%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
-#include "HsVersions.h"
-
-module TcBinds ( tcBindsAndThen, tcPragmaSigs ) where
+module TcBinds ( tcLocalBinds, tcTopBinds,
+ tcHsBootSigs, tcMonoBinds,
+ TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
+ TcSigInfo(..),
+ badBootDeclErr ) where
-IMP_Ubiq()
+#include "HsVersions.h"
-import HsSyn ( HsBinds(..), Bind(..), Sig(..), MonoBinds(..),
- HsExpr, Match, PolyType, InPat, OutPat(..),
- GRHSsAndBinds, ArithSeqInfo, HsLit, Fake,
- collectBinders )
-import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedBind), RenamedSig(..),
- SYN_IE(RenamedMonoBinds), RnName(..)
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcMonoExpr )
+
+import DynFlags ( DynFlag(Opt_MonomorphismRestriction, Opt_GlasgowExts) )
+import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, LHsBind, Sig(..),
+ HsLocalBinds(..), HsValBinds(..), HsIPBinds(..),
+ LSig, Match(..), IPBind(..), Prag(..),
+ HsType(..), LHsType, HsExplicitForAll(..), hsLTyVarNames,
+ isVanillaLSig, sigName, placeHolderNames, isPragLSig,
+ LPat, GRHSs, MatchGroup(..), pprLHsBinds, mkHsCoerce,
+ collectHsBindBinders, collectPatBinders, pprPatBind, isBangHsBind
)
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcBind), SYN_IE(TcMonoBinds),
- TcIdOcc(..), SYN_IE(TcIdBndr) )
-
-import TcMonad hiding ( rnMtoTcM )
-import GenSpecEtc ( checkSigTyVars, genBinds, TcSigInfo(..) )
-import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..) )
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds )
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcPolyType )
-import TcPat ( tcPat )
+import TcHsSyn ( zonkId )
+
+import TcRnMonad
+import Inst ( newDictsAtLoc, newIPDict, instToId )
+import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
+ pprBinders, tcLookupLocalId_maybe, tcLookupId,
+ tcGetGlobalTyVars )
+import TcUnify ( tcInfer, tcSubExp, unifyTheta,
+ bleatEscapedTvs, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck,
+ tcSimplifyRestricted, tcSimplifyIPs )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
+import TcPat ( tcPat, PatCtxt(..) )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( newTcTyVar, tcInstSigType )
-import Unify ( unifyTauTy )
-
-import Kind ( mkBoxedTypeKind, mkTypeKind )
-import Id ( GenId, idType, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( assocMaybe, catMaybes )
-import Name ( pprNonSym, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Pretty
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy,
- mkSigmaTy, splitSigmaTy,
- splitRhoTy, mkForAllTy, splitForAllTy )
-import Util ( isIn, zipEqual, panic )
+import TcMType ( newFlexiTyVarTy, zonkQuantifiedTyVar, zonkSigTyVar,
+ tcInstSigTyVars, tcInstSkolTyVars, tcInstType,
+ zonkTcType, zonkTcTypes, zonkTcTyVars )
+import TcType ( TcType, TcTyVar, TcThetaType,
+ SkolemInfo(SigSkol), UserTypeCtxt(FunSigCtxt),
+ TcTauType, TcSigmaType, isUnboxedTupleType,
+ mkTyVarTy, mkForAllTys, mkFunTys, exactTyVarsOfType,
+ mkForAllTy, isUnLiftedType, tcGetTyVar,
+ mkTyVarTys, tidyOpenTyVar )
+import Kind ( argTypeKind )
+import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv )
+import TysWiredIn ( unitTy )
+import TysPrim ( alphaTyVar )
+import Id ( Id, mkLocalId, mkVanillaGlobal )
+import IdInfo ( vanillaIdInfo )
+import Var ( TyVar, idType, idName )
+import Name ( Name )
+import NameSet
+import NameEnv
+import VarSet
+import SrcLoc ( Located(..), unLoc, getLoc )
+import Bag
+import ErrUtils ( Message )
+import Digraph ( SCC(..), stronglyConnComp )
+import Maybes ( expectJust, isJust, isNothing, orElse )
+import Util ( singleton )
+import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
+ RecFlag(..), isNonRec, InlineSpec, defaultInlineSpec )
+import Outputable
\end{code}
+
%************************************************************************
%* *
\subsection{Type-checking bindings}
@tcBindsAndThen@ also takes a "combiner" which glues together the
bindings and the "thing" to make a new "thing".
-The real work is done by @tcBindAndThen@.
+The real work is done by @tcBindWithSigsAndThen@.
Recursive and non-recursive binds are handled in essentially the same
way: because of uniques there are no scoping issues left. The only
dictionaries, which we resolve at the module level.
