%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1995
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
%
\section[TcBinds]{TcBinds}
\begin{code}
-#include "HsVersions.h"
+module TcBinds ( tcBindsAndThen, tcTopBindsAndThen, bindInstsOfLocalFuns,
+ tcPragmaSigs, checkSigTyVars, tcBindWithSigs,
+ sigCtxt, TcSigInfo(..) ) where
-module TcBinds (
- tcTopBindsAndThen, tcLocalBindsAndThen,
- tcSigs, doSpecPragma
- ) 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(..),
+ collectMonoBinders, andMonoBinds
+ )
+import RnHsSyn ( RenamedHsBinds, RenamedSig, RenamedMonoBinds )
+import TcHsSyn ( TcHsBinds, TcMonoBinds,
+ TcIdOcc(..), TcIdBndr,
+ tcIdType
)
-import AbsSyn -- the stuff being typechecked
-import AbsUniType ( isTyVarTy, isGroundTy, isUnboxedDataType,
- isGroundOrTyVarTy, extractTyVarsFromTy,
- UniType
+import TcMonad
+import Inst ( Inst, LIE, emptyLIE, plusLIE, plusLIEs, InstOrigin(..),
+ newDicts, tyVarsOfInst, instToId, newMethodWithGivenTy,
+ zonkInst, pprInsts
)
-import BackSubst ( applyTcSubstToBinds )
-import E
-import Errors ( topLevelUnboxedDeclErr, specGroundnessErr,
- specCtxtGroundnessErr, Error(..), UnifyErrContext(..)
+import TcEnv ( tcExtendLocalValEnv, tcLookupLocalValueOK,
+ newLocalId, 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 ( tcHsType )
+import TcPat ( tcPat )
import TcSimplify ( bindInstsOfLocalFuns )
-import Unify ( unifyTauTy )
-import UniqFM ( emptyUFM ) -- profiling, pragmas only
-import Util
+import TcType ( TcType, TcThetaType, TcTauType,
+ TcTyVarSet, TcTyVar,
+ newTyVarTy, newTcTyVar, tcInstSigType, tcInstSigTcType,
+ zonkTcType, zonkTcTypes, zonkTcThetaType, zonkTcTyVar
+ )
+import Unify ( unifyTauTy, unifyTauTyLists )
+
+import Kind ( isUnboxedTypeKind, mkTypeKind, isTypeKind, mkBoxedTypeKind )
+import MkId ( mkUserId )
+import Id ( idType, idName, idInfo, replaceIdInfo )
+import IdInfo ( IdInfo, noIdInfo, setInlinePragInfo, InlinePragInfo(..) )
+import Maybes ( maybeToBool, assocMaybe )
+import Name ( getOccName, getSrcLoc, Name )
+import Type ( mkTyVarTy, mkTyVarTys, isTyVarTy, tyVarsOfTypes,
+ splitSigmaTy, mkForAllTys, mkFunTys, getTyVar, mkDictTy,
+ splitRhoTy, mkForAllTy, splitForAllTys
+ )
+import TyVar ( TyVar, tyVarKind, mkTyVarSet, minusTyVarSet, emptyTyVarSet,
+ elementOfTyVarSet, unionTyVarSets, tyVarSetToList
+ )
+import Bag ( bagToList, foldrBag, )
+import Util ( isIn, hasNoDups, assoc )
+import Unique ( Unique )
+import BasicTypes ( TopLevelFlag(..), RecFlag(..) )
+import SrcLoc ( SrcLoc )
+import Outputable
\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 -> this -> that) -- Combinator
+ -> RenamedHsBinds
+ -> TcM s (this, LIE s)
+ -> TcM s (that, LIE s)
+
+tcTopBindsAndThen = tc_binds_and_then TopLevel
+tcBindsAndThen = tc_binds_and_then NotTopLevel
+
+tc_binds_and_then top_lvl combiner binds do_next
+ = tcBinds top_lvl binds `thenTc` \ (mbinds1, binds_lie, env, ids) ->
+ tcSetEnv env $
+
+ -- Now do whatever happens next, in the augmented envt
+ do_next `thenTc` \ (thing, thing_lie) ->
+
+ -- Create specialisations of functions bound here
+ -- Nota Bene: we glom the bindings all together in a single
+ -- recursive group ("recursive" passed to combiner, below)
+ -- so that we can do thsi bindInsts thing once for all the bindings
+ -- and the thing inside. This saves a quadratic-cost algorithm
+ -- when there's a long sequence of bindings.
