\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBinds,
- tcSpecSigs, tcBindWithSigs ) where
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcHsBootSigs, tcMonoBinds, tcSpecSigs ) where
#include "HsVersions.h"
-import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun )
-import {-# SOURCE #-} TcExpr ( tcExpr )
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho )
-import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), StmtCtxt(..),
- Match(..), collectMonoBinders, andMonoBinds
+import CmdLineOpts ( DynFlag(Opt_MonomorphismRestriction) )
+import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, Sig(..),
+ LSig, Match(..), HsBindGroup(..), IPBind(..),
+ HsType(..), hsLTyVarNames, isVanillaLSig,
+ LPat, GRHSs, MatchGroup(..), emptyLHsBinds, isEmptyLHsBinds,
+ collectHsBindBinders, collectPatBinders, pprPatBind
)
-import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
-import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet )
-
-import TcMonad
-import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..),
- newDicts, tyVarsOfInst, instToId,
- getAllFunDepsOfLIE, getIPsOfLIE, zonkFunDeps
- )
-import TcEnv ( tcExtendLocalValEnv,
- newSpecPragmaId, newLocalId,
- tcLookupTyCon,
- tcGetGlobalTyVars, tcExtendGlobalTyVars
- )
-import TcSimplify ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts )
-import TcImprove ( tcImprove )
-import TcMonoType ( tcHsSigType, checkSigTyVars,
- TcSigInfo(..), tcTySig, maybeSig, sigCtxt
+import TcHsSyn ( TcId, TcDictBinds, zonkId, mkHsLet )
+
+import TcRnMonad
+import Inst ( InstOrigin(..), newDictsAtLoc, newIPDict, instToId )
+import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
+ newLocalName, tcLookupLocalIds, pprBinders,
+ tcGetGlobalTyVars )
+import TcUnify ( Expected(..), tcInfer, unifyTheta,
+ bleatEscapedTvs, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
+ tcSimplifyToDicts, tcSimplifyIPs )
+import TcHsType ( tcHsSigType, UserTypeCtxt(..), tcAddLetBoundTyVars,
+ TcSigInfo(..), TcSigFun, lookupSig
)
-import TcPat ( tcPat )
+import TcPat ( tcPat, PatCtxt(..) )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( TcThetaType, newTyVarTy, newTyVar,
- zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar
- )
-import TcUnify ( unifyTauTy, unifyTauTyLists )
-
-import CoreFVs ( idFreeTyVars )
-import Id ( mkVanillaId, setInlinePragma )
+import TcMType ( newTyFlexiVarTy, zonkQuantifiedTyVar,
+ tcInstSigType, zonkTcTypes, zonkTcTyVar )
+import TcType ( TcTyVar, SkolemInfo(SigSkol),
+ TcTauType, TcSigmaType,
+ mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
+ mkForAllTy, isUnLiftedType, tcGetTyVar,
+ mkTyVarTys, tidyOpenTyVar, tidyOpenType )
+import Kind ( argTypeKind )
+import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv, emptyTidyEnv )
+import TysPrim ( alphaTyVar )
+import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
import Var ( idType, idName )
-import IdInfo ( InlinePragInfo(..) )
-import Name ( Name, getOccName, getSrcLoc )
+import Name ( Name )
import NameSet
-import Type ( mkTyVarTy, tyVarsOfTypes, mkTyConApp,
- mkForAllTys, mkFunTys,
- mkPredTy, mkForAllTy, isUnLiftedType,
- isUnboxedType, unboxedTypeKind, boxedTypeKind, openTypeKind
- )
-import FunDeps ( oclose )
-import Var ( tyVarKind )
import VarSet
+import SrcLoc ( Located(..), unLoc, noLoc, getLoc )
import Bag
import Util ( isIn )
-import Maybes ( maybeToBool )
-import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNotTopLevel )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec,
+ isNotTopLevel, isAlwaysActive )
import FiniteMap ( listToFM, lookupFM )
-import PrelNames ( ioTyConName, mainKey, hasKey )
import Outputable
\end{code}
dictionaries, which we resolve at the module level.
\begin{code}
-tcTopBinds :: RenamedHsBinds -> TcM ((TcMonoBinds, TcEnv), LIE)
+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 $
- tcGetEnv `thenNF_Tc` \ env ->
- returnTc ((EmptyMonoBinds, env), emptyLIE)
+ = tc_binds_and_then TopLevel glue binds $
+ do { env <- getLclEnv
+ ; return (emptyLHsBinds, env) }
where
- glue is_rec binds1 (binds2, thing) = (binds1 `AndMonoBinds` binds2, thing)
-
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive MonoBinds
+ glue (HsBindGroup binds1 _ _) (binds2, env) = (binds1 `unionBags` binds2, env)
+ glue (HsIPBinds _) _ = panic "Top-level HsIpBinds"
+ -- Can't have a HsIPBinds at top level
+
+tcHsBootSigs :: [HsBindGroup Name] -> TcM (LHsBinds TcId, TcLclEnv)
+-- A hs-boot file has only one BindGroup, and it only has type
+-- signatures in it. The renamer checked all this
+tcHsBootSigs [HsBindGroup _ sigs _]
+ = do { ids <- mapM (addLocM tc_sig) (filter isVanillaLSig sigs)
+ ; tcExtendIdEnv ids $ do
+ { env <- getLclEnv
+ ; return (emptyLHsBinds, env) }}
+ where
+ tc_sig (Sig (L _ name) ty)
+ = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; return (mkLocalId name sigma_ty) }
tcBindsAndThen
- :: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator
- -> RenamedHsBinds
- -> TcM (thing, LIE)
- -> TcM (thing, LIE)
+ :: (HsBindGroup TcId -> thing -> thing) -- Combinator
+ -> [HsBindGroup Name]
+ -> TcM thing
+ -> TcM thing
tcBindsAndThen = tc_binds_and_then NotTopLevel
-tc_binds_and_then top_lvl combiner EmptyBinds do_next
- = do_next
-tc_binds_and_then top_lvl combiner (MonoBind EmptyMonoBinds sigs is_rec) do_next
+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
-tc_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next
- = tc_binds_and_then top_lvl combiner b1 $
- tc_binds_and_then top_lvl combiner b2 $
- do_next
+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') ->
-tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
- = -- TYPECHECK THE SIGNATURES
- mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs ->
-
- tcBindWithSigs top_lvl bind tc_ty_sigs
- sigs is_rec `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
-
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds ->
+
+ returnM (combiner (HsIPBinds binds') $
+ combiner (HsBindGroup dict_binds [] Recursive) result)
+ where
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (IPBind ip expr)
+ = newTyFlexiVarTy argTypeKind `thenM` \ ty ->
+ 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
+ | isEmptyLHsBinds binds
+ = do_next
+ | otherwise
+ = -- BRING ANY SCOPED TYPE VARIABLES INTO SCOPE
+ -- Notice that they scope over
+ -- a) the type signatures in the binding group
+ -- b) the bindings in the group
+ -- c) the scope of the binding group (the "in" part)
+ tcAddLetBoundTyVars binds $
+
+ case top_lvl of
+ TopLevel -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ -> tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+ tc_body poly_ids `thenM` \ (prag_binds, thing) ->
+ returnM (combiner (HsBindGroup
+ (poly_binds `unionBags` prag_binds)
+ [] -- no sigs
+ Recursive)
+ thing)
+
+ NotTopLevel -- For nested bindings we must do the bindInstsOfLocalFuns thing.
