= arity of CoT, because the latter fully eta-reduced
-
- make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args
- | Just co_con <- newTyConCo_maybe nt_tycon
- , let co = mkSymCoercion (mkTyConApp co_con tc_args)
- = WpCast (mkTyConApp cls_tycon (initial_cls_inst_tys ++ [co]))
- | otherwise -- The newtype is transparent; no need for a cast
- = idHsWrapper
-
- -----------------------
-- (make_body C tys scs coreced_rep_dict)
-- returns
-- (case coerced_rep_dict of { C _ ops -> C scs ops })
------------------------
-- Ordinary instances
-tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags })
- = let
- dfun_id = instanceDFunId ispec
- rigid_info = InstSkol
- inst_ty = idType dfun_id
- loc = getSrcSpan dfun_id
- in
- -- Prime error recovery
- recoverM (return emptyLHsBinds) $
- setSrcSpan loc $
- addErrCtxt (instDeclCtxt2 (idType dfun_id)) $ do
+tc_inst_decl2 dfun_id (VanillaInst monobinds uprags)
+ = do { let rigid_info = InstSkol
+ inst_ty = idType dfun_id
-- Instantiate the instance decl with skolem constants
- (inst_tyvars', dfun_theta', inst_head') <- tcSkolSigType rigid_info inst_ty
+ ; (inst_tyvars', dfun_theta', inst_head') <- tcSkolSigType rigid_info inst_ty
-- These inst_tyvars' scope over the 'where' part
-- Those tyvars are inside the dfun_id's type, which is a bit
-- bizarre, but OK so long as you realise it!
- let
- (clas, inst_tys') = tcSplitDFunHead inst_head'
- (class_tyvars, sc_theta, _, op_items) = classBigSig clas
+ ; let
+ (clas, inst_tys') = tcSplitDFunHead inst_head'
+ (class_tyvars, sc_theta, _, op_items) = classBigSig clas
- -- Instantiate the super-class context with inst_tys
- sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta
- (eq_sc_theta',dict_sc_theta') = partition isEqPred sc_theta'
- origin = SigOrigin rigid_info
- (eq_dfun_theta',dict_dfun_theta') = partition isEqPred dfun_theta'
+ -- Instantiate the super-class context with inst_tys
+ sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta
+ origin = SigOrigin rigid_info
-- Create dictionary Ids from the specified instance contexts.
- sc_loc <- getInstLoc InstScOrigin
- sc_dicts <- newDictBndrs sc_loc dict_sc_theta'
- inst_loc <- getInstLoc origin
- sc_covars <- mkMetaCoVars eq_sc_theta'
- wanted_sc_eqs <- mkEqInsts eq_sc_theta' (map mkWantedCo sc_covars)
- dfun_covars <- mkCoVars eq_dfun_theta'
- dfun_eqs <- mkEqInsts eq_dfun_theta' (map mkGivenCo $ mkTyVarTys dfun_covars)
- dfun_dicts <- newDictBndrs inst_loc dict_dfun_theta'
- this_dict <- newDictBndr inst_loc (mkClassPred clas inst_tys')
+ ; sc_loc <- getInstLoc InstScOrigin
+ ; sc_dicts <- newDictOccs sc_loc sc_theta' -- These are wanted
+ ; inst_loc <- getInstLoc origin
+ ; dfun_dicts <- newDictBndrs inst_loc dfun_theta' -- Includes equalities
+ ; this_dict <- newDictBndr inst_loc (mkClassPred clas inst_tys')
+
-- Default-method Ids may be mentioned in synthesised RHSs,
-- but they'll already be in the environment.
-- Typecheck the methods
- let -- These insts are in scope; quite a few, eh?
- dfun_insts = dfun_eqs ++ dfun_dicts
- wanted_sc_insts = wanted_sc_eqs ++ sc_dicts
- this_dict_id = instToId this_dict
- sc_dict_ids = map instToId sc_dicts
- dfun_dict_ids = map instToId dfun_dicts
- prag_fn = mkPragFun uprags
- tc_meth = tcInstanceMethod loc clas inst_tyvars'
- (dfun_covars ++ dfun_dict_ids)
- dfun_theta' inst_tys'
- this_dict_id dfun_id
- prag_fn monobinds
- (meth_exprs, meth_binds) <- mapAndUnzipM tc_meth op_items
-
- -- Figure out bindings for the superclass context
- -- Don't include this_dict in the 'givens', else
- -- wanted_sc_insts get bound by just selecting from this_dict!!
