\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsTypeKind, tcHsTopType, tcHsTopBoxedType, tcHsTopTypeKind,
- tcContext, tcHsTyVar, kcHsTyVar,
- tcExtendTyVarScope, tcExtendTopTyVarScope,
- TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
- checkSigTyVars, sigCtxt, sigPatCtxt
+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(..), MonoUsageAnn(..),
- Sig(..), HsPred(..), pprHsPred, pprParendHsType )
-import RnHsSyn ( RenamedHsType, RenamedContext, RenamedSig )
+import HsSyn ( HsType(..), HsTyVarBndr(..), HsTyOp(..),
+ Sig(..), HsPred(..), HsTupCon(..), hsTyVarNames )
+import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig, extractHsTyVars )
import TcHsSyn ( TcId )
-import TcMonad
-import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars,
- tcExtendUVarEnv, tcLookupUVar,
- tcGetGlobalTyVars, valueEnvIds, TcTyThing(..)
+import TcRnMonad
+import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
+ TyThing(..), TcTyThing(..), tcExtendKindEnv,
+ getInLocalScope
)
-import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType,
- typeToTcType, kindToTcKind,
- newKindVar, tcInstSigVar,
- zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType
+import TcMType ( newMutTyVar, newKindVar, zonkKindEnv, tcInstType, zonkTcType,
+ checkValidType, UserTypeCtxt(..), pprUserTypeCtxt, newOpenTypeKind
)
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr )
-import TcUnify ( unifyKind, unifyKinds, unifyTypeKind )
-import Type ( Type, PredType(..), ThetaType, UsageAnn(..),
- mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, mkUsgTy,
- mkUsForAllTy, zipFunTys,
- mkSigmaTy, mkDictTy, mkTyConApp, mkAppTys, splitForAllTys, splitRhoTy,
- boxedTypeKind, unboxedTypeKind, tyVarsOfType,
- mkArrowKinds, getTyVar_maybe, getTyVar,
- tidyOpenType, tidyOpenTypes, tidyTyVar,
- tyVarsOfType, tyVarsOfTypes
+import TcUnify ( unifyKind, 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, eqKind,
+ tcSplitFunTy_maybe, tcSplitForAllTys
)
-import PprType ( pprConstraint )
-import Subst ( mkTopTyVarSubst, substTy )
-import Id ( mkVanillaId, idName, idType, idFreeTyVars )
-import Var ( TyVar, mkTyVar, mkNamedUVar, varName )
-import VarEnv
-import VarSet
-import Bag ( bagToList )
+import qualified Type ( splitFunTys )
+import Inst ( Inst, InstOrigin(..), newMethod, instToId )
+
+import Id ( mkLocalId, idName, idType )
+import Var ( TyVar, mkTyVar, tyVarKind )
import ErrUtils ( Message )
-import PrelInfo ( cCallishClassKeys )
-import TyCon ( TyCon )
-import Name ( Name, OccName, isLocallyDefined )
-import TysWiredIn ( mkListTy, mkTupleTy, mkUnboxedTupleTy )
-import UniqFM ( elemUFM, foldUFM )
+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 TcType
-tcHsType ty
- = -- tcAddErrCtxt (typeCtxt ty) $
- tc_type ty
-
-tcHsTypeKind :: RenamedHsType -> TcM s (TcKind, TcType)
-tcHsTypeKind ty
- = -- tcAddErrCtxt (typeCtxt ty) $
- tc_type_kind ty
-
--- Type-check a type, *and* then lazily zonk it. The important
--- point is that this zonks all the uncommitted *kind* variables
--- in kinds of any any nested for-all tyvars.
--- There won't be any mutable *type* variables at all.
---
--- NOTE the forkNF_Tc. This makes the zonking lazy, which is
--- absolutely necessary. During the type-checking of a recursive
--- group of tycons/classes (TcTyClsDecls.tcGroup) we use an
--- environment in which we aren't allowed to look at the actual
--- tycons/classes returned from a lookup. Because tc_app does
--- look at the tycon to build the type, we can't look at the type
--- either, until we get out of the loop. The fork delays the
--- zonking till we've completed the loop. Sigh.
