%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
+module TcBinds ( tcBindsAndThen, tcTopBinds,
+ tcSpecSigs, tcBindWithSigs ) where
+
#include "HsVersions.h"
-module TcBinds ( tcBindsAndThen, tcPragmaSigs ) where
+import {-# SOURCE #-} TcMatches ( tcGRHSs, tcMatchesFun )
+import {-# SOURCE #-} TcExpr ( tcExpr )
-IMP_Ubiq()
+import CmdLineOpts ( opt_NoMonomorphismRestriction )
+import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..),
+ Match(..), HsMatchContext(..),
+ collectMonoBinders, andMonoBinds
+ )
+import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
+import TcHsSyn ( TcMonoBinds, TcId, zonkId, mkHsLet )
-import HsSyn ( HsBinds(..), Bind(..), Sig(..), MonoBinds(..),
- HsExpr, Match, PolyType, InPat, OutPat(..),
- GRHSsAndBinds, ArithSeqInfo, HsLit, Fake,
- collectBinders )
-import RnHsSyn ( SYN_IE(RenamedHsBinds), SYN_IE(RenamedBind), RenamedSig(..),
- SYN_IE(RenamedMonoBinds), RnName(..)
+import TcMonad
+import Inst ( LIE, emptyLIE, mkLIE, plusLIE, InstOrigin(..),
+ newDicts, instToId
+ )
+import TcEnv ( tcExtendLocalValEnv,
+ newSpecPragmaId, newLocalId
+ )
+import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck, tcSimplifyCheck, tcSimplifyRestricted, tcSimplifyToDicts )
+import TcMonoType ( tcHsSigType, checkSigTyVars,
+ TcSigInfo(..), tcTySig, maybeSig, sigCtxt
)
-import TcHsSyn ( SYN_IE(TcHsBinds), SYN_IE(TcBind), SYN_IE(TcMonoBinds),
- TcIdOcc(..), SYN_IE(TcIdBndr) )
-
-import TcMonad hiding ( rnMtoTcM )
-import GenSpecEtc ( checkSigTyVars, genBinds, TcSigInfo(..) )
-import Inst ( Inst, SYN_IE(LIE), emptyLIE, plusLIE, InstOrigin(..) )
-import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK, newMonoIds )
-IMPORT_DELOOPER(TcLoop) ( tcGRHSsAndBinds )
-import TcMatches ( tcMatchesFun )
-import TcMonoType ( tcPolyType )
import TcPat ( tcPat )
import TcSimplify ( bindInstsOfLocalFuns )
-import TcType ( newTcTyVar, tcInstSigType )
-import Unify ( unifyTauTy )
-
-import Kind ( mkBoxedTypeKind, mkTypeKind )
-import Id ( GenId, idType, mkUserId )
-import IdInfo ( noIdInfo )
-import Maybes ( assocMaybe, catMaybes )
-import Name ( pprNonSym, Name )
-import PragmaInfo ( PragmaInfo(..) )
-import Pretty
-import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy,
- mkSigmaTy, splitSigmaTy,
- splitRhoTy, mkForAllTy, splitForAllTy )
-import Util ( isIn, zipEqual, panic )
+import TcType ( newTyVarTy, newTyVar,
+ zonkTcTyVarToTyVar
+ )
+import TcUnify ( unifyTauTy, unifyTauTyLists )
+
+import CoreFVs ( idFreeTyVars )
+import Id ( mkLocalId, setInlinePragma )
+import Var ( idType, idName )
+import IdInfo ( InlinePragInfo(..) )
+import Name ( Name, getOccName, getSrcLoc )
+import NameSet
+import Type ( mkTyVarTy, tyVarsOfTypes,
+ mkForAllTys, mkFunTys, tyVarsOfType,
+ mkPredTy, mkForAllTy, isUnLiftedType,
+ unliftedTypeKind, liftedTypeKind, openTypeKind
+ )
+import Var ( tyVarKind )
+import VarSet
+import Bag
+import Util ( isIn )
+import ListSetOps ( minusList )
+import Maybes ( maybeToBool )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..), isNonRec, isNotTopLevel )
+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}
+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