- sc_binds <- addErrCtxt superClassCtxt $
- tcSimplifySuperClasses inst_loc dfun_insts
- wanted_sc_insts
+ ; let this_dict_id = instToId this_dict
+ dfun_lam_vars = map instToVar dfun_dicts -- Includes equalities
+ prag_fn = mkPragFun uprags
+ loc = getSrcSpan dfun_id
+ tc_meth = tcInstanceMethod loc clas inst_tyvars'
+ dfun_dicts
+ dfun_theta' inst_tys'
+ this_dict dfun_id
+ prag_fn monobinds
+ ; (meth_exprs, meth_binds) <- tcExtendTyVarEnv inst_tyvars' $
+ mapAndUnzipM tc_meth op_items
+
+ -- Figure out bindings for the superclass context
+ -- Don't include this_dict in the 'givens', else
+ -- sc_dicts get bound by just selecting from this_dict!!
+ ; sc_binds <- addErrCtxt superClassCtxt $
+ tcSimplifySuperClasses inst_loc this_dict dfun_dicts sc_dicts
-- Note [Recursive superclasses]
- -- It's possible that the superclass stuff might unified one
- -- of the inst_tyavars' with something in the envt
- checkSigTyVars inst_tyvars'
-
- -- Deal with 'SPECIALISE instance' pragmas
- prags <- tcPrags dfun_id (filter isSpecInstLSig uprags)
-
- -- Create the result bindings
- let
- dict_constr = classDataCon clas
- inline_prag | null dfun_insts = []
- | otherwise = [L loc (InlinePrag (Inline AlwaysActive True))]
- -- Always inline the dfun; this is an experimental decision
- -- because it makes a big performance difference sometimes.
- -- Often it means we can do the method selection, and then
- -- inline the method as well. Marcin's idea; see comments below.
- --
- -- BUT: don't inline it if it's a constant dictionary;
- -- we'll get all the benefit without inlining, and we get
- -- a **lot** of code duplication if we inline it
- --
- -- See Note [Inline dfuns] below
-
- dict_rhs = mkHsConApp dict_constr (inst_tys' ++ mkTyVarTys sc_covars)
- (map HsVar sc_dict_ids ++ meth_exprs)
- -- We don't produce a binding for the dict_constr; instead we
- -- rely on the simplifier to unfold this saturated application
- -- We do this rather than generate an HsCon directly, because
- -- it means that the special cases (e.g. dictionary with only one
- -- member) are dealt with by the common MkId.mkDataConWrapId code rather
- -- than needing to be repeated here.
-
- dict_bind = noLoc (VarBind this_dict_id dict_rhs)
-
- main_bind = noLoc $ AbsBinds
- (inst_tyvars' ++ dfun_covars)
- dfun_dict_ids
- [(inst_tyvars' ++ dfun_covars, dfun_id, this_dict_id, inline_prag ++ prags)]
- (dict_bind `consBag` sc_binds)
-
- showLIE (text "instance")
- return (main_bind `consBag` unionManyBags meth_binds)
-
-mkCoVars :: [PredType] -> TcM [TyVar]
-mkCoVars = newCoVars . map unEqPred
- where
- unEqPred (EqPred ty1 ty2) = (ty1, ty2)
- unEqPred _ = panic "TcInstDcls.mkCoVars"
-
-mkMetaCoVars :: [PredType] -> TcM [TyVar]
-mkMetaCoVars = mapM eqPredToCoVar
- where
- eqPredToCoVar (EqPred ty1 ty2) = newMetaCoVar ty1 ty2
- eqPredToCoVar _ = panic "TcInstDcls.mkMetaCoVars"
+ -- It's possible that the superclass stuff might unified something
+ -- in the envt with one of the inst_tyvars'
+ ; checkSigTyVars inst_tyvars'
+
+ -- Deal with 'SPECIALISE instance' pragmas
+ ; prags <- tcPrags dfun_id (filter isSpecInstLSig uprags)
+
+ -- Create the result bindings
+ ; let dict_constr = classDataCon clas
+ inline_prag | null dfun_dicts = []
+ | otherwise = [L loc (InlinePrag (alwaysInlineSpec FunLike))]
+ -- Always inline the dfun; this is an experimental decision
+ -- because it makes a big performance difference sometimes.
+ -- Often it means we can do the method selection, and then
+ -- inline the method as well. Marcin's idea; see comments below.
