2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcSplice]{Template Haskell splices}
7 module TcSplice( tcSpliceExpr, tcSpliceDecls, tcBracket ) where
9 #include "HsVersions.h"
11 import HscMain ( compileExpr )
12 import TcRnDriver ( tcTopSrcDecls )
13 -- These imports are the reason that TcSplice
14 -- is very high up the module hierarchy
16 import qualified Language.Haskell.TH as TH
17 -- THSyntax gives access to internal functions and data types
18 import qualified Language.Haskell.TH.Syntax as TH
20 import HsSyn ( HsBracket(..), HsExpr(..), HsSplice(..), LHsExpr, LHsDecl,
22 import Convert ( convertToHsExpr, convertToHsDecls, convertToHsType )
23 import RnExpr ( rnLExpr )
24 import RnEnv ( lookupFixityRn, lookupSrcOcc_maybe )
25 import RdrName ( RdrName, mkRdrUnqual, lookupLocalRdrEnv )
26 import RnTypes ( rnLHsType )
27 import TcExpr ( tcCheckRho, tcMonoExpr )
28 import TcHsSyn ( mkHsLet, zonkTopLExpr )
29 import TcSimplify ( tcSimplifyTop, tcSimplifyBracket )
30 import TcUnify ( Expected, zapExpectedTo, zapExpectedType )
31 import TcType ( TcType, TcKind, liftedTypeKind, mkAppTy, tcSplitSigmaTy )
32 import TcEnv ( spliceOK, tcMetaTy, bracketOK, tcLookup )
33 import TcMType ( newTyVarTy, newKindVar, UserTypeCtxt(ExprSigCtxt), zonkTcType, zonkTcTyVar )
34 import TcHsType ( tcHsSigType, kcHsType )
35 import TypeRep ( Type(..), PredType(..), TyThing(..) ) -- For reification
36 import Name ( Name, NamedThing(..), nameOccName, nameModule, isExternalName, mkInternalName )
38 import Var ( Id, TyVar, idType )
39 import Module ( moduleUserString, mkModuleName )
41 import IfaceEnv ( lookupOrig )
43 import Class ( Class, classBigSig )
44 import TyCon ( TyCon, tyConTheta, tyConTyVars, getSynTyConDefn, isSynTyCon, isNewTyCon, tyConDataCons )
45 import DataCon ( DataCon, dataConTyCon, dataConOrigArgTys, dataConStrictMarks,
46 dataConName, dataConFieldLabels, dataConWrapId )
47 import Id ( idName, globalIdDetails )
48 import IdInfo ( GlobalIdDetails(..) )
49 import TysWiredIn ( mkListTy )
50 import DsMeta ( expQTyConName, typeQTyConName, decTyConName, qTyConName, nameTyConName )
51 import ErrUtils ( Message )
52 import SrcLoc ( noLoc, unLoc, getLoc, noSrcLoc )
54 import Unique ( Unique, Uniquable(..), getKey, mkUniqueGrimily )
56 import BasicTypes ( StrictnessMark(..), Fixity(..), FixityDirection(..) )
57 import Panic ( showException )
58 import FastString ( LitString )
60 import GHC.Base ( unsafeCoerce#, Int#, Int(..) ) -- Should have a better home in the module hierarchy
61 import Monad ( liftM )
64 import FastString ( mkFastString )
69 %************************************************************************
71 \subsection{Main interface + stubs for the non-GHCI case
73 %************************************************************************
76 tcSpliceDecls :: LHsExpr Name -> TcM [LHsDecl RdrName]
77 tcSpliceExpr :: HsSplice Name -> Expected TcType -> TcM (HsExpr TcId)
78 kcSpliceType :: HsSplice Name -> TcM (HsType Name, TcKind)
81 tcSpliceExpr n e ty = pprPanic "Cant do tcSpliceExpr without GHCi" (ppr e)
82 tcSpliceDecls e = pprPanic "Cant do tcSpliceDecls without GHCi" (ppr e)
86 %************************************************************************
88 \subsection{Quoting an expression}
90 %************************************************************************
93 tcBracket :: HsBracket Name -> Expected TcType -> TcM (LHsExpr Id)
94 tcBracket brack res_ty
95 = getStage `thenM` \ level ->
96 case bracketOK level of {
97 Nothing -> failWithTc (illegalBracket level) ;
100 -- Typecheck expr to make sure it is valid,
101 -- but throw away the results. We'll type check
102 -- it again when we actually use it.
