2 % (c) The University of Glasgow 2006
3 % (c) The GRASP Project, Glasgow University, 1992-2002
7 TcRnIf, TcRn, TcM, RnM, IfM, IfL, IfG, -- The monad is opaque outside this module
10 -- The environment types
12 TcGblEnv(..), TcLclEnv(..),
13 IfGblEnv(..), IfLclEnv(..),
16 ErrCtxt, RecFieldEnv(..),
17 ImportAvails(..), emptyImportAvails, plusImportAvails,
18 WhereFrom(..), mkModDeps,
21 TcTypeEnv, TcTyThing(..), pprTcTyThingCategory,
24 ThStage(..), topStage, topAnnStage, topSpliceStage,
25 ThLevel, impLevel, outerLevel, thLevel,
28 ArrowCtxt(NoArrowCtxt), newArrowScope, escapeArrowScope,
32 WantedConstraints, emptyWanteds, andWanteds, extendWanteds,
33 WantedConstraint(..), WantedEvVar(..), wantedEvVarLoc,
34 wantedEvVarToVar, wantedEvVarPred, splitWanteds,
38 CtLoc(..), ctLocSpan, ctLocOrigin, setCtLocOrigin,
39 CtOrigin(..), EqOrigin(..),
45 pprEvVarTheta, pprWantedsWithLocs, pprWantedWithLoc,
46 pprEvVars, pprEvVarWithType,
47 pprArising, pprArisingAt,
50 TcId, TcIdSet, TcTyVarBind(..), TcTyVarBinds
54 #include "HsVersions.h"
81 import StaticFlags( opt_ErrorSpans )
87 %************************************************************************
89 Standard monad definition for TcRn
90 All the combinators for the monad can be found in TcRnMonad
92 %************************************************************************
94 The monad itself has to be defined here, because it is mentioned by ErrCtxt
97 type TcRef a = IORef a
98 type TcId = Id -- Type may be a TcType DV: WHAT??????????
102 type TcRnIf a b c = IOEnv (Env a b) c
103 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
105 type IfG a = IfM () a -- Top level
106 type IfL a = IfM IfLclEnv a -- Nested
107 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
108 type RnM a = TcRn a -- Historical
109 type TcM a = TcRn a -- Historical
112 Representation of type bindings to uninstantiated meta variables used during
116 data TcTyVarBind = TcTyVarBind TcTyVar TcType
118 type TcTyVarBinds = Bag TcTyVarBind
120 instance Outputable TcTyVarBind where
121 ppr (TcTyVarBind tv ty) = ppr tv <+> text ":=" <+> ppr ty
125 %************************************************************************
127 The main environment types
129 %************************************************************************
132 data Env gbl lcl -- Changes as we move into an expression
134 env_top :: HscEnv, -- Top-level stuff that never changes
135 -- Includes all info about imported things
137 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
138 -- Unique supply for local varibles
140 env_gbl :: gbl, -- Info about things defined at the top level
141 -- of the module being compiled
143 env_lcl :: lcl -- Nested stuff; changes as we go into
146 -- TcGblEnv describes the top-level of the module at the
147 -- point at which the typechecker is finished work.
148 -- It is this structure that is handed on to the desugarer
152 tcg_mod :: Module, -- ^ Module being compiled
153 tcg_src :: HscSource,
154 -- ^ What kind of module (regular Haskell, hs-boot, ext-core)
156 tcg_rdr_env :: GlobalRdrEnv, -- ^ Top level envt; used during renaming
157 tcg_default :: Maybe [Type],
158 -- ^ Types used for defaulting. @Nothing@ => no @default@ decl
160 tcg_fix_env :: FixityEnv, -- ^ Just for things in this module
161 tcg_field_env :: RecFieldEnv, -- ^ Just for things in this module
163 tcg_type_env :: TypeEnv,
164 -- ^ Global type env for the module we are compiling now. All
165 -- TyCons and Classes (for this module) end up in here right away,
166 -- along with their derived constructors, selectors.
