\section[TcBinds]{TcBinds}
\begin{code}
-#include "HsVersions.h"
+module TcBinds ( tcBindsAndThen, tcTopBindsAndThen, bindInstsOfLocalFuns,
+ tcPragmaSigs, checkSigTyVars, tcBindWithSigs,
+ sigCtxt, TcSigInfo(..) ) where
-module TcBinds ( tcBindsAndThen, tcPragmaSigs, checkSigTyVars, tcBindWithSigs, TcSigInfo(..) ) where
+#include "HsVersions.h"
-IMP_Ubiq()
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ <= 201
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-#else
import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
-#endif
-
-import HsSyn ( HsBinds(..), Sig(..), MonoBinds(..),
- Match, HsType, InPat(..), OutPat(..), HsExpr(..),
- SYN_IE(RecFlag), nonRecursive,
- GRHSsAndBinds, ArithSeqInfo, HsLit, Fake, Stmt, DoOrListComp, Fixity,
- collectMonoBinders )
-import RnHsSyn ( SYN_IE(RenamedHsBinds), RenamedSig(..),
- SYN_IE(RenamedMonoBinds)
+import {-# SOURCE #-} TcExpr ( tcExpr )
+
+import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..),
+ collectMonoBinders, andMonoBinds
)
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcMonoBinds),
- SYN_IE(TcExpr),
+import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
+import TcHsSyn ( TcHsBinds, TcMonoBinds,
+ TcIdOcc(..), TcIdBndr,
tcIdType
)
import TcMonad
-import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..),
- newDicts, tyVarsOfInst, instToId
+import Inst ( Inst, LIE, emptyLIE, plusLIE, plusLIEs, InstOrigin(..),
+ newDicts, tyVarsOfInst, instToId, newMethodWithGivenTy,
+ zonkInst, pprInsts
)
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds,
+import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK,
+ newLocalId, newSpecPragmaId,
tcGetGlobalTyVars, tcExtendGlobalTyVars
)
-import SpecEnv ( SpecEnv )
import TcMatches ( tcMatchesFun )
import TcSimplify ( tcSimplify, tcSimplifyAndCheck )
import TcMonoType ( tcHsType )
import TcPat ( tcPat )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( TcIdOcc(..), SYN_IE(TcIdBndr),
- SYN_IE(TcType), SYN_IE(TcThetaType), SYN_IE(TcTauType),
- SYN_IE(TcTyVarSet), SYN_IE(TcTyVar),
- newTyVarTy, zonkTcType, zonkSigTyVar,
- newTcTyVar, tcInstSigType, newTyVarTys
+import TcType ( TcType, TcThetaType, TcTauType,
+ TcTyVarSet, TcTyVar,
+ newTyVarTy, newTcTyVar, tcInstSigType, tcInstSigTcType,
+ zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVar
)
import Unify ( unifyTauTy, unifyTauTyLists )
import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind )
-import Id ( GenId, idType, mkUserLocal, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( maybeToBool, assocMaybe, catMaybes )
+import MkId ( mkUserId )
+import Id ( idType, idName, idInfo, replaceIdInfo )
+import IdInfo ( IdInfo, noIdInfo, setInlinePragInfo, InlinePragInfo(..) )
+import Maybes ( maybeToBool, assocMaybe )
import Name ( getOccName, getSrcLoc, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Pretty
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes, eqSimpleTheta,
- mkSigmaTy, splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy,
- splitRhoTy, mkForAllTy, splitForAllTy )
-import TyVar ( GenTyVar, SYN_IE(TyVar), tyVarKind, mkTyVarSet, minusTyVarSet, emptyTyVarSet,
- elementOfTyVarSet, unionTyVarSets, tyVarSetToList )
-import Bag ( bagToList, foldrBag, isEmptyBag )
-import Util ( isIn, zipEqual, zipWithEqual, zipWith3Equal, hasNoDups, assoc,
- assertPanic, panic, pprTrace )
-import PprType ( GenClass, GenType, GenTyVar )
+import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes,
+ splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy,
+ splitRhoTy, mkForAllTy, splitForAllTys
+ )
+import TyVar ( TyVar, tyVarKind, mkTyVarSet, minusTyVarSet, emptyTyVarSet,
+ elementOfTyVarSet, unionTyVarSets, tyVarSetToList
+ )
+import Bag ( bagToList, foldrBag, )
+import Util ( isIn, hasNoDups, assoc )
import Unique ( Unique )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
import SrcLoc ( SrcLoc )
-
-import Outputable --( interppSP, interpp'SP )
-
-
+import Outputable
\end{code}
dictionaries, which we resolve at the module level.
