\begin{code}
module TcUnify (
-- Full-blown subsumption
- tcSub, tcGen, subFunTy,
- checkSigTyVars, sigCtxt, sigPatCtxt,
+ tcSubOff, tcSubExp, tcGen, subFunTy, TcHoleType,
+ checkSigTyVars, checkSigTyVarsWrt, sigCtxt, findGlobals,
-- Various unifications
unifyTauTy, unifyTauTyList, unifyTauTyLists,
- unifyFunTy, unifyListTy, unifyTupleTy,
- unifyKind, unifyKinds, unifyOpenTypeKind,
+ unifyFunTy, unifyListTy, unifyPArrTy, unifyTupleTy,
+ unifyKind, unifyKinds, unifyOpenTypeKind, unifyFunKind,
-- Coercions
Coercion, ExprCoFn, PatCoFn,
import HsSyn ( HsExpr(..) )
-import TcHsSyn ( TypecheckedHsExpr, TcPat,
- mkHsDictApp, mkHsTyApp, mkHsLet )
-import TypeRep ( Type(..), SourceType(..),
- openKindCon, typeCon )
-
-import TcMonad -- TcType, amongst others
-import TcType ( TcKind, TcType, TcSigmaType, TcPhiType, TcTyVar, TcTauType,
- TcTyVarSet, TcThetaType,
+import TcHsSyn ( TypecheckedHsExpr, TcPat, mkHsLet )
+import TypeRep ( Type(..), SourceType(..), TyNote(..), openKindCon )
+
+import TcRnMonad -- TcType, amongst others
+import TcType ( TcKind, TcType, TcSigmaType, TcRhoType, TcTyVar, TcTauType,
+ TcTyVarSet, TcThetaType, TyVarDetails(SigTv),
isTauTy, isSigmaTy,
tcSplitAppTy_maybe, tcSplitTyConApp_maybe,
tcGetTyVar_maybe, tcGetTyVar,
- mkTyConApp, mkTyVarTys, mkFunTy, tyVarsOfType, mkRhoTy,
+ mkTyConApp, mkFunTy, tyVarsOfType, mkPhiTy,
typeKind, tcSplitFunTy_maybe, mkForAllTys,
- isHoleTyVar, isSkolemTyVar, isUserTyVar, allDistinctTyVars,
+ isHoleTyVar, isSkolemTyVar, isUserTyVar,
tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars,
- eqKind, openTypeKind, liftedTypeKind, unliftedTypeKind, isTypeKind,
- hasMoreBoxityInfo, tyVarBindingInfo
+ eqKind, openTypeKind, liftedTypeKind, isTypeKind, mkArrowKind,
+ hasMoreBoxityInfo, allDistinctTyVars
)
import qualified Type ( getTyVar_maybe )
-import Inst ( LIE, emptyLIE, plusLIE, mkLIE,
- newDicts, instToId
- )
-import TcMType ( getTcTyVar, putTcTyVar, tcInstType,
- newTyVarTy, newTyVarTys, newBoxityVar, newHoleTyVarTy,
- zonkTcType, zonkTcTyVars, zonkTcTyVar )
+import Inst ( newDicts, instToId, tcInstCall )
+import TcMType ( getTcTyVar, putTcTyVar, tcInstType, readHoleResult, newKindVar,
+ newTyVarTy, newTyVarTys, newOpenTypeKind, newHoleTyVarTy,
+ zonkTcType, zonkTcTyVars, zonkTcTyVarsAndFV, zonkTcTyVar )
import TcSimplify ( tcSimplifyCheck )
-import TysWiredIn ( listTyCon, mkListTy, mkTupleTy )
-import TcEnv ( TcTyThing(..), tcExtendGlobalTyVars, tcGetGlobalTyVars, tcLEnvElts )
+import TysWiredIn ( listTyCon, parrTyCon, mkListTy, mkPArrTy, mkTupleTy )
+import TcEnv ( TcTyThing(..), tcGetGlobalTyVars, findGlobals )
import TyCon ( tyConArity, isTupleTyCon, tupleTyConBoxity )
import PprType ( pprType )
-import CoreFVs ( idFreeTyVars )
-import Id ( mkSysLocal, idType )
+import Id ( Id, mkSysLocal, idType )
import Var ( Var, varName, tyVarKind )
-import VarSet ( elemVarSet, varSetElems )
+import VarSet ( emptyVarSet, unitVarSet, unionVarSet, elemVarSet, varSetElems )
import VarEnv
import Name ( isSystemName, getSrcLoc )
import ErrUtils ( Message )
import BasicTypes ( Boxity, Arity, isBoxed )
-import Util ( isSingleton, equalLength )
+import Util ( equalLength, notNull )
import Maybe ( isNothing )
import Outputable
\end{code}
+Notes on holes
+~~~~~~~~~~~~~~
+* A hole is always filled in with an ordinary type, not another hole.
%************************************************************************
%* *
%* *
%************************************************************************
-\begin{code}
-tcSub :: TcSigmaType -- expected_ty; can be a type scheme;
- -- can be a "hole" type variable
- -> TcSigmaType -- actual_ty; can be a type scheme
- -> TcM (ExprCoFn, LIE)
-\end{code}
+All the tcSub calls have the form
+
+ tcSub expected_ty offered_ty
+which checks
+ offered_ty <= expected_ty
-(tcSub expected_ty actual_ty) checks that
- actual_ty <= expected_ty
-That is, that a value of type actual_ty is acceptable in
+That is, that a value of type offered_ty is acceptable in
a place expecting a value of type expected_ty.