168 -- (Ids defined in this module start in the local envt, though they
169 -- move to the global envt during zonking)
171 tcg_type_env_var :: TcRef TypeEnv,
172 -- Used only to initialise the interface-file
173 -- typechecker in initIfaceTcRn, so that it can see stuff
174 -- bound in this module when dealing with hi-boot recursions
175 -- Updated at intervals (e.g. after dealing with types and classes)
177 tcg_inst_env :: InstEnv,
178 -- ^ Instance envt for /home-package/ modules; Includes the dfuns in
180 tcg_fam_inst_env :: FamInstEnv, -- ^ Ditto for family instances
182 -- Now a bunch of things about this module that are simply
183 -- accumulated, but never consulted until the end.
184 -- Nevertheless, it's convenient to accumulate them along
185 -- with the rest of the info from this module.
186 tcg_exports :: [AvailInfo], -- ^ What is exported
187 tcg_imports :: ImportAvails,
188 -- ^ Information about what was imported from where, including
189 -- things bound in this module.
192 -- ^ What is defined in this module and what is used.
193 -- The latter is used to generate
195 -- (a) version tracking; no need to recompile if these things have
196 -- not changed version stamp
198 -- (b) unused-import info
200 tcg_keep :: TcRef NameSet,
201 -- ^ Locally-defined top-level names to keep alive.
203 -- "Keep alive" means give them an Exported flag, so that the
204 -- simplifier does not discard them as dead code, and so that they
205 -- are exposed in the interface file (but not to export to the
208 -- Some things, like dict-fun Ids and default-method Ids are "born"
209 -- with the Exported flag on, for exactly the above reason, but some
210 -- we only discover as we go. Specifically:
212 -- * The to/from functions for generic data types
214 -- * Top-level variables appearing free in the RHS of an orphan
217 -- * Top-level variables appearing free in a TH bracket
219 tcg_inst_uses :: TcRef NameSet,
220 -- ^ Home-package Dfuns actually used.
222 -- Used to generate version dependencies This records usages, rather
223 -- like tcg_dus, but it has to be a mutable variable so it can be
224 -- augmented when we look up an instance. These uses of dfuns are
225 -- rather like the free variables of the program, but are implicit
226 -- instead of explicit.
228 tcg_th_used :: TcRef Bool,
229 -- ^ @True@ <=> Template Haskell syntax used.
231 -- We need this so that we can generate a dependency on the Template
232 -- Haskell package, becuase the desugarer is going to emit loads of
233 -- references to TH symbols. It's rather like tcg_inst_uses; the
234 -- reference is implicit rather than explicit, so we have to zap a
237 tcg_dfun_n :: TcRef OccSet,
238 -- ^ Allows us to choose unique DFun names.
240 -- The next fields accumulate the payload of the module
241 -- The binds, rules and foreign-decl fiels are collected
242 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
244 tcg_rn_exports :: Maybe [Located (IE Name)],
245 tcg_rn_imports :: [LImportDecl Name],
246 -- Keep the renamed imports regardless. They are not
247 -- voluminous and are needed if you want to report unused imports
249 tcg_used_rdrnames :: TcRef (Set RdrName),
250 -- The set of used *imported* (not locally-defined) RdrNames
251 -- Used only to report unused import declarations
253 tcg_rn_decls :: Maybe (HsGroup Name),
254 -- ^ Renamed decls, maybe. @Nothing@ <=> Don't retain renamed
257 tcg_ev_binds :: Bag EvBind, -- Top-level evidence bindings
258 tcg_binds :: LHsBinds Id, -- Value bindings in this module
259 tcg_sigs :: NameSet, -- ...Top-level names that *lack* a signature
260 tcg_warns :: Warnings, -- ...Warnings and deprecations
261 tcg_anns :: [Annotation], -- ...Annotations
262 tcg_insts :: [Instance], -- ...Instances
263 tcg_fam_insts :: [FamInst], -- ...Family instances
264 tcg_rules :: [LRuleDecl Id], -- ...Rules
265 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
267 tcg_doc_hdr :: Maybe LHsDocString, -- ^ Maybe Haddock header docs
268 tcg_hpc :: AnyHpcUsage, -- ^ @True@ if any part of the
269 -- prog uses hpc instrumentation.
