%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBindsAndThen,
- tcPragmaSigs, checkSigTyVars, tcBindWithSigs,
- sigCtxt, TcSigInfo(..) ) where
+module TcBinds ( tcLocalBinds, tcTopBinds,
+ tcHsBootSigs, tcMonoBinds,
+ TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
+ TcSigInfo(..),
+ badBootDeclErr ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
-
-import HsSyn ( HsBinds(..), MonoBinds(..), Sig(..), InPat(..),
- collectMonoBinders
- )
-import RnHsSyn ( RenamedHsBinds, RenamedSig(..),
- RenamedMonoBinds
+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 TcHsSyn ( TcHsBinds, TcMonoBinds,
- TcIdOcc(..), TcIdBndr,
- tcIdType
- )
-
-import TcMonad
-import Inst ( Inst, LIE, emptyLIE, plusLIE, plusLIEs, InstOrigin(..),
- newDicts, tyVarsOfInst, instToId, newMethodWithGivenTy,
- zonkInst, pprInsts
- )
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newLocalId,
- tcGetGlobalTyVars, tcExtendGlobalTyVars
- )
-import TcMatches ( tcMatchesFun )
-import TcSimplify ( tcSimplify, tcSimplifyAndCheck )
-import TcMonoType ( tcHsType )
-import TcPat ( tcPat )
+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 TcType ( TcType, TcThetaType, TcTauType,
- TcTyVarSet, TcTyVar,
- newTyVarTy, newTcTyVar, tcInstSigType, tcInstSigTcType,
- zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVar
- )
-import Unify ( unifyTauTy, unifyTauTyLists )
-
-import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind )
-import Id ( GenId, idType, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( maybeToBool, assocMaybe )
-import Name ( getOccName, getSrcLoc, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes,
- splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy,
- splitRhoTy, mkForAllTy, splitForAllTys )
-import TyVar ( GenTyVar, TyVar, tyVarKind, mkTyVarSet, minusTyVarSet, emptyTyVarSet,
- elementOfTyVarSet, unionTyVarSets, tyVarSetToList )
-import Bag ( bagToList, foldrBag, )
-import Util ( isIn, hasNoDups, assoc )
-import Unique ( Unique )
-import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
-import SrcLoc ( SrcLoc )
+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 NameEnv
+import VarSet
+import SrcLoc ( Located(..), unLoc, getLoc )
+import Bag
+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}
-tcTopBindsAndThen, tcBindsAndThen
- :: (RecFlag -> TcMonoBinds s -> this -> that) -- Combinator
- -> RenamedHsBinds
- -> TcM s (this, LIE s)
- -> TcM s (that, LIE s)
-
-tcTopBindsAndThen = tc_binds_and_then TopLevel
-tcBindsAndThen = tc_binds_and_then NotTopLevel
-
-tc_binds_and_then top_lvl combiner binds do_next
- = tcBinds top_lvl binds `thenTc` \ (mbinds1, binds_lie, env, ids) ->
- tcSetEnv env $
-
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie) ->
-
- -- Create specialisations of functions bound here
- -- Nota Bene: we glom the bindings all together in a single
- -- recursive group ("recursive" passed to combiner, below)
- -- so that we can do thsi bindInsts thing once for all the bindings
- -- and the thing inside. This saves a quadratic-cost algorithm
- -- when there's a long sequence of bindings.
