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 TcTyThing(..), pprTcTyThingCategory, RefinementVisibility(..),
24 ThStage(..), topStage, topAnnStage, topSpliceStage,
25 ThLevel, impLevel, topLevel,
28 ArrowCtxt(NoArrowCtxt), newArrowScope, escapeArrowScope,
31 Inst(..), EqInstCo, InstOrigin(..), InstLoc(..),
32 pprInstLoc, pprInstArising, instLocSpan, instLocOrigin, setInstLoc,
33 LIE, emptyLIE, unitLIE, plusLIE, consLIE, instLoc, instSpan,
34 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
37 TcId, TcIdSet, TcDictBinds, TcTyVarBind(..), TcTyVarBinds
41 #include "HsVersions.h"
43 import HsSyn hiding (LIE)
77 %************************************************************************
79 Standard monad definition for TcRn
80 All the combinators for the monad can be found in TcRnMonad
82 %************************************************************************
84 The monad itself has to be defined here, because it is mentioned by ErrCtxt
87 type TcRef a = IORef a
88 type TcId = Id -- Type may be a TcType
90 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
92 type TcRnIf a b c = IOEnv (Env a b) c
93 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
95 type IfG a = IfM () a -- Top level
96 type IfL a = IfM IfLclEnv a -- Nested
97 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
98 type RnM a = TcRn a -- Historical
99 type TcM a = TcRn a -- Historical
102 Representation of type bindings to uninstantiated meta variables used during
106 data TcTyVarBind = TcTyVarBind TcTyVar TcType
108 type TcTyVarBinds = Bag TcTyVarBind
110 instance Outputable TcTyVarBind where
111 ppr (TcTyVarBind tv ty) = ppr tv <+> text ":=" <+> ppr ty
115 %************************************************************************
117 The main environment types
119 %************************************************************************
122 data Env gbl lcl -- Changes as we move into an expression
124 env_top :: HscEnv, -- Top-level stuff that never changes
125 -- Includes all info about imported things
127 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
128 -- Unique supply for local varibles
130 env_gbl :: gbl, -- Info about things defined at the top level
131 -- of the module being compiled
133 env_lcl :: lcl -- Nested stuff; changes as we go into
136 -- TcGblEnv describes the top-level of the module at the
137 -- point at which the typechecker is finished work.
138 -- It is this structure that is handed on to the desugarer
142 tcg_mod :: Module, -- ^ Module being compiled
143 tcg_src :: HscSource,
144 -- ^ What kind of module (regular Haskell, hs-boot, ext-core)
146 tcg_rdr_env :: GlobalRdrEnv, -- ^ Top level envt; used during renaming
147 tcg_default :: Maybe [Type],
148 -- ^ Types used for defaulting. @Nothing@ => no @default@ decl
150 tcg_fix_env :: FixityEnv, -- ^ Just for things in this module
151 tcg_field_env :: RecFieldEnv, -- ^ Just for things in this module
153 tcg_type_env :: TypeEnv,
154 -- ^ Global type env for the module we are compiling now. All
155 -- TyCons and Classes (for this module) end up in here right away,
156 -- along with their derived constructors, selectors.
158 -- (Ids defined in this module start in the local envt, though they
159 -- move to the global envt during zonking)
161 tcg_type_env_var :: TcRef TypeEnv,
162 -- Used only to initialise the interface-file
163 -- typechecker in initIfaceTcRn, so that it can see stuff
164 -- bound in this module when dealing with hi-boot recursions
165 -- Updated at intervals (e.g. after dealing with types and classes)
167 tcg_inst_env :: InstEnv,
168 -- ^ Instance envt for /home-package/ modules; Includes the dfuns in
170 tcg_fam_inst_env :: FamInstEnv, -- ^ Ditto for family instances
172 -- Now a bunch of things about this module that are simply
173 -- accumulated, but never consulted until the end.
174 -- Nevertheless, it's convenient to accumulate them along
175 -- with the rest of the info from this module.
