\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta,
+module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, tcHsPred,
UserTypeCtxt(..),
-- Kind checking
kcHsLiftedSigType, kcHsContext,
tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars,
- TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
- checkSigTyVars, sigCtxt, sigPatCtxt
+ TcSigInfo(..), tcTySig, mkTcSig, maybeSig, tcSigPolyId, tcSigMonoId
) where
#include "HsVersions.h"
-import HsSyn ( HsType(..), HsTyVarBndr(..),
+import HsSyn ( HsType(..), HsTyVarBndr(..), HsTyOp(..),
Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames )
import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars )
import TcHsSyn ( TcId )
-import TcMonad
+import TcRnMonad
import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
- tcGetGlobalTyVars, tcLEnvElts, tcInLocalScope,
- TyThing(..), TcTyThing(..), tcExtendKindEnv
+ TyThing(..), TcTyThing(..), tcExtendKindEnv,
+ getInLocalScope
)
-import TcMType ( newKindVar, tcInstSigTyVars,
- zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar,
- unifyKind, unifyOpenTypeKind,
+import TcMType ( newMutTyVar, newKindVar, zonkKindEnv, tcInstType,
checkValidType, UserTypeCtxt(..), pprUserTypeCtxt
)
+import TcUnify ( unifyKind, unifyOpenTypeKind )
import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..),
- TcTyVar, TcTyVarSet, TcType, TcKind, TcThetaType, TcTauType,
- mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
- tcSplitForAllTys, tcSplitRhoTy,
- hoistForAllTys, allDistinctTyVars, zipFunTys,
- mkSigmaTy, mkPredTy, mkTyConApp, mkAppTys, mkRhoTy,
+ TcTyVar, TcKind, TcThetaType, TcTauType,
+ mkTyVarTy, mkTyVarTys, mkFunTy,
+ zipFunTys, mkForAllTys, mkFunTys, tcEqType, isPredTy,
+ mkSigmaTy, mkPredTy, mkGenTyConApp, mkTyConApp, mkAppTys,
liftedTypeKind, unliftedTypeKind, mkArrowKind,
- mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe,
- tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars,
- tyVarsOfType, mkForAllTys
+ mkArrowKinds, tcSplitFunTy_maybe, tcSplitForAllTys
)
-import qualified Type ( getTyVar_maybe )
+import Inst ( Inst, InstOrigin(..), newMethodWith, instToId )
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
-import PprType ( pprType )
-import Subst ( mkTopTyVarSubst, substTy )
-import CoreFVs ( idFreeTyVars )
import Id ( mkLocalId, idName, idType )
-import Var ( Id, Var, TyVar, mkTyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
-import VarEnv
-import VarSet
+import Var ( TyVar, mkTyVar, tyVarKind )
import ErrUtils ( Message )
-import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind )
+import TyCon ( TyCon, tyConKind )
import Class ( classTyCon )
-import Name ( Name, getSrcLoc )
+import Name ( Name )
import NameSet
-import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
+import Subst ( deShadowTy )
+import TysWiredIn ( mkListTy, mkPArrTy, mkTupleTy, genUnitTyCon )
import BasicTypes ( Boxity(..) )
import SrcLoc ( SrcLoc )
-import Util ( isSingleton, lengthIs )
+import Util ( lengthIs )
import Outputable
-
+import List ( nubBy )
\end{code}
\begin{code}
tcHsSigType :: UserTypeCtxt -> RenamedHsType -> TcM Type
-- Do kind checking, and hoist for-alls to the top
-tcHsSigType ctxt ty = tcAddErrCtxt (checkTypeCtxt ctxt ty) (
- kcTypeType ty `thenTc_`
+tcHsSigType ctxt ty = addErrCtxt (checkTypeCtxt ctxt ty) (
+ kcTypeType ty `thenM_`
tcHsType ty
- ) `thenTc` \ ty' ->
- checkValidType ctxt ty' `thenTc_`
- returnTc ty'
+ ) `thenM` \ ty' ->
+ checkValidType ctxt ty' `thenM_`
+ returnM ty'
checkTypeCtxt ctxt ty
= vcat [ptext SLIT("In the type:") <+> ppr ty,
-- This is used in type and class decls, where kinding is
-- done in advance, and validity checking is done later
-- [Validity checking done later because of knot-tying issues.]
-tcHsType ty = tc_type ty `thenTc` \ ty' ->
- returnTc (hoistForAllTys ty')
+tcHsType ty = tc_type ty `thenM` \ ty' ->
+ returnM (hoistForAllTys ty')
tcHsTheta :: RenamedContext -> TcM ThetaType
-- Used when we are expecting a ClassContext (i.e. no implicit params)
-- Does not do validity checking, like tcHsType
-tcHsTheta hs_theta = mapTc tc_pred hs_theta
+tcHsTheta hs_theta = mappM tc_pred hs_theta
-- In interface files the type is already kinded,
-- and we definitely don't want to hoist for-alls.
