\section[TcInstDecls]{Typechecking instance declarations}
\begin{code}
-#include "HsVersions.h"
-
module TcInstDcls (
tcInstDecls1,
- tcInstDecls2,
- processInstBinds
+ tcInstDecls2
) where
+#include "HsVersions.h"
-import Ubiq
-
-import HsSyn ( InstDecl(..), FixityDecl, Sig(..),
- SpecInstSig(..), HsBinds(..), Bind(..),
- MonoBinds(..), GRHSsAndBinds, Match,
- InPat(..), OutPat(..), HsExpr(..), HsLit(..),
- Stmt, Qual, ArithSeqInfo, Fake,
- PolyType(..), MonoType )
-import RnHsSyn ( RenamedHsBinds(..), RenamedMonoBinds(..),
- RenamedInstDecl(..), RenamedFixityDecl(..),
- RenamedSig(..), RenamedSpecInstSig(..),
- RnName(..){-incl instance Outputable-}
+import HsSyn ( HsDecl(..), InstDecl(..),
+ HsBinds(..), MonoBinds(..), GRHSsAndBinds(..), GRHS(..),
+ HsExpr(..), InPat(..), HsLit(..), Sig(..),
+ unguardedRHS,
+ collectMonoBinders, andMonoBinds
+ )
+import HsBinds ( sigsForMe )
+import RnHsSyn ( RenamedHsBinds, RenamedMonoBinds,
+ RenamedInstDecl, RenamedHsExpr,
+ RenamedSig, RenamedHsDecl
+ )
+import TcHsSyn ( TcMonoBinds, TcIdOcc(..), TcIdBndr,
+ maybeBoxedPrimType, tcIdType
)
-import TcHsSyn ( TcIdOcc(..), TcHsBinds(..),
- TcMonoBinds(..), TcExpr(..), tcIdType,
- mkHsTyLam, mkHsTyApp,
- mkHsDictLam, mkHsDictApp )
-
-import TcMonad
-import GenSpecEtc ( checkSigTyVars )
-import Inst ( Inst, InstOrigin(..), InstanceMapper(..),
- newDicts, newMethod, LIE(..), emptyLIE, plusLIE )
import TcBinds ( tcPragmaSigs )
+import TcClassDcl ( tcMethodBind, badMethodErr )
+import TcMonad
+import RnMonad ( RnNameSupply )
+import Inst ( Inst, InstOrigin(..),
+ newDicts, LIE, emptyLIE, plusLIE, plusLIEs )
import TcDeriv ( tcDeriving )
-import TcEnv ( tcLookupClass, tcTyVarScope, newLocalId )
-import TcGRHSs ( tcGRHSsAndBinds )
-import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, buildInstanceEnvs )
+import TcEnv ( tcExtendGlobalValEnv, tcAddImportedIdInfo )
+import TcInstUtil ( InstInfo(..), mkInstanceRelatedIds, classDataCon )
import TcKind ( TcKind, unifyKind )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcContext, tcMonoTypeKind )
-import TcSimplify ( tcSimplifyAndCheck, tcSimplifyThetas )
-import TcType ( TcType(..), TcTyVar(..),
- tcInstSigTyVars, tcInstType, tcInstTheta
+import TcMonoType ( tcHsType )
+import TcSimplify ( tcSimplifyAndCheck )
+import TcType ( TcType, TcTyVar, TcTyVarSet,
+ zonkSigTyVar, tcInstSigTyVars, tcInstType, tcInstTheta
)
-import Unify ( unifyTauTy )
-
import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
- concatBag, foldBag, bagToList )
-import CmdLineOpts ( opt_GlasgowExts, opt_CompilingPrelude,
- opt_OmitDefaultInstanceMethods,
- opt_SpecialiseOverloaded )
-import Class ( GenClass, GenClassOp,
- isCcallishClass, getClassBigSig,
- getClassOps, getClassOpLocalType )
-import CoreUtils ( escErrorMsg )
-import Id ( GenId, idType, isDefaultMethodId_maybe )
-import ListSetOps ( minusList )
-import Maybes ( maybeToBool, expectJust )
-import Name ( getLocalName, origName, nameOf )
-import PrelInfo ( pAT_ERROR_ID )
-import PrelMods ( pRELUDE )
-import PprType ( GenType, GenTyVar, GenClass, GenClassOp, TyCon,
- pprParendGenType
+ foldBag, bagToList, Bag
+ )
+import CmdLineOpts ( opt_GlasgowExts, opt_WarnMissingMethods )
+import Class ( classBigSig, Class )
+import Id ( isNullaryDataCon, dataConArgTys, replaceIdInfo, idName, Id )
+import Maybes ( maybeToBool, seqMaybe, catMaybes )
+import Name ( nameOccName, mkLocalName,
+ isLocallyDefined, Module,
+ NamedThing(..)
)
-import PprStyle
-import Pretty
-import RnUtils ( GlobalNameMappers(..), GlobalNameMapper(..) )
-import TyCon ( derivedFor )
-import Type ( GenType(..), ThetaType(..), mkTyVarTys,
- splitSigmaTy, splitAppTy, isTyVarTy, matchTy, mkSigmaTy,
- getTyCon_maybe, maybeBoxedPrimType )
-import TyVar ( GenTyVar, mkTyVarSet )
+import PrelVals ( nO_METHOD_BINDING_ERROR_ID, eRROR_ID )
+import PprType ( pprParendType, pprConstraint )
+import SrcLoc ( SrcLoc, noSrcLoc )
+import TyCon ( isSynTyCon, isDataTyCon, tyConDerivings )
+import Type ( Type, ThetaType, isUnpointedType,
+ splitSigmaTy, isTyVarTy, mkSigmaTy,
+ splitTyConApp_maybe, splitDictTy_maybe,
+ splitAlgTyConApp_maybe, splitRhoTy,
+ tyVarsOfTypes
+ )
+import TyVar ( zipTyVarEnv, mkTyVarSet, tyVarSetToList, TyVar )
+import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon )
import TysWiredIn ( stringTy )
-import Unique ( Unique )
-import Util ( panic )
+import Unique ( Unique, cCallableClassKey, cReturnableClassKey, Uniquable(..) )
+import Outputable
\end{code}
Typechecking instance declarations is done in two passes. The first
\end{enumerate}
\begin{code}
-tcInstDecls1 :: Bag RenamedInstDecl
- -> [RenamedSpecInstSig]
+tcInstDecls1 :: TcEnv s -- Contains IdInfo for dfun ids
+ -> [RenamedHsDecl]
-> Module -- module name for deriving
- -> GlobalNameMappers -- renamer fns for deriving
- -> [RenamedFixityDecl] -- fixities for deriving
+ -> RnNameSupply -- for renaming derivings
-> TcM s (Bag InstInfo,
RenamedHsBinds,
- PprStyle -> Pretty)
+ SDoc)
-tcInstDecls1 inst_decls specinst_sigs mod_name renamer_name_funs fixities
+tcInstDecls1 unf_env decls mod_name rn_name_supply
= -- Do the ordinary instance declarations
- mapBagNF_Tc (tcInstDecl1 mod_name) inst_decls
- `thenNF_Tc` \ inst_info_bags ->
+ mapNF_Tc (tcInstDecl1 unf_env mod_name)
+ [inst_decl | InstD inst_decl <- decls] `thenNF_Tc` \ inst_info_bags ->
let
- decl_inst_info = concatBag inst_info_bags
+ decl_inst_info = unionManyBags inst_info_bags
in
-- Handle "derived" instances; note that we only do derivings
-- for things in this module; we ignore deriving decls from
- -- interfaces! We pass fixities, because they may be used
- -- in deriving Read and Show.