103 newMutVar [] `thenM` \ pending_splices ->
104 getLIEVar `thenM` \ lie_var ->
106 setStage (Brack next_level pending_splices lie_var) (
107 getLIE (tc_bracket brack)
108 ) `thenM` \ (meta_ty, lie) ->
109 tcSimplifyBracket lie `thenM_`
111 -- Make the expected type have the right shape
112 zapExpectedTo res_ty meta_ty `thenM_`
114 -- Return the original expression, not the type-decorated one
115 readMutVar pending_splices `thenM` \ pendings ->
116 returnM (noLoc (HsBracketOut brack pendings))
119 tc_bracket :: HsBracket Name -> TcM TcType
121 = tcMetaTy nameTyConName
122 -- Result type is Var (not Q-monadic)
124 tc_bracket (ExpBr expr)
125 = newTyVarTy liftedTypeKind `thenM` \ any_ty ->
126 tcCheckRho expr any_ty `thenM_`
127 tcMetaTy expQTyConName
128 -- Result type is Expr (= Q Exp)
130 tc_bracket (TypBr typ)
131 = tcHsSigType ExprSigCtxt typ `thenM_`
132 tcMetaTy typeQTyConName
133 -- Result type is Type (= Q Typ)
135 tc_bracket (DecBr decls)
136 = tcTopSrcDecls decls `thenM_`
137 -- Typecheck the declarations, dicarding the result
138 -- We'll get all that stuff later, when we splice it in
140 tcMetaTy decTyConName `thenM` \ decl_ty ->
141 tcMetaTy qTyConName `thenM` \ q_ty ->
142 returnM (mkAppTy q_ty (mkListTy decl_ty))
143 -- Result type is Q [Dec]
147 %************************************************************************
149 \subsection{Splicing an expression}
151 %************************************************************************
154 tcSpliceExpr (HsSplice name expr) res_ty
155 = addSrcSpan (getLoc expr) $
156 getStage `thenM` \ level ->
157 case spliceOK level of {
158 Nothing -> failWithTc (illegalSplice level) ;
162 Comp -> do { e <- tcTopSplice expr res_ty ;
164 Brack _ ps_var lie_var ->
166 -- A splice inside brackets
167 -- NB: ignore res_ty, apart from zapping it to a mono-type
168 -- e.g. [| reverse $(h 4) |]
169 -- Here (h 4) :: Q Exp
170 -- but $(h 4) :: forall a.a i.e. anything!
172 zapExpectedType res_ty liftedTypeKind `thenM_`
173 tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
174 setStage (Splice next_level) (
176 tcCheckRho expr meta_exp_ty
179 -- Write the pending splice into the bucket
180 readMutVar ps_var `thenM` \ ps ->
181 writeMutVar ps_var ((name,expr') : ps) `thenM_`
183 returnM (panic "tcSpliceExpr") -- The returned expression is ignored
186 -- tcTopSplice used to have this:
187 -- Note that we do not decrement the level (to -1) before
188 -- typechecking the expression. For example:
189 -- f x = $( ...$(g 3) ... )
190 -- The recursive call to tcMonoExpr will simply expand the
191 -- inner escape before dealing with the outer one
193 tcTopSplice :: LHsExpr Name -> Expected TcType -> TcM (LHsExpr Id)
194 tcTopSplice expr res_ty
195 = tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
197 -- Typecheck the expression
198 tcTopSpliceExpr expr meta_exp_ty `thenM` \ zonked_q_expr ->
200 -- Run the expression
201 traceTc (text "About to run" <+> ppr zonked_q_expr) `thenM_`
202 runMetaE zonked_q_expr `thenM` \ simple_expr ->
205 -- simple_expr :: TH.Exp
207 expr2 :: LHsExpr RdrName
208 expr2 = convertToHsExpr simple_expr
210 traceTc (text "Got result" <+> ppr expr2) `thenM_`
212 showSplice "expression"
213 zonked_q_expr (ppr expr2) `thenM_`
215 -- Rename it, but bale out if there are errors
216 -- otherwise the type checker just gives more spurious errors
217 checkNoErrs (rnLExpr expr2) `thenM` \ (exp3, fvs) ->
219 tcMonoExpr exp3 res_ty
222 tcTopSpliceExpr :: LHsExpr Name -> TcType -> TcM (LHsExpr Id)
223 -- Type check an expression that is the body of a top-level splice
224 -- (the caller will compile and run it)
225 tcTopSpliceExpr expr meta_ty
226 = checkNoErrs $ -- checkNoErrs: must not try to run the thing
227 -- if the type checker fails!