-- A useful short cut for a common case!
tcHsTyVars tv_names kind_check thing_inside
- = kcHsTyVars tv_names `thenNF_Tc` \ tv_names_w_kinds ->
- tcExtendKindEnv tv_names_w_kinds kind_check `thenTc_`
- zonkKindEnv tv_names_w_kinds `thenNF_Tc` \ tvs_w_kinds ->
+ = kcHsTyVars tv_names `thenM` \ tv_names_w_kinds ->
+ tcExtendKindEnv tv_names_w_kinds kind_check `thenM_`
+ zonkKindEnv tv_names_w_kinds `thenM` \ tvs_w_kinds ->
let
tyvars = mkImmutTyVars tvs_w_kinds
in
= thing_inside -- Quick get-out for the empty case
tcAddScopedTyVars sig_tys thing_inside
- = tcGetEnv `thenNF_Tc` \ env ->
+ = getInLocalScope `thenM` \ in_scope ->
let
all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys
- sig_tvs = filter not_in_scope (nameSetToList all_sig_tvs)
- not_in_scope tv = not (tcInLocalScope env tv)
+ sig_tvs = filter (not . in_scope) (nameSetToList all_sig_tvs)
in
- mapNF_Tc newNamedKindVar sig_tvs `thenTc` \ kind_env ->
- tcExtendKindEnv kind_env (kcHsSigTypes sig_tys) `thenTc_`
- zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds ->
- listTc [ tcNewMutTyVar name kind PatSigTv
- | (name, kind) <- tvs_w_kinds] `thenNF_Tc` \ tyvars ->
+ mappM newNamedKindVar sig_tvs `thenM` \ kind_env ->
+ tcExtendKindEnv kind_env (kcHsSigTypes sig_tys) `thenM_`
+ zonkKindEnv kind_env `thenM` \ tvs_w_kinds ->
+ sequenceM [ newMutTyVar name kind PatSigTv
+ | (name, kind) <- tvs_w_kinds] `thenM` \ tyvars ->
tcExtendTyVarEnv tyvars thing_inside
\end{code}
\begin{code}
-kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind)
-kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)]
+kcHsTyVar :: HsTyVarBndr name -> TcM (name, TcKind)
+kcHsTyVars :: [HsTyVarBndr name] -> TcM [(name, TcKind)]
kcHsTyVar (UserTyVar name) = newNamedKindVar name
-kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (name, kind)
+kcHsTyVar (IfaceTyVar name kind) = returnM (name, kind)
-kcHsTyVars tvs = mapNF_Tc kcHsTyVar tvs
+kcHsTyVars tvs = mappM kcHsTyVar tvs
-newNamedKindVar name = newKindVar `thenNF_Tc` \ kind ->
- returnNF_Tc (name, kind)
+newNamedKindVar name = newKindVar `thenM` \ kind ->
+ returnM (name, kind)
---------------------------
kcLiftedType :: RenamedHsType -> TcM ()
-- The type ty must be a *lifted* *type*
kcLiftedType ty
- = kcHsType ty `thenTc` \ kind ->
- tcAddErrCtxt (typeKindCtxt ty) $
+ = kcHsType ty `thenM` \ kind ->
+ addErrCtxt (typeKindCtxt ty) $
unifyKind liftedTypeKind kind
---------------------------
kcTypeType :: RenamedHsType -> TcM ()
-- The type ty must be a *type*, but it can be lifted or unlifted.