176 tcg_exports :: [AvailInfo], -- ^ What is exported
177 tcg_imports :: ImportAvails,
178 -- ^ Information about what was imported from where, including
179 -- things bound in this module.
182 -- ^ What is defined in this module and what is used.
183 -- The latter is used to generate
185 -- (a) version tracking; no need to recompile if these things have
186 -- not changed version stamp
188 -- (b) unused-import info
190 tcg_keep :: TcRef NameSet,
191 -- ^ Locally-defined top-level names to keep alive.
193 -- "Keep alive" means give them an Exported flag, so that the
194 -- simplifier does not discard them as dead code, and so that they
195 -- are exposed in the interface file (but not to export to the
198 -- Some things, like dict-fun Ids and default-method Ids are "born"
199 -- with the Exported flag on, for exactly the above reason, but some
200 -- we only discover as we go. Specifically:
202 -- * The to/from functions for generic data types
204 -- * Top-level variables appearing free in the RHS of an orphan
207 -- * Top-level variables appearing free in a TH bracket
209 tcg_inst_uses :: TcRef NameSet,
210 -- ^ Home-package Dfuns actually used.
212 -- Used to generate version dependencies This records usages, rather
213 -- like tcg_dus, but it has to be a mutable variable so it can be
214 -- augmented when we look up an instance. These uses of dfuns are
215 -- rather like the free variables of the program, but are implicit
216 -- instead of explicit.
218 tcg_th_used :: TcRef Bool,
219 -- ^ @True@ <=> Template Haskell syntax used.
221 -- We need this so that we can generate a dependency on the Template
222 -- Haskell package, becuase the desugarer is going to emit loads of
223 -- references to TH symbols. It's rather like tcg_inst_uses; the
224 -- reference is implicit rather than explicit, so we have to zap a
227 tcg_dfun_n :: TcRef Int,
228 -- ^ Allows us to number off the names of DFuns.
230 -- It's convenient to allocate an External Name for a DFun, with
231 -- a permanently-fixed unique, just like other top-level functions
232 -- defined in this module. But that means we need a canonical
233 -- occurrence name, distinct from all other dfuns in this module,
234 -- and this name supply serves that purpose (df1, df2, etc).
236 -- The next fields accumulate the payload of the module
237 -- The binds, rules and foreign-decl fiels are collected
238 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
240 tcg_rn_exports :: Maybe [Located (IE Name)],
241 tcg_rn_imports :: [LImportDecl Name],
242 -- Keep the renamed imports regardless. They are not
243 -- voluminous and are needed if you want to report unused imports
244 tcg_used_rdrnames :: TcRef (Set RdrName),
245 tcg_rn_decls :: Maybe (HsGroup Name),
246 -- ^ Renamed decls, maybe. @Nothing@ <=> Don't retain renamed
249 tcg_binds :: LHsBinds Id, -- Value bindings in this module
250 tcg_warns :: Warnings, -- ...Warnings and deprecations
251 tcg_anns :: [Annotation], -- ...Annotations
252 tcg_insts :: [Instance], -- ...Instances
253 tcg_fam_insts :: [FamInst], -- ...Family instances
254 tcg_rules :: [LRuleDecl Id], -- ...Rules
255 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
257 tcg_doc :: Maybe (HsDoc Name), -- ^ Maybe Haddock documentation
258 tcg_hmi :: HaddockModInfo Name, -- ^ Haddock module information
259 tcg_hpc :: AnyHpcUsage -- ^ @True@ if any part of the prog uses hpc
264 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
265 -- to the fields for that constructor
266 NameSet -- Set of all fields declared *in this module*;
267 -- used to suppress name-shadowing complaints
268 -- when using record wild cards
269 -- E.g. let fld = e in C {..}
270 -- This is used when dealing with ".." notation in record
271 -- construction and pattern matching.
272 -- The FieldEnv deals *only* with constructors defined in *this*
273 -- module. For imported modules, we get the same info from the
277 %************************************************************************
279 The interface environments
280 Used when dealing with IfaceDecls
282 %************************************************************************
287 -- The type environment for the module being compiled,
288 -- in case the interface refers back to it via a reference that
289 -- was originally a hi-boot file.