- :: (TcHsBinds s -> thing -> thing) -- Combinator
+ :: (RecFlag -> TcMonoBinds -> thing -> thing) -- Combinator
-> RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty)
- -> TcM s (thing, LIE s, thing_ty)
+ -> TcM (thing, LIE)
+ -> TcM (thing, LIE)
+
+tcBindsAndThen = tc_binds_and_then NotTopLevel
+
+tc_binds_and_then top_lvl combiner EmptyBinds do_next
+ = do_next
+tc_binds_and_then top_lvl combiner (MonoBind EmptyMonoBinds sigs is_rec) do_next
+ = do_next
+
+tc_binds_and_then top_lvl combiner (ThenBinds b1 b2) do_next
+ = tc_binds_and_then top_lvl combiner b1 $
+ tc_binds_and_then top_lvl combiner b2 $
+ do_next
+
+tc_binds_and_then top_lvl combiner (MonoBind bind sigs is_rec) do_next
+ = -- TYPECHECK THE SIGNATURES
+ mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs ->
+
+ tcBindWithSigs top_lvl bind tc_ty_sigs
+ sigs is_rec `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+
+ -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv [(idName poly_id, poly_id) | poly_id <- poly_ids] $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcSpecSigs sigs `thenTc` \ (prag_binds, prag_lie) ->
-tcBindsAndThen combiner EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc (combiner EmptyBinds thing, lie, thing_ty)
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenTc` \ (thing, thing_lie) ->
-tcBindsAndThen combiner (SingleBind bind) do_next
- = tcBindAndThen combiner bind [] do_next
+ -- Create specialisations of functions bound here
+ -- We want to keep non-recursive things non-recursive
+ -- 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
+ -- All the top level things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ (TopLevel, _)
+ -> returnTc (combiner Recursive (poly_binds `andMonoBinds` prag_binds) thing,
+ thing_lie `plusLIE` prag_lie `plusLIE` poly_lie)
+
+ (NotTopLevel, NonRecursive)
+ -> bindInstsOfLocalFuns
+ (thing_lie `plusLIE` prag_lie)
+ poly_ids `thenTc` \ (thing_lie', lie_binds) ->
+
+ returnTc (
+ combiner NonRecursive poly_binds $
+ combiner NonRecursive prag_binds $
+ combiner Recursive lie_binds $
+ -- NB: the binds returned by tcSimplify and bindInstsOfLocalFuns
+ -- aren't guaranteed in dependency order (though we could change
+ -- that); hence the Recursive marker.
+ thing,
+
+ thing_lie' `plusLIE` poly_lie
+ )
+
+ (NotTopLevel, Recursive)
+ -> bindInstsOfLocalFuns
+ (thing_lie `plusLIE` poly_lie `plusLIE` prag_lie)
+ poly_ids `thenTc` \ (final_lie, lie_binds) ->
+
+ returnTc (
+ combiner Recursive (
+ poly_binds `andMonoBinds`
+ lie_binds `andMonoBinds`
+ prag_binds) thing,
+ final_lie
+ )
+\end{code}
-tcBindsAndThen combiner (BindWith bind sigs) do_next
- = tcBindAndThen combiner bind sigs do_next
-tcBindsAndThen combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen combiner binds1 (tcBindsAndThen combiner binds2 do_next)
-\end{code}
+%************************************************************************
+%* *
+\subsection{tcBindWithSigs}
+%* *
+%************************************************************************
-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]
+@tcBindWithSigs@ deals with a single binding group. It does generalisation,
+so all the clever stuff is in here.