\begin{code}
-tcBindsAndThen
- :: (RecFlag -> TcMonoBinds s -> thing -> thing) -- Combinator
+tcTopBindsAndThen, tcBindsAndThen
+ :: (RecFlag -> TcMonoBinds s -> this -> that) -- Combinator
-> RenamedHsBinds
- -> TcM s (thing, LIE s)
- -> TcM s (thing, LIE s)
-
-tcBindsAndThen combiner EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie) ->
- returnTc (combiner nonRecursive EmptyMonoBinds thing, lie)
-
-tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
-
-tcBindsAndThen combiner (MonoBind bind sigs is_rec) do_next
- = fixTc (\ ~(prag_info_fn, _) ->
- -- This is the usual prag_info fix; the PragmaInfo field of an Id
- -- is not inspected till ages later in the compiler, so there
- -- should be no black-hole problems here.
-
- -- TYPECHECK THE SIGNATURES
- mapTc (tcTySig prag_info_fn) ty_sigs `thenTc` \ tc_ty_sigs ->
+ -> TcM s (this, LIE s)
+ -> TcM s (that, LIE s)
- tcBindWithSigs binder_names bind
- tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+tcTopBindsAndThen = tc_binds_and_then TopLevel
+tcBindsAndThen = tc_binds_and_then NotTopLevel
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv binder_names poly_ids $
-
- -- Build bindings and IdInfos corresponding to user pragmas
- tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+tc_binds_and_then top_lvl combiner binds do_next
+ = tcBinds top_lvl binds `thenTc` \ (mbinds1, binds_lie, env, ids) ->
+ tcSetEnv env $
-- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie) ->
+ do_next `thenTc` \ (thing, thing_lie) ->
-- Create specialisations of functions bound here
- bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
- poly_ids `thenTc` \ (lie2, inst_mbinds) ->
+ -- Nota Bene: we glom the bindings all together in a single
+ -- recursive group ("recursive" passed to combiner, below)
+ -- so that we can do thsi bindInsts thing once for all the bindings
+ -- and the thing inside. This saves a quadratic-cost algorithm
+ -- when there's a long sequence of bindings.
+ bindInstsOfLocalFuns (binds_lie `plusLIE` thing_lie) ids `thenTc` \ (final_lie, mbinds2) ->
-- All done
let
- final_lie = lie2 `plusLIE` poly_lie
- final_thing = combiner is_rec poly_binds $
- combiner nonRecursive inst_mbinds $
- combiner nonRecursive prag_binds
- thing
+ final_mbinds = mbinds1 `AndMonoBinds` mbinds2
in
- returnTc (prag_info_fn, (final_thing, final_lie))
- ) `thenTc` \ (_, result) ->
+ returnTc (combiner Recursive final_mbinds thing, final_lie)
+
+tcBinds :: TopLevelFlag
+ -> RenamedHsBinds
+ -> TcM s (TcMonoBinds s, LIE s, TcEnv s, [TcIdBndr s])
+ -- The envt is the envt with binders in scope
+ -- The binders are those bound by this group of bindings
+
+tcBinds top_lvl EmptyBinds
+ = tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (EmptyMonoBinds, emptyLIE, env, [])
+
+ -- Short-cut for the rather common case of an empty bunch of bindings
+tcBinds top_lvl (MonoBind EmptyMonoBinds sigs is_rec)
+ = tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (EmptyMonoBinds, emptyLIE, env, [])
+
+tcBinds top_lvl (ThenBinds binds1 binds2)
+ = tcBinds top_lvl binds1 `thenTc` \ (mbinds1, lie1, env1, ids1) ->
+ tcSetEnv env1 $
+ tcBinds top_lvl binds2 `thenTc` \ (mbinds2, lie2, env2, ids2) ->
+ returnTc (mbinds1 `AndMonoBinds` mbinds2, lie1 `plusLIE` lie2, env2, ids1++ids2)
+
+tcBinds top_lvl (MonoBind bind sigs is_rec)
+ = fixTc (\ ~(prag_info_fn, _) ->
+ -- This is the usual prag_info fix; the PragmaInfo field of an Id
+ -- is not inspected till ages later in the compiler, so there
+ -- should be no black-hole problems here.