290 -- We need the module name so we can test when it's appropriate
291 -- to look in this env.
292 if_rec_types :: Maybe (Module, IfG TypeEnv)
293 -- Allows a read effect, so it can be in a mutable
294 -- variable; c.f. handling the external package type env
295 -- Nothing => interactive stuff, no loops possible
300 -- The module for the current IfaceDecl
301 -- So if we see f = \x -> x
302 -- it means M.f = \x -> x, where M is the if_mod
305 -- The field is used only for error reporting
306 -- if (say) there's a Lint error in it
308 -- Where the interface came from:
309 -- .hi file, or GHCi state, or ext core
310 -- plus which bit is currently being examined
312 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
313 if_id_env :: UniqFM Id -- Nested id binding
318 %************************************************************************
320 The local typechecker environment
322 %************************************************************************
324 The Global-Env/Local-Env story
325 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
326 During type checking, we keep in the tcg_type_env
327 * All types and classes
328 * All Ids derived from types and classes (constructors, selectors)
330 At the end of type checking, we zonk the local bindings,
331 and as we do so we add to the tcg_type_env
332 * Locally defined top-level Ids
334 Why? Because they are now Ids not TcIds. This final GlobalEnv is
335 a) fed back (via the knot) to typechecking the
336 unfoldings of interface signatures
337 b) used in the ModDetails of this module
340 data TcLclEnv -- Changes as we move inside an expression
341 -- Discarded after typecheck/rename; not passed on to desugarer
343 tcl_loc :: SrcSpan, -- Source span
344 tcl_ctxt :: ErrCtxt, -- Error context
345 tcl_errs :: TcRef Messages, -- Place to accumulate errors
347 tcl_th_ctxt :: ThStage, -- Template Haskell context
348 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
350 tcl_rdr :: LocalRdrEnv, -- Local name envt
351 -- Maintained during renaming, of course, but also during
352 -- type checking, solely so that when renaming a Template-Haskell
353 -- splice we have the right environment for the renamer.
355 -- Does *not* include global name envt; may shadow it
356 -- Includes both ordinary variables and type variables;
357 -- they are kept distinct because tyvar have a different
358 -- occurrence contructor (Name.TvOcc)
359 -- We still need the unsullied global name env so that
360 -- we can look up record field names
362 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and
363 -- TyVars defined in this module
365 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
366 -- Namely, the in-scope TyVars bound in tcl_env,
367 -- plus the tyvars mentioned in the types of Ids bound
369 -- Why mutable? see notes with tcGetGlobalTyVars
371 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
373 tcl_tybinds :: TcRef TcTyVarBinds -- Meta and coercion type variable
374 -- bindings accumulated during
375 -- constraint solving
379 {- Note [Given Insts]
381 Because of GADTs, we have to pass inwards the Insts provided by type signatures
382 and existential contexts. Consider
383 data T a where { T1 :: b -> b -> T [b] }
384 f :: Eq a => T a -> Bool
385 f (T1 x y) = [x]==[y]
