\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcHsBootSigs, tcMonoBinds, tcSpecSigs ) where
#include "HsVersions.h"
import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho )
-import CmdLineOpts ( DynFlag(Opt_NoMonomorphismRestriction) )
-import HsSyn ( HsExpr(..), HsBind(..), LHsBind, LHsBinds, Sig(..),
- LSig, Match(..), HsBindGroup(..), IPBind(..),
- collectSigTysFromHsBinds, collectHsBindBinders,
+import CmdLineOpts ( DynFlag(Opt_MonomorphismRestriction) )
+import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, Sig(..),
+ LSig, Match(..), HsBindGroup(..), IPBind(..),
+ HsType(..), hsLTyVarNames, isVanillaLSig,
+ LPat, GRHSs, MatchGroup(..), emptyLHsBinds, isEmptyLHsBinds,
+ collectHsBindBinders, collectPatBinders, pprPatBind
)
-import TcHsSyn ( TcId, zonkId, mkHsLet )
+import TcHsSyn ( TcId, TcDictBinds, zonkId, mkHsLet )
import TcRnMonad
-import Inst ( InstOrigin(..), newDicts, newIPDict, instToId )
-import TcEnv ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName )
-import TcUnify ( Expected(..), newHole, unifyTauTyLists, checkSigTyVarsWrt, sigCtxt )
+import Inst ( InstOrigin(..), newDictsAtLoc, newIPDict, instToId )
+import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
+ newLocalName, tcLookupLocalIds, pprBinders,
+ tcGetGlobalTyVars )
+import TcUnify ( Expected(..), tcInfer, unifyTheta,
+ bleatEscapedTvs, sigCtxt )
import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
tcSimplifyToDicts, tcSimplifyIPs )
-import TcHsType ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..),
- tcTySig, maybeSig, tcAddScopedTyVars
+import TcHsType ( tcHsSigType, UserTypeCtxt(..), tcAddLetBoundTyVars,
+ TcSigInfo(..), TcSigFun, lookupSig
)
-import TcPat ( tcPat, tcSubPat, tcMonoPatBndr )
+import TcPat ( tcPat, PatCtxt(..) )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcMType ( newTyVar, newTyVarTy, zonkTcTyVarToTyVar )
-import TcType ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
- mkPredTy, mkForAllTy, isUnLiftedType )
-import Kind ( liftedTypeKind, argTypeKind, isUnliftedTypeKind )
-
-import CoreFVs ( idFreeTyVars )
+import TcMType ( newTyFlexiVarTy, zonkQuantifiedTyVar,
+ tcInstSigType, zonkTcTypes, zonkTcTyVar )
+import TcType ( TcTyVar, SkolemInfo(SigSkol),
+ TcTauType, TcSigmaType,
+ mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
+ mkForAllTy, isUnLiftedType, tcGetTyVar,
+ mkTyVarTys, tidyOpenTyVar, tidyOpenType )
+import Kind ( argTypeKind )
+import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv, emptyTidyEnv )
+import TysPrim ( alphaTyVar )
import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
import Var ( idType, idName )
-import Name ( Name, getSrcLoc )
+import Name ( Name )
import NameSet
-import Var ( tyVarKind )
import VarSet
-import SrcLoc ( Located(..), srcLocSpan, unLoc, noLoc, getLoc )
+import SrcLoc ( Located(..), unLoc, noLoc, getLoc )
import Bag
-import Util ( isIn, equalLength )
+import Util ( isIn )
import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec,
isNotTopLevel, isAlwaysActive )
import FiniteMap ( listToFM, lookupFM )
-- want. The bit we care about is the local bindings
-- and the free type variables thereof
tcTopBinds binds
- = tc_binds_and_then TopLevel glue binds $
- getLclEnv `thenM` \ env ->
- returnM (emptyBag, env)
+ = tc_binds_and_then TopLevel glue binds $
+ do { env <- getLclEnv
+ ; return (emptyLHsBinds, env) }
where
-- The top level bindings are flattened into a giant
-- implicitly-mutually-recursive MonoBinds
glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env)
+ glue (HsIPBinds _) _ = panic "Top-level HsIpBinds"
-- Can't have a HsIPBinds at top level
+tcHsBootSigs :: [HsBindGroup Name] -> TcM (LHsBinds TcId, TcLclEnv)
+-- A hs-boot file has only one BindGroup, and it only has type
+-- signatures in it. The renamer checked all this
+tcHsBootSigs [HsBindGroup _ sigs _]
+ = do { ids <- mapM (addLocM tc_sig) (filter isVanillaLSig sigs)
+ ; tcExtendIdEnv ids $ do
+ { env <- getLclEnv
+ ; return (emptyLHsBinds, env) }}
+ where
+ tc_sig (Sig (L _ name) ty)
+ = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkLocalId name sigma_ty) }
tcBindsAndThen
:: (HsBindGroup TcId -> thing -> thing) -- Combinator
-- Consider ?x = 4
-- ?y = ?x + 1
tc_ip_bind (IPBind ip expr)
- = newTyVarTy argTypeKind `thenM` \ ty ->
+ = newTyFlexiVarTy argTypeKind `thenM` \ ty ->
newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
tcCheckRho expr ty `thenM` \ expr' ->
returnM (ip_inst, (IPBind ip' expr'))
tc_bind_and_then top_lvl combiner (HsBindGroup binds sigs is_rec) do_next
- | isEmptyBag binds
+ | isEmptyLHsBinds binds
= do_next
| otherwise
= -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
