%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
-#include "HsVersions.h"
+module TcBinds ( tcBindsAndThen, tcTopBinds, tcMonoBinds, tcSpecSigs ) where
-module TcBinds ( tcBindsAndThen, tcPragmaSigs ) where
+#include "HsVersions.h"
-IMP_Ubiq()
+import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcCheckSigma, tcCheckRho )
-import HsSyn ( HsBinds(..), Bind(..), Sig(..), MonoBinds(..),
- HsExpr, Match, HsType, InPat, OutPat(..),
- GRHSsAndBinds, ArithSeqInfo, HsLit, Fake,
- collectBinders )
-import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedBind), RenamedSig(..),
- SYN_IE(RenamedMonoBinds)
+import CmdLineOpts ( DynFlag(Opt_NoMonomorphismRestriction) )
+import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..),
+ Match(..), mkMonoBind,
+ collectMonoBinders, andMonoBinds,
+ collectSigTysFromMonoBinds
+ )
+import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
+import TcHsSyn ( TcHsBinds, TcMonoBinds, TcId, zonkId, mkHsLet )
+
+import TcRnMonad
+import Inst ( InstOrigin(..), newDicts, newIPDict, instToId )
+import TcEnv ( tcExtendLocalValEnv, tcExtendLocalValEnv2, newLocalName )
+import TcUnify ( Expected(..), newHole, unifyTauTyLists, checkSigTyVarsWrt, sigCtxt )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyRestricted,
+ tcSimplifyToDicts, tcSimplifyIPs )
+import TcMonoType ( tcHsSigType, UserTypeCtxt(..), TcSigInfo(..),
+ tcTySig, maybeSig, tcSigPolyId, tcSigMonoId, tcAddScopedTyVars
)
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcBind), SYN_IE(TcMonoBinds),
- TcIdOcc(..), SYN_IE(TcIdBndr) )
-
-import TcMonad
-import GenSpecEtc ( checkSigTyVars, genBinds, TcSigInfo(..) )
-import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..) )
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds )
-import SpecEnv ( SpecEnv )
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcHsType )
-import TcPat ( tcPat )
+import TcPat ( tcPat, tcSubPat, tcMonoPatBndr )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( newTcTyVar, tcInstSigType, newTyVarTys )
-import Unify ( unifyTauTy )
-
-import Kind ( mkBoxedTypeKind, mkTypeKind )
-import Id ( GenId, idType, mkUserLocal, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( assocMaybe, catMaybes )
-import Name ( pprNonSym, getOccName, getSrcLoc, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Pretty
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy,
- mkSigmaTy, splitSigmaTy,
- splitRhoTy, mkForAllTy, splitForAllTy )
-import Bag ( bagToList )
-import Util ( isIn, zipEqual, zipWith3Equal, panic )
+import TcMType ( newTyVar, newTyVarTy, zonkTcTyVarToTyVar )
+import TcType ( TcTyVar, mkTyVarTy, mkForAllTys, mkFunTys, tyVarsOfType,
+ mkPredTy, mkForAllTy, isUnLiftedType,
+ unliftedTypeKind, liftedTypeKind, openTypeKind, eqKind
+ )
+
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, mkSpecPragmaId, setInlinePragma )
+import Var ( idType, idName )
+import Name ( Name, getSrcLoc )
+import NameSet
+import Var ( tyVarKind )
+import VarSet
+import Bag
+import Util ( isIn, equalLength )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isRec,
+ isNotTopLevel, isAlwaysActive )
+import FiniteMap ( listToFM, lookupFM )
+import Outputable
\end{code}
+
%************************************************************************
%* *
\subsection{Type-checking bindings}
@tcBindsAndThen@ also takes a "combiner" which glues together the
bindings and the "thing" to make a new "thing".
-The real work is done by @tcBindAndThen@.
+The real work is done by @tcBindWithSigsAndThen@.
Recursive and non-recursive binds are handled in essentially the same
way: because of uniques there are no scoping issues left. The only
dictionaries, which we resolve at the module level.
\begin{code}
-tcBindsAndThen
- :: (TcHsBinds s -> thing -> thing) -- Combinator
- -> RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty)
- -> TcM s (thing, LIE s, thing_ty)
+tcTopBinds :: RenamedHsBinds -> TcM (TcMonoBinds, TcLclEnv)
+ -- Note: returning the TcLclEnv is more than we really
+ -- want. The bit we care about is the local bindings
+ -- and the free type variables thereof
+tcTopBinds binds
+ = tc_binds_and_then TopLevel glue binds $
+ getLclEnv `thenM` \ env ->
+ returnM (EmptyMonoBinds, env)
+ where
+ -- The top level bindings are flattened into a giant
+ -- implicitly-mutually-recursive MonoBinds
+ glue binds1 (binds2, env) = (flatten binds1 `AndMonoBinds` binds2, env)
+ flatten EmptyBinds = EmptyMonoBinds
+ flatten (b1 `ThenBinds` b2) = flatten b1 `AndMonoBinds` flatten b2
+ flatten (MonoBind b _ _) = b
+ -- Can't have a IPBinds at top level
-tcBindsAndThen combiner EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc (combiner EmptyBinds thing, lie, thing_ty)
-tcBindsAndThen combiner (SingleBind bind) do_next
- = tcBindAndThen combiner bind [] do_next
+tcBindsAndThen
+ :: (TcHsBinds -> thing -> thing) -- Combinator
+ -> RenamedHsBinds
+ -> TcM thing
+ -> TcM thing
-tcBindsAndThen combiner (BindWith bind sigs) do_next
- = tcBindAndThen combiner bind sigs do_next
+tcBindsAndThen = tc_binds_and_then NotTopLevel
-tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
-\end{code}
+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
+ = do_next
-An aside. The original version of @tcBindsAndThen@ which lacks a
-combiner function, appears below. Though it is perfectly well
-behaved, it cannot be typed by Haskell, because the recursive call is
-at a different type to the definition itself. There aren't too many
-examples of this, which is why I thought it worth preserving! [SLPJ]
+tc_binds_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
-\begin{pseudocode}
-tcBindsAndThen
- :: RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty))
- -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
+tc_binds_and_then top_lvl combiner (IPBinds binds is_with) do_next
+ = getLIE do_next `thenM` \ (result, expr_lie) ->
+ mapAndUnzipM tc_ip_bind binds `thenM` \ (avail_ips, binds') ->
-tcBindsAndThen EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
+ -- If the binding binds ?x = E, we must now
+ -- discharge any ?x constraints in expr_lie
+ tcSimplifyIPs avail_ips expr_lie `thenM` \ dict_binds ->
-tcBindsAndThen (SingleBind bind) do_next
- = tcBindAndThen bind [] do_next
+ returnM (combiner (IPBinds binds' is_with) $
+ combiner (mkMonoBind Recursive dict_binds) result)
+ where
+ -- I wonder if we should do these one at at time
+ -- Consider ?x = 4
+ -- ?y = ?x + 1
+ tc_ip_bind (ip, expr)
+ = newTyVarTy openTypeKind `thenM` \ ty ->
+ getSrcLocM `thenM` \ loc ->
+ newIPDict (IPBind ip) ip ty `thenM` \ (ip', ip_inst) ->
+ tcCheckRho expr ty `thenM` \ expr' ->
+ returnM (ip_inst, (ip', expr'))
+
+tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
+ = -- 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) $
+
+ tcBindWithSigs top_lvl bind sigs is_rec `thenM` \ (poly_binds, poly_ids) ->
+
+ case top_lvl of
+ TopLevel -- For the top level don't bother will all this
+ -- bindInstsOfLocalFuns stuff. All the top level
+ -- things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ --
+ -- Subtle (and ugly) point: furthermore at top level we
+ -- return the TcLclEnv, which contains the LIE var; we
+ -- don't want to return the wrong one!