- tcDeriving mod_name renamer_name_funs decl_inst_info fixities
+ -- interfaces!
+ tcDeriving mod_name rn_name_supply decl_inst_info
`thenTc` \ (deriv_inst_info, deriv_binds, ddump_deriv) ->
let
- inst_info = deriv_inst_info `unionBags` decl_inst_info
- in
-{- LATER
- -- Handle specialise instance pragmas
- tcSpecInstSigs inst_info specinst_sigs
- `thenTc` \ spec_inst_info ->
--}
- let
- spec_inst_info = emptyBag -- For now
-
- full_inst_info = inst_info `unionBags` spec_inst_info
+ full_inst_info = deriv_inst_info `unionBags` decl_inst_info
in
returnTc (full_inst_info, deriv_binds, ddump_deriv)
-tcInstDecl1 :: FAST_STRING -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
+tcInstDecl1 :: TcEnv s -> Module -> RenamedInstDecl -> NF_TcM s (Bag InstInfo)
-tcInstDecl1 mod_name
- (InstDecl class_name
- poly_ty@(HsForAllTy tyvar_names context inst_ty)
- binds
- from_here inst_mod uprags pragmas src_loc)
+tcInstDecl1 unf_env mod_name (InstDecl poly_ty binds uprags (Just dfun_name) src_loc)
= -- Prime error recovery, set source location
recoverNF_Tc (returnNF_Tc emptyBag) $
tcAddSrcLoc src_loc $
- -- Look things up
- tcLookupClass class_name `thenNF_Tc` \ (clas_kind, clas) ->
-
+ -- Type-check all the stuff before the "where"
+ tcHsType poly_ty `thenTc` \ poly_ty' ->
let
- de_rn (RnName n) = n
+ (tyvars, theta, dict_ty) = splitSigmaTy poly_ty'
+ (clas, inst_tys) = case splitDictTy_maybe dict_ty of
+ Nothing -> pprPanic "tcInstDecl1" (ppr poly_ty)
+ Just pair -> pair
in
- -- Typecheck the context and instance type
- tcTyVarScope (map de_rn tyvar_names) (\ tyvars ->
- tcContext context `thenTc` \ theta ->
- tcMonoTypeKind inst_ty `thenTc` \ (tau_kind, tau) ->
- unifyKind clas_kind tau_kind `thenTc_`
- returnTc (tyvars, theta, tau)
- ) `thenTc` \ (inst_tyvars, inst_theta, inst_tau) ->
-- Check for respectable instance type
- scrutiniseInstanceType from_here clas inst_tau
- `thenTc` \ (inst_tycon,arg_tys) ->
-
- -- Deal with the case where we are deriving
- -- and importing the same instance
- if (not from_here && (clas `derivedFor` inst_tycon)
- && all isTyVarTy arg_tys)
- then
- if not opt_CompilingPrelude && maybeToBool inst_mod &&
- mod_name == expectJust "inst_mod" inst_mod
- then
- -- Imported instance came from this module;
- -- discard and derive fresh instance
- returnTc emptyBag
- else
- -- Imported instance declared in another module;
- -- report duplicate instance error
- failTc (derivingWhenInstanceImportedErr inst_mod clas inst_tycon)
- else
+ scrutiniseInstanceType clas inst_tys `thenTc_`
-- Make the dfun id and constant-method ids
- mkInstanceRelatedIds from_here inst_mod pragmas
- clas inst_tyvars inst_tau inst_theta uprags
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- returnTc (unitBag (InstInfo clas inst_tyvars inst_tau inst_theta
- dfun_theta dfun_id const_meth_ids
- binds from_here inst_mod src_loc uprags))
+ let
+ (dfun_id, dfun_theta) = mkInstanceRelatedIds dfun_name
+ clas tyvars inst_tys theta
+ -- Add info from interface file
+ final_dfun_id = tcAddImportedIdInfo unf_env dfun_id
+ in
+ returnTc (unitBag (InstInfo clas tyvars inst_tys theta
+ dfun_theta final_dfun_id
+ binds src_loc uprags))
\end{code}
\begin{code}
tcInstDecls2 :: Bag InstInfo
- -> NF_TcM s (LIE s, TcHsBinds s)
+ -> NF_TcM s (LIE s, TcMonoBinds s)
tcInstDecls2 inst_decls
- = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyBinds)) inst_decls
+ = foldBag combine tcInstDecl2 (returnNF_Tc (emptyLIE, EmptyMonoBinds)) inst_decls
where
combine tc1 tc2 = tc1 `thenNF_Tc` \ (lie1, binds1) ->
tc2 `thenNF_Tc` \ (lie2, binds2) ->
returnNF_Tc (lie1 `plusLIE` lie2,
- binds1 `ThenBinds` binds2)
+ binds1 `AndMonoBinds` binds2)
\end{code}
First comes the easy case of a non-local instance decl.
\begin{code}
-tcInstDecl2 :: InstInfo
- -> NF_TcM s (LIE s, TcHsBinds s)
+tcInstDecl2 :: InstInfo -> NF_TcM s (LIE s, TcMonoBinds s)
-tcInstDecl2 (InstInfo _ _ _ _ _ _ _ _ False{-import-} _ _ _)
+tcInstDecl2 (InstInfo clas inst_tyvars inst_tys
+ inst_decl_theta dfun_theta
+ dfun_id monobinds
+ locn uprags)
+ | not (isLocallyDefined dfun_id)
+ = returnNF_Tc (emptyLIE, EmptyMonoBinds)
+
+{-
+ -- I deleted this "optimisation" because when importing these
+ -- instance decls the renamer would look for the dfun bindings and they weren't there.