-- a) the type signatures in the binding group
-- b) the bindings in the group
-- c) the scope of the binding group (the "in" part)
- tcAddScopedTyVars (collectSigTysFromHsBinds (bagToList binds)) $
+ tcAddLetBoundTyVars binds $
case top_lvl of
TopLevel -- For the top level don't bother will all this
where
tc_body poly_ids -- Type check the pragmas and "thing inside"
= -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv poly_ids $
+ tcExtendIdEnv poly_ids $
-- Build bindings and IdInfos corresponding to user pragmas
tcSpecSigs sigs `thenM` \ prag_binds ->
-> [LSig Name]
-> RecFlag
-> TcM (LHsBinds TcId, [TcId])
+ -- The returned TcIds are guaranteed zonked
-tcBindWithSigs top_lvl mbind sigs is_rec
- = -- TYPECHECK THE SIGNATURES
- recoverM (returnM []) (
- mappM tcTySig [sig | sig@(L _(Sig name _)) <- sigs]
- ) `thenM` \ tc_ty_sigs ->
+tcBindWithSigs top_lvl mbind sigs is_rec = do
+ { -- TYPECHECK THE SIGNATURES
+ tc_ty_sigs <- recoverM (returnM []) $
+ tcTySigs (filter isVanillaLSig sigs)
+ ; let lookup_sig = lookupSig tc_ty_sigs
-- SET UP THE MAIN RECOVERY; take advantage of any type sigs
- recoverM (
- -- If typechecking the binds fails, then return with each
- -- signature-less binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTyVar liftedTypeKind `thenM` \ alpha_tv ->
- let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- binder_names = collectHsBindBinders mbind
- poly_ids = map mk_dummy binder_names
- mk_dummy name = case maybeSig tc_ty_sigs name of
- Just sig -> sig_poly_id sig -- Signature
- Nothing -> mkLocalId name forall_a_a -- No signature
- in
- traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) `thenM_`
- returnM (emptyBag, poly_ids)
- ) $
-
- -- TYPECHECK THE BINDINGS
- traceTc (ptext SLIT("--------------------------------------------------------")) `thenM_`
- traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind)) `thenM_`
- getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', bndr_names_w_ids), lie_req) ->
- let
- (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids)
- tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
- in
-
- -- GENERALISE
- -- (it seems a bit crude to have to do getLIE twice,
- -- but I can't see a better way just now)
- addSrcSpan (getLoc (head (bagToList mbind))) $
- -- TODO: location a bit awkward, but the mbinds have been
- -- dependency analysed and may no longer be adjacent
-
- addErrCtxt (genCtxt binder_names) $
- getLIE (generalise binder_names mbind tau_tvs lie_req tc_ty_sigs)
- `thenM` \ ((tc_tyvars_to_gen, dict_binds, dict_ids), lie_free) ->
-
-
- -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars
- -- This commits any unbound kind variables to boxed kind, by unification
- -- It's important that the final quanfified type variables
- -- are fully zonked, *including boxity*, because they'll be
- -- included in the forall types of the polymorphic Ids.
- -- At calls of these Ids we'll instantiate fresh type variables from
- -- them, and we use their boxity then.
- mappM zonkTcTyVarToTyVar tc_tyvars_to_gen `thenM` \ real_tyvars_to_gen ->
-
- -- ZONK THE Ids
- -- It's important that the dict Ids are zonked, including the boxity set
- -- in the previous step, because they are later used to form the type of
- -- the polymorphic thing, and forall-types must be zonked so far as
- -- their bound variables are concerned
- mappM zonkId dict_ids `thenM` \ zonked_dict_ids ->
- mappM zonkId mono_ids `thenM` \ zonked_mono_ids ->
+ ; recoverM (recoveryCode mbind lookup_sig) $ do
+
+ { traceTc (ptext SLIT("--------------------------------------------------------"))
+ ; traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind))
+
+ -- TYPECHECK THE BINDINGS
+ ; ((mbind', mono_bind_infos), lie_req)
+ <- getLIE (tcMonoBinds mbind lookup_sig is_rec)
+
+ -- CHECK FOR UNLIFTED BINDINGS
+ -- These must be non-recursive etc, and are not generalised
+ -- They desugar to a case expression in the end
+ ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
+ ; if any isUnLiftedType zonked_mono_tys then
+ do { -- Unlifted bindings
+ checkUnliftedBinds top_lvl is_rec mbind
+ ; extendLIEs lie_req
+ ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
+ mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id)
+ mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id)
+
+ ; return ( unitBag $ noLoc $ AbsBinds [] [] exports emptyNameSet mbind',
+ [poly_id | (_, poly_id, _) <- exports]) } -- Guaranteed zonked
+
+ else do -- The normal lifted case: GENERALISE
+ { is_unres <- isUnRestrictedGroup mbind tc_ty_sigs
+ ; (tyvars_to_gen, dict_binds, dict_ids)
+ <- setSrcSpan (getLoc (head (bagToList mbind))) $