-
-tcHsTopType :: RenamedHsType -> TcM s Type
-tcHsTopType ty
- = -- tcAddErrCtxt (typeCtxt ty) $
- tc_type ty `thenTc` \ ty' ->
- forkNF_Tc (zonkTcTypeToType ty')
-
-tcHsTopTypeKind :: RenamedHsType -> TcM s (TcKind, Type)
-tcHsTopTypeKind ty
- = -- tcAddErrCtxt (typeCtxt ty) $
- tc_type_kind ty `thenTc` \ (kind, ty') ->
- forkNF_Tc (zonkTcTypeToType ty') `thenTc` \ zonked_ty ->
- returnNF_Tc (kind, zonked_ty)
-
-tcHsTopBoxedType :: RenamedHsType -> TcM s Type
-tcHsTopBoxedType ty
- = -- tcAddErrCtxt (typeCtxt ty) $
- tc_boxed_type ty `thenTc` \ ty' ->
- forkNF_Tc (zonkTcTypeToType 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}
-The main work horse
-~~~~~~~~~~~~~~~~~~~
+%************************************************************************
+%* *
+\subsection{Kind checking}
+%* *
+%************************************************************************
+
+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
+
+2. Create suitably-kinded tyvars,
+ extend the envt,
+ and typecheck the body
+
+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}
-tc_boxed_type :: RenamedHsType -> TcM s Type
-tc_boxed_type ty
- = tc_type_kind ty `thenTc` \ (actual_kind, tc_ty) ->
- tcAddErrCtxt (typeKindCtxt ty)
- (unifyKind boxedTypeKind actual_kind) `thenTc_`
- returnTc tc_ty
-
-tc_type :: RenamedHsType -> TcM s Type
-tc_type ty
- -- The type ty must be a *type*, but it can be boxed
- -- or unboxed. So we check that is is of form (Type bv)
- -- using unifyTypeKind
- = tc_type_kind ty `thenTc` \ (actual_kind, tc_ty) ->
- tcAddErrCtxt (typeKindCtxt ty)
- (unifyTypeKind actual_kind) `thenTc_`
- returnTc tc_ty
-
-tc_type_kind :: RenamedHsType -> TcM s (TcKind, Type)
-tc_type_kind ty@(MonoTyVar name)
- = tc_app ty []
+-- 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}
-tc_type_kind (MonoListTy ty)
- = tc_boxed_type ty `thenTc` \ tau_ty ->
- returnTc (boxedTypeKind, mkListTy tau_ty)
-
-tc_type_kind (MonoTupleTy tys True {-boxed-})
- = mapTc tc_boxed_type tys `thenTc` \ tau_tys ->
- returnTc (boxedTypeKind, mkTupleTy (length tys) tau_tys)
-
-tc_type_kind (MonoTupleTy tys False {-unboxed-})
- = mapTc tc_type tys `thenTc` \ tau_tys ->
- returnTc (unboxedTypeKind, mkUnboxedTupleTy (length tys) tau_tys)
-
-tc_type_kind (MonoFunTy ty1 ty2)
- = tc_type ty1 `thenTc` \ tau_ty1 ->
- tc_type ty2 `thenTc` \ tau_ty2 ->
- returnTc (boxedTypeKind, mkFunTy tau_ty1 tau_ty2)
-
-tc_type_kind (MonoTyApp ty1 ty2)
- = tc_app ty1 [ty2]
-
-tc_type_kind (MonoDictTy class_name tys)
- = tcClassAssertion (HsPClass class_name tys) `thenTc` \ (Class clas arg_tys) ->
- returnTc (boxedTypeKind, mkDictTy clas arg_tys)
-
-tc_type_kind (MonoUsgTy usg ty)
- = newUsg usg `thenTc` \ usg' ->
- tc_type_kind ty `thenTc` \ (kind, tc_ty) ->
- returnTc (kind, mkUsgTy usg' tc_ty)
+
+\begin{code}
+kcHsTyVar :: HsTyVarBndr name -> TcM (name, TcKind)
+kcHsTyVars :: [HsTyVarBndr name] -> TcM [(name, TcKind)]
+
+kcHsTyVar (UserTyVar name) = newNamedKindVar name
+kcHsTyVar (IfaceTyVar name kind) = returnM (name, kind)
+
+kcHsTyVars tvs = mappM kcHsTyVar tvs
+
+newNamedKindVar name = newKindVar `thenM` \ kind ->
+ returnM (name, kind)
+
+---------------------------
+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