229 setStage topSpliceStage $
231 -- Typecheck the expression
232 getLIE (tcCheckRho expr meta_ty) `thenM` \ (expr', lie) ->
234 -- Solve the constraints
235 tcSimplifyTop lie `thenM` \ const_binds ->
238 zonkTopLExpr (mkHsLet const_binds expr')
242 %************************************************************************
246 %************************************************************************
248 Very like splicing an expression, but we don't yet share code.
251 kcSpliceType (HsSplice name hs_expr)
252 = addSrcSpan (getLoc hs_expr) $ do
254 ; case spliceOK level of {
255 Nothing -> failWithTc (illegalSplice level) ;
256 Just next_level -> do
259 Comp -> do { (t,k) <- kcTopSpliceType hs_expr
260 ; return (unLoc t, k) } ;
261 Brack _ ps_var lie_var -> do
263 { -- A splice inside brackets
264 ; meta_ty <- tcMetaTy typeQTyConName
265 ; expr' <- setStage (Splice next_level) $
267 tcCheckRho hs_expr meta_ty
269 -- Write the pending splice into the bucket
270 ; ps <- readMutVar ps_var
271 ; writeMutVar ps_var ((name,expr') : ps)
273 -- e.g. [| Int -> $(h 4) |]
274 -- Here (h 4) :: Q Type
275 -- but $(h 4) :: forall a.a i.e. any kind
277 ; returnM (panic "kcSpliceType", kind) -- The returned type is ignored
280 kcTopSpliceType :: LHsExpr Name -> TcM (LHsType Name, TcKind)
282 = do { meta_ty <- tcMetaTy typeQTyConName
284 -- Typecheck the expression
285 ; zonked_q_expr <- tcTopSpliceExpr expr meta_ty
287 -- Run the expression
288 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
289 ; simple_ty <- runMetaT zonked_q_expr
291 ; let -- simple_ty :: TH.Type
292 hs_ty2 :: LHsType RdrName
293 hs_ty2 = convertToHsType simple_ty
295 ; traceTc (text "Got result" <+> ppr hs_ty2)
297 ; showSplice "type" zonked_q_expr (ppr hs_ty2)
299 -- Rename it, but bale out if there are errors
300 -- otherwise the type checker just gives more spurious errors
301 ; let doc = ptext SLIT("In the spliced type") <+> ppr hs_ty2
302 ; hs_ty3 <- checkNoErrs (rnLHsType doc hs_ty2)
307 %************************************************************************
309 \subsection{Splicing an expression}
311 %************************************************************************
314 -- Always at top level
316 = do { meta_dec_ty <- tcMetaTy decTyConName
317 ; meta_q_ty <- tcMetaTy qTyConName
318 ; let list_q = mkAppTy meta_q_ty (mkListTy meta_dec_ty)
319 ; zonked_q_expr <- tcTopSpliceExpr expr list_q
321 -- Run the expression
322 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
323 ; simple_expr <- runMetaD zonked_q_expr
325 -- simple_expr :: [TH.Dec]
326 -- decls :: [RdrNameHsDecl]
327 ; decls <- handleErrors (convertToHsDecls simple_expr)
328 ; traceTc (text "Got result" <+> vcat (map ppr decls))
329 ; showSplice "declarations"
330 zonked_q_expr (vcat (map ppr decls))
333 where handleErrors :: [Either a Message] -> TcM [a]
334 handleErrors [] = return []
335 handleErrors (Left x:xs) = liftM (x:) (handleErrors xs)
336 handleErrors (Right m:xs) = do addErrTc m
341 %************************************************************************
