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.THSyntax as TH
17 import qualified Language.Haskell.TH.THLib as TH
18 -- THSyntax gives access to internal functions and data types
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 )
65 %************************************************************************
67 \subsection{Main interface + stubs for the non-GHCI case
69 %************************************************************************
72 tcSpliceDecls :: LHsExpr Name -> TcM [LHsDecl RdrName]
73 tcSpliceExpr :: HsSplice Name -> Expected TcType -> TcM (HsExpr TcId)
74 kcSpliceType :: HsSplice Name -> TcM (HsType Name, TcKind)
77 tcSpliceExpr n e ty = pprPanic "Cant do tcSpliceExpr without GHCi" (ppr e)
78 tcSpliceDecls e = pprPanic "Cant do tcSpliceDecls without GHCi" (ppr e)
82 %************************************************************************
84 \subsection{Quoting an expression}
86 %************************************************************************
89 tcBracket :: HsBracket Name -> Expected TcType -> TcM (LHsExpr Id)
90 tcBracket brack res_ty
91 = getStage `thenM` \ level ->
92 case bracketOK level of {
93 Nothing -> failWithTc (illegalBracket level) ;
96 -- Typecheck expr to make sure it is valid,
97 -- but throw away the results. We'll type check
98 -- it again when we actually use it.
99 newMutVar [] `thenM` \ pending_splices ->
100 getLIEVar `thenM` \ lie_var ->
102 setStage (Brack next_level pending_splices lie_var) (
103 getLIE (tc_bracket brack)
104 ) `thenM` \ (meta_ty, lie) ->
105 tcSimplifyBracket lie `thenM_`
107 -- Make the expected type have the right shape
108 zapExpectedTo res_ty meta_ty `thenM_`
110 -- Return the original expression, not the type-decorated one
111 readMutVar pending_splices `thenM` \ pendings ->
112 returnM (noLoc (HsBracketOut brack pendings))
115 tc_bracket :: HsBracket Name -> TcM TcType
117 = tcMetaTy nameTyConName
118 -- Result type is Var (not Q-monadic)
120 tc_bracket (ExpBr expr)
121 = newTyVarTy liftedTypeKind `thenM` \ any_ty ->
122 tcCheckRho expr any_ty `thenM_`
123 tcMetaTy expQTyConName
124 -- Result type is Expr (= Q Exp)
126 tc_bracket (TypBr typ)
127 = tcHsSigType ExprSigCtxt typ `thenM_`
128 tcMetaTy typeQTyConName
129 -- Result type is Type (= Q Typ)
131 tc_bracket (DecBr decls)
132 = tcTopSrcDecls decls `thenM_`
133 -- Typecheck the declarations, dicarding the result
134 -- We'll get all that stuff later, when we splice it in
136 tcMetaTy decTyConName `thenM` \ decl_ty ->
137 tcMetaTy qTyConName `thenM` \ q_ty ->
138 returnM (mkAppTy q_ty (mkListTy decl_ty))
139 -- Result type is Q [Dec]
143 %************************************************************************
145 \subsection{Splicing an expression}
147 %************************************************************************
150 tcSpliceExpr (HsSplice name expr) res_ty
151 = addSrcSpan (getLoc expr) $
152 getStage `thenM` \ level ->
153 case spliceOK level of {
154 Nothing -> failWithTc (illegalSplice level) ;
158 Comp -> do { e <- tcTopSplice expr res_ty ;
160 Brack _ ps_var lie_var ->
162 -- A splice inside brackets
163 -- NB: ignore res_ty, apart from zapping it to a mono-type
164 -- e.g. [| reverse $(h 4) |]
165 -- Here (h 4) :: Q Exp
166 -- but $(h 4) :: forall a.a i.e. anything!
