\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where
+module TcBinds ( tcLocalBinds, tcTopBinds,
+ tcHsBootSigs, tcMonoBinds,
+ TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
+ TcSigInfo(..),
+ badBootDeclErr ) where
#include "HsVersions.h"
import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
-import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho )
-
-import CmdLineOpts ( DynFlag(Opt_MonomorphismRestriction) )
-import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, Sig(..),
- LSig, Match(..), HsBindGroup(..), IPBind(..),
- LPat, GRHSs, MatchGroup(..), emptyLHsBinds, isEmptyLHsBinds,
- collectHsBindBinders, collectPatBinders, pprPatBind
+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 ( TcId, TcDictBinds, zonkId, mkHsLet )
+import TcHsSyn ( zonkId )
import TcRnMonad
-import Inst ( InstOrigin(..), newDictsAtLoc, newIPDict, instToId )
-import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, newLocalName, tcLookupLocalIds )
-import TcUnify ( Expected(..), tcInfer, checkSigTyVars, sigCtxt )
-import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
- tcSimplifyToDicts, tcSimplifyIPs )
-import TcHsType ( tcHsSigType, UserTypeCtxt(..), tcAddLetBoundTyVars,
- TcSigInfo(..), TcSigFun, mkTcSig, lookupSig
- )
+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 ( newTyFlexiVarTy, tcSkolType, zonkQuantifiedTyVar, zonkTcTypes )
-import TcType ( TcTyVar, SkolemInfo(SigSkol),
- TcTauType, TcSigmaType,
- TvSubstEnv, mkTvSubst, substTheta, substTy,
- mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
- mkForAllTy, isUnLiftedType, tcGetTyVar_maybe,
- mkTyVarTys )
-import Unify ( tcMatchPreds )
-import Kind ( argTypeKind, isUnliftedTypeKind )
-import VarEnv ( lookupVarEnv )
+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 ( mkLocalId, mkSpecPragmaId, setInlinePragma )
-import Var ( idType, idName )
+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, noLoc, getLoc )
+import SrcLoc ( Located(..), unLoc, getLoc )
import Bag
-import Util ( isIn )
-import Maybes ( orElse )
-import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec,
- 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 :: [HsBindGroup Name] -> TcM (LHsBinds TcId, TcLclEnv)
+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 $
- getLclEnv `thenM` \ env ->
- returnM (emptyLHsBinds, env)
- where
+ = 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 MonoBinds
- glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env)
- -- Can't have a HsIPBinds at top level
+ -- 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
+ 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")
-tcBindsAndThen
- :: (HsBindGroup TcId -> thing -> thing) -- Combinator
- -> [HsBindGroup Name]
- -> TcM thing
- -> TcM thing
+------------------------
+tcLocalBinds :: HsLocalBinds Name -> TcM thing
+ -> TcM (HsLocalBinds TcId, thing)
-tcBindsAndThen = tc_binds_and_then NotTopLevel
+tcLocalBinds EmptyLocalBinds thing_inside
+ = do { thing <- thing_inside
+ ; return (EmptyLocalBinds, thing) }
-tc_binds_and_then top_lvl combiner [] do_next
- = do_next
-tc_binds_and_then top_lvl combiner (group : groups) do_next
- = tc_bind_and_then top_lvl combiner group $
- tc_binds_and_then top_lvl combiner groups do_next
+tcLocalBinds (HsValBinds binds) thing_inside
+ = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
+ ; return (HsValBinds binds', thing) }
-tc_bind_and_then top_lvl combiner (HsIPBinds binds) do_next
- = getLIE do_next `thenM` \ (result, expr_lie) ->
- mapAndUnzipM (wrapLocSndM tc_ip_bind) binds `thenM` \ (avail_ips, binds') ->
+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
- tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds ->
-
- returnM (combiner (HsIPBinds binds') $
- combiner (HsBindGroup dict_binds [] Recursive) result)
+ ; 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)
- = newTyFlexiVarTy argTypeKind `thenM` \ ty ->
+ = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
- tcCheckRho expr ty `thenM` \ expr' ->
+ tcMonoExpr expr ty `thenM` \ expr' ->
returnM (ip_inst, (IPBind ip' expr'))
-tc_bind_and_then top_lvl combiner (HsBindGroup binds sigs is_rec) do_next
- | isEmptyLHsBinds binds
- = do_next
- | otherwise
- = -- 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)
- tcAddLetBoundTyVars binds $
-
- case top_lvl of
- TopLevel -- 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
- -> tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
- tc_body poly_ids `thenM` \ (prag_binds, thing) ->
- returnM (combiner (HsBindGroup
- (poly_binds `unionBags` prag_binds)
- [] -- no sigs
- Recursive)
- thing)
-
- NotTopLevel -- For nested bindings we must do the bindInstsOfLocalFuns thing.