- bindInstsOfLocalFuns (binds_lie `plusLIE` thing_lie) ids `thenTc` \ (final_lie, mbinds2) ->
-
- -- All done
- let
- final_mbinds = mbinds1 `AndMonoBinds` mbinds2
- in
- returnTc (combiner Recursive final_mbinds thing, final_lie)
-
-tcBinds :: TopLevelFlag
- -> RenamedHsBinds
- -> TcM s (TcMonoBinds s, LIE s, TcEnv s, [TcIdBndr s])
- -- The envt is the envt with binders in scope
- -- The binders are those bound by this group of bindings
-
-tcBinds top_lvl EmptyBinds
- = tcGetEnv `thenNF_Tc` \ env ->
- returnTc (EmptyMonoBinds, emptyLIE, env, [])
-
- -- Short-cut for the rather common case of an empty bunch of bindings
-tcBinds top_lvl (MonoBind EmptyMonoBinds sigs is_rec)
- = tcGetEnv `thenNF_Tc` \ env ->
- returnTc (EmptyMonoBinds, emptyLIE, env, [])
-
-tcBinds top_lvl (ThenBinds binds1 binds2)
- = tcBinds top_lvl binds1 `thenTc` \ (mbinds1, lie1, env1, ids1) ->
- tcSetEnv env1 $
- tcBinds top_lvl binds2 `thenTc` \ (mbinds2, lie2, env2, ids2) ->
- returnTc (mbinds1 `AndMonoBinds` mbinds2, lie1 `plusLIE` lie2, env2, ids1++ids2)
-
-tcBinds top_lvl (MonoBind bind sigs is_rec)
- = fixTc (\ ~(prag_info_fn, _) ->
- -- This is the usual prag_info fix; the PragmaInfo field of an Id
- -- is not inspected till ages later in the compiler, so there
- -- should be no black-hole problems here.
-
- -- TYPECHECK THE SIGNATURES
- mapTc (tcTySig prag_info_fn) ty_sigs `thenTc` \ tc_ty_sigs ->
-
- tcBindWithSigs top_lvl binder_names bind
- tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
-
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv binder_names poly_ids $
-
- -- Build bindings and IdInfos corresponding to user pragmas
- tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
-
- -- Catch the environment and return
- tcGetEnv `thenNF_Tc` \ env ->
- returnTc (prag_info_fn, (poly_binds `AndMonoBinds` prag_binds,
- poly_lie `plusLIE` prag_lie,
- env, poly_ids)
- ) ) `thenTc` \ (_, result) ->
- returnTc result
+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
+ = 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
- binder_names = map fst (bagToList (collectMonoBinders bind))
- ty_sigs = [sig | sig@(Sig name _ _) <- sigs]
-\end{code}
+ 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)
+
+-- 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) }
+
+ go1 (AcyclicSCC bind) = tc_binds NonRecursive (unitBag bind)
+ go1 (CyclicSCC binds) = tc_binds Recursive (listToBag binds)
+
+ tc_binds rec_tc binds = tcPolyBinds top_lvl Recursive rec_tc sig_fn prag_fn binds
-An aside. The original version of @tcBindsAndThen@ which lacks a
-combiner function, appears below. Though it is perfectly well
-behaved, it cannot be typed by Haskell, because the recursive call is
-at a different type to the definition itself. There aren't too many
-examples of this, which is why I thought it worth preserving! [SLPJ]
+------------------------
+mkEdges :: TcSigFun -> LHsBinds Name
+ -> [(LHsBind Name, BKey, [BKey])]
+
+type BKey = Int -- Just number off the bindings
+
+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
+
+ -- 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
+
+ ; traceTc (text "binding:" <+> ppr (zonked_poly_ids `zip` map idType zonked_poly_ids))
+
+ ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
+ dict_ids exports
+ (dict_binds `unionBags` binds')
+
+ ; return ([unitBag abs_bind], zonked_poly_ids)
+ } }
+
+
+--------------
+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
-\begin{pseudocode}
-tcBindsAndThen
- :: RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty))
- -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
+pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
-tcBindsAndThen EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
+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)
-tcBindsAndThen (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
+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
+ msg | unlifted = ptext SLIT("bindings for unlifted types")
+ | otherwise = ptext SLIT("bang-pattern bindings")
-tcBindsAndThen (MonoBind bind sigs is_rec) do_next
- = tcBindAndThen bind sigs do_next
-\end{pseudocode}
+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}
%************************************************************************
%* *
-\subsection{tcBindWithSigs}
+\subsection{tcMonoBind}
%* *
%************************************************************************
-@tcBindWithSigs@ deals with a single binding group. It does generalisation,
-so all the clever stuff is in here.
+@tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
+The signatures have been dealt with already.
