\begin{code}
module TcUnify ( unifyTauTy, unifyTauTyList, unifyTauTyLists,
- unifyFunTy, unifyListTy, unifyTupleTy, unifyUnboxedTupleTy,
- unifyKind, unifyKinds, unifyTypeKind
+ unifyFunTy, unifyListTy, unifyTupleTy,
+ unifyKind, unifyKinds, unifyOpenTypeKind
) where
#include "HsVersions.h"
-- friends:
import TcMonad
-import Type ( Type(..), tyVarsOfType, funTyCon,
+import TypeRep ( Type(..), PredType(..) ) -- friend
+import Type ( unboxedTypeKind, boxedTypeKind, openTypeKind,
+ typeCon, openKindCon, hasMoreBoxityInfo,
+ tyVarsOfType, typeKind,
mkFunTy, splitFunTy_maybe, splitTyConApp_maybe,
- Kind, boxedTypeKind, typeCon, anyBoxCon, anyBoxKind,
- splitAppTy_maybe,
+ isNotUsgTy, splitAppTy_maybe, mkTyConApp,
tidyOpenType, tidyOpenTypes, tidyTyVar
)
-import TyCon ( TyCon, isTupleTyCon, isUnboxedTupleTyCon,
- tyConArity )
-import Name ( isSysLocalName )
-import Var ( TyVar, tyVarKind, varName )
-import VarEnv
+import TyCon ( TyCon, isTupleTyCon, tupleTyConBoxity, tyConArity )
+import Var ( tyVarKind, varName, isSigTyVar )
import VarSet ( varSetElems )
-import TcType ( TcType, TcTauType, TcTyVar, TcKind,
- newTyVarTy, newOpenTypeKind, newTyVarTy_OpenKind,
- tcGetTyVar, tcPutTyVar, zonkTcType, tcTypeKind
+import TcType ( TcType, TcTauType, TcTyVar, TcKind, newBoxityVar,
+ newTyVarTy, newTyVarTys, tcGetTyVar, tcPutTyVar, zonkTcType
)
+import Name ( isSystemName )
+
-- others:
-import BasicTypes ( Arity )
-import TysWiredIn ( listTyCon, mkListTy, mkTupleTy, mkUnboxedTupleTy )
-import PprType () -- Instances
-import Util
+import BasicTypes ( Arity, Boxity, isBoxed )
+import TysWiredIn ( listTyCon, mkListTy, mkTupleTy )
import Outputable
\end{code}
\begin{code}
unifyKind :: TcKind -- Expected
-> TcKind -- Actual
- -> TcM s ()
+ -> TcM ()
unifyKind k1 k2
= tcAddErrCtxtM (unifyCtxt "kind" k1 k2) $
uTys k1 k1 k2 k2
-unifyKinds :: [TcKind] -> [TcKind] -> TcM s ()
+unifyKinds :: [TcKind] -> [TcKind] -> TcM ()
unifyKinds [] [] = returnTc ()
unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenTc_`
unifyKinds ks1 ks2
unifyKinds _ _ = panic "unifyKinds: length mis-match"
\end{code}
+\begin{code}
+unifyOpenTypeKind :: TcKind -> TcM ()
+-- Ensures that the argument kind is of the form (Type bx)
+-- for some boxity bx
+
+unifyOpenTypeKind ty@(TyVarTy tyvar)
+ = tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyOpenTypeKind ty'
+ other -> unify_open_kind_help ty
+
+unifyOpenTypeKind ty
+ = case splitTyConApp_maybe ty of
+ Just (tycon, [_]) | tycon == typeCon -> returnTc ()
+ other -> unify_open_kind_help ty
+
+unify_open_kind_help ty -- Revert to ordinary unification
+ = newBoxityVar `thenNF_Tc` \ boxity ->
+ unifyKind ty (mkTyConApp typeCon [boxity])
+\end{code}
+
%************************************************************************
%* *
Unify two @TauType@s. Dead straightforward.
\begin{code}
-unifyTauTy :: TcTauType -> TcTauType -> TcM s ()
+unifyTauTy :: TcTauType -> TcTauType -> TcM ()
unifyTauTy ty1 ty2 -- ty1 expected, ty2 inferred
= tcAddErrCtxtM (unifyCtxt "type" ty1 ty2) $
uTys ty1 ty1 ty2 ty2
complain if their lengths differ.