- | not (isRec is_rec) -- Non-recursive group
- -> -- We want to keep non-recursive things non-recursive
- -- so that we desugar unlifted bindings correctly
- tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
- getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) ->
-
- -- Create specialisations of functions bound here
- bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
-
- returnM (
- combiner (HsBindGroup poly_binds [] NonRecursive) $
- combiner (HsBindGroup prag_binds [] NonRecursive) $
- combiner (HsBindGroup lie_binds [] Recursive) $
- -- NB: the binds returned by tcSimplify and
- -- bindInstsOfLocalFuns aren't guaranteed in
- -- dependency order (though we could change that);
- -- hence the Recursive marker.
- thing)
-
- | otherwise
- -> -- 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 tcBindWithSigs.
-
- getLIE (
- tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
- tc_body poly_ids `thenM` \ (prag_binds, thing) ->
- returnM (poly_ids, poly_binds `unionBags` prag_binds, thing)
- ) `thenM` \ ((poly_ids, extra_binds, thing), lie) ->
-
- bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
-
- returnM (combiner (HsBindGroup
- (extra_binds `unionBags` lie_binds)
- [] Recursive) thing
- )
+------------------------
+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
- tc_body poly_ids -- Type check the pragmas and "thing inside"
- = -- Extend the environment to bind the new polymorphic Ids
- tcExtendIdEnv poly_ids $
-
- -- Build bindings and IdInfos corresponding to user pragmas
- tcSpecSigs sigs `thenM` \ prag_binds ->
+ new_sccs :: [SCC (LHsBind Name)]
+ new_sccs = stronglyConnComp (mkEdges sig_fn binds)
- -- Now do whatever happens next, in the augmented envt
- do_next `thenM` \ thing ->
+-- 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) }
- returnM (prag_binds, thing)
-\end{code}
+ 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
-%************************************************************************
-%* *
-\subsection{tcBindWithSigs}
-%* *
-%************************************************************************
+------------------------
+mkEdges :: TcSigFun -> LHsBinds Name
+ -> [(LHsBind Name, BKey, [BKey])]
-@tcBindWithSigs@ deals with a single binding group. It does generalisation,
-so all the clever stuff is in here.
+type BKey = Int -- Just number off the bindings
-* binder_names and mbind must define the same set of Names
+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)
-* The Names in tc_ty_sigs must be a subset of binder_names
+ keyd_binds = bagToList binds `zip` [0::BKey ..]
-* The Ids in tc_ty_sigs don't necessarily have to have the same name
- as the Name in the tc_ty_sig
+ key_map :: NameEnv BKey -- Which binding it comes from
+ key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
+ , bndr <- bindersOfHsBind bind ]
-\begin{code}
-tcBindWithSigs :: TopLevelFlag
- -> LHsBinds Name
- -> [LSig Name]
- -> RecFlag
- -> TcM (LHsBinds TcId, [TcId])
- -- The returned TcIds are guaranteed zonked
-
-tcBindWithSigs top_lvl mbind sigs is_rec = do
- { -- TYPECHECK THE SIGNATURES
- tc_ty_sigs <- recoverM (returnM []) $
- tcTySigs [sig | sig@(L _(Sig name _)) <- sigs]
- ; let lookup_sig = lookupSig tc_ty_sigs
+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
- ; recoverM (recoveryCode mbind lookup_sig) $ do
+ setSrcSpan loc $
+ recoverM (recoveryCode binder_names) $ do
- { traceTc (ptext SLIT("--------------------------------------------------------"))
- ; traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind))
+ { traceTc (ptext SLIT("------------------------------------------------"))
+ ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
-- TYPECHECK THE BINDINGS
- ; ((mbind', mono_bind_infos), lie_req)
- <- getLIE (tcMonoBinds mbind lookup_sig is_rec)
+ ; ((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)
- ; if any isUnLiftedType zonked_mono_tys then
- do { -- Unlifted bindings
- checkUnliftedBinds top_lvl is_rec mbind
- ; extendLIEs lie_req
- ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
- mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id)
- mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id)
-
- ; return ( unitBag $ noLoc $ AbsBinds [] [] exports emptyNameSet mbind',
- [poly_id | (_, poly_id, _) <- exports]) } -- Guaranteed zonked