-* binder_names and mbind must define the same set of Names
+\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
-* The Names in tc_ty_sigs must be a subset of binder_names
+tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
+ = do { mb_sigs <- mapM (tcInstSig_maybe . sig_fn) names
-* The Ids in tc_ty_sigs don't necessarily have to have the same name
- as the Name in the tc_ty_sig
+ ; 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
-\begin{code}
-tcBindWithSigs
- :: TopLevelFlag
- -> [Name]
- -> RenamedMonoBinds
- -> [TcSigInfo s]
- -> RecFlag
- -> (Name -> PragmaInfo)
- -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s])
-
-tcBindWithSigs top_lvl binder_names mbind tc_ty_sigs is_rec prag_info_fn
- = recoverTc (
- -- If typechecking the binds fails, then return with each
- -- signature-less binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
- let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- 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 -> mkUserId name forall_a_a NoPragmaInfo -- No signature
- in
- returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
- ) $
-
- -- Create a new identifier for each binder, with each being given
- -- a fresh unique, and a type-variable type.
- -- For "mono_lies" see comments about polymorphic recursion at the
- -- end of the function.
- mapAndUnzipNF_Tc mk_mono_id binder_names `thenNF_Tc` \ (mono_lies, mono_ids) ->
- let
- mono_lie = plusLIEs mono_lies
- mono_id_tys = map idType mono_ids
- in
+ 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.
- -- TYPECHECK THE BINDINGS
- tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) ->
+ -- 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) }
- -- CHECK THAT THE SIGNATURES MATCH
- -- (must do this before getTyVarsToGen)
- checkSigMatch tc_ty_sigs `thenTc` \ sig_theta ->
-
- -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen
- -- The tyvars_not_to_gen are free in the environment, and hence
- -- candidates for generalisation, but sometimes the monomorphism
- -- restriction means we can't generalise them nevertheless
- getTyVarsToGen is_unrestricted mono_id_tys lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
-
- -- DEAL WITH TYPE VARIABLE KINDS
- -- **** This step can do unification => keep other zonking after this ****
- mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
- let
- real_tyvars_to_gen = mkTyVarSet real_tyvars_to_gen_list
- -- It's important that the final list
- -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
- -- zonked, *including boxity*, because they'll be included in the forall types of
- -- the polymorphic Ids, and instances of these Ids will be generated from them.
- --
- -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass
- -- real_tyvars_to_gen
- --
- in
-
- -- SIMPLIFY THE LIE
- tcExtendGlobalTyVars (tyVarSetToList tyvars_not_to_gen) (
- if null tc_ty_sigs then
- -- No signatures, so just simplify the lie
- -- NB: no signatures => no polymorphic recursion, so no
- -- need to use mono_lies (which will be empty anyway)
- tcSimplify (text "tcBinds1" <+> ppr binder_names)
- top_lvl real_tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) ->
- returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
-
- else
- zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' ->
- newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) ->
- -- It's important that sig_theta is zonked, because
- -- dict_id is later used to form the type of the polymorphic thing,
- -- and forall-types must be zonked so far as their bound variables
- -- are concerned
-
- let
- -- The "givens" is the stuff available. We get that from
- -- the context of the type signature, BUT ALSO the mono_lie
- -- so that polymorphic recursion works right (see comments at end of fn)
- givens = dicts_sig `plusLIE` mono_lie
- in
-
- -- Check that the needed dicts can be expressed in
- -- terms of the signature ones
- tcAddErrCtxt (bindSigsCtxt tysig_names) $
- tcSimplifyAndCheck
- (ptext SLIT("type signature for") <+>
- hsep (punctuate comma (map (quotes . ppr) binder_names)))
- real_tyvars_to_gen givens lie `thenTc` \ (lie_free, dict_binds) ->
-
- returnTc (lie_free, dict_binds, dict_ids)
-
- ) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
-
- ASSERT( not (any (isUnboxedTypeKind . tyVarKind) real_tyvars_to_gen_list) )
- -- 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.
