\section[TcClassDcl]{Typechecking class declarations}
\begin{code}
-module TcClassDcl ( tcClassDecl1, checkValidClass, tcClassDecls2,
- tcMethodBind, badMethodErr
+module TcClassDcl ( tcClassDecl1, tcClassDecls2,
+ tcMethodBind, mkMethodBind, badMethodErr
) where
#include "HsVersions.h"
import HsSyn ( TyClDecl(..), Sig(..), MonoBinds(..),
- HsExpr(..), HsLit(..),
+ HsExpr(..), HsLit(..), InPat(WildPatIn),
mkSimpleMatch, andMonoBinds, andMonoBindList,
- isClassOpSig, isPragSig,
+ isClassOpSig, isPragSig,
getClassDeclSysNames, placeHolderType
)
-import BasicTypes ( TopLevelFlag(..), RecFlag(..), StrictnessMark(..) )
+import BasicTypes ( RecFlag(..), StrictnessMark(..) )
import RnHsSyn ( RenamedTyClDecl,
RenamedClassOpSig, RenamedMonoBinds,
- RenamedSig, maybeGenericMatch
+ maybeGenericMatch
)
import TcHsSyn ( TcMonoBinds )
import Inst ( Inst, InstOrigin(..), LIE, emptyLIE, plusLIE, plusLIEs,
instToId, newDicts, newMethod )
-import TcEnv ( RecTcEnv, TyThingDetails(..), tcAddImportedIdInfo,
- tcLookupClass, tcExtendTyVarEnvForMeths, tcExtendGlobalTyVars,
- tcExtendLocalValEnv, tcExtendTyVarEnv
+import TcEnv ( TyThingDetails(..),
+ tcLookupClass, tcExtendTyVarEnv2,
+ tcExtendTyVarEnv
)
-import TcBinds ( tcBindWithSigs, tcSpecSigs )
-import TcMonoType ( tcHsType, tcHsTheta, checkSigTyVars, sigCtxt, mkTcSig )
-import TcSimplify ( tcSimplifyCheck, bindInstsOfLocalFuns )
-import TcMType ( tcInstTyVars, checkValidTheta, checkValidType, SourceTyCtxt(..), UserTypeCtxt(..) )
-import TcType ( Type, mkSigmaTy, mkTyVarTys, mkPredTys, mkClassPred,
- tcIsTyVarTy, tcSplitTyConApp_maybe, tcSplitSigmaTy
+import TcBinds ( tcMonoBinds )
+import TcMonoType ( TcSigInfo(..), tcHsType, tcHsTheta, mkTcSig )
+import TcSimplify ( tcSimplifyCheck )
+import TcUnify ( checkSigTyVars, sigCtxt )
+import TcMType ( tcInstTyVars )
+import TcType ( Type, TyVarDetails(..), TcType, TcThetaType, TcTyVar,
+ mkTyVarTys, mkPredTys, mkClassPred, tcSplitSigmaTy, tcSplitFunTys,
+ tcIsTyVarTy, tcSplitTyConApp_maybe
)
import TcMonad
-import Generics ( mkGenericRhs, validGenericMethodType )
+import Generics ( mkGenericRhs )
import PrelInfo ( nO_METHOD_BINDING_ERROR_ID )
-import Class ( classTyVars, classBigSig, classTyCon, className,
+import Class ( classTyVars, classBigSig, classTyCon,
Class, ClassOpItem, DefMeth (..) )
+import TyCon ( tyConGenInfo )
import MkId ( mkDictSelId, mkDataConId, mkDataConWrapId, mkDefaultMethodId )
import DataCon ( mkDataCon )
-import Id ( idType, idName )
+import Id ( Id, idType, idName, setIdLocalExported )
import Module ( Module )
import Name ( Name, NamedThing(..) )
import NameEnv ( NameEnv, lookupNameEnv, emptyNameEnv, unitNameEnv, plusNameEnv )
import NameSet ( emptyNameSet )
import Outputable
import Var ( TyVar )
-import VarSet ( mkVarSet, emptyVarSet )
import CmdLineOpts
+import UnicodeUtil ( stringToUtf8 )
import ErrUtils ( dumpIfSet )
-import Util ( count )
-import Maybes ( seqMaybe, maybeToBool )
+import Util ( count, lengthIs, equalLength )
+import Maybes ( seqMaybe )
+import Maybe ( isJust )
+import FastString
\end{code}
\begin{code}
-tcClassDecl1 :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
-tcClassDecl1 rec_env
- (ClassDecl {tcdCtxt = context, tcdName = class_name,
+tcClassDecl1 :: RenamedTyClDecl -> TcM (Name, TyThingDetails)
+tcClassDecl1 (ClassDecl {tcdCtxt = context, tcdName = class_name,
tcdTyVars = tyvar_names, tcdFDs = fundeps,
tcdSigs = class_sigs, tcdMeths = def_methods,
tcdSysNames = sys_names, tcdLoc = src_loc})
-- The renamer has already checked that the context mentions
-- only the type variable of the class decl.
