\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsTypeKind, tcHsTopType, tcHsTopBoxedType, tcHsTopTypeKind,
- tcContext, tcHsTyVar, kcHsTyVar,
- tcExtendTyVarScope, tcExtendTopTyVarScope,
+module TcMonoType ( tcHsType, tcHsRecType, tcIfaceType,
+ tcHsSigType, tcHsLiftedSigType,
+ tcRecTheta, checkAmbiguity,
+
+ -- Kind checking
+ kcHsTyVar, kcHsTyVars, mkTyClTyVars,
+ kcHsType, kcHsSigType, kcHsLiftedSigType, kcHsContext,
+ tcTyVars, tcHsTyVars, mkImmutTyVars,
+
TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
checkSigTyVars, sigCtxt, sigPatCtxt
) where
#include "HsVersions.h"
-import HsSyn ( HsType(..), HsTyVar(..), MonoUsageAnn(..),
- Sig(..), pprClassAssertion, pprParendHsType )
-import RnHsSyn ( RenamedHsType, RenamedContext, RenamedSig )
+import HsSyn ( HsType(..), HsTyVarBndr(..),
+ Sig(..), HsPred(..), pprParendHsType, HsTupCon(..), hsTyVarNames )
+import RnHsSyn ( RenamedHsType, RenamedHsPred, RenamedContext, RenamedSig )
import TcHsSyn ( TcId )
import TcMonad
-import TcEnv ( tcExtendTyVarEnv, tcLookupTy, tcGetValueEnv, tcGetInScopeTyVars,
- tcExtendUVarEnv, tcLookupUVar,
- tcGetGlobalTyVars, valueEnvIds, TcTyThing(..)
+import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
+ tcGetGlobalTyVars, tcEnvTcIds, tcEnvTyVars,
+ TyThing(..), TcTyThing(..), tcExtendKindEnv
)
-import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType,
- typeToTcType, kindToTcKind,
+import TcType ( TcKind, TcTyVar, TcThetaType, TcTauType,
newKindVar, tcInstSigVar,
- zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType
+ zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar
)
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr )
-import TcUnify ( unifyKind, unifyKinds, unifyTypeKind )
-import Type ( Type, 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
+import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
+import FunDeps ( grow )
+import TcUnify ( unifyKind, unifyOpenTypeKind )
+import Unify ( allDistinctTyVars )
+import Type ( Type, Kind, PredType(..), ThetaType, SigmaType, TauType,
+ mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
+ zipFunTys, hoistForAllTys,
+ mkSigmaTy, mkPredTy, mkTyConApp,
+ mkAppTys, splitForAllTys, splitRhoTy, mkRhoTy,
+ liftedTypeKind, unliftedTypeKind, mkArrowKind,
+ mkArrowKinds, getTyVar_maybe, getTyVar, splitFunTy_maybe,
+ tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars,
+ tyVarsOfType, tyVarsOfPred, mkForAllTys,
+ isUnboxedTupleType, isForAllTy, isIPPred
)
+import PprType ( pprType, pprPred )
import Subst ( mkTopTyVarSubst, substTy )
-import Id ( mkVanillaId, idName, idType, idFreeTyVars )
-import Var ( TyVar, mkTyVar, mkNamedUVar )
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, idName, idType )
+import Var ( Id, Var, TyVar, mkTyVar, tyVarKind )
import VarEnv
import VarSet
-import Bag ( bagToList )
import ErrUtils ( Message )
-import PrelInfo ( cCallishClassKeys )
-import TyCon ( TyCon )
-import Name ( Name, OccName, isLocallyDefined )
-import TysWiredIn ( mkListTy, mkTupleTy, mkUnboxedTupleTy )
+import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind )
+import Class ( classArity, classTyCon )
+import Name ( Name )
+import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
+import BasicTypes ( Boxity(..), RecFlag(..), isRec )
import SrcLoc ( SrcLoc )
-import Unique ( Unique, Uniquable(..) )
-import Util ( zipWithEqual, zipLazy, mapAccumL )
+import Util ( mapAccumL, isSingleton )
import Outputable
+
\end{code}
%************************************************************************
%* *
+\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}
+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
+ tyvars = mkImmutTyVars tvs_w_kinds
+ in
+ tcExtendTyVarEnv tyvars (thing_inside tyvars)
+
+tcTyVars :: [Name]
+ -> TcM a -- The kind checker
+ -> TcM [TyVar]
+tcTyVars [] kind_check = returnTc []
+
+tcTyVars tv_names kind_check
+ = mapNF_Tc newNamedKindVar tv_names `thenTc` \ kind_env ->
+ tcExtendKindEnv kind_env kind_check `thenTc_`
+ zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds ->
+ listNF_Tc [tcNewSigTyVar name kind | (name,kind) <- tvs_w_kinds]
+\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
+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 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 splitFunTy_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{Checking types}
%* *
%************************************************************************
-tcHsType and tcHsTypeKind
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+tcHsSigType and tcHsLiftedSigType
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+tcHsSigType and tcHsLiftedSigType are used for type signatures written by the programmer
+
+ * We hoist any inner for-alls to the top
-tcHsType checks that the type really is of kind Type!
