%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcBinds]{TcBinds}
\begin{code}
-#include "HsVersions.h"
+module TcBinds ( tcBindsAndThen, tcTopBindsAndThen,
+ tcPragmaSigs, tcBindWithSigs ) where
-module TcBinds (
- tcTopBindsAndThen, tcLocalBindsAndThen
- ) where
+#include "HsVersions.h"
---IMPORT_Trace -- ToDo:rm (debugging)
+import {-# SOURCE #-} TcGRHSs ( tcGRHSsAndBinds )
+import {-# SOURCE #-} TcExpr ( tcExpr )
-import TcMonad -- typechecking monad machinery
-import TcMonadFns ( newLocalsWithOpenTyVarTys,
- newLocalsWithPolyTyVarTys,
- newSpecPragmaId, newSpecId,
- applyTcSubstAndCollectTyVars
+import HsSyn ( HsExpr(..), HsBinds(..), MonoBinds(..), Sig(..), InPat(..), StmtCtxt(..),
+ collectMonoBinders, andMonoBindList, andMonoBinds
+ )
+import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
+import TcHsSyn ( TcHsBinds, TcMonoBinds,
+ TcIdOcc(..), TcIdBndr,
+ tcIdType, zonkId
)
-import AbsSyn -- the stuff being typechecked
-import AbsUniType ( isTyVarTy, isGroundTy, isUnboxedDataType,
- isGroundOrTyVarTy, extractTyVarsFromTy,
- UniType
+import TcMonad
+import Inst ( Inst, LIE, emptyLIE, mkLIE, plusLIE, plusLIEs, InstOrigin(..),
+ newDicts, tyVarsOfInst, instToId,
)
-import BackSubst ( applyTcSubstToBinds )
-import E
-import Errors ( topLevelUnboxedDeclErr, specGroundnessErr,
- specCtxtGroundnessErr, Error(..), UnifyErrContext(..)
+import TcEnv ( tcExtendLocalValEnv, tcExtendEnvWithPat,
+ tcLookupLocalValueOK,
+ newSpecPragmaId,
+ tcGetGlobalTyVars, tcExtendGlobalTyVars
)
-import GenSpecEtc ( checkSigTyVars, genBinds, SignatureInfo(..) )
-import Id ( getIdUniType, mkInstId )
-import IdInfo ( SpecInfo(..) )
-import Inst
-import LIE ( nullLIE, mkLIE, plusLIE, LIE )
-import Maybes ( assocMaybe, catMaybes, Maybe(..) )
-import Spec ( specTy )
-import TVE ( nullTVE, TVE(..), UniqFM )
-import TcMonoBnds ( tcMonoBinds )
-import TcPolyType ( tcPolyType )
+import TcMatches ( tcMatchesFun )
+import TcSimplify ( tcSimplify, tcSimplifyAndCheck )
+import TcMonoType ( tcHsTcType, checkSigTyVars,
+ TcSigInfo(..), tcTySig, maybeSig, sigCtxt
+ )
+import TcPat ( tcVarPat, tcPat )
import TcSimplify ( bindInstsOfLocalFuns )
-import Unify ( unifyTauTy )
-import UniqFM ( emptyUFM ) -- profiling, pragmas only
-import Util
+import TcType ( TcType, TcThetaType,
+ TcTyVar,
+ newTyVarTy, newTcTyVar, tcInstTcType,
+ zonkTcType, zonkTcTypes, zonkTcThetaType )
+import TcUnify ( unifyTauTy, unifyTauTyLists )
+
+import Id ( mkUserId )
+import Var ( idType, idName, setIdInfo )
+import IdInfo ( IdInfo, noIdInfo, setInlinePragInfo, InlinePragInfo(..) )
+import Name ( Name )
+import Type ( mkTyVarTy, tyVarsOfTypes,
+ splitSigmaTy, mkForAllTys, mkFunTys, getTyVar,
+ mkDictTy, splitRhoTy, mkForAllTy, isUnLiftedType,
+ isUnboxedType, openTypeKind,
+ unboxedTypeKind, boxedTypeKind
+ )
+import Var ( TyVar, tyVarKind )
+import VarSet
+import Bag
+import Util ( isIn )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
+import SrcLoc ( SrcLoc )
+import Outputable
\end{code}
-%************************************************************************
-%* *
-\subsection{Type-checking top-level bindings}
-%* *
-%************************************************************************
-
-@tcBindsAndThen@ takes a boolean which indicates whether the binding
-group is at top level or not. The difference from inner bindings is
-that
-\begin{enumerate}
-\item
-we zero the substitution before each group
-\item
-we back-substitute after each group.
-\end{enumerate}
-We still return an LIE, but it is sure to contain nothing but constant
-dictionaries, which we resolve at the module level.
-
-@tcTopBinds@ returns an LVE, not, as you might expect, a GVE. Why?
-Because the monomorphism restriction means that is might return some
-monomorphic things, with free type variables. Hence it must be an LVE.
-
-The LIE returned by @tcTopBinds@ may constrain some type variables,
-but they are guaranteed to be a subset of those free in the
-corresponding returned LVE.
%************************************************************************
%* *
%* *
%************************************************************************
-@tcBindsAndThen@ typechecks a @Binds@. The "and then" part is because
+@tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
it needs to know something about the {\em usage} of the things bound,
so that it can create specialisations of them. So @tcBindsAndThen@
takes a function which, given an extended environment, E, typechecks
@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
checked the type of its LHS is unified with that of its RHS; and
type-checking the LHS of course requires that the binder is in scope.
-\begin{code}
-tcBindsAndThen
- :: Bool
- -> E
- -> (TypecheckedBinds -> thing -> thing) -- Combinator
- -> RenamedBinds
- -> (E -> TcM (thing, LIE, thing_ty))
- -> TcM (thing, LIE, thing_ty)
-
-tcBindsAndThen top_level e combiner EmptyBinds do_next
- = do_next e `thenTc` \ (thing, lie, thing_ty) ->
- returnTc (combiner EmptyBinds thing, lie, thing_ty)
-
-tcBindsAndThen top_level e combiner (SingleBind bind) do_next
- = tcBindAndThen top_level e combiner bind [] do_next
-
-tcBindsAndThen top_level e combiner (BindWith bind sigs) do_next
- = tcBindAndThen top_level e combiner bind sigs do_next
-
-tcBindsAndThen top_level e combiner (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen top_level e combiner binds1 new_after
- where
- -- new_after :: E -> TcM (thing, LIE, thing_ty)
- -- Can't write this signature, cos it's monomorphic in thing and
- -- thing_ty.
