X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcSplice.lhs;h=50bbc3cd1c91095e5ef78ddbeb401ade5b16cb2d;hp=4e2ae695d90888804298f01c41ac285a0529a809;hb=f3399c446c7507d46d6cc550aa2fe7027dbc1b5b;hpb=948af9452927becb494ac967fba813956b74a182 diff --git a/compiler/typecheck/TcSplice.lhs b/compiler/typecheck/TcSplice.lhs index 4e2ae69..50bbc3c 100644 --- a/compiler/typecheck/TcSplice.lhs +++ b/compiler/typecheck/TcSplice.lhs @@ -6,7 +6,15 @@ TcSplice: Template Haskell splices \begin{code} -module TcSplice( tcSpliceExpr, tcSpliceDecls, tcBracket ) where +{-# OPTIONS -w #-} +-- The above warning supression flag is a temporary kludge. +-- While working on this module you are encouraged to remove it and fix +-- any warnings in the module. See +-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings +-- for details + +module TcSplice( tcSpliceExpr, tcSpliceDecls, tcBracket, + runQuasiQuoteExpr, runQuasiQuotePat ) where #include "HsVersions.h" @@ -54,6 +62,7 @@ import Outputable import Unique import DynFlags import PackageConfig +import Maybe import BasicTypes import Panic import FastString @@ -64,8 +73,86 @@ import qualified Language.Haskell.TH.Syntax as TH import GHC.Exts ( unsafeCoerce#, Int#, Int(..) ) import Control.Monad ( liftM ) +import qualified Control.Exception as Exception( userErrors ) \end{code} +Note [Template Haskell levels] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +* Imported things are impLevel (= 0) + +* In GHCi, variables bound by a previous command are treated + as impLevel, because we have bytecode for them. + +* Variables are bound at the "current level" + +* The current level starts off at topLevel (= 1) + +* The level is decremented by splicing $(..) + incremented by brackets [| |] + incremented by name-quoting 'f + +When a variable is used, we compare + bind: binding level, and + use: current level at usage site + + Generally + bind > use Always error (bound later than used) + [| \x -> $(f x) |] + + bind = use Always OK (bound same stage as used) + [| \x -> $(f [| x |]) |] + + bind < use Inside brackets, it depends + Inside splice, OK + Inside neither, OK + + For (bind < use) inside brackets, there are three cases: + - Imported things OK f = [| map |] + - Top-level things OK g = [| f |] + - Non-top-level Only if there is a liftable instance + h = \(x:Int) -> [| x |] + +See Note [What is a top-level Id?] + +Note [Quoting names] +~~~~~~~~~~~~~~~~~~~~ +A quoted name 'n is a bit like a quoted expression [| n |], except that we +have no cross-stage lifting (c.f. TcExpr.thBrackId). So, after incrementing +the use-level to account for the brackets, the cases are: + + bind > use Error + bind = use OK + bind < use + Imported things OK + Top-level things OK + Non-top-level Error + +See Note [What is a top-level Id?] in TcEnv. Examples: + + f 'map -- OK; also for top-level defns of this module + + \x. f 'x -- Not ok (whereas \x. f [| x |] might have been ok, by + -- cross-stage lifting + + \y. [| \x. $(f 'y) |] -- Not ok (same reason) + + [| \x. $(f 'x) |] -- OK + + +Note [What is a top-level Id?] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In the level-control criteria above, we need to know what a "top level Id" is. +There are three kinds: + * Imported from another module (GlobalId, ExternalName) + * Bound at the top level of this module (ExternalName) + * In GHCi, bound by a previous stmt (GlobalId) +It's strange that there is no one criterion tht picks out all three, but that's +how it is right now. (The obvious thing is to give an ExternalName to GHCi Ids +bound in an earlier Stmt, but what module would you choose? See +Note [Interactively-bound Ids in GHCi] in TcRnDriver.) + +The predicate we use is TcEnv.thTopLevelId. + %************************************************************************ %* * @@ -79,9 +166,15 @@ tcSpliceExpr :: HsSplice Name -> BoxyRhoType -> TcM (HsExpr TcId) kcSpliceType :: HsSplice Name -> TcM (HsType Name, TcKind) -- None of these functions add constraints to the LIE +runQuasiQuoteExpr :: HsQuasiQuote Name -> TcM (LHsExpr RdrName) +runQuasiQuotePat :: HsQuasiQuote Name -> TcM (LPat RdrName) + #ifndef GHCI tcSpliceExpr n e ty = pprPanic "Cant do tcSpliceExpr without GHCi" (ppr e) tcSpliceDecls e = pprPanic "Cant do tcSpliceDecls without GHCi" (ppr e) + +runQuasiQuoteExpr q = pprPanic "Cant do runQuasiQuoteExpr without GHCi" (ppr q) +runQuasiQuotePat q = pprPanic "Cant do runQuasiQuotePat without GHCi" (ppr q) #else \end{code} @@ -119,7 +212,7 @@ tcBracket brack res_ty getLIEVar `thenM` \ lie_var -> setStage (Brack next_level pending_splices lie_var) ( - getLIE (tc_bracket brack) + getLIE (tc_bracket next_level brack) ) `thenM` \ (meta_ty, lie) -> tcSimplifyBracket lie `thenM_` @@ -131,22 +224,34 @@ tcBracket brack res_ty returnM (noLoc (HsBracketOut brack pendings)) } -tc_bracket :: HsBracket Name -> TcM TcType -tc_bracket (VarBr v) - = tcMetaTy nameTyConName -- Result type is Var (not Q-monadic) +tc_bracket :: ThLevel -> HsBracket Name -> TcM TcType +tc_bracket use_lvl (VarBr name) -- Note [Quoting names] + = do { thing <- tcLookup name + ; case thing of + AGlobal _ -> return () + ATcId { tct_level = bind_lvl, tct_id = id } + | thTopLevelId id -- C.f thTopLevelId case of + -> keepAliveTc id -- TcExpr.thBrackId + | otherwise + -> do { checkTc (use_lvl == bind_lvl) + (quotedNameStageErr name) } + other -> pprPanic "th_bracket" (ppr name) + + ; tcMetaTy nameTyConName -- Result type is Var (not Q-monadic) + } -tc_bracket (ExpBr expr) - = newFlexiTyVarTy liftedTypeKind `thenM` \ any_ty -> - tcMonoExpr expr any_ty `thenM_` - tcMetaTy expQTyConName +tc_bracket use_lvl (ExpBr expr) + = do { any_ty <- newFlexiTyVarTy liftedTypeKind + ; tcMonoExpr expr any_ty + ; tcMetaTy expQTyConName } -- Result type is Expr (= Q Exp) -tc_bracket (TypBr typ) - = tcHsSigType ExprSigCtxt typ `thenM_` - tcMetaTy typeQTyConName +tc_bracket use_lvl (TypBr typ) + = do { tcHsSigType ExprSigCtxt typ + ; tcMetaTy typeQTyConName } -- Result type is Type (= Q Typ) -tc_bracket (DecBr decls) +tc_bracket use_lvl (DecBr decls) = do { tcTopSrcDecls emptyModDetails decls -- Typecheck the declarations, dicarding the result -- We'll get all that stuff later, when we splice it in @@ -157,8 +262,12 @@ tc_bracket (DecBr decls) -- Result type is Q [Dec] } -tc_bracket (PatBr _) +tc_bracket use_lvl (PatBr _) = failWithTc (ptext SLIT("Tempate Haskell pattern brackets are not supported yet")) + +quotedNameStageErr v + = sep [ ptext SLIT("Stage error: the non-top-level quoted name") <+> ppr (VarBr v) + , ptext SLIT("must be used at the same stage at which is is bound")] \end{code} @@ -256,6 +365,80 @@ tcTopSpliceExpr expr meta_ty %************************************************************************ %* * + Quasi-quoting +%* * +%************************************************************************ + +Note [Quasi-quote overview] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The GHC "quasi-quote" extension is described by Geoff Mainland's paper +"Why it's nice to be quoted: quasiquoting for Haskell" (Haskell +Workshop 2007). + +Briefly, one writes + [:p| stuff |] +and the arbitrary string "stuff" gets parsed by the parser 'p', whose +type should be Language.Haskell.TH.Quote.QuasiQuoter. 