+ -- This would be fixable, but it seems simpler just to produce a tiny void binding instead,
+ -- even though it's never used.
+
+ -- This case deals with CCallable etc, which don't need any bindings
+ | isNoDictClass clas
= returnNF_Tc (emptyLIE, EmptyBinds)
+-}
-tcInstDecl2 (InstInfo clas inst_tyvars inst_ty
- inst_decl_theta dfun_theta
- dfun_id const_meth_ids monobinds
- True{-here-} inst_mod locn uprags)
+ | otherwise
= -- Prime error recovery
- recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyBinds)) $
- tcAddSrcLoc locn $
+ recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
+ tcAddSrcLoc locn $
-- Get the class signature
- tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
let
- (class_tyvar,
- super_classes, sc_sel_ids,
- class_ops, op_sel_ids, defm_ids) = getClassBigSig clas
+ origin = InstanceDeclOrigin
+ (class_tyvars,
+ sc_theta, sc_sel_ids,
+ op_sel_ids, defm_ids) = classBigSig clas
in
- tcInstType tenv inst_ty `thenNF_Tc` \ inst_ty' ->
+
+ -- Instantiate the instance decl with tc-style type variables
+ tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
+ mapNF_Tc (tcInstType tenv) inst_tys `thenNF_Tc` \ inst_tys' ->
tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' ->
tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
- let
- sc_theta' = super_classes `zip` (repeat inst_ty')
- origin = InstanceDeclOrigin
- mk_method sel_id = newMethodId sel_id inst_ty' origin locn
- in
+
+ -- Instantiate the super-class context with inst_tys
+ tcInstTheta (zipTyVarEnv class_tyvars inst_tys') sc_theta `thenNF_Tc` \ sc_theta' ->
+
-- Create dictionary Ids from the specified instance contexts.
newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) ->
newDicts origin dfun_theta' `thenNF_Tc` \ (dfun_arg_dicts, dfun_arg_dicts_ids) ->
newDicts origin inst_decl_theta' `thenNF_Tc` \ (inst_decl_dicts, _) ->
- newDicts origin [(clas,inst_ty')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+ newDicts origin [(clas,inst_tys')] `thenNF_Tc` \ (this_dict, [this_dict_id]) ->
+
+ -- Check that all the method bindings come from this class
+ let
+ check_from_this_class (bndr, loc)
+ | nameOccName bndr `elem` sel_names = returnNF_Tc ()
+ | otherwise = tcAddSrcLoc loc $
+ addErrTc (badMethodErr bndr clas)
+ sel_names = map getOccName op_sel_ids
+ bndrs = bagToList (collectMonoBinders monobinds)
+ in
+ mapNF_Tc check_from_this_class bndrs `thenNF_Tc_`
- -- Create method variables
- mapAndUnzipNF_Tc mk_method op_sel_ids `thenNF_Tc` \ (meth_insts_s, meth_ids) ->
+ tcExtendGlobalValEnv (catMaybes defm_ids) (
- -- Collect available Insts
+ -- Default-method Ids may be mentioned in synthesised RHSs
+ mapAndUnzip3Tc (tcInstMethodBind clas inst_tys' inst_tyvars' monobinds uprags)
+ (op_sel_ids `zip` defm_ids)
+ ) `thenTc` \ (method_binds_s, insts_needed_s, meth_lies_w_ids) ->
+
+ -- Deal with SPECIALISE instance pragmas
let
- avail_insts -- These insts are in scope; quite a few, eh?
- = unionManyBags (this_dict : dfun_arg_dicts : meth_insts_s)
-
- mk_method_expr
- = if opt_OmitDefaultInstanceMethods then
- makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty' clas inst_mod
- else
- makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty' this_dict_id
+ dfun_prags = [Sig (idName dfun_id) ty loc | SpecInstSig ty loc <- uprags]
in
- processInstBinds mk_method_expr inst_tyvars' avail_insts meth_ids monobinds
- `thenTc` \ (insts_needed, method_mbinds) ->
+ tcExtendGlobalValEnv [dfun_id] (
+ tcPragmaSigs dfun_prags
+ ) `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+
+ -- Check the overloading constraints of the methods and superclasses
+ mapNF_Tc zonkSigTyVar inst_tyvars' `thenNF_Tc` \ zonked_inst_tyvars ->
+
let
- -- Create the dict and method binds
- dict_bind
- = VarMonoBind this_dict_id (Dictionary sc_dict_ids meth_ids)
+ inst_tyvars_set = mkTyVarSet zonked_inst_tyvars
+
+ (meth_lies, meth_ids) = unzip meth_lies_w_ids
- dict_and_method_binds
- = dict_bind `AndMonoBinds` method_mbinds
+ -- These insts are in scope; quite a few, eh?
+ avail_insts = this_dict `plusLIE`
+ dfun_arg_dicts `plusLIE`
+ sc_dicts `plusLIE`
+ unionManyBags meth_lies
- inst_tyvars_set' = mkTyVarSet inst_tyvars'
+ methods_lie = plusLIEs insts_needed_s
in
- -- Check the overloading constraints of the methods and superclasses
- tcAddErrCtxt (bindSigCtxt meth_ids) (
- tcSimplifyAndCheck
- inst_tyvars_set' -- Local tyvars
- avail_insts
- (sc_dicts `unionBags` insts_needed) -- Need to get defns for all these
- ) `thenTc` \ (const_lie, super_binds) ->
-- Check that we *could* construct the superclass dictionaries,
-- even though we are *actually* going to pass the superclass dicts in;
-- the check ensures that the caller will never have a problem building
-- them.
- tcAddErrCtxt superClassSigCtxt (
- tcSimplifyAndCheck
- inst_tyvars_set' -- Local tyvars
+ tcAddErrCtxt superClassCtxt (
+ tcSimplifyAndCheck
+ (ptext SLIT("instance declaration context"))
+ inst_tyvars_set -- Local tyvars
inst_decl_dicts -- The instance dictionaries available
sc_dicts -- The superclass dicationaries reqd
) `thenTc_`
- -- Ignore the result; we're only doing
+ -- Ignore the result; we're only doing
-- this to make sure it can be done.
