%
-% (c) The GRASP/AQUA Project, Glasgow University, 1992-1996
+% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[TcModule]{Typechecking a whole module}
\begin{code}
-#include "HsVersions.h"
-
module TcModule (
typecheckModule,
- TcResults(..),
- TcResultBinds(..),
- TcIfaceInfo(..),
- TcLocalTyConsAndClasses(..),
- TcSpecialiseRequests(..),
- TcDDumpDeriv(..)
+ TcResults(..)
) where
-import Ubiq{-uitous-}
+#include "HsVersions.h"
-import HsSyn ( HsModule(..), HsBinds(..), Bind, HsExpr,
- TyDecl, SpecDataSig, ClassDecl, InstDecl,
- SpecInstSig, DefaultDecl, Sig, Fake, InPat,
- FixityDecl, IE, ImportDecl
+import CmdLineOpts ( DynFlag(..), DynFlags, opt_PprStyle_Debug )
+import HsSyn ( HsBinds(..), MonoBinds(..), HsDecl(..) )
+import HsTypes ( toHsType )
+import RnHsSyn ( RenamedHsDecl )
+import TcHsSyn ( TypecheckedMonoBinds,
+ TypecheckedForeignDecl, TypecheckedRuleDecl,
+ zonkTopBinds, zonkForeignExports, zonkRules
)
-import RnHsSyn ( RenamedHsModule(..), RenamedFixityDecl(..) )
-import TcHsSyn ( TypecheckedHsBinds(..), TypecheckedHsExpr(..),
- TcIdOcc(..), zonkBinds, zonkInst, zonkId )
import TcMonad
-import Inst ( Inst, plusLIE )
-import TcBinds ( tcBindsAndThen )
-import TcClassDcl ( tcClassDecls2 )
+import Inst ( plusLIE )
+import TcBinds ( tcTopBinds )
+import TcClassDcl ( tcClassDecls2, mkImplicitClassBinds )
import TcDefaults ( tcDefaults )
-import TcEnv ( tcExtendGlobalValEnv, getEnv_LocalIds,
- getEnv_TyCons, getEnv_Classes,
- tcLookupLocalValueByKey, tcLookupTyConByKey )
+import TcEnv ( TcEnv, tcExtendGlobalValEnv, tcLookupGlobal_maybe,
+ tcEnvTyCons, tcEnvClasses,
+ tcSetEnv, tcSetInstEnv, initTcEnv, getTcGEnv
+ )
+import TcRules ( tcRules )
+import TcForeign ( tcForeignImports, tcForeignExports )
import TcIfaceSig ( tcInterfaceSigs )
import TcInstDcls ( tcInstDecls1, tcInstDecls2 )
-import TcInstUtil ( buildInstanceEnvs, InstInfo )
+import InstEnv ( InstInfo(..) )
import TcSimplify ( tcSimplifyTop )
-import TcTyClsDecls ( tcTyAndClassDecls1 )
-
-import Bag ( listToBag )
-import Class ( GenClass )
-import ErrUtils ( Warning(..), Error(..) )
-import Id ( GenId, isDataCon, isMethodSelId, idType )
-import Maybes ( catMaybes )
-import Name ( isExported, isLocallyDefined )
-import PrelInfo ( unitTy, mkPrimIoTy )
-import Pretty
-import RnUtils ( RnEnv(..) )
-import TyCon ( TyCon )
-import Type ( mkSynTy )
-import Unify ( unifyTauTy )
-import UniqFM ( lookupUFM_Directly, lookupWithDefaultUFM_Directly,
- filterUFM, eltsUFM )
-import Unique ( iOTyConKey, mainIdKey, mainPrimIOIdKey )
+import TcTyClsDecls ( tcTyAndClassDecls )
+import TcTyDecls ( mkImplicitDataBinds )
+
+import CoreUnfold ( unfoldingTemplate )
+import Type ( funResultTy, splitForAllTys )
+import Bag ( isEmptyBag )
+import ErrUtils ( printErrorsAndWarnings, dumpIfSet_dyn )
+import Id ( idType, idName, idUnfolding )
+import Module ( Module, moduleName, plusModuleEnv )
+import Name ( Name, nameOccName, isLocallyDefined, isGlobalName,
+ toRdrName, nameEnvElts, emptyNameEnv, lookupNameEnv
+ )
+import TyCon ( tyConGenInfo, isClassTyCon )
