%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsTypeKind, tcContext, tcTyVarScope ) where
+module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta,
+ UserTypeCtxt(..),
+
+ -- Kind checking
+ kcHsTyVar, kcHsTyVars, mkTyClTyVars,
+ kcHsType, kcHsSigType, kcHsSigTypes,
+ kcHsLiftedSigType, kcHsContext,
+ tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars,
+
+ TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
+ checkSigTyVars, sigCtxt, sigPatCtxt
+ ) where
#include "HsVersions.h"
-import HsSyn ( HsType(..), HsTyVar(..), pprContext )
-import RnHsSyn ( RenamedHsType(..), RenamedContext(..) )
+import HsSyn ( HsType(..), HsTyVarBndr(..),
+ Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames )
+import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars )
+import TcHsSyn ( TcId )
import TcMonad
-import TcEnv ( tcLookupTyVar, tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv )
-import TcKind ( TcKind, mkBoxedTypeKind, mkTypeKind, mkArrowKind,
- unifyKind, unifyKinds, newKindVar,
- kindToTcKind, tcDefaultKind
+import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
+ tcGetGlobalTyVars, tcLEnvElts, tcInLocalScope,
+ TyThing(..), TcTyThing(..), tcExtendKindEnv
+ )
+import TcMType ( newKindVar, tcInstSigTyVars,
+ zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar,
+ unifyKind, unifyOpenTypeKind,
+ checkValidType, UserTypeCtxt(..), pprUserTypeCtxt
)
-import Type ( Type, ThetaType,
- mkTyVarTy, mkFunTy, mkAppTy, mkSynTy,
- mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys
+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,
+ liftedTypeKind, unliftedTypeKind, mkArrowKind,
+ mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe,
+ tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars,
+ tyVarsOfType, mkForAllTys
)
-import TyVar ( TyVar, mkTyVar )
-import PrelInfo ( cCallishClassKeys )
-import TyCon ( TyCon )
-import Name ( Name, OccName, isTvOcc, getOccName )
-import TysWiredIn ( mkListTy, mkTupleTy )
-import Unique ( Unique, Uniquable(..) )
-import Util ( zipWithEqual, zipLazy )
+import qualified Type ( getTyVar_maybe )
+
+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 ErrUtils ( Message )
+import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind )
+import Class ( classTyCon )
+import Name ( Name, getSrcLoc )
+import NameSet
+import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
+import BasicTypes ( Boxity(..) )
+import SrcLoc ( SrcLoc )
+import Util ( isSingleton, lengthIs )
import Outputable
+
\end{code}
-tcHsType and tcHsTypeKind
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+%************************************************************************
+%* *
+\subsection{Checking types}
+%* *
+%************************************************************************
-tcHsType checks that the type really is of kind Type!
+Generally speaking we now type-check types in three phases
-\begin{code}
-tcHsType :: RenamedHsType -> TcM s Type
+ 1. Kind check the HsType [kcHsType]
+ 2. Convert from HsType to Type, and hoist the foralls [tcHsType]
+ 3. Check the validity of the resulting type [checkValidType]
-tcHsType ty
- = tcAddErrCtxt (typeCtxt ty) $
- tc_hs_type ty
+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
-tc_hs_type ty
- = tc_hs_type_kind ty `thenTc` \ (kind,ty) ->
- -- Check that it really is a type
- unifyKind mkTypeKind kind `thenTc_`
- returnTc ty
+\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}
-tcHsTypeKind does the real work. It returns a kind and a type.