- -- Now process any SPECIALIZE pragmas for the methods
- let
- spec_sigs = [ s | s@(SpecSig _ _ _ _) <- uprags ]
- in
- tcPragmaSigs spec_sigs `thenTc` \ (_, spec_binds, spec_lie) ->
+ -- Ditto method bindings
+ tcAddErrCtxt methodCtxt (
+ tcSimplifyAndCheck
+ (ptext SLIT("instance declaration context"))
+ inst_tyvars_set -- Local tyvars
+ avail_insts
+ methods_lie
+ ) `thenTc_`
+
+ -- Now do the simplification again, this time to get the
+ -- bindings; this time we use an enhanced "avails"
+ -- Ignore errors because they come from the *previous* tcSimplifys
+ discardErrsTc (
+ tcSimplifyAndCheck
+ (ptext SLIT("instance declaration context"))
+ inst_tyvars_set
+ dfun_arg_dicts -- NB! Don't include this_dict here, else the sc_dicts
+ -- get bound by just selecting from this_dict!!
+ (sc_dicts `plusLIE` methods_lie `plusLIE` prag_lie)
+ ) `thenTc` \ (const_lie, lie_binds) ->
+
+
+ -- Create the result bindings
let
- -- Complete the binding group, adding any spec_binds
- inst_binds
+ dict_constr = classDataCon clas
+ scs_and_meths = sc_dict_ids ++ meth_ids
+
+ dict_rhs
+ | null scs_and_meths
+ = -- Blatant special case for CCallable, CReturnable
+ -- If the dictionary is empty then we should never
+ -- select anything from it, so we make its RHS just
+ -- emit an error message. This in turn means that we don't
+ -- mention the constructor, which doesn't exist for CCallable, CReturnable
+ -- Hardly beautiful, but only three extra lines.
+ HsApp (TyApp (HsVar (RealId eRROR_ID)) [tcIdType this_dict_id])
+ (HsLitOut (HsString msg) stringTy)
+
+ | otherwise -- The common case
+ = foldl HsApp (TyApp (HsVar (RealId dict_constr)) inst_tys')
+ (map HsVar (sc_dict_ids ++ meth_ids))
+ -- We don't produce a binding for the dict_constr; instead we
+ -- rely on the simplifier to unfold this saturated application
+ where
+ msg = _PK_ ("Compiler error: bad dictionary " ++ showSDoc (ppr clas))
+
+ dict_bind = VarMonoBind this_dict_id dict_rhs
+ method_binds = andMonoBinds method_binds_s
+
+ final_dfun_id = replaceIdInfo dfun_id (prag_info_fn (idName dfun_id))
+ -- Pretty truesome
+ main_bind
= AbsBinds
- inst_tyvars'
+ zonked_inst_tyvars
dfun_arg_dicts_ids
- ((this_dict_id, RealId dfun_id)
- : (meth_ids `zip` (map RealId const_meth_ids)))
- -- const_meth_ids will often be empty
- super_binds
- (RecBind dict_and_method_binds)
-
- `ThenBinds`
- spec_binds
+ [(inst_tyvars', RealId final_dfun_id, this_dict_id)]
+ (lie_binds `AndMonoBinds`
+ method_binds `AndMonoBinds`
+ prag_binds `AndMonoBinds`
+ dict_bind)
in
-
- returnTc (const_lie `plusLIE` spec_lie, inst_binds)
-\end{code}
-
-@mkMethodId@ manufactures an id for a local method.
-It's rather turgid stuff, because there are two cases:
-
- (a) For methods with no local polymorphism, we can make an Inst of the
- class-op selector function and a corresp InstId;
- which is good because then other methods which call
- this one will do so directly.
-
- (b) For methods with local polymorphism, we can't do this. For example,
-
- class Foo a where
- op :: (Num b) => a -> b -> a
-
- Here the type of the class-op-selector is
-
- forall a b. (Foo a, Num b) => a -> b -> a
-
- The locally defined method at (say) type Float will have type
-
- forall b. (Num b) => Float -> b -> Float
-
- and the one is not an instance of the other.
-
- So for these we just make a local (non-Inst) id with a suitable type.
-
-How disgusting.
-
-\begin{code}
-newMethodId sel_id inst_ty origin loc
- = let (sel_tyvars,sel_theta,sel_tau) = splitSigmaTy (idType sel_id)
- (_:meth_theta) = sel_theta -- The local theta is all except the
- -- first element of the context
- in
- case sel_tyvars of
- -- Ah! a selector for a class op with no local polymorphism
- -- Build an Inst for this
- [clas_tyvar] -> newMethod origin (RealId sel_id) [inst_ty]
-
- -- Ho! a selector for a class op with local polymorphism.
- -- Just make a suitably typed local id for this
- (clas_tyvar:local_tyvars) ->
- tcInstType [(clas_tyvar,inst_ty)]
- (mkSigmaTy local_tyvars meth_theta sel_tau)
- `thenNF_Tc` \ method_ty ->
- newLocalId (getLocalName sel_id) method_ty `thenNF_Tc` \ meth_id ->
- returnNF_Tc (emptyLIE, meth_id)
-\end{code}
-
-The next function makes a default method which calls the global default method, at
-the appropriate instance type.
-
-See the notes under default decls in TcClassDcl.lhs.
-
-\begin{code}
-makeInstanceDeclDefaultMethodExpr
- :: InstOrigin s
- -> [TcIdOcc s]
- -> [Id]
- -> TcType s
- -> TcIdOcc s
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeInstanceDeclDefaultMethodExpr origin meth_ids defm_ids inst_ty this_dict tag
- = newDicts origin op_theta `thenNF_Tc` \ (op_lie,op_dicts) ->
-
- -- def_op_id = /\ op_tyvars -> \ op_dicts ->
- -- defm_id inst_ty op_tyvars this_dict op_dicts
- returnNF_Tc (
- mkHsTyLam op_tyvars (
- mkHsDictLam op_dicts (
- mkHsDictApp (mkHsTyApp (HsVar (RealId defm_id))
- (inst_ty : mkTyVarTys op_tyvars))
- (this_dict : op_dicts)
- )))
- where
- idx = tag - 1
- meth_id = meth_ids !! idx
- defm_id = defm_ids !! idx
- (op_tyvars, op_theta, op_tau) = splitSigmaTy (tcIdType meth_id)
-
-makeInstanceDeclNoDefaultExpr
- :: InstOrigin s
- -> [TcIdOcc s]
- -> [Id]
- -> TcType s
- -> Class
- -> Maybe Module
- -> Int
- -> NF_TcM s (TcExpr s)
-
-makeInstanceDeclNoDefaultExpr origin meth_ids defm_ids inst_ty clas inst_mod tag
- = newDicts origin op_theta `thenNF_Tc` \ (op_lie, op_dicts) ->
-
- -- Produce a warning if the default instance method
- -- has been omitted when one exists in the class
- warnTc (not err_defm_ok)
- (omitDefaultMethodWarn clas_op clas_name inst_ty)
- `thenNF_Tc_`
- returnNF_Tc (mkHsTyLam op_tyvars (
- mkHsDictLam op_dicts (
- HsApp (mkHsTyApp (HsVar (RealId pAT_ERROR_ID)) [op_tau])
- (HsLitOut (HsString (_PK_ error_msg)) stringTy))))
- where
- idx = tag - 1
- meth_id = meth_ids !! idx
- clas_op = (getClassOps clas) !! idx
- defm_id = defm_ids !! idx
- (op_tyvars,op_theta,op_tau) = splitSigmaTy (tcIdType meth_id)
-
- Just (_, _, err_defm_ok) = isDefaultMethodId_maybe defm_id
-
- error_msg = "%E" -- => No explicit method for \"
- ++ escErrorMsg error_str
-
- mod_str = case inst_mod of { Nothing -> pRELUDE; Just m -> m }
-
- error_str = _UNPK_ mod_str ++ "." ++ _UNPK_ clas_name ++ "."