- new_after e = tcBindsAndThen top_level e combiner binds2 do_next
-\end{code}
+At the top-level the LIE is sure to contain nothing but constant
+dictionaries, which we resolve at the module level.
-Simple wrappers for export:
\begin{code}
-tcTopBindsAndThen
- :: E
- -> (TypecheckedBinds -> thing -> thing) -- Combinator
- -> RenamedBinds
- -> (E -> TcM (thing, LIE, anything))
- -> TcM (thing, LIE, anything)
-
-tcTopBindsAndThen e combiner binds do_next
- = tcBindsAndThen True e combiner binds do_next
-
-tcLocalBindsAndThen
- :: E
- -> (TypecheckedBinds -> thing -> thing) -- Combinator
- -> RenamedBinds
- -> (E -> TcM (thing, LIE, thing_ty))
- -> TcM (thing, LIE, thing_ty)
-
-tcLocalBindsAndThen e combiner binds do_next
- = tcBindsAndThen False e combiner binds do_next
+tcTopBindsAndThen, tcBindsAndThen
+ :: (RecFlag -> TcMonoBinds s -> thing -> thing) -- Combinator
+ -> RenamedHsBinds
+ -> TcM s (thing, LIE s)
+ -> TcM s (thing, LIE s)
+
+tcTopBindsAndThen = tc_binds_and_then TopLevel
+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
+ = fixTc (\ ~(prag_info_fn, _, _) ->
+ -- This is the usual prag_info fix; the PragmaInfo field of an Id
+ -- is not inspected till ages later in the compiler, so there
+ -- should be no black-hole problems here.
+
+ -- TYPECHECK THE SIGNATURES
+ mapTc tcTySig [sig | sig@(Sig name _ _) <- sigs] `thenTc` \ tc_ty_sigs ->
+
+ tcBindWithSigs top_lvl bind
+ tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+
+ -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv (map idName poly_ids) poly_ids $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenTc` \ (thing, thing_lie) ->
+
+ -- Create specialisations of functions bound here
+ -- We want to keep non-recursive things non-recursive
+ -- so that we desugar unboxed bindings correctly
+ case (top_lvl, is_rec) of
+
+ -- For the top level don't bother will all this bindInstsOfLocalFuns stuff
+ -- All the top level things are rec'd together anyway, so it's fine to
+ -- leave them to the tcSimplifyTop, and quite a bit faster too
+ (TopLevel, _)
+ -> returnTc (prag_info_fn,
+ 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 (
+ prag_info_fn,
+ 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 (
+ prag_info_fn,
+ combiner Recursive (
+ poly_binds `andMonoBinds`
+ lie_binds `andMonoBinds`
+ prag_binds) thing,
+ final_lie
+ )
+ ) `thenTc` \ (_, thing, lie) ->
+ returnTc (thing, lie)
\end{code}
An aside. The original version of @tcBindsAndThen@ which lacks a
examples of this, which is why I thought it worth preserving! [SLPJ]
\begin{pseudocode}
-tcBindsAndThen
- :: Bool -> E -> RenamedBinds
- -> (E -> TcM (thing, LIE, thing_ty))
- -> TcM ((TypecheckedBinds, thing), LIE, thing_ty)
-
-tcBindsAndThen top_level e EmptyBinds do_next
- = do_next e `thenTc` \ (thing, lie, thing_ty) ->
- returnTc ((EmptyBinds, thing), lie, thing_ty)
-
-tcBindsAndThen top_level e (SingleBind bind) do_next
- = tcBindAndThen top_level e bind [] do_next
-
-tcBindsAndThen top_level e (BindWith bind sigs) do_next
- = tcBindAndThen top_level e bind sigs do_next
-
-tcBindsAndThen top_level e (ThenBinds binds1 binds2) do_next
- = tcBindsAndThen top_level e binds1 new_after
- `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
-
- returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
-
- where
- -- new_after :: E -> TcM ((TypecheckedBinds, thing), LIE, thing_ty)
- -- Can't write this signature, cos it's monomorphic in thing and thing_ty
- new_after e = tcBindsAndThen top_level e binds2 do_next
+% tcBindsAndThen
+% :: RenamedHsBinds
+% -> TcM s (thing, LIE s, thing_ty))
+% -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
+%
+% tcBindsAndThen EmptyBinds do_next
+% = do_next `thenTc` \ (thing, lie, thing_ty) ->
+% returnTc ((EmptyBinds, thing), lie, thing_ty)
+%
+% tcBindsAndThen (ThenBinds binds1 binds2) do_next
+% = tcBindsAndThen binds1 (tcBindsAndThen binds2 do_next)
+% `thenTc` \ ((binds1', (binds2', thing')), lie1, thing_ty) ->
+%
+% returnTc ((binds1' `ThenBinds` binds2', thing'), lie1, thing_ty)
+%
+% tcBindsAndThen (MonoBind bind sigs is_rec) do_next
+% = tcBindAndThen bind sigs do_next
\end{pseudocode}
+
%************************************************************************
%* *
-\subsection{Bind}
+\subsection{tcBindWithSigs}
%* *
%************************************************************************
+@tcBindWithSigs@ deals with a single binding group. It does generalisation,
+so all the clever stuff is in here.