+ -- TODO: location a bit awkward, but the mbinds have been
+ -- dependency analysed and may no longer be adjacent
+ addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
+ generalise top_lvl is_unres mono_bind_infos tc_ty_sigs lie_req
+
+ -- FINALISE THE QUANTIFIED TYPE VARIABLES
+ -- The quantified type variables often include meta type variables
+ -- we want to freeze them into ordinary type variables, and
+ -- default their kind (e.g. from OpenTypeKind to TypeKind)
+ ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
-- BUILD THE POLYMORPHIC RESULT IDs
- let
- exports = zipWith mk_export binder_names zonked_mono_ids
+ ; let
+ exports = map mk_export mono_bind_infos
poly_ids = [poly_id | (_, poly_id, _) <- exports]
- dict_tys = map idType zonked_dict_ids
+ dict_tys = map idType dict_ids
- inlines = mkNameSet [ name
- | L _ (InlineSig True (L _ name) _) <- sigs]
+ inlines = mkNameSet [ name
+ | L _ (InlineSig True (L _ name) _) <- sigs]
-- Any INLINE sig (regardless of phase control)
-- makes the RHS look small
-
inline_phases = listToFM [ (name, phase)
| L _ (InlineSig _ (L _ name) phase) <- sigs,
not (isAlwaysActive phase)]
-- Set the IdInfo field to control the inline phase
-- AlwaysActive is the default, so don't bother with them
+ add_inlines id = attachInlinePhase inline_phases id
- mk_export binder_name zonked_mono_id
- = (tyvars,
- attachInlinePhase inline_phases poly_id,
- zonked_mono_id)
+ mk_export (binder_name, mb_sig, mono_id)
+ = case mb_sig of
+ Just sig -> (sig_tvs sig, add_inlines (sig_id sig), mono_id)
+ Nothing -> (tyvars_to_gen', add_inlines new_poly_id, mono_id)
where
- (tyvars, poly_id) =
- case maybeSig tc_ty_sigs binder_name of
- Just sig -> (sig_tvs sig, sig_poly_id sig)
- Nothing -> (real_tyvars_to_gen, new_poly_id)
-
new_poly_id = mkLocalId binder_name poly_ty
- poly_ty = mkForAllTys real_tyvars_to_gen
+ poly_ty = mkForAllTys tyvars_to_gen'
$ mkFunTys dict_tys
- $ idType zonked_mono_id
- -- It's important to build a fully-zonked poly_ty, because
- -- we'll slurp out its free type variables when extending the
- -- local environment (tcExtendLocalValEnv); if it's not zonked
- -- it appears to have free tyvars that aren't actually free
- -- at all.
- in
+ $ idType mono_id
- traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
- exports, map idType poly_ids)) `thenM_`
+ -- ZONK THE poly_ids, because they are used to extend the type
+ -- environment; see the invariant on TcEnv.tcExtendIdEnv
+ ; zonked_poly_ids <- mappM zonkId poly_ids
- -- Check for an unlifted, non-overloaded group
- -- In that case we must make extra checks
- if any (isUnLiftedType . idType) zonked_mono_ids && null zonked_dict_ids
- then -- Some bindings are unlifted
- checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind `thenM_`
-
- extendLIEs lie_req `thenM_`
- returnM (
- unitBag $ noLoc $
- AbsBinds [] [] exports inlines mbind',
- -- Do not generate even any x=y bindings
- poly_ids
- )
+ ; traceTc (text "binding:" <+> ppr ((dict_ids, dict_binds),
+ exports, map idType zonked_poly_ids))
- else -- The normal case
- extendLIEs lie_free `thenM_`
- returnM (
+ ; return (
unitBag $ noLoc $
- AbsBinds real_tyvars_to_gen
- zonked_dict_ids
- exports
- inlines
- (dict_binds `unionBags` mbind'),
- poly_ids
+ AbsBinds tyvars_to_gen'
+ dict_ids
+ exports
+ inlines
+ (dict_binds `unionBags` mbind'),
+ zonked_poly_ids
)
+ } } }
+
+-- If typechecking the binds fails, then return with each
+-- signature-less binder given type (forall a.a), to minimise
+-- subsequent error messages
+recoveryCode mbind lookup_sig
+ = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
+ ; return (emptyLHsBinds, poly_ids) }
+ where
+ forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
+ binder_names = collectHsBindBinders mbind
+ poly_ids = map mk_dummy binder_names
+ mk_dummy name = case lookup_sig name of
+ Just sig -> sig_id sig -- Signature
+ Nothing -> mkLocalId name forall_a_a -- No signature
attachInlinePhase inline_phases bndr
= case lookupFM inline_phases (idName bndr) of
-- Check that non-overloaded unlifted bindings are
-- a) non-recursive,
-- b) not top level,
--- c) non-polymorphic
--- d) not a multiple-binding group (more or less implied by (a))
-
-checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind
- = ASSERT( not (any (isUnliftedTypeKind . tyVarKind) real_tyvars_to_gen) )
- -- The instCantBeGeneralised stuff in tcSimplify should have
- -- already raised an error if we're trying to generalise an
- -- unboxed tyvar (NB: unboxed tyvars are always introduced
- -- along with a class constraint) and it's better done there
- -- because we have more precise origin information.
