%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where
+
#include "HsVersions.h"
-module TcBinds ( tcBindsAndThen, tcPragmaSigs, checkSigTyVars, tcBindWithSigs, TcSigInfo(..) ) where
-
-IMP_Ubiq()
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-#else
-import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
-#endif
-
-import HsSyn ( HsBinds(..), Sig(..), MonoBinds(..),
- Match, HsType, InPat(..), OutPat(..), HsExpr(..),
- SYN_IE(RecFlag), nonRecursive,
- GRHSsAndBinds, ArithSeqInfo, HsLit, Fake, Stmt, DoOrListComp, Fixity,
- collectMonoBinders )
-import RnHsSyn ( SYN_IE(RenamedHsBinds), RenamedSig(..),
- SYN_IE(RenamedMonoBinds)
- )
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcMonoBinds),
- TcIdOcc(..), SYN_IE(TcIdBndr), SYN_IE(TcExpr),
- tcIdType
- )
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho )
-import TcMonad
-import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..),
- newDicts, tyVarsOfInst, instToId
+import CmdLineOpts ( DynFlag(Opt_NoMonomorphismRestriction) )
+import HsSyn ( HsExpr(..), HsBind(..), LHsBind, LHsBinds, Sig(..),
+ LSig, Match(..), HsBindGroup(..), IPBind(..),
+ collectSigTysFromHsBinds, collectHsBindBinders,
)
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds,
- tcGetGlobalTyVars, tcExtendGlobalTyVars
+import TcHsSyn ( TcId, zonkId, mkHsLet )
+
+import TcRnMonad
+import Inst ( InstOrigin(..), newDicts, newIPDict, instToId )
+import TcEnv ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName )
+import TcUnify ( Expected(..), newHole, unifyTauTyLists, checkSigTyVarsWrt, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
+ tcSimplifyToDicts, tcSimplifyIPs )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..),
+ tcTySig, maybeSig, tcAddScopedTyVars
)
-import SpecEnv ( SpecEnv )
-import TcMatches ( tcMatchesFun )
-import TcSimplify ( tcSimplify, tcSimplifyAndCheck )
-import TcMonoType ( tcHsType )
-import TcPat ( tcPat )
+import TcPat ( tcPat, tcSubPat, tcMonoPatBndr )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( SYN_IE(TcType), SYN_IE(TcThetaType), SYN_IE(TcTauType),
- SYN_IE(TcTyVarSet), SYN_IE(TcTyVar),
- newTyVarTy, zonkTcType, zonkTcTyVar, zonkTcTyVars,
- newTcTyVar, tcInstSigType, newTyVarTys
+import TcMType ( newTyVar, newTyVarTy, zonkTcTyVarToTyVar )
+import TcType ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
+ mkPredTy, mkForAllTy, isUnLiftedType,
+ unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind
)
-import Unify ( unifyTauTy, unifyTauTyLists )
-
-import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind )
-import Id ( GenId, idType, mkUserLocal, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( maybeToBool, assocMaybe, catMaybes )
-import Name ( getOccName, getSrcLoc, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Pretty
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes, eqSimpleTheta,
- mkSigmaTy, splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy,
- splitRhoTy, mkForAllTy, splitForAllTy )
-import TyVar ( GenTyVar, SYN_IE(TyVar), tyVarKind, minusTyVarSet, emptyTyVarSet,
- elementOfTyVarSet, unionTyVarSets, tyVarSetToList )
-import Bag ( bagToList, foldrBag, isEmptyBag )
-import Util ( isIn, zipEqual, zipWithEqual, zipWith3Equal, hasNoDups, assoc,
- assertPanic, panic, pprTrace )
-import PprType ( GenClass, GenType, GenTyVar )
-import Unique ( Unique )
-import SrcLoc ( SrcLoc )
-
-import Outputable --( interppSP, interpp'SP )
-
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
+import Var ( idType, idName )
+import Name ( Name, getSrcLoc )
+import NameSet
+import Var ( tyVarKind )
+import VarSet
+import SrcLoc ( Located(..), srcLocSpan, unLoc, noLoc )
+import Bag
+import Util ( isIn, equalLength )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec,
+ isNotTopLevel, isAlwaysActive )
+import FiniteMap ( listToFM, lookupFM )
+import Outputable
\end{code}
dictionaries, which we resolve at the module level.
\begin{code}
-tcBindsAndThen
- :: (TcHsBinds s -> thing -> thing) -- Combinator
- -> RenamedHsBinds
- -> TcM s (thing, LIE s)
- -> TcM s (thing, LIE s)
-
-tcBindsAndThen combiner EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie) ->
- returnTc (combiner EmptyBinds thing, lie)
-
-tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
-
-tcBindsAndThen combiner (MonoBind bind sigs is_rec) 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.