+import OccName ( isSysOcc )
+import PrelNames ( mAIN_Name, mainName )
+import Maybes ( thenMaybe )
import Util
-
-import FiniteMap ( emptyFM )
-tycon_specs = emptyFM
+import BasicTypes ( EP(..), Fixity )
+import Bag ( isEmptyBag )
+import Outputable
+import HscTypes ( PersistentCompilerState(..), HomeSymbolTable, HomeIfaceTable,
+ PackageSymbolTable, PackageIfaceTable, DFunId, ModIface(..),
+ TypeEnv, extendTypeEnv, lookupTable,
+ TyThing(..), groupTyThings )
+import FiniteMap ( FiniteMap, delFromFM, lookupWithDefaultFM )
\end{code}
Outside-world interface:
\begin{code}
--- Convenient type synonyms first:
-type TcResults
- = (TcResultBinds,
- TcIfaceInfo,
- TcLocalTyConsAndClasses,
- TcSpecialiseRequests,
- TcDDumpDeriv)
-
-type TcResultBinds
- = (TypecheckedHsBinds, -- record selector binds
- TypecheckedHsBinds, -- binds from class decls; does NOT
- -- include default-methods bindings
- TypecheckedHsBinds, -- binds from instance decls; INCLUDES
- -- class default-methods binds
- TypecheckedHsBinds, -- binds from value decls
- [(Id, TypecheckedHsExpr)]) -- constant instance binds
-
-type TcIfaceInfo -- things for the interface generator
- = ([Id], [TyCon], [Class], Bag InstInfo)
+-- Convenient type synonyms first:
+data TcResults
+ = TcResults {
+ tc_pcs :: PersistentCompilerState, -- Augmented with imported information,
+ -- (but not stuff from this module)
+
+ -- All these fields have info *just for this module*
+ tc_env :: TypeEnv, -- The top level TypeEnv
+ tc_insts :: [DFunId], -- Instances
+ tc_binds :: TypecheckedMonoBinds, -- Bindings
+ tc_fords :: [TypecheckedForeignDecl], -- Foreign import & exports.
+ tc_rules :: [TypecheckedRuleDecl] -- Transformation rules
+ }
-type TcLocalTyConsAndClasses -- things defined in this module
- = ([TyCon], [Class])
- -- not sure the classes are used at all (ToDo)
+---------------
+typecheckModule
+ :: DynFlags
+ -> Module
+ -> PersistentCompilerState
+ -> HomeSymbolTable -> HomeIfaceTable
+ -> [RenamedHsDecl]
+ -> IO (Maybe TcResults)
+
+typecheckModule dflags this_mod pcs hst hit decls
+ = do env <- initTcEnv global_symbol_table
+
+ (maybe_result, (errs,warns)) <- initTc dflags env tc_module
+
+ let { maybe_tc_result :: Maybe TcResults ;
+ maybe_tc_result = case maybe_result of
+ Nothing -> Nothing
+ Just (_,r) -> Just r }
+
+ printErrorsAndWarnings (errs,warns)
+ printTcDump dflags maybe_tc_result
+
+ if isEmptyBag errs then
+ return Nothing
+ else
+ return maybe_tc_result
+ where
+ global_symbol_table = pcs_PST pcs `plusModuleEnv` hst
-type TcSpecialiseRequests
- = FiniteMap TyCon [(Bool, [Maybe Type])]
- -- source tycon specialisation requests
+ tc_module :: TcM (TcEnv, TcResults)
+ tc_module = fixTc (\ ~(unf_env ,_) -> tcModule pcs hst get_fixity this_mod decls unf_env)
-type TcDDumpDeriv
- = PprStyle -> Pretty
+ pit = pcs_PIT pcs
----------------
-typecheckModule
- :: UniqSupply
- -> RnEnv -- for renaming derivings
- -> RenamedHsModule
- -> MaybeErr
- (TcResults, -- if all goes well...
- Bag Warning) -- (we can still get warnings)
- (Bag Error, -- if we had errors...