-- Context is already kind-checked
- ASSERT( length context == length sc_sel_names )
- tcHsTheta context `thenTc` \ sc_theta ->
+ ASSERT( equalLength context sc_sel_names )
+ tcHsTheta context `thenTc` \ sc_theta ->
-- CHECK THE CLASS SIGNATURES,
- mapTc (tcClassSig rec_env clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
+ mapTc (tcClassSig clas tyvars mb_dm_env) op_sigs `thenTc` \ sig_stuff ->
-- MAKE THE CLASS DETAILS
let
returnTc (unitNameEnv op all_generic)
where
- n_generic = count (maybeToBool . maybeGenericMatch) matches
+ n_generic = count (isJust . maybeGenericMatch) matches
none_generic = n_generic == 0
- all_generic = n_generic == length matches
+ all_generic = matches `lengthIs` n_generic
\end{code}
\begin{code}
-tcClassSig :: RecTcEnv -- Knot tying only!
- -> Class -- ...ditto...
+tcClassSig :: Class -- ...ditto...
-> [TyVar] -- The class type variable, used for error check only
- -> Maybe (NameEnv Bool) -- Info about default methods
+ -> Maybe (NameEnv Bool) -- Info about default methods;
+ -- Nothing => imported class defn with no method binds
-> RenamedClassOpSig
-> TcM (Type, -- Type of the method
ClassOpItem) -- Selector Id, default-method Id, True if explicit default binding
-- so we distinguish them in checkDefaultBinds, and pass this knowledge in the
-- Class.DefMeth data structure.
-tcClassSig unf_env clas clas_tyvars maybe_dm_env
+tcClassSig clas clas_tyvars maybe_dm_env
(ClassOpSig op_name sig_dm op_ty src_loc)
= tcAddSrcLoc src_loc $
let
theta = [mkClassPred clas (mkTyVarTys clas_tyvars)]
- global_ty = mkSigmaTy clas_tyvars theta local_ty
- -- The default method's type should really come from the
- -- iface file, since it could be usage-generalised, but this
- -- requires altering the mess of knots in TcModule and I'm
- -- too scared to do that. Instead, I have disabled generalisation
- -- of types of default methods (and dict funs) by annotating them
- -- TyGenNever (in MkId). Ugh! KSW 1999-09.
-- Build the selector id and default method id
sel_id = mkDictSelId op_name clas
- dm_id = mkDefaultMethodId dm_name global_ty
DefMeth dm_name = sig_dm
dm_info = case maybe_dm_env of
- Nothing -> iface_dm_info
+ Nothing -> sig_dm
Just dm_env -> mk_src_dm_info dm_env
- iface_dm_info = case sig_dm of
- NoDefMeth -> NoDefMeth
- GenDefMeth -> GenDefMeth
- DefMeth dm_name -> DefMeth (tcAddImportedIdInfo unf_env dm_id)
-
mk_src_dm_info dm_env = case lookupNameEnv dm_env op_name of
Nothing -> NoDefMeth
Just True -> GenDefMeth
- Just False -> DefMeth dm_id
+ Just False -> DefMeth dm_name
in
returnTc (local_ty, (sel_id, dm_info))
\end{code}
-checkValidClass is called once the mutually-recursive knot has been
-tied, so we can look at things freely.