271 tcg_main :: Maybe Name -- ^ The Name of the main
272 -- function, if this module is
277 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
278 -- to the fields for that constructor
279 NameSet -- Set of all fields declared *in this module*;
280 -- used to suppress name-shadowing complaints
281 -- when using record wild cards
282 -- E.g. let fld = e in C {..}
283 -- This is used when dealing with ".." notation in record
284 -- construction and pattern matching.
285 -- The FieldEnv deals *only* with constructors defined in *this*
286 -- module. For imported modules, we get the same info from the
290 %************************************************************************
292 The interface environments
293 Used when dealing with IfaceDecls
295 %************************************************************************
300 -- The type environment for the module being compiled,
301 -- in case the interface refers back to it via a reference that
302 -- was originally a hi-boot file.
303 -- We need the module name so we can test when it's appropriate
304 -- to look in this env.
305 if_rec_types :: Maybe (Module, IfG TypeEnv)
306 -- Allows a read effect, so it can be in a mutable
307 -- variable; c.f. handling the external package type env
308 -- Nothing => interactive stuff, no loops possible
313 -- The module for the current IfaceDecl
314 -- So if we see f = \x -> x
315 -- it means M.f = \x -> x, where M is the if_mod
318 -- The field is used only for error reporting
319 -- if (say) there's a Lint error in it
321 -- Where the interface came from:
322 -- .hi file, or GHCi state, or ext core
323 -- plus which bit is currently being examined
325 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
326 if_id_env :: UniqFM Id -- Nested id binding
331 %************************************************************************
333 The local typechecker environment
335 %************************************************************************
337 The Global-Env/Local-Env story
338 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
339 During type checking, we keep in the tcg_type_env
340 * All types and classes
341 * All Ids derived from types and classes (constructors, selectors)
343 At the end of type checking, we zonk the local bindings,
344 and as we do so we add to the tcg_type_env
345 * Locally defined top-level Ids
347 Why? Because they are now Ids not TcIds. This final GlobalEnv is
348 a) fed back (via the knot) to typechecking the
349 unfoldings of interface signatures
350 b) used in the ModDetails of this module
353 data TcLclEnv -- Changes as we move inside an expression
354 -- Discarded after typecheck/rename; not passed on to desugarer
356 tcl_loc :: SrcSpan, -- Source span
357 tcl_ctxt :: [ErrCtxt], -- Error context, innermost on top
358 tcl_errs :: TcRef Messages, -- Place to accumulate errors
360 tcl_th_ctxt :: ThStage, -- Template Haskell context
361 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
363 tcl_rdr :: LocalRdrEnv, -- Local name envt
364 -- Maintained during renaming, of course, but also during
365 -- type checking, solely so that when renaming a Template-Haskell
366 -- splice we have the right environment for the renamer.
368 -- Does *not* include global name envt; may shadow it
369 -- Includes both ordinary variables and type variables;
370 -- they are kept distinct because tyvar have a different
371 -- occurrence contructor (Name.TvOcc)
372 -- We still need the unsullied global name env so that
373 -- we can look up record field names
375 tcl_env :: TcTypeEnv, -- The local type environment: Ids and
376 -- TyVars defined in this module
378 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
379 -- Namely, the in-scope TyVars bound in tcl_env,
380 -- plus the tyvars mentioned in the types of Ids bound
382 -- Why mutable? see notes with tcGetGlobalTyVars
384 tcl_lie :: TcRef WantedConstraints, -- Place to accumulate type constraints
385 tcl_untch :: Untouchables -- Untouchables
388 type TcTypeEnv = NameEnv TcTyThing
391 {- Note [Given Insts]
393 Because of GADTs, we have to pass inwards the Insts provided by type signatures
394 and existential contexts. Consider
395 data T a where { T1 :: b -> b -> T [b] }
396 f :: Eq a => T a -> Bool
397 f (T1 x y) = [x]==[y]
