2 % (c) The University of Glasgow 2006
7 TyThing(..), TcTyThing(..), TcId,
9 -- Instance environment, and InstInfo type
10 InstInfo(..), iDFunId, pprInstInfo, pprInstInfoDetails,
11 simpleInstInfoClsTy, simpleInstInfoTy, simpleInstInfoTyCon,
17 tcLookupLocatedGlobal, tcLookupGlobal,
18 tcLookupField, tcLookupTyCon, tcLookupClass, tcLookupDataCon,
19 tcLookupLocatedGlobalId, tcLookupLocatedTyCon,
20 tcLookupLocatedClass, tcLookupFamInst,
23 tcExtendKindEnv, tcExtendKindEnvTvs,
24 tcExtendTyVarEnv, tcExtendTyVarEnv2,
25 tcExtendIdEnv, tcExtendIdEnv1, tcExtendIdEnv2,
26 tcLookup, tcLookupLocated, tcLookupLocalIds,
27 tcLookupId, tcLookupTyVar, getScopedTyVarBinds,
28 lclEnvElts, getInLocalScope, findGlobals,
29 wrongThingErr, pprBinders,
32 tcExtendRecEnv, -- For knot-tying
37 -- Global type variables
40 -- Template Haskell stuff
41 checkWellStaged, spliceOK, bracketOK, tcMetaTy, thLevel,
45 newLocalName, newDFunName, newFamInstTyConName
48 #include "HsVersions.h"
78 %************************************************************************
82 %************************************************************************
84 Using the Located versions (eg. tcLookupLocatedGlobal) is preferred,
85 unless you know that the SrcSpan in the monad is already set to the
89 tcLookupLocatedGlobal :: Located Name -> TcM TyThing
90 -- c.f. IfaceEnvEnv.tcIfaceGlobal
91 tcLookupLocatedGlobal name
92 = addLocM tcLookupGlobal name
94 tcLookupGlobal :: Name -> TcM TyThing
95 -- The Name is almost always an ExternalName, but not always
96 -- In GHCi, we may make command-line bindings (ghci> let x = True)
97 -- that bind a GlobalId, but with an InternalName
99 = do { env <- getGblEnv
102 ; case lookupNameEnv (tcg_type_env env) name of {
103 Just thing -> return thing ;
107 { (eps,hpt) <- getEpsAndHpt
109 ; case lookupType dflags hpt (eps_PTE eps) name of {
110 Just thing -> return thing ;
113 -- Should it have been in the local envt?
114 { case nameModule_maybe name of
115 Nothing -> notFound name -- Internal names can happen in GHCi
117 Just mod | mod == tcg_mod env -- Names from this module
118 -> notFound name -- should be in tcg_type_env
119 | mod == thFAKE -- Names bound in TH declaration brackets
120 -> notFound name -- should be in tcg_env
122 -> tcImportDecl name -- Go find it in an interface
125 tcLookupField :: Name -> TcM Id -- Returns the selector Id
127 = tcLookupGlobal name `thenM` \ thing ->
130 other -> wrongThingErr "field name" (AGlobal thing) name
132 tcLookupDataCon :: Name -> TcM DataCon
134 = tcLookupGlobal name `thenM` \ thing ->
136 ADataCon con -> return con
137 other -> wrongThingErr "data constructor" (AGlobal thing) name
139 tcLookupClass :: Name -> TcM Class
141 = tcLookupGlobal name `thenM` \ thing ->
143 AClass cls -> return cls
144 other -> wrongThingErr "class" (AGlobal thing) name
146 tcLookupTyCon :: Name -> TcM TyCon
148 = tcLookupGlobal name `thenM` \ thing ->
150 ATyCon tc -> return tc
151 other -> wrongThingErr "type constructor" (AGlobal thing) name
153 tcLookupLocatedGlobalId :: Located Name -> TcM Id
154 tcLookupLocatedGlobalId = addLocM tcLookupId
156 tcLookupLocatedClass :: Located Name -> TcM Class
157 tcLookupLocatedClass = addLocM tcLookupClass
159 tcLookupLocatedTyCon :: Located Name -> TcM TyCon
160 tcLookupLocatedTyCon = addLocM tcLookupTyCon
162 -- Look up the representation tycon of a family instance.
