%
+% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1996-1998
%
-\section[TcTyClsDecls]{Typecheck type and class declarations}
+
+TcTyClsDecls: Typecheck type and class declarations
\begin{code}
module TcTyClsDecls (
- tcTyAndClassDecls
+ tcTyAndClassDecls, kcDataDecl, tcConDecls, mkRecSelBinds,
+ checkValidTyCon, dataDeclChecks, badFamInstDecl
) where
#include "HsVersions.h"
-import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
- ConDecl(..), Sig(..), NewOrData(..), ResType(..),
- tyClDeclTyVars, isSynDecl, hsConArgs,
- LTyClDecl, tcdName, hsTyVarName, LHsTyVarBndr
- )
-import HsTypes ( HsBang(..), getBangStrictness )
-import BasicTypes ( RecFlag(..), StrictnessMark(..) )
-import HscTypes ( implicitTyThings, ModDetails )
-import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
- mkDataTyConRhs, mkNewTyConRhs )
+import HsSyn
+import HscTypes
+import BuildTyCl
+import TcUnify
import TcRnMonad
-import TcEnv ( TyThing(..),
- tcLookupLocated, tcLookupLocatedGlobal,
- tcExtendGlobalEnv, tcExtendKindEnv, tcExtendKindEnvTvs,
- tcExtendRecEnv, tcLookupTyVar )
-import TcTyDecls ( calcTyConArgVrcs, calcRecFlags, calcClassCycles, calcSynCycles )
-import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
-import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
- kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
- kcHsSigType, tcHsBangType, tcLHsConResTy, tcDataKindSig )
-import TcMType ( newKindVar, checkValidTheta, checkValidType,
- -- checkFreeness,
- UserTypeCtxt(..), SourceTyCtxt(..) )
-import TcType ( TcKind, TcType, tyVarsOfType, mkPhiTy,
- mkArrowKind, liftedTypeKind, mkTyVarTys,
- tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
-import Type ( splitTyConApp_maybe,
- -- pprParendType, pprThetaArrow
- )
-import Kind ( mkArrowKinds, splitKindFunTys )
-import Generics ( validGenericMethodType, canDoGenerics )
-import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
-import TyCon ( TyCon, ArgVrcs, AlgTyConRhs( AbstractTyCon ),
- tyConDataCons, mkForeignTyCon, isProductTyCon, isRecursiveTyCon,
- tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName )
-import DataCon ( DataCon, dataConWrapId, dataConName,
- dataConFieldLabels, dataConTyCon,
- dataConTyVars, dataConFieldType, dataConResTys )
-import Var ( TyVar, idType, idName )
-import VarSet ( elemVarSet, mkVarSet )
-import Name ( Name, getSrcLoc )
+import TcEnv
+import TcTyDecls
+import TcClassDcl
+import TcHsType
+import TcMType
+import TcType
+import TysWiredIn ( unitTy )
+import Type
+import Class
+import TyCon
+import DataCon
+import Id
+import MkCore ( rEC_SEL_ERROR_ID )
+import IdInfo
+import Var
+import VarSet
+import Name
+import NameEnv
import Outputable
-import Maybe ( isJust )
-import Maybes ( expectJust )
-import Unify ( tcMatchTys, tcMatchTyX )
-import Util ( zipLazy, isSingleton, notNull, sortLe )
-import List ( partition )
-import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
-import ListSetOps ( equivClasses )
-import List ( delete )
-import Digraph ( SCC(..) )
-import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
- Opt_UnboxStrictFields ) )
+import Maybes
+import Unify
+import Util
+import SrcLoc
+import ListSetOps
+import Digraph
+import DynFlags
+import FastString
+import Unique ( mkBuiltinUnique )
+import BasicTypes
+
+import Bag
+import Control.Monad
+import Data.List
\end{code}
%* *
%************************************************************************
-Dealing with a group
-~~~~~~~~~~~~~~~~~~~~
-Consider a mutually-recursive group, binding
-a type constructor T and a class C.
-
-Step 1: getInitialKind
- Construct a KindEnv by binding T and C to a kind variable
-
-Step 2: kcTyClDecl
- In that environment, do a kind check
-
-Step 3: Zonk the kinds
-
-Step 4: buildTyConOrClass
- Construct an environment binding T to a TyCon and C to a Class.
- a) Their kinds comes from zonking the relevant kind variable
- b) Their arity (for synonyms) comes direct from the decl
- c) The funcional dependencies come from the decl
- d) The rest comes a knot-tied binding of T and C, returned from Step 4
- e) The variances of the tycons in the group is calculated from
- the knot-tied stuff
-
-Step 5: tcTyClDecl1
- In this environment, walk over the decls, constructing the TyCons and Classes.
- This uses in a strict way items (a)-(c) above, which is why they must
- be constructed in Step 4. Feed the results back to Step 4.
- For this step, pass the is-recursive flag as the wimp-out flag
- to tcTyClDecl1.
-
-
-Step 6: Extend environment
- We extend the type environment with bindings not only for the TyCons and Classes,
- but also for their "implicit Ids" like data constructors and class selectors
-
-Step 7: checkValidTyCl
- For a recursive group only, check all the decls again, just
- to check all the side conditions on validity. We could not
- do this before because we were in a mutually recursive knot.
-
+\begin{code}
-The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
-@TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
+tcTyAndClassDecls :: ModDetails
+ -> [[LTyClDecl Name]] -- Mutually-recursive groups in dependency order
+ -> TcM (TcGblEnv, -- Input env extended by types and classes
+ -- and their implicit Ids,DataCons
+ HsValBinds Name) -- Renamed bindings for record selectors
+-- Fails if there are any errors
+
+tcTyAndClassDecls boot_details decls_s
+ = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
+ -- an error we'd better stop now, to avoid a cascade
+ do { let tyclds_s = map (filterOut (isFamInstDecl . unLoc)) decls_s
+ -- Remove family instance decls altogether
+ -- They are dealt with by TcInstDcls
+
+ ; tyclss <- fixM $ \ rec_tyclss ->
+ tcExtendRecEnv (zipRecTyClss tyclds_s rec_tyclss) $
+ -- We must populate the environment with the loop-tied
+ -- T's right away (even before kind checking), because
+ -- the kind checker may "fault in" some type constructors
+ -- that recursively mention T
+
+ do { -- Kind-check in dependency order
+ -- See Note [Kind checking for type and class decls]
+ kc_decls <- kcTyClDecls tyclds_s
+
+ -- And now build the TyCons/Classes
+ ; let rec_flags = calcRecFlags boot_details rec_tyclss
+ ; concatMapM (tcTyClDecl rec_flags) kc_decls }
+
+ ; tcExtendGlobalEnv tyclss $ do
+ { -- Perform the validity check
+ -- We can do this now because we are done with the recursive knot
+ traceTc "ready for validity check" empty
+ ; mapM_ (addLocM checkValidTyCl) (concat tyclds_s)
+ ; traceTc "done" empty
-\begin{code}
-tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
- -> TcM TcGblEnv -- Input env extended by types and classes
- -- and their implicit Ids,DataCons
-tcTyAndClassDecls boot_details decls
- = do { -- First check for cyclic type synonysm or classes
- -- See notes with checkCycleErrs
- checkCycleErrs decls
- ; mod <- getModule
- ; traceTc (text "tcTyAndCl" <+> ppr mod)
- ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
- do { let { -- Calculate variances and rec-flag
- ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
-
- -- Extend the global env with the knot-tied results
- -- for data types and classes
- --
- -- We must populate the environment with the loop-tied T's right
- -- away, because the kind checker may "fault in" some type
- -- constructors that recursively mention T
- ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
- ; tcExtendRecEnv gbl_things $ do
-
- -- Kind-check the declarations
- { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
-
- ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
- ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
- ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
- -- Type-check the type synonyms, and extend the envt
- ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
- ; tcExtendGlobalEnv syn_tycons $ do
-
- -- Type-check the data types and classes
- { alg_tyclss <- mappM tc_decl kc_alg_decls
- ; return (syn_tycons, alg_tyclss)
- }}})
- -- Finished with knot-tying now
- -- Extend the environment with the finished things
- ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
-
- -- Perform the validity check
- { traceTc (text "ready for validity check")
- ; mappM_ (addLocM checkValidTyCl) decls
- ; traceTc (text "done")
-
-- Add the implicit things;
- -- we want them in the environment because
+ -- we want them in the environment because
-- they may be mentioned in interface files
- ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
- ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
- ; tcExtendGlobalEnv implicit_things getGblEnv
- }}
-
-mkGlobalThings :: [LTyClDecl Name] -- The decls
- -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
- -> [(Name,TyThing)]
--- Driven by the Decls, and treating the TyThings lazily
--- make a TypeEnv for the new things
-mkGlobalThings decls things
- = map mk_thing (decls `zipLazy` things)
+ -- NB: All associated types and their implicit things will be added a
+ -- second time here. This doesn't matter as the definitions are
+ -- the same.