+
+ -- TYPECHECK THE SIGNATURES
+ mapTc tcTySig ty_sigs `thenTc` \ tc_ty_sigs ->
+
+ tcBindWithSigs top_lvl binder_names bind
+ tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+
+ -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv binder_names poly_ids $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+
+ -- Catch the environment and return
+ tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (prag_info_fn, (poly_binds `AndMonoBinds` prag_binds,
+ poly_lie `plusLIE` prag_lie,
+ env, poly_ids)
+ ) ) `thenTc` \ (_, result) ->
returnTc result
where
binder_names = map fst (bagToList (collectMonoBinders bind))
\begin{code}
tcBindWithSigs
- :: [Name]
+ :: TopLevelFlag
+ -> [Name]
-> RenamedMonoBinds
-> [TcSigInfo s]
-> RecFlag
- -> (Name -> PragmaInfo)
+ -> (Name -> IdInfo)
-> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s])
-tcBindWithSigs binder_names mbind tc_ty_sigs is_rec prag_info_fn
+tcBindWithSigs top_lvl binder_names mbind tc_ty_sigs is_rec prag_info_fn
= recoverTc (
-- If typechecking the binds fails, then return with each
-- signature-less binder given type (forall a.a), to minimise subsequent
poly_ids = map mk_dummy binder_names
mk_dummy name = case maybeSig tc_ty_sigs name of
Just (TySigInfo _ poly_id _ _ _ _) -> poly_id -- Signature
- Nothing -> mkUserId name forall_a_a NoPragmaInfo -- No signature
+ Nothing -> mkUserId name forall_a_a -- No signature
in
returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
) $
-- Create a new identifier for each binder, with each being given
-- a fresh unique, and a type-variable type.
- tcGetUniques no_of_binders `thenNF_Tc` \ uniqs ->
- mapNF_Tc mk_mono_id_ty binder_names `thenNF_Tc` \ mono_id_tys ->
+ -- For "mono_lies" see comments about polymorphic recursion at the
+ -- end of the function.
+ mapAndUnzipNF_Tc mk_mono_id binder_names `thenNF_Tc` \ (mono_lies, mono_ids) ->
let
- mono_ids = zipWith3Equal "tcBindAndSigs" mk_id binder_names uniqs mono_id_tys
- mk_id name uniq ty = mkUserLocal (getOccName name) uniq ty (getSrcLoc name)
+ mono_lie = plusLIEs mono_lies
+ mono_id_tys = map idType mono_ids
in
-- TYPECHECK THE BINDINGS
-- The tyvars_not_to_gen are free in the environment, and hence
-- candidates for generalisation, but sometimes the monomorphism
-- restriction means we can't generalise them nevertheless
- getTyVarsToGen is_unrestricted mono_id_tys lie `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
+ getTyVarsToGen is_unrestricted mono_id_tys lie `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
-- DEAL WITH TYPE VARIABLE KINDS
- mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
+ -- **** This step can do unification => keep other zonking after this ****
+ mapTc defaultUncommittedTyVar (tyVarSetToList tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
let
real_tyvars_to_gen = mkTyVarSet real_tyvars_to_gen_list
- -- It's important that the final list (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
+ -- 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
- --
- -- **** This step can do unification => keep other zonking after this ****
in
-- SIMPLIFY THE LIE
- tcExtendGlobalTyVars tyvars_not_to_gen (
+ tcExtendGlobalTyVars (tyVarSetToList tyvars_not_to_gen) (
if null tc_ty_sigs then
-- No signatures, so just simplify the lie
- tcSimplify real_tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) ->
+ -- NB: no signatures => no polymorphic recursion, so no
+ -- need to use mono_lies (which will be empty anyway)
+ tcSimplify (text "tcBinds1" <+> ppr binder_names)
+ top_lvl real_tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) ->
returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
else
- zonk_theta sig_theta `thenNF_Tc` \ sig_theta' ->
+ 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 mono_lie
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ givens = dicts_sig `plusLIE` mono_lie
+ in
+
-- Check that the needed dicts can be expressed in
-- terms of the signature ones
- tcAddErrCtxt (sigsCtxt tysig_names) $
- tcSimplifyAndCheck real_tyvars_to_gen dicts_sig lie `thenTc` \ (lie_free, dict_binds) ->
+ tcAddErrCtxt (bindSigsCtxt tysig_names) $
+ tcSimplifyAndCheck
+ (ptext SLIT("type signature for") <+>
+ hsep (punctuate comma (map (quotes . ppr) binder_names)))
+ real_tyvars_to_gen givens lie `thenTc` \ (lie_free, dict_binds) ->
+
returnTc (lie_free, dict_binds, dict_ids)
) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
-- That's why we just use an ASSERT here.