168 zapExpectedType res_ty liftedTypeKind `thenM_`
169 tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
170 setStage (Splice next_level) (
172 tcCheckRho expr meta_exp_ty
175 -- Write the pending splice into the bucket
176 readMutVar ps_var `thenM` \ ps ->
177 writeMutVar ps_var ((name,expr') : ps) `thenM_`
179 returnM (panic "tcSpliceExpr") -- The returned expression is ignored
182 -- tcTopSplice used to have this:
183 -- Note that we do not decrement the level (to -1) before
184 -- typechecking the expression. For example:
185 -- f x = $( ...$(g 3) ... )
186 -- The recursive call to tcMonoExpr will simply expand the
187 -- inner escape before dealing with the outer one
189 tcTopSplice :: LHsExpr Name -> Expected TcType -> TcM (LHsExpr Id)
190 tcTopSplice expr res_ty
191 = tcMetaTy expQTyConName `thenM` \ meta_exp_ty ->
193 -- Typecheck the expression
194 tcTopSpliceExpr expr meta_exp_ty `thenM` \ zonked_q_expr ->
196 -- Run the expression
197 traceTc (text "About to run" <+> ppr zonked_q_expr) `thenM_`
198 runMetaE zonked_q_expr `thenM` \ simple_expr ->
201 -- simple_expr :: TH.Exp
203 expr2 :: LHsExpr RdrName
204 expr2 = convertToHsExpr simple_expr
206 traceTc (text "Got result" <+> ppr expr2) `thenM_`
208 showSplice "expression"
209 zonked_q_expr (ppr expr2) `thenM_`
211 -- Rename it, but bale out if there are errors
212 -- otherwise the type checker just gives more spurious errors
213 checkNoErrs (rnLExpr expr2) `thenM` \ (exp3, fvs) ->
215 tcMonoExpr exp3 res_ty
218 tcTopSpliceExpr :: LHsExpr Name -> TcType -> TcM (LHsExpr Id)
219 -- Type check an expression that is the body of a top-level splice
220 -- (the caller will compile and run it)
221 tcTopSpliceExpr expr meta_ty
222 = checkNoErrs $ -- checkNoErrs: must not try to run the thing
223 -- if the type checker fails!
225 setStage topSpliceStage $
227 -- Typecheck the expression
228 getLIE (tcCheckRho expr meta_ty) `thenM` \ (expr', lie) ->
230 -- Solve the constraints
231 tcSimplifyTop lie `thenM` \ const_binds ->
234 zonkTopLExpr (mkHsLet const_binds expr')
238 %************************************************************************
242 %************************************************************************
244 Very like splicing an expression, but we don't yet share code.
247 kcSpliceType (HsSplice name hs_expr)
248 = addSrcSpan (getLoc hs_expr) $ do
250 ; case spliceOK level of {
251 Nothing -> failWithTc (illegalSplice level) ;
252 Just next_level -> do
255 Comp -> do { (t,k) <- kcTopSpliceType hs_expr
256 ; return (unLoc t, k) } ;
257 Brack _ ps_var lie_var -> do
259 { -- A splice inside brackets
260 ; meta_ty <- tcMetaTy typeQTyConName
261 ; expr' <- setStage (Splice next_level) $
263 tcCheckRho hs_expr meta_ty
265 -- Write the pending splice into the bucket
266 ; ps <- readMutVar ps_var
267 ; writeMutVar ps_var ((name,expr') : ps)
269 -- e.g. [| Int -> $(h 4) |]
270 -- Here (h 4) :: Q Type
271 -- but $(h 4) :: forall a.a i.e. any kind
273 ; returnM (panic "kcSpliceType", kind) -- The returned type is ignored
276 kcTopSpliceType :: LHsExpr Name -> TcM (LHsType Name, TcKind)
278 = do { meta_ty <- tcMetaTy typeQTyConName
280 -- Typecheck the expression
281 ; zonked_q_expr <- tcTopSpliceExpr expr meta_ty
283 -- Run the expression
284 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
285 ; simple_ty <- runMetaT zonked_q_expr
287 ; let -- simple_ty :: TH.Type
288 hs_ty2 :: LHsType RdrName
289 hs_ty2 = convertToHsType simple_ty
291 ; traceTc (text "Got result" <+> ppr hs_ty2)
