\section[TcMonoType]{Typechecking user-specified @MonoTypes@}
\begin{code}
-module TcMonoType ( tcHsType, tcHsRecType,
+module TcMonoType ( tcHsType, tcHsRecType, tcIfaceType,
tcHsSigType, tcHsLiftedSigType,
- tcRecClassContext, checkAmbiguity,
+ tcRecTheta, checkAmbiguity,
-- Kind checking
kcHsTyVar, kcHsTyVars, mkTyClTyVars,
- kcHsType, kcHsSigType, kcHsLiftedSigType, kcHsContext,
- tcTyVars, tcHsTyVars, mkImmutTyVars,
+ kcHsType, kcHsSigType, kcHsSigTypes,
+ kcHsLiftedSigType, kcHsContext,
+ tcScopedTyVars, tcHsTyVars, mkImmutTyVars,
TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
checkSigTyVars, sigCtxt, sigPatCtxt
tcGetGlobalTyVars, tcEnvTcIds, tcEnvTyVars,
TyThing(..), TcTyThing(..), tcExtendKindEnv
)
-import TcType ( TcKind, TcTyVar, TcThetaType, TcTauType,
- newKindVar, tcInstSigVar,
- zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar
+import TcMType ( newKindVar, tcInstSigVars,
+ zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar,
+ unifyKind, unifyOpenTypeKind
)
-import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
-import FunDeps ( grow )
-import TcUnify ( unifyKind, unifyOpenTypeKind )
-import Unify ( allDistinctTyVars )
-import Type ( Type, Kind, PredType(..), ThetaType, SigmaType, TauType,
+import TcType ( Type, Kind, SourceType(..), ThetaType, SigmaType, TauType,
mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
- zipFunTys, hoistForAllTys,
+ tcSplitForAllTys, tcSplitRhoTy,
+ hoistForAllTys, allDistinctTyVars,
+ zipFunTys,
mkSigmaTy, mkPredTy, mkTyConApp,
- mkAppTys, splitForAllTys, splitRhoTy, mkRhoTy,
+ mkAppTys, mkRhoTy,
liftedTypeKind, unliftedTypeKind, mkArrowKind,
- mkArrowKinds, getTyVar_maybe, getTyVar, splitFunTy_maybe,
+ mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe,
tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars,
tyVarsOfType, tyVarsOfPred, mkForAllTys,
- classesOfPreds, isUnboxedTupleType, isForAllTy
+ isUnboxedTupleType, tcIsForAllTy, isIPPred
)
-import PprType ( pprType, pprPred )
+import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
+import FunDeps ( grow )
+import PprType ( pprType, pprTheta, pprPred )
import Subst ( mkTopTyVarSubst, substTy )
import CoreFVs ( idFreeTyVars )
-import Id ( mkVanillaId, idName, idType )
+import Id ( mkLocalId, idName, idType )
import Var ( Id, Var, TyVar, mkTyVar, tyVarKind )
import VarEnv
import VarSet
import ErrUtils ( Message )
import TyCon ( TyCon, isSynTyCon, tyConArity, tyConKind )
-import Class ( ClassContext, classArity, classTyCon )
+import Class ( classArity, classTyCon )
import Name ( Name )
import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
import BasicTypes ( Boxity(..), RecFlag(..), isRec )
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)
in
tcExtendTyVarEnv tyvars (thing_inside tyvars)
-tcTyVars :: [Name]
- -> TcM a -- The kind checker
- -> TcM [TyVar]
-tcTyVars [] kind_check = returnTc []
-
-tcTyVars tv_names kind_check
+-- tcScopedTyVars is used for scoped type variables
+-- e.g. \ (x::a) (y::a) -> x+y
+-- They never have explicit kinds (because this is source-code only)
+-- They are mutable (because they can get bound to a more specific type)
+tcScopedTyVars :: [Name]
+ -> TcM a -- The kind checker
+ -> TcM b
+ -> TcM b
+tcScopedTyVars [] kind_check thing_inside = thing_inside
+
+tcScopedTyVars tv_names kind_check thing_inside
= mapNF_Tc newNamedKindVar tv_names `thenTc` \ kind_env ->
tcExtendKindEnv kind_env kind_check `thenTc_`
zonkKindEnv kind_env `thenNF_Tc` \ tvs_w_kinds ->
- listNF_Tc [tcNewSigTyVar name kind | (name,kind) <- tvs_w_kinds]
+ listTc [tcNewMutTyVar name kind | (name, kind) <- tvs_w_kinds] `thenNF_Tc` \ tyvars ->
+ tcExtendTyVarEnv tyvars thing_inside
\end{code}
---------------------------
kcHsSigType, kcHsLiftedSigType :: RenamedHsType -> TcM ()