163 -- Return the rep tycon and the corresponding rep args
164 tcLookupFamInst :: TyCon -> [Type] -> TcM (TyCon, [Type])
165 tcLookupFamInst tycon tys
166 | not (isOpenTyCon tycon)
167 = return (tycon, tys)
169 = do { env <- getGblEnv
171 ; let instEnv = (eps_fam_inst_env eps, tcg_fam_inst_env env)
172 ; case lookupFamInstEnv instEnv tycon tys of
173 [(subst,fam_inst)] -> return (rep_tc, substTyVars subst (tyConTyVars rep_tc))
174 where -- NB: assumption is that (tyConTyVars rep_tc) is in
175 -- the domain of the substitution
176 rep_tc = famInstTyCon fam_inst
178 other -> famInstNotFound tycon tys other
182 %************************************************************************
184 Extending the global environment
186 %************************************************************************
190 tcExtendGlobalEnv :: [TyThing] -> TcM r -> TcM r
191 -- Given a mixture of Ids, TyCons, Classes, all from the
192 -- module being compiled, extend the global environment
193 tcExtendGlobalEnv things thing_inside
194 = do { env <- getGblEnv
195 ; let ge' = extendTypeEnvList (tcg_type_env env) things
196 ; setGblEnv (env {tcg_type_env = ge'}) thing_inside }
198 tcExtendGlobalValEnv :: [Id] -> TcM a -> TcM a
199 -- Same deal as tcExtendGlobalEnv, but for Ids
200 tcExtendGlobalValEnv ids thing_inside
201 = tcExtendGlobalEnv [AnId id | id <- ids] thing_inside
205 tcExtendRecEnv :: [(Name,TyThing)] -> TcM r -> TcM r
206 -- Extend the global environments for the type/class knot tying game
207 tcExtendRecEnv gbl_stuff thing_inside
208 = updGblEnv upd thing_inside
210 upd env = env { tcg_type_env = extend (tcg_type_env env) }
211 extend env = extendNameEnvList env gbl_stuff
215 %************************************************************************
217 \subsection{The local environment}
219 %************************************************************************
222 tcLookupLocated :: Located Name -> TcM TcTyThing
223 tcLookupLocated = addLocM tcLookup
225 tcLookup :: Name -> TcM TcTyThing
227 = getLclEnv `thenM` \ local_env ->
228 case lookupNameEnv (tcl_env local_env) name of
229 Just thing -> returnM thing
230 Nothing -> tcLookupGlobal name `thenM` \ thing ->
231 returnM (AGlobal thing)
233 tcLookupTyVar :: Name -> TcM TcTyVar
235 = tcLookup name `thenM` \ thing ->
237 ATyVar _ ty -> return (tcGetTyVar "tcLookupTyVar" ty)
238 other -> pprPanic "tcLookupTyVar" (ppr name)
240 tcLookupId :: Name -> TcM Id
241 -- Used when we aren't interested in the binding level, nor refinement.
242 -- The "no refinement" part means that we return the un-refined Id regardless
244 -- The Id is never a DataCon. (Why does that matter? see TcExpr.tcId)
246 = tcLookup name `thenM` \ thing ->
248 ATcId { tct_id = id} -> returnM id
249 AGlobal (AnId id) -> returnM id
250 other -> pprPanic "tcLookupId" (ppr name)
252 tcLookupLocalIds :: [Name] -> TcM [TcId]
253 -- We expect the variables to all be bound, and all at
254 -- the same level as the lookup. Only used in one place...