+ bindInstsOfLocalFuns (binds_lie `plusLIE` thing_lie) ids `thenTc` \ (final_lie, mbinds2) ->
+
+ -- All done
+ let
+ final_mbinds = mbinds1 `AndMonoBinds` mbinds2
+ in
+ returnTc (combiner Recursive final_mbinds thing, final_lie)
+
+tcBinds :: TopLevelFlag
+ -> RenamedHsBinds
+ -> TcM s (TcMonoBinds s, LIE s, TcEnv s, [TcIdBndr s])
+ -- The envt is the envt with binders in scope
+ -- The binders are those bound by this group of bindings
+
+tcBinds top_lvl EmptyBinds
+ = tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (EmptyMonoBinds, emptyLIE, env, [])
+
+ -- Short-cut for the rather common case of an empty bunch of bindings
+tcBinds top_lvl (MonoBind EmptyMonoBinds sigs is_rec)
+ = tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (EmptyMonoBinds, emptyLIE, env, [])
+
+tcBinds top_lvl (ThenBinds binds1 binds2)
+ = tcBinds top_lvl binds1 `thenTc` \ (mbinds1, lie1, env1, ids1) ->
+ tcSetEnv env1 $
+ tcBinds top_lvl binds2 `thenTc` \ (mbinds2, lie2, env2, ids2) ->
+ returnTc (mbinds1 `AndMonoBinds` mbinds2, lie1 `plusLIE` lie2, env2, ids1++ids2)
+
+tcBinds top_lvl (MonoBind bind sigs is_rec)
+ = fixTc (\ ~(prag_info_fn, _) ->
+ -- This is the usual prag_info fix; the PragmaInfo field of an Id
+ -- is not inspected till ages later in the compiler, so there
+ -- should be no black-hole problems here.
+
+ -- TYPECHECK THE SIGNATURES
+ mapTc tcTySig ty_sigs `thenTc` \ tc_ty_sigs ->
+
+ tcBindWithSigs top_lvl binder_names bind
+ tc_ty_sigs is_rec prag_info_fn `thenTc` \ (poly_binds, poly_lie, poly_ids) ->
+
+ -- Extend the environment to bind the new polymorphic Ids
+ tcExtendLocalValEnv binder_names poly_ids $
+
+ -- Build bindings and IdInfos corresponding to user pragmas
+ tcPragmaSigs sigs `thenTc` \ (prag_info_fn, prag_binds, prag_lie) ->
+
+ -- Catch the environment and return
+ tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (prag_info_fn, (poly_binds `AndMonoBinds` prag_binds,
+ poly_lie `plusLIE` prag_lie,
+ env, poly_ids)
+ ) ) `thenTc` \ (_, result) ->
+ returnTc result
+ where
+ binder_names = map fst (bagToList (collectMonoBinders bind))
+ ty_sigs = [sig | sig@(Sig name _ _) <- sigs]
\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
+ :: RenamedHsBinds
+ -> TcM s (thing, LIE s, thing_ty))
+ -> TcM s ((TcHsBinds s, thing), LIE s, thing_ty)
-tcBindsAndThen top_level e EmptyBinds do_next
- = do_next e `thenTc` \ (thing, lie, thing_ty) ->
+tcBindsAndThen EmptyBinds do_next
+ = do_next `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
+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)
- 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 (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
+ -> [Name]
+ -> RenamedMonoBinds
+ -> [TcSigInfo s]
+ -> RecFlag
+ -> (Name -> IdInfo)
+ -> TcM s (TcMonoBinds s, LIE s, [TcIdBndr s])
+
+tcBindWithSigs top_lvl binder_names mbind tc_ty_sigs is_rec prag_info_fn
+ = recoverTc (
+ -- If typechecking the binds fails, then return with each
+ -- signature-less binder given type (forall a.a), to minimise subsequent
+ -- error messages
+ newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ alpha_tv ->
+ let
+ forall_a_a = mkForAllTy alpha_tv (mkTyVarTy alpha_tv)
+ 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)
+ ) $
+
+ -- Create a new identifier for each binder, with each being given
+ -- a fresh unique, and a type-variable type.