+ --
+ -- BUT: don't inline it if it's a constant dictionary;
+ -- we'll get all the benefit without inlining, and we get
+ -- a **lot** of code duplication if we inline it
+ --
+ -- See Note [Inline dfuns] below
+
+ sc_dict_vars = map instToVar sc_dicts
+ dict_bind = L loc (VarBind this_dict_id dict_rhs)
+ dict_rhs = foldl (\ f a -> L loc (HsApp f (L loc a))) inst_constr meth_exprs
+ inst_constr = L loc $ wrapId (mkWpApps sc_dict_vars <.> mkWpTyApps inst_tys')
+ (dataConWrapId dict_constr)
+ -- We don't produce a binding for the dict_constr; instead we
+ -- rely on the simplifier to unfold this saturated application
+ -- We do this rather than generate an HsCon directly, because
+ -- it means that the special cases (e.g. dictionary with only one
+ -- member) are dealt with by the common MkId.mkDataConWrapId code rather
+ -- than needing to be repeated here.
+
+
+ main_bind = noLoc $ AbsBinds
+ inst_tyvars'
+ dfun_lam_vars
+ [(inst_tyvars', dfun_id, this_dict_id, inline_prag ++ prags)]
+ (dict_bind `consBag` sc_binds)
+
+ ; showLIE (text "instance")
+ ; return (main_bind `consBag` unionManyBags meth_binds) }
\end{code}
Note [Recursive superclasses]
- Use tcValBinds to do the checking
\begin{code}
-tcInstanceMethod :: SrcSpan -> Class -> [TcTyVar] -> [Var]
+tcInstanceMethod :: SrcSpan -> Class -> [TcTyVar] -> [Inst]
-> TcThetaType -> [TcType]
- -> Id -> Id
+ -> Inst -> Id
-> TcPragFun -> LHsBinds Name
-> (Id, DefMeth)
-> TcM (HsExpr Id, LHsBinds Id)
-- The returned inst_meth_ids all have types starting
-- forall tvs. theta => ...
-tcInstanceMethod loc clas tyvars dfun_lam_vars theta inst_tys
- this_dict_id dfun_id
- prag_fn binds_in (sel_id, dm_info)
- = do { uniq <- newUnique
- ; let local_meth_name = mkInternalName uniq sel_occ loc -- Same OccName
- tc_body = tcInstanceMethodBody clas tyvars dfun_lam_vars theta inst_tys
- this_dict_id dfun_id sel_id
- prags local_meth_name
+tcInstanceMethod loc clas tyvars dfun_dicts theta inst_tys
+ this_dict dfun_id prag_fn binds_in (sel_id, dm_info)
+ = do { cloned_this <- cloneDict this_dict
+ -- Need to clone the dict in case it is floated out, and
+ -- then clashes with its friends
+ ; uniq1 <- newUnique
+ ; let local_meth_name = mkInternalName uniq1 sel_occ loc -- Same OccName
+ this_dict_bind = L loc $ VarBind (instToId cloned_this) $
+ L loc $ wrapId meth_wrapper dfun_id
+ mb_this_bind | null tyvars = Nothing
+ | otherwise = Just (cloned_this, this_dict_bind)
+ -- Only need the this_dict stuff if there are type variables
+ -- involved; otherwise overlap is not possible
+ -- See Note [Subtle interaction of recursion and overlap]
+
+ tc_body rn_bind = do { (meth_id, tc_binds) <- tcInstanceMethodBody
+ InstSkol clas tyvars dfun_dicts theta inst_tys
+ mb_this_bind sel_id
+ local_meth_name
+ meth_sig_fn meth_prag_fn rn_bind
+ ; return (wrapId meth_wrapper meth_id, tc_binds) }
; case (findMethodBind sel_name local_meth_name binds_in, dm_info) of
-- There is a user-supplied method binding, so use it
{ -- Build the typechecked version directly,
-- without calling typecheck_method;
-- see Note [Default methods in instances]
- dm_name <- lookupImportedName (mkDefMethRdrName sel_name)
+ dm_name <- lookupGlobalOccRn (mkDefMethRdrName sel_name)
-- Might not be imported, but will be an OrigName
; dm_id <- tcLookupId dm_name
; return (wrapId dm_wrapper dm_id, emptyBag) } }
where
sel_name = idName sel_id
sel_occ = nameOccName sel_name
- prags = prag_fn sel_name
-
- error_rhs = HsApp (mkLHsWrap (WpTyApp meth_tau) error_id) error_msg
- meth_tau = funResultTy (applyTys (idType sel_id) inst_tys)
- error_id = L loc (HsVar nO_METHOD_BINDING_ERROR_ID)
+ this_dict_id = instToId this_dict
+
+ meth_prag_fn _ = prag_fn sel_name
+ meth_sig_fn _ = Just [] -- The 'Just' says "yes, there's a type sig"
+ -- But there are no scoped type variables from local_method_id
+ -- Only the ones from the instance decl itself, which are already
+ -- in scope. Example:
+ -- class C a where { op :: forall b. Eq b => ... }
+ -- instance C [c] where { op = <rhs> }
+ -- In <rhs>, 'c' is scope but 'b' is not!