343 \subsection{Running an expression}
345 %************************************************************************
348 runMetaE :: LHsExpr Id -- Of type (Q Exp)
349 -> TcM TH.Exp -- Of type Exp
350 runMetaE e = runMeta e
352 runMetaT :: LHsExpr Id -- Of type (Q Type)
353 -> TcM TH.Type -- Of type Type
354 runMetaT e = runMeta e
356 runMetaD :: LHsExpr Id -- Of type Q [Dec]
357 -> TcM [TH.Dec] -- Of type [Dec]
358 runMetaD e = runMeta e
360 runMeta :: LHsExpr Id -- Of type X
361 -> TcM t -- Of type t
363 = do { hsc_env <- getTopEnv
364 ; tcg_env <- getGblEnv
365 ; this_mod <- getModule
366 ; let type_env = tcg_type_env tcg_env
367 rdr_env = tcg_rdr_env tcg_env
368 -- Wrap the compile-and-run in an exception-catcher
369 -- Compiling might fail if linking fails
370 -- Running might fail if it throws an exception
371 ; either_tval <- tryM $ do
373 hval <- ioToTcRn (HscMain.compileExpr
375 rdr_env type_env expr)
376 -- Coerce it to Q t, and run it
377 ; TH.runQ (unsafeCoerce# hval) }
379 ; case either_tval of
380 Left exn -> failWithTc (vcat [text "Exception when trying to run compile-time code:",
381 nest 4 (vcat [text "Code:" <+> ppr expr,
382 text ("Exn: " ++ Panic.showException exn)])])
383 Right v -> returnM v }
386 To call runQ in the Tc monad, we need to make TcM an instance of Quasi:
389 instance TH.Quasi (IOEnv (Env TcGblEnv TcLclEnv)) where
390 qNewName s = do { u <- newUnique
392 ; return (TH.mkNameU s i) }
394 qReport True msg = addErr (text msg)
395 qReport False msg = addReport (text msg)
397 qCurrentModule = do { m <- getModule; return (moduleUserString m) }
401 qRunIO io = ioToTcRn io
405 %************************************************************************
407 \subsection{Errors and contexts}
409 %************************************************************************
412 showSplice :: String -> LHsExpr Id -> SDoc -> TcM ()
413 showSplice what before after
414 = getSrcSpanM `thenM` \ loc ->
415 traceSplice (vcat [ppr loc <> colon <+> text "Splicing" <+> text what,
416 nest 2 (sep [nest 2 (ppr before),
421 = ptext SLIT("Illegal bracket at level") <+> ppr level
424 = ptext SLIT("Illegal splice at level") <+> ppr level
430 %************************************************************************
434 %************************************************************************
438 reify :: TH.Name -> TcM TH.Info
440 = do { name <- lookupThName th_name
441 ; thing <- tcLookup name
442 -- ToDo: this tcLookup could fail, which would give a
443 -- rather unhelpful error message
447 lookupThName :: TH.Name -> TcM Name
448 lookupThName (TH.Name occ (TH.NameG th_ns mod))
449 = lookupOrig (mkModuleName (TH.modString mod))
450 (OccName.mkOccName ghc_ns (TH.occString occ))
452 ghc_ns = case th_ns of
453 TH.DataName -> dataName
454 TH.TcClsName -> tcClsName
455 TH.VarName -> varName
457 lookupThName th_name@(TH.Name occ TH.NameS)
458 = do { let rdr_name = mkRdrUnqual (OccName.mkOccFS ns occ_fs)
459 ; rdr_env <- getLocalRdrEnv
460 ; case lookupLocalRdrEnv rdr_env rdr_name of