\begin{code}
-tcBindsAndThen
- :: (TcHsBinds s -> thing -> thing) -- Combinator
- -> RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty)
- -> TcM s (thing, LIE s, thing_ty)
-
-tcBindsAndThen combiner EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc (combiner EmptyBinds thing, lie, thing_ty)
-
-tcBindsAndThen combiner (SingleBind bind) do_next
- = tcBindAndThen combiner bind [] do_next
+tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
+ -- Note: returning the TcLclEnv is more than we really
+ -- want. The bit we care about is the local bindings
+ -- and the free type variables thereof
+tcTopBinds binds
+ = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
+ ; return (foldr (unionBags . snd) emptyBag prs, env) }
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive LHsBinds
+
+tcHsBootSigs :: HsValBinds Name -> TcM [Id]
+-- A hs-boot file has only one BindGroup, and it only has type
+-- signatures in it. The renamer checked all this
+tcHsBootSigs (ValBindsOut binds sigs)
+ = do { checkTc (null binds) badBootDeclErr
+ ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
+ where
+ tc_boot_sig (TypeSig (L _ name) ty)
+ = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
+ -- Notice that we make GlobalIds, not LocalIds
+tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
+
+badBootDeclErr :: Message
+badBootDeclErr = ptext SLIT("Illegal declarations in an hs-boot file")
+
+------------------------
+tcLocalBinds :: HsLocalBinds Name -> TcM thing
+ -> TcM (HsLocalBinds TcId, thing)
+
+tcLocalBinds EmptyLocalBinds thing_inside
+ = do { thing <- thing_inside
+ ; return (EmptyLocalBinds, thing) }
+
+tcLocalBinds (HsValBinds binds) thing_inside
+ = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
+ ; return (HsValBinds binds', thing) }
+
+tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
+ = do { (thing, lie) <- getLIE thing_inside
+ ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
+
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ ; dict_binds <- tcSimplifyIPs avail_ips lie
+ ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
+ where
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (IPBind ip expr)
+ = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
+ newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
+ tcMonoExpr expr ty `thenM` \ expr' ->
+ returnM (ip_inst, (IPBind ip' expr'))
+
+------------------------
+tcValBinds :: TopLevelFlag
+ -> HsValBinds Name -> TcM thing
+ -> TcM (HsValBinds TcId, thing)
+
+tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside
+ = pprPanic "tcValBinds" (ppr binds)
+
+tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
+ = do { -- Typecheck the signature
+ ; let { prag_fn = mkPragFun sigs
+ ; ty_sigs = filter isVanillaLSig sigs
+ ; sig_fn = mkSigFun ty_sigs }
+
+ ; poly_ids <- mapM tcTySig ty_sigs
+
+ -- Extend the envt right away with all
+ -- the Ids declared with type signatures
+ ; (binds', thing) <- tcExtendIdEnv poly_ids $
+ tc_val_binds top_lvl sig_fn prag_fn
+ binds thing_inside
+
+ ; return (ValBindsOut binds' sigs, thing) }
+
+------------------------
+tc_val_binds :: TopLevelFlag -> TcSigFun -> TcPragFun
+ -> [(RecFlag, LHsBinds Name)] -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+-- Typecheck a whole lot of value bindings,
+-- one strongly-connected component at a time
+
+tc_val_binds top_lvl sig_fn prag_fn [] thing_inside
+ = do { thing <- thing_inside
+ ; return ([], thing) }
+
+tc_val_binds top_lvl sig_fn prag_fn (group : groups) thing_inside
+ = do { (group', (groups', thing))
+ <- tc_group top_lvl sig_fn prag_fn group $
+ tc_val_binds top_lvl sig_fn prag_fn groups thing_inside
+ ; return (group' ++ groups', thing) }
+
+------------------------
+tc_group :: TopLevelFlag -> TcSigFun -> TcPragFun
+ -> (RecFlag, LHsBinds Name) -> TcM thing
+ -> TcM ([(RecFlag, LHsBinds TcId)], thing)
+
+-- Typecheck one strongly-connected component of the original program.
+-- We get a list of groups back, because there may
+-- be specialisations etc as well
+
+tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
+ = -- A single non-recursive binding
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ do { (binds, thing) <- tcPolyBinds top_lvl NonRecursive NonRecursive
+ sig_fn prag_fn binds thing_inside
+ ; return ([(NonRecursive, b) | b <- binds], thing) }
+
+tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
+ = -- A recursive strongly-connected component
+ -- To maximise polymorphism (with -fglasgow-exts), we do a new
+ -- strongly-connected-component analysis, this time omitting
+ -- any references to variables with type signatures.
+ --
+ -- Then we bring into scope all the variables with type signatures
+ do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
+ ; gla_exts <- doptM Opt_GlasgowExts
+ ; (binds,thing) <- if gla_exts
+ then go new_sccs
+ else tc_binds Recursive binds thing_inside
+ ; return ([(Recursive, unionManyBags binds)], thing) }
+ -- Rec them all together
+ where
+ new_sccs :: [SCC (LHsBind Name)]
+ new_sccs = stronglyConnComp (mkEdges sig_fn binds)
-tcBindsAndThen combiner (BindWith bind sigs) do_next
- = tcBindAndThen combiner bind sigs do_next
+-- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], thing)
+ go (scc:sccs) = do { (binds1, (binds2, thing)) <- go1 scc (go sccs)
+ ; return (binds1 ++ binds2, thing) }
+ go [] = do { thing <- thing_inside; return ([], thing) }
-tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
-\end{code}
+ go1 (AcyclicSCC bind) = tc_binds NonRecursive (unitBag bind)
+ go1 (CyclicSCC binds) = tc_binds Recursive (listToBag binds)
-An aside. The original version of @tcBindsAndThen@ which lacks a
-combiner function, appears below. Though it is perfectly well
-behaved, it cannot be typed by Haskell, because the recursive call is
-at a different type to the definition itself. There aren't too many
-examples of this, which is why I thought it worth preserving! [SLPJ]
+ tc_binds rec_tc binds = tcPolyBinds top_lvl Recursive rec_tc sig_fn prag_fn binds
-\begin{pseudocode}
-tcBindsAndThen
- :: RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty))
- -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
+------------------------
+mkEdges :: TcSigFun -> LHsBinds Name
+ -> [(LHsBind Name, BKey, [BKey])]
-tcBindsAndThen EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
+type BKey = Int -- Just number off the bindings
-tcBindsAndThen (SingleBind bind) do_next
- = tcBindAndThen bind [] do_next
+mkEdges sig_fn binds
+ = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
+ Just key <- [lookupNameEnv key_map n], no_sig n ])
+ | (bind, key) <- keyd_binds
+ ]
+ where
+ no_sig :: Name -> Bool
+ no_sig n = isNothing (sig_fn n)
+
+ keyd_binds = bagToList binds `zip` [0::BKey ..]
+
+ key_map :: NameEnv BKey -- Which binding it comes from
+ key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
+ , bndr <- bindersOfHsBind bind ]
+
+bindersOfHsBind :: HsBind Name -> [Name]
+bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
+bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
+
+------------------------
+tcPolyBinds :: TopLevelFlag
+ -> RecFlag -- Whether the group is really recursive
+ -> RecFlag -- Whether it's recursive for typechecking purposes
+ -> TcSigFun -> TcPragFun
+ -> LHsBinds Name
+ -> TcM thing
+ -> TcM ([LHsBinds TcId], thing)
+
+-- Typechecks a single bunch of bindings all together,
+-- and generalises them. The bunch may be only part of a recursive
+-- group, because we use type signatures to maximise polymorphism
+--
+-- Deals with the bindInstsOfLocalFuns thing too
+--
+-- Returns a list because the input may be a single non-recursive binding,
+-- in which case the dependency order of the resulting bindings is
+-- important.
+
+tcPolyBinds top_lvl rec_group rec_tc sig_fn prag_fn scc thing_inside
+ = -- NB: polymorphic recursion means that a function
+ -- may use an instance of itself, we must look at the LIE arising
+ -- from the function's own right hand side. Hence the getLIE
+ -- encloses the tc_poly_binds.