-\begin{pseudocode}
-tcBindsAndThen
- :: RenamedHsBinds
- -> TcM s (thing, LIE s, thing_ty))
- -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
+* binder_names and mbind must define the same set of Names
-tcBindsAndThen EmptyBinds do_next
- = do_next `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
+* The Names in tc_ty_sigs must be a subset of binder_names
-tcBindsAndThen (SingleBind bind) do_next
- = tcBindAndThen bind [] do_next
+* The Ids in tc_ty_sigs don't necessarily have to have the same name
+ as the Name in the tc_ty_sig
-tcBindsAndThen (BindWith bind sigs) do_next
- = tcBindAndThen bind sigs do_next
+\begin{code}
+tcBindWithSigs
+ :: TopLevelFlag
+ -> RenamedMonoBinds
+ -> [TcSigInfo]
+ -> [RenamedSig] -- Used solely to get INLINE, NOINLINE sigs
+ -> RecFlag
+ -> TcM (TcMonoBinds, LIE, [TcId])
+
+tcBindWithSigs top_lvl mbind tc_ty_sigs inline_sigs is_rec
+ = recoverTc (
+ -- If typechecking the binds fails, then return with each
+ -- signature-less binder given type (forall a.a), to minimise subsequent
+ -- error messages
+ newTyVar liftedTypeKind `thenNF_Tc` \ alpha_tv ->
+ let
+ forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
+ binder_names = collectMonoBinders mbind
+ poly_ids = map mk_dummy binder_names
+ mk_dummy name = case maybeSig tc_ty_sigs name of
+ Just (TySigInfo _ poly_id _ _ _ _ _ _) -> poly_id -- Signature
+ Nothing -> mkLocalId name forall_a_a -- No signature
+ in
+ returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
+ ) $
-tcBindsAndThen (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
+ -- TYPECHECK THE BINDINGS
+ tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) ->
+ let
+ tau_tvs = varSetElems (foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet mono_ids)
+ in
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-\end{pseudocode}
+ -- GENERALISE
+ generalise binder_names mbind tau_tvs lie_req tc_ty_sigs
+ `thenTc` \ (tc_tyvars_to_gen, lie_free, dict_binds, dict_ids) ->
-%************************************************************************
-%* *
-\subsection{Bind}
-%* *
-%************************************************************************
-\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) ->
-
- -- 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) ->
+ -- 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 ->
- -- Now do whatever happens next, in the augmented envt
- do_next `thenTc` \ (thing, thing_lie, thing_ty) ->
+ -- 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 ->
- -- Create specialisations of functions bound here
- bindInstsOfLocalFuns (prag_lie `plusLIE` thing_lie)
- poly_ids `thenTc` \ (lie2, inst_mbinds) ->
+ -- CHECK FOR BOGUS UNLIFTED BINDINGS
+ checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids `thenTc_`
- -- All done
+ -- BUILD THE POLYMORPHIC RESULT IDs
let
- final_lie = lie2 `plusLIE` poly_lie
- final_binds = poly_binds `ThenBinds`
- SingleBind (NonRecBind inst_mbinds) `ThenBinds`
- prag_binds
+ exports = zipWith mk_export binder_names zonked_mono_ids
+ 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
+
+ mk_export binder_name zonked_mono_id
+ = (tyvars,
+ attachNoInlinePrag no_inlines 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
- returnTc (prag_info_fn, (combiner final_binds thing, final_lie, thing_ty))
- ) `thenTc` \ (_, result) ->
- returnTc result
- where
- binder_names = collectBinders bind
-
-tcBindAndSigs binder_rn_names bind sigs prag_info_fn
- = let
- binder_names = map de_rn binder_rn_names
- de_rn (RnName n) = n
- in
- recoverTc (
- -- If typechecking the binds fails, then return with each
- -- binder given type (forall a.a), to minimise subsequent
- -- error messages
- newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ 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]
- in
- returnTc (EmptyBinds, emptyLIE, poly_ids)
- ) $
-
- -- Create a new identifier for each binder, with each being given
- -- a type-variable type.