-- BUILD THE POLYMORPHIC RESULT IDs
- mapNF_Tc zonkTcType mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
+ zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
let
exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types
dict_tys = map tcIdType dicts_bound
mk_export binder_name mono_id zonked_mono_id_ty
- | maybeToBool maybe_sig = (sig_tyvars, TcId sig_poly_id, TcId mono_id)
- | otherwise = (real_tyvars_to_gen_list, TcId poly_id, TcId mono_id)
+ = (tyvars, TcId (replaceIdInfo poly_id (prag_info_fn binder_name)), TcId mono_id)
where
- maybe_sig = maybeSig tc_ty_sigs binder_name
- Just (TySigInfo _ sig_poly_id sig_tyvars _ _ _) = maybe_sig
- poly_id = mkUserId binder_name poly_ty (prag_info_fn binder_name)
- poly_ty = mkForAllTys real_tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty
+ (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 = mkUserId binder_name poly_ty
+ poly_ty = mkForAllTys real_tyvars_to_gen_list $ mkFunTys dict_tys $ zonked_mono_id_ty
-- It's important to build a fully-zonked poly_ty, because
-- we'll slurp out its free type variables when extending the
-- local environment (tcExtendLocalValEnv); if it's not zonked
where
no_of_binders = length binder_names
- mk_mono_id_ty binder_name = case maybeSig tc_ty_sigs binder_name of
- Just (TySigInfo name _ _ _ tau_ty _) -> returnNF_Tc tau_ty -- There's a signature
- otherwise -> newTyVarTy kind -- No signature
+ mk_mono_id binder_name
+ | theres_a_signature -- There's a signature; and it's overloaded,
+ && not (null sig_theta) -- so make a Method
+ = tcAddSrcLoc sig_loc $
+ newMethodWithGivenTy SignatureOrigin
+ (TcId poly_id) (mkTyVarTys sig_tyvars)
+ sig_theta sig_tau `thenNF_Tc` \ (mono_lie, TcId mono_id) ->
+ -- A bit turgid to have to strip the TcId
+ returnNF_Tc (mono_lie, mono_id)
+
+ | otherwise -- No signature or not overloaded;
+ = tcAddSrcLoc (getSrcLoc binder_name) $
+ (if theres_a_signature then
+ returnNF_Tc sig_tau -- Non-overloaded signature; use its type
+ else
+ newTyVarTy kind -- No signature; use a new type variable
+ ) `thenNF_Tc` \ mono_id_ty ->
+
+ newLocalId (getOccName binder_name) mono_id_ty `thenNF_Tc` \ mono_id ->
+ returnNF_Tc (emptyLIE, mono_id)
+ where
+ maybe_sig = maybeSig tc_ty_sigs binder_name
+ theres_a_signature = maybeToBool maybe_sig
+ Just (TySigInfo name poly_id sig_tyvars sig_theta sig_tau sig_loc) = maybe_sig
tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
is_unrestricted = isUnRestrictedGroup tysig_names mbind
- kind | is_rec = mkBoxedTypeKind -- Recursive, so no unboxed types
- | otherwise = mkTypeKind -- Non-recursive, so we permit unboxed types
-
-zonk_theta theta = mapNF_Tc zonk theta
- where
- zonk (c,t) = zonkTcType t `thenNF_Tc` \ t' ->
- returnNF_Tc (c,t')
+ kind = case is_rec of
+ Recursive -> mkBoxedTypeKind -- Recursive, so no unboxed types
+ NonRecursive -> mkTypeKind -- Non-recursive, so we permit unboxed types
\end{code}
-@getImplicitStuffToGen@ decides what type variables generalise over.
