\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBinds,
- tcSpecSigs, tcBindWithSigs ) where
+module TcBinds ( tcLocalBinds, tcTopBinds,
+ tcHsBootSigs, tcMonoBinds,
+ TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
+ TcSigInfo(..),
+ badBootDeclErr ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun )
-import {-# SOURCE #-} TcExpr ( tcExpr )
-
-import CmdLineOpts ( opt_NoMonomorphismRestriction )
-import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..),
- Match(..), HsMatchContext(..),
- collectMonoBinders, andMonoBinds,
- collectSigTysFromMonoBinds
- )
-import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
-import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet )
-
-import TcMonad
-import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..),
- newDicts, instToId
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcMonoExpr )
+
+import DynFlags ( DynFlag(Opt_MonomorphismRestriction, Opt_GlasgowExts) )
+import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, LHsBind, Sig(..),
+ HsLocalBinds(..), HsValBinds(..), HsIPBinds(..),
+ LSig, Match(..), IPBind(..), Prag(..),
+ HsType(..), LHsType, HsExplicitForAll(..), hsLTyVarNames,
+ isVanillaLSig, sigName, placeHolderNames, isPragLSig,
+ LPat, GRHSs, MatchGroup(..), pprLHsBinds, mkHsCoerce,
+ collectHsBindBinders, collectPatBinders, pprPatBind, isBangHsBind
)
-import TcEnv ( tcExtendLocalValEnv, newLocalName )
-import TcUnify ( unifyTauTyLists, checkSigTyVars, sigCtxt )
-import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, tcSimplifyToDicts )
-import TcMonoType ( tcHsSigType, UserTypeCtxt(..),
- TcSigInfo(..), tcTySig, maybeSig, tcAddScopedTyVars
- )
-import TcPat ( tcPat, tcSubPat, tcMonoPatBndr )
+import TcHsSyn ( zonkId )
+
+import TcRnMonad
+import Inst ( newDictsAtLoc, newIPDict, instToId )
+import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
+ pprBinders, tcLookupLocalId_maybe, tcLookupId,
+ tcGetGlobalTyVars )
+import TcUnify ( tcInfer, tcSubExp, unifyTheta,
+ bleatEscapedTvs, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck,
+ tcSimplifyRestricted, tcSimplifyIPs )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
+import TcPat ( tcPat, PatCtxt(..) )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcMType ( newTyVar, newTyVarTy, newHoleTyVarTy,
- zonkTcTyVarToTyVar
- )
-import TcType ( mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
- mkPredTy, mkForAllTy, isUnLiftedType,
- unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind
- )
-
-import CoreFVs ( idFreeTyVars )
-import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
-import Var ( idType, idName )
-import Name ( Name, getSrcLoc )
+import TcMType ( newFlexiTyVarTy, zonkQuantifiedTyVar, zonkSigTyVar,
+ tcInstSigTyVars, tcInstSkolTyVars, tcInstType,
+ zonkTcType, zonkTcTypes, zonkTcTyVars )
+import TcType ( TcType, TcTyVar, TcThetaType,
+ SkolemInfo(SigSkol), UserTypeCtxt(FunSigCtxt),
+ TcTauType, TcSigmaType, isUnboxedTupleType,
+ mkTyVarTy, mkForAllTys, mkFunTys, exactTyVarsOfType,
+ mkForAllTy, isUnLiftedType, tcGetTyVar,
+ mkTyVarTys, tidyOpenTyVar )
+import Kind ( argTypeKind )
+import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv )
+import TysWiredIn ( unitTy )
+import TysPrim ( alphaTyVar )
+import Id ( Id, mkLocalId, mkVanillaGlobal )
+import IdInfo ( vanillaIdInfo )
+import Var ( TyVar, idType, idName )
+import Name ( Name )
import NameSet
-import Var ( tyVarKind )
+import NameEnv
import VarSet
+import SrcLoc ( Located(..), unLoc, getLoc )
import Bag
-import Util ( isIn, equalLength )
-import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isNotTopLevel,
- isAlwaysActive )
-import FiniteMap ( listToFM, lookupFM )
+import ErrUtils ( Message )
+import Digraph ( SCC(..), stronglyConnComp )
+import Maybes ( expectJust, isJust, isNothing, orElse )
+import Util ( singleton )
+import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
+ RecFlag(..), isNonRec, InlineSpec, defaultInlineSpec )
import Outputable
\end{code}
dictionaries, which we resolve at the module level.
\begin{code}
-tcTopBinds :: RenamedHsBinds -> TcM ((TcMonoBinds, TcEnv), LIE)
+tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
+ -- Note: returning the TcLclEnv is more than we really
+ -- 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 $
- tcGetEnv `thenNF_Tc` \ env ->
- returnTc ((EmptyMonoBinds, env), emptyLIE)
+ = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
+ ; return (foldr (unionBags . snd) emptyBag prs, env) }
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive LHsBinds
+
+tcHsBootSigs :: HsValBinds Name -> TcM [Id]
+-- A hs-boot file has only one BindGroup, and it only has type
+-- signatures in it. The renamer checked all this
+tcHsBootSigs (ValBindsOut binds sigs)
+ = do { checkTc (null binds) badBootDeclErr
+ ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
where
- glue is_rec binds1 (binds2, thing) = (binds1 `AndMonoBinds` binds2, thing)
-
+ tc_boot_sig (TypeSig (L _ name) ty)
+ = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
+ -- Notice that we make GlobalIds, not LocalIds
+tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
+
+badBootDeclErr :: Message
+badBootDeclErr = ptext SLIT("Illegal declarations in an hs-boot file")
+
+------------------------
+tcLocalBinds :: HsLocalBinds Name -> TcM thing
+ -> TcM (HsLocalBinds TcId, thing)
+
+tcLocalBinds EmptyLocalBinds thing_inside
+ = do { thing <- thing_inside
+ ; return (EmptyLocalBinds, thing) }
+
+tcLocalBinds (HsValBinds binds) thing_inside
+ = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
+ ; return (HsValBinds binds', thing) }
+
+tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
+ = do { (thing, lie) <- getLIE thing_inside
+ ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
+
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ ; dict_binds <- tcSimplifyIPs avail_ips lie
+ ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
+ where
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (IPBind ip expr)
+ = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
+ newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
+ tcMonoExpr expr ty `thenM` \ expr' ->
+ returnM (ip_inst, (IPBind ip' expr'))
+
+------------------------
+tcValBinds :: TopLevelFlag
+ -> HsValBinds Name -> TcM thing
+ -> TcM (HsValBinds TcId, thing)
+
+tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside
+ = pprPanic "tcValBinds" (ppr binds)
+
+tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
+ = do { -- Typecheck the signature
+ ; let { prag_fn = mkPragFun sigs
+ ; ty_sigs = filter isVanillaLSig sigs
+ ; sig_fn = mkSigFun ty_sigs }
+
+ ; poly_ids <- mapM tcTySig ty_sigs
+
+ -- Extend the envt right away with all
+ -- the Ids declared with type signatures
+ ; (binds', thing) <- tcExtendIdEnv poly_ids $
+ tc_val_binds top_lvl sig_fn prag_fn
+ binds thing_inside
+
+ ; return (ValBindsOut binds' sigs, thing) }
+
+------------------------
+tc_val_binds :: TopLevelFlag -> TcSigFun -> TcPragFun
+ -> [(RecFlag, LHsBinds Name)] -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+-- Typecheck a whole lot of value bindings,
+-- one strongly-connected component at a time
+
+tc_val_binds top_lvl sig_fn prag_fn [] thing_inside
+ = do { thing <- thing_inside
+ ; return ([], thing) }
+
+tc_val_binds top_lvl sig_fn prag_fn (group : groups) thing_inside
+ = do { (group', (groups', thing))
+ <- tc_group top_lvl sig_fn prag_fn group $
+ tc_val_binds top_lvl sig_fn prag_fn groups thing_inside
+ ; return (group' ++ groups', thing) }
+
+------------------------
+tc_group :: TopLevelFlag -> TcSigFun -> TcPragFun
+ -> (RecFlag, LHsBinds Name) -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+
+-- Typecheck one strongly-connected component of the original program.