-- Used for type signatures
-kcHsSigType = kcTypeType
+kcHsSigType = kcTypeType
+kcHsSigTypes tys = mapTc_ kcHsSigType tys
kcHsLiftedSigType = kcLiftedType
---------------------------
kcTypeType ty2 `thenTc_`
returnTc liftedTypeKind
+kcHsType (HsNumTy _) -- The unit type for generics
+ = returnTc liftedTypeKind
+
kcHsType ty@(HsOpTy ty1 op ty2)
= kcTyVar op `thenTc` \ op_kind ->
kcHsType ty1 `thenTc` \ ty1_kind ->
---------------------------
kcAppKind fun_kind arg_kind
- = case splitFunTy_maybe fun_kind of
+ = case tcSplitFunTy_maybe fun_kind of
Just (arg_kind', res_kind)
-> unifyKind arg_kind arg_kind' `thenTc_`
returnTc res_kind
kcHsContext ctxt = mapTc_ kcHsPred ctxt
kcHsPred :: RenamedHsPred -> TcM ()
-kcHsPred pred@(HsPIParam name ty)
+kcHsPred pred@(HsIParam name ty)
= tcAddErrCtxt (appKindCtxt (ppr pred)) $
kcLiftedType ty
-kcHsPred pred@(HsPClass cls tys)
+kcHsPred pred@(HsClassP cls tys)
= tcAddErrCtxt (appKindCtxt (ppr pred)) $
kcClass cls `thenTc` \ kind ->
mapTc kcHsType tys `thenTc` \ arg_kinds ->
\begin{code}
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
+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}
= 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))
+ --
+ -- In a recursive loop we can't ask whether the thing is
+ -- unboxed -- might be a synonym inside a synonym inside a group
+ checkTc (isRec wimp_out || not (isUnboxedTupleType tau_ty1))
(ubxArgTyErr ty1) `thenTc_`
tc_type wimp_out ty2 `thenTc` \ tau_ty2 ->
returnTc (mkFunTy tau_ty1 tau_ty2)
kind_check = kcHsContext ctxt `thenTc_` kcHsType ty
in
tcHsTyVars tv_names kind_check $ \ tyvars ->
- tc_context wimp_out ctxt `thenTc` \ theta ->
+ tcRecTheta wimp_out ctxt `thenTc` \ theta ->
-- Context behaves like a function type
-- This matters. Return-unboxed-tuple analysis can
= 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_`
+ = tc_type wimp_out arg_ty `thenTc` \ arg_ty' ->
+ checkTc (isRec wimp_out || not (tcIsForAllTy arg_ty')) (polyArgTyErr arg_ty) `thenTc_`
+ checkTc (isRec wimp_out || 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
Contexts
~~~~~~~~
\begin{code}
-tcRecClassContext :: RecFlag -> RenamedContext -> TcM ClassContext
+tcRecTheta :: RecFlag -> RenamedContext -> TcM ThetaType
-- Used when we are expecting a ClassContext (i.e. no implicit params)
-tcRecClassContext wimp_out context
- = tc_context wimp_out context `thenTc` \ theta ->
- returnTc (classesOfPreds theta)
-
-tc_context :: RecFlag -> RenamedContext -> TcM ThetaType
-tc_context wimp_out context = mapTc (tc_pred wimp_out) context
+tcRecTheta wimp_out context = mapTc (tc_pred wimp_out) context
-tc_pred wimp_out assn@(HsPClass class_name tys)
+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
AClass clas -> checkTc (arity == n_tys) err `thenTc_`
- returnTc (Class clas arg_tys)
+ returnTc (ClassP clas arg_tys)
where
arity = classArity clas
n_tys = length tys
other -> failWithTc (wrongThingErr "class" (AGlobal thing) class_name)
-tc_pred wimp_out assn@(HsPIParam name ty)
+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)
tau_vars = tyVarsOfType tau
extended_tau_vars = grow theta tau_vars
+ -- Hack alert. If there are no tyvars, (ppr sigma_ty) will print
+ -- something strange like {Eq k} -> k -> k, because there is no
+ -- ForAll at the top of the type. Since this is going to the user
+ -- we want it to look like a proper Haskell type even then; hence the hack
+ --
+ -- This shows up in the complaint about
+ -- case C a where
+ -- op :: Eq a => a -> a
+ ppr_sigma | null forall_tyvars = pprTheta theta <+> ptext SLIT("=>") <+> ppr tau
+ | otherwise = ppr sigma_ty
+
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 (is_ip pred || not all_free) (freeErr pred sigma_ty)
+ check_pred pred = checkTc (not any_ambig) (ambigErr pred ppr_sigma) `thenTc_`