+ ; let { implicit_things = concatMap implicitTyThings tyclss
+ ; rec_sel_binds = mkRecSelBinds [tc | ATyCon tc <- tyclss]
+ ; dm_ids = mkDefaultMethodIds tyclss }
+
+ ; env <- tcExtendGlobalEnv implicit_things $
+ tcExtendGlobalValEnv dm_ids $
+ getGblEnv
+ ; return (env, rec_sel_binds) } }
+
+zipRecTyClss :: [[LTyClDecl Name]]
+ -> [TyThing] -- Knot-tied
+ -> [(Name,TyThing)]
+-- Build a name-TyThing mapping for the things bound by decls
+-- being careful not to look at the [TyThing]
+-- The TyThings in the result list must have a visible ATyCon/AClass,
+-- because typechecking types (in, say, tcTyClDecl) looks at this outer constructor
+zipRecTyClss decls_s rec_things
+ = [ get decl | decls <- decls_s, L _ decl <- flattenATs decls ]
where
- mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
- = (name, AClass cl)
- mk_thing (L _ decl, ~(ATyCon tc))
- = (tcdName decl, ATyCon tc)
+ rec_type_env :: TypeEnv
+ rec_type_env = mkTypeEnv rec_things
+
+ get :: TyClDecl Name -> (Name, TyThing)
+ get (ClassDecl {tcdLName = L _ name}) = (name, AClass cl)
+ where
+ Just (AClass cl) = lookupTypeEnv rec_type_env name
+ get decl = (name, ATyCon tc)
+ where
+ name = tcdName decl
+ Just (ATyCon tc) = lookupTypeEnv rec_type_env name
\end{code}
%* *
%************************************************************************
+Note [Kind checking for type and class decls]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Kind checking is done thus:
+
+ 1. Make up a kind variable for each parameter of the *data* type,
+ and class, decls, and extend the kind environment (which is in
+ the TcLclEnv)
+
+ 2. Dependency-analyse the type *synonyms* (which must be non-recursive),
+ and kind-check them in dependency order. Extend the kind envt.
+
+ 3. Kind check the data type and class decls
+
+Synonyms are treated differently to data type and classes,
+because a type synonym can be an unboxed type
+ type Foo = Int#
+and a kind variable can't unify with UnboxedTypeKind
+So we infer their kinds in dependency order
+
We need to kind check all types in the mutually recursive group
before we know the kind of the type variables. For example:
use them, whereas for the mutually recursive data types D we bring into
scope kind bindings D -> k, where k is a kind variable, and do inference.
+Type families
+~~~~~~~~~~~~~
+This treatment of type synonyms only applies to Haskell 98-style synonyms.
+General type functions can be recursive, and hence, appear in `alg_decls'.
+
+The kind of a type family is solely determinded by its kind signature;
+hence, only kind signatures participate in the construction of the initial
+kind environment (as constructed by `getInitialKind'). In fact, we ignore
+instances of families altogether in the following. However, we need to
+include the kinds of associated families into the construction of the
+initial kind environment. (This is handled by `allDecls').
+
+
\begin{code}
-kcTyClDecls syn_decls alg_decls
- = do { -- First extend the kind env with each data
- -- type and class, mapping them to a type variable
- alg_kinds <- mappM getInitialKind alg_decls
- ; tcExtendKindEnv alg_kinds $ do
-
- -- Now kind-check the type synonyms, in dependency order
- -- We do these differently to data type and classes,
- -- because a type synonym can be an unboxed type
- -- type Foo = Int#
- -- and a kind variable can't unify with UnboxedTypeKind
- -- So we infer their kinds in dependency order
- { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
- ; tcExtendKindEnv syn_kinds $ do
-
- -- Now kind-check the data type and class declarations,
- -- returning kind-annotated decls
- { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
-
- ; return (kc_syn_decls, kc_alg_decls) }}}
+kcTyClDecls :: [[LTyClDecl Name]] -> TcM [LTyClDecl Name]
+kcTyClDecls [] = return []
+kcTyClDecls (decls : decls_s) = do { (tcl_env, kc_decls1) <- kcTyClDecls1 decls
+ ; kc_decls2 <- setLclEnv tcl_env (kcTyClDecls decls_s)
+ ; return (kc_decls1 ++ kc_decls2) }
+
+kcTyClDecls1 :: [LTyClDecl Name] -> TcM (TcLclEnv, [LTyClDecl Name])
+kcTyClDecls1 decls
+ = do { -- Omit instances of type families; they are handled together
+ -- with the *heads* of class instances
+ ; let (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls
+ alg_at_decls = flattenATs alg_decls
+
+ ; mod <- getModule
+ ; traceTc "tcTyAndCl" (ptext (sLit "module") <+> ppr mod $$ vcat (map ppr decls))
+
+ -- First check for cyclic classes
+ ; checkClassCycleErrs alg_decls
+
+ -- Kind checking; see Note [Kind checking for type and class decls]
+ ; alg_kinds <- mapM getInitialKind alg_at_decls
+ ; tcExtendKindEnv alg_kinds $ do
+
+ { (kc_syn_decls, tcl_env) <- kcSynDecls (calcSynCycles syn_decls)
+ ; setLclEnv tcl_env $ do
+ { kc_alg_decls <- mapM (wrapLocM kcTyClDecl) alg_decls
+
+ -- Kind checking done for this group, so zonk the kind variables
+ -- See Note [Kind checking for type and class decls]
+ ; mapM_ (zonkTcKindToKind . snd) alg_kinds
+
+ ; return (tcl_env, kc_syn_decls ++ kc_alg_decls) } } }
+
+flattenATs :: [LTyClDecl Name] -> [LTyClDecl Name]
+flattenATs decls = concatMap flatten decls
+ where
+ flatten decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
+ flatten decl = [decl]
-------------------------------------------------------------------------
getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
--- Only for data type and class declarations
--- Get as much info as possible from the data or class decl,
+-- Only for data type, class, and indexed type declarations
+-- Get as much info as possible from the data, class, or indexed type decl,
-- so as to maximise usefulness of error messages
getInitialKind (L _ decl)
= do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
; res_kind <- mk_res_kind decl
; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
where
- mk_arg_kind (UserTyVar _) = newKindVar
+ mk_arg_kind (UserTyVar _ _) = newKindVar
mk_arg_kind (KindedTyVar _ kind) = return kind
- mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
+ mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
+ mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
-- On GADT-style declarations we allow a kind signature
-- data T :: *->* where { ... }
- mk_res_kind other = return liftedTypeKind
+ mk_res_kind _ = return liftedTypeKind
----------------
kcSynDecls :: [SCC (LTyClDecl Name)]
-> TcM ([LTyClDecl Name], -- Kind-annotated decls
- [(Name,TcKind)]) -- Kind bindings
+ TcLclEnv) -- Kind bindings
kcSynDecls []
- = return ([], [])
+ = do { tcl_env <- getLclEnv; return ([], tcl_env) }
kcSynDecls (group : groups)
- = do { (decl, nk) <- kcSynDecl group
- ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
- ; return (decl:decls, nk:nks) }
+ = do { (decl, nk) <- kcSynDecl group
+ ; (decls, tcl_env) <- tcExtendKindEnv [nk] (kcSynDecls groups)
+ ; return (decl:decls, tcl_env) }
----------------
kcSynDecl :: SCC (LTyClDecl Name)
-> TcM (LTyClDecl Name, -- Kind-annotated decls
(Name,TcKind)) -- Kind bindings
-kcSynDecl (AcyclicSCC ldecl@(L loc decl))
+kcSynDecl (AcyclicSCC (L loc decl))
= tcAddDeclCtxt decl $
kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
- do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
+ do { traceTc "kcd1" (ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
<+> brackets (ppr k_tvs))
- ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
- ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
- ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
+ ; (k_rhs, rhs_kind) <- kcLHsType (tcdSynRhs decl)
+ ; traceTc "kcd2" (ppr (unLoc (tcdLName decl)))
+ ; let tc_kind = foldr (mkArrowKind . hsTyVarKind . unLoc) rhs_kind k_tvs
; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
(unLoc (tcdLName decl), tc_kind)) })
= do { recSynErr decls; failM } -- Fail here to avoid error cascade
-- of out-of-scope tycons
-kindedTyVarKind (L _ (KindedTyVar _ k)) = k
-
------------------------------------------------------------------------
kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
-- Not used for type synonyms (see kcSynDecl)
-kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
- = kcTyClDeclBody decl $ \ tvs' ->
- do { ctxt' <- kcHsContext ctxt
- ; cons' <- mappM (wrapLocM kc_con_decl) cons
- ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
- where
- kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
- kcHsTyVars ex_tvs $ \ex_tvs' -> do
- ex_ctxt' <- kcHsContext ex_ctxt
- details' <- kc_con_details details
- res' <- case res of
- ResTyH98 -> return ResTyH98
- ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
- return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
-
- kc_con_details (PrefixCon btys)
- = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
- kc_con_details (InfixCon bty1 bty2)
- = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
- kc_con_details (RecCon fields)
- = do { fields' <- mappM kc_field fields; return (RecCon fields') }
-
- kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
+kcTyClDecl decl@(TyData {})
+ = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
+ kcTyClDeclBody decl $
+ kcDataDecl decl
- kc_larg_ty bty = case new_or_data of
- DataType -> kcHsSigType bty
- NewType -> kcHsLiftedSigType bty
- -- Can't allow an unlifted type for newtypes, because we're effectively
- -- going to remove the constructor while coercing it to a lifted type.