kcTypeType ty
- = kcHsType ty `thenTc` \ kind ->
- tcAddErrCtxt (typeKindCtxt ty) $
+ = kcHsType ty `thenM` \ kind ->
+ addErrCtxt (typeKindCtxt ty) $
unifyOpenTypeKind kind
---------------------------
kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM ()
-- Used for type signatures
kcHsSigType = kcTypeType
-kcHsSigTypes tys = mapTc_ kcHsSigType tys
+kcHsSigTypes tys = mappM_ kcHsSigType tys
kcHsLiftedSigType = kcLiftedType
---------------------------
kcHsType :: RenamedHsType -> TcM TcKind
kcHsType (HsTyVar name) = kcTyVar name
+kcHsType (HsKindSig ty k)
+ = kcHsType ty `thenM` \ k' ->
+ unifyKind k k' `thenM_`
+ returnM k
+
kcHsType (HsListTy ty)
- = kcLiftedType ty `thenTc` \ tau_ty ->
- returnTc liftedTypeKind
+ = kcLiftedType ty `thenM` \ tau_ty ->
+ returnM liftedTypeKind
-kcHsType (HsTupleTy (HsTupCon _ boxity _) tys)
- = mapTc kcTypeType tys `thenTc_`
- returnTc (case boxity of
+kcHsType (HsPArrTy ty)
+ = kcLiftedType ty `thenM` \ tau_ty ->
+ returnM liftedTypeKind
+
+kcHsType (HsTupleTy (HsTupCon boxity _) tys)
+ = mappM kcTypeType tys `thenM_`
+ returnM (case boxity of
Boxed -> liftedTypeKind
Unboxed -> unliftedTypeKind)
kcHsType (HsFunTy ty1 ty2)
- = kcTypeType ty1 `thenTc_`
- kcTypeType ty2 `thenTc_`
- returnTc liftedTypeKind
-
-kcHsType (HsNumTy _) -- The unit type for generics
- = returnTc liftedTypeKind
-
-kcHsType ty@(HsOpTy ty1 op ty2)
- = kcTyVar op `thenTc` \ op_kind ->
- kcHsType ty1 `thenTc` \ ty1_kind ->
- kcHsType ty2 `thenTc` \ ty2_kind ->
- tcAddErrCtxt (appKindCtxt (ppr ty)) $
- kcAppKind op_kind ty1_kind `thenTc` \ op_kind' ->
+ = kcTypeType ty1 `thenM_`
+ kcTypeType ty2 `thenM_`
+ returnM liftedTypeKind
+
+kcHsType (HsOpTy ty1 HsArrow ty2)
+ = kcTypeType ty1 `thenM_`
+ kcTypeType ty2 `thenM_`
+ returnM liftedTypeKind
+
+kcHsType ty@(HsOpTy ty1 (HsTyOp op) ty2)
+ = kcTyVar op `thenM` \ op_kind ->
+ kcHsType ty1 `thenM` \ ty1_kind ->
+ kcHsType ty2 `thenM` \ ty2_kind ->
+ addErrCtxt (appKindCtxt (ppr ty)) $
+ kcAppKind op_kind ty1_kind `thenM` \ op_kind' ->
kcAppKind op_kind' ty2_kind
+
+kcHsType (HsParTy ty) -- Skip parentheses markers
+ = kcHsType ty
+kcHsType (HsNumTy _) -- The unit type for generics
+ = returnM liftedTypeKind
+
kcHsType (HsPredTy pred)
- = kcHsPred pred `thenTc_`
- returnTc liftedTypeKind
+ = kcHsPred pred `thenM_`
+ returnM liftedTypeKind
kcHsType ty@(HsAppTy ty1 ty2)
- = kcHsType ty1 `thenTc` \ tc_kind ->
- kcHsType ty2 `thenTc` \ arg_kind ->
- tcAddErrCtxt (appKindCtxt (ppr ty)) $
+ = kcHsType ty1 `thenM` \ tc_kind ->
+ kcHsType ty2 `thenM` \ arg_kind ->
+ addErrCtxt (appKindCtxt (ppr ty)) $
kcAppKind tc_kind arg_kind
kcHsType (HsForAllTy (Just tv_names) context ty)
- = kcHsTyVars tv_names `thenNF_Tc` \ kind_env ->
+ = kcHsTyVars tv_names `thenM` \ kind_env ->
tcExtendKindEnv kind_env $
- kcHsContext context `thenTc_`
- kcHsType ty `thenTc_`
- returnTc liftedTypeKind
+ kcHsContext context `thenM_`
+ kcLiftedType ty `thenM_`
+ -- The body of a forall must be of kind *
+ -- In principle, I suppose, we could allow unlifted types,
+ -- but it seems simpler to stick to lifted types for now.
+ returnM liftedTypeKind
---------------------------
kcAppKind fun_kind arg_kind
= case tcSplitFunTy_maybe fun_kind of
Just (arg_kind', res_kind)
- -> unifyKind arg_kind arg_kind' `thenTc_`
- returnTc res_kind
+ -> unifyKind arg_kind arg_kind' `thenM_`
+ returnM res_kind
- Nothing -> newKindVar `thenNF_Tc` \ res_kind ->
- unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenTc_`
- returnTc res_kind
+ Nothing -> newKindVar `thenM` \ res_kind ->
+ unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenM_`
+ returnM res_kind
---------------------------
-kcHsContext ctxt = mapTc_ kcHsPred ctxt
+kc_pred :: RenamedHsPred -> TcM TcKind -- Does *not* check for a saturated
+ -- application (reason: used from TcDeriv)
+kc_pred pred@(HsIParam name ty)
+ = kcHsType ty
+
+kc_pred pred@(HsClassP cls tys)
+ = kcClass cls `thenM` \ kind ->
+ mappM kcHsType tys `thenM` \ arg_kinds ->
+ newKindVar `thenM` \ kv ->
+ unifyKind kind (mkArrowKinds arg_kinds kv) `thenM_`
+ returnM kv
-kcHsPred :: RenamedHsPred -> TcM ()
-kcHsPred pred@(HsIParam name ty)