+ checkTc (isIPPred pred || not all_free) (freeErr pred ppr_sigma)
where
ct_vars = varSetElems (tyVarsOfPred pred)
all_free = all is_free ct_vars
any_ambig = is_source_polytype && any is_ambig ct_vars
- is_ip (IParam _ _) = True
- is_ip _ = False
\end{code}
%************************************************************************
= tcAddSrcLoc src_loc $
tcAddErrCtxt (tcsigCtxt v) $
tcHsSigType ty `thenTc` \ sigma_tc_ty ->
- mkTcSig (mkVanillaId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
+ mkTcSig (mkLocalId v sigma_tc_ty) src_loc `thenNF_Tc` \ sig ->
returnTc sig
mkTcSig :: TcId -> SrcLoc -> NF_TcM TcSigInfo
-- typechecking the rest of the program with the function bound
-- to a pristine type, namely sigma_tc_ty
let
- (tyvars, rho) = splitForAllTys (idType poly_id)
+ (tyvars, rho) = tcSplitForAllTys (idType poly_id)
in
- mapNF_Tc tcInstSigVar tyvars `thenNF_Tc` \ tyvars' ->
+ tcInstSigVars tyvars `thenNF_Tc` \ tyvars' ->
-- Make *signature* type variables
let
tyvar_tys' = mkTyVarTys tyvars'
rho' = substTy (mkTopTyVarSubst tyvars tyvar_tys') rho
-- mkTopTyVarSubst because the tyvars' are fresh
- (theta', tau') = splitRhoTy rho'
+
+ (theta', tau') = tcSplitRhoTy rho'
-- This splitRhoTy tries hard to make sure that tau' is a type synonym
-- wherever possible, which can improve interface files.
in
checkTcM (allDistinctTyVars sig_tys globals)
(complain sig_tys globals) `thenTc_`
- returnTc (map (getTyVar "checkSigTyVars") sig_tys)
+ returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys)
where
complain sig_tys globals
let
in_scope_assoc = [ (zonked_tv, in_scope_tv)
| (z_ty, in_scope_tv) <- in_scope_tys `zip` in_scope_tvs,
- Just zonked_tv <- [getTyVar_maybe z_ty]
+ Just zonked_tv <- [tcGetTyVar_maybe z_ty]
]
in_scope_env = mkVarEnv in_scope_assoc
in
-- ty is what you get if you zonk sig_tyvar and then tidy it
--
-- acc maps a zonked type variable back to a signature type variable
- = case getTyVar_maybe ty of {
+ = case tcGetTyVar_maybe ty of {
Nothing -> -- Error (a)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (ppr ty) : msgs) ;
+ returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ;
Just tv ->
case lookupVarEnv acc tv of {
Just sig_tyvar' -> -- Error (b) or (d)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (ppr sig_tyvar') : msgs) ;
+ returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
+ where
+ thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar')
- Nothing ->
+ ; Nothing ->
if tv `elemVarSet` globals -- Error (c)! Type variable escapes
-- The least comprehensible, so put it last
vcat_first 0 (x:xs) = text "...others omitted..."
vcat_first n (x:xs) = x $$ vcat_first (n-1) xs
-unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> quotes thing
+unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> thing
mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv)
\end{code}
pp_thing (ATcId _) = ptext SLIT("Local identifier")
pp_thing (AThing _) = ptext SLIT("Utterly bogus")
-ambigErr pred ty
+ambigErr pred ppr_ty
= sep [ptext SLIT("Ambiguous constraint") <+> quotes (pprPred pred),
- nest 4 (ptext SLIT("for the type:") <+> ppr ty),
+ nest 4 (ptext SLIT("for the type:") <+> ppr_ty),
nest 4 (ptext SLIT("At least one of the forall'd type variables mentioned by the constraint") $$
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))
+freeErr pred ppr_ty
+ = sep [ptext SLIT("All of the type variables in the constraint") <+> quotes (pprPred pred) <+>
+ ptext SLIT("are already in scope"),
+ nest 4 (ptext SLIT("At least one must be universally quantified here")),
+ ptext SLIT("In the type") <+> quotes ppr_ty
]
polyArgTyErr ty = ptext SLIT("Illegal polymorphic type as argument:") <+> ppr ty
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