+ -> tc_body poly_ids `thenM` \ (prag_binds, thing) ->
+ returnM (combiner (mkMonoBind Recursive (poly_binds `andMonoBinds` prag_binds))
+ thing)
+
+ NotTopLevel -- For nested bindings we must do teh bindInstsOfLocalFuns thing
+ -> getLIE (tc_body poly_ids) `thenM` \ ((prag_binds, thing), lie) ->
+
+ -- Create specialisations of functions bound here
+ bindInstsOfLocalFuns lie poly_ids `thenM` \ lie_binds ->
+
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unlifted bindings correctly
+ if isRec is_rec then
+ returnM (
+ combiner (mkMonoBind Recursive (
+ poly_binds `andMonoBinds`
+ lie_binds `andMonoBinds`
+ prag_binds)) thing
+ )
+ else
+ returnM (
+ combiner (mkMonoBind NonRecursive poly_binds) $
+ combiner (mkMonoBind NonRecursive prag_binds) $
+ combiner (mkMonoBind 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)
+ where
+ tc_body poly_ids -- Type check the pragmas and "thing inside"
+ = -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv poly_ids $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcSpecSigs sigs `thenM` \ prag_binds ->
-tcBindsAndThen (BindWith bind sigs) do_next
- = tcBindAndThen bind sigs do_next
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenM` \ thing ->
-tcBindsAndThen (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
+ returnM (prag_binds, thing)
+\end{code}
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-\end{pseudocode}
%************************************************************************
%* *
-\subsection{Bind}
+\subsection{tcBindWithSigs}
%* *
%************************************************************************
-\begin{code}
-tcBindAndThen
- :: (TcHsBinds s -> thing -> thing) -- Combinator
- -> RenamedBind -- The Bind to typecheck
- -> [RenamedSig] -- ...and its signatures
- -> TcM s (thing, LIE s, thing_ty) -- Thing to type check in
- -- augmented envt
- -> TcM s (thing, LIE s, thing_ty) -- Results, incl the
-
-tcBindAndThen combiner bind sigs do_next
- = fixTc (\ ~(prag_info_fn, _) ->
- -- This is the usual prag_info fix; the PragmaInfo field of an Id
- -- is not inspected till ages later in the compiler, so there
- -- should be no black-hole problems here.
-
- tcBindAndSigs binder_names bind
- sigs prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+@tcBindWithSigs@ deals with a single binding group. It does generalisation,
+so all the clever stuff is in here.
- -- Extend the environment to bind the new polymorphic Ids
- tcExtendLocalValEnv binder_names poly_ids $
+* binder_names and mbind must define the same set of Names
- -- Build bindings and IdInfos corresponding to user pragmas
- tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+* The Names in tc_ty_sigs must be a subset of binder_names
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie, thing_ty) ->
+* The Ids in tc_ty_sigs don't necessarily have to have the same name
+ as the Name in the tc_ty_sig
- -- Create specialisations of functions bound here
- bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
- poly_ids `thenTc` \ (lie2, inst_mbinds) ->
-
- -- All done
- let
- final_lie = lie2 `plusLIE` poly_lie
- final_binds = poly_binds `ThenBinds`
- SingleBind (NonRecBind inst_mbinds) `ThenBinds`
- prag_binds
- in
- returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty))
- ) `thenTc` \ (_, result) ->
- returnTc result
- where
- binder_names = map fst (bagToList (collectBinders bind))
-
-
-tcBindAndSigs binder_names bind sigs prag_info_fn
- = recoverTc (
+\begin{code}
+tcBindWithSigs
+ :: TopLevelFlag
+ -> RenamedMonoBinds
+ -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs
+ -> RecFlag
+ -> TcM (TcMonoBinds, [TcId])
+
+tcBindWithSigs top_lvl mbind sigs is_rec
+ = -- TYPECHECK THE SIGNATURES
+ recoverM (returnM []) (
+ mappM tcTySig [sig | sig@(Sig name _ _) <- sigs]
+ ) `thenM` \ tc_ty_sigs ->
+
+ -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
+ recoverM (
-- If typechecking the binds fails, then return with each
- -- binder given type (forall a.a), to minimise subsequent
+ -- signature-less binder given type (forall a.a), to minimise subsequent
-- error messages
- newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
+ newTyVar liftedTypeKind `thenM` \ alpha_tv ->
let
- forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
- poly_ids = [ mkUserId name forall_a_a (prag_info_fn name)
- | name <- binder_names]
+ 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 sig -> tcSigPolyId sig -- Signature
+ Nothing -> mkLocalId name forall_a_a -- No signature
in
- returnTc (EmptyBinds, emptyLIE, poly_ids)
- ) $
+ traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names) `thenM_`
+ returnM (EmptyMonoBinds, 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 ->
- newTyVarTys no_of_binders kind `thenNF_Tc` \ tys ->
+ -- TYPECHECK THE BINDINGS
+ getLIE (tcMonoBinds mbind tc_ty_sigs is_rec) `thenM` \ ((mbind', bndr_names_w_ids), lie_req) ->