+
+* binder_names and mbind must define the same set of Names
+
+* The Names in tc_ty_sigs must be a subset of binder_names
+
+* The Ids in tc_ty_sigs don't necessarily have to have the same name
+ as the Name in the tc_ty_sig
+
\begin{code}
-tcBindAndThen
- :: Bool -- At top level
- -> E
- -> (TypecheckedBinds -> thing -> thing) -- Combinator
- -> RenamedBind -- The Bind to typecheck
- -> [RenamedSig] -- ...and its signatures
- -> (E -> TcM (thing, LIE, thing_ty)) -- Thing to type check in
- -- augmented envt
- -> TcM (thing, LIE, thing_ty) -- Results, incl the
-
-tcBindAndThen top_level e combiner bind sigs do_next
- = -- Deal with the bind
- tcBind top_level e bind sigs `thenTc` \ (poly_binds, poly_lie, poly_lve) ->
+tcBindWithSigs
+ :: TopLevelFlag
+ -> RenamedMonoBinds
+ -> [TcSigInfo s]
+ -> RecFlag
+ -> (Name -> IdInfo)
+ -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s])
+
+tcBindWithSigs top_lvl mbind tc_ty_sigs is_rec prag_info_fn
+ = recoverTc (
+ -- If typechecking the binds fails, then return with each
+ -- signature-less binder given type (forall a.a), to minimise subsequent
+ -- error messages
+ newTcTyVar boxedTypeKind `thenNF_Tc` \ alpha_tv ->
+ let
+ forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
+ binder_names = map fst (bagToList (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 -> mkUserId name forall_a_a -- No signature
+ in
+ returnTc (EmptyMonoBinds, emptyLIE, poly_ids)
+ ) $
+
+ -- TYPECHECK THE BINDINGS
+ tcMonoBinds mbind tc_ty_sigs is_rec `thenTc` \ (mbind', lie_req, binder_names, mono_ids) ->
- -- Now do whatever happens next, in the augmented envt
- do_next (growE_LVE e poly_lve) `thenTc` \ (thing, thing_lie, thing_ty) ->
let
- bound_ids = map snd poly_lve
+ mono_id_tys = map idType mono_ids
in
- -- Create specialisations
- specialiseBinds bound_ids thing_lie poly_binds poly_lie
- `thenNF_Tc` \ (final_binds, final_lie) ->
- -- All done
- returnTc (combiner final_binds thing, final_lie, thing_ty)
+
+ -- CHECK THAT THE SIGNATURES MATCH
+ -- (must do this before getTyVarsToGen)
+ checkSigMatch tc_ty_sigs `thenTc` \ (sig_theta, lie_avail) ->
+
+ -- COMPUTE VARIABLES OVER WHICH TO QUANTIFY, namely tyvars_to_gen
+ -- The tyvars_not_to_gen are free in the environment, and hence
+ -- candidates for generalisation, but sometimes the monomorphism
+ -- restriction means we can't generalise them nevertheless
+ getTyVarsToGen is_unrestricted mono_id_tys lie_req `thenNF_Tc` \ (tyvars_not_to_gen, tyvars_to_gen) ->
+
+ -- DEAL WITH TYPE VARIABLE KINDS
+ -- **** This step can do unification => keep other zonking after this ****
+ mapTc defaultUncommittedTyVar (varSetElems tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
+ let
+ real_tyvars_to_gen = mkVarSet real_tyvars_to_gen_list
+ -- It's important that the final list
+ -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
+ -- zonked, *including boxity*, because they'll be included in the forall types of
+ -- the polymorphic Ids, and instances of these Ids will be generated from them.
+ --
+ -- Also NB that tcSimplify takes zonked tyvars as its arg, hence we pass
+ -- real_tyvars_to_gen
+ in
+
+ -- SIMPLIFY THE LIE
+ tcExtendGlobalTyVars tyvars_not_to_gen (
+ if null real_tyvars_to_gen_list then
+ -- No polymorphism, so no need to simplify context
+ returnTc (lie_req, EmptyMonoBinds, [])
+ else
+ if null tc_ty_sigs then
+ -- No signatures, so just simplify the lie
+ -- NB: no signatures => no polymorphic recursion, so no
+ -- need to use lie_avail (which will be empty anyway)
+ tcSimplify (text "tcBinds1" <+> ppr binder_names)
+ top_lvl real_tyvars_to_gen lie_req `thenTc` \ (lie_free, dict_binds, lie_bound) ->
+ returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
+
+ else
+ zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' ->
+ newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) ->
+ -- It's important that sig_theta is zonked, because
+ -- dict_id is later used to form the type of the polymorphic thing,
+ -- and forall-types must be zonked so far as their bound variables
+ -- are concerned
+
+ let
+ -- The "givens" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the lie_avail
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ givens = dicts_sig `plusLIE` lie_avail
+ in
+
+ -- Check that the needed dicts can be expressed in
+ -- terms of the signature ones
+ tcAddErrCtxt (bindSigsCtxt tysig_names) $
+ tcSimplifyAndCheck
+ (ptext SLIT("type signature for") <+> pprQuotedList binder_names)
+ real_tyvars_to_gen givens lie_req `thenTc` \ (lie_free, dict_binds) ->
+
+ returnTc (lie_free, dict_binds, dict_ids)
+
+ ) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
+
+ -- GET THE FINAL MONO_ID_TYS
+ zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
+
+
+ -- CHECK FOR BOGUS UNPOINTED BINDINGS
+ (if any isUnLiftedType zonked_mono_id_types then
+ -- Unlifted bindings must be non-recursive,
+ -- not top level, and non-polymorphic
+ checkTc (case top_lvl of {TopLevel -> False; NotTopLevel -> True})
+ (unliftedBindErr "Top-level" mbind) `thenTc_`
+ checkTc (case is_rec of {Recursive -> False; NonRecursive -> True})
+ (unliftedBindErr "Recursive" mbind) `thenTc_`
+ checkTc (null real_tyvars_to_gen_list)
+ (unliftedBindErr "Polymorphic" mbind)
+ else
+ returnTc ()
+ ) `thenTc_`
+
+ ASSERT( not (any ((== unboxedTypeKind) . tyVarKind) real_tyvars_to_gen_list) )
+ -- The instCantBeGeneralised stuff in tcSimplify should have
+ -- already raised an error if we're trying to generalise an
+ -- unboxed tyvar (NB: unboxed tyvars are always introduced
+ -- along with a class constraint) and it's better done there
+ -- because we have more precise origin information.
+ -- That's why we just use an ASSERT here.