+ -- For "mono_lies" see comments about polymorphic recursion at the
+ -- end of the function.
+ mapAndUnzipNF_Tc mk_mono_id binder_names `thenNF_Tc` \ (mono_lies, mono_ids) ->
+ let
+ mono_lie = plusLIEs mono_lies
+ mono_id_tys = map idType mono_ids
+ in
- -- Now do whatever happens next, in the augmented envt
- do_next (growE_LVE e poly_lve) `thenTc` \ (thing, thing_lie, thing_ty) ->
+ -- TYPECHECK THE BINDINGS
+ tcMonoBinds mbind binder_names mono_ids tc_ty_sigs `thenTc` \ (mbind', lie) ->
+
+ -- CHECK THAT THE SIGNATURES MATCH
+ -- (must do this before getTyVarsToGen)
+ checkSigMatch tc_ty_sigs `thenTc` \ sig_theta ->
+
+ -- 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 `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 (tyVarSetToList tyvars_to_gen) `thenTc` \ real_tyvars_to_gen_list ->
let
- bound_ids = map snd poly_lve
+ real_tyvars_to_gen = mkTyVarSet real_tyvars_to_gen_list
+ -- It's important that the final list
+ -- (real_tyvars_to_gen and real_tyvars_to_gen_list) is fully
+ -- 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
- -- 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)
-\end{code}
-\begin{code}
-tcBind :: Bool -> E
- -> RenamedBind -> [RenamedSig]
- -> TcM (TypecheckedBinds, LIE, LVE) -- LIE is a fixed point of substitution
+ -- SIMPLIFY THE LIE
+ tcExtendGlobalTyVars (tyVarSetToList tyvars_not_to_gen) (
+ if null tc_ty_sigs then
+ -- No signatures, so just simplify the lie
+ -- NB: no signatures => no polymorphic recursion, so no
+ -- need to use mono_lies (which will be empty anyway)
+ tcSimplify (text "tcBinds1" <+> ppr binder_names)
+ top_lvl real_tyvars_to_gen lie `thenTc` \ (lie_free, dict_binds, lie_bound) ->
+ returnTc (lie_free, dict_binds, map instToId (bagToList lie_bound))
+
+ else
+ zonkTcThetaType sig_theta `thenNF_Tc` \ sig_theta' ->
+ newDicts SignatureOrigin sig_theta' `thenNF_Tc` \ (dicts_sig, dict_ids) ->
+ -- It's important that sig_theta is zonked, because
+ -- dict_id is later used to form the type of the polymorphic thing,
+ -- and forall-types must be zonked so far as their bound variables
+ -- are concerned
+
+ let
+ -- The "givens" is the stuff available. We get that from
+ -- the context of the type signature, BUT ALSO the mono_lie
+ -- so that polymorphic recursion works right (see comments at end of fn)
+ givens = dicts_sig `plusLIE` mono_lie
+ in
+
+ -- Check that the needed dicts can be expressed in
+ -- terms of the signature ones
+ tcAddErrCtxt (bindSigsCtxt tysig_names) $
+ tcSimplifyAndCheck
+ (ptext SLIT("type signature for") <+>
+ hsep (punctuate comma (map (quotes . ppr) binder_names)))
+ real_tyvars_to_gen givens lie `thenTc` \ (lie_free, dict_binds) ->
+
+ returnTc (lie_free, dict_binds, dict_ids)
+
+ ) `thenTc` \ (lie_free, dict_binds, dicts_bound) ->
+
+ ASSERT( not (any (isUnboxedTypeKind . 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
+ zonkTcTypes mono_id_tys `thenNF_Tc` \ zonked_mono_id_types ->
+ let
+ exports = zipWith3 mk_export binder_names mono_ids zonked_mono_id_types
+ dict_tys = map tcIdType dicts_bound
+
+ mk_export binder_name mono_id zonked_mono_id_ty
+ = (tyvars, TcId (replaceIdInfo poly_id (prag_info_fn binder_name)), TcId 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 $ zonked_mono_id_ty
+ -- It's important to build a fully-zonked poly_ty, because
+ -- we'll slurp out its free type variables when extending the
+ -- local environment (tcExtendLocalValEnv); if it's not zonked
+ -- it appears to have free tyvars that aren't actually free at all.