-
- -- BUILD THE POLYMORPHIC RESULT IDs
- zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
- let
- exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types
- dict_tys = map tcIdType dicts_bound
-
- mk_export binder_name mono_id zonked_mono_id_ty
- | maybeToBool maybe_sig = (sig_tyvars, TcId sig_poly_id, TcId mono_id)
- | otherwise = (real_tyvars_to_gen_list, TcId poly_id, TcId mono_id)
- where
- maybe_sig = maybeSig tc_ty_sigs binder_name
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _) = maybe_sig
- poly_id = mkUserId binder_name poly_ty (prag_info_fn binder_name)
- poly_ty = mkForAllTys real_tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty
- -- 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
+ ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
+ tcInfer tc_pat
- -- BUILD RESULTS
- returnTc (
- AbsBinds real_tyvars_to_gen_list
- dicts_bound
- exports
- (dict_binds `AndMonoBinds` mbind'),
- lie_free,
- [poly_id | (_, TcId poly_id, _) <- exports]
- )
+ ; return (TcPatBind infos pat' grhss pat_ty) }
where
- no_of_binders = length binder_names
-
- mk_mono_id binder_name
- | theres_a_signature -- There's a signature; and it's overloaded,
- && not (null sig_theta) -- so make a Method
- = tcAddSrcLoc sig_loc $
- newMethodWithGivenTy SignatureOrigin
- (TcId poly_id) (mkTyVarTys sig_tyvars)
- sig_theta sig_tau `thenNF_Tc` \ (mono_lie, TcId mono_id) ->
- -- A bit turgid to have to strip the TcId
- returnNF_Tc (mono_lie, mono_id)
-
- | otherwise -- No signature or not overloaded;
- = tcAddSrcLoc (getSrcLoc binder_name) $
- (if theres_a_signature then
- returnNF_Tc sig_tau -- Non-overloaded signature; use its type
- else
- newTyVarTy kind -- No signature; use a new type variable
- ) `thenNF_Tc` \ mono_id_ty ->
-
- newLocalId (getOccName binder_name) mono_id_ty `thenNF_Tc` \ mono_id ->
- returnNF_Tc (emptyLIE, mono_id)
- where
- maybe_sig = maybeSig tc_ty_sigs binder_name
- theres_a_signature = maybeToBool maybe_sig
- Just (TySigInfo name poly_id sig_tyvars sig_theta sig_tau sig_loc) = maybe_sig
-
- tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
- is_unrestricted = isUnRestrictedGroup tysig_names mbind
-
- kind = case is_rec of
- Recursive -> mkBoxedTypeKind -- Recursive, so no unboxed types
- NonRecursive -> mkTypeKind -- Non-recursive, so we permit unboxed types
-\end{code}
+ names = collectPatBinders pat
-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.
+tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
+ -- AbsBind, VarBind impossible
-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:
+-------------------
+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 }) }
- f :: Eq a => [a] -> [a]
- f xs = ...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 }) }
-If we don't take care, after typechecking we get
- f = /\a -> \d::Eq a -> let f' = f a d
- in
- \ys:[a] -> ...f'...
+---------------------
+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}
-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 ins't being used (but that's a very common case).
-This can lead to a massive space leak, from the following top-level defn:
+%************************************************************************
+%* *
+ Generalisation
+%* *
+%************************************************************************
- ff :: [Int] -> [Int]
- ff = f dEqInt
+\begin{code}
+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
+ do { checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr bndrs)
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
+ tau_tvs lie_req
+
+ -- Check that signature type variables are OK
+ ; final_qtvs <- checkSigsTyVars qtvs sigs
+
+ ; return (final_qtvs, binds, []) }
+
+ | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
+ = tcSimplifyInfer doc tau_tvs lie_req
+
+ | 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
+ ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
+
+ -- Check that signature type variables are OK
+ ; final_qtvs <- checkSigsTyVars forall_tvs sigs
-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.
+ ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
+ where
+ 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}
-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. Thats' what the "mono_lies"
-is doing.
+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).
+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
-%************************************************************************
-%* *
-\subsection{getTyVarsToGen}
-%* *
-%************************************************************************
+We unify them because, with polymorphic recursion, their types
+might not otherwise be related. This is a rather subtle issue.
+
+\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
+ 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)
-@getTyVarsToGen@ decides what type variables generalise over.
+ 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.
For a "restricted group" -- see the monomorphism restriction
for a definition -- we bind no dictionaries, and
Another, more common, example is when there's a Method inst in
the LIE, whose type might very well involve non-overloaded
type variables.
+ [NOTE: Jan 2001: I don't understand the problem here so I'm doing
+ the simple thing instead]
(b) On the other hand, we mustn't generalise tyvars which are constrained,
because we are going to pass on out the unmodified LIE, with those
constrained tyvars. We don't use any of the results, except to
find which tyvars are constrained.
