\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsSigType, tcHsBoxedSigType,
- tcContext, tcClassContext,
+module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta,
+ UserTypeCtxt(..),
-- Kind checking
kcHsTyVar, kcHsTyVars, mkTyClTyVars,
- kcHsType, kcHsSigType, kcHsBoxedSigType, kcHsContext,
- kcTyVarScope, newSigTyVars, mkImmutTyVars,
+ kcHsType, kcHsSigType, kcHsSigTypes,
+ kcHsLiftedSigType, kcHsContext,
+ tcScopedTyVars, tcHsTyVars, mkImmutTyVars,
TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
checkSigTyVars, sigCtxt, sigPatCtxt
#include "HsVersions.h"
-import HsSyn ( HsType(..), HsTyVarBndr(..), HsUsageAnn(..),
+import HsSyn ( HsType(..), HsTyVarBndr(..),
Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames )
import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig )
import TcHsSyn ( TcId )
import TcMonad
-import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars,
- tcExtendUVarEnv, tcLookupUVar,
- tcGetGlobalTyVars, valueEnvIds,
- TyThing(..), tyThingKind, tcExtendKindEnv
+import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
+ tcGetGlobalTyVars, tcEnvTcIds, tcEnvTyVars,
+ TyThing(..), TcTyThing(..), tcExtendKindEnv
)
-import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType,
- newKindVar, tcInstSigVar,
- zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar
+import TcMType ( newKindVar, tcInstSigVars,
+ zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar,
+ unifyKind, unifyOpenTypeKind,
+ checkValidType, UserTypeCtxt(..), pprUserTypeCtxt
)
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr,
- instFunDeps, instFunDepsOfTheta )
-import FunDeps ( tyVarFunDep, oclose )
-import TcUnify ( unifyKind, unifyKinds, unifyOpenTypeKind )
-import Type ( Type, Kind, PredType(..), ThetaType, UsageAnn(..),
- mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, mkUsgTy,
- mkUsForAllTy, zipFunTys, hoistForAllTys,
- mkSigmaTy, mkDictTy, mkPredTy, mkTyConApp,
- mkAppTys, splitForAllTys, splitRhoTy, mkRhoTy,
- boxedTypeKind, unboxedTypeKind, mkArrowKind,
- mkArrowKinds, getTyVar_maybe, getTyVar, splitFunTy_maybe,
+import TcType ( Type, Kind, SourceType(..), ThetaType,
+ mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
+ tcSplitForAllTys, tcSplitRhoTy,
+ hoistForAllTys, allDistinctTyVars,
+ zipFunTys,
+ mkSigmaTy, mkPredTy, mkTyConApp,
+ mkAppTys, mkRhoTy,
+ liftedTypeKind, unliftedTypeKind, mkArrowKind,
+ mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe,
tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars,
- tyVarsOfType, tyVarsOfTypes, tyVarsOfPred, mkForAllTys,
- classesOfPreds
+ tyVarsOfType, mkForAllTys
)
-import PprType ( pprConstraint, pprType, pprPred )
+import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
+import PprType ( pprType )
import Subst ( mkTopTyVarSubst, substTy )
-import Id ( mkVanillaId, idName, idType, idFreeTyVars )
-import Var ( TyVar, mkTyVar, tyVarKind, mkNamedUVar, varName )
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, idName, idType )
+import Var ( Id, Var, TyVar, mkTyVar, tyVarKind )
import VarEnv
import VarSet
import ErrUtils ( Message )
import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind )
-import Class ( ClassContext, classArity, classTyCon )
-import Name ( Name, OccName, isLocallyDefined )
-import TysWiredIn ( mkListTy, mkTupleTy )
-import UniqFM ( elemUFM, foldUFM )
+import Class ( classTyCon )
+import Name ( Name )
+import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
import BasicTypes ( Boxity(..) )
import SrcLoc ( SrcLoc )
-import Util ( mapAccumL, isSingleton, removeDups )
+import Util ( mapAccumL, isSingleton )
import Outputable
+
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{Checking types}
+%* *
+%************************************************************************
+
+Generally speaking we now type-check types in three phases
+
+ 1. Kind check the HsType [kcHsType]
+ 2. Convert from HsType to Type, and hoist the foralls [tcHsType]
+ 3. Check the validity of the resultint type [checkValidType]
+
+Often these steps are done one after the othe (tcHsSigType).