293 ; showSplice "type" zonked_q_expr (ppr hs_ty2)
295 -- Rename it, but bale out if there are errors
296 -- otherwise the type checker just gives more spurious errors
297 ; let doc = ptext SLIT("In the spliced type") <+> ppr hs_ty2
298 ; hs_ty3 <- checkNoErrs (rnLHsType doc hs_ty2)
303 %************************************************************************
305 \subsection{Splicing an expression}
307 %************************************************************************
310 -- Always at top level
312 = do { meta_dec_ty <- tcMetaTy decTyConName
313 ; meta_q_ty <- tcMetaTy qTyConName
314 ; let list_q = mkAppTy meta_q_ty (mkListTy meta_dec_ty)
315 ; zonked_q_expr <- tcTopSpliceExpr expr list_q
317 -- Run the expression
318 ; traceTc (text "About to run" <+> ppr zonked_q_expr)
319 ; simple_expr <- runMetaD zonked_q_expr
321 -- simple_expr :: [TH.Dec]
322 -- decls :: [RdrNameHsDecl]
323 ; decls <- handleErrors (convertToHsDecls simple_expr)
324 ; traceTc (text "Got result" <+> vcat (map ppr decls))
325 ; showSplice "declarations"
326 zonked_q_expr (vcat (map ppr decls))
329 where handleErrors :: [Either a Message] -> TcM [a]
330 handleErrors [] = return []
331 handleErrors (Left x:xs) = liftM (x:) (handleErrors xs)
332 handleErrors (Right m:xs) = do addErrTc m
337 %************************************************************************
339 \subsection{Running an expression}
341 %************************************************************************
344 runMetaE :: LHsExpr Id -- Of type (Q Exp)
345 -> TcM TH.Exp -- Of type Exp
346 runMetaE e = runMeta e
348 runMetaT :: LHsExpr Id -- Of type (Q Type)
349 -> TcM TH.Type -- Of type Type
350 runMetaT e = runMeta e
352 runMetaD :: LHsExpr Id -- Of type Q [Dec]
353 -> TcM [TH.Dec] -- Of type [Dec]
354 runMetaD e = runMeta e
356 runMeta :: LHsExpr Id -- Of type X
357 -> TcM t -- Of type t
359 = do { hsc_env <- getTopEnv
360 ; tcg_env <- getGblEnv
361 ; this_mod <- getModule
362 ; let type_env = tcg_type_env tcg_env
363 rdr_env = tcg_rdr_env tcg_env
364 -- Wrap the compile-and-run in an exception-catcher
365 -- Compiling might fail if linking fails
366 -- Running might fail if it throws an exception
367 ; either_tval <- tryM $ do
369 hval <- ioToTcRn (HscMain.compileExpr
371 rdr_env type_env expr)
372 -- Coerce it to Q t, and run it
373 ; TH.runQ (unsafeCoerce# hval) }
375 ; case either_tval of
376 Left exn -> failWithTc (vcat [text "Exception when trying to run compile-time code:",
377 nest 4 (vcat [text "Code:" <+> ppr expr,
378 text ("Exn: " ++ Panic.showException exn)])])
379 Right v -> returnM v }
382 To call runQ in the Tc monad, we need to make TcM an instance of Quasi:
385 instance TH.Quasi (IOEnv (Env TcGblEnv TcLclEnv)) where
386 qNewName s = do { u <- newUnique
388 ; return (TH.mkNameU s i) }
390 qReport True msg = addErr (text msg)
391 qReport False msg = addReport (text msg)
393 qCurrentModule = do { m <- getModule; return (moduleUserString m) }
397 qRunIO io = ioToTcRn io
401 %************************************************************************
403 \subsection{Errors and contexts}
405 %************************************************************************
408 showSplice :: String -> LHsExpr Id -> SDoc -> TcM ()
409 showSplice what before after
410 = getSrcSpanM `thenM` \ loc ->
411 traceSplice (vcat [ppr loc <> colon <+> text "Splicing" <+> text what,
412 nest 2 (sep [nest 2 (ppr before),
417 = ptext SLIT("Illegal bracket at level") <+> ppr level