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
+
+ * Bind any variable for which we have a type signature
+ to an Id with a polymorphic type. Then when type-checking
+ the RHSs we'll make a full polymorphic call.
+
+This fine, but if you aren't a bit careful you end up with a horrendous
+amount of partial application and (worse) a huge space leak. For example:
+
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
+
+If we don't take care, after typechecking we get
+
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
+
+Notice the the stupid construction of (f a d), which is of course
+identical to the function we're executing. In this case, the
+polymorphic recursion ins't being used (but that's a very common case).
+
+This can lead to a massive space leak, from the following top-level defn:
+
+ ff :: [Int] -> [Int]
+ ff = f dEqInt
+
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
+
+Solution: when typechecking the RHSs we always have in hand the
+*monomorphic* Ids for each binding. So we just need to make sure that
+if (Method f a d) shows up in the constraints emerging from (...f...)
+we just use the monomorphic Id. We achieve this by adding monomorphic Ids
+to the "givens" when simplifying constraints. Thats' what the "mono_lies"
+is doing.
+
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
+
+@getTyVarsToGen@ decides what type variables generalise over.
For a "restricted group" -- see the monomorphism restriction
for a definition -- we bind no dictionaries, and
\begin{code}
getTyVarsToGen is_unrestricted mono_id_tys lie
- = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
- mapNF_Tc zonkTcType mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys ->
+ = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
+ zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys ->
let
tyvars_to_gen = tyVarsOfTypes zonked_mono_id_tys `minusTyVarSet` free_tyvars
in
if is_unrestricted
then
- returnTc (emptyTyVarSet, tyvars_to_gen)
+ returnNF_Tc (emptyTyVarSet, tyvars_to_gen)
else
- tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
+ -- This recover and discard-errs is to avoid duplicate error
+ -- messages; this, after all, is an "extra" call to tcSimplify
+ recoverNF_Tc (returnNF_Tc (emptyTyVarSet, tyvars_to_gen)) $
+ discardErrsTc $
+
+ tcSimplify (text "getTVG") NotTopLevel tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
let
-- ASSERT: dicts_sig is already zonked!
constrained_tyvars = foldrBag (unionTyVarSets . tyVarsOfInst) emptyTyVarSet constrained_dicts
\begin{code}
-tcTySig :: (Name -> PragmaInfo)
- -> RenamedSig
+tcTySig :: RenamedSig
-> TcM s (TcSigInfo s)
-tcTySig prag_info_fn (Sig v ty src_loc)
+tcTySig (Sig v ty src_loc)
= tcAddSrcLoc src_loc $
tcHsType ty `thenTc` \ sigma_ty ->
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' ->
+
+ -- Convert from Type to TcType
+ tcInstSigType sigma_ty `thenNF_Tc` \ sigma_tc_ty ->
+ let
+ poly_id = mkUserId v sigma_tc_ty
+ in
+ -- Instantiate this type
+ -- It's important to do this even though in the error-free case
+ -- we could just split the sigma_tc_ty (since the tyvars don't
+ -- unified with anything). But in the case of an error, when
+ -- the tyvars *do* get unified with something, we want to carry on
+ -- typechecking the rest of the program with the function bound
+ -- to a pristine type, namely sigma_tc_ty
+ tcInstSigTcType sigma_tc_ty `thenNF_Tc` \ (tyvars, rho) ->
let
- poly_id = mkUserId v sigma_ty' (prag_info_fn v)
- (tyvars', theta', tau') = splitSigmaTy sigma_ty'
+ (theta, tau) = splitRhoTy rho
-- This splitSigmaTy tries hard to make sure that tau' is a type synonym
-- wherever possible, which can improve interface files.
in
- returnTc (TySigInfo v poly_id tyvars' theta' tau' src_loc)
+ returnTc (TySigInfo v poly_id tyvars theta tau src_loc)
\end{code}
@checkSigMatch@ does the next step in checking signature matching.
