\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsTcType, tcHsTypeKind, tcContext,
- tcTyVarScope,
- TcSigInfo(..), tcTySig, mkTcSig, noSigs, maybeSig,
- checkSigTyVars, sigCtxt, existentialPatCtxt
+module TcMonoType ( tcHsSigType, tcHsType, tcIfaceType, tcHsTheta, tcHsPred,
+ UserTypeCtxt(..),
+
+ -- Kind checking
+ kcHsTyVar, kcHsTyVars, mkTyClTyVars,
+ kcHsType, kcHsSigType, kcHsSigTypes,
+ kcHsLiftedSigType, kcHsContext,
+ tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars,
+
+ TcSigInfo(..), tcTySig, mkTcSig, maybeSig, tcSigPolyId, tcSigMonoId
) where
#include "HsVersions.h"
-import HsSyn ( HsType(..), HsTyVar(..), Sig(..), pprContext )
-import RnHsSyn ( RenamedHsType, RenamedContext, RenamedSig )
-import TcHsSyn ( TcIdBndr, TcIdOcc(..) )
+import HsSyn ( HsType(..), HsTyVarBndr(..), HsTyOp(..),
+ Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames )
+import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars )
+import TcHsSyn ( TcId )
-import TcMonad
-import TcEnv ( tcLookupTyVar, tcLookupClass, tcLookupTyCon, tcExtendTyVarEnv,
- tcGetGlobalTyVars, tidyTypes, tidyTyVar
+import TcRnMonad
+import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
+ TyThing(..), TcTyThing(..), tcExtendKindEnv,
+ getInLocalScope
)
-import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType,
- typeToTcType, tcInstTcType, kindToTcKind,
- newKindVar,
- zonkTcKindToKind, zonkTcTyVars, zonkTcType
+import TcMType ( newMutTyVar, newKindVar, zonkKindEnv, tcInstType, zonkTcType,
+ checkValidType, UserTypeCtxt(..), pprUserTypeCtxt, newOpenTypeKind
)
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr )
-import TcUnify ( unifyKind, unifyKinds )
-import Type ( Type, ThetaType,
- mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
- mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys, splitRhoTy,
- boxedTypeKind, unboxedTypeKind, openTypeKind,
- mkArrowKind, getTyVar_maybe, getTyVar
+import TcUnify ( unifyKind, unifyOpenTypeKind, unifyFunKind )
+import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..),
+ TcTyVar, TcKind, TcThetaType, TcTauType,
+ mkTyVarTy, mkTyVarTys, mkFunTy, isTypeKind,
+ zipFunTys, mkForAllTys, mkFunTys, tcEqType, isPredTy,
+ mkSigmaTy, mkPredTy, mkGenTyConApp, mkTyConApp, mkAppTys,
+ liftedTypeKind, unliftedTypeKind, mkArrowKind, eqKind,
+ mkArrowKinds, tcSplitFunTy_maybe, tcSplitForAllTys
)
-import Id ( mkUserId, idName, idType, idFreeTyVars )
-import Var ( TyVar, mkTyVar )
-import VarEnv
-import VarSet
-import Bag ( bagToList )
-import PrelInfo ( cCallishClassKeys )
-import TyCon ( TyCon )
-import Name ( Name, OccName, isTvOcc, getOccName )
-import TysWiredIn ( mkListTy, mkTupleTy, mkUnboxedTupleTy )
+import qualified Type ( splitFunTys )
+import Inst ( Inst, InstOrigin(..), newMethod, instToId )
+
+import Id ( mkLocalId, idName, idType )
+import Var ( TyVar, mkTyVar, tyVarKind )
+import ErrUtils ( Message )
+import TyCon ( TyCon, tyConKind )
+import Class ( classTyCon )
+import Name ( Name )
+import NameSet
+import Subst ( deShadowTy )
+import TysWiredIn ( mkListTy, mkPArrTy, mkTupleTy, genUnitTyCon )
+import BasicTypes ( Boxity(..) )
import SrcLoc ( SrcLoc )
-import Unique ( Unique, Uniquable(..) )
-import Util ( zipWithEqual, zipLazy, mapAccumL )
+import Util ( lengthIs )
import Outputable
+import List ( nubBy )
\end{code}
%* *
%************************************************************************
-tcHsType and tcHsTypeKind
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+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 resulting type [checkValidType]
-tcHsType checks that the type really is of kind Type!
