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_imp_specs :: [LTcSpecPrag], -- ...SPECIALISE prags for imported Ids
261 tcg_warns :: Warnings, -- ...Warnings and deprecations
262 tcg_anns :: [Annotation], -- ...Annotations
263 tcg_insts :: [Instance], -- ...Instances
264 tcg_fam_insts :: [FamInst], -- ...Family instances
265 tcg_rules :: [LRuleDecl Id], -- ...Rules
266 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
268 tcg_doc_hdr :: Maybe LHsDocString, -- ^ Maybe Haddock header docs
269 tcg_hpc :: AnyHpcUsage, -- ^ @True@ if any part of the
270 -- prog uses hpc instrumentation.
272 tcg_main :: Maybe Name -- ^ The Name of the main
273 -- function, if this module is
278 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
279 -- to the fields for that constructor
280 NameSet -- Set of all fields declared *in this module*;
281 -- used to suppress name-shadowing complaints
282 -- when using record wild cards
283 -- E.g. let fld = e in C {..}
284 -- This is used when dealing with ".." notation in record
285 -- construction and pattern matching.
286 -- The FieldEnv deals *only* with constructors defined in *this*
287 -- module. For imported modules, we get the same info from the
291 %************************************************************************
293 The interface environments
294 Used when dealing with IfaceDecls
296 %************************************************************************
301 -- The type environment for the module being compiled,
302 -- in case the interface refers back to it via a reference that
303 -- was originally a hi-boot file.
304 -- We need the module name so we can test when it's appropriate
305 -- to look in this env.
306 if_rec_types :: Maybe (Module, IfG TypeEnv)
307 -- Allows a read effect, so it can be in a mutable
308 -- variable; c.f. handling the external package type env
309 -- Nothing => interactive stuff, no loops possible
314 -- The module for the current IfaceDecl
315 -- So if we see f = \x -> x
316 -- it means M.f = \x -> x, where M is the if_mod
319 -- The field is used only for error reporting
320 -- if (say) there's a Lint error in it
322 -- Where the interface came from:
323 -- .hi file, or GHCi state, or ext core
324 -- plus which bit is currently being examined
326 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
327 if_id_env :: UniqFM Id -- Nested id binding
332 %************************************************************************
334 The local typechecker environment
336 %************************************************************************
338 The Global-Env/Local-Env story
339 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
340 During type checking, we keep in the tcg_type_env
341 * All types and classes
342 * All Ids derived from types and classes (constructors, selectors)
344 At the end of type checking, we zonk the local bindings,
345 and as we do so we add to the tcg_type_env
346 * Locally defined top-level Ids
348 Why? Because they are now Ids not TcIds. This final GlobalEnv is
349 a) fed back (via the knot) to typechecking the
350 unfoldings of interface signatures
351 b) used in the ModDetails of this module
354 data TcLclEnv -- Changes as we move inside an expression
355 -- Discarded after typecheck/rename; not passed on to desugarer
357 tcl_loc :: SrcSpan, -- Source span
358 tcl_ctxt :: [ErrCtxt], -- Error context, innermost on top
359 tcl_errs :: TcRef Messages, -- Place to accumulate errors
361 tcl_th_ctxt :: ThStage, -- Template Haskell context
362 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
364 tcl_rdr :: LocalRdrEnv, -- Local name envt
365 -- Maintained during renaming, of course, but also during
366 -- type checking, solely so that when renaming a Template-Haskell
367 -- splice we have the right environment for the renamer.
369 -- Does *not* include global name envt; may shadow it
370 -- Includes both ordinary variables and type variables;
371 -- they are kept distinct because tyvar have a different
372 -- occurrence contructor (Name.TvOcc)
373 -- We still need the unsullied global name env so that
374 -- we can look up record field names
376 tcl_env :: TcTypeEnv, -- The local type environment: Ids and
377 -- TyVars defined in this module
379 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
380 -- Namely, the in-scope TyVars bound in tcl_env,
381 -- plus the tyvars mentioned in the types of Ids bound
383 -- Why mutable? see notes with tcGetGlobalTyVars
385 tcl_lie :: TcRef WantedConstraints, -- Place to accumulate type constraints
386 tcl_untch :: Untouchables -- Untouchables
389 type TcTypeEnv = NameEnv TcTyThing
392 {- Note [Given Insts]
394 Because of GADTs, we have to pass inwards the Insts provided by type signatures
395 and existential contexts. Consider
396 data T a where { T1 :: b -> b -> T [b] }
397 f :: Eq a => T a -> Bool
398 f (T1 x y) = [x]==[y]