- newUsg usg = case usg of
- MonoUsOnce -> returnTc UsOnce
- MonoUsMany -> returnTc UsMany
- MonoUsVar uv_name -> tcLookupUVar uv_name `thenTc` \ uv ->
- returnTc (UsVar uv)
+ 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
+
+
+ ---------------------------
+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 ***
+ --------------------------
+
+
+\begin{code}
+tc_type :: RenamedHsType -> TcM Type
+
+tc_type ty@(HsTyVar name)
+ = tc_app ty []
+
+tc_type (HsKindSig ty k)
+ = tc_type ty -- Kind checking done already
+
+tc_type (HsListTy ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkListTy tau_ty)
+
+tc_type (HsPArrTy ty)
+ = tc_type ty `thenM` \ tau_ty ->
+ returnM (mkPArrTy tau_ty)
+
+tc_type (HsTupleTy (HsTupCon boxity arity) tys)
+ = ASSERT( tys `lengthIs` arity )
+ tc_types tys `thenM` \ tau_tys ->
+ returnM (mkTupleTy boxity arity tau_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_kind (MonoUsgForAllTy uv_name ty)
+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
- uv = mkNamedUVar uv_name
- in
- tcExtendUVarEnv uv_name uv $
- tc_type_kind ty `thenTc` \ (kind, tc_ty) ->
- returnTc (kind, mkUsForAllTy uv tc_ty)
-
-tc_type_kind (HsForAllTy (Just tv_names) context ty)
- = tcExtendTyVarScope tv_names $ \ tyvars ->
- tcContext context `thenTc` \ theta ->
- tc_type_kind ty `thenTc` \ (kind, tau) ->
- tcGetInScopeTyVars `thenTc` \ in_scope_vars ->
- let
- body_kind | null theta = kind
- | otherwise = boxedTypeKind
- -- 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
- check ct@(Class c tys) | ambiguous = failWithTc (ambigErr (c,tys) tau)
- | otherwise = returnTc ()
- where ct_vars = tyVarsOfTypes tys
- forall_tyvars = map varName in_scope_vars
- tau_vars = tyVarsOfType tau
- ambig ct_var = (varName ct_var `elem` forall_tyvars) &&
- not (ct_var `elemUFM` tau_vars)
- ambiguous = foldUFM ((||) . ambig) False ct_vars
+ kind_check = kcHsContext ctxt `thenM_` kcHsType ty
in
- mapTc check theta `thenTc_`
- returnTc (body_kind, mkSigmaTy tyvars theta tau)
+ 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}
Help functions for type applications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-tc_app (MonoTyApp ty1 ty2) tys
+tc_app :: RenamedHsType -> [RenamedHsType] -> TcM Type
+tc_app (HsAppTy ty1 ty2) tys
= tc_app ty1 (ty2:tys)
tc_app ty tys
- | null tys
- = tc_fun_type ty []
+ = 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)
- | otherwise
- = tcAddErrCtxt (appKindCtxt pp_app) $
- mapAndUnzipTc tc_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tc_fun_type ty arg_tys `thenTc` \ (fun_kind, result_ty) ->
-
- -- Check argument compatibility
- newKindVar `thenNF_Tc` \ result_kind ->
- unifyKind fun_kind (mkArrowKinds arg_kinds result_kind)
- `thenTc_`
- returnTc (result_kind, result_ty)
- where
- pp_app = ppr ty <+> sep (map pprParendHsType tys)
-
--- (tc_fun_type ty arg_tys) returns (kind-of ty, mkAppTys 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 (MonoTyVar name) arg_tys
- = tcLookupTy name `thenTc` \ (tycon_kind, maybe_arity, thing) ->
+tc_fun_type name arg_tys
+ = tcLookup name `thenM` \ thing ->
case thing of
- ATyVar tv -> returnTc (tycon_kind, mkAppTys (mkTyVarTy tv) arg_tys)
- AClass clas -> failWithTc (classAsTyConErr name)