420 = ptext SLIT("Illegal splice at level") <+> ppr level
426 %************************************************************************
430 %************************************************************************
434 reify :: TH.Name -> TcM TH.Info
436 = do { name <- lookupThName th_name
437 ; thing <- tcLookup name
438 -- ToDo: this tcLookup could fail, which would give a
439 -- rather unhelpful error message
443 lookupThName :: TH.Name -> TcM Name
444 lookupThName (TH.Name occ (TH.NameG th_ns mod))
445 = lookupOrig (mkModuleName (TH.modString mod))
446 (OccName.mkOccName ghc_ns (TH.occString occ))
448 ghc_ns = case th_ns of
449 TH.DataName -> dataName
450 TH.TcClsName -> tcClsName
451 TH.VarName -> varName
453 lookupThName th_name@(TH.Name occ TH.NameS)
454 = do { let rdr_name = mkRdrUnqual (OccName.mkOccFS ns occ_fs)
455 ; rdr_env <- getLocalRdrEnv
456 ; case lookupLocalRdrEnv rdr_env rdr_name of
457 Just name -> return name
459 { mb_name <- lookupSrcOcc_maybe rdr_name
461 Just name -> return name ;
462 Nothing -> failWithTc (notInScope th_name)
465 ns | isLexCon occ_fs = OccName.dataName
466 | otherwise = OccName.varName
467 occ_fs = mkFastString (TH.occString occ)
469 lookupThName (TH.Name occ (TH.NameU uniq))
470 = return (mkInternalName (mk_uniq uniq) (OccName.mkOccFS bogus_ns occ_fs) noSrcLoc)
472 occ_fs = mkFastString (TH.occString occ)
473 bogus_ns = OccName.varName -- Not yet recorded in the TH name
474 -- but only the unique matters
476 mk_uniq :: Int# -> Unique
477 mk_uniq u = mkUniqueGrimily (I# u)
479 notInScope :: TH.Name -> SDoc
480 notInScope th_name = quotes (text (show (TH.pprName th_name))) <+>
481 ptext SLIT("is not in scope at a reify")
482 -- Ugh! Rather an indirect way to display the name
484 ------------------------------
485 reifyThing :: TcTyThing -> TcM TH.Info
486 -- The only reason this is monadic is for error reporting,
487 -- which in turn is mainly for the case when TH can't express
488 -- some random GHC extension
490 reifyThing (AGlobal (AnId id))
491 = do { ty <- reifyType (idType id)
492 ; fix <- reifyFixity (idName id)
493 ; let v = reifyName id
494 ; case globalIdDetails id of
495 ClassOpId cls -> return (TH.ClassOpI v ty (reifyName cls) fix)
496 other -> return (TH.VarI v ty Nothing fix)
499 reifyThing (AGlobal (ATyCon tc)) = do { dec <- reifyTyCon tc; return (TH.TyConI dec) }
500 reifyThing (AGlobal (AClass cls)) = do { dec <- reifyClass cls; return (TH.ClassI dec) }
501 reifyThing (AGlobal (ADataCon dc))
502 = do { let name = dataConName dc
503 ; ty <- reifyType (idType (dataConWrapId dc))
504 ; fix <- reifyFixity name
505 ; return (TH.DataConI (reifyName name) ty (reifyName (dataConTyCon dc)) fix) }
507 reifyThing (ATcId id _ _)
508 = do { ty1 <- zonkTcType (idType id) -- Make use of all the info we have, even
509 -- though it may be incomplete
510 ; ty2 <- reifyType ty1
511 ; fix <- reifyFixity (idName id)
512 ; return (TH.VarI (reifyName id) ty2 Nothing fix) }
514 reifyThing (ATyVar tv)
515 = do { ty1 <- zonkTcTyVar tv
516 ; ty2 <- reifyType ty1
517 ; return (TH.TyVarI (reifyName tv) ty2) }
519 ------------------------------
520 reifyTyCon :: TyCon -> TcM TH.Dec
523 = do { let (tvs, rhs) = getSynTyConDefn tc
524 ; rhs' <- reifyType rhs
525 ; return (TH.TySynD (reifyName tc) (reifyTyVars tvs) rhs') }
528 = do { cxt <- reifyCxt (tyConTheta tc)
529 ; con <- reifyDataCon (head (tyConDataCons tc))
530 ; return (TH.NewtypeD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