400 The constructor T1 binds an existential variable 'b', and we need Eq [b].
401 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
406 ---------------------------
407 -- Template Haskell stages and levels
408 ---------------------------
410 data ThStage -- See Note [Template Haskell state diagram] in TcSplice
411 = Splice -- Top-level splicing
412 -- This code will be run *at compile time*;
413 -- the result replaces the splice
416 | Comp -- Ordinary Haskell code
419 | Brack -- Inside brackets
420 ThStage -- Binding level = level(stage) + 1
421 (TcRef [PendingSplice]) -- Accumulate pending splices here
422 (TcRef WantedConstraints) -- and type constraints here
424 topStage, topAnnStage, topSpliceStage :: ThStage
427 topSpliceStage = Splice
429 instance Outputable ThStage where
430 ppr Splice = text "Splice"
431 ppr Comp = text "Comp"
432 ppr (Brack s _ _) = text "Brack" <> parens (ppr s)
435 -- See Note [Template Haskell levels] in TcSplice
436 -- Incremented when going inside a bracket,
437 -- decremented when going inside a splice
438 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
439 -- original "Template meta-programming for Haskell" paper
441 impLevel, outerLevel :: ThLevel
442 impLevel = 0 -- Imported things; they can be used inside a top level splice
443 outerLevel = 1 -- Things defined outside brackets
444 -- NB: Things at level 0 are not *necessarily* imported.
445 -- eg $( \b -> ... ) here b is bound at level 0
449 -- g1 = $(map ...) is OK
450 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
452 thLevel :: ThStage -> ThLevel
455 thLevel (Brack s _ _) = thLevel s + 1
457 ---------------------------
458 -- Arrow-notation context
459 ---------------------------
462 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
463 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
468 Here, x is not in scope in e1, but it is in scope in e2. This can get
472 proc y -> (proc z -> e1) -< e2
474 Here, x and z are in scope in e1, but y is not. We implement this by
475 recording the environment when passing a proc (using newArrowScope),
476 and returning to that (using escapeArrowScope) on the left of -< and the
482 | ArrowCtxt (Env TcGblEnv TcLclEnv)
484 -- Record the current environment (outside a proc)
485 newArrowScope :: TcM a -> TcM a
488 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
490 -- Return to the stored environment (from the enclosing proc)
491 escapeArrowScope :: TcM a -> TcM a
493 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
495 ArrowCtxt env' -> env'
497 ---------------------------
499 ---------------------------
502 = AGlobal TyThing -- Used only in the return type of a lookup
504 | ATcId { -- Ids defined in this module; may not be fully zonked
506 tct_level :: ThLevel }
508 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
509 -- is currently refined. We only need the Name
510 -- for error-message purposes; it is the corresponding
511 -- Name in the domain of the envt
513 | AThing TcKind -- Used temporarily, during kind checking, for the
514 -- tycons and clases in this recursive group
516 instance Outputable TcTyThing where -- Debugging only
517 ppr (AGlobal g) = pprTyThing g
518 ppr elt@(ATcId {}) = text "Identifier" <>
519 brackets (ppr (tct_id elt) <> dcolon
520 <> ppr (varType (tct_id elt)) <> comma
521 <+> ppr (tct_level elt))
522 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
523 ppr (AThing k) = text "AThing" <+> ppr k
525 pprTcTyThingCategory :: TcTyThing -> SDoc
526 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
527 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
528 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
529 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
533 type ErrCtxt = (Bool, TidyEnv -> TcM (TidyEnv, Message))
534 -- Monadic so that we have a chance
535 -- to deal with bound type variables just before error
536 -- message construction
538 -- Bool: True <=> this is a landmark context; do not
539 -- discard it when trimming for display
543 %************************************************************************
545 Operations over ImportAvails
547 %************************************************************************
550 -- | 'ImportAvails' summarises what was imported from where, irrespective of
551 -- whether the imported things are actually used or not. It is used:
553 -- * when processing the export list,
555 -- * when constructing usage info for the interface file,
557 -- * to identify the list of directly imported modules for initialisation
558 -- purposes and for optimised overlap checking of family instances,
560 -- * when figuring out what things are really unused
564 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
565 -- ^ Domain is all directly-imported modules
566 -- The 'ModuleName' is what the module was imported as, e.g. in
574 -- - @True@ => import was @import Foo ()@
576 -- - @False@ => import was some other form
580 -- (a) to help construct the usage information in the interface
581 -- file; if we import somethign we need to recompile if the
582 -- export version changes
584 -- (b) to specify what child modules to initialise
586 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
587 -- because we might be importing modules of the same name from
588 -- different packages. (currently not the case, but might be in the
591 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
592 -- ^ Home-package modules needed by the module being compiled
594 -- It doesn't matter whether any of these dependencies
595 -- are actually /used/ when compiling the module; they
596 -- are listed if they are below it at all. For
597 -- example, suppose M imports A which imports X. Then
598 -- compiling M might not need to consult X.hi, but X
599 -- is still listed in M's dependencies.