+ in
-tcBind False e bind sigs -- Not top level
- = tcBind_help False e bind sigs
+ -- 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
+ no_of_binders = length binder_names
+
+ mk_mono_id binder_name
+ | theres_a_signature -- There's a signature; and it's overloaded,
+ && not (null sig_theta) -- so make a Method
+ = tcAddSrcLoc sig_loc $
+ newMethodWithGivenTy SignatureOrigin
+ (TcId poly_id) (mkTyVarTys sig_tyvars)
+ sig_theta sig_tau `thenNF_Tc` \ (mono_lie, TcId mono_id) ->
+ -- A bit turgid to have to strip the TcId
+ returnNF_Tc (mono_lie, mono_id)
+
+ | otherwise -- No signature or not overloaded;
+ = tcAddSrcLoc (getSrcLoc binder_name) $
+ (if theres_a_signature then
+ returnNF_Tc sig_tau -- Non-overloaded signature; use its type
+ else
+ newTyVarTy kind -- No signature; use a new type variable
+ ) `thenNF_Tc` \ mono_id_ty ->
+
+ newLocalId (getOccName binder_name) mono_id_ty `thenNF_Tc` \ mono_id ->
+ returnNF_Tc (emptyLIE, mono_id)
+ where
+ maybe_sig = maybeSig tc_ty_sigs binder_name
+ theres_a_signature = maybeToBool maybe_sig
+ Just (TySigInfo name poly_id sig_tyvars sig_theta sig_tau sig_loc) = maybe_sig
-tcBind True e bind sigs -- Top level!
- = pruneSubstTc (tvOfE e) (
+ tysig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
+ is_unrestricted = isUnRestrictedGroup tysig_names mbind
- -- DO THE WORK
- tcBind_help True e bind sigs `thenTc` \ (new_binds, lie, lve) ->
+ kind = case is_rec of
+ Recursive -> mkBoxedTypeKind -- Recursive, so no unboxed types
+ NonRecursive -> mkTypeKind -- Non-recursive, so we permit unboxed types
+\end{code}
-{- Top-level unboxed values are now allowed
- They will be lifted by the Desugarer (see CoreLift.lhs)
+Polymorphic recursion
+~~~~~~~~~~~~~~~~~~~~~
+The game plan for polymorphic recursion in the code above is
- -- CHECK FOR PRIMITIVE TOP-LEVEL BINDS
- listTc [ checkTc (isUnboxedDataType (getIdUniType id))
- (topLevelUnboxedDeclErr id (getSrcLoc id))
- | (_,id) <- lve ] `thenTc_`
--}
+ * 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.
- -- Back-substitute over the binds, since we are about to discard
- -- a good chunk of the substitution.
- applyTcSubstToBinds new_binds `thenNF_Tc` \ final_binds ->
+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:
- -- 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 :: Eq a => [a] -> [a]
+ f xs = ...f...
-\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 (assoc "doSpecPragma" 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
+If we don't take care, after typechecking we get
- new_locals binders
- = case bind of
- NonRecBind _ -> -- Recursive, so no unboxed types
- newLocalsWithOpenTyVarTys binders
+ f = /\a -> \d::Eq a -> let f' = f a d
+ in
+ \ys:[a] -> ...f'...
- RecBind _ -> -- Non-recursive, so we permit unboxed types
- newLocalsWithPolyTyVarTys binders
+Notice the the stupid construction of (f a d), which is of course
+identical to the function we're executing. In this case, the
+polymorphic recursion ins't being used (but that's a very common case).
- 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}
+This can lead to a massive space leak, from the following top-level defn:
-\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
+ ff :: [Int] -> [Int]
+ ff = f dEqInt
+Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
+f' is another thunk which evaluates to the same thing... and you end
+up with a chain of identical values all hung onto by the CAF ff.