+-- We get a list of groups back, because there may
+-- be specialisations etc as well
+
+tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
+ = -- A single non-recursive binding
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ do { (binds, thing) <- tcPolyBinds top_lvl NonRecursive NonRecursive
+ sig_fn prag_fn binds thing_inside
+ ; return ([(NonRecursive, b) | b <- binds], thing) }
+
+tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
+ = -- A recursive strongly-connected component
+ -- To maximise polymorphism (with -fglasgow-exts), we do a new
+ -- strongly-connected-component analysis, this time omitting
+ -- any references to variables with type signatures.
+ --
+ -- Then we bring into scope all the variables with type signatures
+ do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
+ ; gla_exts <- doptM Opt_GlasgowExts
+ ; (binds,thing) <- if gla_exts
+ then go new_sccs
+ else tc_binds Recursive binds thing_inside
+ ; return ([(Recursive, unionManyBags binds)], thing) }
+ -- Rec them all together
+ where
+ new_sccs :: [SCC (LHsBind Name)]
+ new_sccs = stronglyConnComp (mkEdges sig_fn binds)
-tcBindsAndThen
- :: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator
- -> RenamedHsBinds
- -> TcM (thing, LIE)
- -> TcM (thing, LIE)
+-- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], thing)
+ go (scc:sccs) = do { (binds1, (binds2, thing)) <- go1 scc (go sccs)
+ ; return (binds1 ++ binds2, thing) }
+ go [] = do { thing <- thing_inside; return ([], thing) }
-tcBindsAndThen = tc_binds_and_then NotTopLevel
+ go1 (AcyclicSCC bind) = tc_binds NonRecursive (unitBag bind)
+ go1 (CyclicSCC binds) = tc_binds Recursive (listToBag binds)
-tc_binds_and_then top_lvl combiner EmptyBinds do_next
- = do_next
-tc_binds_and_then top_lvl combiner (MonoBind EmptyMonoBinds sigs is_rec) do_next
- = do_next
+ tc_binds rec_tc binds = tcPolyBinds top_lvl Recursive rec_tc sig_fn prag_fn binds
-tc_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next
- = tc_binds_and_then top_lvl combiner b1 $
- tc_binds_and_then top_lvl combiner b2 $
- do_next
+------------------------
+mkEdges :: TcSigFun -> LHsBinds Name
+ -> [(LHsBind Name, BKey, [BKey])]
-tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
- = -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
- -- Notice that they scope over
- -- 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 (collectSigTysFromMonoBinds bind) $
+type BKey = Int -- Just number off the bindings
- -- TYPECHECK THE SIGNATURES
- mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs ->
-
- tcBindWithSigs top_lvl bind tc_ty_sigs
- sigs is_rec `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
-
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $
-
- -- Build bindings and IdInfos corresponding to user pragmas
- tcSpecSigs sigs `thenTc` \ (prag_binds, prag_lie) ->
-
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie) ->
-
- -- Create specialisations of functions bound here
- -- We want to keep non-recursive things non-recursive
- -- so that we desugar unlifted bindings correctly
- case (top_lvl, is_rec) of
-
- -- For the top level don't bother will all this bindInstsOfLocalFuns stuff
- -- All the top level things are rec'd together anyway, so it's fine to
- -- leave them to the tcSimplifyTop, and quite a bit faster too
- (TopLevel, _)
- -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing,
- thing_lie `plusLIE` prag_lie `plusLIE` poly_lie)
-
- (NotTopLevel, NonRecursive)
- -> bindInstsOfLocalFuns
- (thing_lie `plusLIE` prag_lie)
- poly_ids `thenTc` \ (thing_lie', lie_binds) ->
-
- returnTc (
- combiner NonRecursive poly_binds $
- combiner NonRecursive prag_binds $
- combiner Recursive lie_binds $
- -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
- -- aren't guaranteed in dependency order (though we could change
- -- that); hence the Recursive marker.
- thing,
-
- thing_lie' `plusLIE` poly_lie
- )
-
- (NotTopLevel, Recursive)
- -> bindInstsOfLocalFuns
- (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie)
- poly_ids `thenTc` \ (final_lie, lie_binds) ->
-
- returnTc (
- combiner Recursive (
- poly_binds `andMonoBinds`
- lie_binds `andMonoBinds`
- prag_binds) thing,
- final_lie
- )
-\end{code}
+mkEdges sig_fn binds
+ = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
+ Just key <- [lookupNameEnv key_map n], no_sig n ])
+ | (bind, key) <- keyd_binds
+ ]
+ where
+ no_sig :: Name -> Bool
+ no_sig n = isNothing (sig_fn n)
+
+ keyd_binds = bagToList binds `zip` [0::BKey ..]