let
- mono_ids = zipWith3Equal "tcBindAndSigs" mk_id binder_names uniqs tys
- mk_id name uniq ty = mkUserLocal (getOccName name) uniq ty (getSrcLoc name)
+ (binder_names, mono_ids) = unzip (bagToList bndr_names_w_ids)
+ tau_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids
in
- tcExtendLocalValEnv binder_names mono_ids (
- tcTySigs sigs `thenTc` \ sig_info ->
- tc_bind bind `thenTc` \ (bind', lie) ->
- returnTc (bind', lie, sig_info)
+
+ -- GENERALISE
+ -- (it seems a bit crude to have to do getLIE twice,
+ -- but I can't see a better way just now)
+ addSrcLoc (minimum (map getSrcLoc binder_names)) $
+ addErrCtxt (genCtxt binder_names) $
+ getLIE (generalise binder_names mbind tau_tvs lie_req tc_ty_sigs)
+ `thenM` \ ((tc_tyvars_to_gen, dict_binds, dict_ids), lie_free) ->
+
+
+ -- ZONK THE GENERALISED TYPE VARIABLES TO REAL TyVars
+ -- This commits any unbound kind variables to boxed kind, by unification
+ -- It's important that the final quanfified type variables
+ -- are fully zonked, *including boxity*, because they'll be
+ -- included in the forall types of the polymorphic Ids.
+ -- At calls of these Ids we'll instantiate fresh type variables from
+ -- them, and we use their boxity then.
+ mappM zonkTcTyVarToTyVar tc_tyvars_to_gen `thenM` \ real_tyvars_to_gen ->
+
+ -- ZONK THE Ids
+ -- It's important that the dict Ids are zonked, including the boxity set
+ -- in the previous step, because they are later used to form the type of
+ -- the polymorphic thing, and forall-types must be zonked so far as
+ -- their bound variables are concerned
+ mappM zonkId dict_ids `thenM` \ zonked_dict_ids ->
+ mappM zonkId mono_ids `thenM` \ zonked_mono_ids ->
+
+ -- BUILD THE POLYMORPHIC RESULT IDs
+ let
+ exports = zipWith mk_export binder_names zonked_mono_ids
+ poly_ids = [poly_id | (_, poly_id, _) <- exports]
+ dict_tys = map idType zonked_dict_ids
+
+ inlines = mkNameSet [name | InlineSig True name _ loc <- sigs]
+ -- Any INLINE sig (regardless of phase control)
+ -- makes the RHS look small
+ inline_phases = listToFM [(name, phase) | InlineSig _ name phase _ <- sigs,
+ not (isAlwaysActive phase)]
+ -- Set the IdInfo field to control the inline phase
+ -- AlwaysActive is the default, so don't bother with them
+
+ mk_export binder_name zonked_mono_id
+ = (tyvars,
+ attachInlinePhase inline_phases poly_id,
+ zonked_mono_id)
+ where
+ (tyvars, poly_id) =
+ case maybeSig tc_ty_sigs binder_name of
+ Just (TySigInfo sig_poly_id sig_tyvars _ _ _ _ _) ->
+ (sig_tyvars, sig_poly_id)
+ Nothing -> (real_tyvars_to_gen, new_poly_id)
+
+ new_poly_id = mkLocalId binder_name poly_ty
+ poly_ty = mkForAllTys real_tyvars_to_gen
+ $ mkFunTys dict_tys
+ $ idType zonked_mono_id
+ -- It's important to build a fully-zonked poly_ty, because
+ -- we'll slurp out its free type variables when extending the
+ -- local environment (tcExtendLocalValEnv); if it's not zonked
+ -- it appears to have free tyvars that aren't actually free
+ -- at all.
+ in
+
+ traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
+ exports, map idType poly_ids)) `thenM_`
+
+ -- Check for an unlifted, non-overloaded group
+ -- In that case we must make extra checks
+ if any (isUnLiftedType . idType) zonked_mono_ids && null zonked_dict_ids
+ then -- Some bindings are unlifted
+ checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind `thenM_`
+
+ extendLIEs lie_req `thenM_`
+ returnM (
+ AbsBinds [] [] exports inlines mbind',
+ -- Do not generate even any x=y bindings
+ poly_ids
+ )
+
+ else -- The normal case
+ extendLIEs lie_free `thenM_`
+ returnM (
+ AbsBinds real_tyvars_to_gen
+ zonked_dict_ids
+ exports
+ inlines
+ (dict_binds `andMonoBinds` mbind'),
+ poly_ids
)
- `thenTc` \ (bind', lie, sig_info) ->
- -- Notice that genBinds gets the old (non-extended) environment
- genBinds binder_names mono_ids bind' lie sig_info prag_info_fn
+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) `thenM_`
+ checkTc (isNonRec is_rec)
+ (unliftedBindErr "Recursive" mbind) `thenM_`
+ checkTc (single_bind mbind)
+ (unliftedBindErr "Multiple" mbind) `thenM_`
+ checkTc (null real_tyvars_to_gen)
+ (unliftedBindErr "Polymorphic" mbind)
+
where
- no_of_binders = length binder_names
- kind = case bind of
- NonRecBind _ -> mkTypeKind -- Recursive, so no unboxed types
- RecBind _ -> mkBoxedTypeKind -- Non-recursive, so we permit unboxed types
+ single_bind (PatMonoBind _ _ _) = True
+ single_bind (FunMonoBind _ _ _ _) = True
+ single_bind other = False
\end{code}
-===========
-\begin{code}
-{-
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
-data SigInfo
- = SigInfo Name
- (TcIdBndr s) -- Polymorpic version
- (TcIdBndr s) -- Monomorphic verstion
- [TcType s] [TcIdOcc s] -- Instance information for the monomorphic version
+ * 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...
