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.
104 newMutVar [] `thenM` \ pending_splices ->
105 getLIEVar `thenM` \ lie_var ->
107 setStage (Brack next_level pending_splices lie_var) (
108 getLIE (tc_bracket brack)
109 ) `thenM` \ (meta_ty, lie) ->
110 tcSimplifyBracket lie `thenM_`
112 -- Make the expected type have the right shape
113 zapExpectedTo res_ty meta_ty `thenM_`
115 -- Return the original expression, not the type-decorated one
116 readMutVar pending_splices `thenM` \ pendings ->
117 returnM (noLoc (HsBracketOut brack pendings))
120 tc_bracket :: HsBracket Name -> TcM TcType
122 = tcMetaTy nameTyConName
123 -- Result type is Var (not Q-monadic)
125 tc_bracket (ExpBr expr)
126 = newTyVarTy liftedTypeKind `thenM` \ any_ty ->
127 tcCheckRho expr any_ty `thenM_`
128 tcMetaTy expQTyConName
129 -- Result type is Expr (= Q Exp)
131 tc_bracket (TypBr typ)
132 = tcHsSigType ExprSigCtxt typ `thenM_`
133 tcMetaTy typeQTyConName
134 -- Result type is Type (= Q Typ)
136 tc_bracket (DecBr decls)
137 = tcTopSrcDecls decls `thenM_`
138 -- Typecheck the declarations, dicarding the result
139 -- We'll get all that stuff later, when we splice it in
141 tcMetaTy decTyConName `thenM` \ decl_ty ->
142 tcMetaTy qTyConName `thenM` \ q_ty ->
143 returnM (mkAppTy q_ty (mkListTy decl_ty))
144 -- Result type is Q [Dec]
148 %************************************************************************
150 \subsection{Splicing an expression}
152 %************************************************************************
155 tcSpliceExpr (HsSplice name expr) res_ty
156 = addSrcSpan (getLoc expr) $
157 getStage `thenM` \ level ->
158 case spliceOK level of {
159 Nothing -> failWithTc (illegalSplice level) ;
163 Comp -> do { e <- tcTopSplice expr res_ty
164 ; returnM (unLoc e) } ;
165 Brack _ ps_var lie_var ->
167 -- A splice inside brackets
168 -- NB: ignore res_ty, apart from zapping it to a mono-type
169 -- e.g. [| reverse $(h 4) |]
170 -- Here (h 4) :: Q Exp
171 -- but $(h 4) :: forall a.a i.e. anything!
173 zapExpectedType res_ty liftedTypeKind `thenM_`
174 tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
175 setStage (Splice next_level) (
177 tcCheckRho expr meta_exp_ty
180 -- Write the pending splice into the bucket
181 readMutVar ps_var `thenM` \ ps ->
182 writeMutVar ps_var ((name,expr') : ps) `thenM_`
184 returnM (panic "tcSpliceExpr") -- The returned expression is ignored
187 -- tcTopSplice used to have this:
188 -- Note that we do not decrement the level (to -1) before
189 -- typechecking the expression. For example:
190 -- f x = $( ...$(g 3) ... )
191 -- The recursive call to tcMonoExpr will simply expand the
192 -- inner escape before dealing with the outer one
194 tcTopSplice :: LHsExpr Name -> Expected TcType -> TcM (LHsExpr Id)
195 tcTopSplice expr res_ty
196 = tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
198 -- Typecheck the expression
199 tcTopSpliceExpr expr meta_exp_ty `thenM` \ zonked_q_expr ->
201 -- Run the expression
202 traceTc (text "About to run" <+> ppr zonked_q_expr) `thenM_`
203 runMetaE zonked_q_expr `thenM` \ simple_expr ->
206 -- simple_expr :: TH.Exp
208 expr2 :: LHsExpr RdrName
209 expr2 = convertToHsExpr simple_expr
211 traceTc (text "Got result" <+> ppr expr2) `thenM_`
213 showSplice "expression"
214 zonked_q_expr (ppr expr2) `thenM_`
216 -- Rename it, but bale out if there are errors
217 -- otherwise the type checker just gives more spurious errors
218 checkNoErrs (rnLExpr expr2) `thenM` \ (exp3, fvs) ->
220 tcMonoExpr exp3 res_ty
223 tcTopSpliceExpr :: LHsExpr Name -> TcType -> TcM (LHsExpr Id)
224 -- Type check an expression that is the body of a top-level splice
225 -- (the caller will compile and run it)
226 tcTopSpliceExpr expr meta_ty
227 = checkNoErrs $ -- checkNoErrs: must not try to run the thing
228 -- if the type checker fails!