399 The constructor T1 binds an existential variable 'b', and we need Eq [b].
400 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
405 ---------------------------
406 -- Template Haskell stages and levels
407 ---------------------------
409 data ThStage -- See Note [Template Haskell state diagram] in TcSplice
410 = Splice -- Top-level splicing
411 -- This code will be run *at compile time*;
412 -- the result replaces the splice
415 | Comp -- Ordinary Haskell code
418 | Brack -- Inside brackets
419 ThStage -- Binding level = level(stage) + 1
420 (TcRef [PendingSplice]) -- Accumulate pending splices here
421 (TcRef WantedConstraints) -- and type constraints here
423 topStage, topAnnStage, topSpliceStage :: ThStage
426 topSpliceStage = Splice
428 instance Outputable ThStage where
429 ppr Splice = text "Splice"
430 ppr Comp = text "Comp"
431 ppr (Brack s _ _) = text "Brack" <> parens (ppr s)
434 -- See Note [Template Haskell levels] in TcSplice
435 -- Incremented when going inside a bracket,
436 -- decremented when going inside a splice
437 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
438 -- original "Template meta-programming for Haskell" paper
440 impLevel, outerLevel :: ThLevel
441 impLevel = 0 -- Imported things; they can be used inside a top level splice
442 outerLevel = 1 -- Things defined outside brackets
443 -- NB: Things at level 0 are not *necessarily* imported.
444 -- eg $( \b -> ... ) here b is bound at level 0
448 -- g1 = $(map ...) is OK
449 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
451 thLevel :: ThStage -> ThLevel
454 thLevel (Brack s _ _) = thLevel s + 1
456 ---------------------------
457 -- Arrow-notation context
458 ---------------------------
461 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
462 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
467 Here, x is not in scope in e1, but it is in scope in e2. This can get
471 proc y -> (proc z -> e1) -< e2
473 Here, x and z are in scope in e1, but y is not. We implement this by
474 recording the environment when passing a proc (using newArrowScope),
475 and returning to that (using escapeArrowScope) on the left of -< and the
481 | ArrowCtxt (Env TcGblEnv TcLclEnv)
483 -- Record the current environment (outside a proc)
484 newArrowScope :: TcM a -> TcM a
487 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
489 -- Return to the stored environment (from the enclosing proc)
490 escapeArrowScope :: TcM a -> TcM a
492 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
494 ArrowCtxt env' -> env'
496 ---------------------------
498 ---------------------------
501 = AGlobal TyThing -- Used only in the return type of a lookup
503 | ATcId { -- Ids defined in this module; may not be fully zonked
505 tct_level :: ThLevel }
507 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
508 -- is currently refined. We only need the Name
509 -- for error-message purposes; it is the corresponding
510 -- Name in the domain of the envt
512 | AThing TcKind -- Used temporarily, during kind checking, for the
513 -- tycons and clases in this recursive group
515 instance Outputable TcTyThing where -- Debugging only
516 ppr (AGlobal g) = pprTyThing g
517 ppr elt@(ATcId {}) = text "Identifier" <>
518 brackets (ppr (tct_id elt) <> dcolon
519 <> ppr (varType (tct_id elt)) <> comma
520 <+> ppr (tct_level elt))
521 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
522 ppr (AThing k) = text "AThing" <+> ppr k
524 pprTcTyThingCategory :: TcTyThing -> SDoc
525 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
526 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
527 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
528 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
532 type ErrCtxt = (Bool, TidyEnv -> TcM (TidyEnv, Message))
533 -- Monadic so that we have a chance
534 -- to deal with bound type variables just before error
535 -- message construction
537 -- Bool: True <=> this is a landmark context; do not
538 -- discard it when trimming for display
542 %************************************************************************
544 Operations over ImportAvails
546 %************************************************************************
549 -- | 'ImportAvails' summarises what was imported from where, irrespective of
550 -- whether the imported things are actually used or not. It is used:
552 -- * when processing the export list,
554 -- * when constructing usage info for the interface file,
556 -- * to identify the list of directly imported modules for initialisation
557 -- purposes and for optimised overlap checking of family instances,
559 -- * when figuring out what things are really unused
563 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
564 -- ^ Domain is all directly-imported modules
565 -- The 'ModuleName' is what the module was imported as, e.g. in
573 -- - @True@ => import was @import Foo ()@
575 -- - @False@ => import was some other form
579 -- (a) to help construct the usage information in the interface
580 -- file; if we import somethign we need to recompile if the
581 -- export version changes
583 -- (b) to specify what child modules to initialise
585 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
586 -- because we might be importing modules of the same name from
587 -- different packages. (currently not the case, but might be in the
590 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
591 -- ^ Home-package modules needed by the module being compiled
593 -- It doesn't matter whether any of these dependencies
594 -- are actually /used/ when compiling the module; they
595 -- are listed if they are below it at all. For
596 -- example, suppose M imports A which imports X. Then
597 -- compiling M might not need to consult X.hi, but X
598 -- is still listed in M's dependencies.