- -- Deal with type signatures
- tcTySigs sigs `thenTc` \ sig_infos ->
- let
- sig_binders = [binder | SigInfo binder _ _ _ _ <- sig_infos]
- poly_sigs = [(name,poly) | SigInfo name poly _ _ _ <- sig_infos]
- mono_sigs = [(name,mono) | SigInfo name _ mono _ _ <- sig_infos]
- nosig_binders = binders `minusList` sig_binders
- in
+If we don't take care, after typechecking we get
+
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
+
+Notice the the stupid construction of (f a d), which is of course
+identical to the function we're executing. In this case, the
+polymorphic recursion isn't being used (but that's a very common case).
+We'd prefer
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
- -- Typecheck the binding group
- tcExtendLocalEnv poly_sigs (
- newLocalIds nosig_binders kind (\ nosig_local_ids ->
- tcMonoBinds mono_sigs mono_binds `thenTc` \ binds_w_lies ->
- returnTc (nosig_local_ids, binds_w_lies)
- )) `thenTc` \ (nosig_local_ids, binds_w_lies) ->
+This can lead to a massive space leak, from the following top-level defn
+(post-typechecking)
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
- -- Decide what to generalise over
- getImplicitStuffToGen sig_ids binds_w_lies
- `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen, lie_to_gen) ->
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
+ ff = f Int dEqInt
- *** CHECK FOR UNBOXED TYVARS HERE! ***
+ = let f' = f Int dEqInt in \ys. ...f'...
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
+Etc.
+Solution: when typechecking the RHSs we always have in hand the
+*monomorphic* Ids for each binding. So we just need to make sure that
+if (Method f a d) shows up in the constraints emerging from (...f...)
+we just use the monomorphic Id. We achieve this by adding monomorphic Ids
+to the "givens" when simplifying constraints. That's what the "lies_avail"
+is doing.
- -- Make poly_ids for all the binders that don't have type signatures
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
+
+\begin{code}
+generalise binder_names mbind tau_tvs lie_req sigs =
+
+ -- check for -fno-monomorphism-restriction
+ doptM Opt_NoMonomorphismRestriction `thenM` \ no_MR ->
+ let is_unrestricted | no_MR = True
+ | otherwise = isUnRestrictedGroup tysig_names mbind
+ in
+
+ if not is_unrestricted then -- RESTRICTED CASE
+ -- Check signature contexts are empty
+ checkTc (all is_mono_sig sigs)
+ (restrictedBindCtxtErr binder_names) `thenM_`
+
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ tcSimplifyRestricted doc tau_tvs lie_req `thenM` \ (qtvs, binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars qtvs sigs `thenM` \ final_qtvs ->
+
+ returnM (final_qtvs, binds, [])
+
+ else if null sigs then -- UNRESTRICTED CASE, NO TYPE SIGS
+ tcSimplifyInfer doc tau_tvs lie_req
+
+ else -- UNRESTRICTED CASE, WITH TYPE SIGS
+ -- CHECKING CASE: Unrestricted group, there are type signatures
+ -- Check signature contexts are identical
+ checkSigsCtxts sigs `thenM` \ (sig_avails, sig_dicts) ->
+
+ -- Check that the needed dicts can be
+ -- expressed in terms of the signature ones
+ tcSimplifyInferCheck doc tau_tvs sig_avails lie_req `thenM` \ (forall_tvs, dict_binds) ->
+
+ -- Check that signature type variables are OK
+ checkSigsTyVars forall_tvs sigs `thenM` \ final_qtvs ->
+
+ returnM (final_qtvs, dict_binds, sig_dicts)
+
+ where
+ 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)
+ = addSrcLoc src_loc $
+ mappM_ check_one other_sigs `thenM_`
+ if null theta1 then
+ returnM ([], []) -- Non-overloaded type signatures
+ else
+ newDicts SignatureOrigin theta1 `thenM` \ sig_dicts ->
let
- tys_to_gen = mkTyVarTys tyvars_to_gen
- dicts_to_gen = map instToId (bagToList lie_to_gen)
- dict_tys = map tcIdType dicts_to_gen
-
- mk_poly binder local_id = mkUserId (getName binder) ty noPragmaInfo
- where
- ty = mkForAllTys tyvars_to_gen $
- mkFunTys dict_tys $
- tcIdType local_id
-
- more_sig_infos = [ SigInfo binder (mk_poly binder local_id)
- local_id tys_to_gen dicts_to_gen lie_to_gen
- | (binder, local_id) <- zipEqual "???" nosig_binders nosig_local_ids
- ]
-
- all_sig_infos = sig_infos ++ more_sig_infos -- Contains a "signature" for each binder
+ -- The "sig_avails" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the lie_avail
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ sig_avails = sig_dicts ++ sig_meths
in
+ returnM (sig_avails, map instToId sig_dicts)
+ where
+ sig1_dict_tys = map mkPredTy theta1
+ sig_meths = concat [insts | TySigInfo _ _ _ _ _ insts _ <- sigs]
+ check_one sig@(TySigInfo id _ theta _ _ _ _)
+ = addErrCtxt (sigContextsCtxt id1 id) $
+ checkTc (equalLength theta theta1) sigContextsErr `thenM_`
+ unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
- -- Now generalise the bindings
+checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
+checkSigsTyVars qtvs sigs
+ = mappM check_one sigs `thenM` \ sig_tvs_s ->
let
- -- local_binds is a bunch of bindings of the form
- -- f_mono = f_poly tyvars dicts
- -- one for each binder, f, that lacks a type signature.
- -- This bunch of bindings is put at the top of the RHS of every
- -- binding in the group, so as to bind all the f_monos.