+ * Notice that we kind-check first, because the type-check assumes
+ that the kinds are already checked.
+
+ * They are only called when there are no kind vars in the environment
+ so the kind returned is indeed a Kind not a TcKind
\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, tcHsLiftedSigType :: RenamedHsType -> TcM Type
+ -- Do kind checking, and hoist for-alls to the top
+tcHsSigType ty = kcTypeType ty `thenTc_` tcHsType ty
+tcHsLiftedSigType ty = kcLiftedType ty `thenTc_` tcHsType ty
+
+tcHsType :: RenamedHsType -> TcM Type
+tcHsRecType :: RecFlag -> RenamedHsType -> TcM Type
+ -- Don't do kind checking, but do hoist for-alls to the top
+ -- These are used in type and class decls, where kinding is
+ -- done in advance
+tcHsType ty = tc_type NonRecursive ty `thenTc` \ ty' -> returnTc (hoistForAllTys ty')
+tcHsRecType wimp_out ty = tc_type wimp_out ty `thenTc` \ ty' -> returnTc (hoistForAllTys ty')
+
+-- 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 NonRecursive ty
\end{code}
-The main work horse
-~~~~~~~~~~~~~~~~~~~
+%************************************************************************
+%* *
+\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!
+
+The wimp_out argument tells when we are in a mutually-recursive
+group of type declarations, so omit various checks else we
+get a black hole. They'll be done again later, in TcTyClDecls.tcGroup.
+
+ --------------------------
+ *** END OF BIG WARNING ***
+ --------------------------
+
\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 []
-
-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 (class_name, tys) `thenTc` \ (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)
- where
- newUsg usg = case usg of
- MonoUsOnce -> returnTc UsOnce
- MonoUsMany -> returnTc UsMany
- MonoUsVar uv_name -> tcLookupUVar uv_name `thenTc` \ uv ->
- returnTc (UsVar uv)
+tc_type :: RecFlag -> RenamedHsType -> TcM Type
+
+tc_type wimp_out ty@(HsTyVar name)
+ = tc_app wimp_out ty []
-tc_type_kind (MonoUsgForAllTy uv_name ty)
+tc_type wimp_out (HsListTy ty)
+ = tc_arg_type wimp_out ty `thenTc` \ tau_ty ->
+ returnTc (mkListTy tau_ty)
+
+tc_type wimp_out (HsTupleTy (HsTupCon _ boxity arity) tys)
+ = ASSERT( arity == length tys )
+ mapTc tc_tup_arg tys `thenTc` \ tau_tys ->
+ returnTc (mkTupleTy boxity arity tau_tys)
+ where
+ tc_tup_arg = case boxity of
+ Boxed -> tc_arg_type wimp_out
+ Unboxed -> tc_type wimp_out
+ -- Unboxed tuples can have polymorphic or unboxed args.