- h :: Ord a => [a] -> b -> b
- {-# SPECIALIZE h :: [Int] -> b -> b #-}
+Solution: when typechecking the RHSs we always have in hand the
+*monomorphic* Ids for each binding. So we just need to make sure that
+if (Method f a d) shows up in the constraints emerging from (...f...)
+we just use the monomorphic Id. We achieve this by adding monomorphic Ids
+to the "givens" when simplifying constraints. Thats' what the "mono_lies"
+is doing.
- 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
- -> (Name -> Id)
- -> SignatureInfo
- -> TcM (TypecheckedMonoBinds, LIE)
-
-doSpecPragma e name_to_id (ValSpecInfo name spec_ty using src_loc)
- = let
- main_id = name_to_id name -- Get the parent Id
-
- 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 `minusTyVarSet` 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 ->
- 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')
-
- Just spec_name -> -- use spec_name as the specialisation value ...
+ if is_unrestricted
+ then
+ returnNF_Tc (emptyTyVarSet, 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 (emptyTyVarSet, tyvars_to_gen)) $
+ discardErrsTc $
+
+ tcSimplify (text "getTVG") NotTopLevel tyvars_to_gen lie `thenTc` \ (_, _, constrained_dicts) ->
let
- spec_id = lookupE_Value e spec_name
- spec_id_ty = getIdUniType spec_id
+ -- ASSERT: dicts_sig is already zonked!
+ constrained_tyvars = foldrBag (unionTyVarSets . tyVarsOfInst) emptyTyVarSet constrained_dicts
+ reduced_tyvars_to_gen = tyvars_to_gen `minusTyVarSet` constrained_tyvars
+ in
+ returnTc (constrained_tyvars, reduced_tyvars_to_gen)
+\end{code}
- spec_id_free_tyvars = extractTyVarsFromTy spec_id_ty
- spec_id_ctxt = ValSpecSpecIdCtxt name spec_ty spec_name src_loc
- spec_tys = map maybe_ty main_arg_tys
- maybe_ty ty | isTyVarTy ty = Nothing
- | otherwise = Just ty
- 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 !!!
- let
- spec_info = SpecInfo spec_tys (length main_dicts') local_spec_id
- in
- newSpecPragmaId name spec_ty (Just spec_info) `thenNF_Tc` \ pseudo_spec_id ->
- 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)
- in
- returnTc (spec_bind `AndMonoBinds` pseudo_bind, mkLIE spec_id_dicts')
- )
+\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}
-tc_bind :: E
- -> RenamedBind
- -> TcM (TypecheckedBind, LIE)
+defaultUncommittedTyVar tyvar
+ | isTypeKind (tyVarKind tyvar)
+ = newTcTyVar mkBoxedTypeKind `thenNF_Tc` \ boxed_tyvar ->
+ unifyTauTy (mkTyVarTy boxed_tyvar) (mkTyVarTy tyvar) `thenTc_`
+ returnTc boxed_tyvar
+
+ | otherwise
+ = returnTc tyvar
+\end{code}
-tc_bind e (NonRecBind mono_binds)
- = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (NonRecBind mono_binds2, lie)
-tc_bind e (RecBind mono_binds)
- = tcMonoBinds e mono_binds `thenTc` \ (mono_binds2, lie) ->
- returnTc (RecBind mono_binds2, lie)
-\end{code}
+%************************************************************************
+%* *
+\subsection{tcMonoBind}
+%* *
+%************************************************************************
+
+@tcMonoBinds@ deals with a single @MonoBind@.
+The signatures have been dealt with already.