- ATyCon tc -> case maybe_arity of
- Nothing -> -- Data or newtype
- returnTc (tycon_kind, mkTyConApp tc 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 tc (take arity arg_tys))
- (drop arity arg_tys)
- err_msg = arityErr "type synonym" name arity n_args
- n_args = length arg_tys
-
-tc_fun_type ty arg_tys
- = tc_type_kind ty `thenTc` \ (fun_kind, fun_ty) ->
- returnTc (fun_kind, mkAppTys fun_ty arg_tys)
+ 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}
-
-tcContext :: RenamedContext -> TcM s ThetaType
-tcContext context
- = --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_`
-
- mapTc tcClassAssertion context
-
- where
- check_naughty (HsPClass class_name _)
- = checkTc (not (getUnique class_name `elem` cCallishClassKeys))
- (naughtyCCallContextErr class_name)
- check_naughty (HsPIParam _ _) = returnTc ()
-
-tcClassAssertion assn@(HsPClass class_name tys)
- = tcAddErrCtxt (appKindCtxt (pprHsPred assn)) $
- mapAndUnzipTc tc_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tcLookupTy class_name `thenTc` \ (kind, ~(Just arity), thing) ->
+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
- ATyVar _ -> failWithTc (tyVarAsClassErr class_name)
- ATyCon _ -> failWithTc (tyConAsClassErr class_name)
- AClass clas ->
- -- Check with kind mis-match
- checkTc (arity == n_tys) err `thenTc_`
- unifyKind kind (mkArrowKinds arg_kinds boxedTypeKind) `thenTc_`
- returnTc (Class clas arg_tys)
- where
- n_tys = length tys
- err = arityErr "Class" class_name arity n_tys
-tcClassAssertion assn@(HsPIParam name ty)
- = tcAddErrCtxt (appKindCtxt (pprHsPred assn)) $
- tc_type_kind ty `thenTc` \ (arg_kind, arg_ty) ->
- returnTc (IParam name arg_ty)
+ 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}
-tcExtendTopTyVarScope :: TcKind -> [HsTyVar Name]
- -> ([TcTyVar] -> TcKind -> TcM s a)
- -> TcM s a
-tcExtendTopTyVarScope kind tyvar_names thing_inside
- = let
- (tyvars_w_kinds, result_kind) = zipFunTys tyvar_names kind
- tyvars = map mk_tv tyvars_w_kinds
- in
- tcExtendTyVarEnv tyvars (thing_inside tyvars result_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
- mk_tv (UserTyVar name, kind) = mkTyVar name kind
- mk_tv (IfaceTyVar name _, kind) = mkTyVar name kind
- -- NB: immutable tyvars, but perhaps with mutable kinds
-
-tcExtendTyVarScope :: [HsTyVar Name]
- -> ([TcTyVar] -> TcM s a) -> TcM s a
-tcExtendTyVarScope tv_names thing_inside
- = mapNF_Tc tcHsTyVar tv_names `thenNF_Tc` \ tyvars ->
- tcExtendTyVarEnv tyvars $
- thing_inside tyvars
-
-tcHsTyVar :: HsTyVar Name -> NF_TcM s TcTyVar
-tcHsTyVar (UserTyVar name) = newKindVar `thenNF_Tc` \ kind ->
- tcNewMutTyVar name kind
- -- NB: mutable kind => mutable tyvar, so that zonking can bind
- -- the tyvar to its immutable form
-
-tcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (mkTyVar name (kindToTcKind kind))
-
-kcHsTyVar :: HsTyVar name -> NF_TcM s TcKind
-kcHsTyVar (UserTyVar name) = newKindVar
-kcHsTyVar (IfaceTyVar name kind) = returnNF_Tc (kindToTcKind kind)
+ (tyvars_w_kinds, _) = zipFunTys (hsTyVarNames tyvar_names) kind
\end{code}
\begin{code}
data TcSigInfo
= TySigInfo
- Name -- N, the Name in corresponding binding
-
TcId -- *Polymorphic* binder for this value...