- newMonoIds binder_rn_names kind (\ mono_ids ->
- tcTySigs sigs `thenTc` \ sig_info ->
- tc_bind bind `thenTc` \ (bind', lie) ->
- returnTc (mono_ids, bind', lie, sig_info)
+ traceTc (text "binding:" <+> ppr ((zonked_dict_ids, dict_binds),
+ exports, [idType poly_id | (_, poly_id, _) <- exports])) `thenTc_`
+
+ -- BUILD RESULTS
+ returnTc (
+ AbsBinds real_tyvars_to_gen
+ zonked_dict_ids
+ exports
+ inlines
+ (dict_binds `andMonoBinds` mbind'),
+ lie_free,
+ [poly_id | (_, poly_id, _) <- exports]
)
- `thenTc` \ (mono_ids, 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
+attachNoInlinePrag no_inlines bndr
+ = case lookupFM no_inlines (idName bndr) of
+ Just prag -> bndr `setInlinePragma` prag
+ Nothing -> bndr
+
+checkUnliftedBinds top_lvl is_rec real_tyvars_to_gen mbind zonked_mono_ids
+ = ASSERT( not (any ((== 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.
+
+ -- Check that pattern-bound variables are not unlifted
+ (if or [ (idName id `elem` pat_binders) && isUnLiftedType (idType id)
+ | id <- zonked_mono_ids ] then
+ addErrTc (unliftedBindErr "Pattern" mbind)
+ else
+ returnTc ()
+ ) `thenTc_`
+
+ -- Unlifted bindings must be non-recursive,
+ -- not top level, non-polymorphic, and not pattern bound
+ if any (isUnLiftedType . idType) zonked_mono_ids then
+ checkTc (isNotTopLevel top_lvl)
+ (unliftedBindErr "Top-level" mbind) `thenTc_`
+ checkTc (isNonRec is_rec)
+ (unliftedBindErr "Recursive" mbind) `thenTc_`
+ checkTc (null real_tyvars_to_gen)
+ (unliftedBindErr "Polymorphic" mbind)
+ else
+ returnTc ()
+
where
- kind = case bind of
- NonRecBind _ -> mkTypeKind -- Recursive, so no unboxed types
- RecBind _ -> mkBoxedTypeKind -- Non-recursive, so we permit unboxed types
+ pat_binders :: [Name]
+ pat_binders = collectMonoBinders (justPatBindings mbind EmptyMonoBinds)
+
+ justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds
+ justPatBindings (AndMonoBinds b1 b2) binds =
+ justPatBindings b1 (justPatBindings b2 binds)
+ justPatBindings other_bind binds = binds
\end{code}
-===========
-\begin{code}
-{-
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
-data SigInfo
- = SigInfo RnName
- (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
- -- Typecheck the binding group
- tcExtendLocalEnv poly_sigs (
- newMonoIds 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) ->
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
+This can lead to a massive space leak, from the following top-level defn
+(post-typechecking)
- -- Decide what to generalise over
- getImplicitStuffToGen sig_ids binds_w_lies
- `thenTc` \ (tyvars_not_to_gen, tyvars_to_gen, lie_to_gen) ->
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
- *** CHECK FOR UNBOXED TYVARS HERE! ***
+ ff = f Int dEqInt
+
+ = let f' = f Int dEqInt in \ys. ...f'...
+
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
+
+Etc.
+Solution: when typechecking the RHSs we always have in hand the
+*monomorphic* Ids for each binding. So we just need to make sure that
+if (Method f a d) shows up in the constraints emerging from (...f...)
+we just use the monomorphic Id. We achieve this by adding monomorphic Ids
+to the "givens" when simplifying constraints. That's what the "lies_avail"
+is doing.