- -- That's why we just use an ASSERT here.
-
- checkTc (isNotTopLevel top_lvl)
+-- c) not a multiple-binding group (more or less implied by (a))
+
+checkUnliftedBinds top_lvl is_rec mbind
+ = checkTc (isNotTopLevel top_lvl)
(unliftedBindErr "Top-level" mbind) `thenM_`
checkTc (isNonRec is_rec)
(unliftedBindErr "Recursive" mbind) `thenM_`
checkTc (isSingletonBag mbind)
- (unliftedBindErr "Multiple" mbind) `thenM_`
- checkTc (null real_tyvars_to_gen)
- (unliftedBindErr "Polymorphic" mbind)
+ (unliftedBindErr "Multiple" mbind)
\end{code}
%************************************************************************
%* *
-\subsection{getTyVarsToGen}
+\subsection{tcMonoBind}
%* *
%************************************************************************
+@tcMonoBinds@ deals with a single @MonoBind@.
+The signatures have been dealt with already.
+
\begin{code}
-generalise binder_names mbind tau_tvs lie_req sigs =
+tcMonoBinds :: LHsBinds Name
+ -> TcSigFun -> RecFlag
+ -> TcM (LHsBinds TcId, [MonoBindInfo])
+
+tcMonoBinds binds lookup_sig is_rec
+ = do { tc_binds <- mapBagM (wrapLocM (tcLhs lookup_sig)) binds
+
+ -- Bring (a) the scoped type variables, and (b) the Ids, into scope for the RHSs
+ -- For (a) it's ok to bring them all into scope at once, even
+ -- though each type sig should scope only over its own RHS,
+ -- because the renamer has sorted all that out.
+ ; let mono_info = getMonoBindInfo tc_binds
+ rhs_tvs = [ (name, mkTyVarTy tv)
+ | (_, Just sig, _) <- mono_info,
+ (name, tv) <- sig_scoped sig `zip` sig_tvs sig ]
+ rhs_id_env = map mk mono_info -- A binding for each term variable
+
+ ; binds' <- tcExtendTyVarEnv2 rhs_tvs $
+ tcExtendIdEnv2 rhs_id_env $
+ traceTc (text "tcMonoBinds" <+> vcat [ppr n <+> ppr id <+> ppr (idType id) | (n,id) <- rhs_id_env]) `thenM_`
+ mapBagM (wrapLocM tcRhs) tc_binds
+ ; return (binds', mono_info) }
+ where
+ mk (name, Just sig, _) = (name, sig_id sig) -- Use the type sig if there is one
+ mk (name, Nothing, mono_id) = (name, mono_id) -- otherwise use a monomorphic version
+
+------------------------
+-- tcLhs typechecks the LHS of the bindings, to construct the environment in which
+-- we typecheck the RHSs. Basically what we are doing is this: for each binder:
+-- if there's a signature for it, use the instantiated signature type
+-- otherwise invent a type variable
+-- You see that quite directly in the FunBind case.
+--
+-- But there's a complication for pattern bindings:
+-- data T = MkT (forall a. a->a)
+-- MkT f = e
+-- Here we can guess a type variable for the entire LHS (which will be refined to T)
+-- but we want to get (f::forall a. a->a) as the RHS environment.
+-- The simplest way to do this is to typecheck the pattern, and then look up the
+-- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
+-- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
+
+data TcMonoBind -- Half completed; LHS done, RHS not done
+ = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
+ | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
+
+type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
+ -- Type signature (if any), and
+ -- the monomorphic bound things
+
+bndrNames :: [MonoBindInfo] -> [Name]
+bndrNames mbi = [n | (n,_,_) <- mbi]
+
+getMonoType :: MonoBindInfo -> TcTauType
+getMonoType (_,_,mono_id) = idType mono_id
+
+tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
+tcLhs lookup_sig (FunBind (L nm_loc name) inf matches)
+ = do { let mb_sig = lookup_sig name
+ ; mono_name <- newLocalName name
+ ; mono_ty <- mk_mono_ty mb_sig
+ ; let mono_id = mkLocalId mono_name mono_ty
+ ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
+ where
+ mk_mono_ty (Just sig) = return (sig_tau sig)
+ mk_mono_ty Nothing = newTyFlexiVarTy argTypeKind
+
+tcLhs lookup_sig bind@(PatBind pat grhss _)
+ = do { let tc_pat exp_ty = tcPat (LetPat lookup_sig) pat exp_ty lookup_infos
+ ; ((pat', ex_tvs, infos), pat_ty)
+ <- addErrCtxt (patMonoBindsCtxt pat grhss)
+ (tcInfer tc_pat)
- -- check for -fno-monomorphism-restriction
- doptM Opt_NoMonomorphismRestriction `thenM` \ no_MR ->
- let is_unrestricted | no_MR = True
- | otherwise = isUnRestrictedGroup tysig_names mbind
- in
+ -- Don't know how to deal with pattern-bound existentials yet
+ ; checkTc (null ex_tvs) (existentialExplode bind)
+
+ ; return (TcPatBind infos pat' grhss pat_ty) }
+ where
+ names = collectPatBinders pat
+
+ -- After typechecking the pattern, look up the binder
+ -- names, which the pattern has brought into scope.