+But in mutually recursive groups of type and class decls we do
+ 1 kind-check the whole group
+ 2 build TyCons/Classes in a knot-tied wa
+ 3 check the validity of types in the now-unknotted TyCons/Classes
+
+\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_`
+ tcHsType ty
+ ) `thenTc` \ ty' ->
+ checkValidType ctxt ty' `thenTc_`
+ returnTc ty'
+
+checkTypeCtxt ctxt ty
+ = vcat [ptext SLIT("In the type:") <+> ppr ty,
+ ptext SLIT("While checking") <+> pprUserTypeCtxt ctxt ]
+
+tcHsType :: RenamedHsType -> TcM Type
+ -- Don't do kind checking, nor validity checking,
+ -- but do hoist for-alls to the top
+ -- 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')
+
+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
+
+-- In interface files the type is already kinded,
+-- and we definitely don't want to hoist for-alls.
+-- Otherwise we'll change
+-- dmfail :: forall m:(*->*) Monad m => forall a:* => String -> m a
+-- into
+-- dmfail :: forall m:(*->*) a:* Monad m => String -> m a
+-- which definitely isn't right!
+tcIfaceType ty = tc_type ty
\end{code}
1b. Apply the kind checker
1c. Zonk the resulting kinds
-The kind checker is passed to kcTyVarScope as an argument.
+The kind checker is passed to tcHsTyVars as an argument.
For example, when we find
(forall a m. m a -> m a)
makes a get kind *, and m get kind *->*. Now we typecheck (m a -> m a)
in an environment that binds a and m suitably.
-The kind checker passed to kcTyVarScope needs to look at enough to
+The kind checker passed to tcHsTyVars needs to look at enough to
establish the kind of the tyvar:
* For a group of type and class decls, it's just the group, not
the rest of the program
a::(*->*)-> *, b::*->*
\begin{code}
-kcTyVarScope :: [HsTyVarBndr Name]
- -> TcM s a -- The kind checker
- -> TcM s [(Name,Kind)]
- -- Do a kind check to find out the kinds of the type variables
- -- Then return a bunch of name-kind pairs, from which to
- -- construct the type variables. We don't return the tyvars
- -- themselves because sometimes we want mutable ones and
- -- sometimes we want immutable ones.
-
-kcTyVarScope [] kind_check = returnTc []
+-- tcHsTyVars is used for type variables in type signatures
+-- e.g. forall a. a->a
+-- They are immutable, because they scope only over the signature
+-- They may or may not be explicitly-kinded
+tcHsTyVars :: [HsTyVarBndr Name]
+ -> TcM a -- The kind checker
+ -> ([TyVar] -> TcM b)
+ -> TcM b
+
+tcHsTyVars [] kind_check thing_inside = thing_inside []
-- A useful short cut for a common case!
-kcTyVarScope tv_names kind_check
+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
+ zonkKindEnv tv_names_w_kinds `thenNF_Tc` \ tvs_w_kinds ->
+ let
+ tyvars = mkImmutTyVars tvs_w_kinds
+ in
+ tcExtendTyVarEnv tyvars (thing_inside tyvars)
+
+-- tcScopedTyVars is used for scoped type variables
+-- e.g. \ (x::a) (y::a) -> x+y
+-- They never have explicit kinds (because this is source-code only)
+-- They are mutable (because they can get bound to a more specific type)
+tcScopedTyVars :: [Name]
+ -> TcM a -- The kind checker
+ -> TcM b
+ -> TcM b
+tcScopedTyVars [] kind_check thing_inside = thing_inside
+
+tcScopedTyVars tv_names kind_check thing_inside
+ = mapNF_Tc newNamedKindVar tv_names `thenTc` \ kind_env ->
+ tcExtendKindEnv kind_env kind_check `thenTc_`
+ zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds ->
+ listTc [tcNewMutTyVar name kind | (name, kind) <- tvs_w_kinds] `thenNF_Tc` \ tyvars ->
+ tcExtendTyVarEnv tyvars thing_inside
\end{code}
\begin{code}
-kcHsTyVar :: HsTyVarBndr name -> NF_TcM s (name, TcKind)
-kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM s [(name, TcKind)]
+kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind)
+kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)]
-kcHsTyVar (UserTyVar name) = newKindVar `thenNF_Tc` \ kind ->
- returnNF_Tc (name, kind)
+kcHsTyVar (UserTyVar name) = newNamedKindVar name
kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (name, kind)
kcHsTyVars tvs = mapNF_Tc kcHsTyVar tvs
+newNamedKindVar name = newKindVar `thenNF_Tc` \ kind ->
+ returnNF_Tc (name, kind)
+
---------------------------
-kcBoxedType :: RenamedHsType -> TcM s ()
- -- The type ty must be a *boxed* *type*
-kcBoxedType ty
+kcLiftedType :: RenamedHsType -> TcM ()
+ -- The type ty must be a *lifted* *type*
+kcLiftedType ty
= kcHsType ty `thenTc` \ kind ->
tcAddErrCtxt (typeKindCtxt ty) $
- unifyKind boxedTypeKind kind
+ unifyKind liftedTypeKind kind
---------------------------
-kcTypeType :: RenamedHsType -> TcM s ()
- -- The type ty must be a *type*, but it can be boxed or unboxed.