tcAddErrCtxt (sigCtxt id) $
checkSigTyVars sig_tyvars sig_tau
- mk_dict_tys theta = [mkDictTy c t | (c,t) <- theta]
+ mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta]
\end{code}
eg matching signature [(a,b)] against inferred type [(p,p)]
[then a and b will be unified together]
-BUT ACTUALLY THESE FIRST TWO ARE FORCED BY USING DontBind TYVARS
-
(c) not mentioned in the environment
eg the signature for f in this:
Before doing this, the substitution is applied to the signature type variable.
+We used to have the notion of a "DontBind" type variable, which would
+only be bound to itself or nothing. Then points (a) and (b) were
+self-checking. But it gave rise to bogus consequential error messages.
+For example:
+
+ f = (*) -- Monomorphic
+
+ g :: Num a => a -> a
+ g x = f x x
+
+Here, we get a complaint when checking the type signature for g,
+that g isn't polymorphic enough; but then we get another one when
+dealing with the (Num x) context arising from f's definition;
+we try to unify x with Int (to default it), but find that x has already
+been unified with the DontBind variable "a" from g's signature.
+This is really a problem with side-effecting unification; we'd like to
+undo g's effects when its type signature fails, but unification is done
+by side effect, so we can't (easily).
+
+So we revert to ordinary type variables for signatures, and try to
+give a helpful message in checkSigTyVars.
+
\begin{code}
checkSigTyVars :: [TcTyVar s] -- The original signature type variables
-> TcType s -- signature type (for err msg)
- -> TcM s ()
+ -> TcM s [TcTyVar s] -- Zonked signature type variables
checkSigTyVars sig_tyvars sig_tau
- = -- Several type signatures in the same bindings group can
- -- cause the signature type variable from the different
- -- signatures to be unified. So we need to zonk them.
- mapNF_Tc zonkSigTyVar sig_tyvars `thenNF_Tc` \ sig_tyvars' ->
-
- -- Point (a) is forced by the fact that they are signature type
- -- variables, so the unifer won't bind them to a type.
+ = mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys ->
+ let
+ sig_tyvars' = map (getTyVar "checkSigTyVars") sig_tys
+ in
- -- Check point (b)
- checkTcM (hasNoDups sig_tyvars')
+ -- Check points (a) and (b)
+ checkTcM (all isTyVarTy sig_tys && hasNoDups sig_tyvars')
(zonkTcType sig_tau `thenNF_Tc` \ sig_tau' ->
- failTc (badMatchErr sig_tau sig_tau')
+ failWithTc (badMatchErr sig_tau sig_tau')
) `thenTc_`
-- Check point (c)
-- 1-1 with sig_tyvars, so we can just map back.
tcGetGlobalTyVars `thenNF_Tc` \ globals ->
let
--- mono_tyvars = [sig_tv | (sig_tv, sig_tv') <- sig_tyvars `zip` sig_tyvars',
--- sig_tv' `elementOfTyVarSet` globals
--- ]
mono_tyvars' = [sig_tv' | sig_tv' <- sig_tyvars',
sig_tv' `elementOfTyVarSet` globals]
+
+ mono_tyvars = map (assoc "checkSigTyVars" (sig_tyvars' `zip` sig_tyvars)) mono_tyvars'
in
checkTcM (null mono_tyvars')
- (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' ->
- failTc (notAsPolyAsSigErr sig_tau' mono_tyvars'))
+ (failWithTc (notAsPolyAsSigErr sig_tau mono_tyvars)) `thenTc_`
+
+ returnTc sig_tyvars'
\end{code}
moving them into place as is done for type signatures.