+
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
+\begin{code}
+generalise_help doc tau_tvs lie_req sigs
+-----------------------
+ | null sigs
+ = -- INFERENCE CASE: Unrestricted group, no type signatures
+ tcSimplifyInfer doc
+ tau_tvs lie_req
- -- Make poly_ids for all the binders that don't have type signatures
+-----------------------
+ | otherwise
+ = -- CHECKING CASE: Unrestricted group, there are type signatures
+ -- Check signature contexts are empty
+ 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 sigs `thenTc_`
+
+ returnTc (forall_tvs, lie_free, dict_binds, sig_dicts)
+
+generalise binder_names mbind tau_tvs lie_req sigs
+ | is_unrestricted -- UNRESTRICTED CASE
+ = generalise_help doc tau_tvs lie_req sigs
+
+ | otherwise -- RESTRICTED CASE
+ = -- Do a simplification to decide what type variables
+ -- are constrained. We can't just take the free vars
+ -- of lie_req because that'll have methods that may
+ -- incidentally mention entirely unconstrained variables
+ -- e.g. a call to f :: Eq a => a -> b -> b
+ -- Here, b is unconstrained. A good example would be
+ -- foo = f (3::Int)
+ -- We want to infer the polymorphic type
+ -- foo :: forall b. b -> b
+ generalise_help doc tau_tvs lie_req sigs `thenTc` \ (forall_tvs, lie_free, dict_binds, dict_ids) ->
+
+ -- Check signature contexts are empty
+ checkTc (null sigs || null dict_ids)
+ (restrictedBindCtxtErr binder_names) `thenTc_`
+
+ -- Identify constrained tyvars
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
+ constrained_tvs = varSetElems (tyVarsOfTypes (map idType dict_ids))
+ -- The dict_ids are fully zonked
+ final_forall_tvs = forall_tvs `minusList` constrained_tvs
in
+ -- Now simplify with exactly that set of tyvars
+ -- We have to squash those Methods
+ tcSimplifyRestricted doc final_forall_tvs [] lie_req `thenTc` \ (lie_free, binds) ->
+
+ returnTc (final_forall_tvs, lie_free, binds, [])
- -- Now generalise the bindings
+ where
+ is_unrestricted | opt_NoMonomorphismRestriction = True
+ | otherwise = isUnRestrictedGroup tysig_names mbind
+
+ tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- sigs]
+
+ 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 _ _ _ _ : other_sigs)
+ = mapTc_ check_one other_sigs `thenTc_`
+ if null theta1 then
+ returnTc ([], []) -- Non-overloaded type signatures
+ else
+ newDicts SignatureOrigin theta1 `thenNF_Tc` \ sig_dicts ->
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)
+ -- 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
+ n_sig1_theta = length theta1
+ sig_meths = concat [insts | TySigInfo _ _ _ _ _ _ insts _ <- sigs]
+
+ check_one sig@(TySigInfo _ id _ theta _ _ _ src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (sigContextsCtxt id1 id) $
+ checkTc (length theta == n_sig1_theta) sigContextsErr `thenTc_`
+ unifyTauTyLists sig1_dict_tys (map mkPredTy theta)
+
+checkSigsTyVars sigs = mapTc_ check_one sigs
+ where
+ check_one (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)
+
+ sig_msg id = ptext SLIT("When checking the type signature for") <+> quotes (ppr id)
\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 _) = any 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 _ [] Nothing _) = False -- No args, no signature
+isUnRestrictedMatch other = True -- Some args or a signature
\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,
+ LIE, -- LIE required
+ [Name], -- Bound names
+ [TcId]) -- Corresponding monomorphic bound things
+
+tcMonoBinds mbinds tc_ty_sigs is_rec
+ = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) ->
+ let
+ id_list = bagToList ids
+ (names, mono_ids) = unzip id_list
+
+ -- This last defn is the key one:
+ -- extend the val envt with bindings for the
+ -- things bound in this group, overriding the monomorphic
+ -- ids with the polymorphic ones from the pattern
+ extra_val_env = case is_rec of
+ Recursive -> map mk_bind id_list
+ NonRecursive -> []
+ in
+ -- Don't know how to deal with pattern-bound existentials yet
+ checkTc (isEmptyBag tvs && isEmptyBag lie_avail)
+ (existentialExplode mbinds) `thenTc_`
+
+ -- *Before* checking the RHSs, but *after* checking *all* the patterns,
+ -- extend the envt with bindings for all the bound ids;
+ -- and *then* override with the polymorphic Ids from the signatures
+ -- That is the whole point of the "complete_it" stuff.