230 setStage topSpliceStage $ do
233 do { recordThUse -- Record that TH is used (for pkg depdendency)
235 -- Typecheck the expression
236 ; (expr', lie) <- getLIE (tcCheckRho expr meta_ty)
238 -- Solve the constraints
239 ; const_binds <- tcSimplifyTop lie
242 ; zonkTopLExpr (mkHsLet const_binds expr') }
246 %************************************************************************
250 %************************************************************************
252 Very like splicing an expression, but we don't yet share code.
255 kcSpliceType (HsSplice name hs_expr)
256 = addSrcSpan (getLoc hs_expr) $ do
258 ; case spliceOK level of {
259 Nothing -> failWithTc (illegalSplice level) ;
260 Just next_level -> do
263 Comp -> do { (t,k) <- kcTopSpliceType hs_expr
264 ; return (unLoc t, k) } ;
265 Brack _ ps_var lie_var -> do
267 { -- A splice inside brackets
268 ; meta_ty <- tcMetaTy typeQTyConName
269 ; expr' <- setStage (Splice next_level) $
271 tcCheckRho hs_expr meta_ty
273 -- Write the pending splice into the bucket
274 ; ps <- readMutVar ps_var
275 ; writeMutVar ps_var ((name,expr') : ps)
277 -- e.g. [| Int -> $(h 4) |]
278 -- Here (h 4) :: Q Type
279 -- but $(h 4) :: forall a.a i.e. any kind
281 ; returnM (panic "kcSpliceType", kind) -- The returned type is ignored
284 kcTopSpliceType :: LHsExpr Name -> TcM (LHsType Name, TcKind)
286 = do { meta_ty <- tcMetaTy typeQTyConName
288 -- Typecheck the expression
289 ; zonked_q_expr <- tcTopSpliceExpr expr meta_ty
291 -- Run the expression
292 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
293 ; simple_ty <- runMetaT zonked_q_expr
295 ; let -- simple_ty :: TH.Type
296 hs_ty2 :: LHsType RdrName
297 hs_ty2 = convertToHsType simple_ty
299 ; traceTc (text "Got result" <+> ppr hs_ty2)
301 ; showSplice "type" zonked_q_expr (ppr hs_ty2)
303 -- Rename it, but bale out if there are errors
304 -- otherwise the type checker just gives more spurious errors
305 ; let doc = ptext SLIT("In the spliced type") <+> ppr hs_ty2
306 ; hs_ty3 <- checkNoErrs (rnLHsType doc hs_ty2)
311 %************************************************************************
313 \subsection{Splicing an expression}
315 %************************************************************************
318 -- Always at top level
320 = do { meta_dec_ty <- tcMetaTy decTyConName
321 ; meta_q_ty <- tcMetaTy qTyConName
322 ; let list_q = mkAppTy meta_q_ty (mkListTy meta_dec_ty)
323 ; zonked_q_expr <- tcTopSpliceExpr expr list_q
325 -- Run the expression
326 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
327 ; simple_expr <- runMetaD zonked_q_expr
329 -- simple_expr :: [TH.Dec]
330 -- decls :: [RdrNameHsDecl]
331 ; decls <- handleErrors (convertToHsDecls simple_expr)
332 ; traceTc (text "Got result" <+> vcat (map ppr decls))
333 ; showSplice "declarations"
334 zonked_q_expr (vcat (map ppr decls))
337 where handleErrors :: [Either a Message] -> TcM [a]
338 handleErrors [] = return []
339 handleErrors (Left x:xs) = liftM (x:) (handleErrors xs)
340 handleErrors (Right m:xs) = do addErrTc m