600 imp_dep_pkgs :: [PackageId],
601 -- ^ Packages needed by the module being compiled, whether directly,
602 -- or via other modules in this package, or via modules imported
603 -- from other packages.
605 imp_orphs :: [Module],
606 -- ^ Orphan modules below us in the import tree (and maybe including
607 -- us for imported modules)
609 imp_finsts :: [Module]
610 -- ^ Family instance modules below us in the import tree (and maybe
611 -- including us for imported modules)
614 mkModDeps :: [(ModuleName, IsBootInterface)]
615 -> ModuleNameEnv (ModuleName, IsBootInterface)
616 mkModDeps deps = foldl add emptyUFM deps
618 add env elt@(m,_) = addToUFM env m elt
620 emptyImportAvails :: ImportAvails
621 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
622 imp_dep_mods = emptyUFM,
627 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
629 (ImportAvails { imp_mods = mods1,
630 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
631 imp_orphs = orphs1, imp_finsts = finsts1 })
632 (ImportAvails { imp_mods = mods2,
633 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
634 imp_orphs = orphs2, imp_finsts = finsts2 })
635 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
636 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
637 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
638 imp_orphs = orphs1 `unionLists` orphs2,
639 imp_finsts = finsts1 `unionLists` finsts2 }
641 plus_mod_dep (m1, boot1) (m2, boot2)
642 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
643 -- Check mod-names match
644 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
647 %************************************************************************
649 \subsection{Where from}
651 %************************************************************************
653 The @WhereFrom@ type controls where the renamer looks for an interface file
657 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
658 | ImportBySystem -- Non user import.
660 instance Outputable WhereFrom where
661 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
663 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
667 %************************************************************************
671 These are forced to be in TcRnTypes because
672 TcLclEnv mentions WantedConstraints
673 WantedConstraint mentions CtLoc
674 CtLoc mentions ErrCtxt
677 v%************************************************************************
680 type Untouchables = TcTyVarSet -- All MetaTyVars
682 type WantedConstraints = Bag WantedConstraint
684 data WantedConstraint
685 = WcEvVar WantedEvVar
686 | WcImplic Implication
687 -- ToDo: add literals, methods
689 -- EvVar defined in module Var.lhs:
690 -- Evidence variables include all *quantifiable* constraints
692 -- implicit parameters
693 -- coercion variables
695 data WantedEvVar -- The sort of constraint over which one can lambda-abstract
697 EvVar -- The variable itself; make a binding for it please
698 WantedLoc -- How the constraint arose in the first place
699 -- (used for error messages only)
701 type WantedLoc = CtLoc CtOrigin
702 type GivenLoc = CtLoc SkolemInfo
706 ic_env_tvs :: Untouchables, -- Untouchables: unification variables
707 -- free in the environment
708 ic_env :: TcTypeEnv, -- The type environment
709 -- Used only when generating error messages
710 -- Generally, ic_env_tvs = tvsof(ic_env)
711 -- However, we don't zonk ic_env when zonking the Implication
712 -- Instead we do that when generating a skolem-escape error message
714 ic_skols :: TcTyVarSet, -- Introduced skolems
715 -- See Note [Skolems in an implication]
717 ic_scoped :: [TcTyVar], -- List of scoped variables to be unified
718 -- bijectively to a subset of ic_tyvars
719 -- Note [Scoped pattern variable]
721 ic_given :: [EvVar], -- Given evidence variables
722 -- (order does not matter)
724 ic_wanted :: WantedConstraints, -- Wanted constraints
726 ic_binds :: EvBindsVar, -- Points to the place to fill in the