It returns a coercion function
- co_fn :: actual_ty -> expected_ty
-which takes an HsExpr of type actual_ty into one of type
+ co_fn :: offered_ty -> expected_ty
+which takes an HsExpr of type offered_ty into one of type
expected_ty.
\begin{code}
+type TcHoleType = TcSigmaType -- Either a TcSigmaType,
+ -- or else a hole
+
+tcSubExp :: TcHoleType -> TcSigmaType -> TcM ExprCoFn
+tcSubOff :: TcSigmaType -> TcHoleType -> TcM ExprCoFn
+tcSub :: TcSigmaType -> TcSigmaType -> TcM ExprCoFn
+\end{code}
+
+These two check for holes
+
+\begin{code}
+tcSubExp expected_ty offered_ty
+ = traceTc (text "tcSubExp" <+> (ppr expected_ty $$ ppr offered_ty)) `thenM_`
+ checkHole expected_ty offered_ty tcSub
+
+tcSubOff expected_ty offered_ty
+ = checkHole offered_ty expected_ty (\ off exp -> tcSub exp off)
+
+-- checkHole looks for a hole in its first arg;
+-- If so, and it is uninstantiated, it fills in the hole
+-- with its second arg
+-- Otherwise it calls thing_inside, passing the two args, looking
+-- through any instantiated hole
+
+checkHole (TyVarTy tv) other_ty thing_inside
+ | isHoleTyVar tv
+ = getTcTyVar tv `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty -> thing_inside ty other_ty
+ Nothing -> traceTc (text "checkHole" <+> ppr tv) `thenM_`
+ putTcTyVar tv other_ty `thenM_`
+ returnM idCoercion
+
+checkHole ty other_ty thing_inside
+ = thing_inside ty other_ty
+\end{code}
+
+No holes expected now. Add some error-check context info.
+
+\begin{code}
tcSub expected_ty actual_ty
- = traceTc (text "tcSub" <+> details) `thenNF_Tc_`
- tcAddErrCtxtM (unifyCtxt "type" expected_ty actual_ty)
- (tc_sub expected_ty expected_ty actual_ty actual_ty)
+ = traceTc (text "tcSub" <+> details) `thenM_`
+ addErrCtxtM (unifyCtxt "type" expected_ty actual_ty)
+ (tc_sub expected_ty expected_ty actual_ty actual_ty)
where
details = vcat [text "Expected:" <+> ppr expected_ty,
text "Actual: " <+> ppr actual_ty]
-> TcSigmaType -- ..and after
-> TcSigmaType -- actual_ty, before
-> TcSigmaType -- ..and after
- -> TcM (ExprCoFn, LIE)
+ -> TcM ExprCoFn
-----------------------------------
-- Expand synonyms
tc_sub exp_sty exp_ty act_sty (NoteTy _ act_ty) = tc_sub exp_sty exp_ty act_sty act_ty
-----------------------------------
--- "Hole type variable" case
--- Do this case before unwrapping for-alls in the actual_ty
-
-tc_sub _ (TyVarTy tv) act_sty act_ty
- | isHoleTyVar tv
- = -- It's a "hole" type variable
- getTcTyVar tv `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
-
- Just ty -> -- Already been assigned
- tc_sub ty ty act_sty act_ty ;
-
- Nothing -> -- Assign it
- putTcTyVar tv act_sty `thenNF_Tc_`
- returnTc (idCoercion, emptyLIE)
-
-
------------------------------------
-- Generalisation case
-- actual_ty: d:Eq b => b->b
-- expected_ty: forall a. Ord a => a->a
tc_sub exp_sty expected_ty act_sty actual_ty
| isSigmaTy expected_ty
- = tcGen expected_ty (
+ = tcGen expected_ty (tyVarsOfType actual_ty) (
+ -- It's really important to check for escape wrt the free vars of
+ -- both expected_ty *and* actual_ty
\ body_exp_ty -> tc_sub body_exp_ty body_exp_ty act_sty actual_ty
- ) `thenTc` \ (gen_fn, co_fn, lie) ->
- returnTc (gen_fn <.> co_fn, lie)
+ ) `thenM` \ (gen_fn, co_fn) ->
+ returnM (gen_fn <.> co_fn)
-----------------------------------
-- Specialisation case:
tc_sub exp_sty expected_ty act_sty actual_ty
| isSigmaTy actual_ty
- = tcInstType actual_ty `thenNF_Tc` \ (tvs, theta, body_ty) ->
- newDicts orig theta `thenNF_Tc` \ dicts ->
- let
- inst_fn e = mkHsDictApp (mkHsTyApp e (mkTyVarTys tvs))
- (map instToId dicts)
- in
- tc_sub exp_sty expected_ty body_ty body_ty `thenTc` \ (co_fn, lie) ->
- returnTc (co_fn <.> mkCoercion inst_fn, lie `plusLIE` mkLIE dicts)
- where
- orig = Rank2Origin
+ = tcInstCall Rank2Origin actual_ty `thenM` \ (inst_fn, body_ty) ->
+ tc_sub exp_sty expected_ty body_ty body_ty `thenM` \ co_fn ->
+ returnM (co_fn <.> mkCoercion inst_fn)
-----------------------------------
-- Function case
-- when the arg/res is not a tau-type?
-- NO! e.g. f :: ((forall a. a->a) -> Int) -> Int
-- then x = (f,f)
--- is perfectly fine!
+-- is perfectly fine, because we can instantiat f's type to a monotype
+--
+-- However, we get can get jolly unhelpful error messages.
+-- e.g. foo = id runST
+--
+-- Inferred type is less polymorphic than expected
+-- Quantified type variable `s' escapes
+-- Expected type: ST s a -> t
+-- Inferred type: (forall s1. ST s1 a) -> a
+-- In the first argument of `id', namely `runST'
+-- In a right-hand side of function `foo': id runST
+--
+-- I'm not quite sure what to do about this!