+ ; 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 mbind tc_ty_sigs
+ { is_unres <- isUnRestrictedGroup bind_list sig_fn
; (tyvars_to_gen, dict_binds, dict_ids)
- <- setSrcSpan (getLoc (head (bagToList mbind))) $
- -- TODO: location a bit awkward, but the mbinds have been
- -- dependency analysed and may no longer be adjacent
- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
- generalise is_unres mono_bind_infos tc_ty_sigs lie_req
+ <- 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
; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
-- BUILD THE POLYMORPHIC RESULT IDs
- ; let
- exports = map mk_export mono_bind_infos
- poly_ids = [poly_id | (_, poly_id, _) <- exports]
- dict_tys = map idType dict_ids
-
- inlines = mkNameSet [ name
- | L _ (InlineSig True (L _ name) _) <- sigs]
- -- Any INLINE sig (regardless of phase control)
- -- makes the RHS look small
- inline_phases = listToFM [ (name, phase)
- | L _ (InlineSig _ (L _ name) phase) <- sigs,
- not (isAlwaysActive phase)]
- -- Set the IdInfo field to control the inline phase
- -- AlwaysActive is the default, so don't bother with them
- add_inlines id = attachInlinePhase inline_phases id
-
- mk_export (binder_name, mb_sig, mono_id)
- = case mb_sig of
- Just sig -> (sig_tvs sig, add_inlines (sig_id sig), mono_id)
- Nothing -> (tyvars_to_gen', add_inlines new_poly_id, mono_id)
- where
- new_poly_id = mkLocalId binder_name poly_ty
- poly_ty = mkForAllTys tyvars_to_gen'
- $ mkFunTys dict_tys
- $ idType mono_id
+ ; 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 ((dict_ids, dict_binds),
- exports, map idType zonked_poly_ids))
-
- ; return (
- unitBag $ noLoc $
- AbsBinds tyvars_to_gen'
- dict_ids
- exports
- inlines
- (dict_binds `unionBags` mbind'),
- zonked_poly_ids
- )
- } } }
-
--- If typechecking the binds fails, then return with each
--- signature-less binder given type (forall a.a), to minimise
--- subsequent error messages
-recoveryCode mbind lookup_sig
- = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
- ; return (emptyLHsBinds, poly_ids) }
- where
- forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
- binder_names = collectHsBindBinders mbind
- poly_ids = map mk_dummy binder_names
- mk_dummy name = case lookup_sig name of
- Just sig -> sig_id sig -- Signature
- Nothing -> mkLocalId name forall_a_a -- No signature
-
-attachInlinePhase inline_phases bndr
- = case lookupFM inline_phases (idName bndr) of
- Just prag -> bndr `setInlinePragma` prag
- Nothing -> bndr
-
--- 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))
-
-checkUnliftedBinds top_lvl is_rec mbind
- = checkTc (isNotTopLevel top_lvl)
- (unliftedBindErr "Top-level" mbind) `thenM_`
- checkTc (isNonRec is_rec)
- (unliftedBindErr "Recursive" mbind) `thenM_`
- checkTc (isSingletonBag mbind)
- (unliftedBindErr "Multiple" mbind)
-\end{code}
+ ; 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')
-Polymorphic recursion
-~~~~~~~~~~~~~~~~~~~~~
-The game plan for polymorphic recursion in the code above is
+ ; return ([unitBag abs_bind], zonked_poly_ids)
+ } }
- * 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.
-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:
+--------------
+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
- f :: Eq a => [a] -> [a]
- f xs = ...f...
+ 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
-If we don't take care, after typechecking we get
- f = /\a -> \d::Eq a -> let f' = f a d
- in
- \ys:[a] -> ...f'...
+------------------------
+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
-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
+pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
- f = /\a -> \d::Eq a -> letrec
- fm = \ys:[a] -> ...fm...
- in
- fm
+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)
-This can lead to a massive space leak, from the following top-level defn
-(post-typechecking)
- ff :: [Int] -> [Int]
- ff = f Int dEqInt
+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
-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.
+forall_a_a :: TcType
+forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
- ff = f Int dEqInt
- = let f' = f Int dEqInt in \ys. ...f'...
+-- 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))
- = let f' = let f' = f Int dEqInt in \ys. ...f'...