387 The constructor T1 binds an existential variable 'b', and we need Eq [b].
388 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
393 ---------------------------
394 -- Template Haskell levels
395 ---------------------------
398 -- Indicates how many levels of brackets we are inside
400 -- Incremented when going inside a bracket,
401 -- decremented when going inside a splice
402 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
403 -- original "Template meta-programming for Haskell" paper
405 impLevel, topLevel :: ThLevel
406 topLevel = 1 -- Things defined at top level of this module
407 impLevel = 0 -- Imported things; they can be used inside a top level splice
411 -- g1 = $(map ...) is OK
412 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
416 = Comp ThLevel -- Ordinary compiling, usually at level topLevel but annotations use a lower level
417 | Splice ThLevel -- Inside a splice
418 | Brack ThLevel -- Inside brackets;
419 (TcRef [PendingSplice]) -- accumulate pending splices here
420 (TcRef LIE) -- and type constraints here
421 topStage, topAnnStage, topSpliceStage :: ThStage
422 topStage = Comp topLevel
423 topAnnStage = Comp (topLevel - 1)
424 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
426 ---------------------------
427 -- Arrow-notation context
428 ---------------------------
431 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
432 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
437 Here, x is not in scope in e1, but it is in scope in e2. This can get
441 proc y -> (proc z -> e1) -< e2
443 Here, x and z are in scope in e1, but y is not. We implement this by
444 recording the environment when passing a proc (using newArrowScope),
445 and returning to that (using escapeArrowScope) on the left of -< and the
451 | ArrowCtxt (Env TcGblEnv TcLclEnv)
453 -- Record the current environment (outside a proc)
454 newArrowScope :: TcM a -> TcM a
457 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
459 -- Return to the stored environment (from the enclosing proc)
460 escapeArrowScope :: TcM a -> TcM a
462 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
464 ArrowCtxt env' -> env'
466 ---------------------------
468 ---------------------------
471 = AGlobal TyThing -- Used only in the return type of a lookup
473 | ATcId { -- Ids defined in this module; may not be fully zonked
475 tct_co :: RefinementVisibility, -- Previously: Maybe HsWrapper
476 -- Nothing <=> Do not apply a GADT type refinement
477 -- I am wobbly, or have no free
479 -- Just co <=> Apply any type refinement to me,
480 -- and record it in the coercion
481 tct_type :: TcType, -- Type of (coercion applied to id)
482 tct_level :: ThLevel }
484 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
485 -- is currently refined. We only need the Name
486 -- for error-message purposes
488 | AThing TcKind -- Used temporarily, during kind checking, for the
489 -- tycons and clases in this recursive group
491 data RefinementVisibility
492 = Unrefineable -- Do not apply a GADT refinement
493 -- I have no free variables
495 | Rigid HsWrapper -- Apply any refinement to me
496 -- and record it in the coercion
498 | Wobbly -- Do not apply a GADT refinement
501 | WobblyInvisible -- Wobbly type, not available inside current
504 instance Outputable TcTyThing where -- Debugging only
505 ppr (AGlobal g) = pprTyThing g
506 ppr elt@(ATcId {}) = text "Identifier" <>
507 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
508 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
509 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
510 ppr (AThing k) = text "AThing" <+> ppr k
512 pprTcTyThingCategory :: TcTyThing -> SDoc
513 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
514 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
515 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
516 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
518 instance Outputable RefinementVisibility where
519 ppr Unrefineable = ptext (sLit "unrefineable")
520 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
521 ppr Wobbly = ptext (sLit "wobbly")
522 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
527 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
528 -- Innermost first. Monadic so that we have a chance
529 -- to deal with bound type variables just before error
530 -- message construction
534 %************************************************************************
536 Operations over ImportAvails
538 %************************************************************************
541 -- | 'ImportAvails' summarises what was imported from where, irrespective of
542 -- whether the imported things are actually used or not. It is used:
544 -- * when processing the export list,
546 -- * when constructing usage info for the interface file,
548 -- * to identify the list of directly imported modules for initialisation
549 -- purposes and for optimised overlap checking of family instances,
551 -- * when figuring out what things are really unused
555 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
556 -- ^ Domain is all directly-imported modules
557 -- The 'ModuleName' is what the module was imported as, e.g. in
565 -- - @True@ => import was @import Foo ()@
567 -- - @False@ => import was some other form
571 -- (a) to help construct the usage information in the interface
572 -- file; if we import somethign we need to recompile if the
573 -- export version changes
575 -- (b) to specify what child modules to initialise
577 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
578 -- because we might be importing modules of the same name from
579 -- different packages. (currently not the case, but might be in the
582 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
583 -- ^ Home-package modules needed by the module being compiled
585 -- It doesn't matter whether any of these dependencies
586 -- are actually /used/ when compiling the module; they
587 -- are listed if they are below it at all. For
588 -- example, suppose M imports A which imports X. Then
589 -- compiling M might not need to consult X.hi, but X
590 -- is still listed in M's dependencies.