+ | not (isRec is_rec) -- Non-recursive group
+ -> -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+ getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) ->
+
+ -- Create specialisations of functions bound here
+ bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
+
+ returnM (
+ combiner (HsBindGroup poly_binds [] NonRecursive) $
+ combiner (HsBindGroup prag_binds [] NonRecursive) $
+ combiner (HsBindGroup lie_binds [] Recursive) $
+ -- NB: the binds returned by tcSimplify and
+ -- bindInstsOfLocalFuns aren't guaranteed in
+ -- dependency order (though we could change that);
+ -- hence the Recursive marker.
+ thing)
+
+ | otherwise
+ -> -- NB: polymorphic recursion means that a function
+ -- may use an instance of itself, we must look at the LIE arising
+ -- from the function's own right hand side. Hence the getLIE
+ -- encloses the tcBindWithSigs.
+
+ getLIE (
+ tcBindWithSigs top_lvl binds sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+ tc_body poly_ids `thenM` \ (prag_binds, thing) ->
+ returnM (poly_ids, poly_binds `unionBags` prag_binds, thing)
+ ) `thenM` \ ((poly_ids, extra_binds, thing), lie) ->
+
+ bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
+
+ returnM (combiner (HsBindGroup
+ (extra_binds `unionBags` lie_binds)
+ [] Recursive) thing
+ )
+ where
+ tc_body poly_ids -- Type check the pragmas and "thing inside"
+ = -- Extend the environment to bind the new polymorphic Ids
+ tcExtendIdEnv poly_ids $
-- Build bindings and IdInfos corresponding to user pragmas
- tcSpecSigs sigs `thenTc` \ (prag_binds, prag_lie) ->
-
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie) ->
-
- -- Create specialisations of functions bound here
- -- We want to keep non-recursive things non-recursive
- -- so that we desugar unboxed bindings correctly
- case (top_lvl, is_rec) of
-
- -- 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
- (TopLevel, _)
- -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing,
- thing_lie `plusLIE` prag_lie `plusLIE` poly_lie)
-
- (NotTopLevel, NonRecursive)
- -> bindInstsOfLocalFuns
- (thing_lie `plusLIE` prag_lie)
- poly_ids `thenTc` \ (thing_lie', lie_binds) ->
-
- returnTc (
- combiner NonRecursive poly_binds $
- combiner NonRecursive prag_binds $
- combiner Recursive lie_binds $
- -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
- -- aren't guaranteed in dependency order (though we could change
- -- that); hence the Recursive marker.
- thing,
-
- thing_lie' `plusLIE` poly_lie
- )
+ tcSpecSigs sigs `thenM` \ prag_binds ->
- (NotTopLevel, Recursive)
- -> bindInstsOfLocalFuns
- (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie)
- poly_ids `thenTc` \ (final_lie, lie_binds) ->
-
- returnTc (
- combiner Recursive (
- poly_binds `andMonoBinds`
- lie_binds `andMonoBinds`
- prag_binds) thing,
- final_lie
- )
-\end{code}
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenM` \ thing ->
-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 (thing, LIE, thing_ty))
-% -> TcM ((TcHsBinds, thing), LIE, thing_ty)
-%
-% tcBindsAndThen EmptyBinds do_next
-% = do_next `thenTc` \ (thing, lie, thing_ty) ->
-% returnTc ((EmptyBinds, thing), lie, thing_ty)
-%
-% tcBindsAndThen (ThenBinds binds1 binds2) do_next
-% = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
-% `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
-%
-% returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-%
-% 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
- :: TopLevelFlag
- -> RenamedMonoBinds
- -> [TcSigInfo]
- -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs
- -> RecFlag
- -> TcM (TcMonoBinds, LIE, [TcId])
-
-tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec
- = recoverTc (
- -- If typechecking the binds fails, then return with each
- -- signature-less binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTyVar boxedTypeKind `thenNF_Tc` \ alpha_tv ->
- let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- binder_names = collectMonoBinders 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 -> mkVanillaId name forall_a_a -- No signature
- in
- returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
- ) $
-
- -- TYPECHECK THE BINDINGS
- tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) ->
-
- -- CHECK THAT THE SIGNATURES MATCH
- -- (must do this before getTyVarsToGen)
- checkSigMatch top_lvl binder_names mono_ids tc_ty_sigs `thenTc` \ maybe_sig_theta ->
-
- -- IMPROVE the LIE
- -- Force any unifications dictated by functional dependencies.