601 imp_dep_pkgs :: [PackageId],
602 -- ^ Packages needed by the module being compiled, whether directly,
603 -- or via other modules in this package, or via modules imported
604 -- from other packages.
606 imp_orphs :: [Module],
607 -- ^ Orphan modules below us in the import tree (and maybe including
608 -- us for imported modules)
610 imp_finsts :: [Module]
611 -- ^ Family instance modules below us in the import tree (and maybe
612 -- including us for imported modules)
615 mkModDeps :: [(ModuleName, IsBootInterface)]
616 -> ModuleNameEnv (ModuleName, IsBootInterface)
617 mkModDeps deps = foldl add emptyUFM deps
619 add env elt@(m,_) = addToUFM env m elt
621 emptyImportAvails :: ImportAvails
622 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
623 imp_dep_mods = emptyUFM,
628 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
630 (ImportAvails { imp_mods = mods1,
631 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
632 imp_orphs = orphs1, imp_finsts = finsts1 })
633 (ImportAvails { imp_mods = mods2,
634 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
635 imp_orphs = orphs2, imp_finsts = finsts2 })
636 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
637 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
638 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
639 imp_orphs = orphs1 `unionLists` orphs2,
640 imp_finsts = finsts1 `unionLists` finsts2 }
642 plus_mod_dep (m1, boot1) (m2, boot2)
643 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
644 -- Check mod-names match
645 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
648 %************************************************************************
650 \subsection{Where from}
652 %************************************************************************
654 The @WhereFrom@ type controls where the renamer looks for an interface file
658 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
659 | ImportBySystem -- Non user import.
661 instance Outputable WhereFrom where
662 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
664 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
668 %************************************************************************
672 These are forced to be in TcRnTypes because
673 TcLclEnv mentions WantedConstraints
674 WantedConstraint mentions CtLoc
675 CtLoc mentions ErrCtxt
678 v%************************************************************************
681 type Untouchables = TcTyVarSet -- All MetaTyVars
683 type WantedConstraints = Bag WantedConstraint
685 data WantedConstraint
686 = WcEvVar WantedEvVar
687 | WcImplic Implication
688 -- ToDo: add literals, methods
690 -- EvVar defined in module Var.lhs:
691 -- Evidence variables include all *quantifiable* constraints
693 -- implicit parameters
694 -- coercion variables
696 data WantedEvVar -- The sort of constraint over which one can lambda-abstract
698 EvVar -- The variable itself; make a binding for it please
699 WantedLoc -- How the constraint arose in the first place
700 -- (used for error messages only)
702 type WantedLoc = CtLoc CtOrigin
703 type GivenLoc = CtLoc SkolemInfo
707 ic_untch :: Untouchables, -- Untouchables: unification variables
708 -- free in the environment
709 ic_env :: TcTypeEnv, -- The type environment
710 -- Used only when generating error messages
711 -- Generally, ic_untch is a superset of tvsof(ic_env)
712 -- However, we don't zonk ic_env when zonking the Implication
713 -- Instead we do that when generating a skolem-escape error message
715 ic_skols :: TcTyVarSet, -- Introduced skolems
716 -- See Note [Skolems in an implication]
718 ic_scoped :: [TcTyVar], -- List of scoped variables to be unified
719 -- bijectively to a subset of ic_tyvars
720 -- Note [Scoped pattern variable]
722 ic_given :: [EvVar], -- Given evidence variables
723 -- (order does not matter)
725 ic_wanted :: WantedConstraints, -- Wanted constraints
727 ic_binds :: EvBindsVar, -- Points to the place to fill in the
