\section[TcBinds]{TcBinds}
\begin{code}
-module TcBinds ( tcBindsAndThen, tcTopBindsAndThen,
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds,
tcSpecSigs, tcBindWithSigs ) where
#include "HsVersions.h"
import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun )
import {-# SOURCE #-} TcExpr ( tcExpr )
-import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..), StmtCtxt(..),
- Match(..), collectMonoBinders, andMonoBindList, andMonoBinds
+import CmdLineOpts ( DynFlag(Opt_NoMonomorphismRestriction) )
+import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..),
+ Match(..), HsMatchContext(..),
+ collectMonoBinders, andMonoBinds,
+ collectSigTysFromMonoBinds
)
import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
-import TcHsSyn ( TcHsBinds, TcMonoBinds, TcId, zonkId, mkHsLet )
+import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet )
import TcMonad
-import Inst ( Inst, LIE, emptyLIE, mkLIE, plusLIE, plusLIEs, InstOrigin(..),
- newDicts, tyVarsOfInst, instToId,
- getAllFunDepsOfLIE, getIPsOfLIE, zonkFunDeps
+import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..),
+ newDicts, instToId
)
-import TcEnv ( tcExtendLocalValEnv,
- newSpecPragmaId, newLocalId,
- tcLookupTyCon,
- tcGetGlobalTyVars, tcExtendGlobalTyVars
+import TcEnv ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName )
+import TcUnify ( unifyTauTyLists, checkSigTyVarsWrt, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted, tcSimplifyToDicts )
+import TcMonoType ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..),
+ tcTySig, maybeSig, tcSigPolyId, tcSigMonoId, tcAddScopedTyVars
)
-import TcSimplify ( tcSimplify, tcSimplifyAndCheck, tcSimplifyToDicts )
-import TcImprove ( tcImprove )
-import TcMonoType ( tcHsSigType, checkSigTyVars,
- TcSigInfo(..), tcTySig, maybeSig, sigCtxt
- )
-import TcPat ( tcPat )
+import TcPat ( tcPat, tcSubPat, tcMonoPatBndr )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( TcType, TcThetaType,
- TcTyVar,
- newTyVarTy, newTyVar, newTyVarTy_OpenKind, tcInstTcType,
- zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVarToTyVar
+import TcMType ( newTyVar, newTyVarTy, newHoleTyVarTy,
+ zonkTcTyVarToTyVar, readHoleResult
+ )
+import TcType ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
+ mkPredTy, mkForAllTy, isUnLiftedType,
+ unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind
)
-import TcUnify ( unifyTauTy, unifyTauTyLists )
-
-import PrelInfo ( main_NAME, ioTyCon_NAME )
-import Id ( Id, mkVanillaId, setInlinePragma, idFreeTyVars )
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
import Var ( idType, idName )
-import IdInfo ( setInlinePragInfo, InlinePragInfo(..) )
-import Name ( Name, getName, getOccName, getSrcLoc )
+import Name ( Name, getSrcLoc )
import NameSet
-import Type ( mkTyVarTy, tyVarsOfTypes, mkTyConApp,
- splitSigmaTy, mkForAllTys, mkFunTys, getTyVar,
- mkPredTy, splitRhoTy, mkForAllTy, isUnLiftedType,
- isUnboxedType, unboxedTypeKind, boxedTypeKind
- )
-import FunDeps ( tyVarFunDep, oclose )
-import Var ( TyVar, tyVarKind )
+import Var ( tyVarKind )
import VarSet
import Bag
-import Util ( isIn )
-import Maybes ( maybeToBool )
-import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNotTopLevel )
+import Util ( isIn, equalLength )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isNotTopLevel,
+ isAlwaysActive )
import FiniteMap ( listToFM, lookupFM )
-import SrcLoc ( SrcLoc )
import Outputable
\end{code}
dictionaries, which we resolve at the module level.