- ++ (ppShow 80 (ppr PprForUser inst_ty)) ++ "."
- ++ (ppShow 80 (ppr PprForUser clas_op)) ++ "\""
-
- clas_name = nameOf (origName clas)
+ returnTc (const_lie,
+ main_bind `AndMonoBinds` prag_binds)
\end{code}
%* *
%************************************************************************
-@processInstBinds@ returns a @MonoBinds@ which binds
-all the method ids (which are passed in). It is used
- - both for instance decls,
- - and to compile the default-method declarations in a class decl.
-
-Any method ids which don't have a binding have a suitable default
-binding created for them. The actual right-hand side used is
-created using a function which is passed in, because the right thing to
-do differs between instance and class decls.
-
\begin{code}
-processInstBinds
- :: (Int -> NF_TcM s (TcExpr s)) -- Function to make default method
- -> [TcTyVar s] -- Tyvars for this instance decl
- -> LIE s -- available Insts
- -> [TcIdOcc s] -- Local method ids in tag order
- -- (instance tyvars are free in their types)
- -> RenamedMonoBinds
- -> TcM s (LIE s, -- These are required
- TcMonoBinds s)
-
-processInstBinds mk_default_method_rhs inst_tyvars avail_insts method_ids monobinds
- =
- -- Process the explicitly-given method bindings
- processInstBinds1 inst_tyvars avail_insts method_ids monobinds
- `thenTc` \ (tags, insts_needed_in_methods, method_binds) ->
-
- -- Find the methods not handled, and make default method bindings for them.
+tcInstMethodBind
+ :: Class
+ -> [TcType s] -- Instance types
+ -> [TcTyVar s] -- and their free (sig) tyvars
+ -> RenamedMonoBinds -- Method binding
+ -> [RenamedSig] -- Pragmas
+ -> (Id, Maybe Id) -- Selector id and default-method id
+ -> TcM s (TcMonoBinds s, LIE s, (LIE s, TcIdOcc s))
+
+tcInstMethodBind clas inst_tys inst_tyvars meth_binds prags (sel_id, maybe_dm_id)
+ = tcGetSrcLoc `thenNF_Tc` \ loc ->
+ tcGetUnique `thenNF_Tc` \ uniq ->
let
- unmentioned_tags = [1.. length method_ids] `minusList` tags
+ sel_name = idName sel_id
+ meth_occ = getOccName sel_name
+ default_meth_name = mkLocalName uniq meth_occ loc
+ maybe_meth_bind = find sel_name meth_binds
+ the_meth_bind = case maybe_meth_bind of
+ Just stuff -> stuff
+ Nothing -> mk_default_bind default_meth_name loc
+ meth_prags = sigsForMe (== sel_name) prags
in
- mapNF_Tc mk_default_method unmentioned_tags
- `thenNF_Tc` \ default_bind_list ->
- returnTc (insts_needed_in_methods,
- foldr AndMonoBinds method_binds default_bind_list)
+ -- Warn if no method binding, only if -fwarn-missing-methods
+
+ warnTc (opt_WarnMissingMethods &&
+ not (maybeToBool maybe_meth_bind) &&
+ not (maybeToBool maybe_dm_id))
+ (omittedMethodWarn sel_id clas) `thenNF_Tc_`
+
+ -- Typecheck the method binding
+ tcMethodBind clas origin inst_tys inst_tyvars sel_id the_meth_bind meth_prags
where
- -- From a tag construct us the passed-in function to construct
- -- the binding for the default method
- mk_default_method tag = mk_default_method_rhs tag `thenNF_Tc` \ rhs ->
- returnNF_Tc (VarMonoBind (method_ids !! (tag-1)) rhs)
-\end{code}
+ origin = InstanceDeclOrigin -- Poor
-\begin{code}
-processInstBinds1
- :: [TcTyVar s] -- Tyvars for this instance decl
- -> LIE s -- available Insts
- -> [TcIdOcc s] -- Local method ids in tag order (instance tyvars are free),
- -> RenamedMonoBinds
- -> TcM s ([Int], -- Class-op tags accounted for
- LIE s, -- These are required
- TcMonoBinds s)
-
-processInstBinds1 inst_tyvars avail_insts method_ids EmptyMonoBinds
- = returnTc ([], emptyLIE, EmptyMonoBinds)
-
-processInstBinds1 inst_tyvars avail_insts method_ids (AndMonoBinds mb1 mb2)
- = processInstBinds1 inst_tyvars avail_insts method_ids mb1
- `thenTc` \ (op_tags1,dicts1,method_binds1) ->
- processInstBinds1 inst_tyvars avail_insts method_ids mb2
- `thenTc` \ (op_tags2,dicts2,method_binds2) ->
- returnTc (op_tags1 ++ op_tags2,
- dicts1 `unionBags` dicts2,
- AndMonoBinds method_binds1 method_binds2)
-\end{code}
+ find sel EmptyMonoBinds = Nothing
+ find sel (AndMonoBinds b1 b2) = find sel b1 `seqMaybe` find sel b2
-\begin{code}
-processInstBinds1 inst_tyvars avail_insts method_ids mbind
- =
- -- Find what class op is being defined here. The complication is
- -- that we could have a PatMonoBind or a FunMonoBind. If the
- -- former, it should only bind a single variable, or else we're in
- -- trouble (I'm not sure what the static semantics of methods
- -- defined in a pattern binding with multiple patterns is!)
- -- Renamer has reduced us to these two cases.