- -- And newtypes can't be bang'd
+kcTyClDecl decl@(TyFamily {})
+ = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
-kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
+kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
= kcTyClDeclBody decl $ \ tvs' ->
- do { is_boot <- tcIsHsBoot
- ; ctxt' <- kcHsContext ctxt
- ; sigs' <- mappM (wrapLocM kc_sig) sigs
- ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
+ do { ctxt' <- kcHsContext ctxt
+ ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
+ ; sigs' <- mapM (wrapLocM kc_sig) sigs
+ ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
+ tcdATs = ats'}) }
where
kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
; return (TypeSig nm op_ty') }
+ kc_sig (GenericSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
+ ; return (GenericSig nm op_ty') }
kc_sig other_sig = return other_sig
kcTyClDecl decl@(ForeignType {})
= return decl
+kcTyClDecl (TySynonym {}) = panic "kcTyClDecl TySynonym"
+
kcTyClDeclBody :: TyClDecl Name
-> ([LHsTyVarBndr Name] -> TcM a)
-> TcM a
-- Unpack it, and attribute those kinds to the type variables
-- Extend the env with bindings for the tyvars, taken from
-- the kind of the tycon/class. Give it to the thing inside, and
- -- check the result kind matches
+-- check the result kind matches
kcTyClDeclBody decl thing_inside
= tcAddDeclCtxt decl $
do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
- ; let tc_kind = case tc_ty_thing of { AThing k -> k }
+ ; let tc_kind = case tc_ty_thing of
+ AThing k -> k
+ _ -> pprPanic "kcTyClDeclBody" (ppr tc_ty_thing)
(kinds, _) = splitKindFunTys tc_kind
hs_tvs = tcdTyVars decl
kinded_tvs = ASSERT( length kinds >= length hs_tvs )
- [ L loc (KindedTyVar (hsTyVarName tv) k)
- | (L loc tv, k) <- zip hs_tvs kinds]
- ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
+ zipWith add_kind hs_tvs kinds
+ ; tcExtendKindEnvTvs kinded_tvs thing_inside }
+ where
+ add_kind (L loc (UserTyVar n _)) k = L loc (UserTyVar n k)
+ add_kind (L loc (KindedTyVar n _)) k = L loc (KindedTyVar n k)
+
+-- Kind check a data declaration, assuming that we already extended the
+-- kind environment with the type variables of the left-hand side (these
+-- kinded type variables are also passed as the second parameter).
+--
+kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
+kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
+ tvs
+ = do { ctxt' <- kcHsContext ctxt
+ ; cons' <- mapM (wrapLocM kc_con_decl) cons
+ ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
+ where
+ -- doc comments are typechecked to Nothing here
+ kc_con_decl con_decl@(ConDecl { con_name = name, con_qvars = ex_tvs
+ , con_cxt = ex_ctxt, con_details = details, con_res = res })
+ = addErrCtxt (dataConCtxt name) $
+ kcHsTyVars ex_tvs $ \ex_tvs' -> do
+ do { ex_ctxt' <- kcHsContext ex_ctxt
+ ; details' <- kc_con_details details
+ ; res' <- case res of
+ ResTyH98 -> return ResTyH98
+ ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
+ ; return (con_decl { con_qvars = ex_tvs', con_cxt = ex_ctxt'
+ , con_details = details', con_res = res' }) }
+
+ kc_con_details (PrefixCon btys)
+ = do { btys' <- mapM kc_larg_ty btys
+ ; return (PrefixCon btys') }
+ kc_con_details (InfixCon bty1 bty2)
+ = do { bty1' <- kc_larg_ty bty1
+ ; bty2' <- kc_larg_ty bty2
+ ; return (InfixCon bty1' bty2') }
+ kc_con_details (RecCon fields)
+ = do { fields' <- mapM kc_field fields
+ ; return (RecCon fields') }
+
+ kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
+ ; return (ConDeclField fld bty' d) }
+
+ kc_larg_ty bty = case new_or_data of
+ DataType -> kcHsSigType bty
+ NewType -> kcHsLiftedSigType bty
+ -- Can't allow an unlifted type for newtypes, because we're effectively
+ -- going to remove the constructor while coercing it to a lifted type.
+ -- And newtypes can't be bang'd
+kcDataDecl d _ = pprPanic "kcDataDecl" (ppr d)
+
+-- Kind check a family declaration or type family default declaration.
+--
+kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
+ -> TyClDecl Name -> TcM (TyClDecl Name)
+kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
+ = kcTyClDeclBody decl $ \tvs' ->
+ do { mapM_ unifyClassParmKinds tvs'
+ ; return (decl {tcdTyVars = tvs',
+ tcdKind = kind `mplus` Just liftedTypeKind})
+ -- default result kind is '*'
+ }
+ where
+ unifyClassParmKinds (L _ tv)
+ | (n,k) <- hsTyVarNameKind tv
+ , Just classParmKind <- lookup n classTyKinds
+ = unifyKind k classParmKind
+ | otherwise = return ()
+ classTyKinds = [hsTyVarNameKind tv | L _ tv <- classTvs]
+
+kcFamilyDecl _ (TySynonym {}) -- type family defaults
+ = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
+kcFamilyDecl _ d = pprPanic "kcFamilyDecl" (ppr d)
\end{code}
%************************************************************************
\begin{code}
-tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
-tcSynDecls calc_vrcs [] = return []
-tcSynDecls calc_vrcs (decl : decls)
- = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
- ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
- ; return (syn_tc : syn_tcs) }
-
-tcSynDecl calc_vrcs
- (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
- = tcTyVarBndrs tvs $ \ tvs' -> do
- { traceTc (text "tcd1" <+> ppr tc_name)
- ; rhs_ty' <- tcHsKindedType rhs_ty
- ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
+tcTyClDecl :: (Name -> RecFlag) -> LTyClDecl Name -> TcM [TyThing]
+
+tcTyClDecl calc_isrec (L loc decl)
+ = setSrcSpan loc $ tcAddDeclCtxt decl $
+ tcTyClDecl1 NoParentTyCon calc_isrec decl
+
+ -- "type family" declarations
+tcTyClDecl1 :: TyConParent -> (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
+tcTyClDecl1 parent _calc_isrec
+ (TyFamily {tcdFlavour = TypeFamily,
+ tcdLName = L _ tc_name, tcdTyVars = tvs,
+ tcdKind = Just kind}) -- NB: kind at latest added during kind checking
+ = tcTyVarBndrs tvs $ \ tvs' -> do
+ { traceTc "type family:" (ppr tc_name)
+
+ -- Check that we don't use families without -XTypeFamilies
+ ; idx_tys <- xoptM Opt_TypeFamilies
+ ; checkTc idx_tys $ badFamInstDecl tc_name
+
+ ; tycon <- buildSynTyCon tc_name tvs' SynFamilyTyCon kind parent Nothing
+ ; return [ATyCon tycon]
+ }
+
+ -- "data family" declaration
+tcTyClDecl1 parent _calc_isrec
+ (TyFamily {tcdFlavour = DataFamily,
+ tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
+ = tcTyVarBndrs tvs $ \ tvs' -> do
+ { traceTc "data family:" (ppr tc_name)
+ ; extra_tvs <- tcDataKindSig mb_kind
+ ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
---------------------
-tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
- -> TyClDecl Name -> TcM TyThing
-tcTyClDecl calc_vrcs calc_isrec decl
- = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
+ -- Check that we don't use families without -XTypeFamilies
+ ; idx_tys <- xoptM Opt_TypeFamilies
+ ; checkTc idx_tys $ badFamInstDecl tc_name
-tcTyClDecl1 calc_vrcs calc_isrec
+ ; tycon <- buildAlgTyCon tc_name final_tvs []
+ DataFamilyTyCon Recursive True
+ parent Nothing
+ ; return [ATyCon tycon]
+ }
+
+ -- "type"
+tcTyClDecl1 _parent _calc_isrec
+ (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
+ = ASSERT( isNoParent _parent )
+ tcTyVarBndrs tvs $ \ tvs' -> do