+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}
-tcHsType :: RenamedHsType -> TcM s Type
-tcHsType ty
- = tcAddErrCtxt (typeCtxt ty) $
- tc_hs_type ty
-
--- Version for when we need a TcType returned
-tcHsTcType :: RenamedHsType -> TcM s (TcType s)
-tcHsTcType ty
- = tcHsType ty `thenTc` \ ty' ->
- returnTc (typeToTcType ty')
-
-tc_hs_type ty
- = tc_hs_type_kind ty `thenTc` \ (kind,ty) ->
- -- Check that it really is a type
- unifyKind openTypeKind kind `thenTc_`
- returnTc ty
+tcHsSigType :: UserTypeCtxt -> RenamedHsType -> TcM Type
+ -- Do kind checking, and hoist for-alls to the top
+tcHsSigType ctxt ty = addErrCtxt (checkTypeCtxt ctxt ty) (
+ kcTypeType ty `thenM_`
+ tcHsType ty
+ ) `thenM` \ ty' ->
+ checkValidType ctxt ty' `thenM_`
+ returnM 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 `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 = mappM 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 (boxedTypeKind, mkListTy tau_ty)
-
-tc_hs_type_kind (MonoTupleTy tys True{-boxed-})
- = mapTc tc_hs_type tys `thenTc` \ tau_tys ->
- returnTc (boxedTypeKind, mkTupleTy (length tys) tau_tys)
-
-tc_hs_type_kind (MonoTupleTy tys False{-unboxed-})
- = mapTc tc_hs_type tys `thenTc` \ tau_tys ->
- returnTc (unboxedTypeKind, mkUnboxedTupleTy (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 (boxedTypeKind, 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 (boxedTypeKind, mkSigmaTy tyvars theta tau)
-
--- for unfoldings, and instance decls, only:
-tc_hs_type_kind (MonoDictTy class_name tys)
- = tcClassAssertion (class_name, tys) `thenTc` \ (clas, arg_tys) ->
- returnTc (boxedTypeKind, mkDictTy clas arg_tys)
+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 `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
+ 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
+ = getInLocalScope `thenM` \ in_scope ->
+ let
+ all_sig_tvs = foldr (unionNameSets . extractHsTyVars) emptyNameSet sig_tys
+ sig_tvs = filter (not . in_scope) (nameSetToList all_sig_tvs)
+ in
+ 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}
+
-Help functions for type applications
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-tcTyApp (MonoTyApp ty1 ty2) tys
- = tcTyApp ty1 (ty2:tys)
+kcHsTyVar :: HsTyVarBndr name -> TcM (name, TcKind)
+kcHsTyVars :: [HsTyVarBndr name] -> TcM [(name, TcKind)]
-tcTyApp ty tys
- | null tys
- = tcFunType ty []
+kcHsTyVar (UserTyVar name) = newNamedKindVar name
+kcHsTyVar (IfaceTyVar name kind) = returnM (name, kind)
- | otherwise
- = mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tcFunType ty arg_tys `thenTc` \ (fun_kind, result_ty) ->
+kcHsTyVars tvs = mappM kcHsTyVar tvs
- -- Check argument compatibility
- newKindVar `thenNF_Tc` \ result_kind ->
- unifyKind fun_kind (foldr mkArrowKind result_kind arg_kinds)
- `thenTc_`
- returnTc (result_kind, result_ty)
+newNamedKindVar name = newKindVar `thenM` \ kind ->
+ returnM (name, kind)
--- (tcFunType ty arg_tys) returns (kind-of ty, mkAppTys ty arg_tys)
--- But not quite; for synonyms it checks the correct arity, and builds a SynTy
--- hence the rather strange functionality.
+---------------------------
+kcLiftedType :: RenamedHsType -> TcM Kind
+ -- The type ty must be a *lifted* *type*
+kcLiftedType ty = kcHsType ty `thenM` \ act_kind ->
+ checkExpectedKind (ppr ty) act_kind liftedTypeKind
+
+---------------------------
+kcTypeType :: RenamedHsType -> TcM ()
+ -- The type ty must be a *type*, but it can be lifted or unlifted.