728 -- abstraction and bindings
732 evVarsToWanteds :: WantedLoc -> [EvVar] -> WantedConstraints
733 evVarsToWanteds loc evs = listToBag [WcEvVar (WantedEvVar ev loc) | ev <- evs]
735 wantedEvVarLoc :: WantedEvVar -> WantedLoc
736 wantedEvVarLoc (WantedEvVar _ loc) = loc
738 wantedEvVarToVar :: WantedEvVar -> EvVar
739 wantedEvVarToVar (WantedEvVar ev _) = ev
741 wantedEvVarPred :: WantedEvVar -> PredType
742 wantedEvVarPred (WantedEvVar ev _) = evVarPred ev
744 splitWanteds :: WantedConstraints -> (Bag WantedEvVar, Bag Implication)
745 splitWanteds wanted = partitionBagWith pick wanted
747 pick (WcEvVar v) = Left v
748 pick (WcImplic i) = Right i
751 Note [Skolems in an implication]
752 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
753 The skolems in an implication are not there to perform a skolem escape
754 check. That happens because all the environment variables are in the
755 untouchables, and therefore cannot be unified with anything at all,
756 let alone the skolems.
758 Instead, ic_skols is used only when considering floating a constraint
759 outside the implication in TcSimplify.floatEqualities or
760 TcSimplify.approximateImplications
762 Note [Scoped pattern variables]
763 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
764 data T where K :: forall a,b. a -> b -> T
766 ...(case x of K (p::c) (q::d) -> ...)...
768 We create fresh MetaTvs for c,d, and later check that they are
769 bound bijectively to the skolems we created for a,b. So the
770 implication constraint looks like
771 ic_skols = {a',b'} -- Skolem tvs created from a,b
772 ic_scoped = {c',d'} -- Meta tvs created from c,d
775 emptyWanteds :: WantedConstraints
776 emptyWanteds = emptyBag
778 andWanteds :: WantedConstraints -> WantedConstraints -> WantedConstraints
779 andWanteds = unionBags
781 extendWanteds :: WantedConstraints -> WantedConstraint -> WantedConstraints
782 extendWanteds = snocBag
786 pprEvVars :: [EvVar] -> SDoc -- Print with their types
787 pprEvVars ev_vars = vcat (map pprEvVarWithType ev_vars)
789 pprEvVarTheta :: [EvVar] -> SDoc
790 pprEvVarTheta ev_vars = pprTheta (map evVarPred ev_vars)
792 pprEvVarWithType :: EvVar -> SDoc
793 pprEvVarWithType v = ppr v <+> dcolon <+> pprPred (evVarPred v)
795 pprWantedsWithLocs :: Bag WantedConstraint -> SDoc
796 pprWantedsWithLocs = foldrBag (($$) . pprWantedWithLoc) empty
798 pprWantedWithLoc :: WantedConstraint -> SDoc
799 pprWantedWithLoc (WcImplic i) = ppr i
800 pprWantedWithLoc (WcEvVar v) = pprWantedEvVarWithLoc v
802 instance Outputable WantedConstraint where
803 ppr (WcEvVar v) = ppr v
804 ppr (WcImplic i) = ppr i
806 -- Adding -ferror-spans makes the output more voluminous
807 instance Outputable WantedEvVar where
808 ppr wev | opt_ErrorSpans = pprWantedEvVarWithLoc wev
809 | otherwise = pprWantedEvVar wev
811 pprWantedEvVarWithLoc, pprWantedEvVar :: WantedEvVar -> SDoc
812 pprWantedEvVarWithLoc (WantedEvVar v loc) = hang (pprEvVarWithType v)
814 pprWantedEvVar (WantedEvVar v _) = pprEvVarWithType v
816 instance Outputable Implication where
817 ppr (Implic { ic_untch = untch, ic_skols = skols, ic_given = given
818 , ic_wanted = wanted, ic_binds = binds, ic_loc = loc })
819 = ptext (sLit "Implic") <+> braces
820 (sep [ ptext (sLit "Untouchables = ") <+> ppr untch
821 , ptext (sLit "Skolems = ") <+> ppr skols
822 , ptext (sLit "Given = ") <+> pprEvVars given
823 , ptext (sLit "Wanted = ") <+> ppr wanted
824 , ptext (sLit "Binds = ") <+> ppr binds
825 , pprSkolInfo (ctLocOrigin loc)
826 , ppr (ctLocSpan loc) ])
829 %************************************************************************
833 %************************************************************************
835 The 'CtLoc' and 'CtOrigin' types gives information about where a
836 *wanted constraint* came from. This is important for decent error
837 message reporting because dictionaries don't appear in the original
838 source code. Doubtless this type will evolve...