+
+ key_map :: NameEnv BKey -- Which binding it comes from
+ key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
+ , bndr <- bindersOfHsBind bind ]
+
+bindersOfHsBind :: HsBind Name -> [Name]
+bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
+bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
+
+------------------------
+tcPolyBinds :: TopLevelFlag
+ -> RecFlag -- Whether the group is really recursive
+ -> RecFlag -- Whether it's recursive for typechecking purposes
+ -> TcSigFun -> TcPragFun
+ -> LHsBinds Name
+ -> TcM thing
+ -> TcM ([LHsBinds TcId], thing)
+
+-- Typechecks a single bunch of bindings all together,
+-- and generalises them. The bunch may be only part of a recursive
+-- group, because we use type signatures to maximise polymorphism
+--
+-- Deals with the bindInstsOfLocalFuns thing too
+--
+-- Returns a list because the input may be a single non-recursive binding,
+-- in which case the dependency order of the resulting bindings is
+-- important.
+
+tcPolyBinds top_lvl rec_group rec_tc sig_fn prag_fn scc thing_inside
+ = -- NB: polymorphic recursion means that a function
+ -- may use an instance of itself, we must look at the LIE arising
+ -- from the function's own right hand side. Hence the getLIE
+ -- encloses the tc_poly_binds.
+ do { traceTc (text "tcPolyBinds" <+> ppr scc)
+ ; ((binds1, poly_ids, thing), lie) <- getLIE $
+ do { (binds1, poly_ids) <- tc_poly_binds top_lvl rec_group rec_tc
+ sig_fn prag_fn scc
+ ; thing <- tcExtendIdEnv poly_ids thing_inside
+ ; return (binds1, poly_ids, thing) }
+
+ ; if isTopLevel top_lvl
+ then -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop,
+ -- and quite a bit faster too
+ do { extendLIEs lie; return (binds1, thing) }
+
+ else do -- Nested case
+ { lie_binds <- bindInstsOfLocalFuns lie poly_ids
+ ; return (binds1 ++ [lie_binds], thing) }}
+
+------------------------
+tc_poly_binds :: TopLevelFlag -- See comments on tcPolyBinds
+ -> RecFlag -> RecFlag
+ -> TcSigFun -> TcPragFun
+ -> LHsBinds Name
+ -> TcM ([LHsBinds TcId], [TcId])
+-- Typechecks the bindings themselves
+-- Knows nothing about the scope of the bindings
+
+tc_poly_binds top_lvl rec_group rec_tc sig_fn prag_fn binds
+ = let
+ binder_names = collectHsBindBinders binds
+ bind_list = bagToList binds
+
+ loc = getLoc (head bind_list)
+ -- TODO: location a bit awkward, but the mbinds have been
+ -- dependency analysed and may no longer be adjacent
+ in
+ -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+ setSrcSpan loc $
+ recoverM (recoveryCode binder_names) $ do
+
+ { traceTc (ptext SLIT("------------------------------------------------"))
+ ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
+
+ -- TYPECHECK THE BINDINGS
+ ; ((binds', mono_bind_infos), lie_req)
+ <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
+
+ -- 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)
+ ; is_strict <- checkStrictBinds top_lvl rec_group binds'
+ zonked_mono_tys mono_bind_infos
+ ; if is_strict then
+ do { 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, [])
+ -- ToDo: prags for unlifted bindings
+
+ ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
+ [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
+
+ else do -- The normal lifted case: GENERALISE
+ { is_unres <- isUnRestrictedGroup bind_list sig_fn
+ ; (tyvars_to_gen, dict_binds, dict_ids)
+ <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
+ generalise top_lvl is_unres mono_bind_infos 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
+ ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids))
+ mono_bind_infos
-%************************************************************************
-%* *
-\subsection{tcBindWithSigs}
-%* *
-%************************************************************************
+ -- ZONK THE poly_ids, because they are used to extend the type
+ -- environment; see the invariant on TcEnv.tcExtendIdEnv
+ ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
+ ; zonked_poly_ids <- mappM zonkId poly_ids
-@tcBindWithSigs@ deals with a single binding group. It does generalisation,
-so all the clever stuff is in here.
+ ; traceTc (text "binding:" <+> ppr (zonked_poly_ids `zip` map idType zonked_poly_ids))
-* binder_names and mbind must define the same set of Names
+ ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
+ dict_ids exports
+ (dict_binds `unionBags` binds')
-* The Names in tc_ty_sigs must be a subset of binder_names
+ ; return ([unitBag abs_bind], zonked_poly_ids)
+ } }
-* The Ids in tc_ty_sigs don't necessarily have to have the same name
- as the Name in the tc_ty_sig
-\begin{code}
-tcBindWithSigs
- :: TopLevelFlag
- -> RenamedMonoBinds
- -> [TcSigInfo]
- -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs
- -> RecFlag
- -> TcM (TcMonoBinds, LIE, [TcId])
-
-tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec
- = recoverTc (
- -- If typechecking the binds fails, then return with each
- -- signature-less binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTyVar liftedTypeKind `thenNF_Tc` \ alpha_tv ->
- let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- binder_names = collectMonoBinders mbind
- poly_ids = map mk_dummy binder_names
- mk_dummy name = case maybeSig tc_ty_sigs name of
- Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id -- Signature
- Nothing -> mkLocalId name forall_a_a -- No signature
- in
- returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
- ) $
-
- -- TYPECHECK THE BINDINGS
- tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) ->
- let
- tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
- in
+--------------
+mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo
+ -> TcM ([TyVar], Id, Id, [Prag])
+mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
+ = case mb_sig of
+ Nothing -> do { prags <- tcPrags poly_id (prag_fn poly_name)
+ ; return (inferred_tvs, poly_id, mono_id, prags) }
+ where
+ poly_id = mkLocalId poly_name poly_ty
+ poly_ty = mkForAllTys inferred_tvs
+ $ mkFunTys dict_tys
+ $ idType mono_id
+
+ Just sig -> do { let poly_id = sig_id sig
+ ; prags <- tcPrags poly_id (prag_fn poly_name)
+ ; sig_tys <- zonkTcTyVars (sig_tvs sig)
+ ; let sig_tvs' = map (tcGetTyVar "mkExport") sig_tys
+ ; return (sig_tvs', poly_id, mono_id, prags) }
+ -- We zonk the sig_tvs here so that the export triple
+ -- always has zonked type variables;
+ -- a convenient invariant
+
+
+------------------------
+type TcPragFun = Name -> [LSig Name]
+
+mkPragFun :: [LSig Name] -> TcPragFun
+mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
+ where
+ prs = [(expectJust "mkPragFun" (sigName sig), sig)
+ | sig <- sigs, isPragLSig sig]
+ env = foldl add emptyNameEnv prs
+ add env (n,p) = extendNameEnv_Acc (:) singleton env n p
+
+tcPrags :: Id -> [LSig Name] -> TcM [Prag]
+tcPrags poly_id prags = mapM tc_prag prags
+ where
+ tc_prag (L loc prag) = setSrcSpan loc $
+ addErrCtxt (pragSigCtxt prag) $
+ tcPrag poly_id prag
- -- GENERALISE
- tcAddSrcLoc (minimum (map getSrcLoc binder_names)) $
- tcAddErrCtxt (genCtxt binder_names) $
- generalise binder_names mbind tau_tvs lie_req tc_ty_sigs
- `thenTc` \ (tc_tyvars_to_gen, lie_free, dict_binds, dict_ids) ->
-
-
- -- 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.