256 = getLclEnv `thenM` \ env ->
257 returnM (map (lookup (tcl_env env) (thLevel (tcl_th_ctxt env))) ns)
260 = case lookupNameEnv lenv name of
261 Just (ATcId { tct_id = id, tct_level = lvl1 })
262 -> ASSERT( lvl == lvl1 ) id
263 other -> pprPanic "tcLookupLocalIds" (ppr name)
265 lclEnvElts :: TcLclEnv -> [TcTyThing]
266 lclEnvElts env = nameEnvElts (tcl_env env)
268 getInLocalScope :: TcM (Name -> Bool)
270 getInLocalScope = getLclEnv `thenM` \ env ->
272 lcl_env = tcl_env env
274 return (`elemNameEnv` lcl_env)
278 tcExtendKindEnv :: [(Name, TcKind)] -> TcM r -> TcM r
279 tcExtendKindEnv things thing_inside
280 = updLclEnv upd thing_inside
282 upd lcl_env = lcl_env { tcl_env = extend (tcl_env lcl_env) }
283 extend env = extendNameEnvList env [(n, AThing k) | (n,k) <- things]
285 tcExtendKindEnvTvs :: [LHsTyVarBndr Name] -> TcM r -> TcM r
286 tcExtendKindEnvTvs bndrs thing_inside
287 = updLclEnv upd thing_inside
289 upd lcl_env = lcl_env { tcl_env = extend (tcl_env lcl_env) }
290 extend env = extendNameEnvList env pairs
291 pairs = [(n, AThing k) | L _ (KindedTyVar n k) <- bndrs]
293 tcExtendTyVarEnv :: [TyVar] -> TcM r -> TcM r
294 tcExtendTyVarEnv tvs thing_inside
295 = tcExtendTyVarEnv2 [(tyVarName tv, mkTyVarTy tv) | tv <- tvs] thing_inside
297 tcExtendTyVarEnv2 :: [(Name,TcType)] -> TcM r -> TcM r
298 tcExtendTyVarEnv2 binds thing_inside
299 = getLclEnv `thenM` \ env@(TcLclEnv {tcl_env = le,
301 tcl_rdr = rdr_env}) ->
303 rdr_env' = extendLocalRdrEnv rdr_env (map fst binds)
304 new_tv_set = tcTyVarsOfTypes (map snd binds)
305 le' = extendNameEnvList le [(name, ATyVar name ty) | (name, ty) <- binds]
307 -- It's important to add the in-scope tyvars to the global tyvar set
309 -- f (_::r) = let g y = y::r in ...
310 -- Here, g mustn't be generalised. This is also important during
311 -- class and instance decls, when we mustn't generalise the class tyvars
312 -- when typechecking the methods.
313 tc_extend_gtvs gtvs new_tv_set `thenM` \ gtvs' ->
314 setLclEnv (env {tcl_env = le', tcl_tyvars = gtvs', tcl_rdr = rdr_env'}) thing_inside
316 getScopedTyVarBinds :: TcM [(Name, TcType)]
318 = do { lcl_env <- getLclEnv
319 ; return [(name, ty) | ATyVar name ty <- nameEnvElts (tcl_env lcl_env)] }
324 tcExtendIdEnv :: [TcId] -> TcM a -> TcM a
325 -- Invariant: the TcIds are fully zonked. Reasons:
326 -- (a) The kinds of the forall'd type variables are defaulted
327 -- (see Kind.defaultKind, done in zonkQuantifiedTyVar)
328 -- (b) There are no via-Indirect occurrences of the bound variables
329 -- in the types, because instantiation does not look through such things
330 -- (c) The call to tyVarsOfTypes is ok without looking through refs
331 tcExtendIdEnv ids thing_inside = tcExtendIdEnv2 [(idName id, id) | id <- ids] thing_inside
333 tcExtendIdEnv1 :: Name -> TcId -> TcM a -> TcM a
334 tcExtendIdEnv1 name id thing_inside = tcExtendIdEnv2 [(name,id)] thing_inside
336 tcExtendIdEnv2 :: [(Name,TcId)] -> TcM a -> TcM a
337 -- Invariant: the TcIds are fully zonked (see tcExtendIdEnv above)
338 tcExtendIdEnv2 names_w_ids thing_inside
339 = getLclEnv `thenM` \ env ->
341 extra_global_tyvars = tcTyVarsOfTypes [idType id | (_,id) <- names_w_ids]
342 th_lvl = thLevel (tcl_th_ctxt env)
343 extra_env = [ (name, ATcId { tct_id = id,
346 tct_co = if isRefineableTy id_ty
347 then Just idHsWrapper
349 | (name,id) <- names_w_ids, let id_ty = idType id]
350 le' = extendNameEnvList (tcl_env env) extra_env
351 rdr_env' = extendLocalRdrEnv (tcl_rdr env) [name | (name,_) <- names_w_ids]
353 traceTc (text "env2") `thenM_`
354 traceTc (text "env3" <+> ppr extra_env) `thenM_`
355 tc_extend_gtvs (tcl_tyvars env) extra_global_tyvars `thenM` \ gtvs' ->
356 (traceTc (text "env4") `thenM_`
357 setLclEnv (env {tcl_env = le', tcl_tyvars = gtvs', tcl_rdr = rdr_env'}) thing_inside)
362 -----------------------
363 -- findGlobals looks at the value environment and finds values
364 -- whose types mention the offending type variable. It has to be
365 -- careful to zonk the Id's type first, so it has to be in the monad.