+
+
+ -- BUILD THE POLYMORPHIC RESULT IDs
+ mapNF_Tc zonkId mono_ids `thenNF_Tc` \ zonked_mono_ids ->
+ let
+ exports = zipWith mk_export binder_names zonked_mono_ids
+ dict_tys = map tcIdType dicts_bound
+
+ mk_export binder_name zonked_mono_id
+ = (tyvars,
+ TcId (setIdInfo poly_id (prag_info_fn binder_name)),
+ TcId 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_list, new_poly_id)
+
+ new_poly_id = mkUserId binder_name poly_ty
+ poly_ty = mkForAllTys real_tyvars_to_gen_list
+ $ mkFunTys dict_tys
+ $ idType (zonked_mono_id)
+ -- It's important to build a fully-zonked poly_ty, because
+ -- we'll slurp out its free type variables when extending the
+ -- local environment (tcExtendLocalValEnv); if it's not zonked
+ -- it appears to have free tyvars that aren't actually free
+ -- at all.
+
+ pat_binders :: [Name]
+ pat_binders = map fst $ bagToList $ collectMonoBinders $
+ (justPatBindings mbind EmptyMonoBinds)
+ in
+ -- CHECK FOR UNBOXED BINDERS IN PATTERN BINDINGS
+ mapTc (\id -> checkTc (not (idName id `elem` pat_binders
+ && isUnboxedType (idType id)))
+ (unboxedPatBindErr id)) zonked_mono_ids
+ `thenTc_`
+
+ -- BUILD RESULTS
+ returnTc (
+ AbsBinds real_tyvars_to_gen_list
+ dicts_bound
+ exports
+ (dict_binds `andMonoBinds` mbind'),
+ lie_free,
+ [poly_id | (_, TcId poly_id, _) <- exports]
+ )
+ where
+ tysig_names = [name | (TySigInfo name _ _ _ _ _ _ _) <- tc_ty_sigs]
+ is_unrestricted = isUnRestrictedGroup tysig_names mbind
+
+justPatBindings bind@(PatMonoBind _ _ _) binds = bind `andMonoBinds` binds
+justPatBindings (AndMonoBinds b1 b2) binds =
+ justPatBindings b1 (justPatBindings b2 binds)
+justPatBindings other_bind binds = binds
\end{code}
-\begin{code}
-tcBind :: Bool -> E
- -> RenamedBind -> [RenamedSig]
- -> TcM (TypecheckedBinds, LIE, LVE) -- LIE is a fixed point of substitution
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
-tcBind False e bind sigs -- Not top level
- = tcBind_help False e bind sigs
+ * 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.
-tcBind True e bind sigs -- Top level!
- = pruneSubstTc (tvOfE e) (
+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:
- -- DO THE WORK
- tcBind_help True e bind sigs `thenTc` \ (new_binds, lie, lve) ->
+ f :: Eq a => [a] -> [a]
+ f xs = ...f...
-{- Top-level unboxed values are now allowed
- They will be lifted by the Desugarer (see CoreLift.lhs)
+If we don't take care, after typechecking we get
- -- CHECK FOR PRIMITIVE TOP-LEVEL BINDS
- listTc [ checkTc (isUnboxedDataType (getIdUniType id))
- (topLevelUnboxedDeclErr id (getSrcLoc id))
- | (_,id) <- lve ] `thenTc_`
--}
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
- -- Back-substitute over the binds, since we are about to discard
- -- a good chunk of the substitution.
- applyTcSubstToBinds new_binds `thenNF_Tc` \ final_binds ->
+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
- -- The lie is already a fixed point of the substitution; it just turns out
- -- that almost always this happens automatically, and so we made it part of
- -- the specification of genBinds.
- returnTc (final_binds, lie, lve)
- )
-\end{code}
+ f = /\a -> \d::Eq a -> letrec
+ fm = \ys:[a] -> ...fm...
+ in
+ fm
-\begin{code}
-tcBind_help top_level e bind sigs
- = -- Create an LVE binding each identifier to an appropriate type variable
- new_locals binders `thenNF_Tc` \ bound_ids ->
- let lve = binders `zip` bound_ids in
-
- -- Now deal with type signatures, if any
- tcSigs e lve sigs `thenTc` \ sig_info ->
-
- -- Check the bindings: this is the point at which we can use
- -- error recovery. If checking the bind fails we just
- -- return the empty bindings. The variables will still be in
- -- scope, but bound to completely free type variables, which
- -- is just what we want to minimise subsequent error messages.
- recoverTc (NonRecBind EmptyMonoBinds, nullLIE)
- (tc_bind (growE_LVE e lve) bind) `thenNF_Tc` \ (bind', lie) ->
-
- -- Notice that genBinds gets the old (non-extended) environment
- genBinds top_level e bind' lie lve sig_info `thenTc` \ (binds', lie, lve) ->
-
- -- Add bindings corresponding to SPECIALIZE pragmas in the code
- mapAndUnzipTc (doSpecPragma e lve) (get_spec_pragmas sig_info)
- `thenTc` \ (spec_binds_s, spec_lie_s) ->
-
- returnTc (binds' `ThenBinds` (SingleBind (NonRecBind (
- foldr AndMonoBinds EmptyMonoBinds spec_binds_s))),
- lie `plusLIE` (foldr plusLIE nullLIE spec_lie_s),
- lve)
- where
- binders = collectBinders bind
+This can lead to a massive space leak, from the following top-level defn
+(post-typechecking)
- new_locals binders
- = case bind of
- NonRecBind _ -> -- Recursive, so no unboxed types
- newLocalsWithOpenTyVarTys binders
+ ff :: [Int] -> [Int]
+ ff = f Int dEqInt
- RecBind _ -> -- Non-recursive, so we permit unboxed types
- newLocalsWithPolyTyVarTys binders
+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.
- get_spec_pragmas sig_info
- = catMaybes (map get_pragma_maybe sig_info)
- where
- get_pragma_maybe s@(ValSpecInfo _ _ _ _) = Just s
- get_pragma_maybe _ = Nothing
-\end{code}
+ ff = f Int dEqInt
-\begin{verbatim}
- f :: Ord a => [a] -> b -> b
- {-# SPECIALIZE f :: [Int] -> b -> b #-}
-\end{verbatim}
-We generate:
-\begin{verbatim}
- f@Int = /\ b -> let d1 = ...
- in f Int b d1
+ = let f' = f Int dEqInt in \ys. ...f'...
+ = let f' = let f' = f Int dEqInt in \ys. ...f'...