+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) $
unifyOpenTypeKind kind
---------------------------
-kcHsSigType, kcHsBoxedSigType :: RenamedHsType -> TcM s ()
+kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM ()
-- Used for type signatures
-kcHsSigType = kcTypeType
-kcHsBoxedSigType = kcBoxedType
+kcHsSigType = kcTypeType
+kcHsSigTypes tys = mapTc_ kcHsSigType tys
+kcHsLiftedSigType = kcLiftedType
---------------------------
-kcHsType :: RenamedHsType -> TcM s TcKind
-kcHsType (HsTyVar name)
- = tcLookupTy name `thenTc` \ thing ->
- case thing of
- ATyVar tv -> returnTc (tyVarKind tv)
- ATyCon tc -> returnTc (tyConKind tc)
- AThing k -> returnTc k
- other -> failWithTc (wrongThingErr "type" thing name)
-
-kcHsType (HsUsgTy _ ty) = kcHsType ty
-kcHsType (HsUsgForAllTy _ ty) = kcHsType ty
+kcHsType :: RenamedHsType -> TcM TcKind
+kcHsType (HsTyVar name) = kcTyVar name
kcHsType (HsListTy ty)
- = kcBoxedType ty `thenTc` \ tau_ty ->
- returnTc boxedTypeKind
+ = kcLiftedType ty `thenTc` \ tau_ty ->
+ returnTc liftedTypeKind
-kcHsType (HsTupleTy (HsTupCon _ Boxed) tys)
- = mapTc kcBoxedType tys `thenTc_`
- returnTc boxedTypeKind
-
-kcHsType (HsTupleTy (HsTupCon _ Unboxed) tys)
- = mapTc kcTypeType tys `thenTc_`
- returnTc unboxedTypeKind
+kcHsType (HsTupleTy (HsTupCon _ boxity _) tys)
+ = mapTc kcTypeType tys `thenTc_`
+ returnTc (case boxity of
+ Boxed -> liftedTypeKind
+ Unboxed -> unliftedTypeKind)
kcHsType (HsFunTy ty1 ty2)
= kcTypeType ty1 `thenTc_`
kcTypeType ty2 `thenTc_`
- returnTc boxedTypeKind
+ 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' ->
+ kcAppKind op_kind' ty2_kind
+
kcHsType (HsPredTy pred)
= kcHsPred pred `thenTc_`
- returnTc boxedTypeKind
+ returnTc liftedTypeKind
kcHsType ty@(HsAppTy ty1 ty2)
- = kcHsType ty1 `thenTc` \ tc_kind ->
- kcHsType ty2 `thenTc` \ arg_kind ->
-
+ = kcHsType ty1 `thenTc` \ tc_kind ->
+ kcHsType ty2 `thenTc` \ arg_kind ->
tcAddErrCtxt (appKindCtxt (ppr ty)) $
- case splitFunTy_maybe tc_kind of
+ kcAppKind tc_kind arg_kind
+
+kcHsType (HsForAllTy (Just tv_names) context ty)
+ = kcHsTyVars tv_names `thenNF_Tc` \ kind_env ->
+ tcExtendKindEnv kind_env $
+ kcHsContext context `thenTc_`
+ kcHsType ty `thenTc_`
+ returnTc 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
Nothing -> newKindVar `thenNF_Tc` \ res_kind ->
- unifyKind tc_kind (mkArrowKind arg_kind res_kind) `thenTc_`
+ unifyKind fun_kind (mkArrowKind arg_kind res_kind) `thenTc_`
returnTc res_kind
-kcHsType (HsForAllTy (Just tv_names) context ty)
- = kcHsTyVars tv_names `thenNF_Tc` \ kind_env ->
- tcExtendKindEnv kind_env $
- kcHsContext context `thenTc_`
- kcHsType ty `thenTc` \ kind ->
-
- -- Context behaves like a function type
- -- This matters. Return-unboxed-tuple analysis can
- -- give overloaded functions like
- -- f :: forall a. Num a => (# a->a, a->a #)
- -- And we want these to get through the type checker
- returnTc (if null context then
- kind
- else
- boxedTypeKind)