tc_sub exp_sty exp_ty@(FunTy exp_arg exp_res) _ (TyVarTy tv)
- = getTcTyVar tv `thenNF_Tc` \ maybe_ty ->
+ = ASSERT( not (isHoleTyVar tv) )
+ getTcTyVar tv `thenM` \ maybe_ty ->
case maybe_ty of
Just ty -> tc_sub exp_sty exp_ty ty ty
- Nothing -> imitateFun tv exp_sty `thenNF_Tc` \ (act_arg, act_res) ->
+ Nothing -> imitateFun tv exp_sty `thenM` \ (act_arg, act_res) ->
tcSub_fun exp_arg exp_res act_arg act_res
tc_sub _ (TyVarTy tv) act_sty act_ty@(FunTy act_arg act_res)
- = getTcTyVar tv `thenNF_Tc` \ maybe_ty ->
+ = ASSERT( not (isHoleTyVar tv) )
+ getTcTyVar tv `thenM` \ maybe_ty ->
case maybe_ty of
Just ty -> tc_sub ty ty act_sty act_ty
- Nothing -> imitateFun tv act_sty `thenNF_Tc` \ (exp_arg, exp_res) ->
+ Nothing -> imitateFun tv act_sty `thenM` \ (exp_arg, exp_res) ->
tcSub_fun exp_arg exp_res act_arg act_res
-----------------------------------
-- Unification case
-- If none of the above match, we revert to the plain unifier
tc_sub exp_sty expected_ty act_sty actual_ty
- = uTys exp_sty expected_ty act_sty actual_ty `thenTc_`
- returnTc (idCoercion, emptyLIE)
+ = uTys exp_sty expected_ty act_sty actual_ty `thenM_`
+ returnM idCoercion
\end{code}
%************************************************************************
\begin{code}
tcSub_fun exp_arg exp_res act_arg act_res
- = tcSub act_arg exp_arg `thenTc` \ (co_fn_arg, lie1) ->
- tcSub exp_res act_res `thenTc` \ (co_fn_res, lie2) ->
- tcGetUnique `thenNF_Tc` \ uniq ->
+ = tc_sub act_arg act_arg exp_arg exp_arg `thenM` \ co_fn_arg ->
+ tc_sub exp_res exp_res act_res act_res `thenM` \ co_fn_res ->
+ newUnique `thenM` \ uniq ->
let
-- co_fn_arg :: HsExpr exp_arg -> HsExpr act_arg
-- co_fn_res :: HsExpr act_res -> HsExpr exp_res
-- co_fn :: HsExpr (act_arg -> act_res) -> HsExpr (exp_arg -> exp_res)
- arg_id = mkSysLocal SLIT("sub") uniq exp_arg
+ arg_id = mkSysLocal FSLIT("sub") uniq exp_arg
coercion | isIdCoercion co_fn_arg,
isIdCoercion co_fn_res = idCoercion
| otherwise = mkCoercion co_fn
-- HsApp e $it :: HsExpr act_res
-- co_fn_res $it :: HsExpr exp_res
in
- returnTc (coercion, lie1 `plusLIE` lie2)
+ returnM coercion
-imitateFun :: TcTyVar -> TcType -> NF_TcM (TcType, TcType)
+imitateFun :: TcTyVar -> TcType -> TcM (TcType, TcType)
imitateFun tv ty
= ASSERT( not (isHoleTyVar tv) )
-- NB: tv is an *ordinary* tyvar and so are the new ones
-- Check that tv isn't a type-signature type variable
-- (This would be found later in checkSigTyVars, but
-- we get a better error message if we do it here.)
- checkTcM (not (isSkolemTyVar tv))
- (failWithTcM (unifyWithSigErr tv ty)) `thenTc_`
+ checkM (not (isSkolemTyVar tv))
+ (failWithTcM (unifyWithSigErr tv ty)) `thenM_`
- newTyVarTy openTypeKind `thenNF_Tc` \ arg ->
- newTyVarTy openTypeKind `thenNF_Tc` \ res ->
- putTcTyVar tv (mkFunTy arg res) `thenNF_Tc_`
- returnNF_Tc (arg,res)
+ newTyVarTy openTypeKind `thenM` \ arg ->
+ newTyVarTy openTypeKind `thenM` \ res ->
+ putTcTyVar tv (mkFunTy arg res) `thenM_`
+ returnM (arg,res)
\end{code}
\begin{code}
tcGen :: TcSigmaType -- expected_ty
- -> (TcPhiType -> TcM (result, LIE)) -- spec_ty
- -> TcM (ExprCoFn, result, LIE)
+ -> TcTyVarSet -- Extra tyvars that the universally
+ -- quantified tyvars of expected_ty
+ -- must not be unified
+ -> (TcRhoType -> TcM result) -- spec_ty
+ -> TcM (ExprCoFn, result)
-- The expression has type: spec_ty -> expected_ty
-tcGen expected_ty thing_inside -- We expect expected_ty to be a forall-type
- -- If not, the call is a no-op
- = tcInstType expected_ty `thenNF_Tc` \ (forall_tvs, theta, phi_ty) ->
+tcGen expected_ty extra_tvs thing_inside -- We expect expected_ty to be a forall-type
+ -- If not, the call is a no-op
+ = tcInstType SigTv expected_ty `thenM` \ (forall_tvs, theta, phi_ty) ->
-- Type-check the arg and unify with poly type
- thing_inside phi_ty `thenTc` \ (result, lie) ->
+ getLIE (thing_inside phi_ty) `thenM` \ (result, lie) ->
-- Check that the "forall_tvs" havn't been constrained
-- The interesting bit here is that we must include the free variables
-- Conclusion: include the free vars of the expected_ty in the
-- list of "free vars" for the signature check.
- tcExtendGlobalTyVars free_tvs $
- tcAddErrCtxtM (sigCtxt forall_tvs theta phi_ty) $
+ newDicts SignatureOrigin theta `thenM` \ dicts ->
+ tcSimplifyCheck sig_msg forall_tvs dicts lie `thenM` \ inst_binds ->
+
+#ifdef DEBUG
+ zonkTcTyVars forall_tvs `thenM` \ forall_tys ->
+ traceTc (text "tcGen" <+> vcat [text "extra_tvs" <+> ppr extra_tvs,
+ text "expected_ty" <+> ppr expected_ty,
+ text "inst ty" <+> ppr forall_tvs <+> ppr theta <+> ppr phi_ty,
+ text "free_tvs" <+> ppr free_tvs,
+ text "forall_tys" <+> ppr forall_tys]) `thenM_`
+#endif
+
+ checkSigTyVarsWrt free_tvs forall_tvs `thenM` \ zonked_tvs ->
- newDicts SignatureOrigin theta `thenNF_Tc` \ dicts ->
- tcSimplifyCheck sig_msg forall_tvs dicts lie `thenTc` \ (free_lie, inst_binds) ->
- checkSigTyVars forall_tvs free_tvs `thenTc` \ zonked_tvs ->
+ traceTc (text "tcGen:done") `thenM_`
let
-- This HsLet binds any Insts which came out of the simplification.
dict_ids = map instToId dicts
co_fn e = TyLam zonked_tvs (DictLam dict_ids (mkHsLet inst_binds e))
in
- returnTc (mkCoercion co_fn, result, free_lie)
+ returnM (mkCoercion co_fn, result)
where
- free_tvs = tyVarsOfType expected_ty
- sig_msg = ptext SLIT("When generalising the type of an expression")
+ free_tvs = tyVarsOfType expected_ty `unionVarSet` extra_tvs
+ sig_msg = ptext SLIT("expected type of an expression")
\end{code}
-- (no quantification whatsoever)
ASSERT2( isTauTy ty1, ppr ty1 )
ASSERT2( isTauTy ty2, ppr ty2 )
- tcAddErrCtxtM (unifyCtxt "type" ty1 ty2) $
+ addErrCtxtM (unifyCtxt "type" ty1 ty2) $
uTys ty1 ty1 ty2 ty2
\end{code}
\begin{code}
unifyTauTyLists :: [TcTauType] -> [TcTauType] -> TcM ()
-unifyTauTyLists [] [] = returnTc ()
-unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenTc_`
+unifyTauTyLists [] [] = returnM ()
+unifyTauTyLists (ty1:tys1) (ty2:tys2) = uTys ty1 ty1 ty2 ty2 `thenM_`
unifyTauTyLists tys1 tys2
unifyTauTyLists ty1s ty2s = panic "Unify.unifyTauTyLists: mismatched type lists!"