+ do { traceTc (text "tcPolyBinds" <+> ppr scc)
+ ; ((binds1, poly_ids, thing), lie) <- getLIE $
+ do { (binds1, poly_ids) <- tc_poly_binds top_lvl rec_group rec_tc
+ sig_fn prag_fn scc
+ ; thing <- tcExtendIdEnv poly_ids thing_inside
+ ; return (binds1, poly_ids, thing) }
+
+ ; if isTopLevel top_lvl
+ then -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop,
+ -- and quite a bit faster too
+ do { extendLIEs lie; return (binds1, thing) }
+
+ else do -- Nested case
+ { lie_binds <- bindInstsOfLocalFuns lie poly_ids
+ ; return (binds1 ++ [lie_binds], thing) }}
+
+------------------------
+tc_poly_binds :: TopLevelFlag -- See comments on tcPolyBinds
+ -> RecFlag -> RecFlag
+ -> TcSigFun -> TcPragFun
+ -> LHsBinds Name
+ -> TcM ([LHsBinds TcId], [TcId])
+-- Typechecks the bindings themselves
+-- Knows nothing about the scope of the bindings
+
+tc_poly_binds top_lvl rec_group rec_tc sig_fn prag_fn binds
+ = let
+ binder_names = collectHsBindBinders binds
+ bind_list = bagToList binds
+
+ loc = getLoc (head bind_list)
+ -- TODO: location a bit awkward, but the mbinds have been
+ -- dependency analysed and may no longer be adjacent
+ in
+ -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+ setSrcSpan loc $
+ recoverM (recoveryCode binder_names) $ do
+
+ { traceTc (ptext SLIT("------------------------------------------------"))
+ ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
+
+ -- TYPECHECK THE BINDINGS
+ ; ((binds', mono_bind_infos), lie_req)
+ <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
+
+ -- CHECK FOR UNLIFTED BINDINGS
+ -- These must be non-recursive etc, and are not generalised
+ -- They desugar to a case expression in the end
+ ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
+ ; is_strict <- checkStrictBinds top_lvl rec_group binds'
+ zonked_mono_tys mono_bind_infos
+ ; if is_strict then
+ do { extendLIEs lie_req
+ ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
+ mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
+ mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, [])
+ -- ToDo: prags for unlifted bindings
+
+ ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
+ [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
+
+ else do -- The normal lifted case: GENERALISE
+ { is_unres <- isUnRestrictedGroup bind_list sig_fn
+ ; (tyvars_to_gen, dict_binds, dict_ids)
+ <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
+ generalise top_lvl is_unres mono_bind_infos lie_req
+
+ -- FINALISE THE QUANTIFIED TYPE VARIABLES
+ -- The quantified type variables often include meta type variables
+ -- we want to freeze them into ordinary type variables, and
+ -- default their kind (e.g. from OpenTypeKind to TypeKind)
+ ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
+
+ -- BUILD THE POLYMORPHIC RESULT IDs
+ ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids))
+ mono_bind_infos
+
+ -- ZONK THE poly_ids, because they are used to extend the type
+ -- environment; see the invariant on TcEnv.tcExtendIdEnv
+ ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
+ ; zonked_poly_ids <- mappM zonkId poly_ids
+
+ ; traceTc (text "binding:" <+> ppr (zonked_poly_ids `zip` map idType zonked_poly_ids))
+
+ ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
+ dict_ids exports
+ (dict_binds `unionBags` binds')
+
+ ; return ([unitBag abs_bind], zonked_poly_ids)
+ } }
+
+
+--------------
+mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo
+ -> TcM ([TyVar], Id, Id, [Prag])
+mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
+ = case mb_sig of
+ Nothing -> do { prags <- tcPrags poly_id (prag_fn poly_name)
+ ; return (inferred_tvs, poly_id, mono_id, prags) }
+ where
+ poly_id = mkLocalId poly_name poly_ty
+ poly_ty = mkForAllTys inferred_tvs
+ $ mkFunTys dict_tys
+ $ idType mono_id
+
+ Just sig -> do { let poly_id = sig_id sig
+ ; prags <- tcPrags poly_id (prag_fn poly_name)
+ ; sig_tys <- zonkTcTyVars (sig_tvs sig)
+ ; let sig_tvs' = map (tcGetTyVar "mkExport") sig_tys
+ ; return (sig_tvs', poly_id, mono_id, prags) }
+ -- We zonk the sig_tvs here so that the export triple
+ -- always has zonked type variables;
+ -- a convenient invariant
+
+
+------------------------
+type TcPragFun = Name -> [LSig Name]
+
+mkPragFun :: [LSig Name] -> TcPragFun
+mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
+ where
+ prs = [(expectJust "mkPragFun" (sigName sig), sig)
+ | sig <- sigs, isPragLSig sig]
+ env = foldl add emptyNameEnv prs
+ add env (n,p) = extendNameEnv_Acc (:) singleton env n p
-tcBindsAndThen (BindWith bind sigs) do_next
- = tcBindAndThen bind sigs do_next
+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
+
+pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
+
+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)
+
+
+tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
+tcSpecPrag poly_id hs_ty inl
+ = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
+ ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
+ ; extendLIEs lie
+ ; let const_dicts = map instToId lie
+ ; return (SpecPrag (mkHsCoerce co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
+
+--------------
+-- If typechecking the binds fails, then return with each
+-- signature-less binder given type (forall a.a), to minimise
+-- subsequent error messages
+recoveryCode binder_names
+ = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
+ ; poly_ids <- mapM mk_dummy binder_names
+ ; return ([], poly_ids) }
+ where
+ mk_dummy name = do { mb_id <- tcLookupLocalId_maybe name
+ ; case mb_id of
+ Just id -> return id -- Had signature, was in envt
+ Nothing -> return (mkLocalId name forall_a_a) } -- No signature
+
+forall_a_a :: TcType
+forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
+
+
+-- Check that non-overloaded unlifted bindings are
+-- a) non-recursive,
+-- b) not top level,
+-- c) not a multiple-binding group (more or less implied by (a))
+
+checkStrictBinds :: TopLevelFlag -> RecFlag
+ -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
+ -> TcM Bool
+checkStrictBinds top_lvl rec_group mbind mono_tys infos
+ | unlifted || bang_pat
+ = do { checkTc (isNotTopLevel top_lvl)
+ (strictBindErr "Top-level" unlifted mbind)
+ ; checkTc (isNonRec rec_group)
+ (strictBindErr "Recursive" unlifted mbind)
+ ; checkTc (isSingletonBag mbind)
+ (strictBindErr "Multiple" unlifted mbind)
+ ; mapM_ check_sig infos
+ ; return True }
+ | otherwise
+ = return False
+ where
+ unlifted = any isUnLiftedType mono_tys
+ bang_pat = anyBag (isBangHsBind . unLoc) mbind
+ check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
+ (badStrictSig unlifted sig)
+ check_sig other = return ()
+
+strictBindErr flavour unlifted mbind
+ = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:")) 4 (ppr mbind)
+ where
+ msg | unlifted = ptext SLIT("bindings for unlifted types")
+ | otherwise = ptext SLIT("bang-pattern bindings")
-tcBindsAndThen (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
+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}
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-\end{pseudocode}
%************************************************************************
%* *
-\subsection{Bind}
+\subsection{tcMonoBind}
%* *
%************************************************************************
+@tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
+The signatures have been dealt with already.