- mapNF_Tc zonkTcTyVarToTyVar tc_tyvars_to_gen `thenNF_Tc` \ 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
- mapNF_Tc zonkId dict_ids `thenNF_Tc` \ zonked_dict_ids ->
- mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids ->
-
- -- CHECK FOR BOGUS UNLIFTED BINDINGS
- checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids `thenTc_`
+pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
- -- BUILD THE POLYMORPHIC RESULT IDs
- let
- exports = zipWith mk_export binder_names zonked_mono_ids
- dict_tys = map idType zonked_dict_ids
-
- inlines = mkNameSet [name | InlineSig True name _ loc <- inline_sigs]
- no_inlines = listToFM [(name, phase) | InlineSig _ name phase _ <- inline_sigs,
- not (isAlwaysActive phase)]
- -- AlwaysActive is the default, so don't bother with them
-
- mk_export binder_name zonked_mono_id
- = (tyvars,
- attachNoInlinePrag no_inlines poly_id,
- zonked_mono_id)
- where
- (tyvars, poly_id) =
- case maybeSig tc_ty_sigs binder_name of
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) ->
- (sig_tyvars, sig_poly_id)
- Nothing -> (real_tyvars_to_gen, new_poly_id)
-
- new_poly_id = mkLocalId binder_name poly_ty
- poly_ty = mkForAllTys real_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
+tcPrag :: TcId -> Sig Name -> TcM Prag
+tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl
+tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
+tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl)
- traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
- exports, [idType poly_id | (_, poly_id, _) <- exports])) `thenTc_`
-
- -- BUILD RESULTS
- returnTc (
- AbsBinds real_tyvars_to_gen
- zonked_dict_ids
- exports
- inlines
- (dict_binds `andMonoBinds` mbind'),
- lie_free,
- [poly_id | (_, poly_id, _) <- exports]
- )
-
-attachNoInlinePrag no_inlines bndr
- = case lookupFM no_inlines (idName bndr) of
- Just prag -> bndr `setInlinePragma` prag
- Nothing -> bndr
-
-checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids
- = ASSERT( not (any ((eqKind unliftedTypeKind) . 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.
-
- -- Check that pattern-bound variables are not unlifted
- (if or [ (idName id `elem` pat_binders) && isUnLiftedType (idType id)
- | id <- zonked_mono_ids ] then
- addErrTc (unliftedBindErr "Pattern" mbind)
- else
- returnTc ()
- ) `thenTc_`
-
- -- Unlifted bindings must be non-recursive,
- -- not top level, non-polymorphic, and not pattern bound
- if any (isUnLiftedType . idType) zonked_mono_ids then
- checkTc (isNotTopLevel top_lvl)
- (unliftedBindErr "Top-level" mbind) `thenTc_`
- checkTc (isNonRec is_rec)
- (unliftedBindErr "Recursive" mbind) `thenTc_`
- checkTc (null real_tyvars_to_gen)
- (unliftedBindErr "Polymorphic" mbind)
- else
- returnTc ()
+tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
+tcSpecPrag poly_id hs_ty inl
+ = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
+ ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
+ ; extendLIEs lie
+ ; let const_dicts = map instToId lie
+ ; return (SpecPrag (mkHsCoerce co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
+
+--------------
+-- If typechecking the binds fails, then return with each
+-- signature-less binder given type (forall a.a), to minimise
+-- subsequent error messages
+recoveryCode binder_names
+ = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
+ ; poly_ids <- mapM mk_dummy binder_names
+ ; return ([], poly_ids) }
+ where
+ mk_dummy name = do { mb_id <- tcLookupLocalId_maybe name
+ ; case mb_id of
+ Just id -> return id -- Had signature, was in envt
+ Nothing -> return (mkLocalId name forall_a_a) } -- No signature
+
+forall_a_a :: TcType
+forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
+
+
+-- Check that non-overloaded unlifted bindings are
+-- a) non-recursive,
+-- b) not top level,
+-- c) not a multiple-binding group (more or less implied by (a))
+
+checkStrictBinds :: TopLevelFlag -> RecFlag
+ -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
+ -> TcM Bool
+checkStrictBinds top_lvl rec_group mbind mono_tys infos
+ | unlifted || bang_pat
+ = do { checkTc (isNotTopLevel top_lvl)
+ (strictBindErr "Top-level" unlifted mbind)
+ ; checkTc (isNonRec rec_group)
+ (strictBindErr "Recursive" unlifted mbind)
+ ; checkTc (isSingletonBag mbind)
+ (strictBindErr "Multiple" unlifted mbind)
+ ; mapM_ check_sig infos
+ ; return True }
+ | otherwise
+ = return False
+ where
+ unlifted = any isUnLiftedType mono_tys
+ bang_pat = anyBag (isBangHsBind . unLoc) mbind
+ check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
+ (badStrictSig unlifted sig)
+ check_sig other = return ()
+
+strictBindErr flavour unlifted mbind
+ = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:")) 4 (ppr mbind)
where
- pat_binders :: [Name]
- pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds)
+ msg | unlifted = ptext SLIT("bindings for unlifted types")
+ | otherwise = ptext SLIT("bang-pattern bindings")
- justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds
- justPatBindings (AndMonoBinds b1 b2) binds =
- justPatBindings b1 (justPatBindings b2 binds)
- justPatBindings other_bind binds = binds
+badStrictSig unlifted sig
+ = hang (ptext SLIT("Illegal polymorphic signature in") <+> msg)
+ 4 (ppr sig)
+ where
+ msg | unlifted = ptext SLIT("an unlifted binding")
+ | otherwise = ptext SLIT("a bang-pattern binding")
\end{code}
-Polymorphic recursion
-~~~~~~~~~~~~~~~~~~~~~
-The game plan for polymorphic recursion in the code above is
+%************************************************************************
+%* *
+\subsection{tcMonoBind}
+%* *
+%************************************************************************
- * Bind any variable for which we have a type signature
- to an Id with a polymorphic type. Then when type-checking
- the RHSs we'll make a full polymorphic call.
+@tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
+The signatures have been dealt with already.