\end{code}
\begin{code}
unifyTauTyList :: [TcTauType] -> TcM ()
-unifyTauTyList [] = returnTc ()
-unifyTauTyList [ty] = returnTc ()
-unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenTc_`
+unifyTauTyList [] = returnM ()
+unifyTauTyList [ty] = returnM ()
+unifyTauTyList (ty1:tys@(ty2:_)) = unifyTauTy ty1 ty2 `thenM_`
unifyTauTyList tys
\end{code}
uTys ps_ty1 (NoteTy n1 ty1) ps_ty2 ty2 = uTys ps_ty1 ty1 ps_ty2 ty2
uTys ps_ty1 ty1 ps_ty2 (NoteTy n2 ty2) = uTys ps_ty1 ty1 ps_ty2 ty2
- -- Ignore usage annotations inside typechecker
-uTys ps_ty1 (UsageTy _ ty1) ps_ty2 ty2 = uTys ps_ty1 ty1 ps_ty2 ty2
-uTys ps_ty1 ty1 ps_ty2 (UsageTy _ ty2) = uTys ps_ty1 ty1 ps_ty2 ty2
-
-- Variables; go for uVar
uTys ps_ty1 (TyVarTy tyvar1) ps_ty2 ty2 = uVar False tyvar1 ps_ty2 ty2
uTys ps_ty1 ty1 ps_ty2 (TyVarTy tyvar2) = uVar True tyvar2 ps_ty1 ty1
-- Functions; just check the two parts
uTys _ (FunTy fun1 arg1) _ (FunTy fun2 arg2)
- = uTys fun1 fun1 fun2 fun2 `thenTc_` uTys arg1 arg1 arg2 arg2
+ = uTys fun1 fun1 fun2 fun2 `thenM_` uTys arg1 arg1 arg2 arg2
-- Type constructors must match
uTys ps_ty1 (TyConApp con1 tys1) ps_ty2 (TyConApp con2 tys2)
-- so if one type is an App the other one jolly well better be too
uTys ps_ty1 (AppTy s1 t1) ps_ty2 ty2
= case tcSplitAppTy_maybe ty2 of
- Just (s2,t2) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
+ Just (s2,t2) -> uTys s1 s1 s2 s2 `thenM_` uTys t1 t1 t2 t2
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 tcSplitAppTy_maybe ty1 of
- Just (s1,t1) -> uTys s1 s1 s2 s2 `thenTc_` uTys t1 t1 t2 t2
+ Just (s1,t1) -> uTys s1 s1 s2 s2 `thenM_` uTys t1 t1 t2 t2
Nothing -> unifyMisMatch ps_ty1 ps_ty2
-- Not expecting for-alls in unification
-> TcM ()
uVar swapped tv1 ps_ty2 ty2
- = traceTc (text "uVar" <+> ppr swapped <+> ppr tv1 <+> (ppr ps_ty2 $$ ppr ty2)) `thenNF_Tc_`
- getTcTyVar tv1 `thenNF_Tc` \ maybe_ty1 ->
+ = traceTc (text "uVar" <+> ppr swapped <+> ppr tv1 <+> (ppr ps_ty2 $$ ppr ty2)) `thenM_`
+ getTcTyVar tv1 `thenM` \ maybe_ty1 ->
case maybe_ty1 of
Just ty1 | swapped -> uTys ps_ty2 ty2 ty1 ty1 -- Swap back
| otherwise -> uTys ty1 ty1 ps_ty2 ty2 -- Same order
-- Same type variable => no-op
| tv1 == tv2
- = returnTc ()
+ = returnM ()
-- Distinct type variables
-- ASSERT maybe_ty1 /= Just
| otherwise
- = getTcTyVar tv2 `thenNF_Tc` \ maybe_ty2 ->
+ = getTcTyVar tv2 `thenM` \ maybe_ty2 ->
case maybe_ty2 of
Just ty2' -> uUnboundVar swapped tv1 maybe_ty1 ty2' ty2'
Nothing | update_tv2
-> WARN( not (k1 `hasMoreBoxityInfo` k2), (ppr tv1 <+> ppr k1) $$ (ppr tv2 <+> ppr k2) )
- putTcTyVar tv2 (TyVarTy tv1) `thenNF_Tc_`
- returnTc ()
+ putTcTyVar tv2 (TyVarTy tv1) `thenM_`
+ returnM ()
| otherwise
-> WARN( not (k2 `hasMoreBoxityInfo` k1), (ppr tv2 <+> ppr k2) $$ (ppr tv1 <+> ppr k1) )
- putTcTyVar tv1 ps_ty2 `thenNF_Tc_`
- returnTc ()
+ putTcTyVar tv1 ps_ty2 `thenM_`
+ returnM ()
where
k1 = tyVarKind tv1
k2 = tyVarKind tv2
-- Second one isn't a type variable
uUnboundVar swapped tv1 maybe_ty1 ps_ty2 non_var_ty2
= -- Check that tv1 isn't a type-signature type variable
- checkTcM (not (isSkolemTyVar tv1))
- (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenTc_`
+ checkM (not (isSkolemTyVar tv1))
+ (failWithTcM (unifyWithSigErr tv1 ps_ty2)) `thenM_`
+
+ -- Do the occurs check, and check that we are not
+ -- unifying a type variable with a polytype
+ -- Returns a zonked type ready for the update
+ checkValue tv1 ps_ty2 non_var_ty2 `thenM` \ ty2 ->
-- Check that the kinds match
- zonkTcType ps_ty2 `thenNF_Tc` \ ps_ty2' ->
- checkKinds swapped tv1 ps_ty2' `thenTc_`
-
- -- Occurs check
- -- Basically we want to update tv1 := ps_ty2
- -- because ps_ty2 has type-synonym info, which improves later error messages
- --
- -- But consider
- -- type A a = ()
- --
- -- f :: (A a -> a -> ()) -> ()
- -- f = \ _ -> ()
- --
- -- x :: ()
- -- x = f (\ x p -> p x)
- --
- -- In the application (p x), we try to match "t" with "A t". If we go
- -- ahead and bind t to A t (= ps_ty2), we'll lead the type checker into
- -- an infinite loop later.