+
\begin{code}
-tcBindAndThen
- :: (TcHsBinds s -> thing -> thing) -- Combinator
- -> RenamedBind -- The Bind to typecheck
- -> [RenamedSig] -- ...and its signatures
- -> TcM s (thing, LIE s, thing_ty) -- Thing to type check in
- -- augmented envt
- -> TcM s (thing, LIE s, thing_ty) -- Results, incl the
-
-tcBindAndThen combiner bind sigs do_next
- = fixTc (\ ~(prag_info_fn, _) ->
- -- This is the usual prag_info fix; the PragmaInfo field of an Id
- -- is not inspected till ages later in the compiler, so there
- -- should be no black-hole problems here.
-
- tcBindAndSigs binder_names bind
- sigs prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
-
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv binder_names poly_ids $
-
- -- Build bindings and IdInfos corresponding to user pragmas
- tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
-
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie, thing_ty) ->
-
- -- Create specialisations of functions bound here
- bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
- poly_ids `thenTc` \ (lie2, inst_mbinds) ->
-
- -- All done
- let
- final_lie = lie2 `plusLIE` poly_lie
- final_binds = poly_binds `ThenBinds`
- SingleBind (NonRecBind inst_mbinds) `ThenBinds`
- prag_binds
- in
- returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty))
- ) `thenTc` \ (_, result) ->
- returnTc result
+tcMonoBinds :: [LHsBind Name]
+ -> TcSigFun
+ -> RecFlag -- Whether the binding is recursive for typechecking purposes
+ -- i.e. the binders are mentioned in their RHSs, and
+ -- we are not resuced by a type signature
+ -> TcM (LHsBinds TcId, [MonoBindInfo])
+
+tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
+ fun_matches = matches, bind_fvs = fvs })]
+ sig_fn -- Single function binding,
+ NonRecursive -- binder isn't mentioned in RHS,
+ | Nothing <- sig_fn name -- ...with no type signature
+ = -- In this very special case we infer the type of the
+ -- right hand side first (it may have a higher-rank type)
+ -- and *then* make the monomorphic Id for the LHS
+ -- e.g. f = \(x::forall a. a->a) -> <body>
+ -- We want to infer a higher-rank type for f
+ setSrcSpan b_loc $
+ do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name matches)
+
+ -- Check for an unboxed tuple type
+ -- f = (# True, False #)
+ -- Zonk first just in case it's hidden inside a meta type variable
+ -- (This shows up as a (more obscure) kind error
+ -- in the 'otherwise' case of tcMonoBinds.)
+ ; zonked_rhs_ty <- zonkTcType rhs_ty
+ ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
+ (unboxedTupleErr name zonked_rhs_ty)
+
+ ; mono_name <- newLocalName name
+ ; let mono_id = mkLocalId mono_name zonked_rhs_ty
+ ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
+ fun_matches = matches', bind_fvs = fvs,
+ fun_co_fn = co_fn })),
+ [(name, Nothing, mono_id)]) }
+
+tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
+ fun_matches = matches, bind_fvs = fvs })]
+ sig_fn -- Single function binding
+ non_rec
+ | Just sig <- sig_fn name -- ...with a type signature
+ = -- When we have a single function binding, with a type signature
+ -- we can (a) use genuine, rigid skolem constants for the type variables
+ -- (b) bring (rigid) scoped type variables into scope
+ setSrcSpan b_loc $
+ do { tc_sig <- tcInstSig True sig
+ ; mono_name <- newLocalName name
+ ; let mono_ty = sig_tau tc_sig
+ mono_id = mkLocalId mono_name mono_ty
+ rhs_tvs = [ (name, mkTyVarTy tv)
+ | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
+
+ ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
+ tcMatchesFun mono_name matches mono_ty
+
+ ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
+ fun_infix = inf, fun_matches = matches',
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn }
+ ; return (unitBag (L b_loc fun_bind'),
+ [(name, Just tc_sig, mono_id)]) }
+
+tcMonoBinds binds sig_fn non_rec
+ = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
+
+ -- Bring the monomorphic Ids, into scope for the RHSs
+ ; let mono_info = getMonoBindInfo tc_binds
+ rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
+ -- A monomorphic binding for each term variable that lacks
+ -- a type sig. (Ones with a sig are already in scope.)
+
+ ; binds' <- tcExtendIdEnv2 rhs_id_env $
+ traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
+ | (n,id) <- rhs_id_env]) `thenM_`
+ mapM (wrapLocM tcRhs) tc_binds
+ ; return (listToBag binds', mono_info) }
+
+------------------------
+-- tcLhs typechecks the LHS of the bindings, to construct the environment in which
+-- we typecheck the RHSs. Basically what we are doing is this: for each binder:
+-- if there's a signature for it, use the instantiated signature type
+-- otherwise invent a type variable
+-- You see that quite directly in the FunBind case.
+--
+-- But there's a complication for pattern bindings:
+-- data T = MkT (forall a. a->a)
+-- MkT f = e
+-- Here we can guess a type variable for the entire LHS (which will be refined to T)
+-- but we want to get (f::forall a. a->a) as the RHS environment.
+-- The simplest way to do this is to typecheck the pattern, and then look up the
+-- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
+-- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
+
+data TcMonoBind -- Half completed; LHS done, RHS not done
+ = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
+ | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
+
+type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
+ -- Type signature (if any), and
+ -- the monomorphic bound things
+
+bndrNames :: [MonoBindInfo] -> [Name]
+bndrNames mbi = [n | (n,_,_) <- mbi]
+
+getMonoType :: MonoBindInfo -> TcTauType
+getMonoType (_,_,mono_id) = idType mono_id
+
+tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
+tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
+ = do { mb_sig <- tcInstSig_maybe (sig_fn name)
+ ; mono_name <- newLocalName name
+ ; mono_ty <- mk_mono_ty mb_sig
+ ; let mono_id = mkLocalId mono_name mono_ty
+ ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
where
- binder_names = collectBinders bind
+ mk_mono_ty (Just sig) = return (sig_tau sig)
+ 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
-tcBindAndSigs binder_rn_names bind sigs prag_info_fn
- = let
- binder_names = map de_rn binder_rn_names
- de_rn (RnName n) = n
- in
- recoverTc (
- -- If typechecking the binds fails, then return with each
- -- binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
- let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- poly_ids = [ mkUserId name forall_a_a (prag_info_fn name)
- | name <- binder_names]
- in
- returnTc (EmptyBinds, emptyLIE, poly_ids)
- ) $
-
- -- Create a new identifier for each binder, with each being given
- -- a type-variable type.