+ in \ys. ...f'...
- h :: Ord a => [a] -> b -> b
- {-# SPECIALIZE h :: [Int] -> b -> b #-}
+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.
- spec_h = /\b -> h [Int] b dListOfInt
- ^^^^^^^^^^^^^^^^^^^^ This bit created by specId
-\end{verbatim}
+
+%************************************************************************
+%* *
+\subsection{getTyVarsToGen}
+%* *
+%************************************************************************
+
+@getTyVarsToGen@ decides what type variables generalise over.
+
+For a "restricted group" -- see the monomorphism restriction
+for a definition -- we bind no dictionaries, and
+remove from tyvars_to_gen any constrained type variables
+
+*Don't* simplify dicts at this point, because we aren't going
+to generalise over these dicts. By the time we do simplify them
+we may well know more. For example (this actually came up)
+ f :: Array Int Int
+ f x = array ... xs where xs = [1,2,3,4,5]
+We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
+stuff. If we simplify only at the f-binding (not the xs-binding)
+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:
+
+ (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:
+ instance Eq a => Eq (Foo a b) where ..
+ Here, b is not constrained, even though it looks as if it is.
+ Another, more common, example is when there's a Method inst in
+ the LIE, whose type might very well involve non-overloaded
+ type variables.
+
+ (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.
+
+So we are careful, and do a complete simplification just to find the
+constrained tyvars. We don't use any of the results, except to
+find which tyvars are constrained.
\begin{code}
-doSpecPragma :: E -> LVE
- -> SignatureInfo
- -> TcM (TypecheckedMonoBinds, LIE)
-
-doSpecPragma e lve (ValSpecInfo name spec_ty using src_loc)
- = let
- main_id = assoc "doSpecPragma" lve name
- -- Get the parent Id; it should exist (renamer promises...).
-
- main_id_ty = getIdUniType main_id
- main_id_free_tyvars = extractTyVarsFromTy main_id_ty
- origin = ValSpecOrigin name src_loc
- err_ctxt = ValSpecSigCtxt name spec_ty src_loc
+getTyVarsToGen is_unrestricted mono_id_tys lie
+ = tcGetGlobalTyVars `thenNF_Tc` \ free_tyvars ->
+ zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_tys ->
+ let
+ tyvars_to_gen = tyVarsOfTypes zonked_mono_id_tys `minusVarSet` free_tyvars
in
- addSrcLocTc src_loc (
- specTy origin spec_ty `thenNF_Tc` \ (spec_tyvars, spec_dicts, spec_tau) ->
-
- -- Check that the SPECIALIZE pragma had an empty context
- checkTc (not (null spec_dicts))
- (panic "SPECIALIZE non-empty context (ToDo: msg)") `thenTc_`
-
- -- Make an instance of this id
- specTy origin main_id_ty `thenNF_Tc` \ (main_tyvars, main_dicts, main_tau) ->
-
- -- Check that the specialised type is indeed an instance of
- -- the inferred type.
- -- The unification should leave all type vars which are
- -- currently free in the environment still free, and likewise
- -- the signature type vars.
- -- The only way type vars free in the envt could possibly be affected
- -- is if main_id_ty has free type variables. So we just extract them,
- -- and check that they are not constrained in any way by the unification.
- applyTcSubstAndCollectTyVars main_id_free_tyvars `thenNF_Tc` \ free_tyvars' ->
- unifyTauTy spec_tau main_tau err_ctxt `thenTc_`
- checkSigTyVars [] (spec_tyvars ++ free_tyvars')
- spec_tau main_tau err_ctxt `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
- applyTcSubstToTyVars main_tyvars `thenNF_Tc` \ main_arg_tys ->
- applyTcSubstToInsts main_dicts `thenNF_Tc` \ main_dicts' ->
-
- checkTc (not (all isGroundOrTyVarTy main_arg_tys))
- (specGroundnessErr err_ctxt main_arg_tys)
- `thenTc_`
-
- checkTc (not (and [isGroundTy ty | (_,ty) <- map getDictClassAndType main_dicts']))
- (specCtxtGroundnessErr err_ctxt main_dicts')
- `thenTc_`
-
- -- Build a suitable binding; depending on whether we were given
- -- a value (Maybe Name) to be used as the specialisation.
- case using of
- Nothing ->
-
- -- Make a specPragmaId to which to bind the new call-instance
- newSpecPragmaId name spec_ty Nothing
- `thenNF_Tc` \ pseudo_spec_id ->
+ if is_unrestricted
+ then
+ returnNF_Tc (emptyVarSet, tyvars_to_gen)
+ else
+ -- This recover and discard-errs is to avoid duplicate error
+ -- messages; this, after all, is an "extra" call to tcSimplify
+ recoverNF_Tc (returnNF_Tc (emptyVarSet, tyvars_to_gen)) $
+ discardErrsTc $
+
+ tcSimplify (text "getTVG") NotTopLevel tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
let
- pseudo_bind = VarMonoBind pseudo_spec_id pseudo_rhs
- pseudo_rhs = mkTyLam spec_tyvars (mkDictApp (mkTyApp (Var main_id) main_arg_tys)
- (map mkInstId main_dicts'))
- in
- returnTc (pseudo_bind, mkLIE main_dicts')
+ -- ASSERT: dicts_sig is already zonked!
+ constrained_tyvars = foldrBag (unionVarSet . tyVarsOfInst) emptyVarSet constrained_dicts
+ reduced_tyvars_to_gen = tyvars_to_gen `minusVarSet` constrained_tyvars
+ in
+ returnTc (constrained_tyvars, reduced_tyvars_to_gen)
+\end{code}
- Just spec_name -> -- use spec_name as the specialisation value ...