\begin{code}
-tcTopBindsAndThen, tcBindsAndThen
+tcTopBinds :: RenamedHsBinds -> TcM ((TcMonoBinds, TcEnv), LIE)
+tcTopBinds binds
+ = tc_binds_and_then TopLevel glue binds $
+ tcGetEnv `thenNF_Tc` \ env ->
+ returnTc ((EmptyMonoBinds, env), emptyLIE)
+ where
+ glue is_rec binds1 (binds2, thing) = (binds1 `AndMonoBinds` binds2, thing)
+
+
+tcBindsAndThen
:: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator
-> RenamedHsBinds
- -> TcM s (thing, LIE)
- -> TcM s (thing, LIE)
+ -> TcM (thing, LIE)
+ -> TcM (thing, LIE)
-tcTopBindsAndThen = tc_binds_and_then TopLevel
-tcBindsAndThen = tc_binds_and_then NotTopLevel
+tcBindsAndThen = tc_binds_and_then NotTopLevel
tc_binds_and_then top_lvl combiner EmptyBinds do_next
= do_next
do_next
tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
- = -- TYPECHECK THE SIGNATURES
+ = -- 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 (collectSigTysFromMonoBinds bind) $
+
+ -- 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] $
+ tcExtendLocalValEnv poly_ids $
-- Build bindings and IdInfos corresponding to user pragmas
tcSpecSigs sigs `thenTc` \ (prag_binds, prag_lie) ->
-- Create specialisations of functions bound here
-- We want to keep non-recursive things non-recursive
- -- so that we desugar unboxed bindings correctly
+ -- so that we desugar unlifted bindings correctly
case (top_lvl, is_rec) of
-- For the top level don't bother will all this bindInstsOfLocalFuns stuff
)
\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, thing_ty))
-% -> TcM s ((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}
-
%************************************************************************
%* *
-> [TcSigInfo]
-> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs
-> RecFlag
- -> TcM s (TcMonoBinds, LIE, [TcId])
+ -> 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 ->
+ newTyVar liftedTypeKind `thenNF_Tc` \ alpha_tv ->
let
forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- binder_names = map fst (bagToList (collectMonoBinders mbind))
+ 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
+ Just sig -> tcSigPolyId sig -- Signature
+ Nothing -> mkLocalId 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 in
- tcImprove (lie_avail `plusLIE` lie_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
+ tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
in
- -- SIMPLIFY THE LIE
- tcExtendGlobalTyVars tyvars_not_to_gen (
- let ips = getIPsOfLIE lie_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 ->
+ -- GENERALISE
+ tcAddSrcLoc (minimum (map getSrcLoc binder_names)) $
+ tcAddErrCtxt (genCtxt binder_names) $
+ generalise binder_names mbind tau_tvs lie_req tc_ty_sigs
+ `thenTc` \ (tc_tyvars_to_gen, lie_free, dict_binds, dict_ids) ->
+
+
+ -- 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.
+ mapNF_Tc zonkTcTyVarToTyVar tc_tyvars_to_gen `thenNF_Tc` \ 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
+ mapNF_Tc zonkId dict_ids `thenNF_Tc` \ zonked_dict_ids ->
+ mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids ->
+
+ -- BUILD THE POLYMORPHIC RESULT IDs
let
exports = zipWith mk_export binder_names zonked_mono_ids
- dict_tys = map idType dicts_bound
+ poly_ids = [poly_id | (_, poly_id, _) <- exports]
+ dict_tys = map idType zonked_dict_ids
- 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
+ inlines = mkNameSet [name | InlineSig True name _ loc <- inline_sigs]
+ -- Any INLINE sig (regardless of phase control)
+ -- makes the RHS look small
+ inline_phases = listToFM [(name, phase) | InlineSig _ name phase _ <- inline_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,
- attachNoInlinePrag no_inlines poly_id,
+ attachInlinePhase inline_phases poly_id,
zonked_mono_id)
where
(tyvars, poly_id) =
case maybeSig tc_ty_sigs binder_name of
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _ _ _) ->
+ Just (TySigInfo sig_poly_id sig_tyvars _ _ _ _ _) ->
(sig_tyvars, sig_poly_id)
- Nothing -> (real_tyvars_to_gen_list, new_poly_id)
+ Nothing -> (real_tyvars_to_gen, 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)
+ 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.
-
- pat_binders :: [Name]
- pat_binders = map fst $ bagToList $ 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
+ traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
+ exports, map idType poly_ids)) `thenTc_`
+
+ -- 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 `thenTc_`
+
+ returnTc (
+ AbsBinds [] [] exports inlines mbind',
+ lie_req, -- Do not generate even any x=y bindings
+ poly_ids
+ )
+
+ else -- The normal case
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]
+ AbsBinds real_tyvars_to_gen
+ zonked_dict_ids
+ exports
+ inlines
+ (dict_binds `andMonoBinds` mbind'),
+ lie_free, 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
+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.
+ -- That's why we just use an ASSERT here.