- -- Because unification may happen, it's important that this step
- -- come before:
- -- - computing vars over which to quantify
- -- - zonking the generalized type vars
- let lie_avail = case maybe_sig_theta of
- Nothing -> emptyLIE
- Just (_, la) -> la
- lie_avail_req = lie_avail `plusLIE` lie_req in
- tcImprove lie_avail_req `thenTc_`
-
- -- 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
- let
- mono_id_tys = map idType mono_ids
- in
- getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
-
- -- Finally, zonk the generalised type variables to real TyVars
- -- This commits any unbound kind variables to boxed kind
- -- I'm a little worried that such a kind variable might be
- -- free in the environment, but I don't think it's possible for
- -- this to happen when the type variable is not free in the envt
- -- (which it isn't). SLPJ Nov 98
- mapTc zonkTcTyVarToTyVar (varSetElems tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
- let
- real_tyvars_to_gen = mkVarSet real_tyvars_to_gen_list
- -- It's important that the final list
- -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
- -- zonked, *including boxity*, because they'll be included in the forall types of
- -- the polymorphic Ids, and instances of these Ids will be generated from them.
- --
- -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass
- -- real_tyvars_to_gen
- in
-
- -- SIMPLIFY THE LIE
- tcExtendGlobalTyVars tyvars_not_to_gen (
- let ips = getIPsOfLIE lie_avail_req in
- if null real_tyvars_to_gen_list && (null ips || not is_unrestricted) then
- -- No polymorphism, and no IPs, so no need to simplify context
- returnTc (lie_req, EmptyMonoBinds, [])
- else
- case maybe_sig_theta of
- Nothing ->
- -- No signatures, so just simplify the lie
- -- NB: no signatures => no polymorphic recursion, so no
- -- need to use lie_avail (which will be empty anyway)
- tcSimplify (text "tcBinds1" <+> ppr binder_names)
- real_tyvars_to_gen lie_req `thenTc` \ (lie_free, dict_binds, lie_bound) ->
- returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
-
- Just (sig_theta, lie_avail) ->
- -- There are signatures, and their context is sig_theta
- -- Furthermore, lie_avail is an LIE containing the 'method insts'
- -- for the things bound here
-
- zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' ->
- newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) ->
- -- It's important that sig_theta is zonked, because
- -- dict_id is later used to form the type of the polymorphic thing,
- -- and forall-types must be zonked so far as their bound variables
- -- are concerned
-
- let
- -- The "givens" is the stuff available. We get that from
- -- the context of the type signature, BUT ALSO the lie_avail
- -- so that polymorphic recursion works right (see comments at end of fn)
- givens = dicts_sig `plusLIE` lie_avail
- in
-
- -- Check that the needed dicts can be expressed in
- -- terms of the signature ones
- tcAddErrCtxt (bindSigsCtxt tysig_names) $
- tcSimplifyAndCheck
- (ptext SLIT("type signature for") <+> pprQuotedList binder_names)
- real_tyvars_to_gen givens lie_req `thenTc` \ (lie_free, dict_binds) ->
-
- returnTc (lie_free, dict_binds, dict_ids)
-
- ) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
-
- -- GET THE FINAL MONO_ID_TYS
- zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
-
-
- -- CHECK FOR BOGUS UNPOINTED BINDINGS
- (if any isUnLiftedType zonked_mono_id_types then
- -- Unlifted bindings must be non-recursive,
- -- not top level, and non-polymorphic
- checkTc (isNotTopLevel top_lvl)
- (unliftedBindErr "Top-level" mbind) `thenTc_`
- checkTc (case is_rec of {Recursive -> False; NonRecursive -> True})
- (unliftedBindErr "Recursive" mbind) `thenTc_`
- checkTc (null real_tyvars_to_gen_list)
- (unliftedBindErr "Polymorphic" mbind)
- else
- returnTc ()
- ) `thenTc_`
-
- ASSERT( not (any ((== unboxedTypeKind) . tyVarKind) real_tyvars_to_gen_list) )
- -- The instCantBeGeneralised stuff in tcSimplify should have
- -- already raised an error if we're trying to generalise an
- -- unboxed tyvar (NB: unboxed tyvars are always introduced
- -- along with a class constraint) and it's better done there
- -- because we have more precise origin information.
- -- That's why we just use an ASSERT here.
-
-
- -- BUILD THE POLYMORPHIC RESULT IDs
- mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids ->
- let
- exports = zipWith mk_export binder_names zonked_mono_ids
- dict_tys = map idType dicts_bound
-
- inlines = mkNameSet [name | InlineSig name _ loc <- inline_sigs]
- no_inlines = listToFM ([(name, IMustNotBeINLINEd False phase) | NoInlineSig name phase loc <- inline_sigs] ++
- [(name, IMustNotBeINLINEd True phase) | InlineSig name phase loc <- inline_sigs, maybeToBool phase])
- -- "INLINE n foo" means inline foo, but not until at least phase n
- -- "NOINLINE n foo" means don't inline foo until at least phase n, and even
- -- then only if it is small enough etc.