- Bag Warning)
-
-typecheckModule us rn_env mod
- = initTc us (tcModule rn_env mod)
+ get_fixity :: Name -> Maybe Fixity
+ get_fixity nm = lookupTable hit pit nm `thenMaybe` \ iface ->
+ lookupNameEnv (mi_fixities iface) nm
\end{code}
The internal monster:
\begin{code}
-tcModule :: RnEnv -- for renaming derivings
- -> RenamedHsModule -- input
- -> TcM s TcResults -- output
-
-tcModule rn_env
- (HsModule mod_name verion exports imports fixities
- ty_decls specdata_sigs cls_decls inst_decls specinst_sigs
- default_decls val_decls sigs src_loc)
-
- = ASSERT(null imports)
-
- tcAddSrcLoc src_loc $ -- record where we're starting
-
- -- Tie the knot for inteface-file value declaration signatures
- -- This info is only used inside the knot for type-checking the
- -- pragmas, which is done lazily [ie failure just drops the pragma
- -- without having any global-failure effect].
-
- fixTc (\ ~(_, _, _, _, _, _, sig_ids) ->
- tcExtendGlobalValEnv sig_ids (
-
- -- The knot for instance information. This isn't used at all
- -- till we type-check value declarations
- fixTc ( \ ~(rec_inst_mapper, _, _, _, _, _) ->
-
- -- Type-check the type and class decls
- --trace "tcTyAndClassDecls:" $
- tcTyAndClassDecls1 rec_inst_mapper ty_decls_bag cls_decls_bag
- `thenTc` \ (env, record_binds) ->
-
- -- Typecheck the instance decls, includes deriving
- tcSetEnv env (
- --trace "tcInstDecls:" $
- tcInstDecls1 inst_decls_bag specinst_sigs
- mod_name rn_env fixities
- ) `thenTc` \ (inst_info, deriv_binds, ddump_deriv) ->
-
- buildInstanceEnvs inst_info `thenTc` \ inst_mapper ->
-
- returnTc (inst_mapper, env, record_binds, inst_info, deriv_binds, ddump_deriv)
-
- ) `thenTc` \ (_, env, record_binds, inst_info, deriv_binds, ddump_deriv) ->
- tcSetEnv env (
-
- -- Default declarations
- tcDefaults default_decls `thenTc` \ defaulting_tys ->
- tcSetDefaultTys defaulting_tys ( -- for the iface sigs...
-
- -- Interface type signatures
- -- We tie a knot so that the Ids read out of interfaces are in scope
- -- when we read their pragmas.
- -- What we rely on is that pragmas are typechecked lazily; if
- -- any type errors are found (ie there's an inconsistency)
- -- we silently discard the pragma
- tcInterfaceSigs sigs `thenTc` \ sig_ids ->
-
- returnTc (env, inst_info, record_binds, deriv_binds, ddump_deriv, defaulting_tys, sig_ids)
-
- )))) `thenTc` \ (env, inst_info, record_binds, deriv_binds, ddump_deriv, defaulting_tys, _) ->
-
- tcSetEnv env ( -- to the end...
- tcSetDefaultTys defaulting_tys ( -- ditto
-
- -- Value declarations next.
- -- We also typecheck any extra binds that came out of the "deriving" process
- --trace "tcBinds:" $
- tcBindsAndThen
- (\ binds1 (binds2, thing) -> (binds1 `ThenBinds` binds2, thing))
- (val_decls `ThenBinds` deriv_binds)
- ( -- Second pass over instance declarations,
- -- to compile the bindings themselves.
- tcInstDecls2 inst_info `thenNF_Tc` \ (lie_instdecls, inst_binds) ->
- tcClassDecls2 cls_decls_bag `thenNF_Tc` \ (lie_clasdecls, cls_binds) ->
- tcGetEnv `thenNF_Tc` \ env ->
- returnTc ( (EmptyBinds, (inst_binds, cls_binds, env)),
- lie_instdecls `plusLIE` lie_clasdecls,
- () ))
-
- `thenTc` \ ((val_binds, (inst_binds, cls_binds, final_env)), lie_alldecls, _) ->
-
- checkTopLevelIds mod_name final_env `thenTc_`
-
- -- Deal with constant or ambiguous InstIds. How could
- -- there be ambiguous ones? They can only arise if a
- -- top-level decl falls under the monomorphism
- -- restriction, and no subsequent decl instantiates its
- -- type. (Usually, ambiguous type variables are resolved
- -- during the generalisation step.)