- = tcAddErrCtxt (appKindCtxt (ppr pred)) $
- kcLiftedType ty
+---------------------------
+kcHsContext ctxt = mappM_ kcHsPred ctxt
-kcHsPred pred@(HsClassP cls tys)
- = tcAddErrCtxt (appKindCtxt (ppr pred)) $
- kcClass cls `thenTc` \ kind ->
- mapTc kcHsType tys `thenTc` \ arg_kinds ->
- unifyKind kind (mkArrowKinds arg_kinds liftedTypeKind)
+kcHsPred pred -- Checks that the result is of kind liftedType
+ = addErrCtxt (appKindCtxt (ppr pred)) $
+ kc_pred pred `thenM` \ kind ->
+ unifyKind liftedTypeKind kind `thenM_`
+ returnM ()
+
---------------------------
kcTyVar name -- Could be a tyvar or a tycon
- = tcLookup name `thenTc` \ thing ->
+ = tcLookup name `thenM` \ thing ->
case thing of
- AThing kind -> returnTc kind
- ATyVar tv -> returnTc (tyVarKind tv)
- AGlobal (ATyCon tc) -> returnTc (tyConKind tc)
+ AThing kind -> returnM kind
+ ATyVar tv -> returnM (tyVarKind tv)
+ AGlobal (ATyCon tc) -> returnM (tyConKind tc)
other -> failWithTc (wrongThingErr "type" thing name)
kcClass cls -- Must be a class
- = tcLookup cls `thenNF_Tc` \ thing ->
+ = tcLookup cls `thenM` \ thing ->
case thing of
- AThing kind -> returnTc kind
- AGlobal (AClass cls) -> returnTc (tyConKind (classTyCon cls))
+ AThing kind -> returnM kind
+ AGlobal (AClass cls) -> returnM (tyConKind (classTyCon cls))
other -> failWithTc (wrongThingErr "class" thing cls)
\end{code}
tc_type ty@(HsTyVar name)
= tc_app ty []
+tc_type (HsKindSig ty k)
+ = tc_type ty -- Kind checking done already
+
tc_type (HsListTy ty)
- = tc_type ty `thenTc` \ tau_ty ->
- returnTc (mkListTy tau_ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkListTy tau_ty)
+
+tc_type (HsPArrTy ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkPArrTy tau_ty)
-tc_type (HsTupleTy (HsTupCon _ boxity arity) tys)
+tc_type (HsTupleTy (HsTupCon boxity arity) tys)
= ASSERT( tys `lengthIs` arity )
- tc_types tys `thenTc` \ tau_tys ->
- returnTc (mkTupleTy boxity arity tau_tys)
+ tc_types tys `thenM` \ tau_tys ->
+ returnM (mkTupleTy boxity arity tau_tys)
tc_type (HsFunTy ty1 ty2)
- = tc_type ty1 `thenTc` \ tau_ty1 ->
- tc_type ty2 `thenTc` \ tau_ty2 ->
- returnTc (mkFunTy tau_ty1 tau_ty2)
+ = tc_type ty1 `thenM` \ tau_ty1 ->
+ tc_type ty2 `thenM` \ tau_ty2 ->
+ returnM (mkFunTy tau_ty1 tau_ty2)
+
+tc_type (HsOpTy ty1 HsArrow ty2)
+ = tc_type ty1 `thenM` \ tau_ty1 ->
+ tc_type ty2 `thenM` \ tau_ty2 ->
+ returnM (mkFunTy tau_ty1 tau_ty2)
+
+tc_type (HsOpTy ty1 (HsTyOp op) ty2)
+ = tc_type ty1 `thenM` \ tau_ty1 ->
+ tc_type ty2 `thenM` \ tau_ty2 ->
+ tc_fun_type op [tau_ty1,tau_ty2]
+
+tc_type (HsParTy ty) -- Remove the parentheses markers
+ = tc_type ty
tc_type (HsNumTy n)
= ASSERT(n== 1)
- returnTc (mkTyConApp genUnitTyCon [])
-
-tc_type (HsOpTy ty1 op ty2)
- = tc_type ty1 `thenTc` \ tau_ty1 ->
- tc_type ty2 `thenTc` \ tau_ty2 ->
- tc_fun_type op [tau_ty1,tau_ty2]
+ returnM (mkTyConApp genUnitTyCon [])
tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2]
tc_type (HsPredTy pred)
- = tc_pred pred `thenTc` \ pred' ->
- returnTc (mkPredTy pred')
+ = tc_pred pred `thenM` \ pred' ->
+ returnM (mkPredTy pred')
tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty)
= let
- kind_check = kcHsContext ctxt `thenTc_` kcHsType ty
+ kind_check = kcHsContext ctxt `thenM_` kcHsType ty
in
tcHsTyVars tv_names kind_check $ \ tyvars ->
- mapTc tc_pred ctxt `thenTc` \ theta ->
- tc_type ty `thenTc` \ tau ->
- returnTc (mkSigmaTy tyvars theta tau)
+ mappM tc_pred ctxt `thenM` \ theta ->
+ tc_type ty `thenM` \ tau ->
+ returnM (mkSigmaTy tyvars theta tau)
-tc_types arg_tys = mapTc tc_type arg_tys
+tc_types arg_tys = mappM tc_type arg_tys
\end{code}
Help functions for type applications
= tc_app ty1 (ty2:tys)
tc_app ty tys
- = tcAddErrCtxt (appKindCtxt pp_app) $
- tc_types tys `thenTc` \ arg_tys ->
+ = addErrCtxt (appKindCtxt pp_app) $
+ tc_types tys `thenM` \ arg_tys ->
case ty of
HsTyVar fun -> tc_fun_type fun arg_tys
- other -> tc_type ty `thenTc` \ fun_ty ->
- returnNF_Tc (mkAppTys fun_ty arg_tys)
+ other -> tc_type ty `thenM` \ fun_ty ->
+ returnM (mkAppTys fun_ty arg_tys)
where
pp_app = ppr ty <+> sep (map pprParendHsType tys)
-- hence the rather strange functionality.