- newMonoIds binder_rn_names kind (\ mono_ids ->
- tcTySigs sigs `thenTc` \ sig_info ->
- tc_bind bind `thenTc` \ (bind', lie) ->
- returnTc (mono_ids, bind', lie, sig_info)
- )
- `thenTc` \ (mono_ids, bind', lie, sig_info) ->
-
- -- Notice that genBinds gets the old (non-extended) environment
- genBinds binder_names mono_ids bind' lie sig_info prag_info_fn
- where
- kind = case bind of
- NonRecBind _ -> mkTypeKind -- Recursive, so no unboxed types
- RecBind _ -> mkBoxedTypeKind -- Non-recursive, so we permit unboxed types
-\end{code}
+ ; 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
+ 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.
-===========
-\begin{code}
-{-
+ -- 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) }
-data SigInfo
- = SigInfo RnName
- (TcIdBndr s) -- Polymorpic version
- (TcIdBndr s) -- Monomorphic verstion
- [TcType s] [TcIdOcc s] -- Instance information for the monomorphic version
-
-
-
- -- Deal with type signatures
- tcTySigs sigs `thenTc` \ sig_infos ->
- let
- sig_binders = [binder | SigInfo binder _ _ _ _ <- sig_infos]
- poly_sigs = [(name,poly) | SigInfo name poly _ _ _ <- sig_infos]
- mono_sigs = [(name,mono) | SigInfo name _ mono _ _ <- sig_infos]
- nosig_binders = binders `minusList` sig_binders
- in
+ ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
+ tcInfer tc_pat
+ ; return (TcPatBind infos pat' grhss pat_ty) }
+ where
+ names = collectPatBinders pat
- -- Typecheck the binding group
- tcExtendLocalEnv poly_sigs (
- newMonoIds nosig_binders kind (\ nosig_local_ids ->
- tcMonoBinds mono_sigs mono_binds `thenTc` \ binds_w_lies ->
- returnTc (nosig_local_ids, binds_w_lies)
- )) `thenTc` \ (nosig_local_ids, binds_w_lies) ->
+tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
+ -- AbsBind, VarBind impossible
- -- Decide what to generalise over
- getImplicitStuffToGen sig_ids binds_w_lies
- `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen, lie_to_gen) ->
+-------------------
+tcRhs :: TcMonoBind -> TcM (HsBind TcId)
+tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
+ = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) matches
+ (idType mono_id)
+ ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
+ bind_fvs = placeHolderNames, fun_co_fn = co_fn }) }
+tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
+ = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
+ tcGRHSsPat grhss pat_ty
+ ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
+ bind_fvs = placeHolderNames }) }
- *** CHECK FOR UNBOXED TYVARS HERE! ***
+---------------------
+getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
+getMonoBindInfo tc_binds
+ = foldr (get_info . unLoc) [] tc_binds
+ where
+ get_info (TcFunBind info _ _ _) rest = info : rest
+ get_info (TcPatBind infos _ _ _) rest = infos ++ rest
+\end{code}
- -- Make poly_ids for all the binders that don't have type signatures
- let
- tys_to_gen = mkTyVarTys tyvars_to_gen
- dicts_to_gen = map instToId (bagToList lie_to_gen)
- dict_tys = map tcIdType dicts_to_gen
+%************************************************************************
+%* *
+ Generalisation
+%* *
+%************************************************************************
- mk_poly binder local_id = mkUserId (getName binder) ty noPragmaInfo
- where
- ty = mkForAllTys tyvars_to_gen $
- mkFunTys dict_tys $
- tcIdType local_id
+\begin{code}
+generalise :: TopLevelFlag -> Bool
+ -> [MonoBindInfo] -> [Inst]
+ -> TcM ([TcTyVar], TcDictBinds, [TcId])
+generalise top_lvl is_unrestricted mono_infos lie_req
+ | not is_unrestricted -- RESTRICTED CASE
+ = -- Check signature contexts are empty
+ do { checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr bndrs)
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
+ tau_tvs lie_req
+
+ -- Check that signature type variables are OK
+ ; final_qtvs <- checkSigsTyVars qtvs sigs
+
+ ; return (final_qtvs, binds, []) }
+
+ | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
+ = tcSimplifyInfer doc tau_tvs lie_req
+
+ | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
+ = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty
+ ; let -- The "sig_avails" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the lie_avail
+ -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
+ local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
+ sig_avails = sig_lie ++ local_meths
+
+ -- Check that the needed dicts can be
+ -- expressed in terms of the signature ones
+ ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
+
+ -- Check that signature type variables are OK
+ ; final_qtvs <- checkSigsTyVars forall_tvs sigs
+
+ ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
+ where
+ bndrs = bndrNames mono_infos
+ sigs = [sig | (_, Just sig, _) <- mono_infos]
+ tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos
+ -- NB: exactTyVarsOfType; see Note [Silly type synonym]
+ -- near defn of TcType.exactTyVarsOfType
+ is_mono_sig sig = null (sig_theta sig)
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs
+
+ mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
+ sig_theta = theta, sig_loc = loc }) mono_id
+ = Method mono_id poly_id (mkTyVarTys tvs) theta loc
+\end{code}
- more_sig_infos = [ SigInfo binder (mk_poly binder local_id)
- local_id tys_to_gen dicts_to_gen lie_to_gen
- | (binder, local_id) <- zipEqual "???" nosig_binders nosig_local_ids
- ]
+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).
- all_sig_infos = sig_infos ++ more_sig_infos -- Contains a "signature" for each binder
- in
+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.
- -- Now generalise the bindings
- let
- -- local_binds is a bunch of bindings of the form
- -- f_mono = f_poly tyvars dicts
- -- one for each binder, f, that lacks a type signature.
- -- This bunch of bindings is put at the top of the RHS of every
- -- binding in the group, so as to bind all the f_monos.