- -- But we should not reject the program, because A t = ().
- -- Rather, we should bind t to () (= non_var_ty2).
- --
- -- That's why we have this two-state occurs-check
- if not (tv1 `elemVarSet` tyVarsOfType ps_ty2') then
- putTcTyVar tv1 ps_ty2' `thenNF_Tc_`
- returnTc ()
- else
- zonkTcType non_var_ty2 `thenNF_Tc` \ non_var_ty2' ->
- if not (tv1 `elemVarSet` tyVarsOfType non_var_ty2') then
- -- This branch rarely succeeds, except in strange cases
- -- like that in the example above
- putTcTyVar tv1 non_var_ty2' `thenNF_Tc_`
- returnTc ()
- else
- failWithTcM (unifyOccurCheck tv1 ps_ty2')
+ checkKinds swapped tv1 ty2 `thenM_`
+ -- Perform the update
+ putTcTyVar tv1 ty2 `thenM_`
+ returnM ()
+\end{code}
+\begin{code}
checkKinds swapped tv1 ty2
-- We're about to unify a type variable tv1 with a non-tyvar-type ty2.
--- ty2 has been zonked at this stage
+-- ty2 has been zonked at this stage, which ensures that
+-- its kind has as much boxity information visible as possible.
+ | tk2 `hasMoreBoxityInfo` tk1 = returnM ()
- | tk1 `eqKind` liftedTypeKind && tk2 `eqKind` unliftedTypeKind
- -- Check that we don't unify a lifted type variable with an
- -- unlifted type: e.g. (id 3#) is illegal
- = tcAddErrCtxtM (unifyKindCtxt swapped tv1 ty2) $
+ | otherwise
+ -- Either the kinds aren't compatible
+ -- (can happen if we unify (a b) with (c d))
+ -- or we are unifying a lifted type variable with an
+ -- unlifted type: e.g. (id 3#) is illegal
+ = addErrCtxtM (unifyKindCtxt swapped tv1 ty2) $
unifyMisMatch k1 k2
- | otherwise
- = -- Check that we aren't losing boxity info (shouldn't happen)
- WARN (not (tk2 `hasMoreBoxityInfo` tk1),
- (ppr tv1 <+> ppr tk1) $$ (ppr ty2 <+> ppr tk2))
- returnTc ()
where
(k1,k2) | swapped = (tk2,tk1)
| otherwise = (tk1,tk2)
tk2 = typeKind ty2
\end{code}
+\begin{code}
+checkValue tv1 ps_ty2 non_var_ty2
+-- Do the occurs check, and check that we are not
+-- unifying a type variable with a polytype
+-- Return the type to update the type variable with, or fail
+
+-- Basically we want to update tv1 := ps_ty2
+-- because ps_ty2 has type-synonym info, which improves later error messages
+--
+-- But consider
+-- type A a = ()
+--
+-- f :: (A a -> a -> ()) -> ()
+-- f = \ _ -> ()
+--
+-- x :: ()
+-- x = f (\ x p -> p x)
+--
+-- In the application (p x), we try to match "t" with "A t". If we go
+-- ahead and bind t to A t (= ps_ty2), we'll lead the type checker into
+-- an infinite loop later.
+-- But we should not reject the program, because A t = ().
+-- Rather, we should bind t to () (= non_var_ty2).
+--
+-- That's why we have this two-state occurs-check
+ = zonkTcType ps_ty2 `thenM` \ ps_ty2' ->
+ case okToUnifyWith tv1 ps_ty2' of {
+ Nothing -> returnM ps_ty2' ; -- Success
+ other ->
+
+ zonkTcType non_var_ty2 `thenM` \ non_var_ty2' ->
+ case okToUnifyWith tv1 non_var_ty2' of
+ Nothing -> -- This branch rarely succeeds, except in strange cases
+ -- like that in the example above
+ returnM non_var_ty2'
+
+ Just problem -> failWithTcM (unifyCheck problem tv1 ps_ty2')
+ }
+
+data Problem = OccurCheck | NotMonoType
+
+okToUnifyWith :: TcTyVar -> TcType -> Maybe Problem
+-- (okToUnifyWith tv ty) checks whether it's ok to unify
+-- tv :=: ty
+-- Nothing => ok
+-- Just p => not ok, problem p
+
+okToUnifyWith tv ty
+ = ok ty
+ where
+ ok (TyVarTy tv') | tv == tv' = Just OccurCheck
+ | otherwise = Nothing
+ ok (AppTy t1 t2) = ok t1 `and` ok t2
+ ok (FunTy t1 t2) = ok t1 `and` ok t2
+ ok (TyConApp _ ts) = oks ts
+ ok (ForAllTy _ _) = Just NotMonoType
+ ok (SourceTy st) = ok_st st
+ ok (NoteTy (FTVNote _) t) = ok t
+ ok (NoteTy (SynNote t1) t2) = ok t1 `and` ok t2
+ -- Type variables may be free in t1 but not t2
+ -- A forall may be in t2 but not t1
+
+ oks ts = foldr (and . ok) Nothing ts
+
+ ok_st (ClassP _ ts) = oks ts
+ ok_st (IParam _ t) = ok t
+ ok_st (NType _ ts) = oks ts
+
+ Nothing `and` m = m
+ Just p `and` m = Just p
+\end{code}
%************************************************************************
%* *
type variables, so we should create new ordinary type variables
\begin{code}
-subFunTy :: TcSigmaType -- Fail if ty isn't a function type
- -> TcM (TcType, TcType) -- otherwise return arg and result types
-subFunTy ty@(TyVarTy tyvar)
-
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
- case maybe_ty of
- Just ty -> subFunTy ty
- Nothing | isHoleTyVar tyvar
- -> newHoleTyVarTy `thenNF_Tc` \ arg ->
- newHoleTyVarTy `thenNF_Tc` \ res ->
- putTcTyVar tyvar (mkFunTy arg res) `thenNF_Tc_`
- returnTc (arg,res)
- | otherwise
- -> unify_fun_ty_help ty
-
-subFunTy ty
- = case tcSplitFunTy_maybe ty of
- Just arg_and_res -> returnTc arg_and_res
- Nothing -> unify_fun_ty_help ty
+subFunTy :: TcHoleType -- Fail if ty isn't a function type
+ -- If it's a hole, make two holes, feed them to...