345 %************************************************************************
347 \subsection{Running an expression}
349 %************************************************************************
352 runMetaE :: LHsExpr Id -- Of type (Q Exp)
353 -> TcM TH.Exp -- Of type Exp
354 runMetaE e = runMeta e
356 runMetaT :: LHsExpr Id -- Of type (Q Type)
357 -> TcM TH.Type -- Of type Type
358 runMetaT e = runMeta e
360 runMetaD :: LHsExpr Id -- Of type Q [Dec]
361 -> TcM [TH.Dec] -- Of type [Dec]
362 runMetaD e = runMeta e
364 runMeta :: LHsExpr Id -- Of type X
365 -> TcM t -- Of type t
367 = do { hsc_env <- getTopEnv
368 ; tcg_env <- getGblEnv
369 ; this_mod <- getModule
370 ; let type_env = tcg_type_env tcg_env
371 rdr_env = tcg_rdr_env tcg_env
372 -- Wrap the compile-and-run in an exception-catcher
373 -- Compiling might fail if linking fails
374 -- Running might fail if it throws an exception
375 ; either_tval <- tryM $ do
377 hval <- ioToTcRn (HscMain.compileExpr
379 rdr_env type_env expr)
380 -- Coerce it to Q t, and run it
381 ; TH.runQ (unsafeCoerce# hval) }
383 ; case either_tval of
384 Left exn -> failWithTc (vcat [text "Exception when trying to run compile-time code:",
385 nest 4 (vcat [text "Code:" <+> ppr expr,
386 text ("Exn: " ++ Panic.showException exn)])])
387 Right v -> returnM v }
390 To call runQ in the Tc monad, we need to make TcM an instance of Quasi:
393 instance TH.Quasi (IOEnv (Env TcGblEnv TcLclEnv)) where
394 qNewName s = do { u <- newUnique
396 ; return (TH.mkNameU s i) }
398 qReport True msg = addErr (text msg)
399 qReport False msg = addReport (text msg)
401 qCurrentModule = do { m <- getModule; return (moduleUserString m) }
405 qRunIO io = ioToTcRn io
409 %************************************************************************
411 \subsection{Errors and contexts}
413 %************************************************************************
416 showSplice :: String -> LHsExpr Id -> SDoc -> TcM ()
417 showSplice what before after
418 = getSrcSpanM `thenM` \ loc ->
419 traceSplice (vcat [ppr loc <> colon <+> text "Splicing" <+> text what,
420 nest 2 (sep [nest 2 (ppr before),
425 = ptext SLIT("Illegal bracket at level") <+> ppr level
428 = ptext SLIT("Illegal splice at level") <+> ppr level
434 %************************************************************************
438 %************************************************************************
442 reify :: TH.Name -> TcM TH.Info
444 = do { name <- lookupThName th_name
445 ; thing <- tcLookup name
446 -- ToDo: this tcLookup could fail, which would give a
447 -- rather unhelpful error message
451 lookupThName :: TH.Name -> TcM Name
452 lookupThName (TH.Name occ (TH.NameG th_ns mod))
453 = lookupOrig (mkModuleName (TH.modString mod))
454 (OccName.mkOccName ghc_ns (TH.occString occ))
456 ghc_ns = case th_ns of
457 TH.DataName -> dataName
458 TH.TcClsName -> tcClsName
459 TH.VarName -> varName
461 lookupThName th_name@(TH.Name occ TH.NameS)
462 = do { let rdr_name = mkRdrUnqual (OccName.mkOccFS ns occ_fs)
463 ; rdr_env <- getLocalRdrEnv