+ lookup_infos :: TcM [MonoBindInfo]
+ lookup_infos = do { mono_ids <- tcLookupLocalIds names
+ ; return [ (name, lookup_sig name, mono_id)
+ | (name, mono_id) <- names `zip` mono_ids] }
+
+-------------------
+tcRhs :: TcMonoBind -> TcM (HsBind TcId)
+tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
+ = do { matches' <- tcMatchesFun (idName mono_id) matches
+ (Check (idType mono_id))
+ ; return (FunBind fun' inf matches') }
+
+tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
+ = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
+ tcGRHSsPat grhss (Check pat_ty)
+ ; return (PatBind pat' grhss' pat_ty) }
+
+
+---------------------
+getMonoBindInfo :: Bag (Located TcMonoBind) -> [MonoBindInfo]
+getMonoBindInfo tc_binds
+ = foldrBag (get_info . unLoc) [] tc_binds
+ where
+ get_info (TcFunBind info _ _ _) rest = info : rest
+ get_info (TcPatBind infos _ _ _) rest = infos ++ rest
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
- if not is_unrestricted then -- RESTRICTED CASE
- -- Check signature contexts are empty
- checkTc (all is_mono_sig sigs)
- (restrictedBindCtxtErr binder_names) `thenM_`
+Type signatures are tricky. See Note [Signature skolems] in TcType
+
+\begin{code}
+tcTySigs :: [LSig Name] -> TcM [TcSigInfo]
+-- The trick here is that all the signatures should have the same
+-- context, and we want to share type variables for that context, so that
+-- all the right hand sides agree a common vocabulary for their type
+-- constraints
+tcTySigs [] = return []
+
+tcTySigs sigs
+ = do { (tc_sig1 : tc_sigs) <- mappM tcTySig sigs
+ ; mapM (check_ctxt tc_sig1) tc_sigs
+ ; return (tc_sig1 : tc_sigs) }
+ where
+ -- Check tha all the signature contexts are the same
+ -- The type signatures on a mutually-recursive group of definitions
+ -- must all have the same context (or none).
+ --
+ -- We unify them because, with polymorphic recursion, their types
+ -- might not otherwise be related. This is a rather subtle issue.
+ check_ctxt :: TcSigInfo -> TcSigInfo -> TcM ()
+ check_ctxt sig1@(TcSigInfo { sig_theta = theta1 }) sig@(TcSigInfo { sig_theta = theta })
+ = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
+ addErrCtxt (sigContextsCtxt sig1 sig) $
+ unifyTheta theta1 theta
+
+
+tcTySig :: LSig Name -> TcM TcSigInfo
+tcTySig (L span (Sig (L _ name) ty))
+ = setSrcSpan span $
+ do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; (tvs, theta, tau) <- tcInstSigType name sigma_ty
+ ; loc <- getInstLoc (SigOrigin (SigSkol name))
+
+ ; let poly_id = mkLocalId name sigma_ty
+
+ -- The scoped names are the ones explicitly mentioned
+ -- in the HsForAll. (There may be more in sigma_ty, because
+ -- of nested type synonyms. See Note [Scoped] with TcSigInfo.)
+ scoped_names = case ty of
+ L _ (HsForAllTy _ tvs _ _) -> hsLTyVarNames tvs
+ other -> []
+
+ ; return (TcSigInfo { sig_id = poly_id, sig_scoped = scoped_names,
+ sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
+ sig_loc = loc }) }
+\end{code}
+
+\begin{code}
+generalise :: TopLevelFlag -> Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst]
+ -> TcM ([TcTyVar], TcDictBinds, [TcId])
+generalise top_lvl is_unrestricted mono_infos sigs lie_req
+ | not is_unrestricted -- RESTRICTED CASE
+ = -- Check signature contexts are empty
+ do { checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr bndr_names)
-- Now simplify with exactly that set of tyvars
-- We have to squash those Methods
- tcSimplifyRestricted doc tau_tvs lie_req `thenM` \ (qtvs, binds) ->
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndr_names
+ tau_tvs lie_req
-- Check that signature type variables are OK
- checkSigsTyVars qtvs sigs `thenM` \ final_qtvs ->
+ ; final_qtvs <- checkSigsTyVars qtvs sigs
+
+ ; return (final_qtvs, binds, []) }
- returnM (final_qtvs, binds, [])
+ | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
+ = tcSimplifyInfer doc tau_tvs lie_req
- else if null sigs then -- UNRESTRICTED CASE, NO TYPE SIGS
- tcSimplifyInfer doc tau_tvs lie_req
+ | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
+ = do { let sig1 = head sigs
+ ; sig_lie <- newDictsAtLoc (sig_loc sig1) (sig_theta sig1)
+ ; let -- The "sig_avails" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the lie_avail
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
+ sig_avails = sig_lie ++ local_meths
- else -- UNRESTRICTED CASE, WITH TYPE SIGS
- -- CHECKING CASE: Unrestricted group, there are type signatures
- -- Check signature contexts are identical
- checkSigsCtxts sigs `thenM` \ (sig_avails, sig_dicts) ->
-
-- Check that the needed dicts can be
-- expressed in terms of the signature ones
- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenM` \ (forall_tvs, dict_binds) ->
+ ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
-- Check that signature type variables are OK
- checkSigsTyVars forall_tvs sigs `thenM` \ final_qtvs ->
+ ; final_qtvs <- checkSigsTyVars forall_tvs sigs
- returnM (final_qtvs, dict_binds, sig_dicts)
+ ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
where
- tysig_names = map (idName . sig_poly_id) sigs
+ bndr_names = bndrNames mono_infos
+ tau_tvs = foldr (unionVarSet . tyVarsOfType . getMonoType) emptyVarSet mono_infos
is_mono_sig sig = null (sig_theta sig)
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders bndr_names
- doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names
-
------------------------
- -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE
- -- The type signatures on a mutually-recursive group of definitions
- -- must all have the same context (or none).