-
- local_binds = [ (local_id, mkHsDictApp (mkHsTyApp (HsVar local_id) tys_to_gen) dicts_to_gen)
- | local_id <- nosig_local_ids
- ]
-
- find_sig lid = head [ (pid, tvs, ds, lie)
- | SigInfo _ pid lid' tvs ds lie,
- lid==lid'
- ]
-
- gen_bind (bind, lie)
- = tcSimplifyWithExtraGlobals tyvars_not_to_gen tyvars_to_gen avail lie
- `thenTc` \ (lie_free, dict_binds) ->
- returnTc (AbsBind tyvars_to_gen_here
- dicts
- (zipEqual "gen_bind" local_ids poly_ids)
- (dict_binds ++ local_binds)
- bind,
- lie_free)
- where
- local_ids = bindersOf bind
- local_sigs = [sig | sig@(SigInfo _ _ local_id _ _) <- all_sig_infos,
- local_id `elem` local_ids
- ]
-
- (tyvars_to_gen_here, dicts, avail)
- = case (local_ids, sigs) of
-
- ([local_id], [SigInfo _ _ _ tyvars_to_gen dicts lie])
- -> (tyvars_to_gen, dicts, lie)
-
- other -> (tyvars_to_gen, dicts, avail)
+ -- 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
+ returnM (varSetElems all_tvs)
+ where
+ check_one (TySigInfo id sig_tyvars sig_theta sig_tau _ _ src_loc)
+ = addSrcLoc src_loc $
+ addErrCtxt (ptext SLIT("When checking the type signature for")
+ <+> quotes (ppr id)) $
+ addErrCtxtM (sigCtxt id sig_tyvars sig_theta sig_tau) $
+ checkSigTyVarsWrt (idFreeTyVars id) sig_tyvars
\end{code}
-@getImplicitStuffToGen@ decides what type variables
-and LIE to generalise over.
+@getTyVarsToGen@ decides what type variables to generalise over.
For a "restricted group" -- see the monomorphism restriction
for a definition -- we bind no dictionaries, and
we'll know that the literals are all Ints, and we can just produce
Int literals!
-Find all the type variables involved in overloading, the "constrained_tyvars".
-These are the ones we *aren't* going to generalise.
-We must be careful about doing this:
+Find all the type variables involved in overloading, the
+"constrained_tyvars". These are the ones we *aren't* going to
+generalise. We must be careful about doing this:
+
(a) If we fail to generalise a tyvar which is not actually
constrained, then it will never, ever get bound, and lands
up printed out in interface files! Notorious example:
Another, more common, example is when there's a Method inst in
the LIE, whose type might very well involve non-overloaded
type variables.
+ [NOTE: Jan 2001: I don't understand the problem here so I'm doing
+ the simple thing instead]
+
(b) On the other hand, we mustn't generalise tyvars which are constrained,
because we are going to pass on out the unmodified LIE, with those
tyvars in it. They won't be in scope if we've generalised them.
find which tyvars are constrained.
\begin{code}
-getImplicitStuffToGen is_restricted sig_ids binds_w_lies
- | isUnRestrictedGroup tysig_vars bind
- = tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, dicts_to_gen) ->
- returnNF_Tc (emptyTyVarSet, tyvars_to_gen, dicts_to_gen)
-
- | otherwise
- = tcSimplify tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
- let
- -- ASSERT: dicts_sig is already zonked!
- constrained_tyvars = foldBag unionTyVarSets tyVarsOfInst emptyTyVarSet constrained_dicts
- reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars
- in
- returnTc (constrained_tyvars, reduced_tyvars_to_gen, emptyLIE)
-
- where
- sig_vars = [sig_var | (TySigInfo sig_var _ _ _ _) <- ty_sigs]
-
- (tyvars_to_gen, lie) = foldBag (\(tv1,lie2) (tv2,lie2) -> (tv1 `unionTyVarSets` tv2,
- lie1 `plusLIE` lie2))
- get
- (emptyTyVarSet, emptyLIE)
- binds_w_lies
- get (bind, lie)
- = case bindersOf bind of
- [local_id] | local_id `in` sig_ids -> -- A simple binding with
- -- a type signature
- (emptyTyVarSet, emptyLIE)
-
- local_ids -> -- Complex binding or no type sig
- (foldr (unionTyVarSets . tcIdType) emptyTyVarSet local_ids,
- lie)
--}
-\end{code}
-
-
+isUnRestrictedGroup :: [Name] -- Signatures given for these
+ -> RenamedMonoBinds
+ -> Bool
-\begin{code}
-tc_bind :: RenamedBind -> TcM s (TcBind s, LIE s)
+is_elem v vs = isIn "isUnResMono" v vs
-tc_bind (NonRecBind mono_binds)
- = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (NonRecBind mono_binds2, lie)
+isUnRestrictedGroup sigs (PatMonoBind other _ _) = False
+isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
+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
-tc_bind (RecBind mono_binds)
- = tcMonoBinds mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (RecBind mono_binds2, lie)
+isUnRestrictedMatch (Match [] _ _ : _) = False -- No args => like a pattern binding
+isUnRestrictedMatch other = True -- Some args => a function binding
\end{code}
-\begin{code}
-tcMonoBinds :: RenamedMonoBinds -> TcM s (TcMonoBinds s, LIE s)
-
-tcMonoBinds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
-
-tcMonoBinds (AndMonoBinds mb1 mb2)
- = tcMonoBinds mb1 `thenTc` \ (mb1a, lie1) ->
- tcMonoBinds mb2 `thenTc` \ (mb2a, lie2) ->
- returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
-
-tcMonoBinds bind@(PatMonoBind pat grhss_and_binds locn)
- = tcAddSrcLoc locn $
-
- -- LEFT HAND SIDE
- tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
-
- -- BINDINGS AND GRHSS
- tcGRHSsAndBinds grhss_and_binds `thenTc` \ (grhss_and_binds2, lie, grhss_ty) ->
-
- -- Unify the two sides
- tcAddErrCtxt (patMonoBindsCtxt bind) $
- unifyTauTy pat_ty grhss_ty `thenTc_`
-
- -- RETURN
- returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
- plusLIE lie_pat lie)
-
-tcMonoBinds (FunMonoBind name inf matches locn)
- = tcAddSrcLoc locn $
- tcLookupLocalValueOK "tcMonoBinds" name `thenNF_Tc` \ id ->
- tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
- returnTc (FunMonoBind (TcId id) inf matches' locn, lie)
-\end{code}
%************************************************************************
%* *
-\subsection{Signatures}
+\subsection{tcMonoBind}
%* *
%************************************************************************
-@tcSigs@ checks the signatures for validity, and returns a list of
-{\em freshly-instantiated} signatures. That is, the types are already
-split up, and have fresh type variables installed. All non-type-signature
-"RenamedSigs" are ignored.