-This fine, but if you aren't a bit careful you end up with a horrendous
-amount of partial application and (worse) a huge space leak. For example:
+\begin{code}
+tcMonoBinds :: [LHsBind Name]
+ -> TcSigFun
+ -> RecFlag -- Whether the binding is recursive for typechecking purposes
+ -- i.e. the binders are mentioned in their RHSs, and
+ -- we are not resuced by a type signature
+ -> TcM (LHsBinds TcId, [MonoBindInfo])
+
+tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
+ fun_matches = matches, bind_fvs = fvs })]
+ sig_fn -- Single function binding,
+ NonRecursive -- binder isn't mentioned in RHS,
+ | Nothing <- sig_fn name -- ...with no type signature
+ = -- In this very special case we infer the type of the
+ -- right hand side first (it may have a higher-rank type)
+ -- and *then* make the monomorphic Id for the LHS
+ -- e.g. f = \(x::forall a. a->a) -> <body>
+ -- We want to infer a higher-rank type for f
+ setSrcSpan b_loc $
+ do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name matches)
+
+ -- Check for an unboxed tuple type
+ -- f = (# True, False #)
+ -- Zonk first just in case it's hidden inside a meta type variable
+ -- (This shows up as a (more obscure) kind error
+ -- in the 'otherwise' case of tcMonoBinds.)
+ ; zonked_rhs_ty <- zonkTcType rhs_ty
+ ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
+ (unboxedTupleErr name zonked_rhs_ty)
+
+ ; mono_name <- newLocalName name
+ ; let mono_id = mkLocalId mono_name zonked_rhs_ty
+ ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
+ fun_matches = matches', bind_fvs = fvs,
+ fun_co_fn = co_fn })),
+ [(name, Nothing, mono_id)]) }
+
+tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
+ fun_matches = matches, bind_fvs = fvs })]
+ sig_fn -- Single function binding
+ non_rec
+ | Just sig <- sig_fn name -- ...with a type signature
+ = -- When we have a single function binding, with a type signature
+ -- we can (a) use genuine, rigid skolem constants for the type variables
+ -- (b) bring (rigid) scoped type variables into scope
+ setSrcSpan b_loc $
+ do { tc_sig <- tcInstSig True sig
+ ; mono_name <- newLocalName name
+ ; let mono_ty = sig_tau tc_sig
+ mono_id = mkLocalId mono_name mono_ty
+ rhs_tvs = [ (name, mkTyVarTy tv)
+ | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
+
+ ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
+ tcMatchesFun mono_name matches mono_ty
+
+ ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
+ fun_infix = inf, fun_matches = matches',
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn }
+ ; return (unitBag (L b_loc fun_bind'),
+ [(name, Just tc_sig, mono_id)]) }
+
+tcMonoBinds binds sig_fn non_rec
+ = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
+
+ -- Bring the monomorphic Ids, into scope for the RHSs
+ ; let mono_info = getMonoBindInfo tc_binds
+ rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
+ -- A monomorphic binding for each term variable that lacks
+ -- a type sig. (Ones with a sig are already in scope.)
+
+ ; binds' <- tcExtendIdEnv2 rhs_id_env $
+ traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
+ | (n,id) <- rhs_id_env]) `thenM_`
+ mapM (wrapLocM tcRhs) tc_binds
+ ; return (listToBag binds', mono_info) }
+
+------------------------
+-- 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 sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
+ = do { mb_sig <- tcInstSig_maybe (sig_fn 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 = newFlexiTyVarTy argTypeKind
- f :: Eq a => [a] -> [a]
- f xs = ...f...
+tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
+ = do { mb_sigs <- mapM (tcInstSig_maybe . sig_fn) names
-If we don't take care, after typechecking we get
+ ; let nm_sig_prs = names `zip` mb_sigs
+ tau_sig_env = mkNameEnv [ (name, sig_tau sig) | (name, Just sig) <- nm_sig_prs]
+ sig_tau_fn = lookupNameEnv tau_sig_env
- f = /\a -> \d::Eq a -> let f' = f a d
- in
- \ys:[a] -> ...f'...
+ tc_pat exp_ty = tcPat (LetPat sig_tau_fn) pat exp_ty unitTy $ \ _ ->
+ mapM lookup_info nm_sig_prs
+ -- The unitTy is a bit bogus; it's the "result type" for lookup_info.
-Notice the the stupid construction of (f a d), which is of course
-identical to the function we're executing. In this case, the
-polymorphic recursion isn't being used (but that's a very common case).
-We'd prefer
+ -- After typechecking the pattern, look up the binder
+ -- names, which the pattern has brought into scope.
+ lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
+ lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
+ ; return (name, mb_sig, mono_id) }
- f = /\a -> \d::Eq a -> letrec
- fm = \ys:[a] -> ...fm...
- in
- fm
+ ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
+ tcInfer tc_pat
-This can lead to a massive space leak, from the following top-level defn
-(post-typechecking)
+ ; return (TcPatBind infos pat' grhss pat_ty) }
+ where
+ names = collectPatBinders pat
- ff :: [Int] -> [Int]
- ff = f Int dEqInt
-Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
-f' is another thunk which evaluates to the same thing... and you end
-up with a chain of identical values all hung onto by the CAF ff.
+tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
+ -- AbsBind, VarBind impossible
- ff = f Int dEqInt
+-------------------
+tcRhs :: TcMonoBind -> TcM (HsBind TcId)
+tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
+ = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) matches
+ (idType mono_id)
+ ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn }) }
- = let f' = f Int dEqInt in \ys. ...f'...
+tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
+ = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
+ tcGRHSsPat grhss pat_ty
+ ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
+ bind_fvs = placeHolderNames }) }
- = let f' = let f' = f Int dEqInt in \ys. ...f'...
- in \ys. ...f'...
-Etc.
-Solution: when typechecking the RHSs we always have in hand the
-*monomorphic* Ids for each binding. So we just need to make sure that
-if (Method f a d) shows up in the constraints emerging from (...f...)
-we just use the monomorphic Id. We achieve this by adding monomorphic Ids
-to the "givens" when simplifying constraints. That's what the "lies_avail"
-is doing.