592 imp_dep_pkgs :: [PackageId],
593 -- ^ Packages needed by the module being compiled, whether directly,
594 -- or via other modules in this package, or via modules imported
595 -- from other packages.
597 imp_orphs :: [Module],
598 -- ^ Orphan modules below us in the import tree (and maybe including
599 -- us for imported modules)
601 imp_finsts :: [Module]
602 -- ^ Family instance modules below us in the import tree (and maybe
603 -- including us for imported modules)
606 mkModDeps :: [(ModuleName, IsBootInterface)]
607 -> ModuleNameEnv (ModuleName, IsBootInterface)
608 mkModDeps deps = foldl add emptyUFM deps
610 add env elt@(m,_) = addToUFM env m elt
612 emptyImportAvails :: ImportAvails
613 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
614 imp_dep_mods = emptyUFM,
619 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
621 (ImportAvails { imp_mods = mods1,
622 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
623 imp_orphs = orphs1, imp_finsts = finsts1 })
624 (ImportAvails { imp_mods = mods2,
625 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
626 imp_orphs = orphs2, imp_finsts = finsts2 })
627 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
628 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
629 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
630 imp_orphs = orphs1 `unionLists` orphs2,
631 imp_finsts = finsts1 `unionLists` finsts2 }
633 plus_mod_dep (m1, boot1) (m2, boot2)
634 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
635 -- Check mod-names match
636 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
639 %************************************************************************
641 \subsection{Where from}
643 %************************************************************************
645 The @WhereFrom@ type controls where the renamer looks for an interface file
649 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
650 | ImportBySystem -- Non user import.
652 instance Outputable WhereFrom where
653 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
655 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
659 %************************************************************************
661 \subsection[Inst-types]{@Inst@ types}
663 v%************************************************************************
665 An @Inst@ is either a dictionary, an instance of an overloaded
666 literal, or an instance of an overloaded value. We call the latter a
667 ``method'' even though it may not correspond to a class operation.
668 For example, we might have an instance of the @double@ function at
669 type Int, represented by
671 Method 34 doubleId [Int] origin
673 In addition to the basic Haskell variants of 'Inst's, they can now also
674 represent implication constraints 'forall tvs. given => wanted'
675 and equality constraints 'co :: ty1 ~ ty2'.
677 NB: Equalities occur in two flavours:
679 (1) Dict {tci_pred = EqPred ty1 ty2}
680 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
682 The former arises from equalities in contexts, whereas the latter is used
683 whenever the type checker introduces an equality (e.g., during deferring
686 I am not convinced that this duplication is necessary or useful! -=chak
692 tci_pred :: TcPredType, -- Class or implicit parameter only
696 | ImplicInst { -- An implication constraint
697 -- forall tvs. given => wanted
699 tci_tyvars :: [TcTyVar], -- Quantified type variables
700 tci_given :: [Inst], -- Only Dicts and EqInsts
701 -- (no Methods, LitInsts, ImplicInsts)
702 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
703 -- (no Methods or LitInsts)
707 -- NB: the tci_given are not necessarily rigid
710 tci_id :: TcId, -- The Id for the Inst
712 tci_oid :: TcId, -- The overloaded function
713 -- This function will be a global, local, or ClassOpId;
714 -- inside instance decls (only) it can also be an InstId!
715 -- The id needn't be completely polymorphic.
716 -- You'll probably find its name (for documentation purposes)
717 -- inside the InstOrigin
719 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
720 -- should be instantiated.
721 -- These types must saturate the Id's foralls.
723 tci_theta :: TcThetaType,
724 -- The (types of the) dictionaries to which the function
725 -- must be applied to get the method
729 -- INVARIANT 1: in (Method m f tys theta tau loc)
730 -- type of m = type of (f tys dicts(from theta))
732 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
733 -- Reason: two methods are considered equal if the
734 -- base Id matches, and the instantiating types
735 -- match. The TcThetaType should then match too.