531 con [{- Don't know about deriving -}]) }
533 | otherwise -- Algebraic
534 = do { cxt <- reifyCxt (tyConTheta tc)
535 ; cons <- mapM reifyDataCon (tyConDataCons tc)
536 ; return (TH.DataD cxt (reifyName tc) (reifyTyVars (tyConTyVars tc))
537 cons [{- Don't know about deriving -}]) }
539 reifyDataCon :: DataCon -> TcM TH.Con
541 = do { arg_tys <- reifyTypes (dataConOrigArgTys dc)
542 ; let stricts = map reifyStrict (dataConStrictMarks dc)
543 fields = dataConFieldLabels dc
544 ; if null fields then
545 return (TH.NormalC (reifyName dc) (stricts `zip` arg_tys))
547 return (TH.RecC (reifyName dc) (zip3 (map reifyName fields) stricts arg_tys)) }
548 -- NB: we don't remember whether the constructor was declared in an infix way
550 ------------------------------
551 reifyClass :: Class -> TcM TH.Dec
553 = do { cxt <- reifyCxt theta
554 ; ops <- mapM reify_op op_stuff
555 ; return (TH.ClassD cxt (reifyName cls) (reifyTyVars tvs) ops) }
557 (tvs, theta, _, op_stuff) = classBigSig cls
558 reify_op (op, _) = do { ty <- reifyType (idType op)
559 ; return (TH.SigD (reifyName op) ty) }
561 ------------------------------
562 reifyType :: TypeRep.Type -> TcM TH.Type
563 reifyType (TyVarTy tv) = return (TH.VarT (reifyName tv))
564 reifyType (TyConApp tc tys) = reify_tc_app (reifyName tc) tys
565 reifyType (NewTcApp tc tys) = reify_tc_app (reifyName tc) tys
566 reifyType (NoteTy _ ty) = reifyType ty
567 reifyType (AppTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (r1 `TH.AppT` r2) }
568 reifyType (FunTy t1 t2) = do { [r1,r2] <- reifyTypes [t1,t2] ; return (TH.ArrowT `TH.AppT` r1 `TH.AppT` r2) }
569 reifyType ty@(ForAllTy _ _) = do { cxt' <- reifyCxt cxt;
570 ; tau' <- reifyType tau
571 ; return (TH.ForallT (reifyTyVars tvs) cxt' tau') }
573 (tvs, cxt, tau) = tcSplitSigmaTy ty
574 reifyTypes = mapM reifyType
575 reifyCxt = mapM reifyPred
577 reifyTyVars :: [TyVar] -> [TH.Name]
578 reifyTyVars = map reifyName
580 reify_tc_app :: TH.Name -> [TypeRep.Type] -> TcM TH.Type
581 reify_tc_app tc tys = do { tys' <- reifyTypes tys
582 ; return (foldl TH.AppT (TH.ConT tc) tys') }
584 reifyPred :: TypeRep.PredType -> TcM TH.Type
585 reifyPred (ClassP cls tys) = reify_tc_app (reifyName cls) tys
586 reifyPred p@(IParam _ _) = noTH SLIT("implicit parameters") (ppr p)
589 ------------------------------
590 reifyName :: NamedThing n => n -> TH.Name
592 | isExternalName name = mk_varg mod occ_str
593 | otherwise = TH.mkNameU occ_str (getKey (getUnique name))
596 mod = moduleUserString (nameModule name)
597 occ_str = occNameUserString occ
598 occ = nameOccName name
599 mk_varg | OccName.isDataOcc occ = TH.mkNameG_d
600 | OccName.isVarOcc occ = TH.mkNameG_v
601 | OccName.isTcOcc occ = TH.mkNameG_tc
602 | otherwise = pprPanic "reifyName" (ppr name)
604 ------------------------------
605 reifyFixity :: Name -> TcM TH.Fixity
607 = do { fix <- lookupFixityRn name
608 ; return (conv_fix fix) }
610 conv_fix (BasicTypes.Fixity i d) = TH.Fixity i (conv_dir d)
611 conv_dir BasicTypes.InfixR = TH.InfixR
612 conv_dir BasicTypes.InfixL = TH.InfixL
613 conv_dir BasicTypes.InfixN = TH.InfixN
615 reifyStrict :: BasicTypes.StrictnessMark -> TH.Strict
616 reifyStrict MarkedStrict = TH.IsStrict
617 reifyStrict MarkedUnboxed = TH.IsStrict
618 reifyStrict NotMarkedStrict = TH.NotStrict
620 ------------------------------
621 noTH :: LitString -> SDoc -> TcM a
622 noTH s d = failWithTc (hsep [ptext SLIT("Can't represent") <+> ptext s <+>
623 ptext SLIT("in Template Haskell:"),