+@tcMonoBinds@ deals with a single @MonoBind@.
+The signatures have been dealt with already.
\begin{code}
-tcTySigs :: [RenamedSig] -> TcM s [TcSigInfo s]
+tcMonoBinds :: RenamedMonoBinds
+ -> [TcSigInfo] -> RecFlag
+ -> TcM (TcMonoBinds,
+ Bag (Name, -- Bound names
+ TcId)) -- Corresponding monomorphic bound things
+
+tcMonoBinds mbinds tc_ty_sigs is_rec
+ -- Three stages:
+ -- 1. Check the patterns, building up an environment binding
+ -- the variables in this group (in the recursive case)
+ -- 2. Extend the environment
+ -- 3. Check the RHSs
+ = tc_mb_pats mbinds `thenM` \ (complete_it, xve) ->
+ tcExtendLocalValEnv2 (bagToList xve) complete_it
+ where
+ tc_mb_pats EmptyMonoBinds
+ = returnM (returnM (EmptyMonoBinds, emptyBag), emptyBag)
-tcTySigs (Sig v ty src_loc : other_sigs)
- = tcAddSrcLoc src_loc (
- tcHsType ty `thenTc` \ sigma_ty ->
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' ->
+ tc_mb_pats (AndMonoBinds mb1 mb2)
+ = tc_mb_pats mb1 `thenM` \ (complete_it1, xve1) ->
+ tc_mb_pats mb2 `thenM` \ (complete_it2, xve2) ->
let
- (tyvars', theta', tau') = splitSigmaTy sigma_ty'
+ complete_it = complete_it1 `thenM` \ (mb1', bs1) ->
+ complete_it2 `thenM` \ (mb2', bs2) ->
+ returnM (AndMonoBinds mb1' mb2', bs1 `unionBags` bs2)
in
+ returnM (complete_it, xve1 `unionBags` xve2)
+
+ tc_mb_pats (FunMonoBind name inf matches locn)
+ -- Three cases:
+ -- a) Type sig supplied
+ -- b) No type sig and recursive
+ -- c) No type sig and non-recursive
+
+ | Just sig <- maybeSig tc_ty_sigs name
+ = let -- (a) There is a type signature
+ -- Use it for the environment extension, and check
+ -- the RHS has the appropriate type (with outer for-alls stripped off)
+ mono_id = tcSigMonoId sig
+ mono_ty = idType mono_id
+ complete_it = addSrcLoc locn $
+ tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, if isRec is_rec then unitBag (name,tcSigPolyId sig)
+ else emptyBag)
+
+ | isRec is_rec
+ = -- (b) No type signature, and recursive
+ -- So we must use an ordinary H-M type variable
+ -- which means the variable gets an inferred tau-type
+ newLocalName name `thenM` \ mono_name ->
+ newTyVarTy openTypeKind `thenM` \ mono_ty ->
+ let
+ mono_id = mkLocalId mono_name mono_ty
+ complete_it = addSrcLoc locn $
+ tcMatchesFun name matches (Check mono_ty) `thenM` \ matches' ->
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, unitBag (name, mono_id))
+
+ | otherwise -- (c) No type signature, and non-recursive
+ = let -- So we can use a 'hole' type to infer a higher-rank type
+ complete_it
+ = addSrcLoc locn $
+ newHole `thenM` \ hole ->
+ tcMatchesFun name matches (Infer hole) `thenM` \ matches' ->
+ readMutVar hole `thenM` \ fun_ty ->
+ newLocalName name `thenM` \ mono_name ->
+ let
+ mono_id = mkLocalId mono_name fun_ty
+ in
+ returnM (FunMonoBind mono_id inf matches' locn,
+ unitBag (name, mono_id))
+ in
+ returnM (complete_it, emptyBag)
+
+ tc_mb_pats bind@(PatMonoBind pat grhss locn)
+ = addSrcLoc locn $
+
+ -- Now typecheck the pattern
+ -- We do now support binding fresh (not-already-in-scope) scoped
+ -- type variables in the pattern of a pattern binding.
+ -- For example, this is now legal:
+ -- (x::a, y::b) = e
+ -- The type variables are brought into scope in tc_binds_and_then,
+ -- so we don't have to do anything here.
+
+ newHole `thenM` \ hole ->
+ tcPat tc_pat_bndr pat (Infer hole) `thenM` \ (pat', tvs, ids, lie_avail) ->
+ readMutVar hole `thenM` \ pat_ty ->
+
+ -- Don't know how to deal with pattern-bound existentials yet
+ checkTc (isEmptyBag tvs && null lie_avail)
+ (existentialExplode bind) `thenM_`
- tcLookupLocalValueOK "tcSig1" v `thenNF_Tc` \ val ->
- unifyTauTy (idType val) tau' `thenTc_`
-
- returnTc (TySigInfo val tyvars' theta' tau' src_loc)
- ) `thenTc` \ sig_info1 ->
-
- tcTySigs other_sigs `thenTc` \ sig_infos ->
- returnTc (sig_info1 : sig_infos)
-
-tcTySigs (other : sigs) = tcTySigs sigs
-tcTySigs [] = returnTc []
+ let
+ complete_it = addSrcLoc locn $
+ addErrCtxt (patMonoBindsCtxt bind) $
+ tcGRHSsPat grhss (Check pat_ty) `thenM` \ grhss' ->
+ returnM (PatMonoBind pat' grhss' locn, ids)
+ in
+ returnM (complete_it, if isRec is_rec then ids else emptyBag)
+
+ -- tc_pat_bndr is used when dealing with a LHS binder in a pattern.