+kcTypeType ty
+ = kcHsType ty `thenM` \ kind ->
+ if isTypeKind kind then
+ return ()
+ else
+ newOpenTypeKind `thenM` \ exp_kind ->
+ checkExpectedKind (ppr ty) kind exp_kind `thenM_`
+ returnM ()
+
+---------------------------
+kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM ()
+ -- Used for type signatures
+kcHsSigType ty = kcTypeType ty
+kcHsSigTypes tys = mappM_ kcHsSigType tys
+kcHsLiftedSigType ty = kcLiftedType ty `thenM_` returnM ()
+
+---------------------------
+kcHsType :: RenamedHsType -> TcM TcKind
+-- kcHsType *returns* the kind of the type, rather than taking an expected
+-- kind as argument as tcExpr does. Reason: the kind of (->) is
+-- forall bx1 bx2. Type bx1 -> Type bx2 -> Type Boxed
+-- so we'd need to generate huge numbers of bx variables.
+
+kcHsType (HsTyVar name) = kcTyVar name
+kcHsType (HsListTy ty) = kcLiftedType ty
+kcHsType (HsPArrTy ty) = kcLiftedType ty
+kcHsType (HsParTy ty) = kcHsType ty -- Skip parentheses markers
+kcHsType (HsNumTy _) = returnM liftedTypeKind -- The unit type for generics
+kcHsType (HsKindSig ty k) = kcHsType ty `thenM` \ act_kind ->
+ checkExpectedKind (ppr ty) act_kind k
+
+kcHsType (HsTupleTy (HsTupCon boxity _) tys)
+ = mappM kcTypeType tys `thenM_`
+ returnM (case boxity of
+ Boxed -> liftedTypeKind
+ Unboxed -> unliftedTypeKind)
+
+kcHsType (HsFunTy ty1 ty2)
+ = 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 op_ty@(HsTyOp op) ty2)
+ = addErrCtxt (appKindCtxt (ppr ty)) $
+ kcTyVar op `thenM` \ op_kind ->
+ kcApps (ppr op_ty) op_kind [ty1,ty2]
+
+kcHsType (HsPredTy pred)
+ = kcHsPred pred `thenM_`
+ returnM liftedTypeKind
+
+kcHsType ty@(HsAppTy ty1 ty2)
+ = addErrCtxt (appKindCtxt (ppr ty)) $
+ kc_app ty []
+ where
+ kc_app (HsAppTy f a) as = kc_app f (a:as)
+ kc_app f as = kcHsType f `thenM` \ fk ->
+ kcApps (ppr f) fk as
+
+kcHsType (HsForAllTy (Just tv_names) context ty)
+ = kcHsTyVars tv_names `thenM` \ kind_env ->
+ tcExtendKindEnv kind_env $
+ kcHsContext context `thenM_`
+ kcLiftedType ty
+ -- 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.
+
+---------------------------
+kcApps :: SDoc -- The function
+ -> TcKind -- Function kind
+ -> [RenamedHsType] -- Arg types
+ -> TcM TcKind -- Result kind
+kcApps pp_fun fun_kind args
+ = go fun_kind args
+ where
+ go fk [] = returnM fk
+ go fk (ty:tys) = unifyFunKind fk `thenM` \ mb_fk ->
+ case mb_fk of {
+ Nothing -> failWithTc too_few_args ;
+ Just (ak',fk') ->
+ kcHsType ty `thenM` \ ak ->
+ checkExpectedKind (ppr ty) ak ak' `thenM_`
+ go fk' tys }
+
+ too_few_args = ptext SLIT("Kind error:") <+> quotes pp_fun <+>
+ ptext SLIT("is applied to too many type arguments")
+
+---------------------------
+-- We would like to get a decent error message from
+-- (a) Under-applied type constructors
+-- f :: (Maybe, Maybe)
+-- (b) Over-applied type constructors
+-- f :: Int x -> Int x
+--
+
+checkExpectedKind :: SDoc -> TcKind -> TcKind -> TcM TcKind
+-- A fancy wrapper for 'unifyKind', which tries to give
+-- decent error messages.