-
- local_binds = [ (local_id, mkHsDictApp (mkHsTyApp (HsVar local_id) tys_to_gen) dicts_to_gen)
- | local_id <- nosig_local_ids
- ]
-
- find_sig lid = head [ (pid, tvs, ds, lie)
- | SigInfo _ pid lid' tvs ds lie,
- lid==lid'
- ]
-
- gen_bind (bind, lie)
- = tcSimplifyWithExtraGlobals tyvars_not_to_gen tyvars_to_gen avail lie
- `thenTc` \ (lie_free, dict_binds) ->
- returnTc (AbsBind tyvars_to_gen_here
- dicts
- (zipEqual "gen_bind" local_ids poly_ids)
- (dict_binds ++ local_binds)
- bind,
- lie_free)
- where
- local_ids = bindersOf bind
- local_sigs = [sig | sig@(SigInfo _ _ local_id _ _) <- all_sig_infos,
- local_id `elem` local_ids
- ]
+\begin{code}
+unifyCtxts :: [TcSigInfo] -> TcM [Inst]
+unifyCtxts (sig1 : sigs) -- Argument is always non-empty
+ = do { mapM unify_ctxt sigs
+ ; newDictsAtLoc (sig_loc sig1) (sig_theta sig1) }
+ where
+ theta1 = sig_theta sig1
+ unify_ctxt :: TcSigInfo -> TcM ()
+ unify_ctxt sig@(TcSigInfo { sig_theta = theta })
+ = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
+ addErrCtxt (sigContextsCtxt sig1 sig) $
+ unifyTheta theta1 theta
+
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs
+ = do { gbl_tvs <- tcGetGlobalTyVars
+ ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
+
+ ; let -- Sigh. Make sure that all the tyvars in the type sigs
+ -- appear in the returned ty var list, which is what we are
+ -- going to generalise over. Reason: we occasionally get
+ -- silly types like
+ -- type T a = () -> ()
+ -- f :: T a
+ -- f () = ()
+ -- Here, 'a' won't appear in qtvs, so we have to add it
+ sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
+ all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
+ ; returnM all_tvs }
+ where
+ check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
+ sig_theta = theta, sig_tau = tau})
+ = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
+ addErrCtxtM (sigCtxt id tvs theta tau) $
+ do { tvs' <- checkDistinctTyVars tvs
+ ; ifM (any (`elemVarSet` gbl_tvs) tvs')
+ (bleatEscapedTvs gbl_tvs tvs tvs')
+ ; return tvs' }
+
+checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
+-- (checkDistinctTyVars tvs) checks that the tvs from one type signature
+-- are still all type variables, and all distinct from each other.
+-- It returns a zonked set of type variables.
+-- For example, if the type sig is
+-- f :: forall a b. a -> b -> b
+-- we want to check that 'a' and 'b' haven't
+-- (a) been unified with a non-tyvar type
+-- (b) been unified with each other (all distinct)
+
+checkDistinctTyVars sig_tvs
+ = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
+ ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
+ ; return zonked_tvs }
+ where
+ check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
+ -- The TyVarEnv maps each zonked type variable back to its
+ -- corresponding user-written signature type variable
+ check_dup acc (sig_tv, zonked_tv)
+ = case lookupVarEnv acc zonked_tv of
+ Just sig_tv' -> bomb_out sig_tv sig_tv'
- (tyvars_to_gen_here, dicts, avail)
- = case (local_ids, sigs) of
+ Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
- ([local_id], [SigInfo _ _ _ tyvars_to_gen dicts lie])
- -> (tyvars_to_gen, dicts, lie)
+ 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}
- other -> (tyvars_to_gen, dicts, avail)
-\end{code}
-@getImplicitStuffToGen@ decides what type variables
-and LIE to generalise over.
+@getTyVarsToGen@ decides what type variables to generalise over.
For a "restricted group" -- see the monomorphism restriction
for a definition -- we bind no dictionaries, and
we'll know that the literals are all Ints, and we can just produce
Int literals!
-Find all the type variables involved in overloading, the "constrained_tyvars"
-These are the ones we *aren't* going to generalise.
-We must be careful about doing this:
+Find all the type variables involved in overloading, the
+"constrained_tyvars". These are the ones we *aren't* going to
+generalise. We must be careful about doing this:
+
(a) If we fail to generalise a tyvar which is not actually
constrained, then it will never, ever get bound, and lands
up printed out in interface files! Notorious example:
Another, more common, example is when there's a Method inst in
the LIE, whose type might very well involve non-overloaded
type variables.
+ [NOTE: Jan 2001: I don't understand the problem here so I'm doing
+ the simple thing instead]
+
(b) On the other hand, we mustn't generalise tyvars which are constrained,
because we are going to pass on out the unmodified LIE, with those
tyvars in it. They won't be in scope if we've generalised them.
constrained tyvars. We don't use any of the results, except to
find which tyvars are constrained.
-\begin{code}
-getImplicitStuffToGen is_restricted sig_ids binds_w_lies
- | isUnRestrictedGroup tysig_vars bind
- = tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, dicts_to_gen) ->
- returnNF_Tc (emptyTyVarSet, tyvars_to_gen, dicts_to_gen)
-
- | otherwise
- = tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
- let
- -- ASSERT: dicts_sig is already zonked!
- constrained_tyvars = foldBag unionTyVarSets tyVarsOfInst emptyTyVarSet constrained_dicts
- reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars
- in
- returnTc (constrained_tyvars, reduced_tyvars_to_gen, emptyLIE)
+Note [Polymorphic recursion]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
- where
- sig_vars = [sig_var | (TySigInfo sig_var _ _ _ _) <- ty_sigs]
-
- (tyvars_to_gen, lie) = foldBag (\(tv1,lie2) (tv2,lie2) -> (tv1 `unionTyVarSets` tv2,
- lie1 `plusLIE` lie2))
- get
- (emptyTyVarSet, emptyLIE)
- binds_w_lies
- get (bind, lie)
- = case bindersOf bind of
- [local_id] | local_id `in` sig_ids -> -- A simple binding with
- -- a type signature
- (emptyTyVarSet, emptyLIE)
-
- local_ids -> -- Complex binding or no type sig
- (foldr (unionTyVarSets . tcIdType) emptyTyVarSet local_ids,
- lie)
--}
-\end{code}
-
+ * 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:
-\begin{code}
-tc_bind :: RenamedBind -> TcM s (TcBind s, LIE s)
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
-tc_bind (NonRecBind mono_binds)
- = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (NonRecBind mono_binds2, lie)
+If we don't take care, after typechecking we get
-tc_bind (RecBind mono_binds)
- = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (RecBind mono_binds2, lie)
-\end{code}
-
-\begin{code}
-tcMonoBinds :: RenamedMonoBinds -> TcM s (TcMonoBinds s, LIE s)
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
-tcMonoBinds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
+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)
-tcMonoBinds (AndMonoBinds mb1 mb2)
- = tcMonoBinds mb1 `thenTc` \ (mb1a, lie1) ->
- tcMonoBinds mb2 `thenTc` \ (mb2a, lie2) ->
- returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
-tcMonoBinds bind@(PatMonoBind pat grhss_and_binds locn)
- = tcAddSrcLoc locn $
+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.
