%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
module TcBinds ( tcLocalBinds, tcTopBinds,
tcHsBootSigs, tcMonoBinds,
TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
import {-# SOURCE #-} TcExpr ( tcMonoExpr )
-import DynFlags ( dopt, DynFlags,
- DynFlag(Opt_MonomorphismRestriction, Opt_MonoPatBinds, 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 ( zonkId )
+import DynFlags
+import HsSyn
+import TcHsSyn
import TcRnMonad
-import Inst ( newDictsAtLoc, newIPDict, instToId )
-import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
- pprBinders, tcLookupLocalId_maybe, tcLookupId,
- tcGetGlobalTyVars )
-import TcUnify ( tcInfer, tcSubExp, unifyTheta,
- bleatEscapedTvs, sigCtxt )
-import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck,
- tcSimplifyRestricted, tcSimplifyIPs )
-import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
-import TcPat ( tcPat, PatCtxt(..) )
-import TcSimplify ( bindInstsOfLocalFuns )
-import TcMType ( 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 Inst
+import TcEnv
+import TcUnify
+import TcSimplify
+import TcHsType
+import TcPat
+import TcMType
+import TcType
+import {- Kind parts of -} Type
+import Coercion
+import VarEnv
+import TysPrim
+import Id
+import IdInfo
+import Var ( TyVar, varType )
+import Name
import NameSet
import NameEnv
import VarSet
-import SrcLoc ( Located(..), unLoc, getLoc )
+import SrcLoc
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 ErrUtils
+import Digraph
+import Maybes
+import List
+import Util
+import BasicTypes
import Outputable
+
+import Control.Monad
\end{code}
-- 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'))
+ tc_ip_bind (IPBind ip expr) = do
+ ty <- newFlexiTyVarTy argTypeKind
+ (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty
+ expr' <- tcMonoExpr expr ty
+ return (ip_inst, (IPBind ip' expr'))
------------------------
tcValBinds :: TopLevelFlag
-- Extend the envt right away with all
-- the Ids declared with type signatures
+ ; poly_rec <- doptM Opt_RelaxedPolyRec
; (binds', thing) <- tcExtendIdEnv poly_ids $
- tc_val_binds top_lvl sig_fn prag_fn
+ tc_val_binds poly_rec top_lvl sig_fn prag_fn
binds thing_inside
; return (ValBindsOut binds' sigs, thing) }
------------------------
-tc_val_binds :: TopLevelFlag -> TcSigFun -> TcPragFun
+tc_val_binds :: Bool -> 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
+tc_val_binds poly_rec 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
+tc_val_binds poly_rec 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
+ <- tc_group poly_rec top_lvl sig_fn prag_fn group $
+ tc_val_binds poly_rec top_lvl sig_fn prag_fn groups thing_inside
; return (group' ++ groups', thing) }
------------------------
-tc_group :: TopLevelFlag -> TcSigFun -> TcPragFun
+tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
-> (RecFlag, LHsBinds Name) -> TcM thing
-> TcM ([(RecFlag, LHsBinds TcId)], thing)
-- 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
+tc_group poly_rec 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
+ = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive 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
+tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
+ | not poly_rec -- Recursive group, normal Haskell 98 route
+ = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
+ ; return ([(Recursive, unionManyBags binds1)], thing) }
+
+ | otherwise -- Recursive group, with gla-exts
+ = -- 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
+ -- Notice that the bindInsts thing covers *all* the bindings in the original
+ -- group at once; an earlier one may use a later one!