-\begin{code}
-tcHsTypeKind :: RenamedHsType -> TcM s (TcKind s, Type)
+%************************************************************************
+%* *
+\subsection{Kind checking}
+%* *
+%************************************************************************
-tcHsTypeKind ty
- = tcAddErrCtxt (typeCtxt ty) $
- tc_hs_type_kind ty
+Kind checking
+~~~~~~~~~~~~~
+When we come across the binding site for some type variables, we
+proceed in two stages
+1. Figure out what kind each tyvar has
- -- This equation isn't needed (the next one would handle it fine)
- -- but it's rather a common case, so we handle it directly
-tc_hs_type_kind (MonoTyVar name)
- | isTvOcc (getOccName name)
- = tcLookupTyVar name `thenNF_Tc` \ (kind,tyvar) ->
- returnTc (kind, mkTyVarTy tyvar)
+2. Create suitably-kinded tyvars,
+ extend the envt,
+ and typecheck the body
-tc_hs_type_kind ty@(MonoTyVar name)
- = tcFunType ty []
-
-tc_hs_type_kind (MonoListTy _ ty)
- = tc_hs_type ty `thenTc` \ tau_ty ->
- returnTc (mkBoxedTypeKind, mkListTy tau_ty)
-
-tc_hs_type_kind (MonoTupleTy _ tys)
- = mapTc tc_hs_type tys `thenTc` \ tau_tys ->
- returnTc (mkBoxedTypeKind, mkTupleTy (length tys) tau_tys)
-
-tc_hs_type_kind (MonoFunTy ty1 ty2)
- = tc_hs_type ty1 `thenTc` \ tau_ty1 ->
- tc_hs_type ty2 `thenTc` \ tau_ty2 ->
- returnTc (mkBoxedTypeKind, mkFunTy tau_ty1 tau_ty2)
-
-tc_hs_type_kind (MonoTyApp ty1 ty2)
- = tcTyApp ty1 [ty2]
-
-tc_hs_type_kind (HsForAllTy tv_names context ty)
- = tcTyVarScope tv_names $ \ tyvars ->
- tcContext context `thenTc` \ theta ->
- tc_hs_type ty `thenTc` \ tau ->
- -- For-all's are of kind type!
- returnTc (mkBoxedTypeKind, mkSigmaTy tyvars theta tau)
-
--- for unfoldings, and instance decls, only:
-tc_hs_type_kind (MonoDictTy class_name tys)
- = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tcLookupClass class_name `thenTc` \ (class_kinds, clas) ->
+To do step 1, we proceed thus:
+
+1a. Bind each type variable to a kind variable
+1b. Apply the kind checker
+1c. Zonk the resulting kinds
+
+The kind checker is passed to tcHsTyVars as an argument.
+
+For example, when we find
+ (forall a m. m a -> m a)
+we bind a,m to kind varibles and kind-check (m a -> m a). This
+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 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
+ * For a tyvar bound in a pattern type signature, its the types
+ mentioned in the other type signatures in that bunch of patterns
+ * For a tyvar bound in a RULE, it's the type signatures on other
+ universally quantified variables in the rule
+
+Note that this may occasionally give surprising results. For example:
+
+ data T a b = MkT (a b)
+
+Here we deduce a::*->*, b::*.
+But equally valid would be
+ a::(*->*)-> *, b::*->*
+
+\begin{code}
+-- 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!
+
+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 ->
let
- arity = length class_kinds
- n_args = length arg_kinds
- err = arityErr "Class" class_name arity n_args
+ tyvars = mkImmutTyVars tvs_w_kinds
in
- checkTc (arity == n_args) err `thenTc_`
- unifyKinds class_kinds arg_kinds `thenTc_`
- returnTc (mkBoxedTypeKind, mkDictTy clas arg_tys)
+ tcExtendTyVarEnv tyvars (thing_inside tyvars)
+
+
+
+tcAddScopedTyVars :: [RenamedHsType] -> TcM a -> TcM a
+-- tcAddScopedTyVars is used for scoped type variables
+-- added by pattern type signatures
+-- 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)
+
+-- Find the not-already-in-scope signature type variables,
+-- kind-check them, and bring them into scope
+--
+-- We no longer specify that these type variables must be univerally
+-- quantified (lots of email on the subject). If you want to put that
+-- back in, you need to
+-- a) Do a checkSigTyVars after thing_inside
+-- b) More insidiously, don't pass in expected_ty, else
+-- we unify with it too early and checkSigTyVars barfs
+-- Instead you have to pass in a fresh ty var, and unify
+-- it with expected_ty afterwards
+tcAddScopedTyVars [] thing_inside
+ = thing_inside -- Quick get-out for the empty case