- let
- (op,locn) = case mbind of
- FunMonoBind op _ _ locn -> (op, locn)
- PatMonoBind (VarPatIn op) _ locn -> (op, locn)
+ find sel b@(FunMonoBind op_name _ _ _) | op_name == sel = Just b
+ | otherwise = Nothing
+ find sel b@(PatMonoBind (VarPatIn op_name) _ _) | op_name == sel = Just b
+ | otherwise = Nothing
+ find sel other = panic "Urk! Bad instance method binding"
- occ = getLocalName op
- origin = InstanceDeclOrigin
- in
- tcAddSrcLoc locn $
- -- Make a method id for the method
- let tag = panic "processInstBinds1:getTagFromClassOpName"{-getTagFromClassOpName op-}
- method_id = method_ids !! (tag-1)
+ mk_default_bind local_meth_name loc
+ = PatMonoBind (VarPatIn local_meth_name)
+ (GRHSsAndBindsIn (unguardedRHS (default_expr loc) loc) EmptyBinds)
+ loc
- method_ty = tcIdType method_id
- (method_tyvars, method_theta, method_tau) = splitSigmaTy method_ty
- in
- newDicts origin method_theta `thenNF_Tc` \ (method_dicts,method_dict_ids) ->
-
- case (method_tyvars, method_dict_ids) of
-
- ([],[]) -> -- The simple case; no local polymorphism or overloading in the method
-
- -- Type check the method itself
- tcMethodBind method_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
- returnTc ([tag], lieIop, mbind')
-
- other -> -- It's a locally-polymorphic and/or overloaded method; UGH!
-
- -- Make a new id for (a) the local, non-overloaded method
- -- and (b) the locally-overloaded method
- -- The latter is needed just so we can return an AbsBinds wrapped
- -- up inside a MonoBinds.
-
- newLocalId occ method_tau `thenNF_Tc` \ local_id ->
- newLocalId occ method_ty `thenNF_Tc` \ copy_id ->
- let
- inst_method_tyvars = inst_tyvars ++ method_tyvars
- in
- -- Typecheck the method
- tcMethodBind local_id method_tau mbind `thenTc` \ (mbind', lieIop) ->
-
- -- Check the overloading part of the signature.
- -- Simplify everything fully, even though some
- -- constraints could "really" be left to the next
- -- level out. The case which forces this is
- --
- -- class Foo a where { op :: Bar a => a -> a }
- --
- -- Here we must simplify constraints on "a" to catch all
- -- the Bar-ish things.
- tcAddErrCtxt (methodSigCtxt op method_ty) (
- tcSimplifyAndCheck
- (mkTyVarSet inst_method_tyvars)
- (method_dicts `plusLIE` avail_insts)
- lieIop
- ) `thenTc` \ (f_dicts, dict_binds) ->
-
- returnTc ([tag],
- f_dicts,
- VarMonoBind method_id
- (HsLet
- (AbsBinds
- method_tyvars
- method_dict_ids
- [(local_id, copy_id)]
- dict_binds
- (NonRecBind mbind'))
- (HsVar copy_id)))
-\end{code}
+ default_expr loc
+ = case maybe_dm_id of
+ Just dm_id -> HsVar (getName dm_id) -- There's a default method
+ Nothing -> error_expr loc -- No default method
-\begin{code}
-tcMethodBind :: TcIdOcc s -> TcType s -> RenamedMonoBinds
- -> TcM s (TcMonoBinds s, LIE s)
-
-tcMethodBind meth_id meth_ty (FunMonoBind name inf matches locn)
- = tcMatchesFun name meth_ty matches `thenTc` \ (rhs', lie) ->
- returnTc (FunMonoBind meth_id inf rhs' locn, lie)
-
-tcMethodBind meth_id meth_ty pbind@(PatMonoBind pat grhss_and_binds locn)
- -- pat is sure to be a (VarPatIn op)
- = tcAddErrCtxt (patMonoBindsCtxt pbind) $
- tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds', lie, rhs_ty) ->
- unifyTauTy meth_ty rhs_ty `thenTc_`
- returnTc (PatMonoBind (VarPat meth_id) grhss_and_binds' locn, lie)
+ error_expr loc
+ = HsApp (HsVar (getName nO_METHOD_BINDING_ERROR_ID))
+ (HsLit (HsString (_PK_ (error_msg loc))))
+
+ error_msg loc = showSDoc (hcat [ppr loc, text "|", ppr sel_id ])
\end{code}
+
%************************************************************************
%* *
-\subsection{Type-checking specialise instance pragmas}
+\subsection{Checking for a decent instance type}
%* *
%************************************************************************
-\begin{code}
-{- LATER
-tcSpecInstSigs :: E -> CE -> TCE
- -> Bag InstInfo -- inst decls seen (declared and derived)
- -> [RenamedSpecInstSig] -- specialise instance upragmas
- -> TcM (Bag InstInfo) -- new, overlapped, inst decls
-
-tcSpecInstSigs e ce tce inst_infos []
- = returnTc emptyBag
-
-tcSpecInstSigs e ce tce inst_infos sigs
- = buildInstanceEnvs inst_infos `thenTc` \ inst_mapper ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ spec_inst_infos ->
- returnTc spec_inst_infos
- where
- tc_inst_spec_sigs inst_mapper []
- = returnNF_Tc emptyBag
- tc_inst_spec_sigs inst_mapper (sig:sigs)
- = tcSpecInstSig e ce tce inst_infos inst_mapper sig `thenNF_Tc` \ info_sig ->
- tc_inst_spec_sigs inst_mapper sigs `thenNF_Tc` \ info_sigs ->
- returnNF_Tc (info_sig `unionBags` info_sigs)
-
-tcSpecInstSig :: E -> CE -> TCE
- -> Bag InstInfo
- -> InstanceMapper
- -> RenamedSpecInstSig
- -> NF_TcM (Bag InstInfo)
-
-tcSpecInstSig e ce tce inst_infos inst_mapper (SpecInstSig class_name ty src_loc)
- = recoverTc emptyBag (
- tcAddSrcLoc src_loc (
- let
- clas = lookupCE ce class_name -- Renamer ensures this can't fail
-
- -- Make some new type variables, named as in the specialised instance type
- ty_names = extractMonoTyNames ???is_tyvarish_name??? ty