- let
- spec_id = lookupE_Value e spec_name
- spec_id_ty = getIdUniType spec_id
- spec_id_free_tyvars = extractTyVarsFromTy spec_id_ty
- spec_id_ctxt = ValSpecSpecIdCtxt name spec_ty spec_name src_loc
+\begin{code}
+isUnRestrictedGroup :: [Name] -- Signatures given for these
+ -> RenamedMonoBinds
+ -> Bool
+
+is_elem v vs = isIn "isUnResMono" v vs
+
+isUnRestrictedGroup sigs (PatMonoBind (VarPatIn v) _ _) = v `is_elem` sigs
+isUnRestrictedGroup sigs (PatMonoBind other _ _) = False
+isUnRestrictedGroup sigs (VarMonoBind v _) = v `is_elem` sigs
+isUnRestrictedGroup sigs (FunMonoBind _ _ _ _) = True
+isUnRestrictedGroup sigs (AndMonoBinds mb1 mb2) = isUnRestrictedGroup sigs mb1 &&
+ isUnRestrictedGroup sigs mb2
+isUnRestrictedGroup sigs EmptyMonoBinds = True
+\end{code}
+
+@defaultUncommittedTyVar@ checks for generalisation over unboxed
+types, and defaults any TypeKind TyVars to BoxedTypeKind.
+
+\begin{code}
+defaultUncommittedTyVar tyvar
+ | tyVarKind tyvar == openTypeKind
+ = newTcTyVar boxedTypeKind `thenNF_Tc` \ boxed_tyvar ->
+ unifyTauTy (mkTyVarTy tyvar) (mkTyVarTy boxed_tyvar) `thenTc_`
+ returnTc boxed_tyvar
+
+ | otherwise
+ = returnTc tyvar
+\end{code}
- spec_tys = map maybe_ty main_arg_tys
- maybe_ty ty | isTyVarTy ty = Nothing
- | otherwise = Just ty
+
+%************************************************************************
+%* *
+\subsection{tcMonoBind}
+%* *
+%************************************************************************
+
+@tcMonoBinds@ deals with a single @MonoBind@.
+The signatures have been dealt with already.
+
+\begin{code}
+tcMonoBinds :: RenamedMonoBinds
+ -> [TcSigInfo s]
+ -> RecFlag
+ -> TcM s (TcMonoBinds s,
+ LIE s, -- LIE required
+ [Name], -- Bound names
+ [TcIdBndr s]) -- Corresponding monomorphic bound things
+
+tcMonoBinds mbinds tc_ty_sigs is_rec
+ = tc_mb_pats mbinds `thenTc` \ (complete_it, lie_req_pat, tvs, ids, lie_avail) ->
+ let
+ tv_list = bagToList tvs
+ (names, mono_ids) = unzip (bagToList ids)
+ 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.
+ tcExtendEnvWithPat ids (tcExtendEnvWithPat sig_ids
+ complete_it
+ ) `thenTc` \ (mbinds', lie_req_rhss) ->
+ returnTc (mbinds', lie_req_pat `plusLIE` lie_req_rhss, names, mono_ids)
+ where
+ sig_fn name = case maybeSig tc_ty_sigs name of
+ Nothing -> Nothing
+ Just (TySigInfo _ _ _ _ _ mono_id _ _) -> Just mono_id
+
+ sig_ids = listToBag [(name,poly_id) | TySigInfo name poly_id _ _ _ _ _ _ <- tc_ty_sigs]
+
+ kind = case is_rec of
+ Recursive -> boxedTypeKind -- Recursive, so no unboxed types
+ NonRecursive -> openTypeKind -- Non-recursive, so we permit unboxed types
+
+ tc_mb_pats EmptyMonoBinds
+ = returnTc (returnTc (EmptyMonoBinds, emptyLIE), emptyLIE, emptyBag, emptyBag, emptyLIE)
+
+ tc_mb_pats (AndMonoBinds mb1 mb2)
+ = tc_mb_pats mb1 `thenTc` \ (complete_it1, lie_req1, tvs1, ids1, lie_avail1) ->
+ tc_mb_pats mb2 `thenTc` \ (complete_it2, lie_req2, tvs2, ids2, lie_avail2) ->
+ let
+ complete_it = complete_it1 `thenTc` \ (mb1', lie1) ->
+ complete_it2 `thenTc` \ (mb2', lie2) ->
+ returnTc (AndMonoBinds mb1' mb2', lie1 `plusLIE` lie2)
in
- -- Make an instance of the spec_id
- specTy origin spec_id_ty `thenNF_Tc` \ (spec_id_tyvars, spec_id_dicts, spec_id_tau) ->
-
- -- Check that the specialised type is indeed an instance of
- -- the type inferred for spec_id
- -- The unification should leave all type vars which are
- -- currently free in the environment still free, and likewise
- -- the signature type vars.
- -- The only way type vars free in the envt could possibly be affected
- -- is if spec_id_ty has free type variables. So we just extract them,
- -- and check that they are not constrained in any way by the unification.
- applyTcSubstAndCollectTyVars spec_id_free_tyvars `thenNF_Tc` \ spec_id_free_tyvars' ->
- unifyTauTy spec_tau spec_id_tau spec_id_ctxt `thenTc_`
- checkSigTyVars [] (spec_tyvars ++ spec_id_free_tyvars')
- spec_tau spec_id_tau spec_id_ctxt `thenTc_`
-
- -- Check that the type variables of the explicit spec_id 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
- applyTcSubstToTyVars spec_id_tyvars `thenNF_Tc` \ spec_id_arg_tys ->
- applyTcSubstToInsts spec_id_dicts `thenNF_Tc` \ spec_id_dicts' ->
-
- checkTc (not (all isGroundOrTyVarTy spec_id_arg_tys))
- (specGroundnessErr spec_id_ctxt spec_id_arg_tys)
- `thenTc_`
-
- checkTc (not (and [isGroundTy ty | (_,ty) <- map getDictClassAndType spec_id_dicts']))
- (specCtxtGroundnessErr spec_id_ctxt spec_id_dicts')
- `thenTc_`
-
- -- Make a local SpecId to bind to applied spec_id
- newSpecId main_id spec_tys spec_ty `thenNF_Tc` \ local_spec_id ->
-
- -- Make a specPragmaId id with a spec_info for local_spec_id
- -- This is bound to local_spec_id
- -- The SpecInfo will be extracted by the specialiser and
- -- used to create a call instance for main_id (which is
- -- extracted from the spec_id)
- -- NB: the pseudo_local_id must stay in the scope of main_id !!!