-
-\begin{code}
-checkValidClass :: Class -> TcM ()
-checkValidClass cls
- = -- CHECK ARITY 1 FOR HASKELL 1.4
- doptsTc Opt_GlasgowExts `thenTc` \ gla_exts ->
-
- -- Check that the class is unary, unless GlaExs
- checkTc (gla_exts || unary)
- (classArityErr cls) `thenTc_`
-
- -- Check the super-classes
- checkValidTheta (ClassSCCtxt (className cls)) theta `thenTc_`
-
- -- Check the class operations
- mapTc_ check_op op_stuff `thenTc_`
-
- -- Check that if the class has generic methods, then the
- -- class has only one parameter. We can't do generic
- -- multi-parameter type classes!
- checkTc (unary || no_generics) (genericMultiParamErr cls)
-
- where
- (tyvars, theta, sel_ids, op_stuff) = classBigSig cls
- unary = length tyvars == 1
- no_generics = null [() | (_, GenDefMeth) <- op_stuff]
-
- check_op (sel_id, dm)
- = checkValidTheta SigmaCtxt (tail theta) `thenTc_`
- -- The 'tail' removes the initial (C a) from the
- -- class itself, leaving just the method type
-
- checkValidType (FunSigCtxt op_name) tau `thenTc_`
-
- -- Check that for a generic method, the type of
- -- the method is sufficiently simple
- checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
- (badGenericMethodType op_name op_ty)
- where
- op_name = idName sel_id
- op_ty = idType sel_id
- (_,theta,tau) = tcSplitSigmaTy op_ty
-\end{code}
-
%************************************************************************
%* *
each local class decl.
\begin{code}
-tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds)
+tcClassDecls2 :: Module -> [RenamedTyClDecl] -> NF_TcM (LIE, TcMonoBinds, [Id])
tcClassDecls2 this_mod decls
= foldr combine
- (returnNF_Tc (emptyLIE, EmptyMonoBinds))
+ (returnNF_Tc (emptyLIE, EmptyMonoBinds, []))
[tcClassDecl2 cls_decl | cls_decl@(ClassDecl {tcdMeths = Just _}) <- decls]
-- The 'Just' picks out source ClassDecls
where
- combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
- tc2 `thenNF_Tc` \ (lie2, binds2) ->
+ combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1, ids1) ->
+ tc2 `thenNF_Tc` \ (lie2, binds2, ids2) ->
returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `AndMonoBinds` binds2)
+ binds1 `AndMonoBinds` binds2,
+ ids1 ++ ids2)
\end{code}
@tcClassDecl2@ generates bindings for polymorphic default methods
\begin{code}
tcClassDecl2 :: RenamedTyClDecl -- The class declaration
- -> NF_TcM (LIE, TcMonoBinds)
+ -> NF_TcM (LIE, TcMonoBinds, [Id])
tcClassDecl2 (ClassDecl {tcdName = class_name, tcdSigs = sigs,
tcdMeths = Just default_binds, tcdLoc = src_loc})
= -- The 'Just' picks out source ClassDecls
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds, [])) $
tcAddSrcLoc src_loc $
tcLookupClass class_name `thenNF_Tc` \ clas ->
prags = filter isPragSig sigs
tc_dm = tcDefMeth clas tyvars default_binds prags
in
- mapAndUnzipTc tc_dm op_items `thenTc` \ (defm_binds, const_lies) ->
+ mapAndUnzip3Tc tc_dm op_items `thenTc` \ (defm_binds, const_lies, dm_ids_s) ->
- returnTc (plusLIEs const_lies, andMonoBindList defm_binds)
+ returnTc (plusLIEs const_lies, andMonoBindList defm_binds, concat dm_ids_s)
-tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE)
-tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE)
+tcDefMeth clas tyvars binds_in prags (_, NoDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
+tcDefMeth clas tyvars binds_in prags (_, GenDefMeth) = returnTc (EmptyMonoBinds, emptyLIE, [])
-- Generate code for polymorphic default methods only
-- (Generic default methods have turned into instance decls by now.)