-\begin{code}
-getTyVarsToGen is_unrestricted mono_id_tys lie
- = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
- zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys ->
- let
- tyvars_to_gen = tyVarsOfTypes zonked_mono_id_tys `minusTyVarSet` free_tyvars
- in
- if is_unrestricted
- then
- returnTc (emptyTyVarSet, tyvars_to_gen)
- else
- tcSimplify (text "getTVG") NotTopLevel tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
- let
- -- ASSERT: dicts_sig is already zonked!
- constrained_tyvars = foldrBag (unionTyVarSets . tyVarsOfInst) emptyTyVarSet constrained_dicts
- reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars
- in
- returnTc (constrained_tyvars, reduced_tyvars_to_gen)
-\end{code}
-
-
-\begin{code}
-isUnRestrictedGroup :: [Name] -- Signatures given for these
- -> RenamedMonoBinds
- -> Bool
-
-is_elem v vs = isIn "isUnResMono" v vs
-
-isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (PatMonoBind other _ _) = False
-isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True
-isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 &&
- isUnRestrictedGroup sigs mb2
-isUnRestrictedGroup sigs EmptyMonoBinds = True
-\end{code}
-
-@defaultUncommittedTyVar@ checks for generalisation over unboxed
-types, and defaults any TypeKind TyVars to BoxedTypeKind.
-
-\begin{code}
-defaultUncommittedTyVar tyvar
- | isTypeKind (tyVarKind tyvar)
- = newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ boxed_tyvar ->
- unifyTauTy (mkTyVarTy boxed_tyvar) (mkTyVarTy tyvar) `thenTc_`
- returnTc boxed_tyvar
-
- | otherwise
- = returnTc tyvar
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{tcMonoBind}
-%* *
-%************************************************************************
-
-@tcMonoBinds@ deals with a single @MonoBind@.
-The signatures have been dealt with already.
-
-\begin{code}
-tcMonoBinds :: RenamedMonoBinds
- -> [Name] -> [TcIdBndr s]
- -> [TcSigInfo s]
- -> TcM s (TcMonoBinds s, LIE s)
-
-tcMonoBinds mbind binder_names mono_ids tc_ty_sigs
- = tcExtendLocalValEnv binder_names mono_ids (
- tc_mono_binds mbind
- )
- where
- sig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
- sig_ids = [id | (TySigInfo _ id _ _ _ _) <- tc_ty_sigs]
-
- tc_mono_binds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
-
- tc_mono_binds (AndMonoBinds mb1 mb2)
- = tc_mono_binds mb1 `thenTc` \ (mb1a, lie1) ->
- tc_mono_binds mb2 `thenTc` \ (mb2a, lie2) ->
- returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
-
- tc_mono_binds (FunMonoBind name inf matches locn)
- = tcAddSrcLoc locn $
- tcLookupLocalValueOK "tc_mono_binds" name `thenNF_Tc` \ id ->
-
- -- Before checking the RHS, extend the envt with
- -- bindings for the *polymorphic* Ids from any type signatures
- tcExtendLocalValEnv sig_names sig_ids $
- tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
-
- returnTc (FunMonoBind (TcId id) inf matches' locn, lie)
-
- tc_mono_binds bind@(PatMonoBind pat grhss_and_binds locn)
- = tcAddSrcLoc locn $
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
-
- -- Before checking the RHS, but after the pattern, extend the envt with
- -- bindings for the *polymorphic* Ids from any type signatures
- tcExtendLocalValEnv sig_names sig_ids $
- tcGRHSsAndBinds pat_ty grhss_and_binds `thenTc` \ (grhss_and_binds2, lie) ->
- returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
- plusLIE lie_pat lie)
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Signatures}
-%* *
-%************************************************************************
-
-@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}
-data TcSigInfo s
- = TySigInfo
- Name -- N, the Name in corresponding binding
- (TcIdBndr s) -- *Polymorphic* binder for this value...
- -- Usually has name = N, but doesn't have to.