'p' must be +defined in another module, because we are going to run it here. It's +a bit like a TH splice: + $(p "stuff") + +However, you can do this in patterns as well as terms. Becuase of this, +the splice is run by the *renamer* rather than the type checker. + +\begin{code} +runQuasiQuote :: Outputable hs_syn + => HsQuasiQuote Name -- Contains term of type QuasiQuoter, and the String + -> Name -- Of type QuasiQuoter -> String -> Q th_syn + -> String -- Documentation string only + -> Name -- Name of th_syn type + -> (SrcSpan -> th_syn -> Either Message hs_syn) + -> TcM hs_syn +runQuasiQuote (HsQuasiQuote name quoter q_span quote) quote_selector desc meta_ty convert + = do { -- Check that the quoter is not locally defined, otherwise the TH + -- machinery will not be able to run the quasiquote. + ; this_mod <- getModule + ; let is_local = case nameModule_maybe quoter of + Just mod | mod == this_mod -> True + | otherwise -> False + Nothing -> True + ; traceTc (text "runQQ" <+> ppr quoter <+> ppr is_local) + ; checkTc (not is_local) (quoteStageError quoter) + + -- Build the expression + ; let quoterExpr = L q_span $! HsVar $! quoter + ; let quoteExpr = L q_span $! HsLit $! HsString quote + ; let expr = L q_span $ + HsApp (L q_span $ + HsApp (L q_span (HsVar quote_selector)) quoterExpr) quoteExpr + ; recordThUse + ; meta_exp_ty <- tcMetaTy meta_ty + + -- Typecheck the expression + ; zonked_q_expr <- tcTopSpliceExpr expr meta_exp_ty + + -- Run the expression + ; traceTc (text "About to run" <+> ppr zonked_q_expr) + ; result <- runMeta convert zonked_q_expr + ; traceTc (text "Got result" <+> ppr result) + ; showSplice desc zonked_q_expr (ppr result) + ; return result + } + +runQuasiQuoteExpr quasiquote + = runQuasiQuote quasiquote quoteExpName "expression" expQTyConName convertToHsExpr + +runQuasiQuotePat quasiquote + = runQuasiQuote quasiquote quotePatName "pattern" patQTyConName convertToPat + +quoteStageError quoter + = sep [ptext SLIT("GHC stage restriction:") <+> ppr quoter, + nest 2 (ptext SLIT("is used in a quasiquote, and must be imported, not defined locally"))] +\end{code} + + +%************************************************************************ +%* * Splicing a type %* * %************************************************************************ @@ -361,6 +544,11 @@ runMetaE :: (SrcSpan -> TH.Exp -> Either Message (LHsExpr RdrName)) -> TcM (LHsExpr RdrName) runMetaE = runMeta +runMetaP :: (SrcSpan -> TH.Pat -> Either Message (Pat RdrName)) + -> LHsExpr Id -- Of type (Q Pat) + -> TcM (Pat RdrName) +runMetaP = runMeta + runMetaT :: (SrcSpan -> TH.Type -> Either Message (LHsType RdrName)) -> LHsExpr Id -- Of type (Q Type) -> TcM (LHsType RdrName) @@ -376,11 +564,7 @@ runMeta :: (SrcSpan -> th_syn -> Either Message hs_syn) -> TcM hs_syn -- Of type t runMeta convert expr = do { -- Desugar -#if defined(GHCI) && defined(DEBUGGER) - ds_expr <- unsetOptM Opt_Debugging $ initDsTc (dsLExpr expr) -#else ds_expr <- initDsTc (dsLExpr expr) -#endif -- Compile and link it; might fail if linking fails ; hsc_env <- getTopEnv ; src_span <- getSrcSpanM @@ -391,6 +575,7 @@ runMeta convert expr Right hval -> do { -- Coerce it to Q t, and run it + -- Running might fail if it throws an exception of any kind (hence tryAllM) -- including, say, a pattern-match exception in the code