- -- LEFT HAND SIDE
- tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
+ ff = f Int dEqInt
- -- BINDINGS AND GRHSS
- tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds2, lie, grhss_ty) ->
-
- -- Unify the two sides
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- unifyTauTy pat_ty grhss_ty `thenTc_`
-
- -- RETURN
- returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
- plusLIE lie_pat lie)
-
-tcMonoBinds (FunMonoBind name inf matches locn)
- = tcAddSrcLoc locn $
- tcLookupLocalValueOK "tcMonoBinds" name `thenNF_Tc` \ id ->
- tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
- returnTc (FunMonoBind (TcId id) inf matches' locn, lie)
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Signatures}
-%* *
-%************************************************************************
+ = let f' = f Int dEqInt in \ys. ...f'...
-@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.
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
-\begin{code}
-tcTySigs :: [RenamedSig] -> TcM s [TcSigInfo s]
+Etc.
-tcTySigs (Sig v ty _ src_loc : other_sigs)
- = tcAddSrcLoc src_loc (
- tcPolyType ty `thenTc` \ sigma_ty ->
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' ->
- let
- (tyvars', theta', tau') = splitSigmaTy sigma_ty'
- in
+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
- tcLookupLocalValueOK "tcSig1" v `thenNF_Tc` \ val ->
- unifyTauTy (idType val) tau' `thenTc_`
+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.
- returnTc (TySigInfo val tyvars' theta' tau' src_loc)
- ) `thenTc` \ sig_info1 ->
+Then we get
- tcTySigs other_sigs `thenTc` \ sig_infos ->
- returnTc (sig_info1 : sig_infos)
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
-tcTySigs (other : sigs) = tcTySigs sigs
-tcTySigs [] = returnTc []
-\end{code}
%************************************************************************
%* *
-\subsection{SPECIALIZE pragmas}
+ Signatures
%* *
%************************************************************************
+Type signatures are tricky. See Note [Signature skolems] in TcType
-@tcPragmaSigs@ munches up the "signatures" that arise through *user*
-pragmas. It is convenient for them to appear in the @[RenamedSig]@
-part of a binding because then the same machinery can be used for
-moving them into place as is done for type signatures.
-
-\begin{code}
-tcPragmaSigs :: [RenamedSig] -- The pragma signatures
- -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
- TcHsBinds s,
- LIE s)
-
-tcPragmaSigs sigs = returnTc ( \name -> NoPragmaInfo, EmptyBinds, emptyLIE )
-
-{-
-tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
- let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
- in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
-
-\begin{code}
-tcPragmaSig (DeforestSig name loc)
- = returnTc ((name, addInfo DoDeforest),EmptyBinds,emptyLIE)
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addInfo_UF (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addInfo_UF (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
-\end{code}
+@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 interesting case is for SPECIALISE pragmas. There are two forms.
-Here's the first form:
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b #-}
-\end{verbatim}
-
-For this we generate:
-\begin{verbatim}
- f* = /\ b -> let d1 = ...
- in f Int b d1
-\end{verbatim}
-
-where f* is a SpecPragmaId. The **sole** purpose of SpecPragmaIds is to
-retain a right-hand-side that the simplifier will otherwise discard as
-dead code... the simplifier has a flag that tells it not to discard
-SpecPragmaId bindings.
-
-In this case the f* retains a call-instance of the overloaded
-function, f, (including appropriate dictionaries) so that the
-specialiser will subsequently discover that there's a call of @f@ at
-Int, and will create a specialisation for @f@. After that, the
-binding for @f*@ can be discarded.
-
-The second form is this:
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b = g #-}
-\end{verbatim}
-
-Here @g@ is specified as a function that implements the specialised
-version of @f@. Suppose that g has type (a->b->b); that is, g's type
-is more general than that required. For this we generate
-\begin{verbatim}
- f@Int = /\b -> g Int b
- f* = f@Int
-\end{verbatim}
-
-Here @f@@Int@ is a SpecId, the specialised version of @f@. It inherits
-f's export status etc. @f*@ is a SpecPragmaId, as before, which just serves
-to prevent @f@@Int@ from being discarded prematurely. After specialisation,
-if @f@@Int@ is going to be used at all it will be used explicitly, so the simplifier can
-discard the f* binding.
-
-Actually, there is really only point in giving a SPECIALISE pragma on exported things,
-and the simplifer won't discard SpecIds for exporte things anyway, so maybe this is
-a bit of overkill.
+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}
-tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
-
- -- Get and instantiate its alleged specialised type
- tcPolyType poly_ty `thenTc` \ sig_sigma ->
- tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
- let
- (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
- origin = ValSpecOrigin name
- in
-
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (null sig_theta)
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
-
- -- Get and instantiate the type of the id mentioned
- tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
- tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty ->
- let
- (main_tyvars, main_rho) = splitForAllTy main_ty
- (main_theta,main_tau) = splitRhoTy main_rho
- main_arg_tys = mkTyVarTys main_tyvars
- in
+type TcSigFun = Name -> Maybe (LSig Name)
- -- Check that the specialised type is indeed an instance of
- -- the type of the main function.
- unifyTauTy sig_tau main_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Check that the type variables of the polymorphic function are
- -- either left polymorphic, or instantiate to ground type.
- -- Also check that the overloaded type variables are instantiated to
- -- ground type; or equivalently that all dictionaries have ground type
- mapTc zonkTcType main_arg_tys `thenNF_Tc` \ main_arg_tys' ->
- zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' ->
- tcAddErrCtxt (specGroundnessCtxt main_arg_tys')
- (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_`
- tcAddErrCtxt (specContextGroundnessCtxt main_theta')
- (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_`
-
- -- Build the SpecPragmaId; it is the thing that makes sure we
- -- don't prematurely dead-code-eliminate the binding we are really interested in.
- newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_pragma_id ->
-
- -- Build a suitable binding; depending on whether we were given
- -- a value (Maybe Name) to be used as the specialisation.
- case using of
- Nothing -> -- No implementation function specified
-
- -- Make a Method inst for the occurrence of the overloaded function
- newMethodWithGivenTy (OccurrenceOf name)
- (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) ->
-
- let
- pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs
- pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id))
- in
- returnTc (pseudo_bind, lie, \ info -> info)
-
- Just spec_name -> -- Use spec_name as the specialisation value ...