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) }
+ ; (binds1,thing) <- bindLocalInsts top_lvl $
+ go (stronglyConnComp (mkEdges sig_fn binds))
+ ; return ([(Recursive, unionManyBags binds1)], 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], [TcId], thing)
+ go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
+ ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
+ ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
+ go [] = do { thing <- thing_inside; return ([], [], 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) }
+ tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
+ tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
- go1 (AcyclicSCC bind) = tc_binds NonRecursive (unitBag bind)
- go1 (CyclicSCC binds) = tc_binds Recursive (listToBag binds)
+ tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
- tc_binds rec_tc binds = tcPolyBinds top_lvl Recursive rec_tc sig_fn prag_fn binds
+tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
+ = bindLocalInsts top_lvl $ do
+ { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
+ ; thing <- tcExtendIdEnv ids thing_inside
+ ; return (binds1, ids, thing) }
+
+------------------------
+bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
+bindLocalInsts top_lvl thing_inside
+ | isTopLevel top_lvl = do { (binds, ids, thing) <- thing_inside; return (binds, thing) }
+ -- For the top level don't bother with 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
+
+ | otherwise -- Nested case
+ = do { ((binds, ids, thing), lie) <- getLIE thing_inside
+ ; lie_binds <- bindInstsOfLocalFuns lie ids
+ ; return (binds ++ [lie_binds], thing) }
------------------------
mkEdges :: TcSigFun -> LHsBinds Name
bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
------------------------
-tcPolyBinds :: TopLevelFlag
+tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
-> RecFlag -- Whether the group is really recursive
- -> RecFlag -- Whether it's recursive for typechecking purposes
- -> TcSigFun -> TcPragFun
+ -> RecFlag -- Whether it's recursive after breaking
+ -- dependencies based on type signatures
-> LHsBinds Name
- -> TcM thing
- -> TcM ([LHsBinds TcId], thing)
+ -> TcM ([LHsBinds TcId], [TcId])
-- 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
+tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
= let
- binder_names = collectHsBindBinders binds
bind_list = bagToList binds
-
- loc = getLoc (head bind_list)
+ binder_names = collectHsBindBinders 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
+ recoverM (recoveryCode binder_names sig_fn) $ 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)
+ ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req))
-- CHECK FOR UNLIFTED BINDINGS
-- These must be non-recursive etc, and are not generalised
else do -- The normal lifted case: GENERALISE
{ dflags <- getDOpts
- ; (tyvars_to_gen, dict_binds, dict_ids)
+ ; (tyvars_to_gen, dicts, dict_binds)
<- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
generalise dflags top_lvl bind_list sig_fn 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))
+ ; let dict_vars = map instToVar dicts -- May include equality constraints
+ ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars))
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))
+ ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
- ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
- dict_ids exports
+ ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
+ dict_vars exports
(dict_binds `unionBags` binds')
- ; return ([unitBag abs_bind], zonked_poly_ids)
+ ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
} }
--------------
-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
+mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType]
+ -> MonoBindInfo
+ -> TcM ([TyVar], Id, Id, [LPrag])
+-- mkExport generates exports with
+-- zonked type variables,
+-- zonked poly_ids
+-- The former is just because no further unifications will change
+-- the quantified type variables, so we can fix their final form
+-- right now.
+-- The latter is needed because the poly_ids are used to extend the
+-- type environment; see the invariant on TcEnv.tcExtendIdEnv
+
+-- Pre-condition: the inferred_tvs are already zonked
+
+mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
+ = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs
+ ; let warn = isTopLevel top_lvl && warn_missing_sigs
+ ; (tvs, poly_id) <- mk_poly_id warn mb_sig
+ -- poly_id has a zonked type
+
+ ; prags <- tcPrags poly_id (prag_fn poly_name)
+ -- tcPrags requires a zonked poly_id
+
+ ; return (tvs, poly_id, mono_id, prags) }
+ where
+ poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
+
+ mk_poly_id warn Nothing = do { poly_ty' <- zonkTcType poly_ty
+ ; missingSigWarn warn poly_name poly_ty'
+ ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
+ mk_poly_id warn (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
+ ; return (tvs, sig_id sig) }
+ zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
------------------------
type TcPragFun = Name -> [LSig Name]
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
+tcPrags :: Id -> [LSig Name] -> TcM [LPrag]
+tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags
where
- tc_prag (L loc prag) = setSrcSpan loc $
- addErrCtxt (pragSigCtxt prag) $
- tcPrag poly_id prag
+ tc_prag prag = addErrCtxt (pragSigCtxt prag) $
+ tcPrag poly_id prag
pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
tcPrag :: TcId -> Sig Name -> TcM Prag
+-- Pre-condition: the poly_id is zonked
+-- Reason: required by tcSubExp
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)
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) }
+ = do { let name = idName poly_id
+ ; spec_ty <- tcHsSigType (FunSigCtxt name) hs_ty
+ ; co_fn <- tcSubExp (SpecPragOrigin name) (idType poly_id) spec_ty
+ ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty inl) }
-- Most of the work of specialisation is done by
-- the desugarer, guided by the SpecPrag
-- 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
+recoveryCode binder_names sig_fn
= 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
+ mk_dummy name
+ | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
+ | otherwise = return (mkLocalId name forall_a_a) -- No signature
forall_a_a :: TcType
forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
-- 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)
+ do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
-- Check for an unboxed tuple type
-- f = (# True, False #)
; 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 })),
+ fun_co_fn = co_fn, fun_tick = Nothing })),
[(name, Nothing, mono_id)]) }
tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
-- 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 name scoped_tvs
+ do { tc_sig <- tcInstSig True name
; 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 ]
+ | (name, tv) <- scoped_tvs `zip` sig_tvs tc_sig ]
+ -- See Note [More instantiated than scoped]
+ -- Note that the scoped_tvs and the (sig_tvs sig)
+ -- may have different Names. That's quite ok.
- ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
- tcMatchesFun mono_name matches mono_ty
+ ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
+ tcMatchesFun mono_name inf 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 }
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn,
+ fun_tick = Nothing }
; return (unitBag (L b_loc fun_bind'),
[(name, Just tc_sig, mono_id)]) }
-- 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 $
+ ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
- | (n,id) <- rhs_id_env]) `thenM_`
+ | (n,id) <- rhs_id_env])
mapM (wrapLocM tcRhs) tc_binds
; return (listToBag binds', mono_info) }
| (name, Just sig) <- nm_sig_prs]
sig_tau_fn = lookupNameEnv tau_sig_env
- tc_pat exp_ty = tcPat (LetPat sig_tau_fn) pat exp_ty unitTy $ \ _ ->
+ tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
mapM lookup_info nm_sig_prs
- -- The unitTy is a bit bogus; it's the "result type" for lookup_info.
-- After typechecking the pattern, look up the binder
-- names, which the pattern has brought into scope.
-------------------
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)
+-- When we are doing pattern bindings, or multiple function bindings at a time
+-- we *don't* bring any scoped type variables into scope
+-- Wny not? They are not completely rigid.
+-- That's why we have the special case for a single FunBind in tcMonoBinds
+tcRhs (TcFunBind (_,_,mono_id) fun' inf matches)
+ = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
+ matches (idType mono_id)
; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
- bind_fvs = placeHolderNames, fun_co_fn = co_fn }) }
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn,
+ fun_tick = Nothing }) }
tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
= do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
generalise :: DynFlags -> TopLevelFlag
-> [LHsBind Name] -> TcSigFun
-> [MonoBindInfo] -> [Inst]
- -> TcM ([TcTyVar], TcDictBinds, [TcId])
+ -> TcM ([TyVar], [Inst], TcDictBinds)
+-- The returned [TyVar] are all ready to quantify
+
generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
| isMonoGroup dflags bind_list
- = do { extendLIEs lie_req; return ([], emptyBag, []) }
+ = do { extendLIEs lie_req
+ ; return ([], [], emptyBag) }
| isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
= -- Check signature contexts are empty
-- Check that signature type variables are OK
; final_qtvs <- checkSigsTyVars qtvs sigs
- ; return (final_qtvs, binds, []) }
+ ; 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
+ = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked
; 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
+ loc = sig_loc (head sigs)
-- 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
+ ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req
-- Check that signature type variables are OK
- ; final_qtvs <- checkSigsTyVars forall_tvs sigs
+ ; final_qtvs <- checkSigsTyVars qtvs sigs
- ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
+ ; return (final_qtvs, sig_lie, binds) }
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
+ get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType
+ | otherwise = exactTyVarsOfType
+ tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
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
+ = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs,
+ tci_theta = theta, tci_loc = loc}
\end{code}
unifyCtxts checks that all the signature contexts are the same
\begin{code}
unifyCtxts :: [TcSigInfo] -> TcM [Inst]
+-- Post-condition: the returned Insts are full zonked
unifyCtxts (sig1 : sigs) -- Argument is always non-empty
= do { mapM unify_ctxt sigs
- ; newDictsAtLoc (sig_loc sig1) (sig_theta sig1) }
+ ; theta <- zonkTcThetaType (sig_theta sig1)
+ ; newDictBndrs (sig_loc sig1) theta }
where
theta1 = sig_theta sig1
unify_ctxt :: TcSigInfo -> TcM ()
unify_ctxt sig@(TcSigInfo { sig_theta = theta })
- = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
+ = setSrcSpan (instLocSpan (sig_loc sig)) $
addErrCtxt (sigContextsCtxt sig1 sig) $
- unifyTheta theta1 theta
+ do { cois <- unifyTheta theta1 theta
+ ; -- Check whether all coercions are identity coercions
+ -- That can happen if we have, say
+ -- f :: C [a] => ...
+ -- g :: C (F a) => ...
+ -- where F is a type function and (F a ~ [a])
+ -- Then unification might succeed with a coercion. But it's much
+ -- much simpler to require that such signatures have identical contexts
+ checkTc (all isIdentityCoercion cois)
+ (ptext SLIT("Mutually dependent functions have syntactically distinct contexts"))
+ }
checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
checkSigsTyVars qtvs sigs
= do { gbl_tvs <- tcGetGlobalTyVars
- ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
+ ; sig_tvs_s <- mapM (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
-- 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 }
+ ; return 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')
+ ; when (any (`elemVarSet` gbl_tvs) tvs')
+ (bleatEscapedTvs gbl_tvs tvs tvs')
; return tvs' }
checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
<+> quotes (ppr tidy_tv2)
; failWithTcM (env2, msg) }
where
-\end{code}
+\end{code}
@getTyVarsToGen@ decides what type variables to generalise over.
the variable's type, and after that checked to see whether they've
been instantiated.