366 -- We must be careful to pass it a zonked type variable, too.
368 findGlobals :: TcTyVarSet
370 -> TcM (TidyEnv, [SDoc])
372 findGlobals tvs tidy_env
373 = getLclEnv `thenM` \ lcl_env ->
374 go tidy_env [] (lclEnvElts lcl_env)
376 go tidy_env acc [] = returnM (tidy_env, acc)
377 go tidy_env acc (thing : things)
378 = find_thing ignore_it tidy_env thing `thenM` \ (tidy_env1, maybe_doc) ->
380 Just d -> go tidy_env1 (d:acc) things
381 Nothing -> go tidy_env1 acc things
383 ignore_it ty = tvs `disjointVarSet` tyVarsOfType ty
385 -----------------------
386 find_thing ignore_it tidy_env (ATcId { tct_id = id })
387 = zonkTcType (idType id) `thenM` \ id_ty ->
388 if ignore_it id_ty then
389 returnM (tidy_env, Nothing)
391 (tidy_env', tidy_ty) = tidyOpenType tidy_env id_ty
392 msg = sep [ppr id <+> dcolon <+> ppr tidy_ty,
393 nest 2 (parens (ptext SLIT("bound at") <+>
394 ppr (getSrcLoc id)))]
396 returnM (tidy_env', Just msg)
398 find_thing ignore_it tidy_env (ATyVar tv ty)
399 = zonkTcType ty `thenM` \ tv_ty ->
400 if ignore_it tv_ty then
401 returnM (tidy_env, Nothing)
403 -- The name tv is scoped, so we don't need to tidy it
404 (tidy_env1, tidy_ty) = tidyOpenType tidy_env tv_ty
405 msg = sep [ptext SLIT("Scoped type variable") <+> quotes (ppr tv) <+> eq_stuff, nest 2 bound_at]
407 eq_stuff | Just tv' <- Type.getTyVar_maybe tv_ty,
408 getOccName tv == getOccName tv' = empty
409 | otherwise = equals <+> ppr tidy_ty
410 -- It's ok to use Type.getTyVar_maybe because ty is zonked by now
411 bound_at = parens $ ptext SLIT("bound at:") <+> ppr (getSrcLoc tv)
413 returnM (tidy_env1, Just msg)
415 find_thing _ _ thing = pprPanic "find_thing" (ppr thing)
419 refineEnvironment :: Refinement -> TcM a -> TcM a
420 -- I don't think I have to refine the set of global type variables in scope
421 -- Reason: the refinement never increases that set
422 refineEnvironment reft thing_inside
423 | isEmptyRefinement reft -- Common case
426 = do { env <- getLclEnv
427 ; let le' = mapNameEnv refine (tcl_env env)
428 ; setLclEnv (env {tcl_env = le'}) thing_inside }
430 refine elt@(ATcId { tct_co = Just co, tct_type = ty })
431 | Just (co', ty') <- refineType reft ty
432 = elt { tct_co = Just (WpCo co' <.> co), tct_type = ty' }
433 refine (ATyVar tv ty)
434 | Just (_, ty') <- refineType reft ty
435 = ATyVar tv ty' -- Ignore the coercion that refineType returns
437 refine elt = elt -- Common case
440 %************************************************************************
442 \subsection{The global tyvars}
444 %************************************************************************
447 tc_extend_gtvs gtvs extra_global_tvs
448 = readMutVar gtvs `thenM` \ global_tvs ->
449 newMutVar (global_tvs `unionVarSet` extra_global_tvs)
452 @tcGetGlobalTyVars@ returns a fully-zonked set of tyvars free in the environment.