+tcTopBinds :: [HsBindGroup Name] -> TcM (LHsBinds TcId, TcLclEnv)
+ -- Note: returning the TcLclEnv is more than we really
+ -- want. The bit we care about is the local bindings
+ -- and the free type variables thereof
+tcTopBinds binds
+ = tc_binds_and_then TopLevel glue binds $
+ getLclEnv `thenM` \ env ->
+ returnM (emptyBag, env)
+ where
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive MonoBinds
+ glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env)
+ -- Can't have a HsIPBinds at top level
- -- TYPECHECK THE SIGNATURES
- mapTc (tcTySig prag_info_fn) ty_sigs `thenTc` \ tc_ty_sigs ->
- tcBindWithSigs binder_names bind
- tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+tcBindsAndThen
+ :: (HsBindGroup TcId -> thing -> thing) -- Combinator
+ -> [HsBindGroup Name]
+ -> TcM thing
+ -> TcM thing
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv binder_names poly_ids $
+tcBindsAndThen = tc_binds_and_then NotTopLevel
- -- Build bindings and IdInfos corresponding to user pragmas
- tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+tc_binds_and_then top_lvl combiner [] do_next
+ = do_next
+tc_binds_and_then top_lvl combiner (group : groups) do_next
+ = tc_bind_and_then top_lvl combiner group $
+ tc_binds_and_then top_lvl combiner groups do_next
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie) ->
+tc_bind_and_then top_lvl combiner (HsIPBinds binds) do_next
+ = getLIE do_next `thenM` \ (result, expr_lie) ->
+ mapAndUnzipM (wrapLocSndM tc_ip_bind) binds `thenM` \ (avail_ips, binds') ->
- -- Create specialisations of functions bound here
- bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
- poly_ids `thenTc` \ (lie2, inst_mbinds) ->
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds ->
- -- All done
- let
- final_lie = lie2 `plusLIE` poly_lie
- final_binds = MonoBind poly_binds [] is_rec `ThenBinds`
- MonoBind inst_mbinds [] nonRecursive `ThenBinds`
- prag_binds
- in
- returnTc (prag_info_fn, (combiner final_binds thing, final_lie))
- ) `thenTc` \ (_, result) ->
- returnTc result
+ returnM (combiner (HsIPBinds binds') $
+ combiner (HsBindGroup dict_binds [] Recursive) result)
where
- binder_names = map fst (bagToList (collectMonoBinders bind))
- ty_sigs = [sig | sig@(Sig name _ _) <- sigs]
-
-\end{code}
-
-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]
-
-\begin{pseudocode}
-tcBindsAndThen
- :: RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty))
- -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
-
-tcBindsAndThen EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (IPBind ip expr)
+ = newTyVarTy openTypeKind `thenM` \ ty ->
+ newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
+ tcCheckRho expr ty `thenM` \ expr' ->
+ returnM (ip_inst, (IPBind ip' expr'))
+
+tc_bind_and_then top_lvl combiner (HsBindGroup binds sigs is_rec) do_next
+ | isEmptyBag binds
+ = do_next
+ | otherwise
+ = -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
+ -- Notice that they scope over
+ -- a) the type signatures in the binding group
+ -- b) the bindings in the group
+ -- c) the scope of the binding group (the "in" part)
+ tcAddScopedTyVars (collectSigTysFromHsBinds (bagToList binds)) $
+ tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+
+ case top_lvl of
+ TopLevel -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ --
+ -- Subtle (and ugly) point: furthermore at top level we
+ -- return the TcLclEnv, which contains the LIE var; we
+ -- don't want to return the wrong one!
+ -> tc_body poly_ids `thenM` \ (prag_binds, thing) ->
+ returnM (combiner (HsBindGroup
+ (poly_binds `unionBags` prag_binds)
+ [] -- no sigs
+ Recursive)
+ thing)
+
+ NotTopLevel -- For nested bindings we must do the
+ -- bindInstsOfLocalFuns thing. We must include
+ -- the LIE from the RHSs too -- polymorphic recursion!
+ -> getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) ->
+
+ -- Create specialisations of functions bound here
+ bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
+
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ if isRec is_rec then
+ returnM (
+ combiner (HsBindGroup
+ (poly_binds `unionBags`
+ lie_binds `unionBags`
+ prag_binds)
+ [] Recursive) thing
+ )
+ else
+ returnM (
+ combiner (HsBindGroup poly_binds [] NonRecursive) $
+ combiner (HsBindGroup prag_binds [] NonRecursive) $
+ combiner (HsBindGroup lie_binds [] Recursive) $
+ -- NB: the binds returned by tcSimplify and
+ -- bindInstsOfLocalFuns aren't guaranteed in
+ -- dependency order (though we could change
+ -- that); hence the Recursive marker.
+ thing)
-tcBindsAndThen (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
+{-
+ = -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
+ -- Notice that they scope over
+ -- a) the type signatures in the binding group
+ -- b) the bindings in the group
+ -- c) the scope of the binding group (the "in" part)
+ tcAddScopedTyVars (collectSigTysFromHsBinds (bagToList binds)) $
+
+ tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+
+ case top_lvl of
+ TopLevel -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ --
+ -- Subtle (and ugly) point: furthermore at top level we
+ -- return the TcLclEnv, which contains the LIE var; we
+ -- don't want to return the wrong one!
+ -> tc_body poly_ids `thenM` \ (prag_binds, thing) ->
+ returnM (combiner (HsBindGroup
+ (poly_binds `unionBags` prag_binds)
+ [] -- no sigs
+ Recursive)
+ thing)
+
+ NotTopLevel -- For nested bindings we must do teh bindInstsOfLocalFuns thing
+ -> getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) ->
+
+ -- Create specialisations of functions bound here
+ bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
+
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ if isRec is_rec then
+ returnM (
+ combiner (HsBindGroup (
+ poly_binds `unionBags`
+ lie_binds `unionBags`
+ prag_binds)
+ [] Recursive) thing
+ )
+ else
+ returnM (
+ combiner (HsBindGroup poly_binds [] NonRecursive) $
+ combiner (HsBindGroup prag_binds [] NonRecursive) $
+ combiner (HsBindGroup lie_binds [] Recursive) $
+ -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
+ -- aren't guaranteed in dependency order (though we could change
+ -- that); hence the Recursive marker.
+ thing)
+-}
+ where
+ tc_body poly_ids -- Type check the pragmas and "thing inside"
+ = -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv poly_ids $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcSpecSigs sigs `thenM` \ prag_binds ->
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenM` \ thing ->
-tcBindsAndThen (MonoBind bind sigs is_rec) do_next
- = tcBindAndThen bind sigs do_next
-\end{pseudocode}
+ returnM (prag_binds, thing)
+\end{code}
%************************************************************************
as the Name in the tc_ty_sig
\begin{code}
-tcBindWithSigs
- :: [Name]
- -> RenamedMonoBinds
- -> [TcSigInfo s]
- -> RecFlag
- -> (Name -> PragmaInfo)
- -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s])
-
-tcBindWithSigs binder_names mbind tc_ty_sigs is_rec prag_info_fn
- = recoverTc (
+tcBindWithSigs :: TopLevelFlag
+ -> LHsBinds Name
+ -> [LSig Name]
+ -> RecFlag
+ -> TcM (LHsBinds TcId, [TcId])
+
+tcBindWithSigs top_lvl mbind sigs is_rec
+ = -- TYPECHECK THE SIGNATURES
+ recoverM (returnM []) (
+ mappM tcTySig [sig | sig@(L _(Sig name _)) <- sigs]
+ ) `thenM` \ tc_ty_sigs ->
+
+ -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+ recoverM (
-- If typechecking the binds fails, then return with each
-- signature-less binder given type (forall a.a), to minimise subsequent
-- error messages
- newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
+ newTyVar liftedTypeKind `thenM` \ alpha_tv ->
let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- poly_ids = map mk_dummy binder_names
+ forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
+ binder_names = collectHsBindBinders mbind
+ poly_ids = map mk_dummy binder_names
mk_dummy name = case maybeSig tc_ty_sigs name of
- Just (TySigInfo _ poly_id _ _ _ _) -> poly_id -- Signature
- Nothing -> mkUserId name forall_a_a NoPragmaInfo -- No signature
+ Just sig -> sig_poly_id sig -- Signature
+ Nothing -> mkLocalId name forall_a_a -- No signature
in
- returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
- ) $
+ traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) `thenM_`
+ returnM (emptyBag, poly_ids)
+ ) $
- -- Create a new identifier for each binder, with each being given
- -- a fresh unique, and a type-variable type.