+Note [Scoped tyvars]
+~~~~~~~~~~~~~~~~~~~~
+The -XScopedTypeVariables flag brings lexically-scoped type variables
+into scope for any explicitly forall-quantified type variables:
+ f :: forall a. a -> a
+ f x = e
+Then 'a' is in scope inside 'e'.
+
+However, we do *not* support this
+ - For pattern bindings e.g
+ f :: forall a. a->a
+ (f,g) = e
+
+ - For multiple function bindings, unless Opt_RelaxedPolyRec is on
+ f :: forall a. a -> a
+ f = g
+ g :: forall b. b -> b
+ g = ...f...
+ Reason: we use mutable variables for 'a' and 'b', since they may
+ unify to each other, and that means the scoped type variable would
+ not stand for a completely rigid variable.
+
+ Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
+
+
+Note [More instantiated than scoped]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+There may be more instantiated type variables than lexically-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 the TcSigFun.
+
+
\begin{code}
type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
-- type variables brought into scope
-- Precondition: no duplicates
mkTcSigFun sigs = lookupNameEnv env
where
- env = mkNameEnv [(name, scoped_tyvars hs_ty)
- | L span (TypeSig (L _ name) (L _ hs_ty)) <- sigs]
- scoped_tyvars (HsForAllTy Explicit tvs _ _) = hsLTyVarNames tvs
- scoped_tyvars other = []
+ env = mkNameEnv [(name, hsExplicitTvs lhs_ty)
+ | L span (TypeSig (L _ name) lhs_ty) <- sigs]
-- 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.)
+ -- of nested type synonyms. See Note [More instantiated than scoped].)
+ -- See Note [Only scoped tyvars are in the TyVarEnv]
---------------
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_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'.
+
+-- Note [Only scoped tyvars are in the TyVarEnv]
+-- We are careful to keep only the *lexically scoped* type variables in
+-- the type environment. Why? After all, the renamer has ensured
+-- that only legal occurrences occur, so we could put all type variables
+-- into the type env.
--
--- We assume that the scoped ones are at the *front* of sig_tvs,
--- and remember the names from the original HsForAllTy in sig_scoped
+-- But we want to check that two distinct lexically scoped type variables
+-- do not map to the same internal type variable. So we need to know which
+-- the lexically-scoped ones are... and at the moment we do that by putting
+-- only the lexically scoped ones into the environment.
+
-- Note [Instantiate sig]
--- It's vital to instantiate a type signature with fresh variable.
+-- It's vital to instantiate a type signature with fresh variables.
-- For example:
-- type S = forall a. a->a
-- f,g :: S
tcInstSig_maybe sig_fn name
= case sig_fn name of
Nothing -> return Nothing
- Just tvs -> do { tc_sig <- tcInstSig False name tvs
- ; return (Just tc_sig) }
+ Just scoped_tvs -> do { tc_sig <- tcInstSig False name
+ ; return (Just tc_sig) }
+ -- NB: the scoped_tvs may be non-empty, but we can
+ -- just ignore them. See Note [Scoped tyvars].
-tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo
+tcInstSig :: Bool -> Name -> TcM TcSigInfo
-- Instantiate the signature, with either skolems or meta-type variables
--- depending on the use_skols boolean
+-- depending on the use_skols boolean. This variable is set True
+-- when we are typechecking a single function binding; and False for
+-- pattern bindings and a group of several function bindings.
+-- Reason: in the latter cases, the "skolems" can be unified together,
+-- so they aren't properly rigid in the type-refinement sense.
+-- NB: unless we are doing H98, each function with a sig will be done
+-- separately, even if it's mutually recursive, so use_skols will be True
--
--- We always instantiate with freshs uniques,
+-- We always instantiate with fresh uniques,
-- although we keep the same print-name
--
-- type T = forall a. [a] -> [a]
--
-- We must not use the same 'a' from the defn of T at both places!!
-tcInstSig use_skols name scoped_names
+tcInstSig use_skols name
= 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
+ inst_tyvars = tcInstSigTyVars use_skols 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 = final_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
- -- We also only have scoped type variables when we are instantiating
- -- with true skolems
- final_scoped_names | use_skols = scoped_names
- | otherwise = []
+ sig_loc = loc }) }
-------------------
isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
genCtxt binder_names
= ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
+
+missingSigWarn False name ty = return ()
+missingSigWarn True name ty
+ = do { env0 <- tcInitTidyEnv
+ ; let (env1, tidy_ty) = tidyOpenType env0 ty
+ ; addWarnTcM (env1, mk_msg tidy_ty) }
+ where
+ mk_msg ty = vcat [ptext SLIT("Definition but no type signature for") <+> quotes (ppr name),
+ sep [ptext SLIT("Inferred type:") <+> ppr name <+> dcolon <+> ppr ty]]
\end{code}