453 To improve subsequent calls to the same function it writes the zonked set back into
457 tcGetGlobalTyVars :: TcM TcTyVarSet
459 = getLclEnv `thenM` \ (TcLclEnv {tcl_tyvars = gtv_var}) ->
460 readMutVar gtv_var `thenM` \ gbl_tvs ->
461 zonkTcTyVarsAndFV (varSetElems gbl_tvs) `thenM` \ gbl_tvs' ->
462 writeMutVar gtv_var gbl_tvs' `thenM_`
467 %************************************************************************
471 %************************************************************************
474 tcExtendRules :: [LRuleDecl Id] -> TcM a -> TcM a
475 -- Just pop the new rules into the EPS and envt resp
476 -- All the rules come from an interface file, not soruce
477 -- Nevertheless, some may be for this module, if we read
478 -- its interface instead of its source code
479 tcExtendRules lcl_rules thing_inside
480 = do { env <- getGblEnv
482 env' = env { tcg_rules = lcl_rules ++ tcg_rules env }
483 ; setGblEnv env' thing_inside }
487 %************************************************************************
491 %************************************************************************
494 instance Outputable ThStage where
495 ppr Comp = text "Comp"
496 ppr (Brack l _ _) = text "Brack" <+> int l
497 ppr (Splice l) = text "Splice" <+> int l
500 thLevel :: ThStage -> ThLevel
501 thLevel Comp = topLevel
502 thLevel (Splice l) = l
503 thLevel (Brack l _ _) = l
506 checkWellStaged :: SDoc -- What the stage check is for
507 -> ThLevel -- Binding level
508 -> ThStage -- Use stage
509 -> TcM () -- Fail if badly staged, adding an error
510 checkWellStaged pp_thing bind_lvl use_stage
511 | bind_lvl <= use_lvl -- OK!
514 | bind_lvl == topLevel -- GHC restriction on top level splices
516 sep [ptext SLIT("GHC stage restriction:") <+> pp_thing,
517 nest 2 (ptext SLIT("is used in a top-level splice, and must be imported, not defined locally"))]
519 | otherwise -- Badly staged
521 ptext SLIT("Stage error:") <+> pp_thing <+>
522 hsep [ptext SLIT("is bound at stage") <+> ppr bind_lvl,
523 ptext SLIT("but used at stage") <+> ppr use_lvl]
525 use_lvl = thLevel use_stage
528 topIdLvl :: Id -> ThLevel
529 -- Globals may either be imported, or may be from an earlier "chunk"
530 -- (separated by declaration splices) of this module. The former
531 -- *can* be used inside a top-level splice, but the latter cannot.
532 -- Hence we give the former impLevel, but the latter topLevel
536 -- By the time we are prcessing the $(f x), the binding for "x"
537 -- will be in the global env, not the local one.
538 topIdLvl id | isLocalId id = topLevel
539 | otherwise = impLevel
541 -- Indicates the legal transitions on bracket( [| |] ).
542 bracketOK :: ThStage -> Maybe ThLevel
543 bracketOK (Brack _ _ _) = Nothing -- Bracket illegal inside a bracket
544 bracketOK stage = Just (thLevel stage + 1)
546 -- Indicates the legal transitions on splice($).
547 spliceOK :: ThStage -> Maybe ThLevel
548 spliceOK (Splice _) = Nothing -- Splice illegal inside splice
549 spliceOK stage = Just (thLevel stage - 1)
551 tcMetaTy :: Name -> TcM Type
552 -- Given the name of a Template Haskell data type,
554 -- E.g. given the name "Expr" return the type "Expr"
556 = tcLookupTyCon tc_name `thenM` \ t ->
557 returnM (mkTyConApp t [])
561 %************************************************************************
563 \subsection{The InstInfo type}
565 %************************************************************************
567 The InstInfo type summarises the information in an instance declaration
569 instance c => k (t tvs) where b
571 It is used just for *local* instance decls (not ones from interface files).
572 But local instance decls includes
575 as well as explicit user written ones.