+ -> (TcHoleType -> TcHoleType -> TcM a) -- the thing inside
+ -> TcM a -- and bind the function type to the hole
+
+subFunTy ty@(TyVarTy tyvar) thing_inside
+ | isHoleTyVar tyvar
+ = -- This is the interesting case
+ getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of {
+ Just ty' -> subFunTy ty' thing_inside ;
+ Nothing ->
+
+ newHoleTyVarTy `thenM` \ arg_ty ->
+ newHoleTyVarTy `thenM` \ res_ty ->
+
+ -- Do the business
+ thing_inside arg_ty res_ty `thenM` \ answer ->
+
+ -- Extract the answers
+ readHoleResult arg_ty `thenM` \ arg_ty' ->
+ readHoleResult res_ty `thenM` \ res_ty' ->
+
+ -- Write the answer into the incoming hole
+ putTcTyVar tyvar (mkFunTy arg_ty' res_ty') `thenM_`
+
+ -- And return the answer
+ returnM answer }
+
+subFunTy ty thing_inside
+ = unifyFunTy ty `thenM` \ (arg,res) ->
+ thing_inside arg res
-unifyFunTy :: TcPhiType -- Fail if ty isn't a function type
+unifyFunTy :: TcRhoType -- Fail if ty isn't a function type
-> TcM (TcType, TcType) -- otherwise return arg and result types
unifyFunTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = ASSERT( not (isHoleTyVar tyvar) )
+ getTcTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty' -> unifyFunTy ty'
Nothing -> unify_fun_ty_help ty
unifyFunTy ty
= case tcSplitFunTy_maybe ty of
- Just arg_and_res -> returnTc arg_and_res
+ Just arg_and_res -> returnM arg_and_res
Nothing -> unify_fun_ty_help ty
unify_fun_ty_help ty -- Special cases failed, so revert to ordinary unification
- = newTyVarTy openTypeKind `thenNF_Tc` \ arg ->
- newTyVarTy openTypeKind `thenNF_Tc` \ res ->
- unifyTauTy ty (mkFunTy arg res) `thenTc_`
- returnTc (arg,res)
+ = newTyVarTy openTypeKind `thenM` \ arg ->
+ newTyVarTy openTypeKind `thenM` \ res ->
+ unifyTauTy ty (mkFunTy arg res) `thenM_`
+ returnM (arg,res)
\end{code}
\begin{code}
-> TcM TcType -- list element type
unifyListTy ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty' -> unifyListTy ty'
other -> unify_list_ty_help ty
unifyListTy ty
= case tcSplitTyConApp_maybe ty of
- Just (tycon, [arg_ty]) | tycon == listTyCon -> returnTc arg_ty
+ Just (tycon, [arg_ty]) | tycon == listTyCon -> returnM arg_ty
other -> unify_list_ty_help ty
unify_list_ty_help ty -- Revert to ordinary unification
- = newTyVarTy liftedTypeKind `thenNF_Tc` \ elt_ty ->
- unifyTauTy ty (mkListTy elt_ty) `thenTc_`
- returnTc elt_ty
+ = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy ty (mkListTy elt_ty) `thenM_`
+ returnM elt_ty
+
+-- variant for parallel arrays
+--
+unifyPArrTy :: TcType -- expected list type
+ -> TcM TcType -- list element type
+
+unifyPArrTy ty@(TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just ty' -> unifyPArrTy ty'
+ _ -> unify_parr_ty_help ty
+unifyPArrTy ty
+ = case tcSplitTyConApp_maybe ty of
+ Just (tycon, [arg_ty]) | tycon == parrTyCon -> returnM arg_ty
+ _ -> unify_parr_ty_help ty
+
+unify_parr_ty_help ty -- Revert to ordinary unification
+ = newTyVarTy liftedTypeKind `thenM` \ elt_ty ->
+ unifyTauTy ty (mkPArrTy elt_ty) `thenM_`
+ returnM elt_ty
\end{code}
\begin{code}
unifyTupleTy :: Boxity -> Arity -> TcType -> TcM [TcType]
unifyTupleTy boxity arity ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty' -> unifyTupleTy boxity arity ty'
other -> unify_tuple_ty_help boxity arity ty
| isTupleTyCon tycon
&& tyConArity tycon == arity
&& tupleTyConBoxity tycon == boxity
- -> returnTc arg_tys
+ -> returnM 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
+ = newTyVarTys arity kind `thenM` \ arg_tys ->
+ unifyTauTy ty (mkTupleTy boxity arity arg_tys) `thenM_`
+ returnM arg_tys
where
kind | isBoxed boxity = liftedTypeKind
| otherwise = openTypeKind
unifyKind :: TcKind -- Expected
-> TcKind -- Actual
-> TcM ()
-unifyKind k1 k2
- = tcAddErrCtxtM (unifyCtxt "kind" k1 k2) $
- uTys k1 k1 k2 k2
+unifyKind k1 k2 = uTys k1 k1 k2 k2
unifyKinds :: [TcKind] -> [TcKind] -> TcM ()
-unifyKinds [] [] = returnTc ()
-unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenTc_`
+unifyKinds [] [] = returnM ()
+unifyKinds (k1:ks1) (k2:ks2) = unifyKind k1 k2 `thenM_`
unifyKinds ks1 ks2
unifyKinds _ _ = panic "unifyKinds: length mis-match"
\end{code}
-- for some boxity bx
unifyOpenTypeKind ty@(TyVarTy tyvar)
- = getTcTyVar tyvar `thenNF_Tc` \ maybe_ty ->
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
case maybe_ty of
Just ty' -> unifyOpenTypeKind ty'
other -> unify_open_kind_help ty
unifyOpenTypeKind ty
- | isTypeKind ty = returnTc ()
+ | isTypeKind ty = returnM ()
| otherwise = unify_open_kind_help ty
unify_open_kind_help ty -- Revert to ordinary unification
- = newBoxityVar `thenNF_Tc` \ boxity ->
- unifyKind ty (mkTyConApp typeCon [boxity])
+ = newOpenTypeKind `thenM` \ open_kind ->
+ unifyKind ty open_kind
\end{code}
+\begin{code}
+unifyFunKind :: TcKind -> TcM (Maybe (TcKind, TcKind))