+ { traceTc "tcd1" (ppr tc_name)
+ ; rhs_ty' <- tcHsKindedType rhs_ty
+ ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty')
+ (typeKind rhs_ty') NoParentTyCon Nothing
+ ; return [ATyCon tycon] }
+
+ -- "newtype" and "data"
+ -- NB: not used for newtype/data instances (whether associated or not)
+tcTyClDecl1 _parent calc_isrec
(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
- = tcTyVarBndrs tvs $ \ tvs' -> do
+ = ASSERT( isNoParent _parent )
+ tcTyVarBndrs tvs $ \ tvs' -> do
{ extra_tvs <- tcDataKindSig mb_ksig
; let final_tvs = tvs' ++ extra_tvs
; stupid_theta <- tcHsKindedContext ctxt
- ; want_generic <- doptM Opt_Generics
- ; unbox_strict <- doptM Opt_UnboxStrictFields
- ; gla_exts <- doptM Opt_GlasgowExts
+ ; kind_signatures <- xoptM Opt_KindSignatures
+ ; existential_ok <- xoptM Opt_ExistentialQuantification
+ ; gadt_ok <- xoptM Opt_GADTs
; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
+ ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
- -- Check that we don't use GADT syntax in H98 world
- ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
+ -- Check that we don't use kind signatures without Glasgow extensions
+ ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
- -- Check that there's at least one condecl,
- -- or else we're reading an interface file, or -fglasgow-exts
- ; checkTc (not (null cons) || gla_exts || is_boot)
- (emptyConDeclsErr tc_name)
-
- -- Check that a newtype has exactly one constructor
- ; checkTc (new_or_data == DataType || isSingleton cons)
- (newtypeConError tc_name (length cons))
+ ; dataDeclChecks tc_name new_or_data stupid_theta cons
; tycon <- fixM (\ tycon -> do
- { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
- tycon final_tvs))
- cons
- ; let tc_rhs
- | null cons && is_boot -- In a hs-boot file, empty cons means
- = AbstractTyCon -- "don't know"; hence Abstract
- | otherwise
- = case new_or_data of
- DataType -> mkDataTyConRhs data_cons
- NewType -> ASSERT( isSingleton data_cons )
- mkNewTyConRhs tycon (head data_cons)
- ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
- (want_generic && canDoGenerics data_cons)
+ { let res_ty = mkTyConApp tycon (mkTyVarTys final_tvs)
+ ; data_cons <- tcConDecls ex_ok tycon (final_tvs, res_ty) cons
+ ; tc_rhs <-
+ if null cons && is_boot -- In a hs-boot file, empty cons means
+ then return AbstractTyCon -- "don't know"; hence Abstract
+ else case new_or_data of
+ DataType -> return (mkDataTyConRhs data_cons)
+ NewType -> ASSERT( not (null data_cons) )
+ mkNewTyConRhs tc_name tycon (head data_cons)
+ ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
+ (not h98_syntax) NoParentTyCon Nothing
})
- ; return (ATyCon tycon)
+ ; return [ATyCon tycon]
}
where
- arg_vrcs = calc_vrcs tc_name
is_rec = calc_isrec tc_name
- h98_syntax = case cons of -- All constructors have same shape
- L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
- other -> True
+ h98_syntax = consUseH98Syntax cons
-tcTyClDecl1 calc_vrcs calc_isrec
+tcTyClDecl1 _parent calc_isrec
(ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
tcdCtxt = ctxt, tcdMeths = meths,
- tcdFDs = fundeps, tcdSigs = sigs} )
- = tcTyVarBndrs tvs $ \ tvs' -> do
+ tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
+ = ASSERT( isNoParent _parent )
+ tcTyVarBndrs tvs $ \ tvs' -> do
{ ctxt' <- tcHsKindedContext ctxt
- ; fds' <- mappM (addLocM tc_fundep) fundeps
- ; sig_stuff <- tcClassSigs class_name sigs meths
- ; clas <- fixM (\ clas ->
- let -- This little knot is just so we can get
+ ; fds' <- mapM (addLocM tc_fundep) fundeps
+ ; (sig_stuff, gen_dm_env) <- tcClassSigs class_name sigs meths
+ ; clas <- fixM $ \ clas -> do
+ { let -- This little knot is just so we can get
-- hold of the name of the class TyCon, which we
- -- need to look up its recursiveness and variance
+ -- need to look up its recursiveness
tycon_name = tyConName (classTyCon clas)
tc_isrec = calc_isrec tycon_name
- tc_vrcs = calc_vrcs tycon_name
- in
- buildClass class_name tvs' ctxt' fds'
- sig_stuff tc_isrec tc_vrcs)
- ; return (AClass clas) }
+ ; atss' <- mapM (addLocM $ tcTyClDecl1 (AssocFamilyTyCon clas) (const Recursive)) ats
+ -- NB: 'ats' only contains "type family" and "data family"
+ -- declarations as well as type family defaults
+ ; buildClass False {- Must include unfoldings for selectors -}
+ class_name tvs' ctxt' fds' (concat atss')
+ sig_stuff tc_isrec }
+
+ ; let gen_dm_ids = [ AnId (mkExportedLocalId gen_dm_name gen_dm_ty)
+ | (sel_id, GenDefMeth gen_dm_name) <- classOpItems clas
+ , let gen_dm_tau = expectJust "tcTyClDecl1" $
+ lookupNameEnv gen_dm_env (idName sel_id)
+ , let gen_dm_ty = mkSigmaTy tvs'
+ [mkClassPred clas (mkTyVarTys tvs')]
+ gen_dm_tau
+ ]
+ class_ats = map ATyCon (classATs clas)
+
+ ; return (AClass clas : gen_dm_ids ++ class_ats )
+ -- NB: Order is important due to the call to `mkGlobalThings' when
+ -- tying the the type and class declaration type checking knot.
+ }
where
- tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
- ; tvs2' <- mappM tcLookupTyVar tvs2 ;
+ tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
+ ; tvs2' <- mapM tcLookupTyVar tvs2 ;
; return (tvs1', tvs2') }
-
-tcTyClDecl1 calc_vrcs calc_isrec
+tcTyClDecl1 _ _
(ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
- = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
+ = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
------------------------------------
-tcConDecl :: Bool -- True <=> -funbox-strict_fields
- -> NewOrData -> TyCon -> [TyVar]
- -> ConDecl Name -> TcM DataCon
-
-tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
- (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
- = do { let tc_datacon field_lbls arg_ty
- = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
- ; buildDataCon (unLoc name) False {- Prefix -}
- True {- Vanilla -} [NotMarkedStrict]
- (map unLoc field_lbls)
- tc_tvs [] [arg_ty']
- tycon (mkTyVarTys tc_tvs) }
-
- -- Check that a newtype has no existential stuff
- ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
-
- ; case details of
- PrefixCon [arg_ty] -> tc_datacon [] arg_ty
- RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
- other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
- -- Check that the constructor has exactly one field
- }
+tcTyClDecl1 _ _ d = pprPanic "tcTyClDecl1" (ppr d)
-tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
- (ConDecl name _ tvs ctxt details res_ty)
- = tcTyVarBndrs tvs $ \ tvs' -> do
- { ctxt' <- tcHsKindedContext ctxt
- ; (data_tc, res_ty_args) <- tcResultType tycon tc_tvs res_ty
- ; let
- con_tvs = case res_ty of
- ResTyH98 -> tc_tvs ++ tvs'
- ResTyGADT _ -> tryVanilla tvs' res_ty_args
+dataDeclChecks :: Name -> NewOrData -> ThetaType -> [LConDecl Name] -> TcM ()
+dataDeclChecks tc_name new_or_data stupid_theta cons
+ = do { -- Check that we don't use GADT syntax in H98 world
+ gadtSyntax_ok <- xoptM Opt_GADTSyntax
+ ; let h98_syntax = consUseH98Syntax cons
+ ; checkTc (gadtSyntax_ok || h98_syntax) (badGadtDecl tc_name)
- -- Vanilla iff result type matches the quantified vars exactly,
- -- and there is no existential context
- -- Must check the context too because of implicit params; e.g.