+
+ checkTc (isNotTopLevel top_lvl)
+ (unliftedBindErr "Top-level" mbind) `thenTc_`
+ checkTc (isNonRec is_rec)
+ (unliftedBindErr "Recursive" mbind) `thenTc_`
+ checkTc (single_bind mbind)
+ (unliftedBindErr "Multiple" mbind) `thenTc_`
+ checkTc (null real_tyvars_to_gen)
+ (unliftedBindErr "Polymorphic" mbind)
+
+ where
+ single_bind (PatMonoBind _ _ _) = True
+ single_bind (FunMonoBind _ _ _ _) = True
+ single_bind other = False
\end{code}
+
Polymorphic recursion
~~~~~~~~~~~~~~~~~~~~~
The game plan for polymorphic recursion in the code above is
%* *
%************************************************************************
+\begin{code}
+generalise binder_names mbind tau_tvs lie_req sigs =
+
+ -- check for -fno-monomorphism-restriction
+ doptsTc Opt_NoMonomorphismRestriction `thenTc` \ 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) `thenTc_`
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ tcSimplifyRestricted doc tau_tvs lie_req `thenTc` \ (qtvs, lie_free, binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars qtvs sigs `thenTc` \ final_qtvs ->
+
+ returnTc (final_qtvs, lie_free, 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 `thenTc` \ (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 `thenTc` \ (forall_tvs, lie_free, dict_binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars forall_tvs sigs `thenTc` \ final_qtvs ->
+
+ returnTc (final_qtvs, lie_free, dict_binds, sig_dicts)
+
+ where
+ tysig_names = map (idName . tcSigPolyId) sigs
+ is_mono_sig (TySigInfo _ _ theta _ _ _ _) = null theta
+
+ doc = ptext SLIT("type signature(s) for") <+> pprBinders binder_names
+
+-----------------------
+ -- 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 id1 sig_tvs theta1 _ _ _ src_loc : other_sigs)
+ = tcAddSrcLoc src_loc $
+ mapTc_ check_one other_sigs `thenTc_`
+ if null theta1 then
+ returnTc ([], []) -- Non-overloaded type signatures
+ else
+ newDicts SignatureOrigin theta1 `thenNF_Tc` \ 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
+ returnTc (sig_avails, map instToId sig_dicts)
+ where
+ sig1_dict_tys = map mkPredTy theta1
+ sig_meths = concat [insts | TySigInfo _ _ _ _ _ insts _ <- sigs]
+
+ check_one sig@(TySigInfo id _ theta _ _ _ _)
+ = tcAddErrCtxt (sigContextsCtxt id1 id) $
+ checkTc (equalLength theta theta1) sigContextsErr `thenTc_`
+ unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
+
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs
+ = mapTc check_one sigs `thenTc` \ 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 = foldr (unionVarSet . mkVarSet) emptyVarSet sig_tvs_s
+ all_tvs = mkVarSet qtvs `unionVarSet` sig_tvs
+ in
+ returnTc (varSetElems all_tvs)
+ where
+ check_one (TySigInfo id sig_tyvars sig_theta sig_tau _ _ src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (ptext SLIT("When checking the type signature for")
+ <+> quotes (ppr id)) $
+ tcAddErrCtxtM (sigCtxt id sig_tyvars sig_theta sig_tau) $
+ checkSigTyVarsWrt (idFreeTyVars id) sig_tyvars
+\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
- in
- if is_unrestricted
- then
- let fds = getAllFunDepsOfLIE lie in
- zonkFunDeps fds `thenNF_Tc` \ fds' ->
- let tvFundep = tyVarFunDep fds'
- extended_tyvars = oclose tvFundep body_tyvars in
- -- pprTrace "gTVTG" (ppr (lie, body_tyvars, extended_tyvars)) $
- 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 sigs (PatMonoBind other _ _) = False
isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
-isUnRestrictedGroup sigs (FunMonoBind v _ matches _) = any isUnRestrictedMatch matches ||
+isUnRestrictedGroup sigs (FunMonoBind v _ matches _) = 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
+isUnRestrictedMatch (Match [] _ _ : _) = False -- No args => like a pattern binding
+isUnRestrictedMatch other = True -- Some args => a function binding
\end{code}
tcMonoBinds :: RenamedMonoBinds
-> [TcSigInfo]
-> RecFlag
- -> TcM s (TcMonoBinds,
+ -> TcM (TcMonoBinds,
LIE, -- LIE required
[Name], -- Bound names
- [TcId]) -- Corresponding monomorphic bound things
+ [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
- tv_list = bagToList tvs
id_list = bagToList ids
(names, mono_ids) = unzip id_list
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)
+ Nothing -> (name, mono_id)
+ Just sig -> (idName poly_id, poly_id)
+ where
+ poly_id = tcSigPolyId sig
tc_mb_pats EmptyMonoBinds
= returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
lie_avail1 `plusLIE` lie_avail2)
tc_mb_pats (FunMonoBind name inf matches locn)
- = new_lhs_ty `thenNF_Tc` \ bndr_ty ->
- tc_pat_bndr name bndr_ty `thenTc` \ bndr_id ->
+ = (case maybeSig tc_ty_sigs name of
+ Just sig -> returnNF_Tc (tcSigMonoId sig)
+ Nothing -> newLocalName name `thenNF_Tc` \ bndr_name ->
+ newTyVarTy openTypeKind `thenNF_Tc` \ bndr_ty ->
+ -- NB: not a 'hole' tyvar; since there is no type
+ -- signature, we revert to ordinary H-M typechecking
+ -- which means the variable gets an inferred tau-type
+ returnNF_Tc (mkLocalId bndr_name bndr_ty)
+ ) `thenNF_Tc` \ bndr_id ->
let
+ bndr_ty = idType bndr_id
complete_it xve = tcAddSrcLoc locn $
- tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) ->
+ 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 $
- new_lhs_ty `thenNF_Tc` \ pat_ty ->
+ newHoleTyVarTy `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:
+ -- 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
- -- 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
+ -- The type variables are brought into scope in tc_binds_and_then,
+ -- so we don't have to do anything here.