\begin{code}
-unifyTauTyLists :: [TcTauType] -> [TcTauType] -> TcM s ()
+unifyTauTyLists :: [TcTauType] -> [TcTauType] -> TcM ()
unifyTauTyLists [] [] = returnTc ()
unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenTc_`
unifyTauTyLists tys1 tys2
lists, when all the elts should be of the same type.
\begin{code}
-unifyTauTyList :: [TcTauType] -> TcM s ()
+unifyTauTyList :: [TcTauType] -> TcM ()
unifyTauTyList [] = returnTc ()
unifyTauTyList [ty] = returnTc ()
unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenTc_`
\begin{code}
uTys :: TcTauType -> TcTauType -- Error reporting ty1 and real ty1
+ -- ty1 is the *expected* type
+
-> TcTauType -> TcTauType -- Error reporting ty2 and real ty2
- -> TcM s ()
+ -- ty2 is the *actual* type
+ -> TcM ()
-- Always expand synonyms (see notes at end)
+ -- (this also throws away FTVs and usage annots)
uTys ps_ty1 (NoteTy _ ty1) ps_ty2 ty2 = uTys ps_ty1 ty1 ps_ty2 ty2
uTys ps_ty1 ty1 ps_ty2 (NoteTy _ ty2) = uTys ps_ty1 ty1 ps_ty2 ty2
uTys ps_ty1 ty1 ps_ty2 (TyVarTy tyvar2) = uVar True tyvar2 ps_ty1 ty1
-- "True" means args swapped
+ -- Predicates
+uTys _ (PredTy (IParam n1 t1)) _ (PredTy (IParam n2 t2))
+ | n1 == n2 = uTys t1 t1 t2 t2
+uTys _ (PredTy (Class c1 tys1)) _ (PredTy (Class c2 tys2))
+ | c1 == c2 = unifyTauTyLists tys1 tys2
+
-- Functions; just check the two parts
uTys _ (FunTy fun1 arg1) _ (FunTy fun2 arg2)
= uTys fun1 fun1 fun2 fun2 `thenTc_` uTys arg1 arg1 arg2 arg2
-- Type constructors must match
uTys ps_ty1 (TyConApp con1 tys1) ps_ty2 (TyConApp con2 tys2)
- = checkTcM (cons_match && length tys1 == length tys2)
- (failWithTcM (unifyMisMatch ps_ty1 ps_ty2)) `thenTc_`
- unifyTauTyLists tys1 tys2
- where
- -- The AnyBox wild card matches anything
- cons_match = con1 == con2
- || con1 == anyBoxCon
- || con2 == anyBoxCon
+ | con1 == con2 && length tys1 == length tys2
+ = unifyTauTyLists tys1 tys2
+
+ | con1 == openKindCon
+ -- When we are doing kind checking, we might match a kind '?'
+ -- against a kind '*' or '#'. Notably, CCallable :: ? -> *, and
+ -- (CCallable Int) and (CCallable Int#) are both OK
+ = unifyOpenTypeKind ps_ty2
-- Applications need a bit of care!
-- They can match FunTy and TyConApp, so use splitAppTy_maybe
uTys ps_ty1 (AppTy s1 t1) ps_ty2 ty2
= case splitAppTy_maybe ty2 of
Just (s2,t2) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
- Nothing -> failWithTcM (unifyMisMatch ps_ty1 ps_ty2)
+ Nothing -> unifyMisMatch ps_ty1 ps_ty2
-- Now the same, but the other way round
-- Don't swap the types, because the error messages get worse
uTys ps_ty1 ty1 ps_ty2 (AppTy s2 t2)
= case splitAppTy_maybe ty1 of
Just (s1,t1) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
- Nothing -> failWithTcM (unifyMisMatch ps_ty1 ps_ty2)
+ Nothing -> unifyMisMatch ps_ty1 ps_ty2
-- Not expecting for-alls in unification
-- ... but the error message from the unifyMisMatch more informative
-- than a panic message!