+ -- If there was a type sig for that Id, we want to make it much
+ -- as if that type signature had been on the binder as a SigPatIn.
+ -- We check for a type signature; if there is one, we use the mono_id
+ -- from the signature. This is how we make sure the tau part of the
+ -- signature actually matches the type of the LHS; then tc_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 `thenM` \ bndr_name ->
+ tcMonoPatBndr bndr_name pat_ty
+
+ Just sig -> addSrcLoc (getSrcLoc name) $
+ tcSubPat (idType mono_id) pat_ty `thenM` \ co_fn ->
+ returnM (co_fn, mono_id)
+ where
+ mono_id = tcSigMonoId sig
\end{code}
%* *
%************************************************************************
-
-@tcPragmaSigs@ munches up the "signatures" that arise through *user*
+@tcSpecSigs@ munches up the specialisation "signatures" that arise through *user*
pragmas. It is convenient for them to appear in the @[RenamedSig]@
part of a binding because then the same machinery can be used for
moving them into place as is done for type signatures.
-\begin{code}
-tcPragmaSigs :: [RenamedSig] -- The pragma signatures
- -> TcM s (Name -> PragmaInfo, -- Maps name to the appropriate PragmaInfo
- TcHsBinds s,
- LIE s)
-
-tcPragmaSigs sigs = returnTc ( \name -> NoPragmaInfo, EmptyBinds, emptyLIE )
+They look like this:
-{-
-tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
- let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
- in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
-
-\begin{code}
-tcPragmaSig (DeforestSig name loc)
- = returnTc ((name, addDeforestInfo DoDeforest),EmptyBinds,emptyLIE)
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addUnfoldInfo (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addUnfoldInfo (mkMagicUnfolding string)), EmptyBinds, emptyLIE)
-\end{code}
-
-The interesting case is for SPECIALISE pragmas. There are two forms.
-Here's the first form:
\begin{verbatim}
f :: Ord a => [a] -> b -> b
{-# SPECIALIZE f :: [Int] -> b -> b #-}
Int, and will create a specialisation for @f@. After that, the
binding for @f*@ can be discarded.
-The second form is this:
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b = g #-}
-\end{verbatim}
-
-Here @g@ is specified as a function that implements the specialised
-version of @f@. Suppose that g has type (a->b->b); that is, g's type
-is more general than that required. For this we generate
-\begin{verbatim}
- f@Int = /\b -> g Int b
- f* = f@Int
-\end{verbatim}
-
-Here @f@@Int@ is a SpecId, the specialised version of @f@. It inherits
-f's export status etc. @f*@ is a SpecPragmaId, as before, which just serves
-to prevent @f@@Int@ from being discarded prematurely. After specialisation,
-if @f@@Int@ is going to be used at all it will be used explicitly, so the simplifier can
-discard the f* binding.
-
-Actually, there is really only point in giving a SPECIALISE pragma on exported things,
-and the simplifer won't discard SpecIds for exporte things anyway, so maybe this is
-a bit of overkill.
+We used to have a form
+ {-# SPECIALISE f :: <type> = g #-}
+which promised that g implemented f at <type>, but we do that with
+a RULE now:
+ {-# SPECIALISE (f::<type) = g #-}
\begin{code}
-tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
- = tcAddSrcLoc src_loc $
- tcAddErrCtxt (valSpecSigCtxt name spec_ty) $
+tcSpecSigs :: [RenamedSig] -> TcM TcMonoBinds
+tcSpecSigs (SpecSig name poly_ty src_loc : sigs)
+ = -- SPECIALISE f :: forall b. theta => tau = g
+ addSrcLoc src_loc $
+ addErrCtxt (valSpecSigCtxt name poly_ty) $
-- Get and instantiate its alleged specialised type
- tcHsType poly_ty `thenTc` \ sig_sigma ->
- tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
- let
- (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
- origin = ValSpecOrigin name
- in
+ tcHsSigType (FunSigCtxt name) poly_ty `thenM` \ sig_ty ->
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (null sig_theta)
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
+ -- Check that f has a more general type, and build a RHS for
+ -- the spec-pragma-id at the same time
+ getLIE (tcCheckSigma (HsVar name) sig_ty) `thenM` \ (spec_expr, spec_lie) ->
- -- Get and instantiate the type of the id mentioned
- tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ main_id ->
- tcInstSigType [] (idType main_id) `thenNF_Tc` \ main_ty ->
+ -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
+ tcSimplifyToDicts spec_lie `thenM` \ spec_binds ->
+
+ -- Just specialise "f" by building a SpecPragmaId binding
+ -- It is the thing that makes sure we don't prematurely
+ -- dead-code-eliminate the binding we are really interested in.
+ newLocalName name `thenM` \ spec_name ->
let
- (main_tyvars, main_rho) = splitForAllTy main_ty
- (main_theta,main_tau) = splitRhoTy main_rho
- main_arg_tys = mkTyVarTys main_tyvars
+ spec_bind = VarMonoBind (mkSpecPragmaId spec_name sig_ty)
+ (mkHsLet spec_binds spec_expr)
in
- -- Check that the specialised type is indeed an instance of
- -- the type of the main function.
- unifyTauTy sig_tau main_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Check that the type variables of the polymorphic function are
- -- either left polymorphic, or instantiate to ground type.
- -- Also check that the overloaded type variables are instantiated to
- -- ground type; or equivalently that all dictionaries have ground type
- mapTc zonkTcType main_arg_tys `thenNF_Tc` \ main_arg_tys' ->
- zonkTcThetaType main_theta `thenNF_Tc` \ main_theta' ->
- tcAddErrCtxt (specGroundnessCtxt main_arg_tys')
- (checkTc (all isGroundOrTyVarTy main_arg_tys')) `thenTc_`
- tcAddErrCtxt (specContextGroundnessCtxt main_theta')
- (checkTc (and [isGroundTy ty | (_,ty) <- theta'])) `thenTc_`
-
- -- Build the SpecPragmaId; it is the thing that makes sure we
- -- don't prematurely dead-code-eliminate the binding we are really interested in.
- newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_pragma_id ->
-
- -- Build a suitable binding; depending on whether we were given
- -- a value (Maybe Name) to be used as the specialisation.
- case using of
- Nothing -> -- No implementation function specified
-
- -- Make a Method inst for the occurrence of the overloaded function
- newMethodWithGivenTy (OccurrenceOf name)
- (TcId main_id) main_arg_tys main_rho `thenNF_Tc` \ (lie, meth_id) ->
-
- let
- pseudo_bind = VarMonoBind spec_pragma_id pseudo_rhs
- pseudo_rhs = mkHsTyLam sig_tyvars (HsVar (TcId meth_id))
- in
- returnTc (pseudo_bind, lie, \ info -> info)
-
- Just spec_name -> -- Use spec_name as the specialisation value ...
-
- -- Type check a simple occurrence of the specialised Id
- tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
+ -- Do the rest and combine
+ tcSpecSigs sigs `thenM` \ binds_rest ->
+ returnM (binds_rest `andMonoBinds` spec_bind)
- -- Check that it has the correct type, and doesn't constrain the
- -- signature variables at all
- unifyTauTy sig_tau spec_tau `thenTc_`
- checkSigTyVars sig_tyvars sig_tau `thenTc_`
-
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id main_arg_tys sig_ty `thenNF_Tc` \ local_spec_id ->
-
- let
- spec_rhs = mkHsTyLam sig_tyvars spec_body
- spec_binds = VarMonoBind local_spec_id spec_rhs
- `AndMonoBinds`
- VarMonoBind spec_pragma_id (HsVar (TcId local_spec_id))
- spec_info = SpecInfo spec_tys (length main_theta) local_spec_id
- in
- returnTc ((name, addSpecInfo spec_info), spec_binds, spec_lie)
--}
+tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
+tcSpecSigs [] = returnM EmptyMonoBinds
\end{code}
%************************************************************************
%* *
-\subsection[TcBinds-monomorphism]{The monomorphism restriction}
+\subsection[TcBinds-errors]{Error contexts and messages}
%* *
%************************************************************************
-Not exported:
\begin{code}
-{- In GenSpec at the moment
-
-isUnRestrictedGroup :: [TcIdBndr s] -- Signatures given for these
- -> TcBind s
- -> Bool
-
-isUnRestrictedGroup sigs EmptyBind = True
-isUnRestrictedGroup sigs (NonRecBind monobinds) = isUnResMono sigs monobinds
-isUnRestrictedGroup sigs (RecBind monobinds) = isUnResMono sigs monobinds
+patMonoBindsCtxt bind
+ = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
-is_elem v vs = isIn "isUnResMono" v vs
-
-isUnResMono sigs (PatMonoBind (VarPat (TcId v)) _ _) = v `is_elem` sigs
-isUnResMono sigs (PatMonoBind other _ _) = False
-isUnResMono sigs (VarMonoBind (TcId v) _) = v `is_elem` sigs
-isUnResMono sigs (FunMonoBind _ _ _ _) = True
-isUnResMono sigs (AndMonoBinds mb1 mb2) = isUnResMono sigs mb1 &&
- isUnResMono sigs mb2
-isUnResMono sigs EmptyMonoBinds = True
--}
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[TcBinds-errors]{Error contexts and messages}
-%* *
-%************************************************************************
+-----------------------------------------------
+valSpecSigCtxt v ty
+ = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
+ nest 4 (ppr v <+> dcolon <+> ppr ty)]
+-----------------------------------------------
+sigContextsErr = ptext SLIT("Mismatched contexts")
-\begin{code}
-patMonoBindsCtxt bind sty
- = ppHang (ppPStr SLIT("In a pattern binding:")) 4 (ppr sty bind)
-
---------------------------------------------
-specContextGroundnessCtxt -- err_ctxt dicts sty
- = panic "specContextGroundnessCtxt"
-{-
- = ppHang (
- ppSep [ppBesides [ppStr "In the SPECIALIZE pragma for `", ppr sty name, ppStr "'"],
- ppBesides [ppStr " specialised to the type `", ppr sty spec_ty, ppStr "'"],
- pp_spec_id sty,
- ppStr "... not all overloaded type variables were instantiated",
- ppStr "to ground types:"])
- 4 (ppAboves [ppCat [ppr sty c, ppr sty t]
- | (c,t) <- map getDictClassAndType dicts])
- where
- (name, spec_ty, locn, pp_spec_id)
- = case err_ctxt of
- ValSpecSigCtxt n ty loc -> (n, ty, loc, \ x -> ppNil)
- ValSpecSpecIdCtxt n ty spec loc ->
- (n, ty, loc,
- \ sty -> ppBesides [ppStr "... type of explicit id `", ppr sty spec, ppStr "'"])
--}
+sigContextsCtxt s1 s2
+ = vcat [ptext SLIT("When matching the contexts of the signatures for"),
+ nest 2 (vcat [ppr s1 <+> dcolon <+> ppr (idType s1),
+ ppr s2 <+> dcolon <+> ppr (idType s2)]),
+ ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
-----------------------------------------------
-specGroundnessCtxt
- = panic "specGroundnessCtxt"
+unliftedBindErr flavour mbind
+ = 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)
-valSpecSigCtxt v ty sty
- = ppHang (ppPStr SLIT("In a SPECIALIZE pragma for a value:"))
- 4 (ppSep [ppBeside (pprNonSym sty v) (ppPStr SLIT(" ::")),
- ppr sty ty])
+-----------------------------------------------
+restrictedBindCtxtErr binder_names
+ = hang (ptext SLIT("Illegal overloaded type signature(s)"))
+ 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
+ ptext SLIT("that falls under the monomorphism restriction")])
+
+genCtxt binder_names
+ = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names
+
+-- Used in error messages
+-- Use quotes for a single one; they look a bit "busy" for several
+pprBinders [bndr] = quotes (ppr bndr)
+pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
-
projects / ghc-hetmet.git / blobdiff