+ 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 boxedTypeKind `thenNF_Tc` \ pat_ty ->
+ tcVarPat sig_fn name pat_ty `thenTc` \ bndr_id ->
let
- spec_info = SpecInfo spec_tys (length main_dicts') local_spec_id
+ complete_it = tcAddSrcLoc locn $
+ tcMatchesFun name pat_ty matches `thenTc` \ (matches', lie) ->
+ returnTc (FunMonoBind (TcId bndr_id) inf matches' locn, lie)
in
- newSpecPragmaId name spec_ty (Just spec_info) `thenNF_Tc` \ pseudo_spec_id ->
+ returnTc (complete_it, emptyLIE, emptyBag, unitBag (name, bndr_id), emptyLIE)
+
+ tc_mb_pats bind@(PatMonoBind pat grhss_and_binds locn)
+ = tcAddSrcLoc locn $
+ newTyVarTy kind `thenNF_Tc` \ pat_ty ->
+ tcPat sig_fn pat pat_ty `thenTc` \ (pat', lie_req, tvs, ids, lie_avail) ->
let
- spec_bind = VarMonoBind local_spec_id spec_rhs
- spec_rhs = mkTyLam spec_tyvars (mkDictApp (mkTyApp (Var spec_id) spec_id_arg_tys)
- (map mkInstId spec_id_dicts'))
- pseudo_bind = VarMonoBind pseudo_spec_id (Var local_spec_id)
+ complete_it = tcAddSrcLoc locn $
+ tcAddErrCtxt (patMonoBindsCtxt bind) $
+ tcGRHSsAndBinds grhss_and_binds pat_ty PatBindRhs `thenTc` \ (grhss_and_binds', lie) ->
+ returnTc (PatMonoBind pat' grhss_and_binds' locn, lie)
in
- returnTc (spec_bind `AndMonoBinds` pseudo_bind, mkLIE spec_id_dicts')
- )
+ returnTc (complete_it, lie_req, tvs, ids, lie_avail)
\end{code}
-\begin{code}
-tc_bind :: E
- -> RenamedBind
- -> TcM (TypecheckedBind, LIE)
+%************************************************************************
+%* *
+\subsection{Signatures}
+%* *
+%************************************************************************
-tc_bind e (NonRecBind mono_binds)
- = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (NonRecBind mono_binds2, lie)
+@checkSigMatch@ does the next step in checking signature matching.
+The tau-type part has already been unified. What we do here is to
+check that this unification has not over-constrained the (polymorphic)
+type variables of the original signature type.
-tc_bind e (RecBind mono_binds)
- = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (RecBind mono_binds2, lie)
-\end{code}
+The error message here is somewhat unsatisfactory, but it'll do for
+now (ToDo).
\begin{code}
-specialiseBinds
- :: [Id] -- Ids bound in this group
- -> LIE -- LIE of scope of these bindings
- -> TypecheckedBinds
- -> LIE
- -> NF_TcM (TypecheckedBinds, LIE)
-
-specialiseBinds bound_ids lie_of_scope poly_binds poly_lie
- = bindInstsOfLocalFuns lie_of_scope bound_ids
- `thenNF_Tc` \ (lie2, inst_mbinds) ->
-
- returnNF_Tc (poly_binds `ThenBinds` (SingleBind (NonRecBind inst_mbinds)),
- lie2 `plusLIE` poly_lie)
+checkSigMatch []
+ = returnTc (error "checkSigMatch", emptyLIE)
+
+checkSigMatch tc_ty_sigs@( sig1@(TySigInfo _ id1 _ theta1 _ _ _ _) : all_sigs_but_first )
+ = -- CHECK THAT THE SIGNATURE TYVARS AND TAU_TYPES ARE OK
+ -- Doesn't affect substitution
+ mapTc check_one_sig tc_ty_sigs `thenTc_`
+
+ -- 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
+ mapTc check_one_cxt all_sigs_but_first `thenTc_`
+
+ returnTc (theta1, sig_lie)
+ where
+ sig1_dict_tys = mk_dict_tys theta1
+ n_sig1_dict_tys = length sig1_dict_tys
+ sig_lie = mkLIE [inst | TySigInfo _ _ _ _ _ _ inst _ <- tc_ty_sigs]
+
+ check_one_cxt sig@(TySigInfo _ id _ theta _ _ _ src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (sigContextsCtxt id1 id) $
+ checkTc (length this_sig_dict_tys == n_sig1_dict_tys)
+ sigContextsErr `thenTc_`
+ unifyTauTyLists sig1_dict_tys this_sig_dict_tys
+ where
+ this_sig_dict_tys = mk_dict_tys theta
+
+ check_one_sig (TySigInfo _ id sig_tyvars _ sig_tau _ _ src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxtM (sigCtxt (quotes (ppr id)) sig_tau) $
+ checkSigTyVars sig_tyvars
+
+ mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta]
\end{code}
+
%************************************************************************
%* *
-\subsection{Signatures}
+\subsection{SPECIALIZE pragmas}
%* *
%************************************************************************
-@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 (not @TyVarTemplate@s)
-installed.
+
+@tcPragmaSigs@ munches up the "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}
-tcSigs :: E -> LVE
- -> [RenamedSig]
- -> TcM [SignatureInfo]
+tcPragmaSigs :: [RenamedSig] -- The pragma signatures
+ -> TcM s (Name -> IdInfo, -- Maps name to the appropriate IdInfo
+ TcMonoBinds s,
+ LIE s)
-tcSigs e lve [] = returnTc []
+tcPragmaSigs sigs
+ = mapAndUnzip3Tc tcPragmaSig sigs `thenTc` \ (maybe_info_modifiers, binds, lies) ->
+ let
+ prag_fn name = foldr ($) noIdInfo [f | Just (n,f) <- maybe_info_modifiers, n==name]
+ in
+ returnTc (prag_fn, andMonoBindList binds, plusLIEs lies)
+\end{code}
-tcSigs e lve (s:ss)
- = tc_sig s `thenTc` \ sig_info1 ->
- tcSigs e lve ss `thenTc` \ sig_info2 ->
- returnTc (sig_info1 : sig_info2)
- where
- tc_sig (Sig v ty _ src_loc) -- no interesting pragmas on non-iface sigs
- = addSrcLocTc src_loc (
+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 #-}
+\end{verbatim}
- babyTcMtoTcM
- (tcPolyType (getE_CE e) (getE_TCE e) nullTVE ty) `thenTc` \ sigma_ty ->
+For this we generate:
+\begin{verbatim}
+ f* = /\ b -> let d1 = ...