- -- "NOINLINE foo" means don't inline foo ever, which we signal with a (IMustNotBeINLINEd Nothing)
- -- See comments in CoreUnfold.blackListed for the Authorised Version
-
- mk_export binder_name zonked_mono_id
- = (tyvars,
- attachNoInlinePrag no_inlines poly_id,
- zonked_mono_id)
+tcBindWithSigs :: TopLevelFlag
+ -> LHsBinds Name
+ -> [LSig Name]
+ -> RecFlag
+ -> TcM (LHsBinds TcId, [TcId])
+ -- The returned TcIds are guaranteed zonked
+
+tcBindWithSigs top_lvl mbind sigs is_rec = do
+ { -- TYPECHECK THE SIGNATURES
+ tc_ty_sigs <- recoverM (returnM []) $
+ tcTySigs (filter isVanillaLSig sigs)
+ ; let lookup_sig = lookupSig tc_ty_sigs
+
+ -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+ ; recoverM (recoveryCode mbind lookup_sig) $ do
+
+ { traceTc (ptext SLIT("--------------------------------------------------------"))
+ ; traceTc (ptext SLIT("Bindings for") <+> ppr (collectHsBindBinders mbind))
+
+ -- TYPECHECK THE BINDINGS
+ ; ((mbind', mono_bind_infos), lie_req)
+ <- getLIE (tcMonoBinds mbind lookup_sig is_rec)
+
+ -- CHECK FOR UNLIFTED BINDINGS
+ -- These must be non-recursive etc, and are not generalised
+ -- They desugar to a case expression in the end
+ ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
+ ; if any isUnLiftedType zonked_mono_tys then
+ do { -- Unlifted bindings
+ checkUnliftedBinds top_lvl is_rec mbind
+ ; extendLIEs lie_req
+ ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
+ mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id)
+ mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id)
+
+ ; return ( unitBag $ noLoc $ AbsBinds [] [] exports emptyNameSet mbind',
+ [poly_id | (_, poly_id, _) <- exports]) } -- Guaranteed zonked
+
+ else do -- The normal lifted case: GENERALISE
+ { is_unres <- isUnRestrictedGroup mbind tc_ty_sigs
+ ; (tyvars_to_gen, dict_binds, dict_ids)
+ <- setSrcSpan (getLoc (head (bagToList mbind))) $
+ -- TODO: location a bit awkward, but the mbinds have been
+ -- dependency analysed and may no longer be adjacent
+ addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
+ generalise top_lvl is_unres mono_bind_infos tc_ty_sigs 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
+ ; let
+ exports = map mk_export mono_bind_infos
+ poly_ids = [poly_id | (_, poly_id, _) <- exports]
+ dict_tys = map idType dict_ids
+
+ inlines = mkNameSet [ name
+ | L _ (InlineSig True (L _ name) _) <- sigs]
+ -- Any INLINE sig (regardless of phase control)
+ -- makes the RHS look small
+ inline_phases = listToFM [ (name, phase)
+ | L _ (InlineSig _ (L _ name) phase) <- sigs,
+ not (isAlwaysActive phase)]
+ -- Set the IdInfo field to control the inline phase
+ -- AlwaysActive is the default, so don't bother with them
+ add_inlines id = attachInlinePhase inline_phases id
+
+ mk_export (binder_name, mb_sig, mono_id)
+ = case mb_sig of
+ Just sig -> (sig_tvs sig, add_inlines (sig_id sig), mono_id)
+ Nothing -> (tyvars_to_gen', add_inlines new_poly_id, mono_id)
where
- (tyvars, poly_id) =
- case maybeSig tc_ty_sigs binder_name of
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) ->
- (sig_tyvars, sig_poly_id)
- Nothing -> (real_tyvars_to_gen_list, new_poly_id)
-
- new_poly_id = mkVanillaId binder_name poly_ty
- poly_ty = mkForAllTys real_tyvars_to_gen_list
- $ 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.
-
- pat_binders :: [Name]
- pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds)
- in
- -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS
- mapTc (\id -> checkTc (not (idName id `elem` pat_binders
- && isUnboxedType (idType id)))
- (unboxedPatBindErr id)) zonked_mono_ids
- `thenTc_`
-
- -- BUILD RESULTS
- returnTc (
- -- pprTrace "binding.." (ppr ((dicts_bound, dict_binds), exports, [idType poly_id | (_, poly_id, _) <- exports])) $
- AbsBinds real_tyvars_to_gen_list
- dicts_bound
- exports
- inlines
- (dict_binds `andMonoBinds` mbind'),
- lie_free,
- [poly_id | (_, poly_id, _) <- exports]
- )
+ new_poly_id = mkLocalId binder_name poly_ty
+ poly_ty = mkForAllTys tyvars_to_gen'
+ $ mkFunTys dict_tys
+ $ idType mono_id
+
+ -- ZONK THE poly_ids, because they are used to extend the type
+ -- environment; see the invariant on TcEnv.tcExtendIdEnv
+ ; zonked_poly_ids <- mappM zonkId poly_ids
+
+ ; traceTc (text "binding:" <+> ppr ((dict_ids, dict_binds),
+ exports, map idType zonked_poly_ids))
+
+ ; return (
+ unitBag $ noLoc $
+ AbsBinds tyvars_to_gen'
+ dict_ids
+ exports
+ inlines
+ (dict_binds `unionBags` mbind'),
+ zonked_poly_ids
+ )
+ } } }
+
+-- If typechecking the binds fails, then return with each
+-- signature-less binder given type (forall a.a), to minimise
+-- subsequent error messages
+recoveryCode mbind lookup_sig
+ = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
+ ; return (emptyLHsBinds, poly_ids) }
where
- tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs]
- is_unrestricted = isUnRestrictedGroup tysig_names mbind
-
-justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds
-justPatBindings (AndMonoBinds b1 b2) binds =
- justPatBindings b1 (justPatBindings b2 binds)
-justPatBindings other_bind binds = binds
-
-attachNoInlinePrag no_inlines bndr
- = case lookupFM no_inlines (idName bndr) of
+ forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
+ binder_names = collectHsBindBinders mbind
+ poly_ids = map mk_dummy binder_names
+ mk_dummy name = case lookup_sig name of
+ Just sig -> sig_id sig -- Signature
+ Nothing -> mkLocalId name forall_a_a -- No signature
+
+attachInlinePhase inline_phases bndr
+ = case lookupFM inline_phases (idName bndr) of
Just prag -> bndr `setInlinePragma` prag
Nothing -> bndr
+
+-- Check that non-overloaded unlifted bindings are
+-- a) non-recursive,
+-- b) not top level,
+-- c) not a multiple-binding group (more or less implied by (a))
+
+checkUnliftedBinds top_lvl is_rec mbind
+ = checkTc (isNotTopLevel top_lvl)
+ (unliftedBindErr "Top-level" mbind) `thenM_`
+ checkTc (isNonRec is_rec)
+ (unliftedBindErr "Recursive" mbind) `thenM_`
+ checkTc (isSingletonBag mbind)
+ (unliftedBindErr "Multiple" mbind)
\end{code}
+
Polymorphic recursion
~~~~~~~~~~~~~~~~~~~~~
The game plan for polymorphic recursion in the code above is
%************************************************************************
%* *
+\subsection{tcMonoBind}
+%* *
+%************************************************************************
+
+@tcMonoBinds@ deals with a single @MonoBind@.
