2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 @DsMonad@: monadery used in desugaring
10 DsM, mapM, mapAndUnzipM,
11 initDs, initDsTc, fixDs,
12 foldlM, foldrM, ifOptM,
13 Applicative(..),(<$>),
15 newTyVarsDs, newLocalName,
16 duplicateLocalDs, newSysLocalDs, newSysLocalsDs, newUniqueId,
18 getSrcSpanDs, putSrcSpanDs,
21 UniqSupply, newUniqueSupply,
22 getDOptsDs, getGhcModeDs, doptDs,
23 dsLookupGlobal, dsLookupGlobalId, dsLookupTyCon, dsLookupDataCon,
26 DsMetaEnv, DsMetaVal(..), dsLookupMetaEnv, dsExtendMetaEnv,
29 DsWarning, warnDs, failWithDs,
33 EquationInfo(..), MatchResult(..), DsWrapper, idDsWrapper,
37 #include "HsVersions.h"
67 %************************************************************************
69 Data types for the desugarer
71 %************************************************************************
75 = DsMatchContext (HsMatchContext Name) SrcSpan
80 = EqnInfo { eqn_pats :: [Pat Id], -- The patterns for an eqn
81 eqn_rhs :: MatchResult } -- What to do after match
83 type DsWrapper = CoreExpr -> CoreExpr
84 idDsWrapper :: DsWrapper
87 -- The semantics of (match vs (EqnInfo wrap pats rhs)) is the MatchResult
88 -- \fail. wrap (case vs of { pats -> rhs fail })
89 -- where vs are not bound by wrap
92 -- A MatchResult is an expression with a hole in it
95 CanItFail -- Tells whether the failure expression is used
96 (CoreExpr -> DsM CoreExpr)
97 -- Takes a expression to plug in at the
98 -- failure point(s). The expression should
101 data CanItFail = CanFail | CantFail
103 orFail :: CanItFail -> CanItFail -> CanItFail
104 orFail CantFail CantFail = CantFail
109 %************************************************************************
113 %************************************************************************
115 Now the mondo monad magic (yes, @DsM@ is a silly name)---carry around
116 a @UniqueSupply@ and some annotations, which
117 presumably include source-file location information:
119 type DsM result = TcRnIf DsGblEnv DsLclEnv result
121 -- Compatibility functions
122 fixDs :: (a -> DsM a) -> DsM a
125 type DsWarning = (SrcSpan, SDoc)
126 -- Not quite the same as a WarnMsg, we have an SDoc here
127 -- and we'll do the print_unqual stuff later on to turn it
130 data DsGblEnv = DsGblEnv {
131 ds_mod :: Module, -- For SCC profiling
132 ds_unqual :: PrintUnqualified,
133 ds_msgs :: IORef Messages, -- Warning messages
134 ds_if_env :: (IfGblEnv, IfLclEnv) -- Used for looking up global,
135 -- possibly-imported things
138 data DsLclEnv = DsLclEnv {
139 ds_meta :: DsMetaEnv, -- Template Haskell bindings
140 ds_loc :: SrcSpan -- to put in pattern-matching error msgs
143 -- Inside [| |] brackets, the desugarer looks
144 -- up variables in the DsMetaEnv
145 type DsMetaEnv = NameEnv DsMetaVal
148 = Bound Id -- Bound by a pattern inside the [| |].
149 -- Will be dynamically alpha renamed.
150 -- The Id has type THSyntax.Var
152 | Splice (HsExpr Id) -- These bindings are introduced by
153 -- the PendingSplices on a HsBracketOut
156 -> Module -> GlobalRdrEnv -> TypeEnv
159 -- Print errors and warnings, if any arise
161 initDs hsc_env mod rdr_env type_env thing_inside
162 = do { msg_var <- newIORef (emptyBag, emptyBag)
163 ; let dflags = hsc_dflags hsc_env
164 ; (ds_gbl_env, ds_lcl_env) <- mkDsEnvs dflags mod rdr_env type_env msg_var
166 ; either_res <- initTcRnIf 'd' hsc_env ds_gbl_env ds_lcl_env $
167 tryM thing_inside -- Catch exceptions (= errors during desugaring)
169 -- Display any errors and warnings
170 -- Note: if -Werror is used, we don't signal an error here.