-
- -- Type check a simple occurrence of the specialised Id
- tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
-
- -- Check that it has the correct type, and doesn't constrain the
- -- signature variables at all
- unifyTauTy sig_tau spec_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
-
- let
- spec_rhs = mkHsTyLam sig_tyvars spec_body
- spec_binds = VarMonoBind local_spec_id spec_rhs
- `AndMonoBinds`
- VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
- spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
- in
- returnTc ((name, addInfo spec_info), spec_binds, spec_lie)
--}
+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}
-
-%************************************************************************
-%* *
-\subsection[TcBinds-monomorphism]{The monomorphism restriction}
-%* *
-%************************************************************************
-
-Not exported:
-
\begin{code}
-isUnRestrictedGroup :: [TcIdBndr s] -- Signatures given for these
- -> TcBind s
- -> Bool
-
-isUnRestrictedGroup sigs EmptyBind = True
-isUnRestrictedGroup sigs (NonRecBind monobinds) = isUnResMono sigs monobinds
-isUnRestrictedGroup sigs (RecBind monobinds) = isUnResMono sigs monobinds
-
-is_elem v vs = isIn "isUnResMono" v vs
-
-isUnResMono sigs (PatMonoBind (VarPat (TcId v)) _ _) = v `is_elem` sigs
-isUnResMono sigs (PatMonoBind other _ _) = False
-isUnResMono sigs (VarMonoBind (TcId v) _) = v `is_elem` sigs
-isUnResMono sigs (FunMonoBind _ _ _ _) = True
-isUnResMono sigs (AndMonoBinds mb1 mb2) = isUnResMono sigs mb1 &&
- isUnResMono sigs mb2
-isUnResMono sigs EmptyMonoBinds = True
+tcTySig :: LSig Name -> TcM TcId
+tcTySig (L span (TypeSig (L _ name) ty))
+ = setSrcSpan span $
+ do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkLocalId name sigma_ty) }
+
+-------------------
+tcInstSig_maybe :: Maybe (LSig Name) -> TcM (Maybe TcSigInfo)
+-- Instantiate with *meta* type variables;
+-- this signature is part of a multi-signature group
+tcInstSig_maybe Nothing = return Nothing
+tcInstSig_maybe (Just sig) = do { tc_sig <- tcInstSig False sig
+ ; return (Just tc_sig) }
+
+tcInstSig :: Bool -> LSig Name -> TcM TcSigInfo
+-- Instantiate the signature, with either skolems or meta-type variables
+-- depending on the use_skols boolean
+--
+-- We always instantiate with freshs uniques,
+-- although we keep the same print-name
+--
+-- type T = forall a. [a] -> [a]
+-- f :: T;
+-- f = g where { g :: T; g = <rhs> }
+--
+-- We must not use the same 'a' from the defn of T at both places!!
+
+tcInstSig use_skols (L loc (TypeSig (L _ name) hs_ty))
+ = setSrcSpan loc $
+ do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
+ -- scope when starting the binding group
+ ; let skol_info = SigSkol (FunSigCtxt name)
+ inst_tyvars | use_skols = tcInstSkolTyVars skol_info
+ | otherwise = tcInstSigTyVars skol_info
+ ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
+ ; loc <- getInstLoc (SigOrigin skol_info)
+ ; return (TcSigInfo { sig_id = poly_id,
+ sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
+ sig_scoped = scoped_names, sig_loc = loc }) }
+ -- Note that the scoped_names and the sig_tvs will have
+ -- different Names. That's quite ok; when we bring the
+ -- scoped_names into scope, we just bind them to the sig_tvs
+ where
+ -- The scoped names are the ones explicitly mentioned
+ -- in the HsForAll. (There may be more in sigma_ty, because
+ -- of nested type synonyms. See Note [Scoped] with TcSigInfo.)
+ -- We also only have scoped type variables when we are instantiating
+ -- with true skolems
+ scoped_names = case (use_skols, hs_ty) of
+ (True, L _ (HsForAllTy Explicit tvs _ _)) -> hsLTyVarNames tvs
+ other -> []
+
+-------------------
+isUnRestrictedGroup :: [LHsBind Name] -> TcSigFun -> TcM Bool
+isUnRestrictedGroup binds sig_fn
+ = do { mono_restriction <- doptM Opt_MonomorphismRestriction
+ ; return (not mono_restriction || all_unrestricted) }
+ where
+ all_unrestricted = all (unrestricted . unLoc) binds
+ has_sig n = isJust (sig_fn n)
+
+ unrestricted (PatBind {}) = False
+ unrestricted (VarBind { var_id = v }) = has_sig v
+ unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
+ || has_sig (unLoc v)
+
+ unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
+ -- No args => like a pattern binding
+ unrestricted_match other = True
+ -- Some args => a function binding
\end{code}
\begin{code}
-patMonoBindsCtxt bind sty
- = ppHang (ppPStr SLIT("In a pattern binding:")) 4 (ppr sty bind)
-
---------------------------------------------
-specContextGroundnessCtxt -- err_ctxt dicts sty
- = panic "specContextGroundnessCtxt"
-{-
- = ppHang (
- ppSep [ppBesides [ppStr "In the SPECIALIZE pragma for `", ppr sty name, ppStr "'"],
- ppBesides [ppStr " specialised to the type `", ppr sty spec_ty, ppStr "'"],
- pp_spec_id sty,
- ppStr "... not all overloaded type variables were instantiated",
- ppStr "to ground types:"])
- 4 (ppAboves [ppCat [ppr sty c, ppr sty t]
- | (c,t) <- map getDictClassAndType dicts])
+-- This one is called on LHS, when pat and grhss are both Name
+-- and on RHS, when pat is TcId and grhss is still Name
+patMonoBindsCtxt pat grhss
+ = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
+
+-----------------------------------------------
+sigContextsCtxt sig1 sig2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
+ nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
+ ppr id2 <+> dcolon <+> ppr (idType id2)]),
+ ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
where
- (name, spec_ty, locn, pp_spec_id)
- = case err_ctxt of
- ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> ppNil)
- ValSpecSpecIdCtxt n ty spec loc ->
- (n, ty, loc,
- \ sty -> ppBesides [ppStr "... type of explicit id `", ppr sty spec, ppStr "'"])
--}
+ id1 = sig_id sig1
+ id2 = sig_id sig2
+
-----------------------------------------------
-specGroundnessCtxt
- = panic "specGroundnessCtxt"
+unboxedTupleErr name ty
+ = hang (ptext SLIT("Illegal binding of unboxed tuple"))
+ 4 (ppr name <+> dcolon <+> ppr ty)
+-----------------------------------------------
+restrictedBindCtxtErr binder_names
+ = hang (ptext SLIT("Illegal overloaded type signature(s)"))
+ 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
+ ptext SLIT("that falls under the monomorphism restriction")])
-valSpecSigCtxt v ty sty
- = ppHang (ppPStr SLIT("In a SPECIALIZE pragma for a value:"))
- 4 (ppSep [ppBeside (pprNonSym sty v) (ppPStr SLIT(" ::")),
- ppr sty ty])
+genCtxt binder_names
+ = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
\end{code}
-
projects / ghc-hetmet.git / blobdiff