- tcGetUniques no_of_binders `thenNF_Tc` \ uniqs ->
- mapNF_Tc mk_mono_id_ty binder_names `thenNF_Tc` \ mono_id_tys ->
+ -- TYPECHECK THE BINDINGS
+ traceTc (ptext SLIT("--------------------------------------------------------")) `thenM_`
+ traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind)) `thenM_`
+ getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', bndr_names_w_ids), lie_req) ->
let
- mono_id_tyvars = tyVarsOfTypes mono_id_tys
- mono_ids = zipWith3Equal "tcBindAndSigs" mk_id binder_names uniqs mono_id_tys
- mk_id name uniq ty = mkUserLocal (getOccName name) uniq ty (getSrcLoc name)
+ (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids)
+ tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
in
- -- TYPECHECK THE BINDINGS
- tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) ->
+ -- GENERALISE
+ -- (it seems a bit crude to have to do getLIE twice,
+ -- but I can't see a better way just now)
+ addSrcSpan (srcLocSpan (minimum (map getSrcLoc binder_names))) $
+ -- TODO: location wrong
+
+ addErrCtxt (genCtxt binder_names) $
+ getLIE (generalise binder_names mbind tau_tvs lie_req tc_ty_sigs)
+ `thenM` \ ((tc_tyvars_to_gen, dict_binds, dict_ids), lie_free) ->
+
+
+ -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars
+ -- This commits any unbound kind variables to boxed kind, by unification
+ -- It's important that the final quanfified type variables
+ -- are fully zonked, *including boxity*, because they'll be
+ -- included in the forall types of the polymorphic Ids.
+ -- At calls of these Ids we'll instantiate fresh type variables from
+ -- them, and we use their boxity then.
+ mappM zonkTcTyVarToTyVar tc_tyvars_to_gen `thenM` \ real_tyvars_to_gen ->
+
+ -- ZONK THE Ids
+ -- It's important that the dict Ids are zonked, including the boxity set
+ -- in the previous step, because they are later used to form the type of
+ -- the polymorphic thing, and forall-types must be zonked so far as
+ -- their bound variables are concerned
+ mappM zonkId dict_ids `thenM` \ zonked_dict_ids ->
+ mappM zonkId mono_ids `thenM` \ zonked_mono_ids ->
+
+ -- BUILD THE POLYMORPHIC RESULT IDs
+ let
+ exports = zipWith mk_export binder_names zonked_mono_ids
+ poly_ids = [poly_id | (_, poly_id, _) <- exports]
+ dict_tys = map idType zonked_dict_ids
+
+ inlines = mkNameSet [ name
+ | L _ (InlineSig True (L _ name) _) <- sigs]
+ -- Any INLINE sig (regardless of phase control)
+ -- makes the RHS look small
+
+ inline_phases = listToFM [ (name, phase)
+ | L _ (InlineSig _ (L _ name) phase) <- sigs,
+ not (isAlwaysActive phase)]
+ -- Set the IdInfo field to control the inline phase
+ -- AlwaysActive is the default, so don't bother with them
+
+ mk_export binder_name zonked_mono_id
+ = (tyvars,
+ attachInlinePhase inline_phases poly_id,
+ zonked_mono_id)
+ where
+ (tyvars, poly_id) =
+ case maybeSig tc_ty_sigs binder_name of
+ Just sig -> (sig_tvs sig, sig_poly_id sig)
+ Nothing -> (real_tyvars_to_gen, new_poly_id)
+
+ new_poly_id = mkLocalId binder_name poly_ty
+ poly_ty = mkForAllTys real_tyvars_to_gen
+ $ mkFunTys dict_tys
+ $ idType zonked_mono_id
+ -- It's important to build a fully-zonked poly_ty, because
+ -- we'll slurp out its free type variables when extending the
+ -- local environment (tcExtendLocalValEnv); if it's not zonked
+ -- it appears to have free tyvars that aren't actually free
+ -- at all.
+ in
+
+ traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
+ exports, map idType poly_ids)) `thenM_`
- -- CHECK THAT THE SIGNATURES MATCH
- -- (must do this before getTyVarsToGen)
- checkSigMatch tc_ty_sigs `thenTc` \ sig_theta ->
+ -- Check for an unlifted, non-overloaded group
+ -- In that case we must make extra checks
+ if any (isUnLiftedType . idType) zonked_mono_ids && null zonked_dict_ids
+ then -- Some bindings are unlifted
+ checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind `thenM_`
- -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen
- -- The tyvars_not_to_gen are free in the environment, and hence
- -- candidates for generalisation, but sometimes the monomorphism
- -- restriction means we can't generalise them nevertheless
- getTyVarsToGen is_unrestricted mono_id_tyvars lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
-
- -- DEAL WITH TYPE VARIABLE KINDS
- mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ tyvars_to_gen_list ->
- -- It's important that the final list (tyvars_to_gen_list) is fully
- -- zonked, *including boxity*, because they'll be included in the forall types of
- -- the polymorphic Ids, and instances of these Ids will be generated from them.