- in \ys. ...f'...
+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")
-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.
+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}
%************************************************************************
%* *
%************************************************************************
-@tcMonoBinds@ deals with a single @MonoBind@.
+@tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
The signatures have been dealt with already.
\begin{code}
-tcMonoBinds :: LHsBinds Name
- -> TcSigFun -> RecFlag
+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])
-type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
- -- Type signature (if any), and
- -- the monomorphic bound things
-
-bndrNames :: [MonoBindInfo] -> [Name]
-bndrNames mbi = [n | (n,_,_) <- mbi]
+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)
-getMonoType :: MonoBindInfo -> TcTauType
-getMonoType (_,_,mono_id) = idType mono_id
-
-tcMonoBinds binds lookup_sig is_rec
- = do { tc_binds <- mapBagM (wrapLocM (tcLhs lookup_sig)) binds
- ; let mono_info = getMonoBindInfo tc_binds
- ; binds' <- tcExtendIdEnv2 (rhsEnvExtension mono_info) $
- mapBagM (wrapLocM tcRhs) tc_binds
- ; return (binds', mono_info) }
+ ; 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
= TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
| TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
+type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
+ -- Type signature (if any), and
+ -- the monomorphic bound things
+
+bndrNames :: [MonoBindInfo] -> [Name]
+bndrNames mbi = [n | (n,_,_) <- mbi]
+
+getMonoType :: MonoBindInfo -> TcTauType
+getMonoType (_,_,mono_id) = idType mono_id
+
tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
-tcLhs lookup_sig (FunBind (L nm_loc name) inf matches)
- = do { let mb_sig = lookup_sig name
+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 = newTyFlexiVarTy argTypeKind
+ mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
+
+tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
+ = do { mb_sigs <- mapM (tcInstSig_maybe . sig_fn) names
+
+ ; 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
-tcLhs lookup_sig bind@(PatBind pat grhss _)
- = do { let tc_pat exp_ty = tcPat (LetPat lookup_sig) pat exp_ty lookup_infos
- ; ((pat', ex_tvs, infos), pat_ty)
- <- addErrCtxt (patMonoBindsCtxt pat grhss)
- (tcInfer tc_pat)
+ 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.
- -- Don't know how to deal with pattern-bound existentials yet
- ; checkTc (null ex_tvs) (existentialExplode bind)
+ -- 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) }
+
+ ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
+ tcInfer tc_pat
; return (TcPatBind infos pat' grhss pat_ty) }
where
names = collectPatBinders pat
- -- After typechecking the pattern, look up the binder
- -- names, which the pattern has brought into scope.
- lookup_infos :: TcM [MonoBindInfo]
- lookup_infos = do { mono_ids <- tcLookupLocalIds names
- ; return [ (name, lookup_sig name, mono_id)
- | (name, mono_id) <- names `zip` mono_ids] }
+
+tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
+ -- AbsBind, VarBind impossible
-------------------
tcRhs :: TcMonoBind -> TcM (HsBind TcId)
-tcRhs (TcFunBind _ fun'@(L _ mono_id) inf matches)
- = do { matches' <- tcMatchesFun (idName mono_id) matches
- (Check (idType mono_id))
- ; return (FunBind fun' inf matches') }
+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 }) }
tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
= do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
- tcGRHSsPat grhss (Check pat_ty)
- ; return (PatBind pat' grhss' pat_ty) }
+ tcGRHSsPat grhss pat_ty
+ ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
+ bind_fvs = placeHolderNames }) }
---------------------
-getMonoBindInfo :: Bag (Located TcMonoBind) -> [MonoBindInfo]
+getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
getMonoBindInfo tc_binds
- = foldrBag (get_info . unLoc) [] tc_binds
+ = foldr (get_info . unLoc) [] tc_binds