+ -- This happens in the workers for functions returning
+ -- product types with polymorphic components
+
+tc_type wimp_out (HsFunTy ty1 ty2)
+ = tc_type wimp_out ty1 `thenTc` \ tau_ty1 ->
+ -- Function argument can be polymorphic, but
+ -- must not be an unboxed tuple
+ checkTc (not (isUnboxedTupleType tau_ty1))
+ (ubxArgTyErr ty1) `thenTc_`
+ tc_type wimp_out ty2 `thenTc` \ tau_ty2 ->
+ returnTc (mkFunTy tau_ty1 tau_ty2)
+
+tc_type wimp_out (HsNumTy n)
+ = ASSERT(n== 1)
+ returnTc (mkTyConApp genUnitTyCon [])
+
+tc_type wimp_out (HsOpTy ty1 op ty2) =
+ tc_arg_type wimp_out ty1 `thenTc` \ tau_ty1 ->
+ tc_arg_type wimp_out ty2 `thenTc` \ tau_ty2 ->
+ tc_fun_type op [tau_ty1,tau_ty2]
+
+tc_type wimp_out (HsAppTy ty1 ty2)
+ = tc_app wimp_out ty1 [ty2]
+
+tc_type wimp_out (HsPredTy pred)
+ = tc_pred wimp_out pred `thenTc` \ pred' ->
+ returnTc (mkPredTy pred')
+
+tc_type wimp_out 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) ->
- 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
+ kind_check = kcHsContext ctxt `thenTc_` kcHsType ty
in
- returnTc (body_kind, mkSigmaTy tyvars theta tau)
+ tcHsTyVars tv_names kind_check $ \ tyvars ->
+ tcRecTheta wimp_out ctxt `thenTc` \ theta ->
+
+ -- 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
+ (if null theta then
+ tc_arg_type wimp_out ty
+ else
+ tc_type wimp_out ty
+ ) `thenTc` \ tau ->
+
+ checkAmbiguity wimp_out is_source tyvars theta tau
+ where
+ is_source = case tv_names of
+ (UserTyVar _ : _) -> True
+ other -> False
+
+
+ -- tc_arg_type checks that the argument of a
+ -- type appplication isn't a for-all type or an unboxed tuple type
+ -- For example, we want to reject things like:
+ --
+ -- instance Ord a => Ord (forall s. T s a)
+ -- and
+ -- g :: T s (forall b.b)
+ --
+ -- Other unboxed types are very occasionally allowed as type
+ -- arguments depending on the kind of the type constructor
+
+tc_arg_type wimp_out arg_ty
+ | isRec wimp_out
+ = tc_type wimp_out arg_ty
+
+ | otherwise
+ = tc_type wimp_out arg_ty `thenTc` \ arg_ty' ->
+ checkTc (not (isForAllTy arg_ty')) (polyArgTyErr arg_ty) `thenTc_`
+ checkTc (not (isUnboxedTupleType arg_ty')) (ubxArgTyErr arg_ty) `thenTc_`
+ returnTc arg_ty'
+
+tc_arg_types wimp_out arg_tys = mapTc (tc_arg_type wimp_out) arg_tys
\end{code}
Help functions for type applications
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
\begin{code}
-tc_app (MonoTyApp ty1 ty2) tys
- = tc_app ty1 (ty2:tys)
-
-tc_app ty tys
- | null tys
- = tc_fun_type ty []
+tc_app :: RecFlag -> RenamedHsType -> [RenamedHsType] -> TcM Type
+tc_app wimp_out (HsAppTy ty1 ty2) tys
+ = tc_app wimp_out ty1 (ty2:tys)
- | otherwise
+tc_app wimp_out ty tys
= 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)
+ tc_arg_types wimp_out tys `thenTc` \ arg_tys ->
+ case ty of
+ HsTyVar fun -> tc_fun_type fun arg_tys
+ other -> tc_type wimp_out 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 (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 `thenTc` \ 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 -> returnTc (mkAppTys (mkTyVarTy tv) arg_tys)
+
+ AGlobal (ATyCon tc)
+ | isSynTyCon tc -> checkTc arity_ok err_msg `thenTc_`
+ returnTc (mkAppTys (mkSynTy tc (take arity arg_tys))
+ (drop arity arg_tys))
+
+ | otherwise -> returnTc (mkTyConApp tc arg_tys)
+ where
+
+ arity_ok = arity <= n_args
+ arity = tyConArity tc
+ -- It's OK to have an *over-applied* type synonym
+ -- data Tree a b = ...
+ -- type Foo a = Tree [a]
+ -- f :: Foo a b -> ...
+ err_msg = arityErr "Type synonym" name arity n_args
+ n_args = length arg_tys
+
+ other -> failWithTc (wrongThingErr "type constructor" thing name)
\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 (class_name, _)
- = checkTc (not (getUnique class_name `elem` cCallishClassKeys))
- (naughtyCCallContextErr class_name)
-
-tcClassAssertion assn@(class_name, tys)
- = tcAddErrCtxt (appKindCtxt (pprClassAssertion assn)) $
- mapAndUnzipTc tc_type_kind tys `thenTc` \ (arg_kinds, arg_tys) ->
- tcLookupTy class_name `thenTc` \ (kind, ~(Just arity), thing) ->
+tcRecTheta :: RecFlag -> RenamedContext -> TcM ThetaType
+ -- Used when we are expecting a ClassContext (i.e. no implicit params)
+tcRecTheta wimp_out context = mapTc (tc_pred wimp_out) context
+
+tc_pred wimp_out assn@(HsClassP class_name tys)
+ = tcAddErrCtxt (appKindCtxt (ppr assn)) $
+ tc_arg_types wimp_out tys `thenTc` \ arg_tys ->
+ tcLookupGlobal class_name `thenTc` \ 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 (clas, arg_tys)
+ AClass clas -> checkTc (arity == n_tys) err `thenTc_`
+ returnTc (ClassP clas arg_tys)
where
+ arity = classArity clas
n_tys = length tys
err = arityErr "Class" class_name arity n_tys
+
+ other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name)
+
+tc_pred wimp_out assn@(HsIParam name ty)
+ = tcAddErrCtxt (appKindCtxt (ppr assn)) $
+ tc_arg_type wimp_out ty `thenTc` \ arg_ty ->
+ returnTc (IParam name arg_ty)
\end{code}
+Check for ambiguity
+~~~~~~~~~~~~~~~~~~~
+ forall V. P => tau
+is ambiguous if P contains generic variables
+(i.e. one of the Vs) that are not mentioned in tau
+
+However, we need to take account of functional dependencies
+when we speak of 'mentioned in tau'. Example:
+ class C a b | a -> b where ...