- --
- -- We unify them because, with polymorphic recursion, their types
- -- might not otherwise be related. This is a rather subtle issue.
- -- ToDo: amplify
-checkSigsCtxts sigs@(TySigInfo { sig_poly_id = id1, sig_tvs = sig_tvs, sig_theta = theta1, sig_loc = span}
- : other_sigs)
- = addSrcSpan span $
- mappM_ check_one other_sigs `thenM_`
- if null theta1 then
- returnM ([], []) -- Non-overloaded type signatures
- else
- newDicts SignatureOrigin theta1 `thenM` \ sig_dicts ->
- let
- -- The "sig_avails" is the stuff available. We get that from
- -- the context of the type signature, BUT ALSO the lie_avail
- -- so that polymorphic recursion works right (see comments at end of fn)
- sig_avails = sig_dicts ++ sig_meths
- in
- returnM (sig_avails, map instToId sig_dicts)
- where
- sig1_dict_tys = map mkPredTy theta1
- sig_meths = concatMap sig_insts sigs
-
- check_one (TySigInfo {sig_poly_id = id, sig_theta = theta})
- = addErrCtxt (sigContextsCtxt id1 id) $
- checkTc (equalLength theta theta1) sigContextsErr `thenM_`
- unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
+ mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
+ sig_theta = theta, sig_tau = tau, sig_loc = loc }) mono_id
+ = Method mono_id poly_id (mkTyVarTys tvs) theta tau loc
checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
checkSigsTyVars qtvs sigs
- = mappM check_one sigs `thenM` \ sig_tvs_s ->
- let
- -- Sigh. Make sure that all the tyvars in the type sigs
- -- appear in the returned ty var list, which is what we are
- -- going to generalise over. Reason: we occasionally get
- -- silly types like
- -- type T a = () -> ()
- -- f :: T a
- -- f () = ()
- -- Here, 'a' won't appear in qtvs, so we have to add it
-
- sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
- all_tvs = extendVarSetList sig_tvs qtvs
- in
- returnM (varSetElems all_tvs)
+ = do { gbl_tvs <- tcGetGlobalTyVars
+ ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
+
+ ; let -- Sigh. Make sure that all the tyvars in the type sigs
+ -- appear in the returned ty var list, which is what we are
+ -- going to generalise over. Reason: we occasionally get
+ -- silly types like
+ -- type T a = () -> ()
+ -- f :: T a
+ -- f () = ()
+ -- Here, 'a' won't appear in qtvs, so we have to add it
+ sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
+ all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
+ ; returnM all_tvs }
where
- check_one (TySigInfo {sig_poly_id = id, sig_tvs = tvs, sig_theta = theta, sig_tau = tau})
- = addErrCtxt (ptext SLIT("In the type signature for")
- <+> quotes (ppr id)) $
- addErrCtxtM (sigCtxt id tvs theta tau) $
- checkSigTyVarsWrt (idFreeTyVars id) tvs
-\end{code}
+ check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
+ sig_theta = theta, sig_tau = tau})
+ = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
+ addErrCtxtM (sigCtxt id tvs theta tau) $
+ do { tvs' <- checkDistinctTyVars tvs
+ ; ifM (any (`elemVarSet` gbl_tvs) tvs')
+ (bleatEscapedTvs gbl_tvs tvs tvs')
+ ; return tvs' }
+
+checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
+-- (checkDistinctTyVars tvs) checks that the tvs from one type signature
+-- are still all type variables, and all distinct from each other.
+-- It returns a zonked set of type variables.