+-- Returns the same kind that it is passed, exp_kind
+checkExpectedKind pp_ty act_kind exp_kind
+ | act_kind `eqKind` exp_kind -- Short cut for a very common case
+ = returnM exp_kind
+ | otherwise
+ = tryTc (unifyKind exp_kind act_kind) `thenM` \ (errs, mb_r) ->
+ case mb_r of {
+ Just _ -> returnM exp_kind ; -- Unification succeeded
+ Nothing ->
+
+ -- So there's definitely an error
+ -- Now to find out what sort
+ zonkTcType exp_kind `thenM` \ exp_kind ->
+ zonkTcType act_kind `thenM` \ act_kind ->
+
+ let (exp_as, _) = Type.splitFunTys exp_kind
+ (act_as, _) = Type.splitFunTys act_kind
+ -- Use the Type versions for kinds
+ n_exp_as = length exp_as
+ n_act_as = length act_as
+
+ err | n_exp_as < n_act_as -- E.g. [Maybe]
+ = quotes pp_ty <+> ptext SLIT("is not applied to enough type arguments")
+
+ -- Now n_exp_as >= n_act_as. In the next two cases,
+ -- n_exp_as == 0, and hence so is n_act_as
+ | exp_kind `eqKind` liftedTypeKind && act_kind `eqKind` unliftedTypeKind
+ = ptext SLIT("Expecting a lifted type, but") <+> quotes pp_ty
+ <+> ptext SLIT("is unlifted")
+
+ | exp_kind `eqKind` unliftedTypeKind && act_kind `eqKind` liftedTypeKind
+ = ptext SLIT("Expecting an unlifted type, but") <+> quotes pp_ty
+ <+> ptext SLIT("is lifted")
+
+ | otherwise -- E.g. Monad [Int]
+ = sep [ ptext SLIT("Expecting kind") <+> quotes (ppr exp_kind) <> comma,
+ ptext SLIT("but") <+> quotes pp_ty <+>
+ ptext SLIT("has kind") <+> quotes (ppr act_kind)]
+ in
+ failWithTc (ptext SLIT("Kind error:") <+> err)
+ }
+
+---------------------------
+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 ->
+ kcApps (ppr cls) kind tys
+
+---------------------------
+kcHsContext ctxt = mappM_ kcHsPred ctxt
+
+kcHsPred pred -- Checks that the result is of kind liftedType
+ = addErrCtxt (appKindCtxt (ppr pred)) $
+ kc_pred pred `thenM` \ kind ->
+ checkExpectedKind (ppr pred) kind liftedTypeKind
+
-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)
+ ---------------------------
+kcTyVar name -- Could be a tyvar or a tycon
+ = tcLookup name `thenM` \ thing ->
+ case thing of
+ 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 `thenM` \ thing ->
+ case thing of
+ AThing kind -> returnM kind
+ AGlobal (AClass cls) -> returnM (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 ***
+ --------------------------
+
-Contexts
-~~~~~~~~
\begin{code}
+tc_type :: RenamedHsType -> TcM Type
-tcContext :: RenamedContext -> TcM s ThetaType
-tcContext context
- = tcAddErrCtxt (thetaCtxt context) $
+tc_type ty@(HsTyVar name)
+ = tc_app ty []
- --Someone discovered that @CCallable@ and @CReturnable@
- -- could be used in contexts such as:
- -- foo :: CCallable a => a -> PrimIO Int
- -- Doing this utterly wrecks the whole point of introducing these
- -- classes so we specifically check that this isn't being done.
- --
- -- We *don't* do this check in tcClassAssertion, because that's
- -- called when checking a HsDictTy, and we don't want to reject
- -- instance CCallable Int
- -- etc. Ugh!