- -- data T = (?x::Int) => MkT Int
- is_vanilla = res_ty_args `tcEqTypes` mkTyVarTys con_tvs
- && null (unLoc ctxt)
+ -- Check that the stupid theta is empty for a GADT-style declaration
+ ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
+ -- Check that a newtype has exactly one constructor
+ -- Do this before checking for empty data decls, so that
+ -- we don't suggest -XEmptyDataDecls for newtypes
+ ; checkTc (new_or_data == DataType || isSingleton cons)
+ (newtypeConError tc_name (length cons))
+
+ -- Check that there's at least one condecl,
+ -- or else we're reading an hs-boot file, or -XEmptyDataDecls
+ ; empty_data_decls <- xoptM Opt_EmptyDataDecls
+ ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
+ ; checkTc (not (null cons) || empty_data_decls || is_boot)
+ (emptyConDeclsErr tc_name) }
+
+-----------------------------------
+tcConDecls :: Bool -> TyCon -> ([TyVar], Type)
+ -> [LConDecl Name] -> TcM [DataCon]
+tcConDecls ex_ok rep_tycon res_tmpl cons
+ = mapM (addLocM (tcConDecl ex_ok rep_tycon res_tmpl)) cons
+
+tcConDecl :: Bool -- True <=> -XExistentialQuantificaton or -XGADTs
+ -> TyCon -- Representation tycon
+ -> ([TyVar], Type) -- Return type template (with its template tyvars)
+ -> ConDecl Name
+ -> TcM DataCon
+
+tcConDecl existential_ok rep_tycon res_tmpl -- Data types
+ con@(ConDecl {con_name = name, con_qvars = tvs, con_cxt = ctxt
+ , con_details = details, con_res = res_ty })
+ = addErrCtxt (dataConCtxt name) $
+ tcTyVarBndrs tvs $ \ tvs' -> do
+ { ctxt' <- tcHsKindedContext ctxt
+ ; checkTc (existential_ok || conRepresentibleWithH98Syntax con)
+ (badExistential name)
+ ; (univ_tvs, ex_tvs, eq_preds, res_ty') <- tcResultType res_tmpl tvs' res_ty
+ ; let
tc_datacon is_infix field_lbls btys
- = do { let bangs = map getBangStrictness btys
- ; arg_tys <- mappM tcHsBangType btys
- ; buildDataCon (unLoc name) is_infix is_vanilla
- (argStrictness unbox_strict tycon bangs arg_tys)
- (map unLoc field_lbls)
- con_tvs ctxt' arg_tys
- data_tc res_ty_args }
- -- NB: we put data_tc, the type constructor gotten from the constructor
- -- type signature into the data constructor; that way
- -- checkValidDataCon can complain if it's wrong.
+ = do { (arg_tys, stricts) <- mapAndUnzipM tcConArg btys
+ ; buildDataCon (unLoc name) is_infix
+ stricts field_lbls
+ univ_tvs ex_tvs eq_preds ctxt' arg_tys
+ res_ty' rep_tycon }
+ -- NB: we put data_tc, the type constructor gotten from the
+ -- constructor type signature into the data constructor;
+ -- that way checkValidDataCon can complain if it's wrong.
; case details of
PrefixCon btys -> tc_datacon False [] btys
InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
RecCon fields -> tc_datacon False field_names btys
where
- (field_names, btys) = unzip fields
-
+ field_names = map (unLoc . cd_fld_name) fields
+ btys = map cd_fld_type fields
}
-tcResultType :: TyCon -> [TyVar] -> ResType Name -> TcM (TyCon, [TcType])
-tcResultType tycon tvs ResTyH98 = return (tycon, mkTyVarTys tvs)
-tcResultType _ _ (ResTyGADT res_ty) = tcLHsConResTy res_ty
-
-tryVanilla :: [TyVar] -> [TcType] -> [TyVar]
--- (tryVanilla tvs tys) returns a permutation of tvs.
--- It tries to re-order the tvs so that it exactly
--- matches the [Type], if that is possible
-tryVanilla tvs (ty:tys) | Just tv <- tcGetTyVar_maybe ty -- The type is a tyvar
- , tv `elem` tvs -- That tyvar is in the list
- = tv : tryVanilla (delete tv tvs) tys
-tryVanilla tvs tys = tvs -- Fall through case
-
+-- Example
+-- data instance T (b,c) where
+-- TI :: forall e. e -> T (e,e)
+--
+-- The representation tycon looks like this:
+-- data :R7T b c where
+-- TI :: forall b1 c1. (b1 ~ c1) => b1 -> :R7T b1 c1
+-- In this case orig_res_ty = T (e,e)
+
+tcResultType :: ([TyVar], Type) -- Template for result type; e.g.
+ -- data instance T [a] b c = ...
+ -- gives template ([a,b,c], T [a] b c)
+ -> [TyVar] -- where MkT :: forall x y z. ...
+ -> ResType Name
+ -> TcM ([TyVar], -- Universal
+ [TyVar], -- Existential (distinct OccNames from univs)
+ [(TyVar,Type)], -- Equality predicates
+ Type) -- Typechecked return type
+ -- We don't check that the TyCon given in the ResTy is
+ -- the same as the parent tycon, becuase we are in the middle
+ -- of a recursive knot; so it's postponed until checkValidDataCon
+
+tcResultType (tmpl_tvs, res_ty) dc_tvs ResTyH98
+ = return (tmpl_tvs, dc_tvs, [], res_ty)
+ -- In H98 syntax the dc_tvs are the existential ones
+ -- data T a b c = forall d e. MkT ...
+ -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
+
+tcResultType (tmpl_tvs, res_tmpl) dc_tvs (ResTyGADT res_ty)
+ -- E.g. data T [a] b c where
+ -- MkT :: forall x y z. T [(x,y)] z z
+ -- Then we generate
+ -- Univ tyvars Eq-spec
+ -- a a~(x,y)
+ -- b b~z
+ -- z
+ -- Existentials are the leftover type vars: [x,y]
+ -- So we return ([a,b,z], [x,y], [a~(x,y),b~z], T [(x,y)] z z)
+ = do { res_ty' <- tcHsKindedType res_ty
+ ; let Just subst = tcMatchTy (mkVarSet tmpl_tvs) res_tmpl res_ty'
+
+ -- /Lazily/ figure out the univ_tvs etc
+ -- Each univ_tv is either a dc_tv or a tmpl_tv
+ (univ_tvs, eq_spec) = foldr choose ([], []) tidy_tmpl_tvs
+ choose tmpl (univs, eqs)
+ | Just ty <- lookupTyVar subst tmpl
+ = case tcGetTyVar_maybe ty of
+ Just tv | not (tv `elem` univs)
+ -> (tv:univs, eqs)
+ _other -> (tmpl:univs, (tmpl,ty):eqs)
+ | otherwise = pprPanic "tcResultType" (ppr res_ty)
+ ex_tvs = dc_tvs `minusList` univ_tvs
+
+ ; return (univ_tvs, ex_tvs, eq_spec, res_ty') }
+ where
+ -- NB: tmpl_tvs and dc_tvs are distinct, but
+ -- we want them to be *visibly* distinct, both for
+ -- interface files and general confusion. So rename
+ -- the tc_tvs, since they are not used yet (no
+ -- consequential renaming needed)
+ (_, tidy_tmpl_tvs) = mapAccumL tidy_one init_occ_env tmpl_tvs
+ init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
+ tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
+ where
+ name = tyVarName tv
+ (env', occ') = tidyOccName env (getOccName name)
+
+consUseH98Syntax :: [LConDecl a] -> Bool
+consUseH98Syntax (L _ (ConDecl { con_res = ResTyGADT _ }) : _) = False
+consUseH98Syntax _ = True
+ -- All constructors have same shape
+
+conRepresentibleWithH98Syntax :: ConDecl Name -> Bool
+conRepresentibleWithH98Syntax
+ (ConDecl {con_qvars = tvs, con_cxt = ctxt, con_res = ResTyH98 })
+ = null tvs && null (unLoc ctxt)
+conRepresentibleWithH98Syntax
+ (ConDecl {con_qvars = tvs, con_cxt = ctxt, con_res = ResTyGADT (L _ t) })
+ = null (unLoc ctxt) && f t (map (hsTyVarName . unLoc) tvs)
+ where -- Each type variable should be used exactly once in the
+ -- result type, and the result type must just be the type
+ -- constructor applied to type variables
+ f (HsAppTy (L _ t1) (L _ (HsTyVar v2))) vs
+ = (v2 `elem` vs) && f t1 (delete v2 vs)
+ f (HsTyVar _) [] = True
+ f _ _ = False
-------------------
-argStrictness :: Bool -- True <=> -funbox-strict_fields
- -> TyCon -> [HsBang]
- -> [TcType] -> [StrictnessMark]
-argStrictness unbox_strict tycon bangs arg_tys
- = ASSERT( length bangs == length arg_tys )
- zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
+tcConArg :: LHsType Name -> TcM (TcType, HsBang)
+tcConArg bty
+ = do { arg_ty <- tcHsBangType bty
+ ; strict_mark <- chooseBoxingStrategy arg_ty (getBangStrictness bty)
+ ; return (arg_ty, strict_mark) }
-- We attempt to unbox/unpack a strict field when either:
-- (i) The field is marked '!!', or
-- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
-
-chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
-chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
+--
+-- We have turned off unboxing of newtypes because coercions make unboxing
+-- and reboxing more complicated
+chooseBoxingStrategy :: TcType -> HsBang -> TcM HsBang
+chooseBoxingStrategy arg_ty bang
= case bang of
- HsNoBang -> NotMarkedStrict
- HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
- HsUnbox | can_unbox -> MarkedUnboxed
- other -> MarkedStrict
+ HsNoBang -> return HsNoBang
+ HsStrict -> do { unbox_strict <- doptM Opt_UnboxStrictFields
+ ; if unbox_strict then return (can_unbox HsStrict arg_ty)
+ else return HsStrict }
+ HsUnpack -> do { omit_prags <- doptM Opt_OmitInterfacePragmas
+ -- Do not respect UNPACK pragmas if OmitInterfacePragmas is on
+ -- See Trac #5252: unpacking means we must not conceal the
+ -- representation of the argument type
+ ; if omit_prags then return HsStrict
+ else return (can_unbox HsUnpackFailed arg_ty) }
+ HsUnpackFailed -> pprPanic "chooseBoxingStrategy" (ppr arg_ty)
+ -- Source code never has shtes
where
- can_unbox = case splitTyConApp_maybe arg_ty of
- Nothing -> False
- Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
- isProductTyCon arg_tycon
+ can_unbox :: HsBang -> TcType -> HsBang
+ -- Returns HsUnpack if we can unpack arg_ty
+ -- fail_bang if we know what arg_ty is but we can't unpack it
+ -- HsStrict if it's abstract, so we don't know whether or not we can unbox it
+ can_unbox fail_bang arg_ty
+ = case splitTyConApp_maybe arg_ty of
+ Nothing -> fail_bang
+
+ Just (arg_tycon, tycon_args)
+ | isAbstractTyCon arg_tycon -> HsStrict
+ -- See Note [Don't complain about UNPACK on abstract TyCons]
+ | not (isRecursiveTyCon arg_tycon) -- Note [Recusive unboxing]
+ , isProductTyCon arg_tycon
+ -- We can unbox if the type is a chain of newtypes
+ -- with a product tycon at the end
+ -> if isNewTyCon arg_tycon
+ then can_unbox fail_bang (newTyConInstRhs arg_tycon tycon_args)
+ else HsUnpack
+
+ | otherwise -> fail_bang
\end{code}
+Note [Don't complain about UNPACK on abstract TyCons]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+We are going to complain about UnpackFailed, but if we say
+ data T = MkT {-# UNPACK #-} !Wobble
+and Wobble is a newtype imported from a module that was compiled
+without optimisation, we don't want to complain. Because it might
+be fine when optimsation is on. I think this happens when Haddock
+is working over (say) GHC souce files.