+Then the type
+ forall x y. (C x y) => x
+is not ambiguous because x is mentioned and x determines y
+
+NOTE: In addition, GHC insists that at least one type variable
+in each constraint is in V. So we disallow a type like
+ forall a. Eq b => b -> b
+even in a scope where b is in scope.
+This is the is_free test below.
+
+Notes on the 'is_source_polytype' test above
+Check ambiguity only for source-program types, not
+for types coming from inteface files. The latter can
+legitimately have ambiguous types. Example
+ class S a where s :: a -> (Int,Int)
+ instance S Char where s _ = (1,1)
+ f:: S a => [a] -> Int -> (Int,Int)
+ f (_::[a]) x = (a*x,b)
+ where (a,b) = s (undefined::a)
+Here the worker for f gets the type
+ fw :: forall a. S a => Int -> (# Int, Int #)
+
+If the list of tv_names is empty, we have a monotype,
+and then we don't need to check for ambiguity either,
+because the test can't fail (see is_ambig).
+
+\begin{code}
+checkAmbiguity :: RecFlag -> Bool
+ -> [TyVar] -> ThetaType -> TauType
+ -> TcM SigmaType
+checkAmbiguity wimp_out is_source_polytype forall_tyvars theta tau
+ | isRec wimp_out = returnTc sigma_ty
+ | otherwise = mapTc_ check_pred theta `thenTc_`
+ returnTc sigma_ty
+ where
+ sigma_ty = mkSigmaTy forall_tyvars theta tau
+ tau_vars = tyVarsOfType tau
+ extended_tau_vars = grow theta tau_vars
+
+ is_ambig ct_var = (ct_var `elem` forall_tyvars) &&
+ not (ct_var `elemVarSet` extended_tau_vars)
+ is_free ct_var = not (ct_var `elem` forall_tyvars)
+
+ check_pred pred = checkTc (not any_ambig) (ambigErr pred sigma_ty) `thenTc_`
+ checkTc (isIPPred pred || not all_free) (freeErr pred sigma_ty)
+ where
+ ct_vars = varSetElems (tyVarsOfPred pred)
+ all_free = all is_free ct_vars
+ any_ambig = is_source_polytype && any is_ambig ct_vars
+\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}
-- 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 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
\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 ->
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (tcsigCtxt v) $
+ tcHsSigType ty `thenTc` \ sigma_tc_ty ->
+ mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
returnTc sig
-mkTcSig :: TcId -> SrcLoc -> NF_TcM s TcSigInfo
+mkTcSig :: TcId -> SrcLoc -> NF_TcM TcSigInfo
mkTcSig poly_id src_loc
= -- Instantiate this type
-- It's important to do this even though in the error-free case
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' (instToIdBndr inst) inst src_loc)
+ returnNF_Tc (TySigInfo name poly_id tyvars' theta' tau' (instToId inst) [inst] src_loc)
where
name = idName poly_id
\end{code}
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
+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 (all_ok sig_tys globals)
+ checkTcM (allDistinctTyVars 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 ->
+ tcGetEnv `thenNF_Tc` \ env ->
+ let
+ in_scope_tvs = tcEnvTyVars env
+ in
zonkTcTyVars in_scope_tvs `thenNF_Tc` \ in_scope_tys ->
let
in_scope_assoc = [ (zonked_tv, in_scope_tv)
main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
- check (env, acc, msgs) (sig_tyvar,ty)
+ check (tidy_env, acc, msgs) (sig_tyvar,ty)
-- sig_tyvar is from the signature;
-- ty is what you get if you zonk sig_tyvar and then tidy it
--
-- acc maps a zonked type variable back to a signature type variable
= case getTyVar_maybe ty of {
Nothing -> -- Error (a)!