-- Has name = N
-- Does *not* have name = N
-- Has type tau
- Inst -- 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
+
+tcSigMonoId :: TcSigInfo -> TcId
+tcSigMonoId (TySigInfo _ _ _ _ id _ _) = id
maybeSig :: [TcSigInfo] -> Name -> Maybe (TcSigInfo)
-- Search for a particular signature
maybeSig [] name = Nothing
-maybeSig (sig@(TySigInfo sig_name _ _ _ _ _ _ _) : sigs) name
- | name == sig_name = Just sig
- | otherwise = maybeSig sigs name
+maybeSig (sig@(TySigInfo sig_id _ _ _ _ _ _) : sigs) name
+ | name == idName sig_id = Just sig
+ | otherwise = maybeSig sigs name
\end{code}
\begin{code}
-tcTySig :: RenamedSig -> TcM s TcSigInfo
+tcTySig :: RenamedSig -> TcM TcSigInfo
tcTySig (Sig v ty src_loc)
- = tcAddSrcLoc src_loc $
- tcHsType ty `thenTc` \ sigma_tc_ty ->
- mkTcSig (mkVanillaId 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) `thenM` \ sig ->
+ returnM sig
-mkTcSig :: TcId -> SrcLoc -> NF_TcM s TcSigInfo
-mkTcSig poly_id src_loc
+mkTcSig :: TcId -> TcM TcSigInfo
+mkTcSig poly_id
= -- 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
-- 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) = splitForAllTys (idType poly_id)
- in
- mapNF_Tc tcInstSigVar 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'
- -- This splitRhoTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- newMethodWithGivenTy SignatureOrigin
- poly_id
- tyvar_tys'
- theta' tau' `thenNF_Tc` \ inst ->
+ tcInstType SigTv (idType poly_id) `thenM` \ (tyvars', theta', tau') ->
+
+ getInstLoc SignatureOrigin `thenM` \ inst_loc ->
+ 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
+ getSrcLocM `thenM` \ src_loc ->
+ returnM (TySigInfo poly_id tyvars' theta' tau'
+ (instToId inst) [inst] src_loc)
\end{code}
-
%************************************************************************
%* *
-\subsection{Checking signature type variables}
+\subsection{Errors and contexts}
%* *
%************************************************************************
-@checkSigTyVars@ is used after the type in a type signature has been unified with
-the actual type found. It then checks that the type variables of the type signature
-are
- (a) Still all type variables
- eg matching signature [a] against inferred type [(p,q)]
- [then a will be unified to a non-type variable]
-
- (b) Still all distinct
- eg matching signature [(a,b)] against inferred type [(p,p)]
- [then a and b will be unified together]
-
- (c) Not mentioned in the environment
- eg the signature for f in this:
-
- g x = ... where
- f :: a->[a]
- f y = [x,y]
-
- Here, f is forced to be monorphic by the free occurence of x.
-
- (d) Not (unified with another type variable that is) in scope.
- eg f x :: (r->r) = (\y->y) :: forall a. a->r
- when checking the expression type signature, we find that
- even though there is nothing in scope whose type mentions r,
- nevertheless the type signature for the expression isn't right.
-
- Another example is in a class or instance declaration:
- class C a where
- op :: forall b. a -> b
- op x = x
- Here, b gets unified with a
-
-Before doing this, the substitution is applied to the signature type variable.
-
-We used to have the notion of a "DontBind" type variable, which would
-only be bound to itself or nothing. Then points (a) and (b) were
-self-checking. But it gave rise to bogus consequential error messages.
-For example:
-
- f = (*) -- Monomorphic
-
- g :: Num a => a -> a
- g x = f x x
-
-Here, we get a complaint when checking the type signature for g,
-that g isn't polymorphic enough; but then we get another one when
-dealing with the (Num x) context arising from f's definition;
-we try to unify x with Int (to default it), but find that x has already
-been unified with the DontBind variable "a" from g's signature.
-This is really a problem with side-effecting unification; we'd like to
-undo g's effects when its type signature fails, but unification is done
-by side effect, so we can't (easily).
-
-So we revert to ordinary type variables for signatures, and try to
-give a helpful message in checkSigTyVars.
\begin{code}
-checkSigTyVars :: [TcTyVar] -- The original signature type variables
- -> TcM s [TcTyVar] -- 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
- = -- 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 ->
- 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]
- ]
- in_scope_env = mkVarEnv in_scope_assoc
- in
-
- -- "check" checks each sig tyvar in turn
- foldlNF_Tc check
- (env2, in_scope_env, [])
- (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) ->
-
- failWithTcM (env3, main_msg $$ nest 4 (vcat msgs))
- where
- (env1, tidy_tvs) = mapAccumL tidyTyVar emptyTidyEnv sig_tyvars
- (env2, tidy_tys) = tidyOpenTypes env1 sig_tys
-
- main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
-
- check (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 {
- Nothing -> -- Error (a)!