---------------------------
kcHsContext ctxt = mapTc_ kcHsPred ctxt
-kcHsPred :: RenamedHsPred -> TcM s ()
-kcHsPred pred@(HsPIParam name ty)
+kcHsPred :: RenamedHsPred -> TcM ()
+kcHsPred pred@(HsIParam name ty)
= tcAddErrCtxt (appKindCtxt (ppr pred)) $
- kcBoxedType ty
+ kcLiftedType ty
-kcHsPred pred@(HsPClass cls tys)
+kcHsPred pred@(HsClassP cls tys)
= tcAddErrCtxt (appKindCtxt (ppr pred)) $
- tcLookupTy cls `thenNF_Tc` \ thing ->
- (case thing of
- AClass cls -> returnTc (tyConKind (classTyCon cls))
- AThing kind -> returnTc kind
- other -> failWithTc (wrongThingErr "class" thing cls)) `thenTc` \ kind ->
- mapTc kcHsType tys `thenTc` \ arg_kinds ->
- unifyKind kind (mkArrowKinds arg_kinds boxedTypeKind)
+ kcClass cls `thenTc` \ kind ->
+ mapTc kcHsType tys `thenTc` \ arg_kinds ->
+ unifyKind kind (mkArrowKinds arg_kinds liftedTypeKind)
+
+ ---------------------------
+kcTyVar name -- Could be a tyvar or a tycon
+ = tcLookup name `thenTc` \ thing ->
+ case thing of
+ AThing kind -> returnTc kind
+ ATyVar tv -> returnTc (tyVarKind tv)
+ AGlobal (ATyCon tc) -> returnTc (tyConKind tc)
+ other -> failWithTc (wrongThingErr "type" thing name)
+
+kcClass cls -- Must be a class
+ = tcLookup cls `thenNF_Tc` \ thing ->
+ case thing of
+ AThing kind -> returnTc kind
+ AGlobal (AClass cls) -> returnTc (tyConKind (classTyCon cls))
+ other -> failWithTc (wrongThingErr "class" thing cls)
\end{code}
%************************************************************************
%* *
-\subsection{Checking types}
+\subsection{tc_type}
%* *
%************************************************************************
-tcHsType and tcHsTypeKind
+tc_type, the main work horse
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-tcHsSigType and tcHsBoxedSigType are used for type signatures written by the programmer
+ -------------------
+ *** BIG WARNING ***
+ -------------------
- * We hoist any inner for-alls to the top
+tc_type is used to typecheck the types in the RHS of data
+constructors. In the case of recursive data types, that means that
+the type constructors themselves are (partly) black holes. e.g.
- * Notice that we kind-check first, because the type-check assumes
- that the kinds are already checked.
- * They are only called when there are no kind vars in the environment
- so the kind returned is indeed a Kind not a TcKind
+ data T a = MkT a [T a]
-\begin{code}
-tcHsSigType :: RenamedHsType -> TcM s TcType
-tcHsSigType ty
- = kcTypeType ty `thenTc_`
- tcHsType ty `thenTc` \ ty' ->
- returnTc (hoistForAllTys ty')
-
-tcHsBoxedSigType :: RenamedHsType -> TcM s Type
-tcHsBoxedSigType ty
- = kcBoxedType ty `thenTc_`
- tcHsType ty `thenTc` \ ty' ->
- returnTc (hoistForAllTys ty')
-\end{code}
+While typechecking the [T a] on the RHS, T itself is not yet fully
+defined. That in turn places restrictions on what you can check in
+tcHsType; if you poke on too much you get a black hole. I keep
+forgetting this, hence this warning!