+---------------------
+getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
+getMonoBindInfo tc_binds
+ = foldr (get_info . unLoc) [] tc_binds
+ where
+ get_info (TcFunBind info _ _ _) rest = info : rest
+ get_info (TcPatBind infos _ _ _) rest = infos ++ rest
+\end{code}
%************************************************************************
%* *
-\subsection{getTyVarsToGen}
+ Generalisation
%* *
%************************************************************************
\begin{code}
-generalise binder_names mbind tau_tvs lie_req sigs
- | not is_unrestricted -- RESTRICTED CASE
+generalise :: TopLevelFlag -> Bool
+ -> [MonoBindInfo] -> [Inst]
+ -> TcM ([TcTyVar], TcDictBinds, [TcId])
+generalise top_lvl is_unrestricted mono_infos lie_req
+ | not is_unrestricted -- RESTRICTED CASE
= -- Check signature contexts are empty
- checkTc (all is_mono_sig sigs)
- (restrictedBindCtxtErr binder_names) `thenTc_`
+ do { checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr bndrs)
-- Now simplify with exactly that set of tyvars
-- We have to squash those Methods
- tcSimplifyRestricted doc tau_tvs lie_req `thenTc` \ (qtvs, lie_free, binds) ->
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
+ tau_tvs lie_req
-- Check that signature type variables are OK
- checkSigsTyVars sigs `thenTc_`
+ ; final_qtvs <- checkSigsTyVars qtvs sigs
- returnTc (qtvs, lie_free, binds, [])
+ ; return (final_qtvs, binds, []) }
- | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
+ | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
= tcSimplifyInfer doc tau_tvs lie_req
- | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
- = -- CHECKING CASE: Unrestricted group, there are type signatures
- -- Check signature contexts are empty
- checkSigsCtxts sigs `thenTc` \ (sig_avails, sig_dicts) ->
-
+ | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
+ = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty
+ ; 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 Note [Polymorphic recursion])
+ local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
+ sig_avails = sig_lie ++ local_meths
+
-- Check that the needed dicts can be
-- expressed in terms of the signature ones
- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenTc` \ (forall_tvs, lie_free, dict_binds) ->
+ ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
-- Check that signature type variables are OK
- checkSigsTyVars sigs `thenTc_`
-
- returnTc (forall_tvs, lie_free, dict_binds, sig_dicts)
+ ; final_qtvs <- checkSigsTyVars forall_tvs sigs
+ ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
where
- is_unrestricted | opt_NoMonomorphismRestriction = True
- | otherwise = isUnRestrictedGroup tysig_names mbind
-
- tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- sigs]
- is_mono_sig (TySigInfo _ _ _ theta _ _ _ _) = null theta
+ bndrs = bndrNames mono_infos
+ sigs = [sig | (_, Just sig, _) <- mono_infos]
+ tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos
+ -- NB: exactTyVarsOfType; see Note [Silly type synonym]
+ -- near defn of TcType.exactTyVarsOfType
+ is_mono_sig sig = null (sig_theta sig)
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs
+
+ mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
+ sig_theta = theta, sig_loc = loc }) mono_id
+ = Method mono_id poly_id (mkTyVarTys tvs) theta loc
+\end{code}
- doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names
+unifyCtxts checks that 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).
------------------------
- -- 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 _ id1 sig_tvs theta1 _ _ _ src_loc : other_sigs)
- = tcAddSrcLoc src_loc $
- mapTc_ check_one other_sigs `thenTc_`
- if null theta1 then
- returnTc ([], []) -- Non-overloaded type signatures
- else
- newDicts SignatureOrigin theta1 `thenNF_Tc` \ 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
- returnTc (sig_avails, map instToId sig_dicts)
- where
- sig1_dict_tys = map mkPredTy theta1
- sig_meths = concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs]
+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
- check_one sig@(TySigInfo _ id _ theta _ _ _ src_loc)
- = tcAddErrCtxt (sigContextsCtxt id1 id) $
- checkTc (equalLength theta theta1) sigContextsErr `thenTc_`
- unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
+We unify them because, with polymorphic recursion, their types
+might not otherwise be related. This is a rather subtle issue.
-checkSigsTyVars sigs = mapTc_ check_one sigs
+\begin{code}
+unifyCtxts :: [TcSigInfo] -> TcM [Inst]
+unifyCtxts (sig1 : sigs) -- Argument is always non-empty
+ = do { mapM unify_ctxt sigs
+ ; newDictsAtLoc (sig_loc sig1) (sig_theta sig1) }
where
- check_one (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (ptext SLIT("When checking the type signature for")
- <+> quotes (ppr id)) $
- tcAddErrCtxtM (sigCtxt sig_tyvars sig_theta sig_tau) $
- checkSigTyVars sig_tyvars (idFreeTyVars id)
-\end{code}
+ theta1 = sig_theta sig1
+ unify_ctxt :: TcSigInfo -> TcM ()
+ unify_ctxt sig@(TcSigInfo { sig_theta = theta })
+ = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
+ addErrCtxt (sigContextsCtxt sig1 sig) $
+ unifyTheta theta1 theta
+
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs
+ = 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_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 zonkSigTyVar sig_tvs
+ ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
+ ; return zonked_tvs }
+ where
+ 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
+ = do { env0 <- tcInitTidyEnv
+ ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
+ (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
+ msg = ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
+ <+> ptext SLIT("is unified with another quantified type variable")
+ <+> quotes (ppr tidy_tv2)
+ ; failWithTcM (env2, msg) }
+ where
+\end{code}
+
@getTyVarsToGen@ decides what type variables to generalise over.
constrained tyvars. We don't use any of the results, except to
find which tyvars are constrained.
-\begin{code}
-isUnRestrictedGroup :: [Name] -- Signatures given for these
- -> RenamedMonoBinds
- -> Bool
-
-is_elem v vs = isIn "isUnResMono" v vs
-
-isUnRestrictedGroup sigs (PatMonoBind other _ _) = False
-isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (FunMonoBind v _ matches _) = isUnRestrictedMatch matches ||
- v `is_elem` sigs
-isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 &&
- isUnRestrictedGroup sigs mb2
-isUnRestrictedGroup sigs EmptyMonoBinds = True
-
-isUnRestrictedMatch (Match [] _ _ : _) = False -- No args => like a pattern binding
-isUnRestrictedMatch other = True -- Some args => a function binding
-\end{code}
+Note [Polymorphic recursion]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
+ * Bind any variable for which we have a type signature
+ to an Id with a polymorphic type. Then when type-checking
+ the RHSs we'll make a full polymorphic call.
-%************************************************************************
-%* *
-\subsection{tcMonoBind}
-%* *
-%************************************************************************
+This fine, but if you aren't a bit careful you end up with a horrendous
+amount of partial application and (worse) a huge space leak. For example:
-@tcMonoBinds@ deals with a single @MonoBind@.
-The signatures have been dealt with already.