+-- For example, if the type sig is
+-- f :: forall a b. a -> b -> b
+-- we want to check that 'a' and 'b' haven't
+-- (a) been unified with a non-tyvar type
+-- (b) been unified with each other (all distinct)
+
+checkDistinctTyVars sig_tvs
+ = do { zonked_tvs <- mapM zonk_one sig_tvs
+ ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
+ ; return zonked_tvs }
+ where
+ zonk_one sig_tv = do { ty <- zonkTcTyVar sig_tv
+ ; return (tcGetTyVar "checkDistinctTyVars" ty) }
+ -- 'ty' is bound to be a type variable, because SigSkolTvs
+ -- can only be unified with type variables
+
+ check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
+ -- The TyVarEnv maps each zonked type variable back to its
+ -- corresponding user-written signature type variable
+ check_dup acc (sig_tv, zonked_tv)
+ = case lookupVarEnv acc zonked_tv of
+ Just sig_tv' -> bomb_out sig_tv sig_tv'
+
+ Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
+
+ bomb_out sig_tv1 sig_tv2
+ = failWithTc (ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
+ <+> ptext SLIT("is unified with another quantified type variable")
+ <+> ppr tidy_tv2)
+ where
+ (env1, tidy_tv1) = tidyOpenTyVar emptyTidyEnv sig_tv1
+ (_env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
+\end{code}
+
@getTyVarsToGen@ decides what type variables to generalise over.
find which tyvars are constrained.
\begin{code}
-isUnRestrictedGroup :: [Name] -- Signatures given for these
- -> LHsBinds Name
- -> Bool
-isUnRestrictedGroup sigs binds = all (unrestricted . unLoc) (bagToList binds)
+isUnRestrictedGroup :: LHsBinds Name -> [TcSigInfo] -> TcM Bool
+isUnRestrictedGroup binds sigs
+ = do { mono_restriction <- doptM Opt_MonomorphismRestriction
+ ; return (not mono_restriction || all_unrestricted) }
where
- unrestricted (PatBind other _) = False
- unrestricted (VarBind v _) = v `is_elem` sigs
- unrestricted (FunBind v _ matches) = unrestricted_match matches
- || unLoc v `is_elem` sigs
+ all_unrestricted = all (unrestricted . unLoc) (bagToList binds)
+ tysig_names = map (idName . sig_id) sigs
- unrestricted_match (L _ (Match [] _ _) : _) = False
+ unrestricted (PatBind other _ _) = False
+ unrestricted (VarBind v _) = v `is_elem` tysig_names
+ unrestricted (FunBind v _ matches) = unrestricted_match matches
+ || unLoc v `is_elem` tysig_names
+
+ unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
-- No args => like a pattern binding
unrestricted_match other = True
-- Some args => a function binding
%************************************************************************
%* *
-\subsection{tcMonoBind}
-%* *
-%************************************************************************
-
-@tcMonoBinds@ deals with a single @MonoBind@.
-The signatures have been dealt with already.
-
-\begin{code}
-tcMonoBinds :: LHsBinds Name
- -> [TcSigInfo] -> RecFlag
- -> TcM (LHsBinds TcId,
- Bag (Name, -- Bound names
- TcId)) -- Corresponding monomorphic bound things
-
-tcMonoBinds mbinds tc_ty_sigs is_rec
- -- Three stages:
- -- 1. Check the patterns, building up an environment binding
- -- the variables in this group (in the recursive case)
- -- 2. Extend the environment
- -- 3. Check the RHSs
- = mapBagM tc_lbind_pats mbinds `thenM` \ bag_of_pairs ->
- let
- (complete_it, xve)
- = foldrBag combine
- (returnM (emptyBag, emptyBag), emptyBag)
- bag_of_pairs
- combine (complete_it1, xve1) (complete_it2, xve2)
- = (complete_it, xve1 `unionBags` xve2)
- where
- complete_it = complete_it1 `thenM` \ (b1, bs1) ->
- complete_it2 `thenM` \ (b2, bs2) ->
- returnM (b1 `consBag` b2, bs1 `unionBags` bs2)
- in
- tcExtendLocalValEnv2 (bagToList xve) complete_it
- where
- tc_lbind_pats :: LHsBind Name
- -> TcM (TcM (LHsBind TcId, Bag (Name,TcId)), -- Completer
- Bag (Name,TcId))
- -- wrapper for tc_bind_pats to deal with the location stuff
- tc_lbind_pats (L loc bind)
- = addSrcSpan loc $ do
- (tc, bag) <- tc_bind_pats bind
- return (wrap tc, bag)
- where
- wrap tc = addSrcSpan loc $ do
- (bind, stuff) <- tc
- return (L loc bind, stuff)
-
-
- tc_bind_pats :: HsBind Name
- -> TcM (TcM (HsBind TcId, Bag (Name,TcId)), -- Completer
- Bag (Name,TcId))
- tc_bind_pats (FunBind (L nm_loc name) inf matches)
- -- Three cases:
- -- a) Type sig supplied
- -- b) No type sig and recursive
- -- c) No type sig and non-recursive
-
- | Just sig <- maybeSig tc_ty_sigs name
- = let -- (a) There is a type signature
- -- Use it for the environment extension, and check
- -- the RHS has the appropriate type (with outer for-alls stripped off)
- mono_id = sig_mono_id sig
- mono_ty = idType mono_id
- complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
- returnM (FunBind (L nm_loc mono_id) inf matches',
- unitBag (name, mono_id))
- in
- returnM (complete_it, if isRec is_rec then unitBag (name, sig_poly_id sig)
- else emptyBag)
-
- | isRec is_rec
- = -- (b) No type signature, and recursive
- -- So we must use an ordinary H-M type variable
- -- which means the variable gets an inferred tau-type
- newLocalName name `thenM` \ mono_name ->
- newTyVarTy argTypeKind `thenM` \ mono_ty ->
- let
- mono_id = mkLocalId mono_name mono_ty
- complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
- returnM (FunBind (L nm_loc mono_id) inf matches',
- unitBag (name, mono_id))
- in
- returnM (complete_it, unitBag (name, mono_id))
-
- | otherwise -- (c) No type signature, and non-recursive
- = let -- So we can use a 'hole' type to infer a higher-rank type
- complete_it
- = newHole `thenM` \ hole ->
- tcMatchesFun name matches (Infer hole) `thenM` \ matches' ->
- readMutVar hole `thenM` \ fun_ty ->
- newLocalName name `thenM` \ mono_name ->
- let
- mono_id = mkLocalId mono_name fun_ty
- in
- returnM (FunBind (L nm_loc mono_id) inf matches',
- unitBag (name, mono_id))
- in
- returnM (complete_it, emptyBag)
-
- tc_bind_pats bind@(PatBind pat grhss)
- = -- Now typecheck the pattern
- -- We do now support binding fresh (not-already-in-scope) scoped
- -- type variables in the pattern of a pattern binding.