+-- Like unifyFunTy, but does not fail; instead just returns Nothing
+
+unifyFunKind (TyVarTy tyvar)
+ = getTcTyVar tyvar `thenM` \ maybe_ty ->
+ case maybe_ty of
+ Just fun_kind -> unifyFunKind fun_kind
+ Nothing -> newKindVar `thenM` \ arg_kind ->
+ newKindVar `thenM` \ res_kind ->
+ putTcTyVar tyvar (mkArrowKind arg_kind res_kind) `thenM_`
+ returnM (Just (arg_kind,res_kind))
+
+unifyFunKind (FunTy arg_kind res_kind) = returnM (Just (arg_kind,res_kind))
+unifyFunKind (NoteTy _ ty) = unifyFunKind ty
+unifyFunKind other = returnM Nothing
+\end{code}
%************************************************************************
%* *
\begin{code}
unifyCtxt s ty1 ty2 tidy_env -- ty1 expected, ty2 inferred
- = zonkTcType ty1 `thenNF_Tc` \ ty1' ->
- zonkTcType ty2 `thenNF_Tc` \ ty2' ->
- returnNF_Tc (err ty1' ty2')
+ = zonkTcType ty1 `thenM` \ ty1' ->
+ zonkTcType ty2 `thenM` \ ty2' ->
+ returnM (err ty1' ty2')
where
err ty1 ty2 = (env1,
nest 4
unifyKindCtxt swapped tv1 ty2 tidy_env -- not swapped => tv1 expected, ty2 inferred
-- tv1 is zonked already
- = zonkTcType ty2 `thenNF_Tc` \ ty2' ->
- returnNF_Tc (err ty2')
+ = zonkTcType ty2 `thenM` \ ty2' ->
+ returnM (err ty2')
where
err ty2 = (env2, ptext SLIT("When matching types") <+>
sep [quotes pp_expected, ptext SLIT("and"), quotes pp_actual])
pp2 = ppr ty2'
unifyMisMatch ty1 ty2
- = zonkTcType ty1 `thenNF_Tc` \ ty1' ->
- zonkTcType ty2 `thenNF_Tc` \ ty2' ->
+ = zonkTcType ty1 `thenM` \ ty1' ->
+ zonkTcType ty2 `thenM` \ ty2' ->
let
(env, [tidy_ty1, tidy_ty2]) = tidyOpenTypes emptyTidyEnv [ty1',ty2']
msg = hang (ptext SLIT("Couldn't match"))
(env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar
(env2, tidy_ty) = tidyOpenType env1 ty
-unifyOccurCheck tyvar ty
- = (env2, hang (ptext SLIT("Occurs check: cannot construct the infinite type:"))
+unifyCheck problem tyvar ty
+ = (env2, hang msg
4 (sep [ppr tidy_tyvar, char '=', ppr tidy_ty]))
where
(env1, tidy_tyvar) = tidyOpenTyVar emptyTidyEnv tyvar
(env2, tidy_ty) = tidyOpenType env1 ty
+
+ msg = case problem of
+ OccurCheck -> ptext SLIT("Occurs check: cannot construct the infinite type:")
+ NotMonoType -> ptext SLIT("Cannot unify a type variable with a type scheme:")
\end{code}
give a helpful message in checkSigTyVars.
\begin{code}
-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 ->
+checkSigTyVars :: [TcTyVar] -> TcM [TcTyVar]
+checkSigTyVars sig_tvs = check_sig_tyvars emptyVarSet sig_tvs
+
+checkSigTyVarsWrt :: TcTyVarSet -> [TcTyVar] -> TcM [TcTyVar]
+checkSigTyVarsWrt extra_tvs sig_tvs
+ = zonkTcTyVarsAndFV (varSetElems extra_tvs) `thenM` \ extra_tvs' ->
+ check_sig_tyvars extra_tvs' sig_tvs
+
+check_sig_tyvars
+ :: TcTyVarSet -- Global type variables. The universally quantified
+ -- tyvars should not mention any of these
+ -- Guaranteed already zonked.
+ -> [TcTyVar] -- Universally-quantified type variables in the signature
+ -- Not guaranteed zonked.
+ -> TcM [TcTyVar] -- Zonked signature type variables
+
+check_sig_tyvars extra_tvs []
+ = returnM []
+check_sig_tyvars extra_tvs sig_tvs
+ = zonkTcTyVars sig_tvs `thenM` \ sig_tys ->
+ tcGetGlobalTyVars `thenM` \ gbl_tvs ->
+ let
+ env_tvs = gbl_tvs `unionVarSet` extra_tvs
+ in
+ traceTc (text "check_sig_tyvars" <+> (vcat [text "sig_tys" <+> ppr sig_tys,
+ text "gbl_tvs" <+> ppr gbl_tvs,
+ text "extra_tvs" <+> ppr extra_tvs])) `thenM_`
- checkTcM (allDistinctTyVars sig_tys globals)
- (complain sig_tys globals) `thenTc_`
+ checkM (allDistinctTyVars sig_tys env_tvs)
+ (complain sig_tys env_tvs) `thenM_`
- returnTc (map (tcGetTyVar "checkSigTyVars") sig_tys)
+ returnM (map (tcGetTyVar "checkSigTyVars") sig_tys)
where
complain sig_tys globals
= -- "check" checks each sig tyvar in turn
- foldlNF_Tc check
- (env2, emptyVarEnv, [])
- (tidy_tvs `zip` tidy_tys) `thenNF_Tc` \ (env3, _, msgs) ->
+ foldlM check
+ (env2, emptyVarEnv, [])
+ (tidy_tvs `zip` tidy_tys) `thenM` \ (env3, _, msgs) ->
- failWithTcM (env3, main_msg $$ vcat msgs)
+ failWithTcM (env3, main_msg $$ nest 4 (vcat msgs))
where
- (env1, tidy_tvs) = tidyOpenTyVars emptyTidyEnv sig_tyvars
+ (env1, tidy_tvs) = tidyOpenTyVars emptyTidyEnv sig_tvs
(env2, tidy_tys) = tidyOpenTypes env1 sig_tys
main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
-- acc maps a zonked type variable back to a signature type variable
= case tcGetTyVar_maybe ty of {
Nothing -> -- Error (a)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ;
+ returnM (tidy_env, acc, unify_msg sig_tyvar (quotes (ppr ty)) : msgs) ;
Just tv ->
case lookupVarEnv acc tv of {
Just sig_tyvar' -> -- Error (b)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
+ returnM (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
where
thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar')