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
-\begin{code}
-tcMonoBinds :: RenamedMonoBinds
- -> [TcSigInfo]
- -> RecFlag
- -> TcM (TcMonoBinds,
- LIE, -- LIE required
- [Name], -- Bound names
- [TcId]) -- Corresponding monomorphic bound things
-
-tcMonoBinds mbinds tc_ty_sigs is_rec
- = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) ->
- let
- id_list = bagToList ids
- (names, mono_ids) = unzip id_list
-
- -- This last defn is the key one:
- -- extend the val envt with bindings for the
- -- things bound in this group, overriding the monomorphic
- -- ids with the polymorphic ones from the pattern
- extra_val_env = case is_rec of
- Recursive -> map mk_bind id_list
- NonRecursive -> []
- in
- -- Don't know how to deal with pattern-bound existentials yet
- checkTc (isEmptyBag tvs && isEmptyBag lie_avail)
- (existentialExplode mbinds) `thenTc_`
-
- -- *Before* checking the RHSs, but *after* checking *all* the patterns,
- -- extend the envt with bindings for all the bound ids;
- -- and *then* override with the polymorphic Ids from the signatures
- -- That is the whole point of the "complete_it" stuff.
- --
- -- There's a further wrinkle: we have to delay extending the environment
- -- until after we've dealt with any pattern-bound signature type variables
- -- Consider f (x::a) = ...f...
- -- We're going to check that a isn't unified with anything in the envt,
- -- so f itself had better not be! So we pass the envt binding f into
- -- complete_it, which extends the actual envt in TcMatches.tcMatch, after
- -- dealing with the signature tyvars
+If we don't take care, after typechecking we get
- complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) ->
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
- returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids)
- where
+Notice the the stupid construction of (f a d), which is of course
+identical to the function we're executing. In this case, the
+polymorphic recursion isn't being used (but that's a very common case).
+This can lead to a massive space leak, from the following top-level defn
+(post-typechecking)
+
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
+
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
+
+ ff = f Int dEqInt
+
+ = let f' = f Int dEqInt in \ys. ...f'...
+
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
+
+Etc.
+
+NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
+which would make the space leak go away in this case
+
+Solution: when typechecking the RHSs we always have in hand the
+*monomorphic* Ids for each binding. So we just need to make sure that
+if (Method f a d) shows up in the constraints emerging from (...f...)
+we just use the monomorphic Id. We achieve this by adding monomorphic Ids
+to the "givens" when simplifying constraints. That's what the "lies_avail"
+is doing.
+
+Then we get
+
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
- mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of
- Nothing -> (name, mono_id)
- Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id)
-
- tc_mb_pats EmptyMonoBinds
- = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
-
- tc_mb_pats (AndMonoBinds mb1 mb2)
- = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) ->
- tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) ->
- let
- complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) ->
- complete_it2 xve `thenTc` \ (mb2', lie2) ->
- returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2)
- in
- returnTc (complete_it,
- lie_req1 `plusLIE` lie_req2,
- tvs1 `unionBags` tvs2,
- ids1 `unionBags` ids2,
- lie_avail1 `plusLIE` lie_avail2)
-
- tc_mb_pats (FunMonoBind name inf matches locn)
- = (case maybeSig tc_ty_sigs name of
- Just (TySigInfo _ _ _ _ _ mono_id _ _)
- -> returnNF_Tc mono_id
- Nothing -> newLocalName name `thenNF_Tc` \ bndr_name ->
- newTyVarTy openTypeKind `thenNF_Tc` \ bndr_ty ->
- -- NB: not a 'hole' tyvar; since there is no type
- -- signature, we revert to ordinary H-M typechecking
- -- which means the variable gets an inferred tau-type
- returnNF_Tc (mkLocalId bndr_name bndr_ty)
- ) `thenNF_Tc` \ bndr_id ->
- let
- bndr_ty = idType bndr_id
- complete_it xve = tcAddSrcLoc locn $
- tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) ->
- returnTc (FunMonoBind bndr_id inf matches' locn, lie)
- in
- returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
-
- tc_mb_pats bind@(PatMonoBind pat grhss locn)
- = tcAddSrcLoc locn $
- newHoleTyVarTy `thenNF_Tc` \ pat_ty ->
-
- -- 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.
-
- tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
- let
- complete_it xve = tcAddSrcLoc locn $
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- tcExtendLocalValEnv xve $
- tcGRHSs PatBindRhs grhss pat_ty `thenTc` \ (grhss', lie) ->
- returnTc (PatMonoBind pat' grhss' locn, lie)
- in
- returnTc (complete_it, lie_req, tvs, ids, lie_avail)
-
- -- 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_mb_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 `thenNF_Tc` \ bndr_name ->
- tcMonoPatBndr bndr_name pat_ty
-
- Just (TySigInfo _ _ _ _ _ mono_id _ _)
- -> tcAddSrcLoc (getSrcLoc name) $
- tcSubPat pat_ty (idType mono_id) `thenTc` \ (co_fn, lie) ->
- returnTc (co_fn, lie, mono_id)
-\end{code}
%************************************************************************
%* *
-\subsection{SPECIALIZE pragmas}
+ Signatures
%* *
%************************************************************************
-@tcSpecSigs@ munches up the specialisation "signatures" that arise through *user*
-pragmas. It is convenient for them to appear in the @[RenamedSig]@
-part of a binding because then the same machinery can be used for
-moving them into place as is done for type signatures.
-
-They look like this:
-
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b #-}
-\end{verbatim}
-
-For this we generate:
-\begin{verbatim}
- f* = /\ b -> let d1 = ...
- in f Int b d1
-\end{verbatim}
-
-where f* is a SpecPragmaId. The **sole** purpose of SpecPragmaIds is to
-retain a right-hand-side that the simplifier will otherwise discard as
-dead code... the simplifier has a flag that tells it not to discard
-SpecPragmaId bindings.
-
-In this case the f* retains a call-instance of the overloaded
-function, f, (including appropriate dictionaries) so that the
-specialiser will subsequently discover that there's a call of @f@ at
-Int, and will create a specialisation for @f@. After that, the
-binding for @f*@ can be discarded.
-
-We used to have a form
- {-# SPECIALISE f :: <type> = g #-}
-which promised that g implemented f at <type>, but we do that with
-a RULE now:
- {-# SPECIALISE (f::<type) = g #-}
+Type signatures are tricky. See Note [Signature skolems] in TcType
+
+@tcSigs@ checks the signatures for validity, and returns a list of
+{\em freshly-instantiated} signatures. That is, the types are already
+split up, and have fresh type variables installed. All non-type-signature
+"RenamedSigs" are ignored.
+
+The @TcSigInfo@ contains @TcTypes@ because they are unified with
+the variable's type, and after that checked to see whether they've
+been instantiated.
\begin{code}
-tcSpecSigs :: [RenamedSig] -> TcM (TcMonoBinds, LIE)
-tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
- = -- SPECIALISE f :: forall b. theta => tau = g
- tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
-
- -- Get and instantiate its alleged specialised type
- tcHsSigType (FunSigCtxt name) poly_ty `thenTc` \ sig_ty ->
-
- -- Check that f has a more general type, and build a RHS for
- -- the spec-pragma-id at the same time
- tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) ->
-
- -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
- tcSimplifyToDicts spec_lie `thenTc` \ (spec_dicts, spec_binds) ->
-
- -- Just specialise "f" by building a SpecPragmaId binding
- -- It is the thing that makes sure we don't prematurely
- -- dead-code-eliminate the binding we are really interested in.