841 -------------------------------------------
842 data CtLoc orig = CtLoc orig SrcSpan [ErrCtxt]
844 ctLocSpan :: CtLoc o -> SrcSpan
845 ctLocSpan (CtLoc _ s _) = s
847 ctLocOrigin :: CtLoc o -> o
848 ctLocOrigin (CtLoc o _ _) = o
850 setCtLocOrigin :: CtLoc o -> o' -> CtLoc o'
851 setCtLocOrigin (CtLoc _ s c) o = CtLoc o s c
853 pprArising :: CtOrigin -> SDoc
854 pprArising (TypeEqOrigin {}) = empty
855 pprArising orig = text "arising from" <+> ppr orig
857 pprArisingAt :: CtLoc CtOrigin -> SDoc
858 pprArisingAt (CtLoc o s _) = sep [pprArising o, text "at" <+> ppr s]
860 -------------------------------------------
861 -- CtOrigin gives the origin of *wanted* constraints
863 = OccurrenceOf Name -- Occurrence of an overloaded identifier
864 | AppOrigin -- An application of some kind
866 | SpecPragOrigin Name -- Specialisation pragma for identifier
868 | TypeEqOrigin EqOrigin
870 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
872 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
873 | NegateOrigin -- Occurrence of syntactic negation
875 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
876 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
878 | TupleOrigin -- (..,..)
879 | ExprSigOrigin -- e :: ty
880 | PatSigOrigin -- p :: ty
881 | PatOrigin -- Instantiating a polytyped pattern at a constructor
885 | ScOrigin -- Typechecking superclasses of an instance declaration
886 | DerivOrigin -- Typechecking deriving
887 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
888 | DefaultOrigin -- Typechecking a default decl
889 | DoOrigin -- Arising from a do expression
890 | ProcOrigin -- Arising from a proc expression
891 | AnnOrigin -- An annotation
895 { uo_actual :: TcType
896 , uo_expected :: TcType }
898 instance Outputable CtOrigin where
901 pprO :: CtOrigin -> SDoc
902 pprO (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
903 pprO AppOrigin = ptext (sLit "an application")
904 pprO (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
905 pprO (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
906 pprO RecordUpdOrigin = ptext (sLit "a record update")
907 pprO ExprSigOrigin = ptext (sLit "an expression type signature")
908 pprO PatSigOrigin = ptext (sLit "a pattern type signature")
909 pprO PatOrigin = ptext (sLit "a pattern")
910 pprO ViewPatOrigin = ptext (sLit "a view pattern")
911 pprO (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
912 pprO (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
913 pprO (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
914 pprO SectionOrigin = ptext (sLit "an operator section")
915 pprO TupleOrigin = ptext (sLit "a tuple")
916 pprO NegateOrigin = ptext (sLit "a use of syntactic negation")
917 pprO ScOrigin = ptext (sLit "the superclasses of an instance declaration")
918 pprO DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
919 pprO StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
920 pprO DefaultOrigin = ptext (sLit "a 'default' declaration")
921 pprO DoOrigin = ptext (sLit "a do statement")
922 pprO ProcOrigin = ptext (sLit "a proc expression")
923 pprO (TypeEqOrigin eq) = ptext (sLit "an equality") <+> ppr eq
924 pprO AnnOrigin = ptext (sLit "an annotation")
926 instance Outputable EqOrigin where
927 ppr (UnifyOrigin t1 t2) = ppr t1 <+> char '~' <+> ppr t2