- tcSimplifyTop lie_alldecls `thenTc` \ const_insts ->
+tcModule :: PersistentCompilerState
+ -> HomeSymbolTable
+ -> (Name -> Maybe Fixity)
+ -> Module
+ -> [RenamedHsDecl]
+ -> TcEnv -- The knot-tied environment
+ -> TcM (TcEnv, TcResults)
+
+ -- (unf_env :: TcEnv) is used for type-checking interface pragmas
+ -- which is done lazily [ie failure just drops the pragma
+ -- without having any global-failure effect].
+ --
+ -- unf_env is also used to get the pragama info
+ -- for imported dfuns and default methods
+
+tcModule pcs hst get_fixity this_mod decls unf_env
+ = -- Type-check the type and class decls
+ tcTyAndClassDecls unf_env decls `thenTc` \ env ->
+ tcSetEnv env $
let
- localids = getEnv_LocalIds final_env
- tycons = getEnv_TyCons final_env
- classes = getEnv_Classes final_env
-
- local_tycons = filter isLocallyDefined tycons
- local_classes = filter isLocallyDefined classes
-
- exported_ids = [v | v <- localids,
- isExported v && not (isDataCon v) && not (isMethodSelId v)]
+ classes = tcEnvClasses env
+ tycons = tcEnvTyCons env -- INCLUDES tycons derived from classes
+ local_tycons = [ tc | tc <- tycons,
+ isLocallyDefined tc,
+ not (isClassTyCon tc)
+ ]
+ -- For local_tycons, filter out the ones derived from classes
+ -- Otherwise the latter show up in interface files
in
- -- Backsubstitution. Monomorphic top-level decls may have
- -- been instantiated by subsequent decls, and the final
- -- simplification step may have instantiated some
- -- ambiguous types. So, sadly, we need to back-substitute
- -- over the whole bunch of bindings.
- zonkBinds record_binds `thenNF_Tc` \ record_binds' ->
- zonkBinds val_binds `thenNF_Tc` \ val_binds' ->
- zonkBinds inst_binds `thenNF_Tc` \ inst_binds' ->
- zonkBinds cls_binds `thenNF_Tc` \ cls_binds' ->
- mapNF_Tc zonkInst const_insts `thenNF_Tc` \ const_insts' ->
- mapNF_Tc (zonkId.TcId) exported_ids `thenNF_Tc` \ exported_ids' ->
-
- -- FINISHED AT LAST
- returnTc (
- (record_binds', cls_binds', inst_binds', val_binds', const_insts'),
-
- -- the next collection is just for mkInterface
- (exported_ids', tycons, classes, inst_info),
-
- (local_tycons, local_classes),
-
- tycon_specs,
-
- ddump_deriv
- )))
- where
- ty_decls_bag = listToBag ty_decls
- cls_decls_bag = listToBag cls_decls
- inst_decls_bag = listToBag inst_decls
+
+ -- Typecheck the instance decls, includes deriving
+ tcInstDecls1 (pcs_insts pcs) (pcs_PRS pcs)
+ hst unf_env get_fixity this_mod
+ local_tycons decls `thenTc` \ (new_pcs_insts, inst_env, local_inst_info, deriv_binds) ->
+ tcSetInstEnv inst_env $
+
+ -- Default declarations
+ tcDefaults decls `thenTc` \ defaulting_tys ->
+ tcSetDefaultTys defaulting_tys $
+
+ -- Interface type signatures
+ -- We tie a knot so that the Ids read out of interfaces are in scope
+ -- when we read their pragmas.
+ -- What we rely on is that pragmas are typechecked lazily; if
+ -- any type errors are found (ie there's an inconsistency)
+ -- we silently discard the pragma
+ -- We must do this before mkImplicitDataBinds (which comes next), since
+ -- the latter looks up unpackCStringId, for example, which is usually
+ -- imported
+ tcInterfaceSigs unf_env decls `thenTc` \ sig_ids ->
+ tcExtendGlobalValEnv sig_ids $
+
+ -- Create any necessary record selector Ids and their bindings
+ -- "Necessary" includes data and newtype declarations
+ -- We don't create bindings for dictionary constructors;
+ -- they are always fully applied, and the bindings are just there
+ -- to support partial applications
+ mkImplicitDataBinds tycons `thenTc` \ (data_ids, imp_data_binds) ->
+ mkImplicitClassBinds classes `thenNF_Tc` \ (cls_ids, imp_cls_binds) ->
+
+ -- Extend the global value environment with
+ -- (a) constructors
+ -- (b) record selectors
+ -- (c) class op selectors
+ -- (d) default-method ids... where? I can't see where these are
+ -- put into the envt, and I'm worried that the zonking phase
+ -- will find they aren't there and complain.