+So tc_type does no validity-checking. Instead that's all done
+by TcMType.checkValidType
+
+ --------------------------
+ *** END OF BIG WARNING ***
+ --------------------------
-The main work horse
-~~~~~~~~~~~~~~~~~~~
\begin{code}
-tcHsType :: RenamedHsType -> TcM s Type
-tcHsType ty@(HsTyVar name)
+tc_type :: RenamedHsType -> TcM Type
+
+tc_type ty@(HsTyVar name)
= tc_app ty []
-tcHsType (HsListTy ty)
- = tcHsType ty `thenTc` \ tau_ty ->
+tc_type (HsListTy ty)
+ = tc_type ty `thenTc` \ tau_ty ->
returnTc (mkListTy tau_ty)
-tcHsType (HsTupleTy (HsTupCon _ boxity) tys)
- = mapTc tcHsType tys `thenTc` \ tau_tys ->
- returnTc (mkTupleTy boxity (length tys) tau_tys)
+tc_type (HsTupleTy (HsTupCon _ boxity arity) tys)
+ = ASSERT( arity == length tys )
+ tc_types tys `thenTc` \ tau_tys ->
+ returnTc (mkTupleTy boxity arity tau_tys)
-tcHsType (HsFunTy ty1 ty2)
- = tcHsType ty1 `thenTc` \ tau_ty1 ->
- tcHsType ty2 `thenTc` \ tau_ty2 ->
+tc_type (HsFunTy ty1 ty2)
+ = tc_type ty1 `thenTc` \ tau_ty1 ->
+ tc_type ty2 `thenTc` \ tau_ty2 ->
returnTc (mkFunTy tau_ty1 tau_ty2)
-tcHsType (HsAppTy ty1 ty2)
- = tc_app ty1 [ty2]
+tc_type (HsNumTy n)
+ = ASSERT(n== 1)
+ returnTc (mkTyConApp genUnitTyCon [])
-tcHsType (HsPredTy pred)
- = tcClassAssertion True pred `thenTc` \ pred' ->
- returnTc (mkPredTy pred')
+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]
-tcHsType (HsUsgTy usg ty)
- = newUsg usg `thenTc` \ usg' ->
- tcHsType ty `thenTc` \ tc_ty ->
- returnTc (mkUsgTy usg' tc_ty)
- where
- newUsg usg = case usg of
- HsUsOnce -> returnTc UsOnce
- HsUsMany -> returnTc UsMany
- HsUsVar uv_name -> tcLookupUVar uv_name `thenTc` \ uv ->
- returnTc (UsVar uv)
+tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2]
-tcHsType (HsUsgForAllTy uv_name ty)
+tc_type (HsPredTy pred)
+ = tc_pred pred `thenTc` \ pred' ->
+ returnTc (mkPredTy pred')
+
+tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty)
= let
- uv = mkNamedUVar uv_name
+ kind_check = kcHsContext ctxt `thenTc_` kcHsType ty
in
- tcExtendUVarEnv uv_name uv $
- tcHsType ty `thenTc` \ tc_ty ->
- returnTc (mkUsForAllTy uv tc_ty)
+ tcHsTyVars tv_names kind_check $ \ tyvars ->
+ mapTc tc_pred ctxt `thenTc` \ theta ->
+ tc_type ty `thenTc` \ tau ->
+ returnTc (mkSigmaTy tyvars theta tau)
-tcHsType full_ty@(HsForAllTy (Just tv_names) ctxt ty)
- = kcTyVarScope tv_names
- (kcHsContext ctxt `thenTc_` kcHsType ty) `thenTc` \ tv_kinds ->
- let
- forall_tyvars = mkImmutTyVars tv_kinds
- in
- tcExtendTyVarEnv forall_tyvars $
- tcContext ctxt `thenTc` \ theta ->
- tcHsType ty `thenTc` \ tau ->
- let
- -- Check for ambiguity
- -- forall V. P => tau
- -- is ambiguous if P contains generic variables
- -- (i.e. one of the Vs) that are not mentioned in tau
- --
- -- However, we need to take account of functional dependencies
- -- when we speak of 'mentioned in tau'. Example:
- -- class C a b | a -> b where ...
- -- Then the type
- -- forall x y. (C x y) => x
- -- is not ambiguous because x is mentioned and x determines y
- --
- -- NOTE: In addition, GHC insists that at least one type variable
- -- in each constraint is in V. So we disallow a type like
- -- forall a. Eq b => b -> b
- -- even in a scope where b is in scope.
- -- This is the is_free test below.
