import TcType ( TcType, TcKind, TcTyVar, TcThetaType, TcTauType,
typeToTcType, kindToTcKind,
newKindVar, tcInstSigVar,
- zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType
+ zonkTcKindToKind, zonkTcTypeToType, zonkTcTyVars, zonkTcType, zonkTcTyVar
)
import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToIdBndr )
import TcUnify ( unifyKind, unifyKinds, unifyTypeKind )
mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy, mkUsgTy,
mkUsForAllTy, zipFunTys, hoistForAllTys,
mkSigmaTy, mkDictTy, mkPredTy, mkTyConApp,
- mkAppTys, splitForAllTys, splitRhoTy,
+ mkAppTys, splitForAllTys, splitRhoTy, mkRhoTy,
boxedTypeKind, unboxedTypeKind, tyVarsOfType,
mkArrowKinds, getTyVar_maybe, getTyVar,
- tidyOpenType, tidyOpenTypes, tidyTyVar,
+ tidyOpenType, tidyOpenTypes, tidyTyVar, tidyTyVars,
tyVarsOfType, tyVarsOfTypes
)
-import PprType ( pprConstraint )
+import PprType ( pprConstraint, pprType )
import Subst ( mkTopTyVarSubst, substTy )
import Id ( mkVanillaId, idName, idType, idFreeTyVars )
import Var ( TyVar, mkTyVar, mkNamedUVar, varName )
import UniqFM ( elemUFM, foldUFM )
import SrcLoc ( SrcLoc )
import Unique ( Unique, Uniquable(..) )
-import Util ( zipWithEqual, zipLazy, mapAccumL )
+import Util ( mapAccumL, isSingleton )
import Outputable
\end{code}
give a helpful message in checkSigTyVars.
\begin{code}
-checkSigTyVars :: [TcTyVar] -- The original signature type variables
+checkSigTyVars :: [TcTyVar] -- Universally-quantified type variables in the signature
+ -> TcTyVarSet -- Tyvars that are free in the type signature
+ -- These should *already* be in the global-var set, and are
+ -- used here only to improve the error message
-> TcM s [TcTyVar] -- Zonked signature type variables
-checkSigTyVars [] = returnTc []
+checkSigTyVars [] free = returnTc []
-checkSigTyVars sig_tyvars
+checkSigTyVars sig_tyvars free_tyvars
= zonkTcTyVars sig_tyvars `thenNF_Tc` \ sig_tys ->
tcGetGlobalTyVars `thenNF_Tc` \ globals ->
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)
+ then tcGetValueEnv `thenNF_Tc` \ ve ->
+ find_globals tv env [] (valueEnvIds ve) `thenNF_Tc` \ (env1, globs) ->
+ find_frees tv env1 [] (varSetElems free_tyvars) `thenNF_Tc` \ (env2, frees) ->
+ returnNF_Tc (env2, acc, escape_msg sig_tyvar tv globs frees : msgs)
else -- All OK
returnNF_Tc (env, extendVarEnv acc tv sig_tyvar, msgs)
-- 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 acc []
+ = returnNF_Tc (tidy_env, acc)
-find_globals tv tidy_env (id:ids)
+find_globals tv tidy_env acc (id:ids)
| not (isLocallyDefined id) ||
isEmptyVarSet (idFreeTyVars id)
- = find_globals tv tidy_env ids
+ = 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
-
-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_globals tv tidy_env acc ids
+
+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
+sigCtxt :: Message -> [TcTyVar] -> TcThetaType -> TcTauType
-> TidyEnv -> NF_TcM s (TidyEnv, Message)
-sigCtxt mk_msg sig_ty tidy_env
- = let
- (env1, tidy_sig_ty) = tidyOpenType tidy_env sig_ty
+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 env1 actual_tau
+ forall | null sig_tyvars = empty
+ | otherwise = ptext SLIT("forall") <+> hsep (map ppr tidy_sig_tyvars) <> dot
+ msg = vcat [ptext SLIT("Signature type: ") <+> forall <+> pprType 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,
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