- --
- -- This step can do unification => keep other zonking after this
-
- -- SIMPLIFY THE LIE
- tcExtendGlobalTyVars tyvars_not_to_gen (
- if null tc_ty_sigs then
- -- No signatures, so just simplify the lie
- tcSimplify tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) ->
- returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
-
- else
- zonk_theta sig_theta `thenNF_Tc` \ sig_theta' ->
- newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) ->
- -- It's important that sig_theta is zonked, because
- -- dict_id is later used to form the type of the polymorphic thing,
- -- and forall-types must be zonked so far as their bound variables
- -- are concerned
-
- -- Check that the needed dicts can be expressed in
- -- terms of the signature ones
- tcAddErrCtxt (sigsCtxt tysig_names) $
- tcSimplifyAndCheck tyvars_to_gen dicts_sig lie `thenTc` \ (lie_free, dict_binds) ->
- returnTc (lie_free, dict_binds, dict_ids)
-
- ) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
-
- ASSERT( not (any (isUnboxedTypeKind . tyVarKind) tyvars_to_gen_list) )
+ extendLIEs lie_req `thenM_`
+ returnM (
+ unitBag $ noLoc $
+ AbsBinds [] [] exports inlines mbind',
+ -- Do not generate even any x=y bindings
+ poly_ids
+ )
+
+ else -- The normal case
+ extendLIEs lie_free `thenM_`
+ returnM (
+ unitBag $ noLoc $
+ AbsBinds real_tyvars_to_gen
+ zonked_dict_ids
+ exports
+ inlines
+ (dict_binds `unionBags` mbind'),
+ poly_ids
+ )
+
+attachInlinePhase inline_phases bndr
+ = case lookupFM inline_phases (idName bndr) of
+ Just prag -> bndr `setInlinePragma` prag
+ Nothing -> bndr
+
+-- Check that non-overloaded unlifted bindings are
+-- a) non-recursive,
+-- b) not top level,
+-- c) non-polymorphic
+-- d) not a multiple-binding group (more or less implied by (a))
+
+checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind
+ = ASSERT( not (any ((eqKind unliftedTypeKind) . tyVarKind) real_tyvars_to_gen) )
-- The instCantBeGeneralised stuff in tcSimplify should have
- -- already raised an error if we're trying to generalise an unboxed tyvar
- -- (NB: unboxed tyvars are always introduced along with a class constraint)
- -- and it's better done there because we have more precise origin information.
+ -- already raised an error if we're trying to generalise an
+ -- unboxed tyvar (NB: unboxed tyvars are always introduced
+ -- along with a class constraint) and it's better done there
+ -- because we have more precise origin information.
-- That's why we just use an ASSERT here.
- -- BUILD THE POLYMORPHIC RESULT IDs
- mapNF_Tc zonkTcType mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
- let
- exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types
- dict_tys = map tcIdType dicts_bound
+ checkTc (isNotTopLevel top_lvl)
+ (unliftedBindErr "Top-level" mbind) `thenM_`
+ checkTc (isNonRec is_rec)
+ (unliftedBindErr "Recursive" mbind) `thenM_`
+ checkTc (isSingletonBag mbind)
+ (unliftedBindErr "Multiple" mbind) `thenM_`
+ checkTc (null real_tyvars_to_gen)
+ (unliftedBindErr "Polymorphic" mbind)
+\end{code}
- mk_export binder_name mono_id zonked_mono_id_ty
- | maybeToBool maybe_sig = (sig_tyvars, TcId sig_poly_id, TcId mono_id)
- | otherwise = (tyvars_to_gen_list, TcId poly_id, TcId mono_id)
- where
- maybe_sig = maybeSig tc_ty_sigs binder_name
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _) = maybe_sig
- poly_id = mkUserId binder_name poly_ty (prag_info_fn binder_name)
- poly_ty = mkForAllTys tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty
- -- It's important to build a fully-zonked poly_ty, because
- -- we'll slurp out its free type variables when extending the
- -- local environment (tcExtendLocalValEnv); if it's not zonked
- -- it appears to have free tyvars that aren't actually free at all.
- in
- -- BUILD RESULTS
- returnTc (
- AbsBinds tyvars_to_gen_list
- dicts_bound
- exports
- (dict_binds `AndMonoBinds` mbind'),
- lie_free,
- [poly_id | (_, TcId poly_id, _) <- exports]
- )
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
+
+ * Bind any variable for which we have a type signature
+ to an Id with a polymorphic type. Then when type-checking
+ the RHSs we'll make a full polymorphic call.
+
+This fine, but if you aren't a bit careful you end up with a horrendous
+amount of partial application and (worse) a huge space leak. For example:
+
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
+
+If we don't take care, after typechecking we get
+
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
+
+Notice the the stupid construction of (f a d), which is of course
+identical to the function we're executing. In this case, the
+polymorphic recursion isn't being used (but that's a very common case).
+We'd prefer
+
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
+
+This can lead to a massive space leak, from the following top-level defn
+(post-typechecking)
+
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
+
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
+
+ ff = f Int dEqInt
+
+ = let f' = f Int dEqInt in \ys. ...f'...
+
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
+
+Etc.
+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.
+
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
+
+\begin{code}
+generalise binder_names mbind tau_tvs lie_req sigs =
+
+ -- check for -fno-monomorphism-restriction
+ doptM Opt_NoMonomorphismRestriction `thenM` \ no_MR ->
+ let is_unrestricted | no_MR = True
+ | otherwise = isUnRestrictedGroup tysig_names mbind
+ in
+
+ if not is_unrestricted then -- RESTRICTED CASE
+ -- Check signature contexts are empty
+ checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr binder_names) `thenM_`
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ tcSimplifyRestricted doc tau_tvs lie_req `thenM` \ (qtvs, binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars qtvs sigs `thenM` \ final_qtvs ->
+
+ returnM (final_qtvs, binds, [])
+
+ else if null sigs then -- UNRESTRICTED CASE, NO TYPE SIGS
+ tcSimplifyInfer doc tau_tvs lie_req
+
+ else -- UNRESTRICTED CASE, WITH TYPE SIGS
+ -- CHECKING CASE: Unrestricted group, there are type signatures
+ -- Check signature contexts are identical
+ checkSigsCtxts sigs `thenM` \ (sig_avails, sig_dicts) ->
+
+ -- Check that the needed dicts can be
+ -- expressed in terms of the signature ones
+ tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenM` \ (forall_tvs, dict_binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars forall_tvs sigs `thenM` \ final_qtvs ->
+
+ returnM (final_qtvs, dict_binds, sig_dicts)
+
where
- no_of_binders = length binder_names
+ tysig_names = map (idName . sig_poly_id) sigs
+ is_mono_sig sig = null (sig_theta sig)
- mk_mono_id_ty binder_name = case maybeSig tc_ty_sigs binder_name of
- Just (TySigInfo name _ _ _ tau_ty _) -> returnNF_Tc tau_ty -- There's a signature
- otherwise -> newTyVarTy kind -- No signature
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names
- tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
- is_unrestricted = isUnRestrictedGroup tysig_names mbind
+-----------------------
+ -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE
+ -- The type signatures on a mutually-recursive group of definitions
+ -- must all have the same context (or none).