-- This is incompatible with Hugs, which expects a polymorphic
-- the programmer supplied an explicit default decl for the class.
-- (If necessary we can fix that, but we don't have a convenient Id to hand.)
-tcDefMeth clas tyvars binds_in prags op_item@(_, DefMeth dm_id)
- = tcInstTyVars tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
+tcDefMeth clas tyvars binds_in prags op_item@(sel_id, DefMeth dm_name)
+ = tcInstTyVars ClsTv tyvars `thenNF_Tc` \ (clas_tyvars, inst_tys, _) ->
let
- theta = [(mkClassPred clas inst_tys)]
+ dm_ty = idType sel_id -- Same as dict selector!
+ -- The default method's type should really come from the
+ -- iface file, since it could be usage-generalised, but this
+ -- requires altering the mess of knots in TcModule and I'm
+ -- too scared to do that. Instead, I have disabled generalisation
+ -- of types of default methods (and dict funs) by annotating them
+ -- TyGenNever (in MkId). Ugh! KSW 1999-09.
+
+ theta = [mkClassPred clas inst_tys]
+ dm_id = mkDefaultMethodId dm_name dm_ty
+ local_dm_id = setIdLocalExported dm_id
+ -- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
+ xtve = tyvars `zip` clas_tyvars
in
- newDicts origin theta `thenNF_Tc` \ [this_dict] ->
+ newDicts origin theta `thenNF_Tc` \ [this_dict] ->
- tcExtendTyVarEnvForMeths tyvars clas_tyvars (
- tcMethodBind clas origin clas_tyvars inst_tys theta
- binds_in prags False op_item
- ) `thenTc` \ (defm_bind, insts_needed, local_dm_inst) ->
+ mkMethodBind origin clas inst_tys binds_in op_item `thenTc` \ (dm_inst, meth_info) ->
+ tcMethodBind xtve clas_tyvars theta
+ [this_dict] meth_info `thenTc` \ (defm_bind, insts_needed) ->
tcAddErrCtxt (defltMethCtxt clas) $
(ptext SLIT("class") <+> ppr clas)
clas_tyvars
[this_dict]
- insts_needed `thenTc` \ (const_lie, dict_binds) ->
+ insts_needed `thenTc` \ (const_lie, dict_binds) ->
-- Simplification can do unification
- checkSigTyVars clas_tyvars emptyVarSet `thenTc` \ clas_tyvars' ->
+ checkSigTyVars clas_tyvars `thenTc` \ clas_tyvars' ->
let
full_bind = AbsBinds
clas_tyvars'
[instToId this_dict]
- [(clas_tyvars', dm_id, instToId local_dm_inst)]
+ [(clas_tyvars', local_dm_id, instToId dm_inst)]
emptyNameSet -- No inlines (yet)
(dict_binds `andMonoBinds` defm_bind)
in
- returnTc (full_bind, const_lie)
+ returnTc (full_bind, const_lie, [dm_id])
where
origin = ClassDeclOrigin
\end{code}
\begin{code}
tcMethodBind
- :: Class
- -> InstOrigin
+ :: [(TyVar,TcTyVar)] -- Bindings for type environment
-> [TcTyVar] -- Instantiated type variables for the
- -- enclosing class/instance decl.
- -- They'll be signature tyvars, and we
- -- want to check that they don't get bound
- -> [TcType] -- Instance types
- -> TcThetaType -- Available theta; this could be used to check
- -- the method signature, but actually that's done by
- -- the caller; here, it's just used for the error message
- -> RenamedMonoBinds -- Method binding (pick the right one from in here)
- -> [RenamedSig] -- Pramgas (just for this one)
- -> Bool -- True <=> This method is from an instance declaration
- -> ClassOpItem -- The method selector and default-method Id
- -> TcM (TcMonoBinds, LIE, Inst)
-
-tcMethodBind clas origin inst_tyvars inst_tys inst_theta
- meth_binds prags is_inst_decl (sel_id, dm_info)
+ -- enclosing class/instance decl.