+
+Note [Recursive unboxing]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Be careful not to try to unbox this!
+ data T = MkT !T Int
+But it's the *argument* type that matters. This is fine:
+ data S = MkS S !Int
+because Int is non-recursive.
+
+
%************************************************************************
%* *
-\subsection{Dependency analysis}
+ Validity checking
%* *
%************************************************************************
tied, so we can look at things freely.
\begin{code}
-checkCycleErrs :: [LTyClDecl Name] -> TcM ()
-checkCycleErrs tyclss
+checkClassCycleErrs :: [LTyClDecl Name] -> TcM ()
+checkClassCycleErrs tyclss
| null cls_cycles
= return ()
| otherwise
- = do { mappM_ recClsErr cls_cycles
+ = do { mapM_ recClsErr cls_cycles
; failM } -- Give up now, because later checkValidTyCl
-- will loop if the synonym is recursive
where
checkValidTyCl decl
= tcAddDeclCtxt decl $
do { thing <- tcLookupLocatedGlobal (tcdLName decl)
- ; traceTc (text "Validity of" <+> ppr thing)
+ ; traceTc "Validity of" (ppr thing)
; case thing of
ATyCon tc -> checkValidTyCon tc
- AClass cl -> checkValidClass cl
- ; traceTc (text "Done validity of" <+> ppr thing)
+ AClass cl -> do { checkValidClass cl
+ ; mapM_ (addLocM checkValidTyCl) (tcdATs decl) }
+ AnId _ -> return () -- Generic default methods are checked
+ -- with their parent class
+ _ -> panic "checkValidTyCl"
+ ; traceTc "Done validity of" (ppr thing)
}
-------------------------
-- (b) has the same type for 'f'
-- module alpha conversion of the quantified type variables
-- of the constructor.
+--
+-- Note that we allow existentials to match becuase the
+-- fields can never meet. E.g
+-- data T where
+-- T1 { f1 :: b, f2 :: a, f3 ::Int } :: T
+-- T2 { f1 :: c, f2 :: c, f3 ::Int } :: T
+-- Here we do not complain about f1,f2 because they are existential
checkValidTyCon :: TyCon -> TcM ()
-checkValidTyCon tc
+checkValidTyCon tc
| isSynTyCon tc
- = checkValidType syn_ctxt syn_rhs
+ = case synTyConRhs tc of
+ SynFamilyTyCon {} -> return ()
+ SynonymTyCon ty -> checkValidType syn_ctxt ty
| otherwise
- = -- Check the context on the data decl
- checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
+ = do -- Check the context on the data decl
+ checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
-- Check arg types of data constructors
- mappM_ (checkValidDataCon tc) data_cons `thenM_`
+ mapM_ (checkValidDataCon tc) data_cons
-- Check that fields with the same name share a type
- mappM_ check_fields groups
+ mapM_ check_fields groups
where
syn_ctxt = TySynCtxt name
name = tyConName tc
- syn_rhs = synTyConRhs tc
data_cons = tyConDataCons tc
groups = equivClasses cmp_fld (concatMap get_fields data_cons)
get_fields con = dataConFieldLabels con `zip` repeat con
-- dataConFieldLabels may return the empty list, which is fine
- -- Note: The complicated checkOne logic below is there to accomodate
- -- for different return types. Add res_ty to the mix,
- -- comparing them in two steps, all for good error messages.
- -- Plan: Use Unify.tcMatchTys to compare the first candidate's
- -- result type against other candidates' types (check bothways).
- -- If they magically agrees, take the substitution and
- -- apply them to the latter ones, and see if they match perfectly.
- -- check_fields fields@((first_field_label, field_ty) : other_fields)
- check_fields fields@((label, con1) : other_fields)
+ -- See Note [GADT record selectors] in MkId.lhs
+ -- We must check (a) that the named field has the same
+ -- type in each constructor
+ -- (b) that those constructors have the same result type
+ --
+ -- However, the constructors may have differently named type variable
+ -- and (worse) we don't know how the correspond to each other. E.g.
+ -- C1 :: forall a b. { f :: a, g :: b } -> T a b
+ -- C2 :: forall d c. { f :: c, g :: c } -> T c d
+ --
+ -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
+ -- result type against other candidates' types BOTH WAYS ROUND.
+ -- If they magically agrees, take the substitution and
+ -- apply them to the latter ones, and see if they match perfectly.
+ check_fields ((label, con1) : other_fields)
-- These fields all have the same name, but are from
-- different constructors in the data type
= recoverM (return ()) $ mapM_ checkOne other_fields
-- NB: this check assumes that all the constructors of a given
-- data type use the same type variables
where
- tvs1 = mkVarSet (dataConTyVars con1)
- res1 = dataConResTys con1
+ (tvs1, _, _, res1) = dataConSig con1
+ ts1 = mkVarSet tvs1
fty1 = dataConFieldType con1 label
checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
- = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
- ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
+ = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
+ ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
where
- tvs2 = mkVarSet (dataConTyVars con2)
- res2 = dataConResTys con2
+ (tvs2, _, _, res2) = dataConSig con2
+ ts2 = mkVarSet tvs2
fty2 = dataConFieldType con2 label
+ check_fields [] = panic "checkValidTyCon/check_fields []"
+checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
+ -> Type -> Type -> Type -> Type -> TcM ()
checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
= do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
where
- mb_subst1 = tcMatchTys tvs1 res1 res2
+ mb_subst1 = tcMatchTy tvs1 res1 res2
mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
-------------------------------
checkValidDataCon tc con
= setSrcSpan (srcLocSpan (getSrcLoc con)) $
addErrCtxt (dataConCtxt con) $
- do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
- ; checkValidType ctxt (idType (dataConWrapId con)) }
-
- -- This checks the argument types and
- -- ambiguity of the existential context (if any)
- --
- -- Note [Sept 04] Now that tvs is all the tvs, this
- -- test doesn't actually check anything
--- ; checkFreeness tvs ex_theta }
+ do { traceTc "Validity of data con" (ppr con)
+ ; let tc_tvs = tyConTyVars tc
+ res_ty_tmpl = mkFamilyTyConApp tc (mkTyVarTys tc_tvs)
+ actual_res_ty = dataConOrigResTy con
+ ; checkTc (isJust (tcMatchTy (mkVarSet tc_tvs)
+ res_ty_tmpl
+ actual_res_ty))
+ (badDataConTyCon con res_ty_tmpl actual_res_ty)
+ ; checkValidMonoType (dataConOrigResTy con)
+ -- Disallow MkT :: T (forall a. a->a)
+ -- Reason: it's really the argument of an equality constraint
+ ; checkValidType ctxt (dataConUserType con)
+ ; when (isNewTyCon tc) (checkNewDataCon con)
+ ; mapM_ check_bang (dataConStrictMarks con `zip` [1..])