- returnNF_Tc (env, acc, unify_msg sig_tyvar (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) ;
-
- 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) ->
- returnNF_Tc (env1, acc, escape_msg sig_tyvar tv globs : msgs)
-
- else -- All OK
- returnNF_Tc (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 tv tidy_env ids
- | null ids
- = returnNF_Tc (tidy_env, [])
-
-find_globals tv tidy_env (id:ids)
- | not (isLocallyDefined id) ||
- isEmptyVarSet (idFreeTyVars id)
- = find_globals tv tidy_env ids
-
- | otherwise
- = zonkTcType (idType id) `thenNF_Tc` \ id_ty ->
- if tv `elemVarSet` tyVarsOfType id_ty then
- let
- (tidy_env', id_ty') = tidyOpenType tidy_env id_ty
- in
- find_globals tv tidy_env' ids `thenNF_Tc` \ (tidy_env'', globs) ->
- returnNF_Tc (tidy_env'', (idName id, id_ty') : globs)
- else
- find_globals tv tidy_env ids
-
-escape_msg sig_tv tv globs
- = vcat [mk_msg sig_tv <+> ptext SLIT("escapes"),
- pp_escape,
- ptext SLIT("The following variables in the environment mention") <+> quotes (ppr tv),
- nest 4 (vcat_first 10 [ppr name <+> dcolon <+> ppr ty | (name,ty) <- globs])
- ]
- where
- pp_escape | sig_tv /= tv = ptext SLIT("It unifies with") <+>
- quotes (ppr tv) <> comma <+>
- ptext SLIT("which is mentioned in the environment")
- | otherwise = ptext SLIT("It is mentioned in the environment")
-
- 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") <+> quotes thing
-mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv)
-\end{code}
+hoistForAllTys :: Type -> Type
+-- Used for user-written type signatures only
+-- Move all the foralls and constraints to the top
+-- e.g. T -> forall a. a ==> forall a. T -> a
+-- T -> (?x::Int) -> Int ==> (?x::Int) -> T -> Int
+--
+-- Also: eliminate duplicate constraints. These can show up
+-- when hoisting constraints, notably implicit parameters.
+--
+-- We want to 'look through' type synonyms when doing this
+-- so it's better done on the Type than the HsType
-These two context are used with checkSigTyVars
-
-\begin{code}
-sigCtxt :: (Type -> Message) -> Type
- -> TidyEnv -> NF_TcM s (TidyEnv, Message)
-sigCtxt mk_msg sig_ty tidy_env
+hoistForAllTys ty
= let
- (env1, tidy_sig_ty) = tidyOpenType tidy_env sig_ty
+ 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, mk_msg tidy_sig_ty)
-
-sigPatCtxt bound_tvs bound_ids tidy_env
- = returnNF_Tc (env1,
- sep [ptext SLIT("When checking a pattern that binds"),
- nest 4 (vcat (zipWith ppr_id show_ids tidy_tys))])
+ case hoist no_shadow_ty of
+ (tvs, theta, body) -> mkForAllTys tvs (mkFunTys (nubBy tcEqType theta) body)
+ -- The 'nubBy' eliminates duplicate constraints,
+ -- notably implicit parameters
where
- show_ids = filter is_interesting bound_ids
- is_interesting id = any (`elemVarSet` idFreeTyVars id) bound_tvs
-
- (env1, tidy_tys) = tidyOpenTypes tidy_env (map idType show_ids)
- ppr_id id ty = ppr id <+> dcolon <+> ppr ty
- -- Don't zonk the types so we get the separate, un-unified versions
+ hoist ty
+ | (tvs1, body_ty) <- tcSplitForAllTys ty,
+ not (null tvs1)
+ = case hoist body_ty of
+ (tvs2,theta,tau) -> (tvs1 ++ tvs2, theta, tau)
+
+ | Just (arg, res) <- tcSplitFunTy_maybe ty
+ = let
+ arg' = hoistForAllTys arg -- Don't forget to apply hoist recursively
+ in -- to the argument type
+ if (isPredTy arg') then
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, arg':theta, tau)
+ else
+ case hoist res of
+ (tvs,theta,tau) -> (tvs, theta, mkFunTy arg' tau)
+
+ | otherwise = ([], [], ty)
\end{code}
%************************************************************************
\begin{code}
-naughtyCCallContextErr clas_name
- = sep [ptext SLIT("Can't use class") <+> quotes (ppr clas_name),
- ptext SLIT("in a context")]
-
-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
-classAsTyConErr name
- = ptext SLIT("Class used as a type constructor:") <+> ppr name
-
-tyConAsClassErr name
- = ptext SLIT("Type constructor used as a class:") <+> ppr name
-
-tyVarAsClassErr name
- = ptext SLIT("Type variable used as a class:") <+> ppr name
-
-ambigErr (c, ts) ty
- = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprConstraint c ts),
- 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 =>."))]
+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 (AGlobal (ADataCon _)) = ptext SLIT("Data constructor")
+ 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