+ -- They'll be signature tyvars, and we
+ -- want to check that they don't get bound
+ -- Always equal the range of the type envt
+ -> TcThetaType -- Available theta; it's just used for the error message
+ -> [Inst] -- Available from context, used to simplify constraints
+ -- from the method body
+ -> (Id, TcSigInfo, RenamedMonoBinds) -- Details of this method
+ -> TcM (TcMonoBinds, LIE)
+
+tcMethodBind xtve inst_tyvars inst_theta avail_insts
+ (sel_id, meth_sig, meth_bind)
+ =
+ -- Check the bindings; first adding inst_tyvars to the envt
+ -- so that we don't quantify over them in nested places
+ tcExtendTyVarEnv2 xtve (
+ tcAddErrCtxt (methodCtxt sel_id) $
+ tcMonoBinds meth_bind [meth_sig] NonRecursive
+ ) `thenTc` \ (meth_bind, meth_lie, _, _) ->
+
+ -- Now do context reduction. We simplify wrt both the local tyvars
+ -- and the ones of the class/instance decl, so that there is
+ -- no problem with
+ -- class C a where
+ -- op :: Eq a => a -> b -> a
+ --
+ -- We do this for each method independently to localise error messages
+
+ let
+ TySigInfo meth_id meth_tvs meth_theta _ local_meth_id _ _ = meth_sig
+ in
+ tcAddErrCtxtM (sigCtxt sel_id inst_tyvars inst_theta (idType meth_id)) $
+ newDicts SignatureOrigin meth_theta `thenNF_Tc` \ meth_dicts ->
+ let
+ all_tyvars = meth_tvs ++ inst_tyvars
+ all_insts = avail_insts ++ meth_dicts
+ in
+ tcSimplifyCheck
+ (ptext SLIT("class or instance method") <+> quotes (ppr sel_id))
+ all_tyvars all_insts meth_lie `thenTc` \ (lie, lie_binds) ->
+
+ checkSigTyVars all_tyvars `thenTc` \ all_tyvars' ->
+
+ let
+ meth_tvs' = take (length meth_tvs) all_tyvars'
+ poly_meth_bind = AbsBinds meth_tvs'
+ (map instToId meth_dicts)
+ [(meth_tvs', meth_id, local_meth_id)]
+ emptyNameSet -- Inlines?
+ (lie_binds `andMonoBinds` meth_bind)
+ in
+ returnTc (poly_meth_bind, lie)
+
+
+mkMethodBind :: InstOrigin
+ -> Class -> [TcType] -- Class and instance types
+ -> RenamedMonoBinds -- Method binding (pick the right one from in here)
+ -> ClassOpItem
+ -> TcM (Inst, -- Method inst
+ (Id, -- Global selector Id
+ TcSigInfo, -- Signature
+ RenamedMonoBinds)) -- Binding for the method
+
+mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
= tcGetSrcLoc `thenNF_Tc` \ loc ->
- newMethod origin sel_id inst_tys `thenNF_Tc` \ meth ->
+ newMethod origin sel_id inst_tys `thenNF_Tc` \ meth_inst ->
let
- meth_id = instToId meth
+ meth_id = instToId meth_inst
meth_name = idName meth_id
- sig_msg = ptext SLIT("When checking the expected type for class method") <+> ppr sel_id
- meth_prags = find_prags (idName sel_id) meth_name prags
in
- mkTcSig meth_id loc `thenNF_Tc` \ sig_info ->
-
-- Figure out what method binding to use
-- If the user suppplied one, use it, else construct a default one
(case find_bind (idName sel_id) meth_name meth_binds of
Just user_bind -> returnTc user_bind
- Nothing -> mkDefMethRhs is_inst_decl clas inst_tys sel_id loc dm_info `thenTc` \ rhs ->
+ Nothing -> mkDefMethRhs origin clas inst_tys sel_id loc dm_info `thenTc` \ rhs ->
returnTc (FunMonoBind meth_name False -- Not infix decl
[mkSimpleMatch [] rhs placeHolderType loc] loc)
) `thenTc` \ meth_bind ->
- -- Check the bindings; first add inst_tyvars to the envt
- -- so that we don't quantify over them in nested places
- -- The *caller* put the class/inst decl tyvars into the envt
- tcExtendGlobalTyVars (mkVarSet inst_tyvars)
- (tcAddErrCtxt (methodCtxt sel_id) $
- tcBindWithSigs NotTopLevel meth_bind
- [sig_info] meth_prags NonRecursive
- ) `thenTc` \ (binds, insts, _) ->
-
- tcExtendLocalValEnv [(meth_name, meth_id)]
- (tcSpecSigs meth_prags) `thenTc` \ (prag_binds1, prag_lie) ->
-
- -- The prag_lie for a SPECIALISE pragma will mention the function
- -- itself, so we have to simplify them away right now lest they float
- -- outwards!