727 -- abstraction and bindings
731 evVarsToWanteds :: WantedLoc -> [EvVar] -> WantedConstraints
732 evVarsToWanteds loc evs = listToBag [WcEvVar (WantedEvVar ev loc) | ev <- evs]
734 wantedEvVarLoc :: WantedEvVar -> WantedLoc
735 wantedEvVarLoc (WantedEvVar _ loc) = loc
737 wantedEvVarToVar :: WantedEvVar -> EvVar
738 wantedEvVarToVar (WantedEvVar ev _) = ev
740 wantedEvVarPred :: WantedEvVar -> PredType
741 wantedEvVarPred (WantedEvVar ev _) = evVarPred ev
743 splitWanteds :: WantedConstraints -> (Bag WantedEvVar, Bag Implication)
744 splitWanteds wanted = partitionBagWith pick wanted
746 pick (WcEvVar v) = Left v
747 pick (WcImplic i) = Right i
750 Note [Skolems in an implication]
751 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
752 The skolems in an implication are not there to perform a skolem escape
753 check. That happens because all the environment variables are in the
754 untouchables, and therefore cannot be unified with anything at all,
755 let alone the skolems.
757 Instead, ic_skols is used only when considering floating a constraint
758 outside the implication in TcSimplify.floatEqualities or
759 TcSimplify.approximateImplications
761 Note [Scoped pattern variables]
762 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
763 data T where K :: forall a,b. a -> b -> T
765 ...(case x of K (p::c) (q::d) -> ...)...
767 We create fresh MetaTvs for c,d, and later check that they are
768 bound bijectively to the skolems we created for a,b. So the
769 implication constraint looks like
770 ic_skols = {a',b'} -- Skolem tvs created from a,b
771 ic_scoped = {c',d'} -- Meta tvs created from c,d
774 emptyWanteds :: WantedConstraints
775 emptyWanteds = emptyBag
777 andWanteds :: WantedConstraints -> WantedConstraints -> WantedConstraints
778 andWanteds = unionBags
780 extendWanteds :: WantedConstraints -> WantedConstraint -> WantedConstraints
781 extendWanteds = snocBag
785 pprEvVars :: [EvVar] -> SDoc -- Print with their types
786 pprEvVars ev_vars = vcat (map pprEvVarWithType ev_vars)
788 pprEvVarTheta :: [EvVar] -> SDoc
789 pprEvVarTheta ev_vars = pprTheta (map evVarPred ev_vars)
791 pprEvVarWithType :: EvVar -> SDoc
792 pprEvVarWithType v = ppr v <+> dcolon <+> pprPred (evVarPred v)
794 pprWantedsWithLocs :: Bag WantedConstraint -> SDoc
795 pprWantedsWithLocs = foldrBag (($$) . pprWantedWithLoc) empty
797 pprWantedWithLoc :: WantedConstraint -> SDoc
798 pprWantedWithLoc (WcImplic i) = ppr i
799 pprWantedWithLoc (WcEvVar v) = pprWantedEvVarWithLoc v
801 instance Outputable WantedConstraint where
802 ppr (WcEvVar v) = ppr v
803 ppr (WcImplic i) = ppr i
805 -- Adding -ferror-spans makes the output more voluminous
806 instance Outputable WantedEvVar where
807 ppr wev | opt_ErrorSpans = pprWantedEvVarWithLoc wev
808 | otherwise = pprWantedEvVar wev
810 pprWantedEvVarWithLoc, pprWantedEvVar :: WantedEvVar -> SDoc
811 pprWantedEvVarWithLoc (WantedEvVar v loc) = hang (pprEvVarWithType v)
813 pprWantedEvVar (WantedEvVar v _) = pprEvVarWithType v
815 instance Outputable Implication where
816 ppr (Implic { ic_env_tvs = env_tvs, ic_skols = skols, ic_given = given
817 , ic_wanted = wanted, ic_binds = binds, ic_loc = loc })
818 = ptext (sLit "Implic") <+> braces
819 (sep [ ptext (sLit "Untouchables = ") <+> ppr env_tvs
820 , ptext (sLit "Skolems = ") <+> ppr skols
821 , ptext (sLit "Given = ") <+> pprEvVars given
822 , ptext (sLit "Wanted = ") <+> ppr wanted
823 , ptext (sLit "Binds = ") <+> ppr binds
824 , pprSkolInfo (ctLocOrigin loc)
825 , ppr (ctLocSpan loc) ])
828 %************************************************************************
832 %************************************************************************
834 The 'CtLoc' and 'CtOrigin' types gives information about where a
835 *wanted constraint* came from. This is important for decent error
836 message reporting because dictionaries don't appear in the original
837 source code. Doubtless this type will evolve...