we are running -- @@ -398,23 +583,61 @@ runMeta convert expr -- exception-cacthing thing so that if there are any lurking -- exceptions in the data structure returned by hval, we'll -- encounter them inside the try - either_tval <- tryAllM $ do - { th_syn <- TH.runQ (unsafeCoerce# hval) - ; case convert (getLoc expr) th_syn of - Left err -> do { addErrTc err; return Nothing } - Right hs_syn -> return (Just hs_syn) } + -- + -- See Note [Exceptions in TH] + let expr_span = getLoc expr + ; either_tval <- tryAllM $ + setSrcSpan expr_span $ -- Set the span so that qLocation can + -- see where this splice is + do { th_syn <- TH.runQ (unsafeCoerce# hval) + ; case convert expr_span th_syn of + Left err -> failWithTc err + Right hs_syn -> return hs_syn } ; case either_tval of - Right (Just v) -> return v - Right Nothing -> failM -- Error already in Tc monad - Left exn -> failWithTc (mk_msg "run" exn) -- Exception - }}} + Right v -> return v + Left exn | Just s <- Exception.userErrors exn + , s == "IOEnv failure" + -> failM -- Error already in Tc monad + | otherwise -> failWithTc (mk_msg "run" exn) -- Exception + }}} where mk_msg s exn = vcat [text "Exception when trying to" <+> text s <+> text "compile-time code:", nest 2 (text (Panic.showException exn)), nest 2 (text "Code:" <+> ppr expr)] \end{code} +Note [Exceptions in TH] +~~~~~~~~~~~~~~~~~~~~~~~ +Supppose we have something like this + $( f 4 ) +where + f :: Int -> Q [Dec] + f n | n>3 = fail "Too many declarations" + | otherwise = ... + +The 'fail' is a user-generated failure, and should be displayed as a +perfectly ordinary compiler error message, not a panic or anything +like that. Here's how it's processed: + + * 'fail' is the monad fail. The monad instance for Q in TH.Syntax + effectively transforms (fail s) to + qReport True s >> fail + where 'qReport' comes from the Quasi class and fail from its monad + superclass. + + * The TcM monad is an instance of Quasi (see TcSplice), and it implements + (qReport True s) by using addErr to add an error message to the bag of errors. + The 'fail' in TcM raises a UserError, with the uninteresting string + "IOEnv failure" + + * So, when running a splice, we catch all exceptions; then for + - a UserError "IOEnv failure", we assume the error is already + in the error-bag (above) + - other errors, we add an error to the bag + and then fail + + To call runQ in the Tc monad, we need to make TcM an instance of Quasi: \begin{code} @@ -426,10 +649,14 @@ instance TH.Quasi (IOEnv (Env TcGblEnv TcLclEnv)) where qReport True msg = addErr (text msg) qReport False msg = addReport (text msg) - qCurrentModule = do { m <- getModule; - return (moduleNameString (moduleName m)) } - -- ToDo: is throwing away the package name ok here? - + qLocation = do { m <- getModule + ; l <- getSrcSpanM + ; return (TH.Loc { TH.loc_filename = unpackFS (srcSpanFile l) + , TH.loc_module = moduleNameString (moduleName m) + , TH.loc_package = packageIdString (modulePackageId m) + , TH.loc_start = (srcSpanStartLine l, srcSpanStartCol l) + , TH.loc_end = (srcSpanEndLine l, srcSpanEndCol l) }) } + qReify v = reify v -- For qRecover, discard error messages if @@ -505,8 +732,7 @@ lookupThName th_name@(TH.Name occ flavour) Nothing | not (isSrcRdrName rdr_name) -- Exact, Orig -> lookupImportedName rdr_name | otherwise -- Unqual, Qual - -> do { - mb_name <- lookupSrcOcc_maybe rdr_name + -> do { mb_name <- lookupSrcOcc_maybe rdr_name ; case mb_name of Just name -> return name Nothing -> failWithTc (notInScope th_name) }