+The signatures have been dealt with already.
+
+\begin{code}
+tcMonoBinds :: LHsBinds Name
+ -> TcSigFun -> RecFlag
+ -> TcM (LHsBinds TcId, [MonoBindInfo])
+
+tcMonoBinds binds lookup_sig is_rec
+ = do { tc_binds <- mapBagM (wrapLocM (tcLhs lookup_sig)) binds
+
+ -- Bring (a) the scoped type variables, and (b) the Ids, into scope for the RHSs
+ -- For (a) it's ok to bring them all into scope at once, even
+ -- though each type sig should scope only over its own RHS,
+ -- because the renamer has sorted all that out.
+ ; let mono_info = getMonoBindInfo tc_binds
+ rhs_tvs = [ (name, mkTyVarTy tv)
+ | (_, Just sig, _) <- mono_info,
+ (name, tv) <- sig_scoped sig `zip` sig_tvs sig ]
+ rhs_id_env = map mk mono_info -- A binding for each term variable
+
+ ; binds' <- tcExtendTyVarEnv2 rhs_tvs $
+ tcExtendIdEnv2 rhs_id_env $
+ traceTc (text "tcMonoBinds" <+> vcat [ppr n <+> ppr id <+> ppr (idType id) | (n,id) <- rhs_id_env]) `thenM_`
+ mapBagM (wrapLocM tcRhs) tc_binds
+ ; return (binds', mono_info) }
+ where
+ mk (name, Just sig, _) = (name, sig_id sig) -- Use the type sig if there is one
+ mk (name, Nothing, mono_id) = (name, mono_id) -- otherwise use a monomorphic version
+
+------------------------
+-- 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 lookup_sig (FunBind (L nm_loc name) inf matches)
+ = do { let mb_sig = lookup_sig name
+ ; mono_name <- newLocalName name
+ ; mono_ty <- mk_mono_ty mb_sig
+ ; let mono_id = mkLocalId mono_name mono_ty
+ ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
+ where
+ mk_mono_ty (Just sig) = return (sig_tau sig)
+ mk_mono_ty Nothing = newTyFlexiVarTy argTypeKind
+
+tcLhs lookup_sig bind@(PatBind pat grhss _)
+ = do { let tc_pat exp_ty = tcPat (LetPat lookup_sig) pat exp_ty lookup_infos
+ ; ((pat', ex_tvs, infos), pat_ty)
+ <- addErrCtxt (patMonoBindsCtxt pat grhss)
+ (tcInfer tc_pat)
+
+ -- Don't know how to deal with pattern-bound existentials yet
+ ; checkTc (null ex_tvs) (existentialExplode bind)
+
+ ; return (TcPatBind infos pat' grhss pat_ty) }
+ where
+ names = collectPatBinders pat
+
+ -- After typechecking the pattern, look up the binder
+ -- names, which the pattern has brought into scope.
+ lookup_infos :: TcM [MonoBindInfo]
+ lookup_infos = do { mono_ids <- tcLookupLocalIds names
+ ; return [ (name, lookup_sig name, mono_id)
+ | (name, mono_id) <- names `zip` mono_ids] }
+
+-------------------
+tcRhs :: TcMonoBind -> TcM (HsBind TcId)
+tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
+ = do { matches' <- tcMatchesFun (idName mono_id) matches
+ (Check (idType mono_id))
+ ; return (FunBind fun' inf matches') }
+
+tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
+ = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
+ tcGRHSsPat grhss (Check pat_ty)
+ ; return (PatBind pat' grhss' pat_ty) }
+
+
+---------------------
+getMonoBindInfo :: Bag (Located TcMonoBind) -> [MonoBindInfo]
+getMonoBindInfo tc_binds
+ = foldrBag (get_info . unLoc) [] tc_binds
+ where
+ get_info (TcFunBind info _ _ _) rest = info : rest
+ get_info (TcPatBind infos _ _ _) rest = infos ++ rest
+\end{code}
+
+
+%************************************************************************
+%* *
\subsection{getTyVarsToGen}
%* *
%************************************************************************
+Type signatures are tricky. See Note [Signature skolems] in TcType
+
+\begin{code}
+tcTySigs :: [LSig Name] -> TcM [TcSigInfo]
+-- The trick here is that all the signatures should have the same
+-- context, and we want to share type variables for that context, so that
+-- all the right hand sides agree a common vocabulary for their type
+-- constraints
+tcTySigs [] = return []
+
+tcTySigs sigs
+ = do { (tc_sig1 : tc_sigs) <- mappM tcTySig sigs
+ ; mapM (check_ctxt tc_sig1) tc_sigs
+ ; return (tc_sig1 : tc_sigs) }
+ where
+ -- Check tha 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).
+ --
+ -- We unify them because, with polymorphic recursion, their types
+ -- might not otherwise be related. This is a rather subtle issue.