\begin{code}
-tcPragmaSigs :: [RenamedSig] -- The pragma signatures
- -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
+tcPragmaSigs :: [RenamedSig] -- The pragma signatures
+ -> TcM s (Name -> IdInfo, -- Maps name to the appropriate IdInfo
TcMonoBinds s,
LIE s)
--- For now we just deal with INLINE pragmas
-tcPragmaSigs sigs = returnTc (prag_fn, EmptyMonoBinds, emptyLIE )
- where
- prag_fn name | any has_inline sigs = IWantToBeINLINEd
- | otherwise = NoPragmaInfo
- where
- has_inline (InlineSig n _) = (n == name)
- has_inline other = False
-
-
-{-
tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
+ = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (maybe_info_modifiers, binds, lies) ->
let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
+ prag_fn name = foldr ($) noIdInfo [f | Just (n,f) <- maybe_info_modifiers, n==name]
in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
-
-\begin{code}
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addUnfoldInfo (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addUnfoldInfo (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
+ returnTc (prag_fn, andMonoBinds binds, plusLIEs lies)
\end{code}
The interesting case is for SPECIALISE pragmas. There are two forms.
a bit of overkill.
\begin{code}
+tcPragmaSig :: RenamedSig -> TcM s (Maybe (Name, IdInfo -> IdInfo), TcMonoBinds s, LIE s)
+tcPragmaSig (Sig _ _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+tcPragmaSig (SpecInstSig _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (InlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IWantToBeINLINEd), EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (NoInlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IDontWantToBeINLINEd), EmptyMonoBinds, emptyLIE)
+
tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
+ = -- SPECIALISE f :: forall b. theta => tau = g
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
tcHsType poly_ty `thenTc` \ sig_sigma ->
tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
- let
- (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
- origin = ValSpecOrigin name
- in
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (null sig_theta)
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
+ -- Check that f has a more general type, and build a RHS for
+ -- the spec-pragma-id at the same time
+ tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) ->
- -- Get and instantiate the type of the id mentioned
- tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
- tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty ->
- let
- (main_tyvars, main_rho) = splitForAllTy main_ty
- (main_theta,main_tau) = splitRhoTy main_rho
- main_arg_tys = mkTyVarTys main_tyvars
- in
+ case maybe_spec_name of
+ Nothing -> -- 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 ->
+ returnTc (Nothing, VarMonoBind (TcId spec_id) spec_expr, spec_lie)
- -- Check that the specialised type is indeed an instance of
- -- the type of the main function.
- unifyTauTy sig_tau main_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Check that the type variables of the polymorphic function are
- -- either left polymorphic, or instantiate to ground type.
- -- Also check that the overloaded type variables are instantiated to
- -- ground type; or equivalently that all dictionaries have ground type
- mapTc zonkTcType main_arg_tys `thenNF_Tc` \ main_arg_tys' ->
- zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' ->
- tcAddErrCtxt (specGroundnessCtxt main_arg_tys')
- (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_`
- tcAddErrCtxt (specContextGroundnessCtxt main_theta')
- (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_`
-
- -- Build the SpecPragmaId; it is the thing that makes sure we
- -- don't prematurely dead-code-eliminate the binding we are really interested in.
- newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_pragma_id ->
-
- -- Build a suitable binding; depending on whether we were given
- -- a value (Maybe Name) to be used as the specialisation.
- case using of
- Nothing -> -- No implementation function specified
-
- -- Make a Method inst for the occurrence of the overloaded function
- newMethodWithGivenTy (OccurrenceOf name)
- (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) ->
+ Just g_name -> -- Don't create a SpecPragmaId. Instead add some suitable IdIfo
+
+ panic "Can't handle SPECIALISE with a '= g' part"
- let
- pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs
- pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id))
- in
- returnTc (pseudo_bind, lie, \ info -> info)
+ {- Not yet. Because we're still in the TcType world we
+ can't really add to the SpecEnv of the Id. Instead we have to
+ record the information in a different sort of Sig, and add it to
+ the IdInfo after zonking.
- Just spec_name -> -- Use spec_name as the specialisation value ...