464 ; case lookupLocalRdrEnv rdr_env rdr_name of
465 Just name -> return name
467 { mb_name <- lookupSrcOcc_maybe rdr_name
469 Just name -> return name ;
470 Nothing -> failWithTc (notInScope th_name)
473 ns | isLexCon occ_fs = OccName.dataName
474 | otherwise = OccName.varName
475 occ_fs = mkFastString (TH.occString occ)
477 lookupThName (TH.Name occ (TH.NameU uniq))
478 = return (mkInternalName (mk_uniq uniq) (OccName.mkOccFS bogus_ns occ_fs) noSrcLoc)
480 occ_fs = mkFastString (TH.occString occ)
481 bogus_ns = OccName.varName -- Not yet recorded in the TH name
482 -- but only the unique matters
484 mk_uniq :: Int# -> Unique
485 mk_uniq u = mkUniqueGrimily (I# u)
487 notInScope :: TH.Name -> SDoc
488 notInScope th_name = quotes (text (TH.pprint th_name)) <+>
489 ptext SLIT("is not in scope at a reify")
490 -- Ugh! Rather an indirect way to display the name
492 ------------------------------
493 reifyThing :: TcTyThing -> TcM TH.Info
494 -- The only reason this is monadic is for error reporting,
495 -- which in turn is mainly for the case when TH can't express
496 -- some random GHC extension
498 reifyThing (AGlobal (AnId id))
499 = do { ty <- reifyType (idType id)
500 ; fix <- reifyFixity (idName id)
501 ; let v = reifyName id
502 ; case globalIdDetails id of
503 ClassOpId cls -> return (TH.ClassOpI v ty (reifyName cls) fix)
504 other -> return (TH.VarI v ty Nothing fix)
507 reifyThing (AGlobal (ATyCon tc)) = do { dec <- reifyTyCon tc; return (TH.TyConI dec) }
508 reifyThing (AGlobal (AClass cls)) = do { dec <- reifyClass cls; return (TH.ClassI dec) }
509 reifyThing (AGlobal (ADataCon dc))
510 = do { let name = dataConName dc
511 ; ty <- reifyType (idType (dataConWrapId dc))
512 ; fix <- reifyFixity name
513 ; return (TH.DataConI (reifyName name) ty (reifyName (dataConTyCon dc)) fix) }
515 reifyThing (ATcId id _ _)
516 = do { ty1 <- zonkTcType (idType id) -- Make use of all the info we have, even
517 -- though it may be incomplete
518 ; ty2 <- reifyType ty1
519 ; fix <- reifyFixity (idName id)
520 ; return (TH.VarI (reifyName id) ty2 Nothing fix) }
522 reifyThing (ATyVar tv)
523 = do { ty1 <- zonkTcTyVar tv
524 ; ty2 <- reifyType ty1
525 ; return (TH.TyVarI (reifyName tv) ty2) }
527 ------------------------------
528 reifyTyCon :: TyCon -> TcM TH.Dec
531 = do { let (tvs, rhs) = getSynTyConDefn tc
532 ; rhs' <- reifyType rhs
533 ; return (TH.TySynD (reifyName tc) (reifyTyVars tvs) rhs') }
536 = do { cxt <- reifyCxt (tyConTheta tc)
537 ; con <- reifyDataCon (head (tyConDataCons tc))
538 ; return (TH.NewtypeD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
539 con [{- Don't know about deriving -}]) }
541 | otherwise -- Algebraic
542 = do { cxt <- reifyCxt (tyConTheta tc)
543 ; cons <- mapM reifyDataCon (tyConDataCons tc)
544 ; return (TH.DataD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
545 cons [{- Don't know about deriving -}]) }
547 reifyDataCon :: DataCon -> TcM TH.Con
549 = do { arg_tys <- reifyTypes (dataConOrigArgTys dc)
550 ; let stricts = map reifyStrict (dataConStrictMarks dc)