461 Just name -> return name
463 { mb_name <- lookupSrcOcc_maybe rdr_name
465 Just name -> return name ;
466 Nothing -> failWithTc (notInScope th_name)
469 ns | isLexCon occ_fs = OccName.dataName
470 | otherwise = OccName.varName
471 occ_fs = mkFastString (TH.occString occ)
473 lookupThName (TH.Name occ (TH.NameU uniq))
474 = return (mkInternalName (mk_uniq uniq) (OccName.mkOccFS bogus_ns occ_fs) noSrcLoc)
476 occ_fs = mkFastString (TH.occString occ)
477 bogus_ns = OccName.varName -- Not yet recorded in the TH name
478 -- but only the unique matters
480 mk_uniq :: Int# -> Unique
481 mk_uniq u = mkUniqueGrimily (I# u)
483 notInScope :: TH.Name -> SDoc
484 notInScope th_name = quotes (text (TH.pprint th_name)) <+>
485 ptext SLIT("is not in scope at a reify")
486 -- Ugh! Rather an indirect way to display the name
488 ------------------------------
489 reifyThing :: TcTyThing -> TcM TH.Info
490 -- The only reason this is monadic is for error reporting,
491 -- which in turn is mainly for the case when TH can't express
492 -- some random GHC extension
494 reifyThing (AGlobal (AnId id))
495 = do { ty <- reifyType (idType id)
496 ; fix <- reifyFixity (idName id)
497 ; let v = reifyName id
498 ; case globalIdDetails id of
499 ClassOpId cls -> return (TH.ClassOpI v ty (reifyName cls) fix)
500 other -> return (TH.VarI v ty Nothing fix)
503 reifyThing (AGlobal (ATyCon tc)) = do { dec <- reifyTyCon tc; return (TH.TyConI dec) }
504 reifyThing (AGlobal (AClass cls)) = do { dec <- reifyClass cls; return (TH.ClassI dec) }
505 reifyThing (AGlobal (ADataCon dc))
506 = do { let name = dataConName dc
507 ; ty <- reifyType (idType (dataConWrapId dc))
508 ; fix <- reifyFixity name
509 ; return (TH.DataConI (reifyName name) ty (reifyName (dataConTyCon dc)) fix) }
511 reifyThing (ATcId id _ _)
512 = do { ty1 <- zonkTcType (idType id) -- Make use of all the info we have, even
513 -- though it may be incomplete
514 ; ty2 <- reifyType ty1
515 ; fix <- reifyFixity (idName id)
516 ; return (TH.VarI (reifyName id) ty2 Nothing fix) }
518 reifyThing (ATyVar tv)
519 = do { ty1 <- zonkTcTyVar tv
520 ; ty2 <- reifyType ty1
521 ; return (TH.TyVarI (reifyName tv) ty2) }
523 ------------------------------
524 reifyTyCon :: TyCon -> TcM TH.Dec
527 = do { let (tvs, rhs) = getSynTyConDefn tc
528 ; rhs' <- reifyType rhs
529 ; return (TH.TySynD (reifyName tc) (reifyTyVars tvs) rhs') }
532 = do { cxt <- reifyCxt (tyConTheta tc)
533 ; con <- reifyDataCon (head (tyConDataCons tc))
534 ; return (TH.NewtypeD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
535 con [{- Don't know about deriving -}]) }
537 | otherwise -- Algebraic
538 = do { cxt <- reifyCxt (tyConTheta tc)
539 ; cons <- mapM reifyDataCon (tyConDataCons tc)
540 ; return (TH.DataD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
541 cons [{- Don't know about deriving -}]) }
543 reifyDataCon :: DataCon -> TcM TH.Con
545 = do { arg_tys <- reifyTypes (dataConOrigArgTys dc)
546 ; let stricts = map reifyStrict (dataConStrictMarks dc)