+ }
where
ctxt = ConArgCtxt (dataConName con)
--- (tvs, ex_theta, _, _, _) = dataConSig con
+ check_bang (HsUnpackFailed, n) = addWarnTc (cant_unbox_msg n)
+ check_bang _ = return ()
+ cant_unbox_msg n = sep [ ptext (sLit "Ignoring unusable UNPACK pragma on the")
+ , speakNth n <+> ptext (sLit "argument of") <+> quotes (ppr con)]
+
+-------------------------------
+checkNewDataCon :: DataCon -> TcM ()
+-- Checks for the data constructor of a newtype
+checkNewDataCon con
+ = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
+ -- One argument
+ ; checkTc (null eq_spec) (newtypePredError con)
+ -- Return type is (T a b c)
+ ; checkTc (null ex_tvs && null theta) (newtypeExError con)
+ -- No existentials
+ ; checkTc (not (any isBanged (dataConStrictMarks con)))
+ (newtypeStrictError con)
+ -- No strictness
+ }
+ where
+ (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
-------------------------------
checkValidClass :: Class -> TcM ()
checkValidClass cls
- = do { -- CHECK ARITY 1 FOR HASKELL 1.4
- gla_exts <- doptM Opt_GlasgowExts
+ = do { constrained_class_methods <- xoptM Opt_ConstrainedClassMethods
+ ; multi_param_type_classes <- xoptM Opt_MultiParamTypeClasses
+ ; fundep_classes <- xoptM Opt_FunctionalDependencies
-- Check that the class is unary, unless GlaExs
; checkTc (notNull tyvars) (nullaryClassErr cls)
- ; checkTc (gla_exts || unary) (classArityErr cls)
+ ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
+ ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
-- Check the super-classes
; checkValidTheta (ClassSCCtxt (className cls)) theta
-- Check the class operations
- ; mappM_ (check_op gla_exts) op_stuff
+ ; mapM_ (check_op constrained_class_methods) op_stuff
-- Check that if the class has generic methods, then the
-- class has only one parameter. We can't do generic
; checkTc (unary || no_generics) (genericMultiParamErr cls)
}
where
- (tyvars, theta, _, op_stuff) = classBigSig cls
+ (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
unary = isSingleton tyvars
- no_generics = null [() | (_, GenDefMeth) <- op_stuff]
+ no_generics = null [() | (_, (GenDefMeth _)) <- op_stuff]
- check_op gla_exts (sel_id, dm)
+ check_op constrained_class_methods (sel_id, dm)
= addErrCtxt (classOpCtxt sel_id tau) $ do
{ checkValidTheta SigmaCtxt (tail theta)
-- The 'tail' removes the initial (C a) from the
-- class itself, leaving just the method type
+ ; traceTc "class op type" (ppr op_ty <+> ppr tau)
; checkValidType (FunSigCtxt op_name) tau
-- Check that the type mentions at least one of
- -- the class type variables
- ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
+ -- the class type variables...or at least one reachable
+ -- from one of the class variables. Example: tc223
+ -- class Error e => Game b mv e | b -> mv e where
+ -- newBoard :: MonadState b m => m ()
+ -- Here, MonadState has a fundep m->b, so newBoard is fine
+ ; let grown_tyvars = growThetaTyVars theta (mkVarSet tyvars)
+ ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
(noClassTyVarErr cls sel_id)
- -- Check that for a generic method, the type of
- -- the method is sufficiently simple
- ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
- (badGenericMethodType op_name op_ty)
+ ; case dm of
+ GenDefMeth dm_name -> do { dm_id <- tcLookupId dm_name
+ ; checkValidType (FunSigCtxt op_name) (idType dm_id) }
+ _ -> return ()
}
where
op_name = idName sel_id
op_ty = idType sel_id
(_,theta1,tau1) = tcSplitSigmaTy op_ty
(_,theta2,tau2) = tcSplitSigmaTy tau1
- (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
- | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
+ (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
+ | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
-- Ugh! The function might have a type like
-- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
- -- With -fglasgow-exts, we want to allow this, even though the inner
+ -- With -XConstrainedClassMethods, we want to allow this, even though the inner
-- forall has an (Eq a) constraint. Whereas in general, each constraint
-- in the context of a for-all must mention at least one quantified
-- type variable. What a mess!
+\end{code}
----------------------------------------------------------------------
+%************************************************************************
+%* *
+ Building record selectors
+%* *
+%************************************************************************
+
+\begin{code}
+mkDefaultMethodIds :: [TyThing] -> [Id]
+-- See Note [Default method Ids and Template Haskell]
+mkDefaultMethodIds things
+ = [ mkExportedLocalId dm_name (idType sel_id)
+ | AClass cls <- things
+ , (sel_id, DefMeth dm_name) <- classOpItems cls ]
+\end{code}
+
+Note [Default method Ids and Template Haskell]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider this (Trac #4169):
+ class Numeric a where
+ fromIntegerNum :: a
+ fromIntegerNum = ...
+
+ ast :: Q [Dec]
+ ast = [d| instance Numeric Int |]
+
+When we typecheck 'ast' we have done the first pass over the class decl
+(in tcTyClDecls), but we have not yet typechecked the default-method
+declarations (becuase they can mention value declarations). So we
+must bring the default method Ids into scope first (so they can be seen
+when typechecking the [d| .. |] quote, and typecheck them later.
+
+\begin{code}
+mkRecSelBinds :: [TyCon] -> HsValBinds Name
+-- NB We produce *un-typechecked* bindings, rather like 'deriving'
+-- This makes life easier, because the later type checking will add
+-- all necessary type abstractions and applications
+mkRecSelBinds tycons
+ = ValBindsOut [(NonRecursive, b) | b <- binds] sigs
+ where
+ (sigs, binds) = unzip rec_sels
+ rec_sels = map mkRecSelBind [ (tc,fld)
+ | tc <- tycons
+ , fld <- tyConFields tc ]
+
+mkRecSelBind :: (TyCon, FieldLabel) -> (LSig Name, LHsBinds Name)
+mkRecSelBind (tycon, sel_name)
+ = (L loc (IdSig sel_id), unitBag (L loc sel_bind))
+ where
+ loc = getSrcSpan tycon
+ sel_id = Var.mkLocalVar rec_details sel_name sel_ty vanillaIdInfo
+ rec_details = RecSelId { sel_tycon = tycon, sel_naughty = is_naughty }
+
+ -- Find a representative constructor, con1
+ all_cons = tyConDataCons tycon
+ cons_w_field = [ con | con <- all_cons
+ , sel_name `elem` dataConFieldLabels con ]
+ con1 = ASSERT( not (null cons_w_field) ) head cons_w_field
+
+ -- Selector type; Note [Polymorphic selectors]
+ field_ty = dataConFieldType con1 sel_name
+ data_ty = dataConOrigResTy con1
+ data_tvs = tyVarsOfType data_ty
+ is_naughty = not (tyVarsOfType field_ty `subVarSet` data_tvs)
+ (field_tvs, field_theta, field_tau) = tcSplitSigmaTy field_ty
+ sel_ty | is_naughty = unitTy -- See Note [Naughty record selectors]
+ | otherwise = mkForAllTys (varSetElems data_tvs ++ field_tvs) $
+ mkPhiTy (dataConStupidTheta con1) $ -- Urgh!
+ mkPhiTy field_theta $ -- Urgh!
+ mkFunTy data_ty field_tau
+
+ -- Make the binding: sel (C2 { fld = x }) = x
+ -- sel (C7 { fld = x }) = x
+ -- where cons_w_field = [C2,C7]
+ sel_bind | is_naughty = mkFunBind sel_lname [mkSimpleMatch [] unit_rhs]
+ | otherwise = mkFunBind sel_lname (map mk_match cons_w_field ++ deflt)
+ mk_match con = mkSimpleMatch [L loc (mk_sel_pat con)]
+ (L loc (HsVar field_var))
+ mk_sel_pat con = ConPatIn (L loc (getName con)) (RecCon rec_fields)
+ rec_fields = HsRecFields { rec_flds = [rec_field], rec_dotdot = Nothing }
+ rec_field = HsRecField { hsRecFieldId = sel_lname
+ , hsRecFieldArg = nlVarPat field_var
+ , hsRecPun = False }
+ sel_lname = L loc sel_name
+ field_var = mkInternalName (mkBuiltinUnique 1) (getOccName sel_name) loc
+
+ -- Add catch-all default case unless the case is exhaustive
+ -- We do this explicitly so that we get a nice error message that
+ -- mentions this particular record selector
+ deflt | not (any is_unused all_cons) = []
+ | otherwise = [mkSimpleMatch [nlWildPat]
+ (nlHsApp (nlHsVar (getName rEC_SEL_ERROR_ID))
+ (nlHsLit msg_lit))]
+
+ -- Do not add a default case unless there are unmatched
+ -- constructors. We must take account of GADTs, else we
+ -- get overlap warning messages from the pattern-match checker
+ is_unused con = not (con `elem` cons_w_field
+ || dataConCannotMatch inst_tys con)
+ inst_tys = tyConAppArgs data_ty
+
+ unit_rhs = mkLHsTupleExpr []
+ msg_lit = HsStringPrim $ mkFastString $
+ occNameString (getOccName sel_name)
+
+---------------
+tyConFields :: TyCon -> [FieldLabel]
+tyConFields tc
+ | isAlgTyCon tc = nub (concatMap dataConFieldLabels (tyConDataCons tc))
+ | otherwise = []
+\end{code}
+
+Note [Polymorphic selectors]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+When a record has a polymorphic field, we pull the foralls out to the front.