+ check_ctxt :: TcSigInfo -> TcSigInfo -> TcM ()
+ check_ctxt sig1@(TcSigInfo { sig_theta = theta1 }) sig@(TcSigInfo { sig_theta = theta })
+ = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
+ addErrCtxt (sigContextsCtxt sig1 sig) $
+ unifyTheta theta1 theta
+
+
+tcTySig :: LSig Name -> TcM TcSigInfo
+tcTySig (L span (Sig (L _ name) ty))
+ = setSrcSpan span $
+ do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
+ ; (tvs, theta, tau) <- tcInstSigType name sigma_ty
+ ; loc <- getInstLoc (SigOrigin (SigSkol name))
+
+ ; let poly_id = mkLocalId name sigma_ty
+
+ -- 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.)
+ scoped_names = case ty of
+ L _ (HsForAllTy _ tvs _ _) -> hsLTyVarNames tvs
+ other -> []
+
+ ; return (TcSigInfo { sig_id = poly_id, sig_scoped = scoped_names,
+ sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
+ sig_loc = loc }) }
+\end{code}
+
+\begin{code}
+generalise :: TopLevelFlag -> Bool -> [MonoBindInfo] -> [TcSigInfo] -> [Inst]
+ -> TcM ([TcTyVar], TcDictBinds, [TcId])
+generalise top_lvl is_unrestricted mono_infos sigs lie_req
+ | not is_unrestricted -- RESTRICTED CASE
+ = -- Check signature contexts are empty
+ do { checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr bndr_names)
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndr_names
+ 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 { let sig1 = head sigs
+ ; sig_lie <- newDictsAtLoc (sig_loc sig1) (sig_theta sig1)
+ ; 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)
+ 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
+ bndr_names = bndrNames mono_infos
+ tau_tvs = foldr (unionVarSet . tyVarsOfType . getMonoType) emptyVarSet mono_infos
+ is_mono_sig sig = null (sig_theta sig)
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders bndr_names
+
+ mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
+ sig_theta = theta, sig_tau = tau, sig_loc = loc }) mono_id
+ = Method mono_id poly_id (mkTyVarTys tvs) theta tau loc
+
+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 zonk_one sig_tvs
+ ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
+ ; return zonked_tvs }
+ where
+ zonk_one sig_tv = do { ty <- zonkTcTyVar sig_tv
+ ; return (tcGetTyVar "checkDistinctTyVars" ty) }
+ -- 'ty' is bound to be a type variable, because SigSkolTvs
+ -- can only be unified with type variables
+
+ check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
+ -- The TyVarEnv maps each zonked type variable back to its
+ -- corresponding user-written signature type variable
+ check_dup acc (sig_tv, zonked_tv)
+ = case lookupVarEnv acc zonked_tv of
+ Just sig_tv' -> bomb_out sig_tv sig_tv'
+
+ Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
+
+ bomb_out sig_tv1 sig_tv2
+ = failWithTc (ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
+ <+> ptext SLIT("is unified with another quantified type variable")
+ <+> ppr tidy_tv2)
+ where
+ (env1, tidy_tv1) = tidyOpenTyVar emptyTidyEnv sig_tv1
+ (_env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
+\end{code}
+
+
@getTyVarsToGen@ decides what type variables to generalise over.
For a "restricted group" -- see the monomorphism restriction
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_id_tys lie
- = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
- zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys ->
- let
- body_tyvars = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars
- fds = getAllFunDepsOfLIE lie
- in
- if is_unrestricted
- then
- -- We need to augment the type variables that appear explicitly in
- -- the type by those that are determined by the functional dependencies.
- -- e.g. suppose our type is C a b => a -> a
- -- with the fun-dep a->b
- -- Then we should generalise over b too; otherwise it will be
- -- reported as ambiguous.
- zonkFunDeps fds `thenNF_Tc` \ fds' ->
- let
- extended_tyvars = oclose fds' body_tyvars
- in
- returnNF_Tc (emptyVarSet, extended_tyvars)
- else
- -- This recover and discard-errs is to avoid duplicate error
- -- messages; this, after all, is an "extra" call to tcSimplify
- recoverNF_Tc (returnNF_Tc (emptyVarSet, body_tyvars)) $
- discardErrsTc $
-
- tcSimplify (text "getTVG") body_tyvars lie `thenTc` \ (_, _, constrained_dicts) ->
- let
- -- ASSERT: dicts_sig is already zonked!
- constrained_tyvars = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts
- reduced_tyvars_to_gen = body_tyvars `minusVarSet` constrained_tyvars
- in
- returnTc (constrained_tyvars, reduced_tyvars_to_gen)
-\end{code}
-
-
-\begin{code}
-isUnRestrictedGroup :: [Name] -- Signatures given for these
- -> RenamedMonoBinds
- -> Bool
+isUnRestrictedGroup :: LHsBinds Name -> [TcSigInfo] -> TcM Bool
+isUnRestrictedGroup binds sigs
+ = do { mono_restriction <- doptM Opt_MonomorphismRestriction
+ ; return (not mono_restriction || all_unrestricted) }
+ where
+ all_unrestricted = all (unrestricted . unLoc) (bagToList binds)
+ tysig_names = map (idName . sig_id) sigs
+
+ unrestricted (PatBind other _ _) = False
+ unrestricted (VarBind v _) = v `is_elem` tysig_names
+ unrestricted (FunBind v _ matches) = unrestricted_match matches
+ || unLoc v `is_elem` tysig_names
+
+ unrestricted_match (MatchGroup (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 other _ _) = False
-isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (FunMonoBind v _ matches _) = any isUnRestrictedMatch matches ||
- v `is_elem` sigs
-isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 &&
- isUnRestrictedGroup sigs mb2
-isUnRestrictedGroup sigs EmptyMonoBinds = True
-
-isUnRestrictedMatch (Match _ [] Nothing _) = False -- No args, no signature
-isUnRestrictedMatch other = True -- Some args or a signature
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection{tcMonoBind}
-%* *
-%************************************************************************
-
-@tcMonoBinds@ deals with a single @MonoBind@.