+ --
+ -- We unify them because, with polymorphic recursion, their types
+ -- might not otherwise be related. This is a rather subtle issue.
+ -- ToDo: amplify
+checkSigsCtxts sigs@(TySigInfo { sig_poly_id = id1, sig_tvs = sig_tvs, sig_theta = theta1, sig_loc = span}
+ : other_sigs)
+ = addSrcSpan span $
+ mappM_ check_one other_sigs `thenM_`
+ if null theta1 then
+ returnM ([], []) -- Non-overloaded type signatures
+ else
+ newDicts SignatureOrigin theta1 `thenM` \ sig_dicts ->
+ let
+ -- The "sig_avails" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the lie_avail
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ sig_avails = sig_dicts ++ sig_meths
+ in
+ returnM (sig_avails, map instToId sig_dicts)
+ where
+ sig1_dict_tys = map mkPredTy theta1
+ sig_meths = concatMap sig_insts sigs
- kind | is_rec = mkBoxedTypeKind -- Recursive, so no unboxed types
- | otherwise = mkTypeKind -- Non-recursive, so we permit unboxed types
+ check_one (TySigInfo {sig_poly_id = id, sig_theta = theta})
+ = addErrCtxt (sigContextsCtxt id1 id) $
+ checkTc (equalLength theta theta1) sigContextsErr `thenM_`
+ unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
-zonk_theta theta = mapNF_Tc zonk theta
- where
- zonk (c,t) = zonkTcType t `thenNF_Tc` \ t' ->
- returnNF_Tc (c,t')
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs
+ = mappM check_one sigs `thenM` \ sig_tvs_s ->
+ let
+ -- Sigh. Make sure that all the tyvars in the type sigs
+ -- appear in the returned ty var list, which is what we are
+ -- going to generalise over. Reason: we occasionally get
+ -- silly types like
+ -- type T a = () -> ()
+ -- f :: T a
+ -- f () = ()
+ -- Here, 'a' won't appear in qtvs, so we have to add it
+
+ sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
+ all_tvs = extendVarSetList sig_tvs qtvs
+ in
+ returnM (varSetElems all_tvs)
+ where
+ check_one (TySigInfo {sig_poly_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) $
+ checkSigTyVarsWrt (idFreeTyVars id) tvs
\end{code}
-@getImplicitStuffToGen@ decides what type variables 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
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
find which tyvars are constrained.
\begin{code}
-getTyVarsToGen is_unrestricted mono_tyvars lie
- = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
- zonkTcTyVars mono_tyvars `thenNF_Tc` \ mentioned_tyvars ->
- let
- tyvars_to_gen = mentioned_tyvars `minusTyVarSet` free_tyvars
- in
- if is_unrestricted
- then
- returnTc (emptyTyVarSet, tyvars_to_gen)
- else
- tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
- let
- -- ASSERT: dicts_sig is already zonked!
- constrained_tyvars = foldrBag (unionTyVarSets . tyVarsOfInst) emptyTyVarSet constrained_dicts
- reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars
- in
- returnTc (constrained_tyvars, reduced_tyvars_to_gen)
-\end{code}
-
-
-\begin{code}
isUnRestrictedGroup :: [Name] -- Signatures given for these
- -> RenamedMonoBinds
+ -> LHsBinds Name
-> Bool
+isUnRestrictedGroup sigs binds = all (unrestricted . unLoc) (bagToList binds)
+ where
+ unrestricted (PatBind other _) = False
+ unrestricted (VarBind v _) = v `is_elem` sigs
+ unrestricted (FunBind v _ matches) = unrestricted_match matches
+ || unLoc v `is_elem` sigs
+
+ unrestricted_match (L _ (Match [] _ _) : _) = False
+ -- No args => like a pattern binding
+ unrestricted_match other = True
+ -- Some args => a function binding
is_elem v vs = isIn "isUnResMono" v vs
-
-isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (PatMonoBind other _ _) = False
-isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True
-isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 &&
- isUnRestrictedGroup sigs mb2
-isUnRestrictedGroup sigs EmptyMonoBinds = True
-\end{code}
-
-@defaultUncommittedTyVar@ checks for generalisation over unboxed
-types, and defaults any TypeKind TyVars to BoxedTypeKind.
-
-\begin{code}
-defaultUncommittedTyVar tyvar
- | isTypeKind (tyVarKind tyvar)
- = newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ boxed_tyvar ->
- unifyTauTy (mkTyVarTy boxed_tyvar) (mkTyVarTy tyvar) `thenTc_`
- returnTc boxed_tyvar
-
- | otherwise
- = returnTc tyvar
\end{code}
The signatures have been dealt with already.
\begin{code}
-tcMonoBinds :: RenamedMonoBinds
- -> [Name] -> [TcIdBndr s]
- -> [TcSigInfo s]
- -> TcM s (TcMonoBinds s, LIE s)
-
-tcMonoBinds mbind binder_names mono_ids tc_ty_sigs
- = tcExtendLocalValEnv binder_names mono_ids (
- tc_mono_binds mbind
- )
- where
- sig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
- sig_ids = [id | (TySigInfo _ id _ _ _ _) <- tc_ty_sigs]
-
- tc_mono_binds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
-
- tc_mono_binds (AndMonoBinds mb1 mb2)
- = tc_mono_binds mb1 `thenTc` \ (mb1a, lie1) ->
- tc_mono_binds mb2 `thenTc` \ (mb2a, lie2) ->
- returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
-
- tc_mono_binds (FunMonoBind name inf matches locn)
- = tcAddSrcLoc locn $
- tcLookupLocalValueOK "tc_mono_binds" name `thenNF_Tc` \ id ->
-
- -- Before checking the RHS, extend the envt with
- -- bindings for the *polymorphic* Ids from any type signatures
- tcExtendLocalValEnv sig_names sig_ids $
- tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
-
- returnTc (FunMonoBind (TcId id) inf matches' locn, lie)
-
- tc_mono_binds bind@(PatMonoBind pat grhss_and_binds locn)
- = tcAddSrcLoc locn $
- tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
- tcExtendLocalValEnv sig_names sig_ids $
- tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds2, lie, grhss_ty) ->
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- unifyTauTy pat_ty grhss_ty `thenTc_`
- returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
- plusLIE lie_pat lie)
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Signatures}
-%* *
-%************************************************************************
-
-@tcSigs@ checks the signatures for validity, and returns a list of
-{\em freshly-instantiated} signatures. That is, the types are already
-split up, and have fresh type variables installed. All non-type-signature
-"RenamedSigs" are ignored.