if tv `elemVarSet` globals -- Error (c) or (d)! Type variable escapes
-- The least comprehensible, so put it last
-- Game plan:
- -- a) get the local TcIds and TyVars from the environment,
+ -- get the local TcIds and TyVars 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 (tcLEnvElts 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)
+ then findGlobals (unitVarSet tv) tidy_env `thenM` \ (tidy_env1, globs) ->
+ returnM (tidy_env1, acc, escape_msg sig_tyvar tv globs : msgs)
else -- All OK
- returnNF_Tc (tidy_env, extendVarEnv acc tv sig_tyvar, msgs)
+ returnM (tidy_env, extendVarEnv acc tv sig_tyvar, msgs)
}}
+\end{code}
------------------------
--- 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 :: Var
- -> TidyEnv
- -> [TcTyThing]
- -> NF_TcM (TidyEnv, [SDoc])
-
-find_globals tv tidy_env things
- = go tidy_env [] things
- where
- go tidy_env acc [] = returnNF_Tc (tidy_env, acc)
- go tidy_env acc (thing : things)
- = find_thing ignore_it tidy_env thing `thenNF_Tc` \ (tidy_env1, maybe_doc) ->
- case maybe_doc of
- Just d -> go tidy_env1 (d:acc) things
- Nothing -> go tidy_env1 acc things
-
- ignore_it ty = not (tv `elemVarSet` tyVarsOfType ty)
-
------------------------
-find_thing ignore_it tidy_env (ATcId id)
- = zonkTcType (idType id) `thenNF_Tc` \ id_ty ->
- if ignore_it id_ty then
- returnNF_Tc (tidy_env, Nothing)
- else let
- (tidy_env', tidy_ty) = tidyOpenType tidy_env id_ty
- msg = sep [ppr id <+> dcolon <+> ppr tidy_ty,
- nest 2 (parens (ptext SLIT("bound at") <+>
- ppr (getSrcLoc id)))]
- in
- returnNF_Tc (tidy_env', Just msg)
-
-find_thing ignore_it tidy_env (ATyVar tv)
- = zonkTcTyVar tv `thenNF_Tc` \ tv_ty ->
- if ignore_it tv_ty then
- returnNF_Tc (tidy_env, Nothing)
- else let
- (tidy_env1, tv1) = tidyOpenTyVar tidy_env tv
- (tidy_env2, tidy_ty) = tidyOpenType tidy_env1 tv_ty
- msg = sep [ptext SLIT("Type variable") <+> quotes (ppr tv1) <+> eq_stuff, nest 2 bound_at]
-
- eq_stuff | Just tv' <- Type.getTyVar_maybe tv_ty, tv == tv' = empty
- | otherwise = equals <+> ppr tv_ty
- -- It's ok to use Type.getTyVar_maybe because ty is zonked by now
-
- bound_at = tyVarBindingInfo tv
- in
- returnNF_Tc (tidy_env2, Just msg)
+\begin{code}
-----------------------
-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') = tidyOpenTyVar 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
+escape_msg sig_tv tv globs
= mk_msg sig_tv <+> ptext SLIT("escapes") $$
- if not (null globs) then
+ if notNull globs then
vcat [pp_it <+> ptext SLIT("is mentioned in the environment:"),
nest 2 (vcat globs)]
- else if not (null frees) then
- vcat [ptext SLIT("It is reachable from the type variable(s)") <+> pprQuotedList frees,
- nest 2 (ptext SLIT("which") <+> is_are <+> ptext SLIT("free in the signature"))
- ]
else
empty -- Sigh. It's really hard to give a good error message
- -- all the time. One bad case is an existential pattern match
+ -- all the time. One bad case is an existential pattern match.
+ -- We rely on the "When..." context to help.
where
- is_are | isSingleton frees = ptext SLIT("is")
- | otherwise = ptext SLIT("are")
pp_it | sig_tv /= tv = ptext SLIT("It unifies with") <+> quotes (ppr tv) <> comma <+> ptext SLIT("which")
| otherwise = ptext SLIT("It")
- vcat_first :: Int -> [SDoc] -> SDoc
- vcat_first n [] = empty
- vcat_first 0 (x:xs) = text "...others omitted..."
- vcat_first n (x:xs) = x $$ vcat_first (n-1) xs
-
unify_msg tv thing = mk_msg tv <+> ptext SLIT("is unified with") <+> thing
mk_msg tv = ptext SLIT("Quantified type variable") <+> quotes (ppr tv)
These two context are used with checkSigTyVars
\begin{code}
-sigCtxt :: [TcTyVar] -> TcThetaType -> TcTauType
- -> TidyEnv -> NF_TcM (TidyEnv, Message)
-sigCtxt sig_tyvars sig_theta sig_tau tidy_env
- = zonkTcType sig_tau `thenNF_Tc` \ actual_tau ->
+sigCtxt :: Id -> [TcTyVar] -> TcThetaType -> TcTauType
+ -> TidyEnv -> TcM (TidyEnv, Message)
+sigCtxt id sig_tvs sig_theta sig_tau tidy_env
+ = zonkTcType sig_tau `thenM` \ actual_tau ->
let
- (env1, tidy_sig_tyvars) = tidyOpenTyVars 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
+ (env1, tidy_sig_tvs) = tidyOpenTyVars tidy_env sig_tvs
+ (env2, tidy_sig_rho) = tidyOpenType env1 (mkPhiTy sig_theta sig_tau)
+ (env3, tidy_actual_tau) = tidyOpenType env2 actual_tau
+ sub_msg = vcat [ptext SLIT("Signature type: ") <+> pprType (mkForAllTys tidy_sig_tvs tidy_sig_rho),
+ ptext SLIT("Type to generalise:") <+> pprType tidy_actual_tau
]
+ msg = vcat [ptext SLIT("When trying to generalise the type inferred for") <+> quotes (ppr id),
+ nest 4 sub_msg]
in
- returnNF_Tc (env3, msg)
-
-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))])
- 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
+ returnM (env3, msg)
\end{code}
-
-
projects / ghc-hetmet.git / blobdiff