tc_fun_type name arg_tys
- = tcLookup name `thenTc` \ thing ->
+ = tcLookup name `thenM` \ thing ->
case thing of
- ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys)
+ ATyVar tv -> returnM (mkAppTys (mkTyVarTy tv) arg_tys)
- AGlobal (ATyCon tc)
- | isSynTyCon tc -> returnTc (mkSynTy tc arg_tys)
- | otherwise -> returnTc (mkTyConApp tc arg_tys)
+ AGlobal (ATyCon tc) -> returnM (mkGenTyConApp tc arg_tys)
other -> failWithTc (wrongThingErr "type constructor" thing name)
\end{code}
Contexts
~~~~~~~~
\begin{code}
+tcHsPred pred = kc_pred pred `thenM_` tc_pred pred
+ -- Is happy with a partial application, e.g. (ST s)
+ -- Used from TcDeriv
+
tc_pred assn@(HsClassP class_name tys)
- = tcAddErrCtxt (appKindCtxt (ppr assn)) $
- tc_types tys `thenTc` \ arg_tys ->
- tcLookupGlobal class_name `thenTc` \ thing ->
+ = addErrCtxt (appKindCtxt (ppr assn)) $
+ tc_types tys `thenM` \ arg_tys ->
+ tcLookupGlobal class_name `thenM` \ thing ->
case thing of
- AClass clas -> returnTc (ClassP clas arg_tys)
+ AClass clas -> returnM (ClassP clas arg_tys)
other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name)
tc_pred assn@(HsIParam name ty)
- = tcAddErrCtxt (appKindCtxt (ppr assn)) $
- tc_type ty `thenTc` \ arg_ty ->
- returnTc (IParam name arg_ty)
+ = addErrCtxt (appKindCtxt (ppr assn)) $
+ tc_type ty `thenM` \ arg_ty ->
+ returnM (IParam name arg_ty)
\end{code}
\begin{code}
data TcSigInfo
= TySigInfo
- Name -- N, the Name in corresponding binding
-
TcId -- *Polymorphic* binder for this value...
-- Has name = N
SrcLoc -- Of the signature
instance Outputable TcSigInfo where
- ppr (TySigInfo nm id tyvars theta tau _ inst loc) =
- ppr nm <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
+ ppr (TySigInfo id tyvars theta tau _ inst loc) =
+ ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
+
+tcSigPolyId :: TcSigInfo -> TcId
+tcSigPolyId (TySigInfo id _ _ _ _ _ _) = id
+
+tcSigMonoId :: TcSigInfo -> TcId
+tcSigMonoId (TySigInfo _ _ _ _ id _ _) = id
maybeSig :: [TcSigInfo] -> Name -> Maybe (TcSigInfo)
-- Search for a particular signature
maybeSig [] name = Nothing
-maybeSig (sig@(TySigInfo sig_name _ _ _ _ _ _ _) : sigs) name
- | name == sig_name = Just sig
- | otherwise = maybeSig sigs name
+maybeSig (sig@(TySigInfo sig_id _ _ _ _ _ _) : sigs) name
+ | name == idName sig_id = Just sig
+ | otherwise = maybeSig sigs name
\end{code}
tcTySig :: RenamedSig -> TcM TcSigInfo
tcTySig (Sig v ty src_loc)
- = tcAddSrcLoc src_loc $
- tcHsSigType (FunSigCtxt v) ty `thenTc` \ sigma_tc_ty ->
- mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
- returnTc sig
+ = addSrcLoc src_loc $
+ tcHsSigType (FunSigCtxt v) ty `thenM` \ sigma_tc_ty ->
+ mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenM` \ sig ->
+ returnM sig
-mkTcSig :: TcId -> SrcLoc -> NF_TcM TcSigInfo
+mkTcSig :: TcId -> SrcLoc -> TcM TcSigInfo
mkTcSig poly_id src_loc
= -- Instantiate this type
-- It's important to do this even though in the error-free case
-- the tyvars *do* get unified with something, we want to carry on
-- typechecking the rest of the program with the function bound
-- to a pristine type, namely sigma_tc_ty
- let
- (tyvars, rho) = tcSplitForAllTys (idType poly_id)
- in
- tcInstSigTyVars SigTv tyvars `thenNF_Tc` \ tyvars' ->
- -- Make *signature* type variables
-
- let
- tyvar_tys' = mkTyVarTys tyvars'
- rho' = substTy (mkTopTyVarSubst tyvars tyvar_tys') rho
- -- mkTopTyVarSubst because the tyvars' are fresh
-
- (theta', tau') = tcSplitRhoTy rho'
- -- This splitRhoTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- newMethodWithGivenTy SignatureOrigin
- poly_id
- tyvar_tys'
- theta' tau' `thenNF_Tc` \ inst ->
+ tcInstType SigTv (idType poly_id) `thenM` \ (tyvars', theta', tau') ->
+
+ getInstLoc SignatureOrigin `thenM` \ inst_loc ->
+ newMethodWith inst_loc poly_id
+ (mkTyVarTys tyvars')
+ theta' tau' `thenM` \ inst ->
-- We make a Method even if it's not overloaded; no harm
+ -- But do not extend the LIE! We're just making an Id.
- returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc)
- where
- name = idName poly_id
+ returnM (TySigInfo poly_id tyvars' theta' tau'
+ (instToId inst) [inst] src_loc)
\end{code}
-
%************************************************************************
%* *
-\subsection{Checking signature type variables}
+\subsection{Errors and contexts}
%* *
%************************************************************************
-@checkSigTyVars@ is used after the type in a type signature has been unified with
-the actual type found. It then checks that the type variables of the type signature
-are
- (a) Still all type variables
- eg matching signature [a] against inferred type [(p,q)]
- [then a will be unified to a non-type variable]
-
- (b) Still all distinct
- eg matching signature [(a,b)] against inferred type [(p,p)]
- [then a and b will be unified together]
-
- (c) Not mentioned in the environment
- eg the signature for f in this:
-
- g x = ... where
- f :: a->[a]
- f y = [x,y]
-
- Here, f is forced to be monorphic by the free occurence of x.
-
- (d) Not (unified with another type variable that is) in scope.
- eg f x :: (r->r) = (\y->y) :: forall a. a->r
- when checking the expression type signature, we find that
- even though there is nothing in scope whose type mentions r,
- nevertheless the type signature for the expression isn't right.
-
- Another example is in a class or instance declaration:
- class C a where
- op :: forall b. a -> b
- op x = x
- Here, b gets unified with a
-
-Before doing this, the substitution is applied to the signature type variable.
-
-We used to have the notion of a "DontBind" type variable, which would
-only be bound to itself or nothing. Then points (a) and (b) were
-self-checking. But it gave rise to bogus consequential error messages.
-For example:
-
- f = (*) -- Monomorphic
-
- g :: Num a => a -> a
- g x = f x x
-
-Here, we get a complaint when checking the type signature for g,
-that g isn't polymorphic enough; but then we get another one when
-dealing with the (Num x) context arising from f's definition;
-we try to unify x with Int (to default it), but find that x has already
-been unified with the DontBind variable "a" from g's signature.
-This is really a problem with side-effecting unification; we'd like to
-undo g's effects when its type signature fails, but unification is done
-by side effect, so we can't (easily).
-
-So we revert to ordinary type variables for signatures, and try to
-give a helpful message in checkSigTyVars.