-
- tau_vars = tyVarsOfType tau
- fds = instFunDepsOfTheta theta
- tvFundep = tyVarFunDep fds
- extended_tau_vars = oclose tvFundep tau_vars
- is_ambig ct_var = (ct_var `elem` forall_tyvars) &&
- not (ct_var `elemUFM` extended_tau_vars)
- is_free ct_var = not (ct_var `elem` forall_tyvars)
-
- check_pred pred = checkTc (not any_ambig) (ambigErr pred full_ty) `thenTc_`
- checkTc (not all_free) (freeErr pred full_ty)
- where
- ct_vars = varSetElems (tyVarsOfPred pred)
- any_ambig = is_source_polytype && any is_ambig ct_vars
- all_free = all is_free ct_vars
-
- -- Check ambiguity only for source-program types, not
- -- for types coming from inteface files. The latter can
- -- legitimately have ambiguous types. Example
- -- class S a where s :: a -> (Int,Int)
- -- instance S Char where s _ = (1,1)
- -- f:: S a => [a] -> Int -> (Int,Int)
- -- f (_::[a]) x = (a*x,b)
- -- where (a,b) = s (undefined::a)
- -- Here the worker for f gets the type
- -- fw :: forall a. S a => Int -> (# Int, Int #)
- --
- -- If the list of tv_names is empty, we have a monotype,
- -- and then we don't need to check for ambiguity either,
- -- because the test can't fail (see is_ambig).
- is_source_polytype = case tv_names of
- (UserTyVar _ : _) -> True
- other -> False
- in
- mapTc check_pred theta `thenTc_`
- returnTc (mkSigmaTy forall_tyvars theta tau)
+tc_types arg_tys = mapTc tc_type arg_tys
\end{code}
Help functions for type applications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
+tc_app :: RenamedHsType -> [RenamedHsType] -> TcM Type
tc_app (HsAppTy ty1 ty2) tys
= tc_app ty1 (ty2:tys)
tc_app ty tys
= tcAddErrCtxt (appKindCtxt pp_app) $
- mapTc tcHsType tys `thenTc` \ arg_tys ->
- tc_fun_type ty arg_tys
+ tc_types tys `thenTc` \ 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)
where
pp_app = ppr ty <+> sep (map pprParendHsType tys)
-- But not quite; for synonyms it checks the correct arity, and builds a SynTy
-- hence the rather strange functionality.
-tc_fun_type (HsTyVar name) arg_tys
- = tcLookupTy name `thenTc` \ thing ->
+tc_fun_type name arg_tys
+ = tcLookup name `thenTc` \ thing ->
case thing of
ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys)
- ATyCon tc | isSynTyCon tc -> checkTc arity_ok err_msg `thenTc_`
- returnTc (mkAppTys (mkSynTy tc (take arity arg_tys))
- (drop arity arg_tys))
-
- | otherwise -> returnTc (mkTyConApp tc arg_tys)
- where
+ AGlobal (ATyCon tc)
+ | isSynTyCon tc -> returnTc (mkAppTys (mkSynTy tc (take arity arg_tys))
+ (drop arity arg_tys))
+ | otherwise -> returnTc (mkTyConApp tc arg_tys)
+ where
+ arity = tyConArity tc
- arity_ok = arity <= n_args
- arity = tyConArity tc
- -- It's OK to have an *over-applied* type synonym
- -- data Tree a b = ...
- -- type Foo a = Tree [a]
- -- f :: Foo a b -> ...