+ --
+ -- There's a further wrinkle: we have to delay extending the environment
+ -- until after we've dealt with any pattern-bound signature type variables
+ -- Consider f (x::a) = ...f...
+ -- We're going to check that a isn't unified with anything in the envt,
+ -- so f itself had better not be! So we pass the envt binding f into
+ -- complete_it, which extends the actual envt in TcMatches.tcMatch, after
+ -- dealing with the signature tyvars
+
+ complete_it extra_val_env `thenTc` \ (mbinds', lie_req_rhss) ->
+
+ returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids)
+ where
-tcTySigs (Sig v ty _ src_loc : other_sigs)
- = tcAddSrcLoc src_loc (
- tcPolyType ty `thenTc` \ sigma_ty ->
- tcInstSigType sigma_ty `thenNF_Tc` \ sigma_ty' ->
+ -- This function is used when dealing with a LHS binder;
+ -- we make a monomorphic version of the Id.
+ -- 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 maatches 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
+ -> newLocalId (getOccName name) pat_ty (getSrcLoc name)
+
+ Just (TySigInfo _ _ _ _ _ mono_id _ _)
+ -> tcAddSrcLoc (getSrcLoc name) $
+ unifyTauTy (idType mono_id) pat_ty `thenTc_`
+ returnTc mono_id
+
+ mk_bind (name, mono_id) = case maybeSig tc_ty_sigs name of
+ Nothing -> (name, mono_id)
+ Just (TySigInfo name poly_id _ _ _ _ _ _) -> (name, poly_id)
+
+ tc_mb_pats EmptyMonoBinds
+ = returnTc (\ xve -> returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
+
+ tc_mb_pats (AndMonoBinds mb1 mb2)
+ = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) ->
+ tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) ->
let
- (tyvars', theta', tau') = splitSigmaTy sigma_ty'
+ complete_it xve = complete_it1 xve `thenTc` \ (mb1', lie1) ->
+ complete_it2 xve `thenTc` \ (mb2', lie2) ->
+ returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2)
in
+ returnTc (complete_it,
+ lie_req1 `plusLIE` lie_req2,
+ tvs1 `unionBags` tvs2,
+ ids1 `unionBags` ids2,
+ lie_avail1 `plusLIE` lie_avail2)
+
+ tc_mb_pats (FunMonoBind name inf matches locn)
+ = newTyVarTy kind `thenNF_Tc` \ bndr_ty ->
+ tc_pat_bndr name bndr_ty `thenTc` \ bndr_id ->
+ let
+ complete_it xve = tcAddSrcLoc locn $
+ tcMatchesFun xve name bndr_ty matches `thenTc` \ (matches', lie) ->
+ returnTc (FunMonoBind bndr_id inf matches' locn, lie)
+ in
+ returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
+
+ tc_mb_pats bind@(PatMonoBind pat grhss locn)
+ = tcAddSrcLoc locn $
+ newTyVarTy kind `thenNF_Tc` \ pat_ty ->
+
+ -- Now typecheck the pattern
+ -- We don't support binding fresh type variables in the
+ -- pattern of a pattern binding. For example, this is illegal:
+ -- (x::a, y::b) = e
+ -- whereas this is ok
+ -- (x::Int, y::Bool) = e
+ --
+ -- We don't check explicitly for this problem. Instead, we simply
+ -- type check the pattern with tcPat. If the pattern mentions any
+ -- fresh tyvars we simply get an out-of-scope type variable error
+ tcPat tc_pat_bndr pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
+ let
+ complete_it xve = tcAddSrcLoc locn $
+ tcAddErrCtxt (patMonoBindsCtxt bind) $
+ tcExtendLocalValEnv xve $
+ tcGRHSs grhss pat_ty PatBindRhs `thenTc` \ (grhss', lie) ->
+ returnTc (PatMonoBind pat' grhss' locn, lie)
+ in
+ returnTc (complete_it, lie_req, tvs, ids, lie_avail)
- 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 []
+ -- Figure out the appropriate kind for the pattern,
+ -- and generate a suitable type variable
+ kind = case is_rec of
+ Recursive -> liftedTypeKind -- Recursive, so no unlifted types
+ NonRecursive -> openTypeKind -- Non-recursive, so we permit unlifted types