\begin{code}
-checkSigTyVars :: [TcTyVar] -- Universally-quantified type variables in the signature
- -> TcTyVarSet -- Tyvars that are free in the type signature
- -- Not necessarily zonked
- -- These should *already* be in the free-in-env set,
- -- and are used here only to improve the error message
- -> TcM [TcTyVar] -- Zonked signature type variables
-
-checkSigTyVars [] free = returnTc []
-checkSigTyVars sig_tyvars free_tyvars
- = zonkTcTyVars sig_tyvars `thenNF_Tc` \ sig_tys ->
- tcGetGlobalTyVars `thenNF_Tc` \ globals ->
-
- checkTcM (allDistinctTyVars sig_tys globals)
- (complain sig_tys globals) `thenTc_`
-
- returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys)
-
- where
- complain sig_tys globals
- = -- "check" checks each sig tyvar in turn
- foldlNF_Tc check
- (env2, emptyVarEnv, [])
- (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) ->
-
- failWithTcM (env3, main_msg $$ vcat msgs)
- where
- (env1, tidy_tvs) = tidyOpenTyVars emptyTidyEnv sig_tyvars
- (env2, tidy_tys) = tidyOpenTypes env1 sig_tys
-
- main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
-
- check (tidy_env, acc, msgs) (sig_tyvar,ty)
- -- sig_tyvar is from the signature;
- -- ty is what you get if you zonk sig_tyvar and then tidy it
- --
- -- acc maps a zonked type variable back to a signature type variable
- = case tcGetTyVar_maybe ty of {
- Nothing -> -- Error (a)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ;
-
- Just tv ->
-
- case lookupVarEnv acc tv of {
- Just sig_tyvar' -> -- Error (b)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
- where
- thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar')
-
- ; Nothing ->
-
- if tv `elemVarSet` globals -- Error (c) or (d)! Type variable escapes
- -- The least comprehensible, so put it last
- -- Game plan:
- -- a) get the local TcIds and TyVars from the environment,
- -- and pass them to find_globals (they might have tv free)
- -- b) similarly, find any free_tyvars that mention tv
- then tcGetEnv `thenNF_Tc` \ ve ->
- find_globals tv tidy_env (tcLEnvElts ve) `thenNF_Tc` \ (tidy_env1, globs) ->
- find_frees tv tidy_env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (tidy_env2, frees) ->
- returnNF_Tc (tidy_env2, acc, escape_msg sig_tyvar tv globs frees : msgs)
-
- else -- All OK
- returnNF_Tc (tidy_env, extendVarEnv acc tv sig_tyvar, msgs)
- }}
-
------------------------
--- find_globals looks at the value environment and finds values
--- whose types mention the offending type variable. It has to be
--- careful to zonk the Id's type first, so it has to be in the monad.
--- We must be careful to pass it a zonked type variable, too.
-
-find_globals :: Var
- -> TidyEnv
- -> [TcTyThing]
- -> NF_TcM (TidyEnv, [SDoc])
-
-find_globals tv tidy_env things
- = go tidy_env [] things
- where
- go tidy_env acc [] = returnNF_Tc (tidy_env, acc)
- go tidy_env acc (thing : things)
- = find_thing ignore_it tidy_env thing `thenNF_Tc` \ (tidy_env1, maybe_doc) ->
- case maybe_doc of
- Just d -> go tidy_env1 (d:acc) things
- Nothing -> go tidy_env1 acc things
-
- ignore_it ty = not (tv `elemVarSet` tyVarsOfType ty)
-
------------------------
-find_thing ignore_it tidy_env (ATcId id)
- = zonkTcType (idType id) `thenNF_Tc` \ id_ty ->
- if ignore_it id_ty then
- returnNF_Tc (tidy_env, Nothing)
- else let
- (tidy_env', tidy_ty) = tidyOpenType tidy_env id_ty
- msg = sep [ppr id <+> dcolon <+> ppr tidy_ty,
- nest 2 (parens (ptext SLIT("bound at") <+>
- ppr (getSrcLoc id)))]
- in
- returnNF_Tc (tidy_env', Just msg)
-
-find_thing ignore_it tidy_env (ATyVar tv)
- = zonkTcTyVar tv `thenNF_Tc` \ tv_ty ->
- if ignore_it tv_ty then
- returnNF_Tc (tidy_env, Nothing)
- else let
- (tidy_env1, tv1) = tidyOpenTyVar tidy_env tv
- (tidy_env2, tidy_ty) = tidyOpenType tidy_env1 tv_ty
- msg = sep [ptext SLIT("Type variable") <+> quotes (ppr tv1) <+> eq_stuff, nest 2 bound_at]
-
- eq_stuff | Just tv' <- Type.getTyVar_maybe tv_ty, tv == tv' = empty
- | otherwise = equals <+> ppr tv_ty
- -- It's ok to use Type.getTyVar_maybe because ty is zonked by now
-
- bound_at | isMutTyVar tv = mut_info -- The expected case
- | otherwise = empty
-
- mut_info = sep [ptext SLIT("is bound by the") <+> ppr (mutTyVarDetails tv),
- ptext SLIT("at") <+> ppr (getSrcLoc tv)]
- in
- returnNF_Tc (tidy_env2, Just msg)
-
------------------------
-find_frees tv tidy_env acc []
- = returnNF_Tc (tidy_env, acc)
-find_frees tv tidy_env acc (ftv:ftvs)
- = zonkTcTyVar ftv `thenNF_Tc` \ ty ->
- if tv `elemVarSet` tyVarsOfType ty then
- let
- (tidy_env', ftv') = tidyOpenTyVar tidy_env ftv
- in
- find_frees tv tidy_env' (ftv':acc) ftvs
- else
- find_frees tv tidy_env acc ftvs
-
-
-escape_msg sig_tv tv globs frees
- = mk_msg sig_tv <+> ptext SLIT("escapes") $$
- if not (null globs) then
- vcat [pp_it <+> ptext SLIT("is mentioned in the environment:"),
- nest 2 (vcat globs)]
- else if not (null frees) then
- vcat [ptext SLIT("It is reachable from the type variable(s)") <+> pprQuotedList frees,
- nest 2 (ptext SLIT("which") <+> is_are <+> ptext SLIT("free in the signature"))
- ]
- else
- empty -- Sigh. It's really hard to give a good error message
- -- all the time. One bad case is an existential pattern match
- where
- is_are | isSingleton frees = ptext SLIT("is")
- | otherwise = ptext SLIT("are")
- pp_it | sig_tv /= tv = ptext SLIT("It unifies with") <+> quotes (ppr tv) <> comma <+> ptext SLIT("which")
- | otherwise = ptext SLIT("It")
-
- vcat_first :: Int -> [SDoc] -> SDoc
- vcat_first n [] = empty
- vcat_first 0 (x:xs) = text "...others omitted..."