+ tcExtendGlobalValEnv data_ids $
+ tcExtendGlobalValEnv cls_ids $
+
+ -- Foreign import declarations next
+ tcForeignImports decls `thenTc` \ (fo_ids, foi_decls) ->
+ tcExtendGlobalValEnv fo_ids $
+
+ -- Value declarations next.
+ -- We also typecheck any extra binds that came out of the "deriving" process
+ tcTopBinds (get_binds decls `ThenBinds` deriv_binds) `thenTc` \ ((val_binds, env), lie_valdecls) ->
+ tcSetEnv env $
+
+ -- Foreign export declarations next
+ tcForeignExports decls `thenTc` \ (lie_fodecls, foe_binds, foe_decls) ->
+
+ -- Second pass over class and instance declarations,
+ -- to compile the bindings themselves.
+ tcInstDecls2 local_inst_info `thenNF_Tc` \ (lie_instdecls, inst_binds) ->
+ tcClassDecls2 decls `thenNF_Tc` \ (lie_clasdecls, cls_dm_binds) ->
+ tcRules (pcs_rules pcs) decls `thenNF_Tc` \ (new_pcs_rules, lie_rules, local_rules) ->
+
+ -- Deal with constant or ambiguous InstIds. How could
+ -- there be ambiguous ones? They can only arise if a
+ -- top-level decl falls under the monomorphism
+ -- restriction, and no subsequent decl instantiates its
+ -- type. (Usually, ambiguous type variables are resolved
+ -- during the generalisation step.)
+ let
+ lie_alldecls = lie_valdecls `plusLIE`
+ lie_instdecls `plusLIE`
+ lie_clasdecls `plusLIE`
+ lie_fodecls `plusLIE`
+ lie_rules
+ in
+ tcSimplifyTop lie_alldecls `thenTc` \ const_inst_binds ->
+
+ -- Check that Main defines main
+ checkMain this_mod `thenTc_`
+
+ -- Backsubstitution. This must be done last.
+ -- Even tcSimplifyTop may do some unification.
+ let
+ all_binds = imp_data_binds `AndMonoBinds`
+ imp_cls_binds `AndMonoBinds`
+ val_binds `AndMonoBinds`
+ inst_binds `AndMonoBinds`
+ cls_dm_binds `AndMonoBinds`
+ const_inst_binds `AndMonoBinds`
+ foe_binds
+ in
+ zonkTopBinds all_binds `thenNF_Tc` \ (all_binds', final_env) ->
+ tcSetEnv final_env $
+ -- zonkTopBinds puts all the top-level Ids into the tcGEnv
+ zonkForeignExports foe_decls `thenNF_Tc` \ foe_decls' ->
+ zonkRules local_rules `thenNF_Tc` \ local_rules' ->
+
+
+ let groups :: FiniteMap Module TypeEnv
+ groups = groupTyThings (nameEnvElts (getTcGEnv final_env))
+
+ local_type_env :: TypeEnv
+ local_type_env = lookupWithDefaultFM groups emptyNameEnv this_mod
+
+ new_pst :: PackageSymbolTable
+ new_pst = extendTypeEnv (pcs_PST pcs) (delFromFM groups this_mod)
+
+ final_pcs :: PersistentCompilerState
+ final_pcs = pcs { pcs_PST = new_pst,
+ pcs_insts = new_pcs_insts,
+ pcs_rules = new_pcs_rules
+ }
+ in
+ returnTc (final_env,
+ TcResults { tc_pcs = final_pcs,
+ tc_env = local_type_env,
+ tc_binds = all_binds',
+ tc_insts = map iDFunId local_inst_info,
+ tc_fords = foi_decls ++ foe_decls',
+ tc_rules = rules'
+ })
+
+get_binds decls = foldr ThenBinds EmptyBinds [binds | ValD binds <- decls]
+\end{code}
+
+\begin{code}
+checkMain :: Module -> TcM ()
+checkMain this_mod
+ | moduleName this_mod == mAIN_Name
+ = tcLookupGlobal_maybe mainName `thenNF_Tc` \ maybe_main ->
+ case maybe_main of
+ Just (AnId _) -> returnTc ()
+ other -> addErrTc noMainErr
+
+ | otherwise = returnTc ()
+
+noMainErr
+ = hsep [ptext SLIT("Module"), quotes (ppr mAIN_Name),
+ ptext SLIT("must include a definition for"), quotes (ptext SLIT("main"))]
\end{code}
%************************************************************************
%* *
-\subsection{Error checking code}
+\subsection{Dumping output}
%* *
%************************************************************************
-
-checkTopLevelIds checks that Main.main or Main.mainPrimIO has correct type.