171 ; msgs <- readIORef msg_var
172 ; printErrorsAndWarnings dflags msgs
174 ; let final_res | errorsFound dflags msgs = Nothing
175 | otherwise = case either_res of
176 Right res -> Just res
177 Left exn -> pprPanic "initDs" (text (show exn))
178 -- The (Left exn) case happens when the thing_inside throws
179 -- a UserError exception. Then it should have put an error
180 -- message in msg_var, so we just discard the exception
184 initDsTc :: DsM a -> TcM a
185 initDsTc thing_inside
186 = do { this_mod <- getModule
187 ; tcg_env <- getGblEnv
188 ; msg_var <- getErrsVar
190 ; let type_env = tcg_type_env tcg_env
191 rdr_env = tcg_rdr_env tcg_env
192 ; ds_envs <- liftIO $ mkDsEnvs dflags this_mod rdr_env type_env msg_var
193 ; setEnvs ds_envs thing_inside }
195 mkDsEnvs :: DynFlags -> Module -> GlobalRdrEnv -> TypeEnv -> IORef Messages -> IO (DsGblEnv, DsLclEnv)
196 mkDsEnvs dflags mod rdr_env type_env msg_var
197 = do -- TODO: unnecessarily monadic
198 let if_genv = IfGblEnv { if_rec_types = Just (mod, return type_env) }
199 if_lenv = mkIfLclEnv mod (ptext SLIT("GHC error in desugarer lookup in") <+> ppr mod)
200 gbl_env = DsGblEnv { ds_mod = mod,
201 ds_if_env = (if_genv, if_lenv),
202 ds_unqual = mkPrintUnqualified dflags rdr_env,
204 lcl_env = DsLclEnv { ds_meta = emptyNameEnv,
207 return (gbl_env, lcl_env)
211 %************************************************************************
213 Operations in the monad
215 %************************************************************************
217 And all this mysterious stuff is so we can occasionally reach out and
218 grab one or more names. @newLocalDs@ isn't exported---exported
219 functions are defined with it. The difference in name-strings makes
220 it easier to read debugging output.
223 -- Make a new Id with the same print name, but different type, and new unique
224 newUniqueId :: Name -> Type -> DsM Id
225 newUniqueId id ty = do
227 return (mkSysLocal (occNameFS (nameOccName id)) uniq ty)
229 duplicateLocalDs :: Id -> DsM Id
230 duplicateLocalDs old_local = do
232 return (setIdUnique old_local uniq)
234 newSysLocalDs, newFailLocalDs :: Type -> DsM Id
235 newSysLocalDs ty = do
237 return (mkSysLocal FSLIT("ds") uniq ty)
239 newSysLocalsDs :: [Type] -> DsM [Id]
240 newSysLocalsDs tys = mapM newSysLocalDs tys
242 newFailLocalDs ty = do
244 return (mkSysLocal FSLIT("fail") uniq ty)
245 -- The UserLocal bit just helps make the code a little clearer
249 newTyVarsDs :: [TyVar] -> DsM [TyVar]
250 newTyVarsDs tyvar_tmpls = do
251 uniqs <- newUniqueSupply
252 return (zipWith setTyVarUnique tyvar_tmpls (uniqsFromSupply uniqs))
255 We can also reach out and either set/grab location information from
256 the @SrcSpan@ being carried around.
259 getDOptsDs :: DsM DynFlags
260 getDOptsDs = getDOpts
262 doptDs :: DynFlag -> TcRnIf gbl lcl Bool
265 getGhcModeDs :: DsM GhcMode
266 getGhcModeDs = getDOptsDs >>= return . ghcMode
268 getModuleDs :: DsM Module
269 getModuleDs = do { env <- getGblEnv; return (ds_mod env) }
271 getSrcSpanDs :: DsM SrcSpan
272 getSrcSpanDs = do { env <- getLclEnv; return (ds_loc env) }
274 putSrcSpanDs :: SrcSpan -> DsM a -> DsM a
275 putSrcSpanDs new_loc thing_inside = updLclEnv (\ env -> env {ds_loc = new_loc}) thing_inside
277 warnDs :: SDoc -> DsM ()
278 warnDs warn = do { env <- getGblEnv
279 ; loc <- getSrcSpanDs
280 ; let msg = mkWarnMsg loc (ds_unqual env)
281 (ptext SLIT("Warning:") <+> warn)
282 ; updMutVar (ds_msgs env) (\ (w,e) -> (w `snocBag` msg, e)) }
285 failWithDs :: SDoc -> DsM a
287 = do { env <- getGblEnv
288 ; loc <- getSrcSpanDs
289 ; let msg = mkErrMsg loc (ds_unqual env) err
290 ; updMutVar (ds_msgs env) (\ (w,e) -> (w, e `snocBag` msg))
296 dsLookupGlobal :: Name -> DsM TyThing
297 -- Very like TcEnv.tcLookupGlobal
299 = do { env <- getGblEnv
300 ; setEnvs (ds_if_env env)
301 (tcIfaceGlobal name) }
303 dsLookupGlobalId :: Name -> DsM Id
304 dsLookupGlobalId name
305 = tyThingId <$> dsLookupGlobal name
307 dsLookupTyCon :: Name -> DsM TyCon
309 = tyThingTyCon <$> dsLookupGlobal name
311 dsLookupDataCon :: Name -> DsM DataCon
313 = tyThingDataCon <$> dsLookupGlobal name
315 dsLookupClass :: Name -> DsM Class
317 = tyThingClass <$> dsLookupGlobal name
321 dsLookupMetaEnv :: Name -> DsM (Maybe DsMetaVal)
322 dsLookupMetaEnv name = do { env <- getLclEnv; return (lookupNameEnv (ds_meta env) name) }
324 dsExtendMetaEnv :: DsMetaEnv -> DsM a -> DsM a
325 dsExtendMetaEnv menv thing_inside
326 = updLclEnv (\env -> env { ds_meta = ds_meta env `plusNameEnv` menv }) thing_inside