+
tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
+ readHoleResult pat_ty `thenTc` \ pat_ty' ->
let
complete_it xve = tcAddSrcLoc locn $
tcAddErrCtxt (patMonoBindsCtxt bind) $
- tcExtendLocalValEnv xve $
- tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) ->
+ tcExtendLocalValEnv2 xve $
+ tcGRHSs PatBindRhs grhss pat_ty' `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
- new_lhs_ty = case is_rec of
- Recursive -> newTyVarTy boxedTypeKind -- Recursive, so no unboxed types
- NonRecursive -> newTyVarTy_OpenKind -- 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 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 ioTyCon_NAME `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 [inst | TySigInfo _ _ _ _ _ _ inst _ <- 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 == main_NAME = Just m
- | otherwise = go ns ms
+ -- 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_mb_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 `thenNF_Tc` \ bndr_name ->
+ tcMonoPatBndr bndr_name pat_ty
+
+ Just sig -> tcAddSrcLoc (getSrcLoc name) $
+ tcSubPat (idType mono_id) pat_ty `thenTc` \ (co_fn, lie) ->
+ returnTc (co_fn, lie, mono_id)
+ where
+ mono_id = tcSigMonoId sig
\end{code}
{-# SPECIALISE (f::<type) = g #-}
\begin{code}
-tcSpecSigs :: [RenamedSig] -> TcM s (TcMonoBinds, LIE)
+tcSpecSigs :: [RenamedSig] -> TcM (TcMonoBinds, LIE)
tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
= -- SPECIALISE f :: forall b. theta => tau = g
tcAddSrcLoc src_loc $
tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
- tcHsSigType poly_ty `thenTc` \ sig_ty ->
+ tcHsSigType (FunSigCtxt name) poly_ty `thenTc` \ 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) ->
-- Squeeze out any Methods (see comments with tcSimplifyToDicts)
- tcSimplifyToDicts spec_lie `thenTc` \ (spec_lie1, spec_binds) ->
+ tcSimplifyToDicts spec_lie `thenTc` \ (spec_dicts, 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 `thenNF_Tc` \ spec_name ->
+ let
+ spec_bind = VarMonoBind (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)
+ returnTc (binds_rest `andMonoBinds` spec_bind,
+ lie_rest `plusLIE` mkLIE spec_dicts)
tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE)
nest 4 (ppr v <+> dcolon <+> ppr ty)]
-----------------------------------------------
-notAsPolyAsSigErr sig_tau mono_tyvars
- = hang (ptext SLIT("A type signature is more polymorphic than the inferred type"))
- 4 (vcat [text "Can't for-all the type variable(s)" <+>
- pprQuotedList mono_tyvars,
- text "in the type" <+> quotes (ppr sig_tau)
- ])
-
------------------------------------------------
-badMatchErr sig_ty inferred_ty
- = hang (ptext SLIT("Type signature doesn't match inferred type"))
- 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sig_ty),
- hang (ptext SLIT("Inferred :")) 4 (ppr inferred_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")
+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
- | getName id == main_NAME = 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.
-
-mainTyCheckCtxt
- = hsep [ptext SLIT("When checking that"), quotes (ppr main_NAME),
- ptext SLIT("has the required type")]
+ = 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")]
-----------------------------------------------
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
+
+-- 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}