-- Anything else fails
-uTys ps_ty1 ty1 ps_ty2 ty2 = failWithTcM (unifyMisMatch ps_ty1 ps_ty2)
+uTys ps_ty1 ty1 ps_ty2 ty2 = unifyMisMatch ps_ty1 ps_ty2
\end{code}
Notes on synonyms
-- True => ty is the "expected" thing
-> TcTyVar
-> TcTauType -> TcTauType -- printing and real versions
- -> TcM s ()
+ -> TcM ()
uVar swapped tv1 ps_ty2 ty2
= tcGetTyVar tv1 `thenNF_Tc` \ maybe_ty1 ->
| otherwise -> uTys ty1 ty1 ps_ty2 ty2 -- Same order
other -> uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2
- -- Expand synonyms
+ -- Expand synonyms; ignore FTVs; ignore usage annots
uUnboundVar swapped tv1 maybe_ty1 ps_ty2 (NoteTy _ ty2)
= uUnboundVar swapped tv1 maybe_ty1 ps_ty2 ty2
case maybe_ty2 of
Just ty2' -> uUnboundVar swapped tv1 maybe_ty1 ty2' ty2'
- Nothing -> checkKinds swapped tv1 ty2 `thenTc_`
+ Nothing | tv1_dominates_tv2
- -- Try to update sys-y type variables in preference to sig-y ones
- -- (the latter respond False to isSysLocalName)
- if isSysLocalName (varName tv2) then
- tcPutTyVar tv2 (TyVarTy tv1) `thenNF_Tc_`
- returnTc ()
- else
- tcPutTyVar tv1 ps_ty2 `thenNF_Tc_`
- returnTc ()
+ -> WARN( not (k1 `hasMoreBoxityInfo` k2), (ppr tv1 <+> ppr k1) $$ (ppr tv2 <+> ppr k2) )
+ tcPutTyVar tv2 (TyVarTy tv1) `thenNF_Tc_`
+ returnTc ()
+ | otherwise
+
+ -> WARN( not (k2 `hasMoreBoxityInfo` k1), (ppr tv2 <+> ppr k2) $$ (ppr tv1 <+> ppr k1) )
+ (ASSERT( isNotUsgTy ps_ty2 )
+ tcPutTyVar tv1 ps_ty2 `thenNF_Tc_`
+ returnTc ())
+ where
+ k1 = tyVarKind tv1
+ k2 = tyVarKind tv2
+ tv1_dominates_tv2 = isSigTyVar tv1
+ -- Don't unify a signature type variable if poss
+ || k2 == openTypeKind
+ -- Try to get rid of open type variables as soon as poss
+ || isSystemName (varName tv2)
+ -- Try to update sys-y type variables in preference to sig-y ones
-- Second one isn't a type variable
uUnboundVar swapped tv1 maybe_ty1 ps_ty2 non_var_ty2
- | non_var_ty2 == anyBoxKind
- -- If the
- = returnTc ()
+ = checkKinds swapped tv1 non_var_ty2 `thenTc_`
+ occur_check non_var_ty2 `thenTc_`
+ ASSERT( isNotUsgTy ps_ty2 )
+ checkTcM (not (isSigTyVar tv1))
+ (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenTc_`
+
+ warnTc (not (typeKind non_var_ty2 `hasMoreBoxityInfo` tyVarKind tv1))
+ ((ppr tv1 <+> ppr (tyVarKind tv1)) $$
+ (ppr non_var_ty2 <+> ppr (typeKind non_var_ty2))) `thenNF_Tc_`
+
+ tcPutTyVar tv1 non_var_ty2 `thenNF_Tc_`
+ -- This used to say "ps_ty2" instead of "non_var_ty2"
+
+ -- But that led to an infinite loop in the type checker!
+ -- Consider
+ -- type A a = ()
+ --
+ -- f :: (A a -> a -> ()) -> ()
+ -- f = \ _ -> ()
+ --
+ -- x :: ()
+ -- x = f (\ x p -> p x)
+ --
+ -- Here, we try to match "t" with "A t", and succeed
+ -- because the unifier looks through synonyms. The occurs
+ -- check doesn't kick in because we are "really" binding "t" to "()",
+ -- but we *actually* bind "t" to "A t" if we store ps_ty2.
+ -- That leads the typechecker into an infinite loop later.
- | otherwise
- = checkKinds swapped tv1 non_var_ty2 `thenTc_`
- occur_check non_var_ty2 `thenTc_`
- tcPutTyVar tv1 ps_ty2 `thenNF_Tc_`
returnTc ()
where
occur_check ty = mapTc occur_check_tv (varSetElems (tyVarsOfType ty)) `thenTc_`
other -> returnTc ()
checkKinds swapped tv1 ty2
+-- We're about to unify a type variable tv1 with a non-tyvar-type ty2.