- [TcTyVar s]
- (TcThetaType s)
- (TcTauType s)
- SrcLoc
-
-
-maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s)
- -- Search for a particular signature
-maybeSig [] name = Nothing
-maybeSig (sig@(TySigInfo sig_name _ _ _ _ _) : sigs) name
- | name == sig_name = Just sig
- | otherwise = maybeSig sigs name
-\end{code}
-
-
-\begin{code}
-tcTySig :: (Name -> PragmaInfo)
- -> RenamedSig
- -> TcM s (TcSigInfo s)
-
-tcTySig prag_info_fn (Sig v ty src_loc)
- = tcAddSrcLoc src_loc $
- tcHsType ty `thenTc` \ sigma_ty ->
-
- -- Convert from Type to TcType
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_tc_ty ->
- let
- poly_id = mkUserId v sigma_tc_ty (prag_info_fn v)
- in
- -- Instantiate this type
- -- It's important to do this even though in the error-free case
- -- we could just split the sigma_tc_ty (since the tyvars don't
- -- unified with anything). But in the case of an error, when
- -- the tyvars *do* get unified with something, we want to carry on
- -- typechecking the rest of the program with the function bound
- -- to a pristine type, namely sigma_tc_ty
- tcInstSigTcType sigma_tc_ty `thenNF_Tc` \ (tyvars, rho) ->
- let
- (theta, tau) = splitRhoTy rho
- -- This splitSigmaTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- returnTc (TySigInfo v poly_id tyvars theta tau src_loc)
-\end{code}
-
-@checkSigMatch@ does the next step in checking signature matching.
-The tau-type part has already been unified. What we do here is to
-check that this unification has not over-constrained the (polymorphic)
-type variables of the original signature type.
-
-The error message here is somewhat unsatisfactory, but it'll do for
-now (ToDo).
-
-\begin{code}
-checkSigMatch []
- = returnTc (error "checkSigMatch")
-
-checkSigMatch tc_ty_sigs@( sig1@(TySigInfo _ id1 _ theta1 _ _) : all_sigs_but_first )
- = -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK
- -- Doesn't affect substitution
- mapTc check_one_sig tc_ty_sigs `thenTc_`
+Note [Polymorphic recursion]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
- -- 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
- mapTc check_one_cxt all_sigs_but_first `thenTc_`
+ * 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.
- returnTc theta1
- where
- sig1_dict_tys = mk_dict_tys theta1
- n_sig1_dict_tys = length sig1_dict_tys
-
- check_one_cxt sig@(TySigInfo _ id _ theta _ src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (sigContextsCtxt id1 id) $
- checkTc (length this_sig_dict_tys == n_sig1_dict_tys)
- sigContextsErr `thenTc_`
- unifyTauTyLists sig1_dict_tys this_sig_dict_tys
- where
- this_sig_dict_tys = mk_dict_tys theta
-
- check_one_sig (TySigInfo name id sig_tyvars _ sig_tau src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (sigCtxt id) $
- checkSigTyVars sig_tyvars sig_tau
-
- mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta]
-\end{code}
+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:
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
-@checkSigTyVars@ is used after the type in a type signature has been unified with
-the actual type found. It then checks that the type variables of the type signature
-are
- (a) still all type variables
- eg matching signature [a] against inferred type [(p,q)]
- [then a will be unified to a non-type variable]
+If we don't take care, after typechecking we get
- (b) still all distinct
- eg matching signature [(a,b)] against inferred type [(p,p)]
- [then a and b will be unified together]
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
- (c) not mentioned in the environment
- eg the signature for f in this:
+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)
- g x = ... where
- f :: a->[a]
- f y = [x,y]
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
- Here, f is forced to be monorphic by the free occurence of x.
+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.
-Before doing this, the substitution is applied to the signature type variable.
+ ff = f Int dEqInt
-We used to have the notion of a "DontBind" type variable, which would
-only be bound to itself or nothing. Then points (a) and (b) were
-self-checking. But it gave rise to bogus consequential error messages.
-For example:
+ = let f' = f Int dEqInt in \ys. ...f'...
- f = (*) -- Monomorphic
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
- g :: Num a => a -> a
- g x = f x x
+Etc.
-Here, we get a complaint when checking the type signature for g,
-that g isn't polymorphic enough; but then we get another one when
-dealing with the (Num x) context arising from f's definition;
-we try to unify x with Int (to default it), but find that x has already
-been unified with the DontBind variable "a" from g's signature.
-This is really a problem with side-effecting unification; we'd like to
-undo g's effects when its type signature fails, but unification is done
-by side effect, so we can't (easily).