- mapTc check_naughty context `thenTc_`
+tc_type (HsKindSig ty k)
+ = tc_type ty -- Kind checking done already
- mapTc tcClassAssertion context
+tc_type (HsListTy ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkListTy tau_ty)
- where
- check_naughty (class_name, _)
- = checkTc (not (getUnique class_name `elem` cCallishClassKeys))
- (naughtyCCallContextErr class_name)
+tc_type (HsPArrTy ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkPArrTy tau_ty)
-tcClassAssertion (class_name, tys)
- = tcLookupClass class_name `thenTc` \ (class_kinds, clas) ->
- mapAndUnzipTc tc_hs_type_kind tys `thenTc` \ (ty_kinds, tc_tys) ->
+tc_type (HsTupleTy (HsTupCon boxity arity) tys)
+ = ASSERT( tys `lengthIs` arity )
+ tc_types tys `thenM` \ tau_tys ->
+ returnM (mkTupleTy boxity arity tau_tys)
- -- Check with kind mis-match
- let
- arity = length class_kinds
- n_tys = length ty_kinds
- err = arityErr "Class" class_name arity n_tys
+tc_type (HsFunTy ty1 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)
+ returnM (mkTyConApp genUnitTyCon [])
+
+tc_type ty@(HsAppTy ty1 ty2)
+ = addErrCtxt (appKindCtxt (ppr ty)) $
+ tc_app ty1 [ty2]
+
+tc_type (HsPredTy pred)
+ = tc_pred pred `thenM` \ pred' ->
+ returnM (mkPredTy pred')
+
+tc_type full_ty@(HsForAllTy (Just tv_names) ctxt ty)
+ = let
+ kind_check = kcHsContext ctxt `thenM_` kcHsType ty
in
- checkTc (arity == n_tys) err `thenTc_`
- unifyKinds class_kinds ty_kinds `thenTc_`
+ tcHsTyVars tv_names kind_check $ \ tyvars ->
+ mappM tc_pred ctxt `thenM` \ theta ->
+ tc_type ty `thenM` \ tau ->
+ returnM (mkSigmaTy tyvars theta tau)
+
+tc_types arg_tys = mappM tc_type arg_tys
+\end{code}
- returnTc (clas, tc_tys)
+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
+ = tc_types tys `thenM` \ arg_tys ->
+ case ty of
+ HsTyVar fun -> tc_fun_type fun arg_tys
+ other -> tc_type ty `thenM` \ fun_ty ->
+ returnM (mkAppTys fun_ty arg_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.
+
+tc_fun_type name arg_tys
+ = tcLookup name `thenM` \ thing ->
+ case thing of
+ ATyVar tv -> returnM (mkAppTys (mkTyVarTy tv) 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)
+ = addErrCtxt (appKindCtxt (ppr assn)) $
+ tc_types tys `thenM` \ arg_tys ->
+ tcLookupGlobal class_name `thenM` \ thing ->
+ case thing of
+ AClass clas -> returnM (ClassP clas arg_tys)
+ other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name)
+
+tc_pred assn@(HsIParam name ty)
+ = addErrCtxt (appKindCtxt (ppr assn)) $
+ tc_type ty `thenM` \ arg_ty ->
+ returnM (IParam name arg_ty)
\end{code}
+
%************************************************************************
%* *
\subsection{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
-
-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 zonkTcKindToKind kinds `thenNF_Tc` \ kinds' ->
-
- -- Construct the real TyVars
- let
- tyvars = zipWithEqual "tcTyVarScope" mkTyVar names kinds'
- 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)
+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}
been instantiated.
\begin{code}
-data TcSigInfo s
+data TcSigInfo
= TySigInfo
- Name -- N, the Name in corresponding binding
-
- (TcIdBndr s) -- *Polymorphic* binder for this value...
+ TcId -- *Polymorphic* binder for this value...
-- Has name = N
- [TcTyVar s] -- tyvars
- (TcThetaType s) -- theta
- (TcTauType s) -- tau
+ [TcTyVar] -- tyvars
+ TcThetaType -- theta
+ TcTauType -- tau
- (TcIdBndr s) -- *Monomorphic* binder for this value
+ TcId -- *Monomorphic* binder for this value
-- Does *not* have name = N
-- Has type tau
- (Inst s) -- Empty if theta is null, or
+ [Inst] -- Empty if theta is null, or
-- (method mono_id) otherwise
SrcLoc -- Of the signature
+instance Outputable TcSigInfo where
+ 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
-maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s)
+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
-
--- This little helper is useful to pass to tcPat
-noSigs :: Name -> Maybe (TcIdBndr s)
-noSigs name = Nothing
+maybeSig (sig@(TySigInfo sig_id _ _ _ _ _ _) : sigs) name
+ | name == idName sig_id = Just sig
+ | otherwise = maybeSig sigs name
\end{code}
\begin{code}
-tcTySig :: RenamedSig
- -> TcM s (TcSigInfo s)
+tcTySig :: RenamedSig -> TcM TcSigInfo
tcTySig (Sig v ty src_loc)
- = tcAddSrcLoc src_loc $
- tcHsTcType ty `thenTc` \ sigma_tc_ty ->
- mkTcSig (mkUserId 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 :: TcIdBndr s -> SrcLoc -> NF_TcM s (TcSigInfo s)
+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
- tcInstTcType (idType poly_id) `thenNF_Tc` \ (tyvars, rho) ->
- let
- (theta, tau) = splitRhoTy rho
- -- This splitSigmaTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- newMethodWithGivenTy SignatureOrigin
- (TcId poly_id)
- (mkTyVarTys tyvars)
- theta tau `thenNF_Tc` \ inst ->
+ tcInstType SigTv (idType poly_id) `thenM` \ (tyvars', theta', tau') ->
+
+ getInstLoc SignatureOrigin `thenM` \ inst_loc ->
+ newMethod 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 (instToIdBndr 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.