-The signatures have been dealt with already.
-
-\begin{code}
-tcMonoBinds :: RenamedMonoBinds
- -> [TcSigInfo]
- -> RecFlag
- -> TcM (TcMonoBinds,
- LIE, -- LIE required
- [Name], -- Bound names
- [TcId]) -- Corresponding monomorphic bound things
-
-tcMonoBinds mbinds tc_ty_sigs is_rec
- = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) ->
- let
- id_list = bagToList ids
- (names, mono_ids) = unzip id_list
-
- -- This last defn is the key one:
- -- extend the val envt with bindings for the
- -- things bound in this group, overriding the monomorphic
- -- ids with the polymorphic ones from the pattern
- extra_val_env = case is_rec of
- Recursive -> map mk_bind id_list
- NonRecursive -> []
- in
- -- Don't know how to deal with pattern-bound existentials yet
- checkTc (isEmptyBag tvs && isEmptyBag lie_avail)
- (existentialExplode mbinds) `thenTc_`
-
- -- *Before* checking the RHSs, but *after* checking *all* the patterns,
- -- extend the envt with bindings for all the bound ids;
- -- and *then* override with the polymorphic Ids from the signatures
- -- That is the whole point of the "complete_it" stuff.
- --
- -- There's a further wrinkle: we have to delay extending the environment
- -- until after we've dealt with any pattern-bound signature type variables
- -- Consider f (x::a) = ...f...
- -- We're going to check that a isn't unified with anything in the envt,
- -- so f itself had better not be! So we pass the envt binding f into
- -- complete_it, which extends the actual envt in TcMatches.tcMatch, after
- -- dealing with the signature tyvars
-
- complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) ->
-
- returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids)
- where
-
- -- This function is used when dealing with a LHS binder; we make a monomorphic
- -- version of the Id. We check for type signatures
- tc_pat_bndr name pat_ty
- = case maybeSig tc_ty_sigs name of
- Nothing
- -> newLocalId (getOccName name) pat_ty (getSrcLoc name)
-
- Just (TySigInfo _ _ _ _ _ mono_id _ _)
- -> tcAddSrcLoc (getSrcLoc name) $
- unifyTauTy (idType mono_id) pat_ty `thenTc_`
- returnTc mono_id
-
- mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of
- Nothing -> (name, mono_id)
- Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id)
-
- tc_mb_pats EmptyMonoBinds
- = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
-
- tc_mb_pats (AndMonoBinds mb1 mb2)
- = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) ->
- tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) ->
- let
- complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) ->
- complete_it2 xve `thenTc` \ (mb2', lie2) ->
- returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2)
- in
- returnTc (complete_it,
- lie_req1 `plusLIE` lie_req2,
- tvs1 `unionBags` tvs2,
- ids1 `unionBags` ids2,
- lie_avail1 `plusLIE` lie_avail2)
-
- tc_mb_pats (FunMonoBind name inf matches locn)
- = newTyVarTy kind `thenNF_Tc` \ bndr_ty ->
- tc_pat_bndr name bndr_ty `thenTc` \ bndr_id ->
- let
- complete_it xve = tcAddSrcLoc locn $
- tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) ->
- returnTc (FunMonoBind bndr_id inf matches' locn, lie)
- in
- returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
-
- tc_mb_pats bind@(PatMonoBind pat grhss locn)
- = tcAddSrcLoc locn $
- newTyVarTy kind `thenNF_Tc` \ pat_ty ->
-
- -- Now typecheck the pattern
- -- We don't support binding fresh type variables in the
- -- pattern of a pattern binding. For example, this is illegal:
- -- (x::a, y::b) = e
- -- whereas this is ok
- -- (x::Int, y::Bool) = e
- --
- -- We don't check explicitly for this problem. Instead, we simply
- -- type check the pattern with tcPat. If the pattern mentions any
- -- fresh tyvars we simply get an out-of-scope type variable error
- tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
- let
- complete_it xve = tcAddSrcLoc locn $
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- tcExtendLocalValEnv xve $
- tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) ->
- returnTc (PatMonoBind pat' grhss' locn, lie)
- in
- returnTc (complete_it, lie_req, tvs, ids, lie_avail)
-
- -- Figure out the appropriate kind for the pattern,
- -- and generate a suitable type variable
- kind = case is_rec of
- Recursive -> boxedTypeKind -- Recursive, so no unboxed types
- NonRecursive -> openTypeKind -- Non-recursive, so we permit unboxed types
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{Signatures}
-%* *
-%************************************************************************
-
-@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 :: TopLevelFlag -> [Name] -> [TcId] -> [TcSigInfo] -> TcM (Maybe (TcThetaType, LIE))
-checkSigMatch top_lvl binder_names mono_ids sigs
- | main_bound_here
- = -- First unify the main_id with IO t, for any old t
- tcSetErrCtxt mainTyCheckCtxt (
- tcLookupTyCon ioTyConName `thenTc` \ ioTyCon ->
- newTyVarTy boxedTypeKind `thenNF_Tc` \ t_tv ->
- unifyTauTy ((mkTyConApp ioTyCon [t_tv]))
- (idType main_mono_id)
- ) `thenTc_`
-
- -- Now check the signatures
- -- Must do this after the unification with IO t,
- -- in case of a silly signature like
- -- main :: forall a. a
- -- The unification to IO t will bind the type variable 'a',
- -- which is just waht check_one_sig looks for
- mapTc check_one_sig sigs `thenTc_`
- mapTc check_main_ctxt sigs `thenTc_`
- returnTc (Just ([], emptyLIE))
-
- | not (null sigs)
- = mapTc check_one_sig sigs `thenTc_`
- mapTc check_one_ctxt all_sigs_but_first `thenTc_`
- returnTc (Just (theta1, sig_lie))
-
- | otherwise
- = returnTc Nothing -- No constraints from type sigs
-
- where