\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 )
-
-{-
-tcPragmaSigs sigs
- = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (names_w_id_infos, binds, lies) ->
- let
- name_to_info name = foldr ($) noIdInfo
- [info_fn | (n,info_fn) <- names_w_id_infos, n==name]
- in
- returnTc (name_to_info,
- foldr ThenBinds EmptyBinds binds,
- foldr plusLIE emptyLIE lies)
-\end{code}
-
-Here are the easy cases for tcPragmaSigs
+They look like this:
-\begin{code}
-tcPragmaSig (DeforestSig name loc)
- = returnTc ((name, addInfo DoDeforest),EmptyBinds,emptyLIE)
-tcPragmaSig (InlineSig name loc)
- = returnTc ((name, addInfo_UF (iWantToBeINLINEd UnfoldAlways)), EmptyBinds, emptyLIE)
-tcPragmaSig (MagicUnfoldingSig name string loc)
- = returnTc ((name, addInfo_UF (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, 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
- tcPolyType 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_`
-
- -- 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
-
- -- 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) ->
+ tcHsSigType poly_ty `thenTc` \ sig_ty ->
- 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)
+ -- 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) ->
- Just spec_name -> -- Use spec_name as the specialisation value ...
+ -- Squeeze out any Methods (see comments with tcSimplifyToDicts)
+ tcSimplifyToDicts spec_lie `thenTc` \ (spec_dicts, spec_binds) ->
- -- Type check a simple occurrence of the specialised Id
- tcId spec_name `thenTc` \ (spec_body, spec_lie, spec_tau) ->
+ -- 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 ->
- -- 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_`
+ -- 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` mkLIE spec_dicts)
- -- 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, addInfo spec_info), spec_binds, spec_lie)
--}
+tcSpecSigs (other_sig : sigs) = tcSpecSigs sigs
+tcSpecSigs [] = returnTc (EmptyMonoBinds, emptyLIE)
\end{code}
%************************************************************************
%* *
-\subsection[TcBinds-monomorphism]{The monomorphism restriction}
+\subsection[TcBinds-errors]{Error contexts and messages}
%* *
%************************************************************************
-Not exported:
\begin{code}
-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
-
-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}
+patMonoBindsCtxt bind
+ = hang (ptext SLIT("In a pattern binding:")) 4 (ppr bind)
+-----------------------------------------------
+valSpecSigCtxt v ty
+ = sep [ptext SLIT("In a SPECIALIZE pragma for a value:"),
+ nest 4 (ppr v <+> dcolon <+> ppr ty)]
-%************************************************************************
-%* *
-\subsection[TcBinds-errors]{Error contexts and messages}
-%* *
-%************************************************************************
+-----------------------------------------------
+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)"))
-\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 "'"])
--}
+-----------------------------------------------
+unliftedBindErr flavour mbind
+ = hang (text flavour <+> ptext SLIT("bindings for unlifted types aren't allowed:"))
+ 4 (ppr mbind)
-----------------------------------------------
-specGroundnessCtxt
- = panic "specGroundnessCtxt"
+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")])
-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])
+-- Used in error messages
+pprBinders bndrs = pprWithCommas ppr bndrs
\end{code}
-
projects / ghc-hetmet.git / blobdiff