- bindInstsOfLocalFuns prag_lie [meth_id] `thenTc` \ (prag_lie', prag_binds2) ->
-
- -- Now check that the instance type variables
- -- (or, in the case of a class decl, the class tyvars)
- -- have not been unified with anything in the environment
- --
- -- We do this for each method independently to localise error messages
- -- ...and this is why the call to tcExtendGlobalTyVars must be here
- -- rather than in the caller
- tcAddErrCtxtM (sigCtxt sig_msg inst_tyvars inst_theta (idType meth_id)) $
- checkSigTyVars inst_tyvars emptyVarSet `thenTc_`
-
- returnTc (binds `AndMonoBinds` prag_binds1 `AndMonoBinds` prag_binds2,
- insts `plusLIE` prag_lie',
- meth)
+
+ mkTcSig meth_id loc `thenNF_Tc` \ meth_sig ->
+
+ returnTc (meth_inst, (sel_id, meth_sig, meth_bind))
+
-- The user didn't supply a method binding,
-- so we have to make up a default binding
-- The RHS of a default method depends on the default-method info
-mkDefMethRhs is_inst_decl clas inst_tys sel_id loc (DefMeth dm_id)
+mkDefMethRhs origin clas inst_tys sel_id loc (DefMeth dm_name)
= -- An polymorphic default method
- returnTc (HsVar (idName dm_id))
+ returnTc (HsVar dm_name)
-mkDefMethRhs is_inst_decl clas inst_tys sel_id loc NoDefMeth
+mkDefMethRhs origin clas inst_tys sel_id loc NoDefMeth
= -- No default method
-- Warn only if -fwarn-missing-methods
doptsTc Opt_WarnMissingMethods `thenNF_Tc` \ warn ->
- warnTc (is_inst_decl && warn)
+ warnTc (isInstDecl origin && warn)
(omittedMethodWarn sel_id) `thenNF_Tc_`
returnTc error_rhs
where
- error_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
- (HsLit (HsString (_PK_ error_msg)))
+ error_rhs = HsLam (mkSimpleMatch wild_pats simple_rhs placeHolderType loc)
+ simple_rhs = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsStringPrim (mkFastString (stringToUtf8 error_msg))))
error_msg = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
-
-mkDefMethRhs is_inst_decl clas inst_tys sel_id loc GenDefMeth
+ -- When the type is of form t1 -> t2 -> t3
+ -- make a default method like (\ _ _ -> noMethBind "blah")
+ -- rather than simply (noMethBind "blah")
+ -- Reason: if t1 or t2 are higher-ranked types we get n
+ -- silly ambiguity messages.
+ -- Example: f :: (forall a. Eq a => a -> a) -> Int
+ -- f = error "urk"
+ -- Here, tcSub tries to force (error "urk") to have the right type,
+ -- thus: f = \(x::forall a. Eq a => a->a) -> error "urk" (x t)
+ -- where 't' is fresh ty var. This leads directly to "ambiguous t".
+ --
+ -- NB: technically this changes the meaning of the default-default
+ -- method slightly, because `seq` can see the lambdas. Oh well.
+ (_,_,tau1) = tcSplitSigmaTy (idType sel_id)
+ (_,_,tau2) = tcSplitSigmaTy tau1
+ -- Need two splits because the selector can have a type like
+ -- forall a. Foo a => forall b. Eq b => ...