- (tmpl_e,inst_tmpls,inst_tmpl_tys) = mkTVE ty_names
- in
- babyTcMtoTcM (tcInstanceType ce tce tmpl_e True src_loc ty)
- `thenTc` \ inst_ty ->
- let
- maybe_tycon = case maybeAppDataTyCon inst_ty of
- Just (tc,_,_) -> Just tc
- Nothing -> Nothing
-
- maybe_unspec_inst = lookup_unspec_inst clas maybe_tycon inst_infos
- in
- -- Check that we have a local instance declaration to specialise
- checkMaybeTc maybe_unspec_inst
- (specInstUnspecInstNotFoundErr clas inst_ty src_loc) `thenTc_`
-
- -- Create tvs to substitute for tmpls while simplifying the context
- copyTyVars inst_tmpls `thenNF_Tc` \ (tv_e, inst_tvs, inst_tv_tys) ->
- let
- Just (InstInfo _ unspec_tyvars unspec_inst_ty unspec_theta
- _ _ _ binds True{-from here-} mod _ uprag) = maybe_unspec_inst
-
- subst = case matchTy unspec_inst_ty inst_ty of
- Just subst -> subst
- Nothing -> panic "tcSpecInstSig:matchTy"
-
- subst_theta = instantiateThetaTy subst unspec_theta
- subst_tv_theta = instantiateThetaTy tv_e subst_theta
-
- mk_spec_origin clas ty
- = InstanceSpecOrigin inst_mapper clas ty src_loc
- in
- tcSimplifyThetas mk_spec_origin subst_tv_theta
- `thenTc` \ simpl_tv_theta ->
- let
- simpl_theta = [ (clas, tv_to_tmpl tv) | (clas, tv) <- simpl_tv_theta ]
-
- tv_tmpl_map = inst_tv_tys `zipEqual` inst_tmpl_tys
- tv_to_tmpl tv = assoc "tcSpecInstSig" tv_tmpl_map tv
- in
- mkInstanceRelatedIds e True{-from here-} mod NoInstancePragmas src_loc
- clas inst_tmpls inst_ty simpl_theta uprag
- `thenTc` \ (dfun_id, dfun_theta, const_meth_ids) ->
-
- getSwitchCheckerTc `thenNF_Tc` \ sw_chkr ->
- (if sw_chkr SpecialiseTrace then
- pprTrace "Specialised Instance: "
- (ppAboves [ppCat [if null simpl_theta then ppNil else ppr PprDebug simpl_theta,
- if null simpl_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendGenType PprDebug inst_ty],
- ppCat [ppStr " derived from:",
- if null unspec_theta then ppNil else ppr PprDebug unspec_theta,
- if null unspec_theta then ppNil else ppStr "=>",
- ppr PprDebug clas,
- pprParendGenType PprDebug unspec_inst_ty]])
- else id) (
-
- returnTc (unitBag (InstInfo clas inst_tmpls inst_ty simpl_theta
- dfun_theta dfun_id const_meth_ids
- binds True{-from here-} mod src_loc uprag))
- )))
-
-
-lookup_unspec_inst clas maybe_tycon inst_infos
- = case filter (match_info match_inst_ty) (bagToList inst_infos) of
- [] -> Nothing
- (info:_) -> Just info
- where
- match_info match_ty (InstInfo inst_clas _ inst_ty _ _ _ _ _ from_here _ _ _)
- = from_here && clas == inst_clas &&
- match_ty inst_ty && is_plain_instance inst_ty
-
- match_inst_ty = case maybe_tycon of
- Just tycon -> match_tycon tycon
- Nothing -> match_fun
-
- match_tycon tycon inst_ty = case (maybeAppDataTyCon inst_ty) of
- Just (inst_tc,_,_) -> tycon == inst_tc
- Nothing -> False
-
- match_fun inst_ty = isFunType inst_ty
-
-
-is_plain_instance inst_ty
- = case (maybeAppDataTyCon inst_ty) of
- Just (_,tys,_) -> all isTyVarTemplateTy tys
- Nothing -> case maybeUnpackFunTy inst_ty of
- Just (arg, res) -> isTyVarTemplateTy arg && isTyVarTemplateTy res
- Nothing -> error "TcInstDecls:is_plain_instance"
--}
-\end{code}
-
-
-Checking for a decent instance type
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints:
it must normally look like: @instance Foo (Tycon a b c ...) ...@
We can also have instances for functions: @instance Foo (a -> b) ...@.
\begin{code}
-scrutiniseInstanceType from_here clas inst_tau
- -- TYCON CHECK
- | not (maybeToBool inst_tycon_maybe)
- = failTc (instTypeErr inst_tau)
-
- -- IMPORTED INSTANCES ARE OK (but see tcInstDecl1)
- | from_here
- = returnTc (inst_tycon,arg_tys)
-
- -- TYVARS CHECK
- | not (all isTyVarTy arg_tys ||
- not from_here ||
- opt_GlasgowExts)
- = failTc (instTypeErr inst_tau)
+scrutiniseInstanceType clas inst_taus
+ | -- CCALL CHECK (a).... urgh!
+ -- To verify that a user declaration of a CCallable/CReturnable
+ -- instance is OK, we must be able to see the constructor(s)
+ -- of the instance type (see next guard.)
+ --
+ -- We flag this separately to give a more precise error msg.
+ --
+ (uniqueOf clas == cCallableClassKey || uniqueOf clas == cReturnableClassKey)
+ && is_alg_tycon_app && not constructors_visible
+ = failWithTc (invisibleDataConPrimCCallErr clas first_inst_tau)
+
+ | -- CCALL CHECK (b)
+ -- A user declaration of a CCallable/CReturnable instance
+ -- must be for a "boxed primitive" type.
+ (uniqueOf clas == cCallableClassKey && not (ccallable_type first_inst_tau)) ||
+ (uniqueOf clas == cReturnableClassKey && not (creturnable_type first_inst_tau))
+ = failWithTc (nonBoxedPrimCCallErr clas first_inst_tau)
-- DERIVING CHECK
-- It is obviously illegal to have an explicit instance
-- for something that we are also planning to `derive'
- -- Though we can have an explicit instance which is more
- -- specific than the derived instance
- | clas `derivedFor` inst_tycon
- && all isTyVarTy arg_tys
- = failTc (derivingWhenInstanceExistsErr clas inst_tycon)
-
- | -- CCALL CHECK
- -- A user declaration of a CCallable/CReturnable instance
- -- must be for a "boxed primitive" type.