\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)
+tcMonoBinds :: RenamedMonoBinds
+ -> [Name] -> [TcIdBndr s]
+ -> [TcSigInfo s]
+ -> TcM s (TcMonoBinds s, LIE s)
+
+tcMonoBinds mbind binder_names mono_ids tc_ty_sigs
+ = tcExtendLocalValEnv binder_names mono_ids (
+ tc_mono_binds mbind
+ )
+ where
+ sig_names = [name | (TySigInfo name _ _ _ _ _) <- tc_ty_sigs]
+ sig_ids = [id | (TySigInfo _ id _ _ _ _) <- tc_ty_sigs]
+
+ tc_mono_binds EmptyMonoBinds = returnTc (EmptyMonoBinds, emptyLIE)
+
+ tc_mono_binds (AndMonoBinds mb1 mb2)
+ = tc_mono_binds mb1 `thenTc` \ (mb1a, lie1) ->
+ tc_mono_binds mb2 `thenTc` \ (mb2a, lie2) ->
+ returnTc (AndMonoBinds mb1a mb2a, lie1 `plusLIE` lie2)
+
+ tc_mono_binds (FunMonoBind name inf matches locn)
+ = tcAddSrcLoc locn $
+ tcLookupLocalValueOK "tc_mono_binds" name `thenNF_Tc` \ id ->
+
+ -- Before checking the RHS, extend the envt with
+ -- bindings for the *polymorphic* Ids from any type signatures
+ tcExtendLocalValEnv sig_names sig_ids $
+ tcMatchesFun name (idType id) matches `thenTc` \ (matches', lie) ->
+
+ returnTc (FunMonoBind (TcId id) inf matches' locn, lie)
+
+ tc_mono_binds bind@(PatMonoBind pat grhss_and_binds locn)
+ = tcAddSrcLoc locn $
+ tcAddErrCtxt (patMonoBindsCtxt bind) $
+ tcPat pat `thenTc` \ (pat2, lie_pat, pat_ty) ->
+
+ -- Before checking the RHS, but after the pattern, extend the envt with
+ -- bindings for the *polymorphic* Ids from any type signatures
+ tcExtendLocalValEnv sig_names sig_ids $
+ tcGRHSsAndBinds pat_ty grhss_and_binds `thenTc` \ (grhss_and_binds2, lie) ->
+ returnTc (PatMonoBind pat2 grhss_and_binds2 locn,
+ plusLIE lie_pat lie)
\end{code}
%************************************************************************
@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.
+split up, and have fresh type variables installed. All non-type-signature
+"RenamedSigs" are ignored.
+
+The @TcSigInfo@ contains @TcTypes@ because they are unified with
+the variable's type, and after that checked to see whether they've
+been instantiated.
\begin{code}
-tcSigs :: E -> LVE
- -> [RenamedSig]
- -> TcM [SignatureInfo]
+data TcSigInfo s
+ = TySigInfo
+ Name -- N, the Name in corresponding binding
+ (TcIdBndr s) -- *Polymorphic* binder for this value...
+ -- Usually has name = N, but doesn't have to.
+ [TcTyVar s]
+ (TcThetaType s)
+ (TcTauType s)
+ SrcLoc
+
+
+maybeSig :: [TcSigInfo s] -> Name -> Maybe (TcSigInfo s)
+ -- Search for a particular signature
+maybeSig [] name = Nothing
+maybeSig (sig@(TySigInfo sig_name _ _ _ _ _) : sigs) name
+ | name == sig_name = Just sig
+ | otherwise = maybeSig sigs name
+\end{code}
-tcSigs e lve [] = returnTc []
-tcSigs e lve (s:ss)
- = tc_sig s `thenTc` \ sig_info1 ->
- tcSigs e lve ss `thenTc` \ sig_info2 ->
- returnTc (sig_info1 : sig_info2)
+\begin{code}
+tcTySig :: RenamedSig
+ -> TcM s (TcSigInfo s)
+
+tcTySig (Sig v ty src_loc)
+ = tcAddSrcLoc src_loc $
+ tcHsType ty `thenTc` \ sigma_ty ->
+
+ -- Convert from Type to TcType
+ tcInstSigType sigma_ty `thenNF_Tc` \ sigma_tc_ty ->
+ let
+ poly_id = mkUserId v sigma_tc_ty
+ in
+ -- Instantiate this type
+ -- It's important to do this even though in the error-free case
+ -- we could just split the sigma_tc_ty (since the tyvars don't
+ -- unified with anything). But in the case of an error, when
+ -- the tyvars *do* get unified with something, we want to carry on
+ -- typechecking the rest of the program with the function bound
+ -- to a pristine type, namely sigma_tc_ty
+ tcInstSigTcType sigma_tc_ty `thenNF_Tc` \ (tyvars, rho) ->
+ let
+ (theta, tau) = splitRhoTy rho
+ -- This splitSigmaTy tries hard to make sure that tau' is a type synonym
+ -- wherever possible, which can improve interface files.