+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
-So we revert to ordinary type variables for signatures, and try to
-give a helpful message in checkSigTyVars.
+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.
-\begin{code}
-checkSigTyVars :: [TcTyVar s] -- The original signature type variables
- -> TcType s -- signature type (for err msg)
- -> TcM s [TcTyVar s] -- Zonked signature type variables
-
-checkSigTyVars sig_tyvars sig_tau
- = mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys ->
- let
- sig_tyvars' = map (getTyVar "checkSigTyVars") sig_tys
- in
+Then we get
- -- Check points (a) and (b)
- checkTcM (all isTyVarTy sig_tys && hasNoDups sig_tyvars')
- (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' ->
- failWithTc (badMatchErr sig_tau sig_tau')
- ) `thenTc_`
-
- -- Check point (c)
- -- We want to report errors in terms of the original signature tyvars,
- -- ie sig_tyvars, NOT sig_tyvars'. sig_tyvars' correspond
- -- 1-1 with sig_tyvars, so we can just map back.
- tcGetGlobalTyVars `thenNF_Tc` \ globals ->
- let
- mono_tyvars' = [sig_tv' | sig_tv' <- sig_tyvars',
- sig_tv' `elementOfTyVarSet` globals]
-
- mono_tyvars = map (assoc "checkSigTyVars" (sig_tyvars' `zip` sig_tyvars)) mono_tyvars'
- in
- checkTcM (null mono_tyvars')
- (failWithTc (notAsPolyAsSigErr sig_tau mono_tyvars)) `thenTc_`
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
- returnTc sig_tyvars'
-\end{code}
%************************************************************************
%* *
-\subsection{SPECIALIZE pragmas}
+ Signatures
%* *
%************************************************************************
+Type signatures are tricky. See Note [Signature skolems] in TcType
-@tcPragmaSigs@ munches up the "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.
+@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}
-tcPragmaSigs :: [RenamedSig] -- The pragma signatures
- -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
- TcMonoBinds s,
- LIE s)
+type TcSigFun = Name -> Maybe (LSig Name)
--- For now we just deal with INLINE pragmas
-tcPragmaSigs sigs = returnTc (prag_fn, EmptyMonoBinds, emptyLIE )
+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
- prag_fn name | any has_inline sigs = IWantToBeINLINEd
- | otherwise = NoPragmaInfo
- where
- has_inline (InlineSig n _) = (n == name)
- has_inline other = False
-
-
-{-
-tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
- let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
- in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
-
-\begin{code}
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addUnfoldInfo (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addUnfoldInfo (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
+ 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}
-The interesting case is for SPECIALISE pragmas. There are two forms.
-Here's the first form:
-\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.
-
-The second form is this:
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b = g #-}
-\end{verbatim}
-
-Here @g@ is specified as a function that implements the specialised
-version of @f@. Suppose that g has type (a->b->b); that is, g's type
-is more general than that required. For this we generate
-\begin{verbatim}
- f@Int = /\b -> g Int b
- f* = f@Int
-\end{verbatim}
-
-Here @f@@Int@ is a SpecId, the specialised version of @f@. It inherits
-f's export status etc. @f*@ is a SpecPragmaId, as before, which just serves
-to prevent @f@@Int@ from being discarded prematurely. After specialisation,
-if @f@@Int@ is going to be used at all it will be used explicitly, so the simplifier can
-discard the f* binding.
-
-Actually, there is really only point in giving a SPECIALISE pragma on exported things,
-and the simplifer won't discard SpecIds for exporte things anyway, so maybe this is
-a bit of overkill.
-
\begin{code}
-tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
-
- -- Get and instantiate its alleged specialised type
- tcHsType poly_ty `thenTc` \ sig_sigma ->
- tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
- let
- (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
- origin = ValSpecOrigin name
- in
-
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (null sig_theta)
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
-
- -- Get and instantiate the type of the id mentioned
- tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
- tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty ->
- let
- (main_tyvars, main_rho) = splitForAllTys main_ty
- (main_theta,main_tau) = splitRhoTy main_rho
- main_arg_tys = mkTyVarTys main_tyvars
- in
-
- -- Check that the specialised type is indeed an instance of
- -- the type of the main function.