- isCcallishClass clas
- && not opt_CompilingPrelude -- which allows anything
- && maybeToBool (maybeBoxedPrimType inst_tau)
- = failTc (nonBoxedPrimCCallErr clas inst_tau)
+ | maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon)
+ = failWithTc (derivingWhenInstanceExistsErr clas first_inst_tau)
+ -- Kind check will have ensured inst_taus is of length 1
+
+ -- WITH HASKELL 1.4, MUST HAVE C (T a b c)
+ | not opt_GlasgowExts
+ && not (length inst_taus == 1 &&
+ maybeToBool maybe_tycon_app && -- Yes, there's a type constuctor
+ not (isSynTyCon tycon) && -- ...but not a synonym
+ all isTyVarTy arg_tys && -- Applied to type variables
+ length (tyVarSetToList (tyVarsOfTypes arg_tys)) == length arg_tys
+ -- This last condition checks that all the type variables are distinct
+ )
+ = failWithTc (instTypeErr clas inst_taus
+ (text "the instance type must be of form (T a b c)" $$
+ text "where T is not a synonym, and a,b,c are distinct type variables")
+ )
| otherwise
- = returnTc (inst_tycon,arg_tys)
-
- where
- (possible_tycon, arg_tys) = splitAppTy inst_tau
- inst_tycon_maybe = getTyCon_maybe possible_tycon
- inst_tycon = expectJust "tcInstDecls1:inst_tycon" inst_tycon_maybe
-\end{code}
-
-\begin{code}
+ = returnTc ()
-instTypeErr ty sty
- = case ty of
- SynTy tc _ _ -> ppBesides [ppStr "The type synonym `", ppr sty tc, rest_of_msg]
- TyVarTy tv -> ppBesides [ppStr "The type variable `", ppr sty tv, rest_of_msg]
- other -> ppBesides [ppStr "The type `", ppr sty ty, rest_of_msg]
where
- rest_of_msg = ppStr "' cannot be used as an instance type."
+ (first_inst_tau : _) = inst_taus
-derivingWhenInstanceExistsErr clas tycon sty
- = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"])
- 4 (ppStr "when an explicit instance exists")
-
-derivingWhenInstanceImportedErr inst_mod clas tycon sty
- = ppHang (ppBesides [ppStr "Deriving class `", ppr sty clas, ppStr "' type `", ppr sty tycon, ppStr "'"])
- 4 (ppBesides [ppStr "when an instance declared in module `", pp_mod, ppStr "' has been imported"])
- where
- pp_mod = case inst_mod of
- Nothing -> ppPStr SLIT("the standard Prelude")
- Just m -> ppBesides [ppStr "module `", ppPStr m, ppStr "'"]
-
-nonBoxedPrimCCallErr clas inst_ty sty
- = ppHang (ppStr "Instance isn't for a `boxed-primitive' type")
- 4 (ppBesides [ ppStr "class `", ppr sty clas, ppStr "' type `",
- ppr sty inst_ty, ppStr "'"])
-
-omitDefaultMethodWarn clas_op clas_name inst_ty sty
- = ppCat [ppStr "Warning: Omitted default method for",
- ppr sty clas_op, ppStr "in instance",
- ppPStr clas_name, pprParendGenType sty inst_ty]
+ -- Stuff for algebraic or -> type
+ maybe_tycon_app = splitTyConApp_maybe first_inst_tau
+ Just (tycon, arg_tys) = maybe_tycon_app
+ -- Stuff for an *algebraic* data type
+ alg_tycon_app_maybe = splitAlgTyConApp_maybe first_inst_tau
+ -- The "Alg" part looks through synonyms
+ is_alg_tycon_app = maybeToBool alg_tycon_app_maybe
+ Just (alg_tycon, _, data_cons) = alg_tycon_app_maybe
-patMonoBindsCtxt pbind sty
- = ppHang (ppStr "In a pattern binding:")
- 4 (ppr sty pbind)
+ constructors_visible = not (null data_cons)
+
-methodSigCtxt name ty sty
- = ppHang (ppBesides [ppStr "When matching the definition of class method `",
- ppr sty name, ppStr "' to its signature :" ])
- 4 (ppr sty ty)
+-- These conditions come directly from what the DsCCall is capable of.
+-- Totally grotesque. Green card should solve this.
-bindSigCtxt method_ids sty
- = ppHang (ppStr "When checking type signatures for: ")
- 4 (ppInterleave (ppStr ", ") (map (ppr sty) method_ids))
+ccallable_type ty = isUnpointedType ty || -- Allow CCallable Int# etc
+ maybeToBool (maybeBoxedPrimType ty) || -- Ditto Int etc
+ ty == stringTy ||
+ byte_arr_thing
+ where
+ byte_arr_thing = case splitAlgTyConApp_maybe ty of
+ Just (tycon, ty_args, [data_con]) | isDataTyCon tycon ->
+ length data_con_arg_tys == 2 &&
+ maybeToBool maybe_arg2_tycon &&
+ (arg2_tycon == byteArrayPrimTyCon ||
+ arg2_tycon == mutableByteArrayPrimTyCon)
+ where
+ data_con_arg_tys = dataConArgTys data_con ty_args
+ (data_con_arg_ty1 : data_con_arg_ty2 : _) = data_con_arg_tys
+ maybe_arg2_tycon = splitTyConApp_maybe data_con_arg_ty2
+ Just (arg2_tycon,_) = maybe_arg2_tycon
+
+ other -> False
+
+creturnable_type ty = maybeToBool (maybeBoxedPrimType ty) ||
+ -- Or, a data type with a single nullary constructor
+ case (splitAlgTyConApp_maybe ty) of
+ Just (tycon, tys_applied, [data_con])
+ -> isNullaryDataCon data_con
+ other -> False
+\end{code}
-superClassSigCtxt sty
- = ppStr "When checking superclass constraints on instance declaration"
+\begin{code}
+instTypeErr clas tys msg
+ = sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys),
+ nest 4 (parens msg)
+ ]
+
+derivingWhenInstanceExistsErr clas tycon
+ = hang (hsep [ptext SLIT("Deriving class"),
+ quotes (ppr clas),
+ ptext SLIT("type"), quotes (ppr tycon)])
+ 4 (ptext SLIT("when an explicit instance exists"))
+
+nonBoxedPrimCCallErr clas inst_ty
+ = hang (ptext SLIT("Unacceptable instance type for ccall-ish class"))
+ 4 (hsep [ ptext SLIT("class"), ppr clas, ptext SLIT("type"),
+ ppr inst_ty])
+
+omittedMethodWarn sel_id clas
+ = sep [ptext SLIT("No explicit method nor default method for") <+> quotes (ppr sel_id),
+ ptext SLIT("in an instance declaration for") <+> quotes (ppr clas)]
+
+{-
+ Declaring CCallable & CReturnable instances in a module different
+ from where the type was defined. Caused by importing data type
+ abstractly (either programmatically or by the renamer being over-eager
+ in its pruning.)
+-}
+invisibleDataConPrimCCallErr clas inst_ty
+ = hang (hsep [ptext SLIT("Constructors for"), quotes (ppr inst_ty),
+ ptext SLIT("not visible when checking"),
+ quotes (ppr clas), ptext SLIT("instance")])
+ 4 (hsep [text "(Try either importing", ppr inst_ty,
+ text "non-abstractly or compile using -fno-prune-tydecls ..)"])
+
+methodCtxt = ptext SLIT("When checking the methods of an instance declaration")
+superClassCtxt = ptext SLIT("When checking the superclasses of an instance declaration")
\end{code}