+ in f Int b d1
+\end{verbatim}
+
+where f* is a SpecPragmaId. The **sole** purpose of SpecPragmaIds is to
+retain a right-hand-side that the simplifier will otherwise discard as
+dead code... the simplifier has a flag that tells it not to discard
+SpecPragmaId bindings.
+
+In this case the f* retains a call-instance of the overloaded
+function, f, (including appropriate dictionaries) so that the
+specialiser will subsequently discover that there's a call of @f@ at
+Int, and will create a specialisation for @f@. After that, the
+binding for @f*@ can be discarded.
- let val = assoc "tcSigs" lve v in
- -- (The renamer/dependency-analyser should have ensured
- -- that there are only signatures for which there is a
- -- corresponding binding.)
+The second form is this:
+\begin{verbatim}
+ f :: Ord a => [a] -> b -> b
+ {-# SPECIALIZE f :: [Int] -> b -> b = g #-}
+\end{verbatim}
- -- Instantiate the type, and unify with the type variable
- -- found in the Id.
- specTy SignatureOrigin sigma_ty `thenNF_Tc` \ (tyvars, dicts, tau_ty) ->
- unifyTauTy (getIdUniType val) tau_ty
- (panic "ToDo: unifyTauTy(tcSigs)") `thenTc_`
+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}
- returnTc (TySigInfo val tyvars dicts tau_ty src_loc)
- )
+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.
- tc_sig (SpecSig v ty using src_loc)
- = addSrcLocTc src_loc (
+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.
- babyTcMtoTcM
- (tcPolyType (getE_CE e) (getE_TCE e) nullTVE ty) `thenTc` \ sigma_ty ->
+\begin{code}
+tcPragmaSig :: RenamedSig -> TcM s (Maybe (Name, IdInfo -> IdInfo), TcMonoBinds s, LIE s)
+tcPragmaSig (Sig _ _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+tcPragmaSig (SpecInstSig _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (InlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IWantToBeINLINEd), EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (NoInlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IMustNotBeINLINEd), EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
+ = -- SPECIALISE f :: forall b. theta => tau = g
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
+
+ -- Get and instantiate its alleged specialised type
+ tcHsTcType poly_ty `thenTc` \ sig_ty ->
+
+ -- Check that f has a more general type, and build a RHS for
+ -- the spec-pragma-id at the same time
+ tcExpr (HsVar name) sig_ty `thenTc` \ (spec_expr, spec_lie) ->
+
+ case maybe_spec_name of
+ Nothing -> -- Just specialise "f" by building a SpecPragmaId binding
+ -- It is the thing that makes sure we don't prematurely
+ -- dead-code-eliminate the binding we are really interested in.
+ newSpecPragmaId name sig_ty `thenNF_Tc` \ spec_id ->
+ returnTc (Nothing, VarMonoBind (TcId spec_id) spec_expr, spec_lie)
+
+ Just g_name -> -- Don't create a SpecPragmaId. Instead add some suitable IdIfo
+
+ panic "Can't handle SPECIALISE with a '= g' part"
+
+ {- Not yet. Because we're still in the TcType world we
+ can't really add to the SpecEnv of the Id. Instead we have to
+ record the information in a different sort of Sig, and add it to
+ the IdInfo after zonking.
+
+ For now we just leave out this case
+
+ -- Get the type of f, and find out what types
+ -- f has to be instantiated at to give the signature type
+ tcLookupLocalValueOK "tcPragmaSig" name `thenNF_Tc` \ f_id ->
+ tcInstTcType (idType f_id) `thenNF_Tc` \ (f_tyvars, f_rho) ->
+
+ let
+ (sig_tyvars, sig_theta, sig_tau) = splitSigmaTy sig_ty
+ (f_theta, f_tau) = splitRhoTy f_rho
+ sig_tyvar_set = mkVarSet sig_tyvars
+ in
+ unifyTauTy sig_tau f_tau `thenTc_`
+
+ tcPolyExpr str (HsVar g_name) (mkSigmaTy sig_tyvars f_theta sig_tau) `thenTc` \ (_, _,
+ -}
+
+tcPragmaSig other = pprTrace "tcPragmaSig: ignoring" (ppr other) $
+ returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+\end{code}
- returnTc (ValSpecInfo v sigma_ty using src_loc)
- )
- tc_sig (InlineSig v guide locn)
- = returnTc (ValInlineInfo v guide locn)
+%************************************************************************
+%* *
+\subsection[TcBinds-errors]{Error contexts and messages}
+%* *
+%************************************************************************
- tc_sig (DeforestSig v locn)
- = returnTc (ValDeforestInfo v locn)
- tc_sig (MagicUnfoldingSig v str locn)
- = returnTc (ValMagicUnfoldingInfo v str locn)
+\begin{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 <+> ptext SLIT(" ::") <+> ppr ty)]
+
+-----------------------------------------------
+notAsPolyAsSigErr sig_tau mono_tyvars
+ = hang (ptext SLIT("A type signature is more polymorphic than the inferred type"))
+ 4 (vcat [text "Can't for-all the type variable(s)" <+>
+ pprQuotedList mono_tyvars,
+ text "in the type" <+> quotes (ppr sig_tau)
+ ])
+
+-----------------------------------------------
+badMatchErr sig_ty inferred_ty
+ = hang (ptext SLIT("Type signature doesn't match inferred type"))
+ 4 (vcat [hang (ptext SLIT("Signature:")) 4 (ppr sig_ty),
+ hang (ptext SLIT("Inferred :")) 4 (ppr inferred_ty)
+ ])
+
+-----------------------------------------------
+unboxedPatBindErr id
+ = ptext SLIT("variable in a lazy pattern binding has unboxed type: ")
+ <+> quotes (ppr id)
+
+-----------------------------------------------
+bindSigsCtxt ids
+ = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
+
+-----------------------------------------------
+sigContextsErr
+ = ptext SLIT("Mismatched contexts")
+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)"))
+
+-----------------------------------------------
+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)
\end{code}
projects / ghc-hetmet.git / blobdiff