736 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
740 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
741 -- INVARIANT: never a rebindable-syntax literal
742 -- Reason: tcSyntaxName does unification, and we
743 -- don't want to deal with that during tcSimplify,
744 -- when resolving LitInsts
746 tci_ty :: TcType, -- The type at which the literal is used
750 | EqInst { -- delayed unification of the form
752 tci_left :: TcType, -- ty1 -- both types are...
753 tci_right :: TcType, -- ty2 -- ...free of boxes
754 tci_co :: EqInstCo, -- co
757 tci_name :: Name -- Debugging help only: this makes it easier to
758 -- follow where a constraint is used in a morass
759 -- of trace messages! Unlike other Insts, it
760 -- has no semantic significance whatsoever.
763 type EqInstCo = Either -- Distinguish between given and wanted coercions
764 TcTyVar -- - a wanted equation, with a hole, to be filled
765 -- with a witness for the equality; for equation
766 -- arising from deferring unification, 'ty1' is
767 -- the actual and 'ty2' the expected type
768 Coercion -- - a given equation, with a coercion witnessing
769 -- the equality; a coercion that originates
770 -- from a signature or a GADT is a CoVar, but
771 -- after normalisation of coercions, they can
772 -- be arbitrary Coercions involving constructors
773 -- and pseudo-constructors like sym and trans.
776 @Insts@ are ordered by their class/type info, rather than by their
777 unique. This allows the context-reduction mechanism to use standard finite
778 maps to do their stuff. It's horrible that this code is here, rather
779 than with the Avails handling stuff in TcSimplify
782 instance Ord Inst where
784 -- Used *only* for AvailEnv in TcSimplify
786 instance Eq Inst where
787 (==) i1 i2 = case i1 `cmpInst` i2 of
791 cmpInst :: Inst -> Inst -> Ordering
792 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
793 cmpInst (Dict {}) _ = LT
795 cmpInst (Method {}) (Dict {}) = GT
796 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
797 (tci_tys m1 `tcCmpTypes` tci_tys m2)
798 cmpInst (Method {}) _ = LT
800 cmpInst (LitInst {}) (Dict {}) = GT
801 cmpInst (LitInst {}) (Method {}) = GT
802 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
803 (tci_ty l1 `tcCmpType` tci_ty l2)
804 cmpInst (LitInst {}) _ = LT
806 -- Implication constraints are compared by *name*
807 -- not by type; that is, we make no attempt to do CSE on them
808 cmpInst (ImplicInst {}) (Dict {}) = GT
809 cmpInst (ImplicInst {}) (Method {}) = GT
810 cmpInst (ImplicInst {}) (LitInst {}) = GT
811 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
812 cmpInst (ImplicInst {}) _ = LT
814 -- same for Equality constraints
815 cmpInst (EqInst {}) (Dict {}) = GT
816 cmpInst (EqInst {}) (Method {}) = GT
817 cmpInst (EqInst {}) (LitInst {}) = GT
818 cmpInst (EqInst {}) (ImplicInst {}) = GT
819 cmpInst i1@(EqInst {}) i2@(EqInst {}) = (tci_left i1 `tcCmpType` tci_left i2) `thenCmp`
820 (tci_right i1 `tcCmpType` tci_right i2)
824 %************************************************************************
826 \subsection[Inst-collections]{LIE: a collection of Insts}
828 %************************************************************************
831 -- FIXME: Rename this. It clashes with (Located (IE ...))
