kcHsLiftedSigType, kcHsContext,
tcAddScopedTyVars, tcHsTyVars, mkImmutTyVars,
- TcSigInfo(..), tcTySig, mkTcSig, maybeSig,
- checkSigTyVars, sigCtxt, sigPatCtxt
+ TcSigInfo(..), tcTySig, mkTcSig, maybeSig
) where
#include "HsVersions.h"
import TcMonad
import TcEnv ( tcExtendTyVarEnv, tcLookup, tcLookupGlobal,
- tcGetGlobalTyVars, tcLEnvElts, tcInLocalScope,
+ tcInLocalScope,
TyThing(..), TcTyThing(..), tcExtendKindEnv
)
-import TcMType ( newKindVar, tcInstSigTyVars,
- zonkKindEnv, zonkTcType, zonkTcTyVars, zonkTcTyVar,
- unifyKind, unifyOpenTypeKind,
+import TcMType ( newKindVar, tcInstSigTyVars, zonkKindEnv,
checkValidType, UserTypeCtxt(..), pprUserTypeCtxt
)
+import TcUnify ( unifyKind, unifyOpenTypeKind )
import TcType ( Type, Kind, SourceType(..), ThetaType, TyVarDetails(..),
- TcTyVar, TcTyVarSet, TcKind, TcThetaType, TcTauType,
+ TcTyVar, TcKind, TcThetaType, TcTauType,
mkTyVarTy, mkTyVarTys, mkFunTy, mkSynTy,
tcSplitForAllTys, tcSplitRhoTy,
- hoistForAllTys, allDistinctTyVars, zipFunTys,
- mkSigmaTy, mkPredTy, mkTyConApp, mkAppTys, mkRhoTy,
+ hoistForAllTys, zipFunTys,
+ mkSigmaTy, mkPredTy, mkTyConApp, mkAppTys,
liftedTypeKind, unliftedTypeKind, mkArrowKind,
- mkArrowKinds, tcGetTyVar_maybe, tcGetTyVar, tcSplitFunTy_maybe,
- tidyOpenType, tidyOpenTypes, tidyOpenTyVar, tidyOpenTyVars,
- tyVarsOfType, mkForAllTys
+ mkArrowKinds, tcSplitFunTy_maybe
)
-import qualified Type ( getTyVar_maybe )
import Inst ( Inst, InstOrigin(..), newMethodWithGivenTy, instToId )
-import PprType ( pprType )
import Subst ( mkTopTyVarSubst, substTy )
-import CoreFVs ( idFreeTyVars )
import Id ( mkLocalId, idName, idType )
-import Var ( Var, TyVar, mkTyVar, tyVarKind, isMutTyVar, mutTyVarDetails )
-import VarEnv
-import VarSet
+import Var ( TyVar, mkTyVar, tyVarKind )
import ErrUtils ( Message )
import TyCon ( TyCon, isSynTyCon, tyConKind )
import Class ( classTyCon )
-import Name ( Name, getSrcLoc )
+import Name ( Name )
import NameSet
import TysWiredIn ( mkListTy, mkTupleTy, genUnitTyCon )
import BasicTypes ( Boxity(..) )
import SrcLoc ( SrcLoc )
-import Util ( isSingleton, lengthIs )
+import Util ( lengthIs )
import Outputable
\end{code}
%************************************************************************
%* *
-\subsection{Checking signature type variables}
-%* *
-%************************************************************************
-
-@checkSigTyVars@ is used after the type in a type signature has been unified with
-the actual type found. It then checks that the type variables of the type signature
-are
- (a) Still all type variables
- eg matching signature [a] against inferred type [(p,q)]
- [then a will be unified to a non-type variable]
-
- (b) Still all distinct
- eg matching signature [(a,b)] against inferred type [(p,p)]
- [then a and b will be unified together]
-
- (c) Not mentioned in the environment
- eg the signature for f in this:
-
- g x = ... where
- f :: a->[a]
- f y = [x,y]
-
- Here, f is forced to be monorphic by the free occurence of x.
-
- (d) Not (unified with another type variable that is) in scope.
- eg f x :: (r->r) = (\y->y) :: forall a. a->r
- when checking the expression type signature, we find that
- even though there is nothing in scope whose type mentions r,
- nevertheless the type signature for the expression isn't right.
-
- Another example is in a class or instance declaration:
- class C a where
- op :: forall b. a -> b
- op x = x
- Here, b gets unified with a
-
-Before doing this, the substitution is applied to the signature type variable.
-
-We used to have the notion of a "DontBind" type variable, which would
-only be bound to itself or nothing. Then points (a) and (b) were
-self-checking. But it gave rise to bogus consequential error messages.
-For example:
-
- f = (*) -- Monomorphic
-
- g :: Num a => a -> a
- g x = f x x
-
-Here, we get a complaint when checking the type signature for g,
-that g isn't polymorphic enough; but then we get another one when
-dealing with the (Num x) context arising from f's definition;
-we try to unify x with Int (to default it), but find that x has already
-been unified with the DontBind variable "a" from g's signature.
-This is really a problem with side-effecting unification; we'd like to
-undo g's effects when its type signature fails, but unification is done
-by side effect, so we can't (easily).
-
-So we revert to ordinary type variables for signatures, and try to
-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 ->
-
- checkTcM (allDistinctTyVars sig_tys globals)
- (complain sig_tys globals) `thenTc_`
-
- returnTc (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) ->
-
- failWithTcM (env3, main_msg $$ vcat msgs)
- where
- (env1, tidy_tvs) = tidyOpenTyVars emptyTidyEnv sig_tyvars
- (env2, tidy_tys) = tidyOpenTypes env1 sig_tys
-
- main_msg = ptext SLIT("Inferred type is less polymorphic than expected")
-
- 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 tcGetTyVar_maybe ty of {
- Nothing -> -- Error (a)!
- 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)!
- returnNF_Tc (tidy_env, acc, unify_msg sig_tyvar thing : msgs)
- where
- thing = ptext SLIT("another quantified type variable") <+> quotes (ppr sig_tyvar')
-
- ; Nothing ->
-
- 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,
- -- 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)
-
- else -- All OK
- 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 :: 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 | isMutTyVar tv = mut_info -- The expected case
- | otherwise = empty
-
- mut_info = sep [ptext SLIT("is bound by the") <+> ppr (mutTyVarDetails tv),
- ptext SLIT("at") <+> ppr (getSrcLoc tv)]
- in
- returnNF_Tc (tidy_env2, Just msg)
-
------------------------
-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
- = mk_msg sig_tv <+> ptext SLIT("escapes") $$
- if not (null 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
- 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)
-\end{code}
-
-These two context are used with checkSigTyVars
-
-\begin{code}
-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) = 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,
- when
- ]
- 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
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{Errors and contexts}
%* *
%************************************************************************
projects / ghc-hetmet.git / blobdiff