+ For now we just leave out this case
- -- Type check a simple occurrence of the specialised Id
- tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
+ -- Get the type of f, and find out what types
+ -- f has to be instantiated at to give the signature type
+ tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ f_id ->
+ tcInstSigTcType (idType f_id) `thenNF_Tc` \ (f_tyvars, f_rho) ->
- -- Check that it has the correct type, and doesn't constrain the
- -- signature variables at all
- unifyTauTy sig_tau spec_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
+ let
+ (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
+ (f_theta, f_tau) = splitRhoTy f_rho
+ sig_tyvar_set = mkTyVarSet sig_tyvars
+ in
+ unifyTauTy sig_tau f_tau `thenTc_`
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
+ tcPolyExpr str (HsVar g_name) (mkSigmaTy sig_tyvars f_theta sig_tau) `thenTc` \ (_, _,
+ -}
- let
- spec_rhs = mkHsTyLam sig_tyvars spec_body
- spec_binds = VarMonoBind local_spec_id spec_rhs
- `AndMonoBinds`
- VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
- spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
- in
- returnTc ((name, addSpecInfo spec_info), spec_binds, spec_lie)
--}
+tcPragmaSig other = pprTrace "tcPragmaSig: ignoring" (ppr other) $
+ returnTc (Nothing, EmptyMonoBinds, emptyLIE)
\end{code}
\begin{code}
-patMonoBindsCtxt bind sty
- = hang (ptext SLIT("In a pattern binding:")) 4 (ppr sty bind)
+patMonoBindsCtxt bind
+ = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
-----------------------------------------------
-valSpecSigCtxt v ty sty
- = hang (ptext SLIT("In a SPECIALIZE pragma for a value:"))
- 4 (sep [(<>) (ppr sty v) (ptext SLIT(" ::")),
- ppr sty ty])
-
-
+valSpecSigCtxt v ty
+ = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
+ nest 4 (ppr v <+> ptext SLIT(" ::") <+> ppr ty)]
-----------------------------------------------
-notAsPolyAsSigErr sig_tau mono_tyvars sty
+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)" <+> interpp'SP sty mono_tyvars,
- text "in the inferred type" <+> ppr sty sig_tau
+ 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 sty
+badMatchErr sig_ty inferred_ty
= hang (ptext SLIT("Type signature doesn't match inferred type"))
- 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sty sig_ty),
- hang (ptext SLIT("Inferred :")) 4 (ppr sty inferred_ty)
+ 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sig_ty),
+ hang (ptext SLIT("Inferred :")) 4 (ppr inferred_ty)
])
-----------------------------------------------
-sigCtxt id sty
- = sep [ptext SLIT("When checking signature for"), ppr sty id]
-sigsCtxt ids sty
- = sep [ptext SLIT("When checking signature(s) for:"), interpp'SP sty ids]
+sigCtxt id
+ = sep [ptext SLIT("When checking the type signature for"), quotes (ppr id)]
+
+bindSigsCtxt ids
+ = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
-----------------------------------------------
-sigContextsErr sty
+sigContextsErr
= ptext SLIT("Mismatched contexts")
-sigContextsCtxt s1 s2 sty
+sigContextsCtxt s1 s2
= hang (hsep [ptext SLIT("When matching the contexts of the signatures for"),
- ppr sty s1, ptext SLIT("and"), ppr sty s2])
+ quotes (ppr s1), ptext SLIT("and"), quotes (ppr s2)])
4 (ptext SLIT("(the signature contexts in a mutually recursive group should all be identical)"))
-----------------------------------------------
= panic "specGroundnessCtxt"
--------------------------------------------
-specContextGroundnessCtxt -- err_ctxt dicts sty
+specContextGroundnessCtxt -- err_ctxt dicts
= panic "specContextGroundnessCtxt"
{-
= hang (
- sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr sty name],
- hcat [ptext SLIT(" specialised to the type"), ppr sty spec_ty],
- pp_spec_id sty,
+ sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr name],
+ hcat [ptext SLIT(" specialised to the type"), ppr spec_ty],
+ pp_spec_id,
ptext SLIT("... not all overloaded type variables were instantiated"),
ptext SLIT("to ground types:")])
- 4 (vcat [hsep [ppr sty c, ppr sty t]
+ 4 (vcat [hsep [ppr c, ppr t]
| (c,t) <- map getDictClassAndType dicts])
where
(name, spec_ty, locn, pp_spec_id)
ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> empty)
ValSpecSpecIdCtxt n ty spec loc ->
(n, ty, loc,
- \ sty -> hsep [ptext SLIT("... type of explicit id"), ppr sty spec])
+ hsep [ptext SLIT("... type of explicit id"), ppr spec])
-}
\end{code}
-
-
-
-
projects / ghc-hetmet.git / blobdiff