+
+tcAddScopedTyVars sig_tys thing_inside
+ = tcGetEnv `thenNF_Tc` \ env ->
+ 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)
+ 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 ->
+ tcExtendTyVarEnv tyvars thing_inside
\end{code}
+
+
+\begin{code}
+kcHsTyVar :: HsTyVarBndr name -> NF_TcM (name, TcKind)
+kcHsTyVars :: [HsTyVarBndr name] -> NF_TcM [(name, TcKind)]
+
+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)
+
+---------------------------
+kcLiftedType :: RenamedHsType -> TcM ()
+ -- The type ty must be a *lifted* *type*
+kcLiftedType ty
+ = kcHsType ty `thenTc` \ kind ->
+ tcAddErrCtxt (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) $
+ unifyOpenTypeKind kind
+
+---------------------------
+kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM ()
+ -- Used for type signatures
+kcHsSigType = kcTypeType
+kcHsSigTypes tys = mapTc_ kcHsSigType tys
+kcHsLiftedSigType = kcLiftedType
+
+---------------------------
+kcHsType :: RenamedHsType -> TcM TcKind
+kcHsType (HsTyVar name) = kcTyVar name
+
+kcHsType (HsListTy ty)
+ = kcLiftedType ty `thenTc` \ tau_ty ->
+ returnTc liftedTypeKind
+
+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 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 liftedTypeKind
+
+kcHsType ty@(HsAppTy ty1 ty2)
+ = kcHsType ty1 `thenTc` \ tc_kind ->
+ kcHsType ty2 `thenTc` \ arg_kind ->
+ tcAddErrCtxt (appKindCtxt (ppr ty)) $
+ 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 fun_kind (mkArrowKind arg_kind res_kind) `thenTc_`
+ returnTc res_kind
+
+
+---------------------------
+kcHsContext ctxt = mapTc_ kcHsPred ctxt
+
+kcHsPred :: RenamedHsPred -> TcM ()
+kcHsPred pred@(HsIParam name ty)
+ = tcAddErrCtxt (appKindCtxt (ppr pred)) $
+ kcLiftedType ty
+
+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)
+
+ ---------------------------
+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{tc_type}
+%* *
+%************************************************************************
+
+tc_type, the main work horse
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ -------------------
+ *** BIG WARNING ***
+ -------------------
+
+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.
+
+ data T a = MkT a [T a]
+
+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 ***
+ --------------------------
+
-Help functions for type applications
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-tcTyApp (MonoTyApp ty1 ty2) tys
- = tcTyApp ty1 (ty2:tys)
+tc_type :: RenamedHsType -> TcM Type
+
+tc_type ty@(HsTyVar name)
+ = tc_app ty []
-tcTyApp ty tys
- | null tys
- = tcFunType ty []
+tc_type (HsListTy ty)
+ = tc_type ty `thenTc` \ tau_ty ->
+ returnTc (mkListTy tau_ty)
- | otherwise
- = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tcFunType ty arg_tys `thenTc` \ (fun_kind, result_ty) ->
+tc_type (HsTupleTy (HsTupCon _ boxity arity) tys)
+ = ASSERT( tys `lengthIs` arity )
+ tc_types tys `thenTc` \ tau_tys ->
+ returnTc (mkTupleTy boxity arity tau_tys)
- -- Check argument compatibility
- newKindVar `thenNF_Tc` \ result_kind ->
- unifyKind fun_kind (foldr mkArrowKind result_kind arg_kinds)
- `thenTc_`
- returnTc (result_kind, result_ty)
+tc_type (HsFunTy ty1 ty2)
+ = tc_type ty1 `thenTc` \ tau_ty1 ->
+ tc_type ty2 `thenTc` \ tau_ty2 ->
+ returnTc (mkFunTy tau_ty1 tau_ty2)
--- (tcFunType ty arg_tys) returns (kind-of ty, mkAppTys ty arg_tys)
+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]
+
+tc_type (HsAppTy ty1 ty2) = tc_app ty1 [ty2]
+
+tc_type (HsPredTy pred)
+ = tc_pred pred `thenTc` \ pred' ->
+ returnTc (mkPredTy pred')
+
+tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty)
+ = let
+ kind_check = kcHsContext ctxt `thenTc_` 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)
+
+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) $
+ 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)
+
+-- (tc_fun_type ty arg_tys) returns (mkAppTys ty arg_tys)
-- But not quite; for synonyms it checks the correct arity, and builds a SynTy
-- hence the rather strange functionality.