- (TySigInfo _ id1 _ theta1 _ _ _ _ : all_sigs_but_first) = sigs
-
- sig1_dict_tys = mk_dict_tys theta1
- n_sig1_dict_tys = length sig1_dict_tys
- sig_lie = mkLIE (concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs])
-
- maybe_main = find_main top_lvl binder_names mono_ids
- main_bound_here = maybeToBool maybe_main
- Just main_mono_id = maybe_main
-
- -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK
- -- Doesn't affect substitution
- check_one_sig (TySigInfo _ id sig_tyvars sig_theta sig_tau _ _ src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxtM (sigCtxt (sig_msg id) sig_tyvars sig_theta sig_tau) $
- checkSigTyVars sig_tyvars (idFreeTyVars id)
-
-
- -- 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
- check_one_ctxt 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 THAT FOR A GROUP INVOLVING Main.main, all
- -- the signature contexts are empty (what a bore)
- check_main_ctxt sig@(TySigInfo _ id _ theta _ _ _ src_loc)
- = tcAddSrcLoc src_loc $
- checkTc (null theta) (mainContextsErr id)
-
- mk_dict_tys theta = map mkPredTy theta
-
- sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id)
-
- -- Search for Main.main in the binder_names, return corresponding mono_id
- find_main NotTopLevel binder_names mono_ids = Nothing
- find_main TopLevel binder_names mono_ids = go binder_names mono_ids
- go [] [] = Nothing
- go (n:ns) (m:ms) | n `hasKey` mainKey = Just m
- | otherwise = go ns ms
\end{code}
{-# SPECIALISE f :: <type> = g #-}
which promised that g implemented f at <type>, but we do that with
a RULE now:
- {-# SPECIALISE (f::<type) = g #-}
+ {-# RULES (f::<type>) = g #-}
\begin{code}
-tcSpecSigs :: [RenamedSig] -> TcM (TcMonoBinds, LIE)
-tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
+tcSpecSigs :: [LSig Name] -> TcM (LHsBinds TcId)
+tcSpecSigs (L loc (SpecSig (L nm_loc name) poly_ty) : sigs)
= -- SPECIALISE f :: forall b. theta => tau = g
- tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
+ setSrcSpan loc $
+ addErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
- tcHsSigType poly_ty `thenTc` \ sig_ty ->
+ tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty ->
-- Check that f has a more general type, and build a RHS for
-- the spec-pragma-id at the same time
- tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) ->
+ getLIE (tcCheckSigma (L nm_loc (HsVar name)) sig_ty) `thenM` \ (spec_expr, spec_lie) ->
-- Squeeze out any Methods (see comments with tcSimplifyToDicts)
- tcSimplifyToDicts spec_lie `thenTc` \ (spec_lie1, spec_binds) ->
+ 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.
- newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id ->
+ newLocalName name `thenM` \ spec_name ->
+ let
+ spec_bind = VarBind (mkSpecPragmaId spec_name sig_ty)
+ (mkHsLet spec_binds spec_expr)
+ in
-- Do the rest and combine
- tcSpecSigs sigs `thenTc` \ (binds_rest, lie_rest) ->
- returnTc (binds_rest `andMonoBinds` VarMonoBind spec_id (mkHsLet spec_binds spec_expr),
- lie_rest `plusLIE` spec_lie1)
+ tcSpecSigs sigs `thenM` \ binds_rest ->
+ returnM (binds_rest `snocBag` L loc spec_bind)
tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
-tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE)
+tcSpecSigs [] = returnM emptyLHsBinds
\end{code}
-
%************************************************************************
%* *
\subsection[TcBinds-errors]{Error contexts and messages}
\begin{code}
-patMonoBindsCtxt bind
- = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
+-- 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)
-----------------------------------------------
valSpecSigCtxt v ty
nest 4 (ppr v <+> dcolon <+> ppr ty)]
-----------------------------------------------
-unboxedPatBindErr id
- = ptext SLIT("variable in a lazy pattern binding has unboxed type: ")
- <+> quotes (ppr id)
-
------------------------------------------------
-bindSigsCtxt ids
- = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
-
------------------------------------------------
-sigContextsErr
- = ptext SLIT("Mismatched contexts")
-
-sigContextsCtxt s1 s2
- = hang (hsep [ptext SLIT("When matching the contexts of the signatures for"),
- quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)])
- 4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)"))
-
-mainContextsErr id
- | id `hasKey` mainKey = ptext SLIT("Main.main cannot be overloaded")
- | otherwise
- = quotes (ppr id) <+> ptext SLIT("cannot be overloaded") <> char ',' <> -- sigh; workaround for cpp's inability to deal
- ptext SLIT("because it is mutually recursive with Main.main") -- with commas inside SLIT strings.
+sigContextsCtxt sig1 sig2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
+ nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
+ ppr id2 <+> dcolon <+> ppr (idType id2)]),
+ ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
+ where
+ id1 = sig_id sig1
+ id2 = sig_id sig2
-mainTyCheckCtxt
- = hsep [ptext SLIT("When checking that"), quotes (ptext SLIT("main")),
- ptext SLIT("has the required type")]
-----------------------------------------------
unliftedBindErr flavour mbind
- = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed"))
+ = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:"))
4 (ppr mbind)
+-----------------------------------------------
existentialExplode mbinds
= hang (vcat [text "My brain just exploded.",
text "I can't handle pattern bindings for existentially-quantified constructors.",
text "In the binding group"])
4 (ppr mbinds)
+
+-----------------------------------------------
+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
\end{code}
projects / ghc-hetmet.git / blobdiff