- err_msg = arityErr "Type synonym" name arity n_args
- n_args = length arg_tys
other -> failWithTc (wrongThingErr "type constructor" thing name)
-
-tc_fun_type ty arg_tys
- = tcHsType ty `thenTc` \ fun_ty ->
- returnNF_Tc (mkAppTys fun_ty arg_tys)
\end{code}
Contexts
~~~~~~~~
\begin{code}
-tcClassContext :: RenamedContext -> TcM s ClassContext
- -- Used when we are expecting a ClassContext (i.e. no implicit params)
-tcClassContext context
- = tcContext context `thenTc` \ theta ->
- returnTc (classesOfPreds theta)
-
-tcContext :: RenamedContext -> TcM s ThetaType
-tcContext context = mapTc (tcClassAssertion False) context
-
-tcClassAssertion ccall_ok assn@(HsPClass class_name tys)
+tc_pred assn@(HsClassP class_name tys)
= tcAddErrCtxt (appKindCtxt (ppr assn)) $
- mapTc tcHsType tys `thenTc` \ arg_tys ->
- tcLookupTy class_name `thenTc` \ thing ->
+ tc_types tys `thenTc` \ arg_tys ->
+ tcLookupGlobal class_name `thenTc` \ thing ->
case thing of
- AClass clas -> checkTc (arity == n_tys) err `thenTc_`
- returnTc (Class clas arg_tys)
- where
- arity = classArity clas
- n_tys = length tys
- err = arityErr "Class" class_name arity n_tys
-
- other -> failWithTc (wrongThingErr "class" thing class_name)
+ AClass clas -> returnTc (ClassP clas arg_tys)
+ other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name)
-tcClassAssertion ccall_ok assn@(HsPIParam name ty)
+tc_pred assn@(HsIParam name ty)
= tcAddErrCtxt (appKindCtxt (ppr assn)) $
- tcHsType ty `thenTc` \ arg_ty ->
+ tc_type ty `thenTc` \ arg_ty ->
returnTc (IParam name arg_ty)
\end{code}
+
%************************************************************************
%* *
\subsection{Type variables, with knot tying!}
\begin{code}
mkImmutTyVars :: [(Name,Kind)] -> [TyVar]
-newSigTyVars :: [(Name,Kind)] -> NF_TcM s [TcTyVar]
-
mkImmutTyVars pairs = [mkTyVar name kind | (name, kind) <- pairs]
-newSigTyVars pairs = listNF_Tc [tcNewSigTyVar name kind | (name,kind) <- pairs]
mkTyClTyVars :: Kind -- Kind of the tycon or class
-> [HsTyVarBndr Name]
\begin{code}
-tcTySig :: RenamedSig -> TcM s TcSigInfo
+tcTySig :: RenamedSig -> TcM TcSigInfo
tcTySig (Sig v ty src_loc)
= tcAddSrcLoc src_loc $
- tcAddErrCtxt (tcsigCtxt v) $
- tcHsSigType ty `thenTc` \ sigma_tc_ty ->
- mkTcSig (mkVanillaId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
+ tcHsSigType (FunSigCtxt v) ty `thenTc` \ sigma_tc_ty ->
+ mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
returnTc sig
-mkTcSig :: TcId -> SrcLoc -> NF_TcM s TcSigInfo
+mkTcSig :: TcId -> SrcLoc -> NF_TcM TcSigInfo
mkTcSig poly_id src_loc
= -- Instantiate this type
-- It's important to do this even though in the error-free case
-- typechecking the rest of the program with the function bound
-- to a pristine type, namely sigma_tc_ty
let
- (tyvars, rho) = splitForAllTys (idType poly_id)
+ (tyvars, rho) = tcSplitForAllTys (idType poly_id)
in
- mapNF_Tc tcInstSigVar tyvars `thenNF_Tc` \ tyvars' ->
+ tcInstSigVars 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') = splitRhoTy rho'
+
+ (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
tyvar_tys'
theta' tau' `thenNF_Tc` \ inst ->
-- We make a Method even if it's not overloaded; no harm
- instFunDeps SignatureOrigin theta' `thenNF_Tc` \ fds ->
- returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToIdBndr inst) (inst : fds) src_loc)
+ returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc)
where
name = idName poly_id
\end{code}
\begin{code}
checkSigTyVars :: [TcTyVar] -- Universally-quantified type variables in the signature
-> TcTyVarSet -- Tyvars that are free in the type signature
- -- These should *already* be in the global-var set, and are
- -- used here only to improve the error message
- -> TcM s [TcTyVar] -- Zonked signature type variables
+ -- 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 (all_ok sig_tys globals)
+ checkTcM (allDistinctTyVars sig_tys globals)
(complain sig_tys globals) `thenTc_`
- returnTc (map (getTyVar "checkSigTyVars") sig_tys)
+ returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys)
where
- all_ok [] acc = True
- all_ok (ty:tys) acc = case getTyVar_maybe ty of
- Nothing -> False -- Point (a)
- Just tv | tv `elemVarSet` acc -> False -- Point (b) or (c)
- | otherwise -> all_ok tys (acc `extendVarSet` tv)
-
-
complain sig_tys globals
= -- For the in-scope ones, zonk them and construct a map
-- from the zonked tyvar to the in-scope one
-- If any of the in-scope tyvars zonk to a type, then ignore them;
-- that'll be caught later when we back up to their type sig
- tcGetInScopeTyVars `thenNF_Tc` \ in_scope_tvs ->
+ tcGetEnv `thenNF_Tc` \ env ->
+ let
+ in_scope_tvs = tcEnvTyVars env
+ in
zonkTcTyVars in_scope_tvs `thenNF_Tc` \ in_scope_tys ->
let
in_scope_assoc = [ (zonked_tv, in_scope_tv)
| (z_ty, in_scope_tv) <- in_scope_tys `zip` in_scope_tvs,
- Just zonked_tv <- [getTyVar_maybe z_ty]
+ Just zonked_tv <- [tcGetTyVar_maybe z_ty]
]
in_scope_env = mkVarEnv in_scope_assoc
in
main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
- check (env, acc, msgs) (sig_tyvar,ty)
+ 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 getTyVar_maybe ty of {
+ = case tcGetTyVar_maybe ty of {
Nothing -> -- Error (a)!
- returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr ty) : msgs) ;
+ 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) or (d)!
- returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr sig_tyvar') : msgs) ;
+ returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
+ where
+ thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar')
- Nothing ->
+ ; Nothing ->
if tv `elemVarSet` globals -- Error (c)! Type variable escapes
-- The least comprehensible, so put it last
- then tcGetValueEnv `thenNF_Tc` \ ve ->
- find_globals tv env [] (valueEnvIds ve) `thenNF_Tc` \ (env1, globs) ->
- find_frees tv env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (env2, frees) ->
- returnNF_Tc (env2, acc, escape_msg sig_tyvar tv globs frees : msgs)
+ -- Game plan:
+ -- a) get the local TcIds 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 [] (tcEnvTcIds 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 (env, extendVarEnv acc tv sig_tyvar, msgs)
+ 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
+ -> [(Name,Type)]
+ -> [Id]
+ -> NF_TcM (TidyEnv,[(Name,Type)])
+
find_globals tv tidy_env acc []
= returnNF_Tc (tidy_env, acc)
find_globals tv tidy_env acc (id:ids)
- | not (isLocallyDefined id) ||
- isEmptyVarSet (idFreeTyVars id)
+ | isEmptyVarSet (idFreeTyVars id)
= find_globals tv tidy_env acc ids
| otherwise
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") <+> quotes thing
+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}
\begin{code}
sigCtxt :: Message -> [TcTyVar] -> TcThetaType -> TcTauType
- -> TidyEnv -> NF_TcM s (TidyEnv, Message)
+ -> TidyEnv -> NF_TcM (TidyEnv, Message)
sigCtxt when sig_tyvars sig_theta sig_tau tidy_env
= zonkTcType sig_tau `thenNF_Tc` \ actual_tau ->
let
%************************************************************************
\begin{code}
-tcsigCtxt v = ptext SLIT("In a type signature for") <+> quotes (ppr v)
-
-typeCtxt ty = ptext SLIT("In the type") <+> quotes (ppr ty)
-
typeKindCtxt :: RenamedHsType -> Message
typeKindCtxt ty = sep [ptext SLIT("When checking that"),
nest 2 (quotes (ppr ty)),
appKindCtxt :: SDoc -> Message
appKindCtxt pp = ptext SLIT("When checking kinds in") <+> quotes pp
-wrongThingErr expected actual name
- = pp_actual actual <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected
+wrongThingErr expected thing name
+ = pp_thing thing <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected
where
- pp_actual (ATyCon _) = ptext SLIT("Type constructor")
- pp_actual (AClass _) = ptext SLIT("Class")
- pp_actual (ATyVar _) = ptext SLIT("Type variable")
- pp_actual (AThing _) = ptext SLIT("Utterly bogus")
-
-ambigErr pred ty
- = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred),
- nest 4 (ptext SLIT("for the type:") <+> ppr ty),
- nest 4 (ptext SLIT("Each forall'd type variable mentioned by the constraint must appear after the =>"))]
-
-freeErr pred ty
- = sep [ptext SLIT("The constraint") <+> quotes (pprPred pred) <+>
- ptext SLIT("does not mention any of the universally quantified type variables"),
- nest 4 (ptext SLIT("in the type") <+> quotes (ppr ty))
- ]
+ pp_thing (AGlobal (ATyCon _)) = ptext SLIT("Type constructor")
+ 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 (AThing _) = ptext SLIT("Utterly bogus")
\end{code}