-
-The @TcSigInfo@ contains @TcTypes@ because they are unified with
-the variable's type, and after that checked to see whether they've
-been instantiated.
-
-\begin{code}
-data TcSigInfo s
- = TySigInfo Name
- (TcIdBndr s) -- *Polymorphic* binder for this value...
- [TcTyVar s] (TcThetaType s) (TcTauType s)
- SrcLoc
-
-
-maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s)
- -- Search for a particular signature
-maybeSig [] name = Nothing
-maybeSig (sig@(TySigInfo sig_name _ _ _ _ _) : sigs) name
- | name == sig_name = Just sig
- | otherwise = maybeSig sigs name
-\end{code}
-
-
-\begin{code}
-tcTySig :: (Name -> PragmaInfo)
- -> RenamedSig
- -> TcM s (TcSigInfo s)
-
-tcTySig prag_info_fn (Sig v ty src_loc)
- = tcAddSrcLoc src_loc $
- tcHsType ty `thenTc` \ sigma_ty ->
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' ->
- let
- poly_id = mkUserId v sigma_ty' (prag_info_fn v)
- (tyvars', theta', tau') = splitSigmaTy sigma_ty'
- -- This splitSigmaTy tries hard to make sure that tau' is a type synonym
- -- wherever possible, which can improve interface files.
- in
- returnTc (TySigInfo v poly_id tyvars' theta' tau' src_loc)
-\end{code}
-
-@checkSigMatch@ does the next step in checking signature matching.
-The tau-type part has already been unified. What we do here is to
-check that this unification has not over-constrained the (polymorphic)
-type variables of the original signature type.
-
-The error message here is somewhat unsatisfactory, but it'll do for
-now (ToDo).
-
-\begin{code}
-checkSigMatch []
- = returnTc (error "checkSigMatch")
-
-checkSigMatch tc_ty_sigs@( sig1@(TySigInfo _ id1 _ theta1 _ _) : all_sigs_but_first )
- = -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK
- -- Doesn't affect substitution
- mapTc check_one_sig tc_ty_sigs `thenTc_`
-
- -- CHECK THAT ALL THE SIGNATURE CONTEXTS ARE UNIFIABLE
- -- The type signatures on a mutually-recursive group of definitions
- -- must all have the same context (or none).
- --
- -- We unify them because, with polymorphic recursion, their types
- -- might not otherwise be related. This is a rather subtle issue.
- -- ToDo: amplify
- mapTc check_one_cxt all_sigs_but_first `thenTc_`
-
- returnTc theta1
- where
- sig1_dict_tys = mk_dict_tys theta1
- n_sig1_dict_tys = length sig1_dict_tys
-
- check_one_cxt sig@(TySigInfo _ id _ theta _ src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (sigContextsCtxt id1 id) $
- checkTc (length this_sig_dict_tys == n_sig1_dict_tys)
- sigContextsErr `thenTc_`
- unifyTauTyLists sig1_dict_tys this_sig_dict_tys
- where
- this_sig_dict_tys = mk_dict_tys theta
-
- check_one_sig (TySigInfo name id sig_tyvars _ sig_tau src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (sigCtxt id) $
- checkSigTyVars sig_tyvars sig_tau
-
- mk_dict_tys theta = [mkDictTy c t | (c,t) <- theta]
-\end{code}
-
-
-@checkSigTyVars@ is used after the type in a type signature has been unified with
-the actual type found. It then checks that the type variables of the type signature
-are
- (a) still all type variables
- eg matching signature [a] against inferred type [(p,q)]
- [then a will be unified to a non-type variable]
-
- (b) still all distinct
- eg matching signature [(a,b)] against inferred type [(p,p)]
- [then a and b will be unified together]
-
-BUT ACTUALLY THESE FIRST TWO ARE FORCED BY USING DontBind TYVARS
-
- (c) not mentioned in the environment
- eg the signature for f in this:
-
- g x = ... where
- f :: a->[a]
- f y = [x,y]
-
- Here, f is forced to be monorphic by the free occurence of x.
-
-Before doing this, the substitution is applied to the signature type variable.
-
-\begin{code}
-checkSigTyVars :: [TcTyVar s] -- The original signature type variables
- -> TcType s -- signature type (for err msg)
- -> TcM s ()
-
-checkSigTyVars sig_tyvars sig_tau
- = tcGetGlobalTyVars `thenNF_Tc` \ globals ->
+tcMonoBinds :: LHsBinds Name
+ -> [TcSigInfo] -> RecFlag
+ -> TcM (LHsBinds TcId,
+ Bag (Name, -- Bound names
+ TcId)) -- Corresponding monomorphic bound things
+
+tcMonoBinds mbinds tc_ty_sigs is_rec
+ -- Three stages:
+ -- 1. Check the patterns, building up an environment binding
+ -- the variables in this group (in the recursive case)
+ -- 2. Extend the environment
+ -- 3. Check the RHSs
+ = mapBagM tc_lbind_pats mbinds `thenM` \ bag_of_pairs ->
let
- mono_tyvars = filter (`elementOfTyVarSet` globals) sig_tyvars
+ (complete_it, xve)
+ = foldrBag combine
+ (returnM (emptyBag, emptyBag), emptyBag)
+ bag_of_pairs
+ combine (complete_it1, xve1) (complete_it2, xve2)
+ = (complete_it, xve1 `unionBags` xve2)
+ where
+ complete_it = complete_it1 `thenM` \ (b1, bs1) ->
+ complete_it2 `thenM` \ (b2, bs2) ->
+ returnM (b1 `consBag` b2, bs1 `unionBags` bs2)
in
- -- TEMPORARY FIX
- -- Until the final Bind-handling stuff is in, several type signatures in the same
- -- bindings group can cause the signature type variable from the different
- -- signatures to be unified. So we still need to zonk and check point (b).
- -- Remove when activating the new binding code
- mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys ->
- checkTcM (hasNoDups (map (getTyVar "checkSigTyVars") sig_tys))
- (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' ->
- failTc (badMatchErr sig_tau sig_tau')
- ) `thenTc_`
-
-
- -- Check point (c)
- -- We want to report errors in terms of the original signature tyvars,
- -- ie sig_tyvars, NOT sig_tyvars'. sig_tys and sig_tyvars' correspond
- -- 1-1 with sig_tyvars, so we can just map back.