where
get_info (TcFunBind info _ _ _) rest = info : rest
get_info (TcPatBind infos _ _ _) rest = infos ++ rest
-
----------------------
-rhsEnvExtension :: [MonoBindInfo] -> [(Name, TcId)]
--- Environment for RHS of definitions: use type sig if there is one
-rhsEnvExtension mono_info
- = map mk mono_info
- where
- mk (name, Just sig, _) = (name, sig_id sig)
- mk (name, Nothing, mono_id) = (name, mono_id)
\end{code}
%************************************************************************
%* *
-\subsection{getTyVarsToGen}
+ Generalisation
%* *
%************************************************************************
\begin{code}
-tcTySigs :: [LSig Name] -> TcM [TcSigInfo]
--- The trick here is that all the signatures should have the same
--- context, and we want to share type variables for that context, so that
--- all the right hand sides agree a common vocabulary for their type
--- constraints
-tcTySigs [] = return []
-tcTySigs (L span (Sig (L _ name) ty) : sigs)
- = do { -- Typecheck the first signature
- ; sigma1 <- setSrcSpan span $
- tcHsSigType (FunSigCtxt name) ty
- ; let id1 = mkLocalId name sigma1
- ; tc_sig1 <- mkTcSig id1
-
- ; tc_sigs <- mapM (tcTySig tc_sig1) sigs
- ; return (tc_sig1 : tc_sigs) }
-
-tcTySig sig1 (L span (Sig (L _ name) ty))
- = setSrcSpan span $
- do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
- ; (tvs, theta, tau) <- tcSkolType rigid_info sigma_ty
- ; let poly_id = mkLocalId name sigma_ty
- bale_out = failWithTc $
- sigContextsErr (sig_id sig1) name sigma_ty
-
- -- Try to match the context of this signature with
- -- that of the first signature
- ; case tcMatchPreds tvs theta (sig_theta sig1) of {
- Nothing -> bale_out
- ; Just tenv -> do
- ; case check_tvs tenv tvs of
- Nothing -> bale_out
- Just tvs' -> do {
-
- let subst = mkTvSubst tenv
- theta' = substTheta subst theta
- tau' = substTy subst tau
- ; loc <- getInstLoc (SigOrigin rigid_info)
- ; return (TcSigInfo { sig_id = poly_id, sig_tvs = tvs',
- sig_theta = theta', sig_tau = tau',
- sig_loc = loc }) }}}
- where
- rigid_info = SigSkol name
-
- -- Rather tedious check that the type variables
- -- have been matched only with another type variable,
- -- and that two type variables have not been matched
- -- with the same one
- -- A return of Nothing indicates that one of the bad
- -- things has happened
- check_tvs :: TvSubstEnv -> [TcTyVar] -> Maybe [TcTyVar]
- check_tvs tenv [] = Just []
- check_tvs tenv (tv:tvs)
- = do { let ty = lookupVarEnv tenv tv `orElse` mkTyVarTy tv
- ; tv' <- tcGetTyVar_maybe ty
- ; tvs' <- check_tvs tenv tvs
- ; if tv' `elem` tvs'
- then Nothing
- else Just (tv':tvs') }
-\end{code}
-
-\begin{code}
-generalise :: Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst]
+generalise :: TopLevelFlag -> Bool
+ -> [MonoBindInfo] -> [Inst]
-> TcM ([TcTyVar], TcDictBinds, [TcId])
-generalise is_unrestricted mono_infos sigs lie_req
+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 bndr_names)
+ (restrictedBindCtxtErr bndrs)
-- Now simplify with exactly that set of tyvars
-- We have to squash those Methods
- ; (qtvs, binds) <- tcSimplifyRestricted doc tau_tvs lie_req
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
+ tau_tvs lie_req
-- Check that signature type variables are OK
; final_qtvs <- checkSigsTyVars qtvs sigs
= tcSimplifyInfer doc tau_tvs lie_req
| otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
- = do { let sig1 = head sigs
- ; sig_lie <- newDictsAtLoc (sig_loc sig1) (sig_theta sig1)
+ = 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 comments at end of fn)
+ -- 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
; final_qtvs <- checkSigsTyVars forall_tvs sigs
; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
-
where
- bndr_names = bndrNames mono_infos
- tau_tvs = foldr (unionVarSet . tyVarsOfType . getMonoType) emptyVarSet mono_infos
+ 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 bndr_names
+ 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}
+
+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).
-mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
- sig_theta = theta, sig_tau = tau, sig_loc = loc }) mono_id
- = Method mono_id poly_id (mkTyVarTys tvs) theta tau loc
+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
+
+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
- = mappM check_one sigs `thenM` \ sig_tvs_s ->
- let
- -- Sigh. Make sure that all the tyvars in the type sigs
- -- appear in the returned ty var list, which is what we are
- -- going to generalise over. Reason: we occasionally get
- -- silly types like
- -- type T a = () -> ()
- -- f :: T a
- -- f () = ()
- -- Here, 'a' won't appear in qtvs, so we have to add it
-
- sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
- all_tvs = extendVarSetList sig_tvs qtvs
- in
- returnM (varSetElems all_tvs)
+ = do { gbl_tvs <- tcGetGlobalTyVars
+ ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
+
+ ; let -- Sigh. Make sure that all the tyvars in the type sigs
+ -- appear in the returned ty var list, which is what we are
+ -- going to generalise over. Reason: we occasionally get
+ -- silly types like
+ -- type T a = () -> ()
+ -- f :: T a
+ -- f () = ()
+ -- Here, 'a' won't appear in qtvs, so we have to add it
+ sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
+ all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
+ ; returnM all_tvs }
where
- check_one (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 { checkSigTyVars tvs; return tvs }
-\end{code}
+ check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
+ sig_theta = theta, sig_tau = tau})
+ = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
+ addErrCtxtM (sigCtxt id tvs theta tau) $
+ do { tvs' <- checkDistinctTyVars tvs
+ ; ifM (any (`elemVarSet` gbl_tvs) tvs')
+ (bleatEscapedTvs gbl_tvs tvs tvs')
+ ; return tvs' }
+
+checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
+-- (checkDistinctTyVars tvs) checks that the tvs from one type signature
+-- are still all type variables, and all distinct from each other.
+-- It returns a zonked set of type variables.
+-- For example, if the type sig is
+-- f :: forall a b. a -> b -> b
+-- we want to check that 'a' and 'b' haven't
+-- (a) been unified with a non-tyvar type
+-- (b) been unified with each other (all distinct)
+
+checkDistinctTyVars sig_tvs
+ = do { zonked_tvs <- mapM 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 :: LHsBinds Name -> [TcSigInfo] -> TcM Bool
-isUnRestrictedGroup binds sigs
- = do { mono_restriction <- doptM Opt_MonomorphismRestriction
- ; return (not mono_restriction || all_unrestricted) }
- where
- all_unrestricted = all (unrestricted . unLoc) (bagToList binds)
- tysig_names = map (idName . sig_id) sigs
+Note [Polymorphic recursion]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
- unrestricted (PatBind other _ _) = False
- unrestricted (VarBind v _) = v `is_elem` tysig_names
- unrestricted (FunBind v _ matches) = unrestricted_match matches
- || unLoc v `is_elem` tysig_names
+ * 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.
- unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
- -- No args => like a pattern binding
- unrestricted_match other = True
- -- Some args => a function binding
+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...
+
+If we don't take care, after typechecking we get
+
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
+
+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
-is_elem v vs = isIn "isUnResMono" v vs
-\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:
- {-# RULES (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 :: [LSig Name] -> TcM (LHsBinds TcId)
-tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs)
- = -- SPECIALISE f :: forall b. theta => tau = g
- setSrcSpan loc $
- addErrCtxt (valSpecSigCtxt name poly_ty) $
-
- -- Get and instantiate its alleged specialised type
- tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty ->
-
- -- Check that f has a more general type, and build a RHS for
- -- the spec-pragma-id at the same time
- getLIE (tcCheckSigma (L nm_loc (HsVar name)) sig_ty) `thenM` \ (spec_expr, spec_lie) ->
-
- -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
- tcSimplifyToDicts spec_lie `thenM` \ 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 `thenM` \ spec_name ->
- let
- spec_bind = VarBind (mkSpecPragmaId spec_name sig_ty)
- (mkHsLet spec_binds spec_expr)
- in
+type TcSigFun = Name -> Maybe (LSig Name)
+
+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}
+
+\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)
- -- Do the rest and combine
- tcSpecSigs sigs `thenM` \ binds_rest ->
- returnM (binds_rest `snocBag` L loc spec_bind)
+ 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)
-tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
-tcSpecSigs [] = returnM emptyLHsBinds
+ unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
+ -- No args => like a pattern binding
+ unrestricted_match other = True
+ -- Some args => a function binding
\end{code}
+
%************************************************************************
%* *
\subsection[TcBinds-errors]{Error contexts and messages}
= hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
-----------------------------------------------
-valSpecSigCtxt v ty
- = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
- nest 4 (ppr v <+> dcolon <+> ppr ty)]
-
------------------------------------------------
-sigContextsErr id1 name ty
- = vcat [ptext SLIT("Mis-match between the contexts of the signatures for"),
+sigContextsCtxt sig1 sig2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
- ppr name <+> dcolon <+> ppr ty]),
+ 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
--- Use quotes for a single one; they look a bit "busy" for several
-pprBinders [bndr] = quotes (ppr bndr)
-pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
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