-
\begin{code}
-checkTopLevelIds :: FAST_STRING -> TcEnv s -> TcM s ()
-checkTopLevelIds mod final_env
- | mod /= SLIT("Main")
- = returnTc ()
-
- | otherwise
- = tcSetEnv final_env (
- tcLookupLocalValueByKey mainIdKey `thenNF_Tc` \ maybe_main ->
- tcLookupLocalValueByKey mainPrimIOIdKey `thenNF_Tc` \ maybe_prim ->
- tcLookupTyConByKey iOTyConKey `thenNF_Tc` \ io_tc ->
-
- case (maybe_main, maybe_prim) of
- (Just main, Nothing) -> tcAddErrCtxt mainCtxt $
- unifyTauTy (mkSynTy io_tc [unitTy])
- (idType main)
-
- (Nothing, Just prim) -> tcAddErrCtxt primCtxt $
- unifyTauTy (mkPrimIoTy unitTy)
- (idType prim)
-
- (Just _ , Just _ ) -> failTc mainBothIdErr
- (Nothing, Nothing) -> failTc mainNoneIdErr
- )
-
-mainCtxt sty
- = ppStr "main should have type IO ()"
-
-primCtxt sty
- = ppStr "mainPrimIO should have type PrimIO ()"
-
-mainBothIdErr sty
- = ppStr "module Main contains definitions for both main and mainPrimIO"
-
-mainNoneIdErr sty
- = ppStr "module Main does not contain a definition for main (or mainPrimIO)"
+printTcDump dflags Nothing = return ()
+printTcDump dflags (Just results)
+ = do dumpIfSet_dyn dflags Opt_D_dump_types
+ "Type signatures" (dump_sigs results)
+ dumpIfSet_dyn dflags Opt_D_dump_tc
+ "Typechecked" (dump_tc results)
+
+dump_tc results
+ = vcat [ppr (tc_binds results),
+ pp_rules (tc_rules results),
+ ppr_gen_tycons [tc | ATyCon tc <- nameEnvElts (tc_env results)]
+ ]
+
+dump_sigs results -- Print type signatures
+ = -- Convert to HsType so that we get source-language style printing
+ -- And sort by RdrName
+ vcat $ map ppr_sig $ sortLt lt_sig $
+ [(toRdrName id, toHsType (idType id))
+ | AnId id <- nameEnvElts (tc_env results),
+ want_sig id
+ ]
+ where
+ lt_sig (n1,_) (n2,_) = n1 < n2
+ ppr_sig (n,t) = ppr n <+> dcolon <+> ppr t
+
+ want_sig id | opt_PprStyle_Debug = True
+ | otherwise = isLocallyDefined n &&
+ isGlobalName n &&
+ not (isSysOcc (nameOccName n))
+ where
+ n = idName id
+
+ppr_gen_tycons tcs = vcat [ptext SLIT("{-# Generic type constructor details"),
+ vcat (map ppr_gen_tycon (filter isLocallyDefined tcs)),
+ ptext SLIT("#-}")
+ ]
+
+-- x&y are now Id's, not CoreExpr's
+ppr_gen_tycon tycon
+ | Just ep <- tyConGenInfo tycon
+ = (ppr tycon <> colon) $$ nest 4 (ppr_ep ep)
+
+ | otherwise = ppr tycon <> colon <+> ptext SLIT("Not derivable")
+
+ppr_ep (EP from to)
+ = vcat [ ptext SLIT("Rep type:") <+> ppr (funResultTy from_tau),
+ ptext SLIT("From:") <+> ppr (unfoldingTemplate (idUnfolding from)),
+ ptext SLIT("To:") <+> ppr (unfoldingTemplate (idUnfolding to))
+ ]
+ where
+ (_,from_tau) = splitForAllTys (idType from)
+
+pp_rules [] = empty
+pp_rules rs = vcat [ptext SLIT("{-# RULES"),
+ nest 4 (vcat (map ppr rs)),
+ ptext SLIT("#-}")]
\end{code}