834 isEmptyLIE :: LIE -> Bool
835 isEmptyLIE = isEmptyBag
840 unitLIE :: Inst -> LIE
841 unitLIE inst = unitBag inst
843 mkLIE :: [Inst] -> LIE
844 mkLIE insts = listToBag insts
846 plusLIE :: LIE -> LIE -> LIE
847 plusLIE lie1 lie2 = lie1 `unionBags` lie2
849 plusLIEs :: [LIE] -> LIE
850 plusLIEs lies = unionManyBags lies
852 lieToList :: LIE -> [Inst]
853 lieToList = bagToList
855 listToLIE :: [Inst] -> LIE
856 listToLIE = listToBag
858 consLIE :: Inst -> LIE -> LIE
859 consLIE inst lie = lie `snocBag` inst
860 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
861 -- to ensure that we tend to report the *leftmost* type-constraint error
864 -- we'd like to complain about the '1', not the '3'.
866 -- "Half-hearted" because the rest of the type checker makes no great
867 -- claims for retaining order in the constraint set. Still, this
868 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
872 %************************************************************************
874 \subsection[Inst-origin]{The @InstOrigin@ type}
876 %************************************************************************
878 The @InstOrigin@ type gives information about where a dictionary came from.
879 This is important for decent error message reporting because dictionaries
880 don't appear in the original source code. Doubtless this type will evolve...
882 It appears in TcMonad because there are a couple of error-message-generation
883 functions that deal with it.
886 -------------------------------------------
887 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
889 instLoc :: Inst -> InstLoc
890 instLoc inst = tci_loc inst
892 setInstLoc :: Inst -> InstLoc -> Inst
893 setInstLoc inst new_loc = inst { tci_loc = new_loc }
895 instSpan :: Inst -> SrcSpan
896 instSpan wanted = instLocSpan (instLoc wanted)
898 instLocSpan :: InstLoc -> SrcSpan
899 instLocSpan (InstLoc _ s _) = s
901 instLocOrigin :: InstLoc -> InstOrigin
902 instLocOrigin (InstLoc o _ _) = o
904 pprInstArising :: Inst -> SDoc
905 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
907 pprInstLoc :: InstLoc -> SDoc
908 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
910 -------------------------------------------
912 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
913 -- Places that bind type variables and introduce
914 -- available constraints
916 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
918 -------------------------------------------------------
919 -- The rest are all occurrences: Insts that are 'wanted'
920 -------------------------------------------------------
921 | OccurrenceOf Name -- Occurrence of an overloaded identifier
922 | SpecPragOrigin Name -- Specialisation pragma for identifier
924 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
926 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
927 | NegateOrigin -- Occurrence of syntactic negation
929 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
930 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
931 | TupleOrigin -- (..,..)
933 | InstSigOrigin -- A dict occurrence arising from instantiating
934 -- a polymorphic type during a subsumption check
936 | ExprSigOrigin -- e :: ty
940 | InstScOrigin -- Typechecking superclasses of an instance declaration
942 | NoScOrigin -- A very special hack; see TcSimplify,
943 -- Note [Recursive instances and superclases]
946 | DerivOrigin -- Typechecking deriving
947 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
948 | DefaultOrigin -- Typechecking a default decl
949 | DoOrigin -- Arising from a do expression
950 | ProcOrigin -- Arising from a proc expression
951 | ImplicOrigin SDoc -- An implication constraint
952 | EqOrigin -- A type equality
953 | AnnOrigin -- An annotation
955 instance Outputable InstOrigin where
956 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
957 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
958 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
959 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
960 ppr RecordUpdOrigin = ptext (sLit "a record update")
961 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
962 ppr ViewPatOrigin = ptext (sLit "a view pattern")
963 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
964 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
965 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
966 ppr TupleOrigin = ptext (sLit "a tuple")
967 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
968 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
969 ppr NoScOrigin = ptext (sLit "an instance declaration")
970 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
971 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
972 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
973 ppr DoOrigin = ptext (sLit "a do statement")
974 ppr ProcOrigin = ptext (sLit "a proc expression")
975 ppr (ImplicOrigin doc) = doc
976 ppr (SigOrigin info) = pprSkolInfo info
977 ppr EqOrigin = ptext (sLit "a type equality")
978 ppr InstSigOrigin = panic "ppr InstSigOrigin"
979 ppr AnnOrigin = ptext (sLit "an annotation")