840 -------------------------------------------
841 data CtLoc orig = CtLoc orig SrcSpan [ErrCtxt]
843 ctLocSpan :: CtLoc o -> SrcSpan
844 ctLocSpan (CtLoc _ s _) = s
846 ctLocOrigin :: CtLoc o -> o
847 ctLocOrigin (CtLoc o _ _) = o
849 setCtLocOrigin :: CtLoc o -> o' -> CtLoc o'
850 setCtLocOrigin (CtLoc _ s c) o = CtLoc o s c
852 pprArising :: CtOrigin -> SDoc
853 pprArising (TypeEqOrigin {}) = empty
854 pprArising orig = text "arising from" <+> ppr orig
856 pprArisingAt :: CtLoc CtOrigin -> SDoc
857 pprArisingAt (CtLoc o s _) = sep [pprArising o, text "at" <+> ppr s]
859 -------------------------------------------
860 -- CtOrigin gives the origin of *wanted* constraints
862 = OccurrenceOf Name -- Occurrence of an overloaded identifier
863 | AppOrigin -- An application of some kind
865 | SpecPragOrigin Name -- Specialisation pragma for identifier
867 | TypeEqOrigin EqOrigin
869 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
871 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
872 | NegateOrigin -- Occurrence of syntactic negation
874 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
875 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
877 | TupleOrigin -- (..,..)
878 | ExprSigOrigin -- e :: ty
879 | PatSigOrigin -- p :: ty
880 | PatOrigin -- Instantiating a polytyped pattern at a constructor
884 | ScOrigin -- Typechecking superclasses of an instance declaration
885 | DerivOrigin -- Typechecking deriving
886 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
887 | DefaultOrigin -- Typechecking a default decl
888 | DoOrigin -- Arising from a do expression
889 | ProcOrigin -- Arising from a proc expression
890 | AnnOrigin -- An annotation
894 { uo_actual :: TcType
895 , uo_expected :: TcType }
897 instance Outputable CtOrigin where
900 pprO :: CtOrigin -> SDoc
901 pprO (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
902 pprO AppOrigin = ptext (sLit "an application")
903 pprO (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
904 pprO (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
905 pprO RecordUpdOrigin = ptext (sLit "a record update")
906 pprO ExprSigOrigin = ptext (sLit "an expression type signature")
907 pprO PatSigOrigin = ptext (sLit "a pattern type signature")
908 pprO PatOrigin = ptext (sLit "a pattern")
909 pprO ViewPatOrigin = ptext (sLit "a view pattern")
910 pprO (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
911 pprO (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
912 pprO (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
913 pprO SectionOrigin = ptext (sLit "an operator section")
914 pprO TupleOrigin = ptext (sLit "a tuple")
915 pprO NegateOrigin = ptext (sLit "a use of syntactic negation")
916 pprO ScOrigin = ptext (sLit "the superclasses of an instance declaration")
917 pprO DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
918 pprO StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
919 pprO DefaultOrigin = ptext (sLit "a 'default' declaration")
920 pprO DoOrigin = ptext (sLit "a do statement")
921 pprO ProcOrigin = ptext (sLit "a proc expression")
922 pprO (TypeEqOrigin eq) = ptext (sLit "an equality") <+> ppr eq
923 pprO AnnOrigin = ptext (sLit "an annotation")
925 instance Outputable EqOrigin where
926 ppr (UnifyOrigin t1 t2) = ppr t1 <+> char '~' <+> ppr t2