+ in
+ returnTc (TySigInfo v poly_id tyvars theta tau src_loc)
+\end{code}
+
+@checkSigMatch@ does the next step in checking signature matching.
+The tau-type part has already been unified. What we do here is to
+check that this unification has not over-constrained the (polymorphic)
+type variables of the original signature type.
+
+The error message here is somewhat unsatisfactory, but it'll do for
+now (ToDo).
+
+\begin{code}
+checkSigMatch []
+ = returnTc (error "checkSigMatch")
+
+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
where
- tc_sig (Sig v ty _ src_loc) -- no interesting pragmas on non-iface sigs
- = addSrcLocTc src_loc (
+ sig1_dict_tys = mk_dict_tys theta1
+ n_sig1_dict_tys = length sig1_dict_tys
+
+ 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 name id sig_tyvars _ sig_tau src_loc)
+ = tcAddSrcLoc src_loc $
+ tcAddErrCtxt (sigCtxt id) $
+ checkSigTyVars sig_tyvars sig_tau
+
+ mk_dict_tys theta = [mkDictTy c ts | (c,ts) <- theta]
+\end{code}
- babyTcMtoTcM
- (tcPolyType (getE_CE e) (getE_TCE e) nullTVE ty) `thenTc` \ sigma_ty ->
- 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.)
+@checkSigTyVars@ is used after the type in a type signature has been unified with
+the actual type found. It then checks that the type variables of the type signature
+are
+ (a) still all type variables
+ eg matching signature [a] against inferred type [(p,q)]
+ [then a will be unified to a non-type variable]
- -- 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_`
+ (b) still all distinct
+ eg matching signature [(a,b)] against inferred type [(p,p)]
+ [then a and b will be unified together]
- returnTc (TySigInfo val tyvars dicts tau_ty src_loc)
- )
+ (c) not mentioned in the environment
+ eg the signature for f in this:
- tc_sig (SpecSig v ty using src_loc)
- = addSrcLocTc src_loc (
+ g x = ... where
+ f :: a->[a]
+ f y = [x,y]
- babyTcMtoTcM
- (tcPolyType (getE_CE e) (getE_TCE e) nullTVE ty) `thenTc` \ sigma_ty ->
+ Here, f is forced to be monorphic by the free occurence of x.
- returnTc (ValSpecInfo v sigma_ty using src_loc)
- )
+Before doing this, the substitution is applied to the signature type variable.
- tc_sig (InlineSig v guide locn)
- = returnTc (ValInlineInfo v guide locn)
+We used to have the notion of a "DontBind" type variable, which would
+only be bound to itself or nothing. Then points (a) and (b) were
+self-checking. But it gave rise to bogus consequential error messages.
+For example:
- tc_sig (DeforestSig v locn)
- = returnTc (ValDeforestInfo v locn)
+ f = (*) -- Monomorphic
+
+ g :: Num a => a -> a
+ g x = f x x
+
+Here, we get a complaint when checking the type signature for g,
+that g isn't polymorphic enough; but then we get another one when
+dealing with the (Num x) context arising from f's definition;
+we try to unify x with Int (to default it), but find that x has already
+been unified with the DontBind variable "a" from g's signature.
+This is really a problem with side-effecting unification; we'd like to
+undo g's effects when its type signature fails, but unification is done
+by side effect, so we can't (easily).
+
+So we revert to ordinary type variables for signatures, and try to
+give a helpful message in checkSigTyVars.
+
+\begin{code}
+checkSigTyVars :: [TcTyVar s] -- The original signature type variables
+ -> TcType s -- signature type (for err msg)
+ -> TcM s [TcTyVar s] -- Zonked signature type variables
+
+checkSigTyVars sig_tyvars sig_tau
+ = mapNF_Tc zonkTcTyVar sig_tyvars `thenNF_Tc` \ sig_tys ->
+ let
+ sig_tyvars' = map (getTyVar "checkSigTyVars") sig_tys
+ in
+
+ -- Check points (a) and (b)
+ checkTcM (all isTyVarTy sig_tys && hasNoDups sig_tyvars')
+ (zonkTcType sig_tau `thenNF_Tc` \ sig_tau' ->
+ failWithTc (badMatchErr sig_tau sig_tau')
+ ) `thenTc_`
+
+ -- Check point (c)
+ -- We want to report errors in terms of the original signature tyvars,
+ -- ie sig_tyvars, NOT sig_tyvars'. sig_tyvars' correspond
+ -- 1-1 with sig_tyvars, so we can just map back.