- checkTc (null mono_tyvars)
- (notAsPolyAsSigErr sig_tau mono_tyvars)
+ tcExtendLocalValEnv2 (bagToList xve) complete_it
+ where
+ tc_lbind_pats :: LHsBind Name
+ -> TcM (TcM (LHsBind TcId, Bag (Name,TcId)), -- Completer
+ Bag (Name,TcId))
+ -- wrapper for tc_bind_pats to deal with the location stuff
+ tc_lbind_pats (L loc bind)
+ = addSrcSpan loc $ do
+ (tc, bag) <- tc_bind_pats bind
+ return (wrap tc, bag)
+ where
+ wrap tc = addSrcSpan loc $ do
+ (bind, stuff) <- tc
+ return (L loc bind, stuff)
+
+
+ tc_bind_pats :: HsBind Name
+ -> TcM (TcM (HsBind TcId, Bag (Name,TcId)), -- Completer
+ Bag (Name,TcId))
+ tc_bind_pats (FunBind (L nm_loc name) inf matches)
+ -- Three cases:
+ -- a) Type sig supplied
+ -- b) No type sig and recursive
+ -- c) No type sig and non-recursive
+
+ | Just sig <- maybeSig tc_ty_sigs name
+ = let -- (a) There is a type signature
+ -- Use it for the environment extension, and check
+ -- the RHS has the appropriate type (with outer for-alls stripped off)
+ mono_id = sig_mono_id sig
+ mono_ty = idType mono_id
+ complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
+ returnM (FunBind (L nm_loc mono_id) inf matches',
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, if isRec is_rec then unitBag (name, sig_poly_id sig)
+ else emptyBag)
+
+ | isRec is_rec
+ = -- (b) No type signature, and recursive
+ -- So we must use an ordinary H-M type variable
+ -- which means the variable gets an inferred tau-type
+ newLocalName name `thenM` \ mono_name ->
+ newTyVarTy openTypeKind `thenM` \ mono_ty ->
+ let
+ mono_id = mkLocalId mono_name mono_ty
+ complete_it = tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
+ returnM (FunBind (L nm_loc mono_id) inf matches',
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, unitBag (name, mono_id))
+
+ | otherwise -- (c) No type signature, and non-recursive
+ = let -- So we can use a 'hole' type to infer a higher-rank type
+ complete_it
+ = newHole `thenM` \ hole ->
+ tcMatchesFun name matches (Infer hole) `thenM` \ matches' ->
+ readMutVar hole `thenM` \ fun_ty ->
+ newLocalName name `thenM` \ mono_name ->
+ let
+ mono_id = mkLocalId mono_name fun_ty
+ in
+ returnM (FunBind (L nm_loc mono_id) inf matches',
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, emptyBag)
+
+ tc_bind_pats bind@(PatBind pat grhss)
+ = -- Now typecheck the pattern
+ -- We do now support binding fresh (not-already-in-scope) scoped
+ -- type variables in the pattern of a pattern binding.
+ -- For example, this is now legal:
+ -- (x::a, y::b) = e
+ -- The type variables are brought into scope in tc_binds_and_then,
+ -- so we don't have to do anything here.
+ newHole `thenM` \ hole ->
+ tcPat tc_pat_bndr pat (Infer hole) `thenM` \ (pat', tvs, ids, lie_avail) ->
+ readMutVar hole `thenM` \ pat_ty ->
+
+ -- Don't know how to deal with pattern-bound existentials yet
+ checkTc (isEmptyBag tvs && null lie_avail)
+ (existentialExplode bind) `thenM_`
+
+ let
+ complete_it = addErrCtxt (patMonoBindsCtxt bind) $
+ tcGRHSsPat grhss (Check pat_ty) `thenM` \ grhss' ->
+ returnM (PatBind pat' grhss', ids)
+ in
+ returnM (complete_it, if isRec is_rec then ids else emptyBag)
+
+ -- tc_pat_bndr is used when dealing with a LHS binder in a pattern.
+ -- If there was a type sig for that Id, we want to make it much
+ -- as if that type signature had been on the binder as a SigPatIn.
+ -- We check for a type signature; if there is one, we use the mono_id
+ -- from the signature. This is how we make sure the tau part of the
+ -- signature actually matches the type of the LHS; then tc_bind_pats
+ -- ensures the LHS and RHS have the same type
+
+ tc_pat_bndr name pat_ty
+ = case maybeSig tc_ty_sigs name of
+ Nothing -> newLocalName name `thenM` \ bndr_name ->
+ tcMonoPatBndr bndr_name pat_ty
+
+ Just sig -> addSrcSpan (srcLocSpan (getSrcLoc name)) $
+ -- TODO: location wrong
+ tcSubPat (idType mono_id) pat_ty `thenM` \ co_fn ->
+ returnM (co_fn, mono_id)
+ where
+ mono_id = sig_mono_id sig
\end{code}
%* *
%************************************************************************
-
-@tcPragmaSigs@ munches up the "signatures" that arise through *user*
+@tcSpecSigs@ munches up the specialisation "signatures" that arise through *user*
pragmas. It is convenient for them to appear in the @[RenamedSig]@
part of a binding because then the same machinery can be used for
moving them into place as is done for type signatures.
-\begin{code}
-tcPragmaSigs :: [RenamedSig] -- The pragma signatures
- -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
- TcHsBinds s,
- LIE s)
-
--- For now we just deal with INLINE pragmas
-tcPragmaSigs sigs = returnTc (prag_fn, EmptyBinds, emptyLIE )
- where
- prag_fn name | any has_inline sigs = IWantToBeINLINEd
- | otherwise = NoPragmaInfo
- where
- has_inline (InlineSig n _) = (n == name)
- has_inline other = False
-
-
-{-
-tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
- let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
- in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
+They look like this:
-\begin{code}
-tcPragmaSig (DeforestSig name loc)
- = returnTc ((name, addDeforestInfo DoDeforest),EmptyBinds,emptyLIE)
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addUnfoldInfo (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addUnfoldInfo (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
-\end{code}
-
-The interesting case is for SPECIALISE pragmas. There are two forms.
-Here's the first form:
\begin{verbatim}
f :: Ord a => [a] -> b -> b
{-# SPECIALIZE f :: [Int] -> b -> b #-}
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.