+ data T = MkT { f :: forall a. [a] -> a }
+Then f :: forall a. T -> [a] -> a
+NOT f :: T -> forall a. [a] -> a
+
+This is horrid. It's only needed in deeply obscure cases, which I hate.
+The only case I know is test tc163, which is worth looking at. It's far
+from clear that this test should succeed at all!
+
+Note [Naughty record selectors]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+A "naughty" field is one for which we can't define a record
+selector, because an existential type variable would escape. For example:
+ data T = forall a. MkT { x,y::a }
+We obviously can't define
+ x (MkT v _) = v
+Nevertheless we *do* put a RecSelId into the type environment
+so that if the user tries to use 'x' as a selector we can bleat
+helpfully, rather than saying unhelpfully that 'x' is not in scope.
+Hence the sel_naughty flag, to identify record selectors that don't really exist.
+
+In general, a field is "naughty" if its type mentions a type variable that
+isn't in the result type of the constructor. Note that this *allows*
+GADT record selectors (Note [GADT record selectors]) whose types may look
+like sel :: T [a] -> a
+
+For naughty selectors we make a dummy binding
+ sel = ()
+for naughty selectors, so that the later type-check will add them to the
+environment, and they'll be exported. The function is never called, because
+the tyepchecker spots the sel_naughty field.
+
+Note [GADT record selectors]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For GADTs, we require that all constructors with a common field 'f' have the same
+result type (modulo alpha conversion). [Checked in TcTyClsDecls.checkValidTyCon]
+E.g.
+ data T where
+ T1 { f :: Maybe a } :: T [a]
+ T2 { f :: Maybe a, y :: b } :: T [a]
+
+and now the selector takes that result type as its argument:
+ f :: forall a. T [a] -> Maybe a
+
+Details: the "real" types of T1,T2 are:
+ T1 :: forall r a. (r~[a]) => a -> T r
+ T2 :: forall r a b. (r~[a]) => a -> b -> T r
+
+So the selector loooks like this:
+ f :: forall a. T [a] -> Maybe a
+ f (a:*) (t:T [a])
+ = case t of
+ T1 c (g:[a]~[c]) (v:Maybe c) -> v `cast` Maybe (right (sym g))
+ T2 c d (g:[a]~[c]) (v:Maybe c) (w:d) -> v `cast` Maybe (right (sym g))
+
+Note the forall'd tyvars of the selector are just the free tyvars
+of the result type; there may be other tyvars in the constructor's
+type (e.g. 'b' in T2).
+
+Note the need for casts in the result!
+
+Note [Selector running example]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It's OK to combine GADTs and type families. Here's a running example:
+
+ data instance T [a] where
+ T1 { fld :: b } :: T [Maybe b]
+
+The representation type looks like this
+ data :R7T a where
+ T1 { fld :: b } :: :R7T (Maybe b)
+
+and there's coercion from the family type to the representation type
+ :CoR7T a :: T [a] ~ :R7T a
+
+The selector we want for fld looks like this:
+
+ fld :: forall b. T [Maybe b] -> b
+ fld = /\b. \(d::T [Maybe b]).
+ case d `cast` :CoR7T (Maybe b) of
+ T1 (x::b) -> x
+
+The scrutinee of the case has type :R7T (Maybe b), which can be
+gotten by appying the eq_spec to the univ_tvs of the data con.
+
+%************************************************************************
+%* *
+ Error messages
+%* *
+%************************************************************************
+
+\begin{code}
+resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
resultTypeMisMatch field_name con1 con2
- = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
- ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
- nest 2 $ ptext SLIT("but have different result types")]
+ = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
+ ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
+ nest 2 $ ptext (sLit "but have different result types")]
+
+fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
fieldTypeMisMatch field_name con1 con2
- = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
- ptext SLIT("give different types for field"), quotes (ppr field_name)]
+ = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
+ ptext (sLit "give different types for field"), quotes (ppr field_name)]
-dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
+dataConCtxt :: Outputable a => a -> SDoc
+dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
-classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
+classOpCtxt :: Var -> Type -> SDoc
+classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
+nullaryClassErr :: Class -> SDoc
nullaryClassErr cls
- = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
+ = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
+classArityErr :: Class -> SDoc
classArityErr cls
- = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
- parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
+ = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
+ parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
+classFunDepsErr :: Class -> SDoc
+classFunDepsErr cls
+ = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
+ parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
+
+noClassTyVarErr :: Class -> Var -> SDoc
noClassTyVarErr clas op
- = sep [ptext SLIT("The class method") <+> quotes (ppr op),
- ptext SLIT("mentions none of the type variables of the class") <+>
+ = sep [ptext (sLit "The class method") <+> quotes (ppr op),
+ ptext (sLit "mentions none of the type variables of the class") <+>
ppr clas <+> hsep (map ppr (classTyVars clas))]
+genericMultiParamErr :: Class -> SDoc
genericMultiParamErr clas
- = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
- ptext SLIT("cannot have generic methods")
-
-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, lists, and tuples")])
+ = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
+ ptext (sLit "cannot have generic methods")
+recSynErr :: [LTyClDecl Name] -> TcRn ()
recSynErr syn_decls
= setSrcSpan (getLoc (head sorted_decls)) $
- addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
+ addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
nest 2 (vcat (map ppr_decl sorted_decls))])
where
sorted_decls = sortLocated syn_decls
ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
+recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
recClsErr cls_decls
= setSrcSpan (getLoc (head sorted_decls)) $
- addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
+ addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
nest 2 (vcat (map ppr_decl sorted_decls))])
where
sorted_decls = sortLocated cls_decls
where
le (L l1 _) (L l2 _) = l1 <= l2
-badDataConTyCon data_con
- = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
- ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
- 2 (ptext SLIT("instead of its parent type"))
+badDataConTyCon :: DataCon -> Type -> Type -> SDoc
+badDataConTyCon data_con res_ty_tmpl actual_res_ty
+ = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
+ ptext (sLit "returns type") <+> quotes (ppr actual_res_ty))
+ 2 (ptext (sLit "instead of an instance of its parent type") <+> quotes (ppr res_ty_tmpl))
+badGadtDecl :: Name -> SDoc
badGadtDecl tc_name
- = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
+ = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
+ , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
+
+badExistential :: Located Name -> SDoc
+badExistential con_name
+ = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
+ ptext (sLit "has existential type variables, a context, or a specialised result type"))
+ 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
+
+badStupidTheta :: Name -> SDoc
+badStupidTheta tc_name
+ = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
+newtypeConError :: Name -> Int -> SDoc
newtypeConError tycon n
- = sep [ptext SLIT("A newtype must have exactly one constructor,"),
- nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
+ = sep [ptext (sLit "A newtype must have exactly one constructor,"),
+ nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
+newtypeExError :: DataCon -> SDoc
newtypeExError con
- = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
- nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
+ = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
+ nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
-newtypeFieldErr con_name n_flds
- = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
- nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
+newtypeStrictError :: DataCon -> SDoc
+newtypeStrictError con
+ = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
+ nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
+
+newtypePredError :: DataCon -> SDoc
+newtypePredError con
+ = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
+ nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
+newtypeFieldErr :: DataCon -> Int -> SDoc
+newtypeFieldErr con_name n_flds
+ = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
+ nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
+
+badSigTyDecl :: Name -> SDoc
+badSigTyDecl tc_name
+ = vcat [ ptext (sLit "Illegal kind signature") <+>
+ quotes (ppr tc_name)
+ , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
+
+badFamInstDecl :: Outputable a => a -> SDoc
+badFamInstDecl tc_name
+ = vcat [ ptext (sLit "Illegal family instance for") <+>
+ quotes (ppr tc_name)
+ , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
+
+emptyConDeclsErr :: Name -> SDoc
emptyConDeclsErr tycon
- = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
- nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]
+ = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
+ nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]
\end{code}
projects / ghc-hetmet.git / blobdiff