- unifyTauTy sig_tau main_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Check that the type variables of the polymorphic function are
- -- either left polymorphic, or instantiate to ground type.
- -- Also check that the overloaded type variables are instantiated to
- -- ground type; or equivalently that all dictionaries have ground type
- zonkTcTypes main_arg_tys `thenNF_Tc` \ main_arg_tys' ->
- zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' ->
- tcAddErrCtxt (specGroundnessCtxt main_arg_tys')
- (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_`
- tcAddErrCtxt (specContextGroundnessCtxt main_theta')
- (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_`
-
- -- Build the SpecPragmaId; it is the thing that makes sure we
- -- don't prematurely dead-code-eliminate the binding we are really interested in.
- newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_pragma_id ->
-
- -- Build a suitable binding; depending on whether we were given
- -- a value (Maybe Name) to be used as the specialisation.
- case using of
- Nothing -> -- No implementation function specified
-
- -- Make a Method inst for the occurrence of the overloaded function
- newMethodWithGivenTy (OccurrenceOf name)
- (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) ->
-
- let
- pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs
- pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id))
- in
- returnTc (pseudo_bind, lie, \ info -> info)
-
- Just spec_name -> -- Use spec_name as the specialisation value ...
-
- -- Type check a simple occurrence of the specialised Id
- tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
-
- -- Check that it has the correct type, and doesn't constrain the
- -- signature variables at all
- unifyTauTy sig_tau spec_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
-
- let
- spec_rhs = mkHsTyLam sig_tyvars spec_body
- spec_binds = VarMonoBind local_spec_id spec_rhs
- `AndMonoBinds`
- VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
- spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
- in
- returnTc ((name, addSpecInfo spec_info), spec_binds, spec_lie)
--}
+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 <+> ptext SLIT(" ::") <+> 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)
-----------------------------------------------
-notAsPolyAsSigErr sig_tau mono_tyvars
- = hang (ptext SLIT("A type signature is more polymorphic than the inferred type"))
- 4 (vcat [text "Can't for-all the type variable(s)" <+>
- pprQuotedList mono_tyvars,
- text "in the type" <+> quotes (ppr sig_tau)
- ])
+sigContextsCtxt sig1 sig2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
+ 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
------------------------------------------------
-badMatchErr sig_ty inferred_ty
- = hang (ptext SLIT("Type signature doesn't match inferred type"))
- 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sig_ty),
- hang (ptext SLIT("Inferred :")) 4 (ppr inferred_ty)
- ])
-----------------------------------------------
-sigCtxt id
- = sep [ptext SLIT("When checking the type signature for"), quotes (ppr id)]
-
-bindSigsCtxt ids
- = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
+unboxedTupleErr name ty
+ = hang (ptext SLIT("Illegal binding of unboxed tuple"))
+ 4 (ppr name <+> dcolon <+> ppr ty)
-----------------------------------------------
-sigContextsErr
- = ptext SLIT("Mismatched contexts")
-sigContextsCtxt s1 s2
- = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"),
- quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)])
- 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)"))
+restrictedBindCtxtErr binder_names
+ = hang (ptext SLIT("Illegal overloaded type signature(s)"))
+ 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
+ ptext SLIT("that falls under the monomorphism restriction")])
------------------------------------------------
-specGroundnessCtxt
- = panic "specGroundnessCtxt"
-
---------------------------------------------
-specContextGroundnessCtxt -- err_ctxt dicts
- = panic "specContextGroundnessCtxt"
-{-
- = hang (
- sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr name],
- hcat [ptext SLIT(" specialised to the type"), ppr spec_ty],
- pp_spec_id,
- ptext SLIT("... not all overloaded type variables were instantiated"),
- ptext SLIT("to ground types:")])
- 4 (vcat [hsep [ppr c, ppr t]
- | (c,t) <- map getDictClassAndType dicts])
- where
- (name, spec_ty, locn, pp_spec_id)
- = case err_ctxt of
- ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> empty)
- ValSpecSpecIdCtxt n ty spec loc ->
- (n, ty, loc,
- hsep [ptext SLIT("... type of explicit id"), ppr spec])
--}
+genCtxt binder_names
+ = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
\end{code}
projects / ghc-hetmet.git / blobdiff