+
+ error_rhs = HsApp error_fun error_msg
+ error_fun = L loc $ wrapId (WpTyApp meth_tau) nO_METHOD_BINDING_ERROR_ID
error_msg = L loc (HsLit (HsStringPrim (mkFastString error_string)))
+ meth_tau = funResultTy (applyTys (idType sel_id) inst_tys)
error_string = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
dm_wrapper = WpApp this_dict_id <.> mkWpTyApps inst_tys
omitted_meth_warn = ptext (sLit "No explicit method nor default method for")
<+> quotes (ppr sel_id)
----------------
-tcInstanceMethodBody :: Class -> [TcTyVar] -> [Var]
- -> TcThetaType -> [TcType]
- -> Id -> Id -> Id
- -> [LSig Name] -> Name -> LHsBind Name
- -> TcM (HsExpr Id, LHsBinds Id)
-tcInstanceMethodBody clas tyvars dfun_lam_vars theta inst_tys
- this_dict_id dfun_id sel_id
- prags local_meth_name bind@(L loc _)
- = do { uniq <- newUnique
- ; let (sel_tyvars,sel_rho) = tcSplitForAllTys (idType sel_id)
- rho_ty = ASSERT( length sel_tyvars == length inst_tys )
- substTyWith sel_tyvars inst_tys sel_rho
-
- (first_pred, meth_tau) = tcSplitPredFunTy_maybe rho_ty
- `orElse` pprPanic "tcInstanceMethod" (ppr sel_id)
-
- meth_name = mkInternalName uniq (getOccName local_meth_name) loc
- meth_ty = mkSigmaTy tyvars theta meth_tau
- meth_id = mkLocalId meth_name meth_ty
-
- local_meth_ty = mkSigmaTy tyvars (theta ++ [first_pred]) meth_tau
- local_meth_id = mkLocalId local_meth_name local_meth_ty
-
- tv_names = map tyVarName tyvars
-
- -- The first predicate should be of form (C a b)
- -- where C is the class in question
- ; MASSERT( case getClassPredTys_maybe first_pred of
- { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } )
-
- ; local_meth_bind <- tcMethodBind tv_names prags local_meth_id bind
-
- ; let full_bind = unitBag $ L loc $
- VarBind meth_id $ L loc $
- mkHsWrap (mkWpTyLams tyvars <.> mkWpLams dfun_lam_vars) $
- HsLet (HsValBinds (ValBindsOut [(NonRecursive, local_meth_bind)] [])) $ L loc $
- mkHsWrap (WpLet this_dict_bind <.> WpApp this_dict_id) $
- wrapId meth_wrapper local_meth_id
- this_dict_bind = unitBag $ L loc $
- VarBind this_dict_id $ L loc $
- wrapId meth_wrapper dfun_id
-
- ; return (wrapId meth_wrapper meth_id, full_bind) }
- where
+ dfun_lam_vars = map instToVar dfun_dicts
meth_wrapper = mkWpApps dfun_lam_vars <.> mkWpTyApps (mkTyVarTys tyvars)
+
wrapId :: HsWrapper -> id -> HsExpr id
wrapId wrapper id = mkHsWrap wrapper (HsVar id)
\end{code}
wrongATArgErr :: Type -> Type -> SDoc
wrongATArgErr ty instTy =
sep [ ptext (sLit "Type indexes must match class instance head")
- , ptext (sLit "Found") <+> ppr ty <+> ptext (sLit "but expected") <+>
- ppr instTy
+ , ptext (sLit "Found") <+> quotes (ppr ty)
+ <+> ptext (sLit "but expected") <+> quotes (ppr instTy)
]
\end{code}