- vcat_first n (x:xs) = x $$ vcat_first (n-1) xs
-
-
-unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> thing
-mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv)
-\end{code}
+hoistForAllTys :: Type -> Type
+-- Used for user-written type signatures only
+-- Move all the foralls and constraints to the top
+-- e.g. T -> forall a. a ==> forall a. T -> a
+-- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
+--
+-- Also: eliminate duplicate constraints. These can show up
+-- when hoisting constraints, notably implicit parameters.
+--
+-- We want to 'look through' type synonyms when doing this
+-- so it's better done on the Type than the HsType
-These two context are used with checkSigTyVars
-
-\begin{code}
-sigCtxt :: Message -> [TcTyVar] -> TcThetaType -> TcTauType
- -> TidyEnv -> NF_TcM (TidyEnv, Message)
-sigCtxt when sig_tyvars sig_theta sig_tau tidy_env
- = zonkTcType sig_tau `thenNF_Tc` \ actual_tau ->
- let
- (env1, tidy_sig_tyvars) = tidyOpenTyVars tidy_env sig_tyvars
- (env2, tidy_sig_rho) = tidyOpenType env1 (mkRhoTy sig_theta sig_tau)
- (env3, tidy_actual_tau) = tidyOpenType env2 actual_tau
- msg = vcat [ptext SLIT("Signature type: ") <+> pprType (mkForAllTys tidy_sig_tyvars tidy_sig_rho),
- ptext SLIT("Type to generalise:") <+> pprType tidy_actual_tau,
- when
- ]
+hoistForAllTys ty
+ = let
+ no_shadow_ty = deShadowTy ty
+ -- Running over ty with an empty substitution gives it the
+ -- no-shadowing property. This is important. For example:
+ -- type Foo r = forall a. a -> r
+ -- foo :: Foo (Foo ())
+ -- Here the hoisting should give
+ -- foo :: forall a a1. a -> a1 -> ()
+ --
+ -- What about type vars that are lexically in scope in the envt?
+ -- We simply rely on them having a different unique to any
+ -- binder in 'ty'. Otherwise we'd have to slurp the in-scope-tyvars
+ -- out of the envt, which is boring and (I think) not necessary.
in
- returnNF_Tc (env3, msg)
-
-sigPatCtxt bound_tvs bound_ids tidy_env
- = returnNF_Tc (env1,
- sep [ptext SLIT("When checking a pattern that binds"),
- nest 4 (vcat (zipWith ppr_id show_ids tidy_tys))])
+ case hoist no_shadow_ty of
+ (tvs, theta, body) -> mkForAllTys tvs (mkFunTys (nubBy tcEqType theta) body)
+ -- The 'nubBy' eliminates duplicate constraints,
+ -- notably implicit parameters
where
- show_ids = filter is_interesting bound_ids
- is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
-
- (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
- ppr_id id ty = ppr id <+> dcolon <+> ppr ty
- -- Don't zonk the types so we get the separate, un-unified versions
+ hoist ty
+ | (tvs1, body_ty) <- tcSplitForAllTys ty,
+ not (null tvs1)
+ = case hoist body_ty of
+ (tvs2,theta,tau) -> (tvs1 ++ tvs2, theta, tau)
+
+ | Just (arg, res) <- tcSplitFunTy_maybe ty
+ = let
+ arg' = hoistForAllTys arg -- Don't forget to apply hoist recursively
+ in -- to the argument type
+ if (isPredTy arg') then
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, arg':theta, tau)
+ else
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, theta, mkFunTy arg' tau)
+
+ | otherwise = ([], [], ty)
\end{code}
pp_thing (AGlobal (AClass _)) = ptext SLIT("Class")
pp_thing (AGlobal (AnId _)) = ptext SLIT("Identifier")
pp_thing (ATyVar _) = ptext SLIT("Type variable")
- pp_thing (ATcId _) = ptext SLIT("Local identifier")
+ pp_thing (ATcId _ _) = ptext SLIT("Local identifier")
pp_thing (AThing _) = ptext SLIT("Utterly bogus")
\end{code}