- -- For example, this is now legal:
- -- (x::a, y::b) = e
- -- The type variables are brought into scope in tc_binds_and_then,
- -- so we don't have to do anything here.
- newHole `thenM` \ hole ->
- tcPat tc_pat_bndr pat (Infer hole) `thenM` \ (pat', tvs, ids, lie_avail) ->
- readMutVar hole `thenM` \ pat_ty ->
-
- -- Don't know how to deal with pattern-bound existentials yet
- checkTc (isEmptyBag tvs && null lie_avail)
- (existentialExplode bind) `thenM_`
-
- let
- complete_it = addErrCtxt (patMonoBindsCtxt bind) $
- tcGRHSsPat grhss (Check pat_ty) `thenM` \ grhss' ->
- returnM (PatBind pat' grhss', ids)
- in
- returnM (complete_it, if isRec is_rec then ids else emptyBag)
-
- -- tc_pat_bndr is used when dealing with a LHS binder in a pattern.
- -- If there was a type sig for that Id, we want to make it much
- -- as if that type signature had been on the binder as a SigPatIn.
- -- We check for a type signature; if there is one, we use the mono_id
- -- from the signature. This is how we make sure the tau part of the
- -- signature actually matches the type of the LHS; then tc_bind_pats
- -- ensures the LHS and RHS have the same type
-
- tc_pat_bndr name pat_ty
- = case maybeSig tc_ty_sigs name of
- Nothing -> newLocalName name `thenM` \ bndr_name ->
- tcMonoPatBndr bndr_name pat_ty
-
- Just sig -> addSrcSpan (srcLocSpan (getSrcLoc name)) $
- -- TODO: location wrong
- tcSubPat (idType mono_id) pat_ty `thenM` \ co_fn ->
- returnM (co_fn, mono_id)
- where
- mono_id = sig_mono_id sig
-\end{code}
-
-
-%************************************************************************
-%* *
\subsection{SPECIALIZE pragmas}
%* *
%************************************************************************
{-# SPECIALISE f :: <type> = g #-}
which promised that g implemented f at <type>, but we do that with
a RULE now:
- {-# SPECIALISE (f::<type) = g #-}
+ {-# RULES (f::<type>) = g #-}
\begin{code}
tcSpecSigs :: [LSig Name] -> TcM (LHsBinds TcId)
tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs)
= -- SPECIALISE f :: forall b. theta => tau = g
- addSrcSpan loc $
+ setSrcSpan loc $
addErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
returnM (binds_rest `snocBag` L loc spec_bind)
tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
-tcSpecSigs [] = returnM emptyBag
+tcSpecSigs [] = returnM emptyLHsBinds
\end{code}
%************************************************************************
\begin{code}
-patMonoBindsCtxt bind
- = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
+-- This one is called on LHS, when pat and grhss are both Name
+-- and on RHS, when pat is TcId and grhss is still Name
+patMonoBindsCtxt pat grhss
+ = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
-----------------------------------------------
valSpecSigCtxt v ty
nest 4 (ppr v <+> dcolon <+> ppr ty)]
-----------------------------------------------
-sigContextsErr = ptext SLIT("Mismatched contexts")
-
-sigContextsCtxt s1 s2
+sigContextsCtxt sig1 sig2
= vcat [ptext SLIT("When matching the contexts of the signatures for"),
- nest 2 (vcat [ppr s1 <+> dcolon <+> ppr (idType s1),
- ppr s2 <+> dcolon <+> ppr (idType s2)]),
+ nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
+ ppr id2 <+> dcolon <+> ppr (idType id2)]),
ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
+ where
+ id1 = sig_id sig1
+ id2 = sig_id sig2
+
-----------------------------------------------
unliftedBindErr flavour mbind
genCtxt binder_names
= ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
-
--- Used in error messages
--- Use quotes for a single one; they look a bit "busy" for several
-pprBinders [bndr] = quotes (ppr bndr)
-pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
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