580 iSpec :: Instance, -- Includes the dfun id. Its forall'd type
581 iBinds :: InstBindings -- variables scope over the stuff in InstBindings!
584 iDFunId :: InstInfo -> DFunId
585 iDFunId info = instanceDFunId (iSpec info)
588 = VanillaInst -- The normal case
589 (LHsBinds Name) -- Bindings
590 [LSig Name] -- User pragmas recorded for generating
591 -- specialised instances
593 | NewTypeDerived -- Used for deriving instances of newtypes, where the
594 -- witness dictionary is identical to the argument
595 -- dictionary. Hence no bindings, no pragmas.
597 -- Nothing => The newtype-derived instance involves type variables,
598 -- and the dfun has a type like df :: forall a. Eq a => Eq (T a)
599 -- Just (r:scs) => The newtype-defined instance has no type variables
600 -- so the dfun is just a constant, df :: Eq T
601 -- In this case we need to know waht the rep dict, r, and the
602 -- superclasses, scs, are. (In the Nothing case these are in the
604 -- Invariant: these PredTypes have no free variables
605 -- NB: In both cases, the representation dict is the *first* dict.
607 pprInstInfo info = vcat [ptext SLIT("InstInfo:") <+> ppr (idType (iDFunId info))]
609 pprInstInfoDetails info = pprInstInfo info $$ nest 2 (details (iBinds info))
611 details (VanillaInst b _) = pprLHsBinds b
612 details (NewTypeDerived _) = text "Derived from the representation type"
614 simpleInstInfoClsTy :: InstInfo -> (Class, Type)
615 simpleInstInfoClsTy info = case instanceHead (iSpec info) of
616 (_, _, cls, [ty]) -> (cls, ty)
618 simpleInstInfoTy :: InstInfo -> Type
619 simpleInstInfoTy info = snd (simpleInstInfoClsTy info)
621 simpleInstInfoTyCon :: InstInfo -> TyCon
622 -- Gets the type constructor for a simple instance declaration,
623 -- i.e. one of the form instance (...) => C (T a b c) where ...
624 simpleInstInfoTyCon inst = tcTyConAppTyCon (simpleInstInfoTy inst)
627 Make a name for the dict fun for an instance decl. It's an *external*
628 name, like otber top-level names, and hence must be made with newGlobalBinder.
631 newDFunName :: Class -> [Type] -> SrcLoc -> TcM Name
632 newDFunName clas (ty:_) loc
633 = do { index <- nextDFunIndex
634 ; is_boot <- tcIsHsBoot
636 ; let info_string = occNameString (getOccName clas) ++
637 occNameString (getDFunTyKey ty)
638 dfun_occ = mkDFunOcc info_string is_boot index
640 ; newGlobalBinder mod dfun_occ loc }
642 newDFunName clas [] loc = pprPanic "newDFunName" (ppr clas <+> ppr loc)
645 Make a name for the representation tycon of a data/newtype instance. It's an
646 *external* name, like otber top-level names, and hence must be made with
650 newFamInstTyConName :: Name -> SrcLoc -> TcM Name
651 newFamInstTyConName tc_name loc
652 = do { index <- nextDFunIndex
654 ; let occ = nameOccName tc_name
655 ; newGlobalBinder mod (mkInstTyTcOcc index occ) loc }
659 %************************************************************************
663 %************************************************************************
666 pprBinders :: [Name] -> SDoc
667 -- Used in error messages
668 -- Use quotes for a single one; they look a bit "busy" for several
669 pprBinders [bndr] = quotes (ppr bndr)
670 pprBinders bndrs = pprWithCommas ppr bndrs
673 = failWithTc (ptext SLIT("GHC internal error:") <+> quotes (ppr name) <+>
674 ptext SLIT("is not in scope"))
676 wrongThingErr expected thing name
677 = failWithTc (pprTcTyThingCategory thing <+> quotes (ppr name) <+>
678 ptext SLIT("used as a") <+> text expected)
680 famInstNotFound tycon tys what
681 = failWithTc (msg <+> quotes (ppr tycon <+> hsep (map pprParendType tys)))
684 [] -> ptext SLIT("No instance for")
685 xs -> ptext SLIT("More than one instance for")