-tcFunType (MonoTyVar name) arg_tys
- | isTvOcc (getOccName name) -- Must be a type variable
- = tcLookupTyVar name `thenNF_Tc` \ (kind,tyvar) ->
- returnTc (kind, mkAppTys (mkTyVarTy tyvar) arg_tys)
-
- | otherwise -- Must be a type constructor
- = tcLookupTyCon name `thenTc` \ (tycon_kind,maybe_arity, tycon) ->
- case maybe_arity of
- Nothing -> -- Data type or newtype
- returnTc (tycon_kind, mkTyConApp tycon arg_tys)
-
- Just arity -> -- Type synonym
- checkTc (arity <= n_args) err_msg `thenTc_`
- returnTc (tycon_kind, result_ty)
- where
- -- It's OK to have an *over-applied* type synonym
- -- data Tree a b = ...
- -- type Foo a = Tree [a]
- -- f :: Foo a b -> ...
- result_ty = mkAppTys (mkSynTy tycon (take arity arg_tys))
- (drop arity arg_tys)
- err_msg = arityErr "Type synonym constructor" name arity n_args
- n_args = length arg_tys
-
-tcFunType ty arg_tys
- = tc_hs_type_kind ty `thenTc` \ (fun_kind, fun_ty) ->
- returnTc (fun_kind, mkAppTys fun_ty arg_tys)
+tc_fun_type name arg_tys
+ = tcLookup name `thenTc` \ thing ->
+ case thing of
+ ATyVar tv -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys)
+
+ AGlobal (ATyCon tc)
+ | isSynTyCon tc -> returnTc (mkSynTy tc arg_tys)
+ | otherwise -> returnTc (mkTyConApp tc arg_tys)
+
+ other -> failWithTc (wrongThingErr "type constructor" thing name)
\end{code}
Contexts
~~~~~~~~
\begin{code}
+tc_pred assn@(HsClassP class_name tys)
+ = tcAddErrCtxt (appKindCtxt (ppr assn)) $
+ tc_types tys `thenTc` \ arg_tys ->
+ tcLookupGlobal class_name `thenTc` \ thing ->
+ case thing of
+ AClass clas -> returnTc (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)
+\end{code}
-tcContext :: RenamedContext -> TcM s ThetaType
-tcContext context = tcAddErrCtxt (thetaCtxt context) $
- mapTc tcClassAssertion context
-
-tcClassAssertion (class_name, tys)
- = checkTc (canBeUsedInContext class_name)
- (naughtyCCallContextErr class_name) `thenTc_`
- tcLookupClass class_name `thenTc` \ (class_kinds, clas) ->
- mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (ty_kinds, tc_tys) ->
- unifyKinds class_kinds ty_kinds `thenTc_`
+%************************************************************************
+%* *
+\subsection{Type variables, with knot tying!}
+%* *
+%************************************************************************
- returnTc (clas, tc_tys)
+\begin{code}
+mkImmutTyVars :: [(Name,Kind)] -> [TyVar]
+mkImmutTyVars pairs = [mkTyVar name kind | (name, kind) <- pairs]
+
+mkTyClTyVars :: Kind -- Kind of the tycon or class
+ -> [HsTyVarBndr Name]
+ -> [TyVar]
+mkTyClTyVars kind tyvar_names
+ = mkImmutTyVars tyvars_w_kinds
+ where
+ (tyvars_w_kinds, _) = zipFunTys (hsTyVarNames tyvar_names) kind
\end{code}
-HACK warning: Someone discovered that @CCallable@ and @CReturnable@
-could be used in contexts such as:
-\begin{verbatim}
-foo :: CCallable a => a -> PrimIO Int
-\end{verbatim}
-Doing this utterly wrecks the whole point of introducing these
-classes so we specifically check that this isn't being done.
+%************************************************************************
+%* *
+\subsection{Signatures}
+%* *
+%************************************************************************
+
+@tcSigs@ checks the signatures for validity, and returns a list of
+{\em freshly-instantiated} signatures. That is, the types are already
+split up, and have fresh type variables installed. All non-type-signature
+"RenamedSigs" are ignored.