- newLocalName name `thenNF_Tc` \ spec_name ->
- let
- spec_bind = VarMonoBind (mkSpecPragmaId spec_name sig_ty)
- (mkHsLet spec_binds spec_expr)
- in
+type TcSigFun = Name -> Maybe (LSig Name)
- -- Do the rest and combine
- tcSpecSigs sigs `thenTc` \ (binds_rest, lie_rest) ->
- returnTc (binds_rest `andMonoBinds` spec_bind,
- lie_rest `plusLIE` mkLIE spec_dicts)
+mkSigFun :: [LSig Name] -> TcSigFun
+-- Search for a particular type signature
+-- Precondition: the sigs are all type sigs
+-- Precondition: no duplicates
+mkSigFun sigs = lookupNameEnv env
+ where
+ env = mkNameEnv [(expectJust "mkSigFun" (sigName sig), sig) | sig <- sigs]
+
+---------------
+data TcSigInfo
+ = TcSigInfo {
+ sig_id :: TcId, -- *Polymorphic* binder for this value...
+
+ sig_scoped :: [Name], -- Names for any scoped type variables
+ -- Invariant: correspond 1-1 with an initial
+ -- segment of sig_tvs (see Note [Scoped])
+
+ sig_tvs :: [TcTyVar], -- Instantiated type variables
+ -- See Note [Instantiate sig]
+
+ sig_theta :: TcThetaType, -- Instantiated theta
+ sig_tau :: TcTauType, -- Instantiated tau
+ sig_loc :: InstLoc -- The location of the signature
+ }
+
+-- Note [Scoped]
+-- There may be more instantiated type variables than scoped
+-- ones. For example:
+-- type T a = forall b. b -> (a,b)
+-- f :: forall c. T c
+-- Here, the signature for f will have one scoped type variable, c,
+-- but two instantiated type variables, c' and b'.
+--
+-- We assume that the scoped ones are at the *front* of sig_tvs,
+-- and remember the names from the original HsForAllTy in sig_scoped
+
+-- Note [Instantiate sig]
+-- It's vital to instantiate a type signature with fresh variable.
+-- For example:
+-- type S = forall a. a->a
+-- f,g :: S
+-- f = ...
+-- g = ...
+-- Here, we must use distinct type variables when checking f,g's right hand sides.
+-- (Instantiation is only necessary because of type synonyms. Otherwise,
+-- it's all cool; each signature has distinct type variables from the renamer.)
+
+instance Outputable TcSigInfo where
+ ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
+ = ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
+\end{code}
-tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
-tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE)
+\begin{code}
+tcTySig :: LSig Name -> TcM TcId
+tcTySig (L span (TypeSig (L _ name) ty))
+ = setSrcSpan span $
+ do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkLocalId name sigma_ty) }
+
+-------------------
+tcInstSig_maybe :: Maybe (LSig Name) -> TcM (Maybe TcSigInfo)
+-- Instantiate with *meta* type variables;
+-- this signature is part of a multi-signature group
+tcInstSig_maybe Nothing = return Nothing
+tcInstSig_maybe (Just sig) = do { tc_sig <- tcInstSig False sig
+ ; return (Just tc_sig) }
+
+tcInstSig :: Bool -> LSig Name -> TcM TcSigInfo
+-- Instantiate the signature, with either skolems or meta-type variables
+-- depending on the use_skols boolean
+--
+-- We always instantiate with freshs uniques,
+-- although we keep the same print-name
+--
+-- type T = forall a. [a] -> [a]
+-- f :: T;
+-- f = g where { g :: T; g = <rhs> }
+--
+-- We must not use the same 'a' from the defn of T at both places!!
+
+tcInstSig use_skols (L loc (TypeSig (L _ name) hs_ty))
+ = setSrcSpan loc $
+ do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
+ -- scope when starting the binding group
+ ; let skol_info = SigSkol (FunSigCtxt name)
+ inst_tyvars | use_skols = tcInstSkolTyVars skol_info
+ | otherwise = tcInstSigTyVars skol_info
+ ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
+ ; loc <- getInstLoc (SigOrigin skol_info)
+ ; return (TcSigInfo { sig_id = poly_id,
+ sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
+ sig_scoped = scoped_names, sig_loc = loc }) }
+ -- Note that the scoped_names and the sig_tvs will have
+ -- different Names. That's quite ok; when we bring the
+ -- scoped_names into scope, we just bind them to the sig_tvs
+ where
+ -- 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.)
+ -- We also only have scoped type variables when we are instantiating
+ -- with true skolems
+ scoped_names = case (use_skols, hs_ty) of
+ (True, L _ (HsForAllTy Explicit tvs _ _)) -> hsLTyVarNames tvs
+ other -> []
+
+-------------------
+isUnRestrictedGroup :: [LHsBind Name] -> TcSigFun -> TcM Bool
+isUnRestrictedGroup binds sig_fn
+ = do { mono_restriction <- doptM Opt_MonomorphismRestriction
+ ; return (not mono_restriction || all_unrestricted) }
+ where
+ all_unrestricted = all (unrestricted . unLoc) binds
+ has_sig n = isJust (sig_fn n)
+
+ unrestricted (PatBind {}) = False
+ unrestricted (VarBind { var_id = v }) = has_sig v
+ unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
+ || has_sig (unLoc v)
+
+ unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
+ -- No args => like a pattern binding
+ unrestricted_match other = True
+ -- Some args => a function binding
\end{code}
\begin{code}
-patMonoBindsCtxt bind
- = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
-
------------------------------------------------
-valSpecSigCtxt v ty
- = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
- nest 4 (ppr v <+> dcolon <+> ppr ty)]
+-- 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)
-----------------------------------------------
-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
- = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:"))
- 4 (ppr mbind)
-----------------------------------------------
-existentialExplode mbinds
- = hang (vcat [text "My brain just exploded.",
- text "I can't handle pattern bindings for existentially-quantified constructors.",
- text "In the binding group"])
- 4 (ppr mbinds)
+unboxedTupleErr name ty
+ = hang (ptext SLIT("Illegal binding of unboxed tuple"))
+ 4 (ppr name <+> dcolon <+> ppr ty)
-----------------------------------------------
restrictedBindCtxtErr binder_names
genCtxt binder_names
= ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
-
--- Used in error messages
-pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
projects / ghc-hetmet.git / blobdiff