+-- We need to check that we don't unify a boxed type variable with an
+-- unboxed type: e.g. (id 3#) is illegal
+ | tk1 == boxedTypeKind && tk2 == unboxedTypeKind
= tcAddErrCtxtM (unifyKindCtxt swapped tv1 ty2) $
-
- -- We have to use tcTypeKind not just typeKind to get the
- -- kind of ty2, because there might be mutable kind variables
- -- in the way. For example, suppose that ty2 :: (a b), and
- -- the kind of 'a' is a kind variable 'k' that has (presumably)
- -- been unified with 'k1 -> k2'.
- tcTypeKind ty2 `thenNF_Tc` \ k2 ->
-
- if swapped then
- unifyKind k2 (tyVarKind tv1)
- else
- unifyKind (tyVarKind tv1) k2
+ unifyMisMatch k1 k2
+ | otherwise
+ = returnTc ()
+ where
+ (k1,k2) | swapped = (tk2,tk1)
+ | otherwise = (tk1,tk2)
+ tk1 = tyVarKind tv1
+ tk2 = typeKind ty2
\end{code}
+
%************************************************************************
%* *
\subsection[Unify-fun]{@unifyFunTy@}
\begin{code}
unifyFunTy :: TcType -- Fail if ty isn't a function type
- -> TcM s (TcType, TcType) -- otherwise return arg and result types
+ -> TcM (TcType, TcType) -- otherwise return arg and result types
unifyFunTy ty@(TyVarTy tyvar)
= tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty ->
Nothing -> unify_fun_ty_help ty
unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification
- = newTyVarTy_OpenKind `thenNF_Tc` \ arg ->
- newTyVarTy_OpenKind `thenNF_Tc` \ res ->
+ = newTyVarTy openTypeKind `thenNF_Tc` \ arg ->
+ newTyVarTy openTypeKind `thenNF_Tc` \ res ->
unifyTauTy ty (mkFunTy arg res) `thenTc_`
returnTc (arg,res)
\end{code}
\begin{code}
unifyListTy :: TcType -- expected list type
- -> TcM s TcType -- list element type
+ -> TcM TcType -- list element type
unifyListTy ty@(TyVarTy tyvar)
= tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty ->
\end{code}
\begin{code}
-unifyTupleTy :: Arity -> TcType -> TcM s [TcType]
-unifyTupleTy arity ty@(TyVarTy tyvar)
- = tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty' -> unifyTupleTy arity ty'
- other -> unify_tuple_ty_help arity ty
-
-unifyTupleTy arity ty
- = case splitTyConApp_maybe ty of
- Just (tycon, arg_tys) | isTupleTyCon tycon
- && tyConArity tycon == arity
- -> returnTc arg_tys
- other -> unify_tuple_ty_help arity ty
-
-unify_tuple_ty_help arity ty
- = mapNF_Tc (\ _ -> newTyVarTy boxedTypeKind) [1..arity] `thenNF_Tc` \ arg_tys ->
- unifyTauTy ty (mkTupleTy arity arg_tys) `thenTc_`
- returnTc arg_tys
-\end{code}
-
-\begin{code}
-unifyUnboxedTupleTy :: Arity -> TcType -> TcM s [TcType]
-unifyUnboxedTupleTy arity ty@(TyVarTy tyvar)
+unifyTupleTy :: Boxity -> Arity -> TcType -> TcM [TcType]
+unifyTupleTy boxity arity ty@(TyVarTy tyvar)
= tcGetTyVar tyvar `thenNF_Tc` \ maybe_ty ->
case maybe_ty of
- Just ty' -> unifyUnboxedTupleTy arity ty'
- other -> unify_unboxed_tuple_ty_help arity ty
+ Just ty' -> unifyTupleTy boxity arity ty'
+ other -> unify_tuple_ty_help boxity arity ty
-unifyUnboxedTupleTy arity ty
+unifyTupleTy boxity arity ty
= case splitTyConApp_maybe ty of
- Just (tycon, arg_tys) | isUnboxedTupleTyCon tycon
- && tyConArity tycon == arity
- -> returnTc arg_tys
- other -> unify_tuple_ty_help arity ty
-
-unify_unboxed_tuple_ty_help arity ty
- = mapNF_Tc (\ _ -> newTyVarTy_OpenKind) [1..arity] `thenNF_Tc` \ arg_tys ->
- unifyTauTy ty (mkUnboxedTupleTy arity arg_tys) `thenTc_`
+ Just (tycon, arg_tys)
+ | isTupleTyCon tycon
+ && tyConArity tycon == arity
+ && tupleTyConBoxity tycon == boxity
+ -> returnTc arg_tys
+ other -> unify_tuple_ty_help boxity arity ty
+
+unify_tuple_ty_help boxity arity ty
+ = newTyVarTys arity kind `thenNF_Tc` \ arg_tys ->
+ unifyTauTy ty (mkTupleTy boxity arity arg_tys) `thenTc_`
returnTc arg_tys
-\end{code}
-
-Make sure a kind is of the form (Type b) for some boxity b.