+
+The @TcSigInfo@ contains @TcTypes@ because they are unified with
+the variable's type, and after that checked to see whether they've
+been instantiated.
\begin{code}
-canBeUsedInContext :: Name -> Bool
-canBeUsedInContext n = not (uniqueOf n `elem` cCallishClassKeys)
+data TcSigInfo
+ = TySigInfo
+ Name -- N, the Name in corresponding binding
+
+ TcId -- *Polymorphic* binder for this value...
+ -- Has name = N
+
+ [TcTyVar] -- tyvars
+ TcThetaType -- theta
+ TcTauType -- tau
+
+ TcId -- *Monomorphic* binder for this value
+ -- Does *not* have name = N
+ -- Has type tau
+
+ [Inst] -- Empty if theta is null, or
+ -- (method mono_id) otherwise
+
+ 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
+
+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
\end{code}
-Type variables, with knot tying!
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
\begin{code}
-tcTyVarScope
- :: [HsTyVar Name] -- Names of some type variables
- -> ([TyVar] -> TcM s a) -- Thing to type check in their scope
- -> TcM s a -- Result
+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
+
+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
+ -- we could just split the sigma_tc_ty (since the tyvars don't
+ -- unified with anything). But in the case of an error, when
+ -- 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 ->
+ -- We make a Method even if it's not overloaded; no harm
+
+ returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc)
+ where
+ name = idName poly_id
+\end{code}
-tcTyVarScope tyvar_names thing_inside
- = mapAndUnzipNF_Tc tcHsTyVar tyvar_names `thenNF_Tc` \ (names, kinds) ->
- fixTc (\ ~(rec_tyvars, _) ->
- -- Ok to look at names, kinds, but not tyvars!
- tcExtendTyVarEnv names (kinds `zipLazy` rec_tyvars)
- (thing_inside rec_tyvars) `thenTc` \ result ->
-
- -- Get the tyvar's Kinds from their TcKinds
- mapNF_Tc tcDefaultKind kinds `thenNF_Tc` \ kinds' ->
+%************************************************************************
+%* *
+\subsection{Checking signature type variables}
+%* *
+%************************************************************************
- -- Construct the real TyVars
+@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
- tyvars = zipWithEqual "tcTyVarScope" mkTyVar names kinds'
+ (tidy_env', ftv') = tidyOpenTyVar tidy_env ftv
in
- returnTc (tyvars, result)
- ) `thenTc` \ (_,result) ->
- returnTc result
-
-tcHsTyVar (UserTyVar name)
- = newKindVar `thenNF_Tc` \ tc_kind ->
- returnNF_Tc (name, tc_kind)
-tcHsTyVar (IfaceTyVar name kind)
- = returnNF_Tc (name, kindToTcKind kind)
+ 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}
-Errors and contexts
-~~~~~~~~~~~~~~~~~~~
+These two context are used with checkSigTyVars
+
\begin{code}
-naughtyCCallContextErr clas_name
- = sep [ptext SLIT("Can't use class"), quotes (ppr clas_name), ptext SLIT("in a context")]
+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
+ ]
+ 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))])
+ 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
+\end{code}
-typeCtxt ty = ptext SLIT("In the type") <+> quotes (ppr ty)
-thetaCtxt theta = ptext SLIT("In the context") <+> quotes (pprContext theta)
+%************************************************************************
+%* *
+\subsection{Errors and contexts}
+%* *
+%************************************************************************
+
+\begin{code}
+typeKindCtxt :: RenamedHsType -> Message
+typeKindCtxt ty = sep [ptext SLIT("When checking that"),
+ nest 2 (quotes (ppr ty)),
+ ptext SLIT("is a type")]
+
+appKindCtxt :: SDoc -> Message
+appKindCtxt pp = ptext SLIT("When checking kinds in") <+> quotes pp
+
+wrongThingErr expected thing name
+ = pp_thing thing <+> quotes (ppr name) <+> ptext SLIT("used as a") <+> text expected
+ where
+ 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}
projects / ghc-hetmet.git / blobdiff