547 fields = dataConFieldLabels dc
548 ; if null fields then
549 return (TH.NormalC (reifyName dc) (stricts `zip` arg_tys))
551 return (TH.RecC (reifyName dc) (zip3 (map reifyName fields) stricts arg_tys)) }
552 -- NB: we don't remember whether the constructor was declared in an infix way
554 ------------------------------
555 reifyClass :: Class -> TcM TH.Dec
557 = do { cxt <- reifyCxt theta
558 ; ops <- mapM reify_op op_stuff
559 ; return (TH.ClassD cxt (reifyName cls) (reifyTyVars tvs) ops) }
561 (tvs, theta, _, op_stuff) = classBigSig cls
562 reify_op (op, _) = do { ty <- reifyType (idType op)
563 ; return (TH.SigD (reifyName op) ty) }
565 ------------------------------
566 reifyType :: TypeRep.Type -> TcM TH.Type
567 reifyType (TyVarTy tv) = return (TH.VarT (reifyName tv))
568 reifyType (TyConApp tc tys) = reify_tc_app (reifyName tc) tys
569 reifyType (NewTcApp tc tys) = reify_tc_app (reifyName tc) tys
570 reifyType (NoteTy _ ty) = reifyType ty
571 reifyType (AppTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (r1 `TH.AppT` r2) }
572 reifyType (FunTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (TH.ArrowT `TH.AppT` r1 `TH.AppT` r2) }
573 reifyType ty@(ForAllTy _ _) = do { cxt' <- reifyCxt cxt;
574 ; tau' <- reifyType tau
575 ; return (TH.ForallT (reifyTyVars tvs) cxt' tau') }
577 (tvs, cxt, tau) = tcSplitSigmaTy ty
578 reifyTypes = mapM reifyType
579 reifyCxt = mapM reifyPred
581 reifyTyVars :: [TyVar] -> [TH.Name]
582 reifyTyVars = map reifyName
584 reify_tc_app :: TH.Name -> [TypeRep.Type] -> TcM TH.Type
585 reify_tc_app tc tys = do { tys' <- reifyTypes tys
586 ; return (foldl TH.AppT (TH.ConT tc) tys') }
588 reifyPred :: TypeRep.PredType -> TcM TH.Type
589 reifyPred (ClassP cls tys) = reify_tc_app (reifyName cls) tys
590 reifyPred p@(IParam _ _) = noTH SLIT("implicit parameters") (ppr p)
593 ------------------------------
594 reifyName :: NamedThing n => n -> TH.Name
596 | isExternalName name = mk_varg mod occ_str
597 | otherwise = TH.mkNameU occ_str (getKey (getUnique name))
600 mod = moduleUserString (nameModule name)
601 occ_str = occNameUserString occ
602 occ = nameOccName name
603 mk_varg | OccName.isDataOcc occ = TH.mkNameG_d
604 | OccName.isVarOcc occ = TH.mkNameG_v
605 | OccName.isTcOcc occ = TH.mkNameG_tc
606 | otherwise = pprPanic "reifyName" (ppr name)
608 ------------------------------
609 reifyFixity :: Name -> TcM TH.Fixity
611 = do { fix <- lookupFixityRn name
612 ; return (conv_fix fix) }
614 conv_fix (BasicTypes.Fixity i d) = TH.Fixity i (conv_dir d)
615 conv_dir BasicTypes.InfixR = TH.InfixR
616 conv_dir BasicTypes.InfixL = TH.InfixL
617 conv_dir BasicTypes.InfixN = TH.InfixN
619 reifyStrict :: BasicTypes.StrictnessMark -> TH.Strict
620 reifyStrict MarkedStrict = TH.IsStrict
621 reifyStrict MarkedUnboxed = TH.IsStrict
622 reifyStrict NotMarkedStrict = TH.NotStrict
624 ------------------------------
625 noTH :: LitString -> SDoc -> TcM a
626 noTH s d = failWithTc (hsep [ptext SLIT("Can't represent") <+> ptext s <+>
627 ptext SLIT("in Template Haskell:"),