+We used to have a form
+ {-# SPECIALISE f :: <type> = g #-}
+which promised that g implemented f at <type>, but we do that with
+a RULE now:
+ {-# SPECIALISE (f::<type) = g #-}
\begin{code}
-tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
+tcSpecSigs :: [LSig Name] -> TcM (LHsBinds TcId)
+tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs)
+ = -- SPECIALISE f :: forall b. theta => tau = g
+ addSrcSpan loc $
+ addErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
- tcHsType poly_ty `thenTc` \ sig_sigma ->
- tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
- let
- (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
- origin = ValSpecOrigin name
- in
+ tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty ->
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (null sig_theta)
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
+ -- Check that f has a more general type, and build a RHS for
+ -- the spec-pragma-id at the same time
+ getLIE (tcCheckSigma (L nm_loc (HsVar name)) sig_ty) `thenM` \ (spec_expr, spec_lie) ->
- -- Get and instantiate the type of the id mentioned
- tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
- tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty ->
+ -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
+ tcSimplifyToDicts spec_lie `thenM` \ spec_binds ->
+
+ -- Just specialise "f" by building a SpecPragmaId binding
+ -- It is the thing that makes sure we don't prematurely
+ -- dead-code-eliminate the binding we are really interested in.
+ newLocalName name `thenM` \ spec_name ->
let
- (main_tyvars, main_rho) = splitForAllTy main_ty
- (main_theta,main_tau) = splitRhoTy main_rho
- main_arg_tys = mkTyVarTys main_tyvars
+ spec_bind = VarBind (mkSpecPragmaId spec_name sig_ty)
+ (mkHsLet spec_binds spec_expr)
in
- -- Check that the specialised type is indeed an instance of
- -- the type of the main function.
- unifyTauTy sig_tau main_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Check that the type variables of the polymorphic function are
- -- either left polymorphic, or instantiate to ground type.
- -- Also check that the overloaded type variables are instantiated to
- -- ground type; or equivalently that all dictionaries have ground type
- 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) ->
+ -- Do the rest and combine
+ tcSpecSigs sigs `thenM` \ binds_rest ->
+ returnM (binds_rest `snocBag` L loc spec_bind)
- -- Check that it has the correct type, and doesn't constrain the
- -- signature variables at all
- unifyTauTy sig_tau spec_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
-
- let
- spec_rhs = mkHsTyLam sig_tyvars spec_body
- spec_binds = VarMonoBind local_spec_id spec_rhs
- `AndMonoBinds`
- VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
- spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
- in
- returnTc ((name, addSpecInfo spec_info), spec_binds, spec_lie)
--}
+tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
+tcSpecSigs [] = returnM emptyBag
\end{code}
-
%************************************************************************
%* *
\subsection[TcBinds-errors]{Error contexts and messages}
\begin{code}
-patMonoBindsCtxt bind sty
- = hang (ptext SLIT("In a pattern binding:")) 4 (ppr sty bind)
+patMonoBindsCtxt bind
+ = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
-----------------------------------------------
-valSpecSigCtxt v ty sty
- = hang (ptext SLIT("In a SPECIALIZE pragma for a value:"))
- 4 (sep [(<>) (ppr sty v) (ptext SLIT(" ::")),
- ppr sty ty])
-
-
+valSpecSigCtxt v ty
+ = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
+ nest 4 (ppr v <+> dcolon <+> ppr ty)]
-----------------------------------------------
-notAsPolyAsSigErr sig_tau mono_tyvars sty
- = hang (ptext SLIT("A type signature is more polymorphic than the inferred type"))
- 4 (vcat [text "Some type variables in the inferred type can't be forall'd, namely:",
- interpp'SP sty mono_tyvars,
- ptext SLIT("Possible cause: the RHS mentions something subject to the monomorphism restriction")
- ])
+sigContextsErr = ptext SLIT("Mismatched contexts")
------------------------------------------------
-badMatchErr sig_ty inferred_ty sty
- = hang (ptext SLIT("Type signature doesn't match inferred type"))
- 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sty sig_ty),
- hang (ptext SLIT("Inferred :")) 4 (ppr sty inferred_ty)
- ])
+sigContextsCtxt s1 s2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
+ nest 2 (vcat [ppr s1 <+> dcolon <+> ppr (idType s1),
+ ppr s2 <+> dcolon <+> ppr (idType s2)]),
+ ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
-----------------------------------------------
-sigCtxt id sty
- = sep [ptext SLIT("When checking signature for"), ppr sty id]
-sigsCtxt ids sty
- = sep [ptext SLIT("When checking signature(s) for:"), interpp'SP sty ids]
+unliftedBindErr flavour mbind
+ = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:"))
+ 4 (ppr mbind)
-----------------------------------------------
-sigContextsErr sty
- = ptext SLIT("Mismatched contexts")
-sigContextsCtxt s1 s2 sty
- = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"),
- ppr sty s1, ptext SLIT("and"), ppr sty s2])
- 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)"))
+existentialExplode mbinds
+ = hang (vcat [text "My brain just exploded.",
+ text "I can't handle pattern bindings for existentially-quantified constructors.",
+ text "In the binding group"])
+ 4 (ppr mbinds)
-----------------------------------------------
-specGroundnessCtxt
- = panic "specGroundnessCtxt"
-
---------------------------------------------
-specContextGroundnessCtxt -- err_ctxt dicts sty
- = panic "specContextGroundnessCtxt"
-{-
- = hang (
- sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr sty name],
- hcat [ptext SLIT(" specialised to the type"), ppr sty spec_ty],
- pp_spec_id sty,
- ptext SLIT("... not all overloaded type variables were instantiated"),
- ptext SLIT("to ground types:")])
- 4 (vcat [hsep [ppr sty c, ppr sty t]
- | (c,t) <- map getDictClassAndType dicts])
- where
- (name, spec_ty, locn, pp_spec_id)
- = case err_ctxt of
- ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> empty)
- ValSpecSpecIdCtxt n ty spec loc ->
- (n, ty, loc,
- \ sty -> hsep [ptext SLIT("... type of explicit id"), ppr sty spec])
--}
+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")])
+
+genCtxt binder_names
+ = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
+
+-- Used in error messages
+-- Use quotes for a single one; they look a bit "busy" for several
+pprBinders [bndr] = quotes (ppr bndr)
+pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
-
-
-
-
projects / ghc-hetmet.git / blobdiff