-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 s] -- The original signature type variables
- -> TcM s [TcTyVar s] -- Zonked signature type variables
-
-checkSigTyVars [] = returnTc []
-
-checkSigTyVars sig_tyvars
- = zonkTcTyVars sig_tyvars `thenNF_Tc` \ sig_tys ->
- tcGetGlobalTyVars `thenNF_Tc` \ globals ->
- checkTcM (all_ok sig_tys globals)
- (complain sig_tys globals) `thenTc_`
-
- returnTc (map (getTyVar "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
- = failWithTcM (env2, main_msg)
- where
- (env1, tidy_tys) = tidyTypes emptyTidyEnv sig_tys
- (env2, tidy_tvs) = mapAccumL tidyTyVar env1 sig_tyvars
-
- msgs = check (tidy_tvs `zip` tidy_tys) emptyVarEnv
-
- main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
- $$
- nest 4 (vcat msgs)
-
- check [] acc = []
- check ((sig_tyvar,ty):prs) acc
- = case getTyVar_maybe ty of
- Nothing -- Error (a)!
- -> unify_msg sig_tyvar (ppr ty) : check prs acc
-
- Just tv
- | tv `elemVarSet` globals -- Error (c)! Type variable escapes
- -> escape_msg tv : check prs acc
-
- | otherwise
- -> case lookupVarEnv acc tv of
- Nothing -- All OK
- -> check prs (extendVarEnv acc tv sig_tyvar) -- All OK
- Just sig_tyvar' -- Error (b)!
- -> unify_msg sig_tyvar (ppr sig_tyvar') : check prs acc
-
-
-escape_msg tv = mk_msg tv <+> ptext SLIT("escapes; i.e. unifies with something more global")
-unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> quotes thing
-mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv)
-\end{code}
-
-These two context are used with checkSigTyVars
-
\begin{code}
-sigCtxt thing sig_tau tidy_env
- = zonkTcType sig_tau `thenNF_Tc` \ zonked_sig_tau ->
- let
- (env1, [tidy_tau, tidy_zonked_tau]) = tidyTypes tidy_env [sig_tau, zonked_sig_tau]
-
- msg = vcat [ptext SLIT("When checking the type signature for") <+> thing,
- nest 4 (ptext SLIT("Signature:") <+> ppr tidy_tau),
- nest 4 (ptext SLIT("Inferred: ") <+> ppr tidy_zonked_tau)]
+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
+
+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 (env1, msg)
-
-existentialPatCtxt bound_tvs bound_ids tidy_env
- = returnNF_Tc (env1,
- sep [ptext SLIT("When checking an existential 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
- tv_list = bagToList bound_tvs
- show_ids = filter is_interesting (map snd (bagToList bound_ids))
- is_interesting id = any (`elemVarSet` idFreeTyVars id) tv_list
-
- (env1, tidy_tys) = tidyTypes tidy_env (map idType show_ids)
- ppr_id id ty = ppr id <+> ptext SLIT("::") <+> 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}
%************************************************************************
\begin{code}
-naughtyCCallContextErr clas_name
- = sep [ptext SLIT("Can't use class"), quotes (ppr clas_name), ptext SLIT("in a context")]
+typeKindCtxt :: RenamedHsType -> Message
+typeKindCtxt ty = sep [ptext SLIT("When checking that"),
+ nest 2 (quotes (ppr ty)),
+ ptext SLIT("is a type")]
-typeCtxt ty = ptext SLIT("In the type") <+> quotes (ppr ty)
+appKindCtxt :: SDoc -> Message
+appKindCtxt pp = ptext SLIT("When checking kinds in") <+> quotes pp
-thetaCtxt theta = ptext SLIT("In the context") <+> quotes (pprContext theta)
+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