-
-\begin{code}
-unifyTypeKind :: TcKind -> TcM s ()
-unifyTypeKind kind@(TyVarTy kv)
- = tcGetTyVar kv `thenNF_Tc` \ maybe_kind ->
- case maybe_kind of
- Just kind' -> unifyTypeKind kind'
- Nothing -> unify_type_kind_help kind
-
-unifyTypeKind kind
- = case splitTyConApp_maybe kind of
- Just (tycon, [_]) | tycon == typeCon -> returnTc ()
- other -> unify_type_kind_help kind
-
-unify_type_kind_help kind
- = newOpenTypeKind `thenNF_Tc` \ expected_kind ->
- unifyKind expected_kind kind
+ where
+ kind | isBoxed boxity = boxedTypeKind
+ | otherwise = openTypeKind
\end{code}
(env1, [tidy_ty1,tidy_ty2]) = tidyOpenTypes tidy_env [ty1,ty2]
unifyKindCtxt swapped tv1 ty2 tidy_env -- not swapped => tv1 expected, ty2 inferred
- = returnNF_Tc (env2, ptext SLIT("When matching types") <+>
- sep [quotes pp_expected, ptext SLIT("and"), quotes pp_actual])
+ -- tv1 is zonked already
+ = zonkTcType ty2 `thenNF_Tc` \ ty2' ->
+ returnNF_Tc (err ty2')
where
- (pp_expected, pp_actual) | swapped = (pp2, pp1)
- | otherwise = (pp1, pp2)
- (env1, tv1') = tidyTyVar tidy_env tv1
- (env2, ty2') = tidyOpenType env1 ty2
- pp1 = ppr tv1'
- pp2 = ppr ty2'
+ err ty2 = (env2, ptext SLIT("When matching types") <+>
+ sep [quotes pp_expected, ptext SLIT("and"), quotes pp_actual])
+ where
+ (pp_expected, pp_actual) | swapped = (pp2, pp1)
+ | otherwise = (pp1, pp2)
+ (env1, tv1') = tidyTyVar tidy_env tv1
+ (env2, ty2') = tidyOpenType env1 ty2
+ pp1 = ppr tv1'
+ pp2 = ppr ty2'
unifyMisMatch ty1 ty2
- = (env2, hang (ptext SLIT("Couldn't match"))
- 4 (sep [quotes (ppr tidy_ty1), ptext SLIT("against"), quotes (ppr tidy_ty2)]))
+ = zonkTcType ty1 `thenNF_Tc` \ ty1' ->
+ zonkTcType ty2 `thenNF_Tc` \ ty2' ->
+ let
+ (env, [tidy_ty1, tidy_ty2]) = tidyOpenTypes emptyTidyEnv [ty1',ty2']
+ msg = hang (ptext SLIT("Couldn't match"))
+ 4 (sep [quotes (ppr tidy_ty1),
+ ptext SLIT("against"),
+ quotes (ppr tidy_ty2)])
+ in
+ failWithTcM (env, msg)
+
+unifyWithSigErr tyvar ty
+ = (env2, hang (ptext SLIT("Cannot unify the type-signature variable") <+> quotes (ppr tidy_tyvar))
+ 4 (ptext SLIT("with the type") <+> quotes (ppr tidy_ty)))
where
- (env1, tidy_ty1) = tidyOpenType emptyTidyEnv ty1
- (env2, tidy_ty2) = tidyOpenType env1 ty2
+ (env1, tidy_tyvar) = tidyTyVar emptyTidyEnv tyvar
+ (env2, tidy_ty) = tidyOpenType env1 ty
unifyOccurCheck tyvar ty
= (env2, hang (ptext SLIT("Occurs check: cannot construct the infinite type:"))
projects / ghc-hetmet.git / blobdiff