551 fields = dataConFieldLabels dc
552 ; if null fields then
553 return (TH.NormalC (reifyName dc) (stricts `zip` arg_tys))
555 return (TH.RecC (reifyName dc) (zip3 (map reifyName fields) stricts arg_tys)) }
556 -- NB: we don't remember whether the constructor was declared in an infix way
558 ------------------------------
559 reifyClass :: Class -> TcM TH.Dec
561 = do { cxt <- reifyCxt theta
562 ; ops <- mapM reify_op op_stuff
563 ; return (TH.ClassD cxt (reifyName cls) (reifyTyVars tvs) ops) }
565 (tvs, theta, _, op_stuff) = classBigSig cls
566 reify_op (op, _) = do { ty <- reifyType (idType op)
567 ; return (TH.SigD (reifyName op) ty) }
569 ------------------------------
570 reifyType :: TypeRep.Type -> TcM TH.Type
571 reifyType (TyVarTy tv) = return (TH.VarT (reifyName tv))
572 reifyType (TyConApp tc tys) = reify_tc_app (reifyName tc) tys
573 reifyType (NewTcApp tc tys) = reify_tc_app (reifyName tc) tys
574 reifyType (NoteTy _ ty) = reifyType ty
575 reifyType (AppTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (r1 `TH.AppT` r2) }
576 reifyType (FunTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (TH.ArrowT `TH.AppT` r1 `TH.AppT` r2) }
577 reifyType ty@(ForAllTy _ _) = do { cxt' <- reifyCxt cxt;
578 ; tau' <- reifyType tau
579 ; return (TH.ForallT (reifyTyVars tvs) cxt' tau') }
581 (tvs, cxt, tau) = tcSplitSigmaTy ty
582 reifyTypes = mapM reifyType
583 reifyCxt = mapM reifyPred
585 reifyTyVars :: [TyVar] -> [TH.Name]
586 reifyTyVars = map reifyName
588 reify_tc_app :: TH.Name -> [TypeRep.Type] -> TcM TH.Type
589 reify_tc_app tc tys = do { tys' <- reifyTypes tys
590 ; return (foldl TH.AppT (TH.ConT tc) tys') }
592 reifyPred :: TypeRep.PredType -> TcM TH.Type
593 reifyPred (ClassP cls tys) = reify_tc_app (reifyName cls) tys
594 reifyPred p@(IParam _ _) = noTH SLIT("implicit parameters") (ppr p)
597 ------------------------------
598 reifyName :: NamedThing n => n -> TH.Name
600 | isExternalName name = mk_varg mod occ_str
601 | otherwise = TH.mkNameU occ_str (getKey (getUnique name))
604 mod = moduleUserString (nameModule name)
605 occ_str = occNameUserString occ
606 occ = nameOccName name
607 mk_varg | OccName.isDataOcc occ = TH.mkNameG_d
608 | OccName.isVarOcc occ = TH.mkNameG_v
609 | OccName.isTcOcc occ = TH.mkNameG_tc
610 | otherwise = pprPanic "reifyName" (ppr name)
612 ------------------------------
613 reifyFixity :: Name -> TcM TH.Fixity
615 = do { fix <- lookupFixityRn name
616 ; return (conv_fix fix) }
618 conv_fix (BasicTypes.Fixity i d) = TH.Fixity i (conv_dir d)
619 conv_dir BasicTypes.InfixR = TH.InfixR
620 conv_dir BasicTypes.InfixL = TH.InfixL
621 conv_dir BasicTypes.InfixN = TH.InfixN
623 reifyStrict :: BasicTypes.StrictnessMark -> TH.Strict
624 reifyStrict MarkedStrict = TH.IsStrict
625 reifyStrict MarkedUnboxed = TH.IsStrict
626 reifyStrict NotMarkedStrict = TH.NotStrict
628 ------------------------------
629 noTH :: LitString -> SDoc -> TcM a
630 noTH s d = failWithTc (hsep [ptext SLIT("Can't represent") <+> ptext s <+>
631 ptext SLIT("in Template Haskell:"),