+ tcGetGlobalTyVars `thenNF_Tc` \ globals ->
+ let
+ mono_tyvars' = [sig_tv' | sig_tv' <- sig_tyvars',
+ sig_tv' `elementOfTyVarSet` globals]
+
+ mono_tyvars = map (assoc "checkSigTyVars" (sig_tyvars' `zip` sig_tyvars)) mono_tyvars'
+ in
+ checkTcM (null mono_tyvars')
+ (failWithTc (notAsPolyAsSigErr sig_tau mono_tyvars)) `thenTc_`
+
+ returnTc sig_tyvars'
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{SPECIALIZE pragmas}
+%* *
+%************************************************************************
- tc_sig (MagicUnfoldingSig v str locn)
- = returnTc (ValMagicUnfoldingInfo v str locn)
+
+@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}
+tcPragmaSigs :: [RenamedSig] -- The pragma signatures
+ -> TcM s (Name -> IdInfo, -- Maps name to the appropriate IdInfo
+ TcMonoBinds s,
+ LIE s)
+
+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, andMonoBinds binds, plusLIEs lies)
+\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 #-}
+\end{verbatim}
+
+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.
+
+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.
+
+\begin{code}
+tcPragmaSig :: RenamedSig -> TcM s (Maybe (Name, IdInfo -> IdInfo), TcMonoBinds s, LIE s)
+tcPragmaSig (Sig _ _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+tcPragmaSig (SpecInstSig _ _) = returnTc (Nothing, EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (InlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IWantToBeINLINEd), EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (NoInlineSig name loc)
+ = returnTc (Just (name, setInlinePragInfo IDontWantToBeINLINEd), EmptyMonoBinds, emptyLIE)
+
+tcPragmaSig (SpecSig name poly_ty maybe_spec_name src_loc)
+ = -- SPECIALISE f :: forall b. theta => tau = g
+ tcAddSrcLoc src_loc $
+ tcAddErrCtxt (valSpecSigCtxt name poly_ty) $
+
+ -- Get and instantiate its alleged specialised type
+ tcHsType poly_ty `thenTc` \ sig_sigma ->
+ tcInstSigType sig_sigma `thenNF_Tc` \ sig_ty ->
+
+ -- 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 ->
+ tcInstSigTcType (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 = mkTyVarSet 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}
+
+
+%************************************************************************
+%* *
+\subsection[TcBinds-errors]{Error contexts and messages}
+%* *
+%************************************************************************
+
+
+\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)
+ ])
+
+-----------------------------------------------
+sigCtxt id
+ = sep [ptext SLIT("When checking the type signature for"), quotes (ppr id)]
+
+bindSigsCtxt ids
+ = ptext SLIT("When checking the type signature(s) for") <+> pprQuotedList ids
+
+-----------------------------------------------
+sigContextsErr
+ = 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)"))
+
+-----------------------------------------------
+specGroundnessCtxt
+ = panic "specGroundnessCtxt"
+
+--------------------------------------------
+specContextGroundnessCtxt -- err_ctxt dicts
+ = panic "specContextGroundnessCtxt"
+{-
+ = hang (
+ sep [hsep [ptext SLIT("In the SPECIALIZE pragma for"), ppr name],
+ hcat [ptext SLIT(" specialised to the type"), ppr spec_ty],
+ pp_spec_id,
+ ptext SLIT("... not all overloaded type variables were instantiated"),
+ ptext SLIT("to ground types:")])
+ 4 (vcat [hsep [ppr c, ppr 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 -> empty)
+ ValSpecSpecIdCtxt n ty spec loc ->
+ (n, ty, loc,
+ hsep [ptext SLIT("... type of explicit id"), ppr spec])
+-}
\end{code}
projects / ghc-hetmet.git / blobdiff