+ (arg_tys, _) = tcSplitFunTys tau2
+ wild_pats = [WildPatIn | ty <- arg_tys]
+
+mkDefMethRhs origin clas inst_tys sel_id loc GenDefMeth
= -- A generic default method
-- If the method is defined generically, we can only do the job if the
-- instance declaration is for a single-parameter type class with
-- a type constructor applied to type arguments in the instance decl
-- (checkTc, so False provokes the error)
- checkTc (not is_inst_decl || simple_inst)
- (badGenericInstance sel_id) `thenTc_`
+ ASSERT( isInstDecl origin ) -- We never get here from a class decl
+
+ checkTc (isJust maybe_tycon)
+ (badGenericInstance sel_id (notSimple inst_tys)) `thenTc_`
+ checkTc (isJust (tyConGenInfo tycon))
+ (badGenericInstance sel_id (notGeneric tycon)) `thenTc_`
ioToTc (dumpIfSet opt_PprStyle_Debug "Generic RHS" stuff) `thenNF_Tc_`
returnTc rhs
-- case we require that the instance decl is for a single-parameter
-- type class with type variable arguments:
-- instance (...) => C (T a b)
- simple_inst = maybeToBool maybe_tycon
clas_tyvar = head (classTyVars clas)
Just tycon = maybe_tycon
maybe_tycon = case inst_tys of
Just (tycon, arg_tys) | all tcIsTyVarTy arg_tys -> Just tycon
other -> Nothing
other -> Nothing
+
+isInstDecl InstanceDeclOrigin = True
+isInstDecl ClassDeclOrigin = False
\end{code}
find_prags sel_name meth_name [] = []
find_prags sel_name meth_name (SpecSig name ty loc : prags)
| name == sel_name = SpecSig meth_name ty loc : find_prags sel_name meth_name prags
-find_prags sel_name meth_name (InlineSig name phase loc : prags)
- | name == sel_name = InlineSig meth_name phase loc : find_prags sel_name meth_name prags
-find_prags sel_name meth_name (NoInlineSig name phase loc : prags)
- | name == sel_name = NoInlineSig meth_name phase loc : find_prags sel_name meth_name prags
+find_prags sel_name meth_name (InlineSig sense name phase loc : prags)
+ | name == sel_name = InlineSig sense meth_name phase loc : find_prags sel_name meth_name prags
find_prags sel_name meth_name (prag:prags) = find_prags sel_name meth_name prags
\end{code}
Contexts and errors
~~~~~~~~~~~~~~~~~~~
\begin{code}
-classArityErr cls
- = ptext SLIT("Too many parameters for class") <+> quotes (ppr cls)
-
defltMethCtxt clas
= ptext SLIT("When checking the default methods for class") <+> quotes (ppr clas)
omittedMethodWarn sel_id
= ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id)
-badGenericMethodType op op_ty
- = hang (ptext SLIT("Generic method type is too complex"))
- 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
- ptext SLIT("You can only use type variables, arrows, and tuples")])
-
-badGenericInstance sel_id
+badGenericInstance sel_id because
= sep [ptext SLIT("Can't derive generic code for") <+> quotes (ppr sel_id),
- ptext SLIT("because the instance declaration is not for a simple type (T a b c)"),
- ptext SLIT("(where T is a derivable type constructor)")]
+ because]
+
+notSimple inst_tys
+ = vcat [ptext SLIT("because the instance type(s)"),
+ nest 2 (ppr inst_tys),
+ ptext SLIT("is not a simple type of form (T a b c)")]
+
+notGeneric tycon
+ = vcat [ptext SLIT("because the instance type constructor") <+> quotes (ppr tycon) <+>
+ ptext SLIT("was not compiled with -fgenerics")]
mixedGenericErr op
= ptext SLIT("Can't mix generic and non-generic equations for class method") <+> quotes (ppr op)
-
-genericMultiParamErr clas
- = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
- ptext SLIT("cannot have generic methods")
\end{code}
projects / ghc-hetmet.git / blobdiff