- returnNF_Tc (env, acc, unify_msg sig_tyvar (ppr ty) : msgs) ;
+ returnNF_Tc (tidy_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) ;
+ returnNF_Tc (tidy_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)
+ -- Game plan:
+ -- a) get the local TcIds from the environment,
+ -- and pass them to find_globals (they might have tv free)
+ -- b) similarly, find any free_tyvars that mention tv
+ then tcGetEnv `thenNF_Tc` \ ve ->
+ find_globals tv tidy_env [] (tcEnvTcIds ve) `thenNF_Tc` \ (tidy_env1, globs) ->
+ find_frees tv tidy_env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (tidy_env2, frees) ->
+ returnNF_Tc (tidy_env2, acc, escape_msg sig_tyvar tv globs frees : msgs)
else -- All OK
- returnNF_Tc (env, extendVarEnv acc tv sig_tyvar, msgs)
+ returnNF_Tc (tidy_env, extendVarEnv acc tv sig_tyvar, msgs)
}}
-- find_globals looks at the value environment and finds values
-- whose types mention the offending type variable. It has to be
-- careful to zonk the Id's type first, so it has to be in the monad.
-- We must be careful to pass it a zonked type variable, too.
-find_globals 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
+find_globals :: Var
+ -> TidyEnv
+ -> [(Name,Type)]
+ -> [Id]
+ -> NF_TcM (TidyEnv,[(Name,Type)])
+
+find_globals tv tidy_env acc []
+ = returnNF_Tc (tidy_env, acc)
+
+find_globals tv tidy_env acc (id:ids)
+ | isEmptyVarSet (idFreeTyVars id)
+ = find_globals tv tidy_env acc 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
+ acc' = (idName id, id_ty') : acc
in
- find_globals tv tidy_env' ids `thenNF_Tc` \ (tidy_env'', globs) ->
- returnNF_Tc (tidy_env'', (idName id, id_ty') : globs)
+ find_globals tv tidy_env' acc' ids
else
- find_globals tv tidy_env ids
+ find_globals tv tidy_env acc 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])
- ]
+find_frees tv tidy_env acc []
+ = returnNF_Tc (tidy_env, acc)
+find_frees tv tidy_env acc (ftv:ftvs)
+ = zonkTcTyVar ftv `thenNF_Tc` \ ty ->
+ if tv `elemVarSet` tyVarsOfType ty then
+ let
+ (tidy_env', ftv') = tidyTyVar tidy_env ftv
+ in
+ find_frees tv tidy_env' (ftv':acc) ftvs
+ else
+ find_frees tv tidy_env acc ftvs
+
+
+escape_msg sig_tv tv globs frees
+ = mk_msg sig_tv <+> ptext SLIT("escapes") $$
+ if not (null globs) then
+ vcat [pp_it <+> ptext SLIT("is mentioned in the environment"),
+ ptext SLIT("The following variables in the environment mention") <+> quotes (ppr tv),
+ nest 2 (vcat_first 10 [ppr name <+> dcolon <+> ppr ty | (name,ty) <- 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
- 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")
+ 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
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
- = let
- (env1, tidy_sig_ty) = tidyOpenType tidy_env sig_ty
+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) = tidyTyVars 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 (env1, mk_msg tidy_sig_ty)
+ returnNF_Tc (env3, msg)
sigPatCtxt bound_tvs bound_ids tidy_env
= returnNF_Tc (env1,
%************************************************************************
\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)
+tcsigCtxt v = ptext SLIT("In a type signature for") <+> quotes (ppr v)
typeKindCtxt :: RenamedHsType -> Message
typeKindCtxt ty = sep [ptext SLIT("When checking that"),
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
+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")
+
+ambigErr pred ty
+ = sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred),
+ nest 4 (ptext SLIT("for the type:") <+> ppr ty),
+ nest 4 (ptext SLIT("At least one of the forall'd type variables mentioned by the constraint") $$
+ ptext SLIT("must be reachable from the type after the =>"))]
+
+freeErr pred ty
+ = sep [ptext SLIT("The constraint") <+> quotes (pprPred pred) <+>
+ ptext SLIT("does not mention any of the universally quantified type variables"),
+ nest 4 (ptext SLIT("in the type") <+> quotes (ppr ty))
+ ]
-tyVarAsClassErr name
- = ptext SLIT("Type variable used as a class:") <+> ppr name
+polyArgTyErr ty = ptext SLIT("Illegal polymorphic type as argument:") <+> ppr ty
+ubxArgTyErr ty = ptext SLIT("Illegal unboxed tuple type as argument:") <+> ppr ty
\end{code}
projects / ghc-hetmet.git / blobdiff