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)
75 %************************************************************************
77 Standard monad definition for TcRn
78 All the combinators for the monad can be found in TcRnMonad
80 %************************************************************************
82 The monad itself has to be defined here, because it is mentioned by ErrCtxt
85 type TcRef a = IORef a
86 type TcId = Id -- Type may be a TcType
88 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
90 type TcRnIf a b c = IOEnv (Env a b) c
91 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
93 type IfG a = IfM () a -- Top level
94 type IfL a = IfM IfLclEnv a -- Nested
95 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
96 type RnM a = TcRn a -- Historical
97 type TcM a = TcRn a -- Historical
100 Representation of type bindings to uninstantiated meta variables used during
104 data TcTyVarBind = TcTyVarBind TcTyVar TcType
106 type TcTyVarBinds = Bag TcTyVarBind
108 instance Outputable TcTyVarBind where
109 ppr (TcTyVarBind tv ty) = ppr tv <+> text ":=" <+> ppr ty
113 %************************************************************************
115 The main environment types
117 %************************************************************************
120 data Env gbl lcl -- Changes as we move into an expression
122 env_top :: HscEnv, -- Top-level stuff that never changes
123 -- Includes all info about imported things
125 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
126 -- Unique supply for local varibles
128 env_gbl :: gbl, -- Info about things defined at the top level
129 -- of the module being compiled
131 env_lcl :: lcl -- Nested stuff; changes as we go into
134 -- TcGblEnv describes the top-level of the module at the
135 -- point at which the typechecker is finished work.
136 -- It is this structure that is handed on to the desugarer
140 tcg_mod :: Module, -- ^ Module being compiled
141 tcg_src :: HscSource,
142 -- ^ What kind of module (regular Haskell, hs-boot, ext-core)
144 tcg_rdr_env :: GlobalRdrEnv, -- ^ Top level envt; used during renaming
145 tcg_default :: Maybe [Type],
146 -- ^ Types used for defaulting. @Nothing@ => no @default@ decl
148 tcg_fix_env :: FixityEnv, -- ^ Just for things in this module
149 tcg_field_env :: RecFieldEnv, -- ^ Just for things in this module
151 tcg_type_env :: TypeEnv,
152 -- ^ Global type env for the module we are compiling now. All
153 -- TyCons and Classes (for this module) end up in here right away,
154 -- along with their derived constructors, selectors.
156 -- (Ids defined in this module start in the local envt, though they
157 -- move to the global envt during zonking)
159 tcg_type_env_var :: TcRef TypeEnv,
160 -- Used only to initialise the interface-file
161 -- typechecker in initIfaceTcRn, so that it can see stuff
162 -- bound in this module when dealing with hi-boot recursions
163 -- Updated at intervals (e.g. after dealing with types and classes)
165 tcg_inst_env :: InstEnv,
166 -- ^ Instance envt for /home-package/ modules; Includes the dfuns in
168 tcg_fam_inst_env :: FamInstEnv, -- ^ Ditto for family instances
170 -- Now a bunch of things about this module that are simply
171 -- accumulated, but never consulted until the end.
172 -- Nevertheless, it's convenient to accumulate them along
173 -- with the rest of the info from this module.
174 tcg_exports :: [AvailInfo], -- ^ What is exported
175 tcg_imports :: ImportAvails,
176 -- ^ Information about what was imported from where, including
177 -- things bound in this module.
180 -- ^ What is defined in this module and what is used.
181 -- The latter is used to generate
183 -- (a) version tracking; no need to recompile if these things have
184 -- not changed version stamp
186 -- (b) unused-import info
188 tcg_keep :: TcRef NameSet,
189 -- ^ Locally-defined top-level names to keep alive.
191 -- "Keep alive" means give them an Exported flag, so that the
192 -- simplifier does not discard them as dead code, and so that they
193 -- are exposed in the interface file (but not to export to the
196 -- Some things, like dict-fun Ids and default-method Ids are "born"
197 -- with the Exported flag on, for exactly the above reason, but some
198 -- we only discover as we go. Specifically:
200 -- * The to/from functions for generic data types
202 -- * Top-level variables appearing free in the RHS of an orphan
205 -- * Top-level variables appearing free in a TH bracket
207 tcg_inst_uses :: TcRef NameSet,
208 -- ^ Home-package Dfuns actually used.
210 -- Used to generate version dependencies This records usages, rather
211 -- like tcg_dus, but it has to be a mutable variable so it can be
212 -- augmented when we look up an instance. These uses of dfuns are
213 -- rather like the free variables of the program, but are implicit
214 -- instead of explicit.
216 tcg_th_used :: TcRef Bool,
217 -- ^ @True@ <=> Template Haskell syntax used.
219 -- We need this so that we can generate a dependency on the Template
220 -- Haskell package, becuase the desugarer is going to emit loads of
221 -- references to TH symbols. It's rather like tcg_inst_uses; the
222 -- reference is implicit rather than explicit, so we have to zap a
225 tcg_dfun_n :: TcRef OccSet,
226 -- ^ Allows us to choose unique DFun names.
228 -- The next fields accumulate the payload of the module
229 -- The binds, rules and foreign-decl fiels are collected
230 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
232 tcg_rn_exports :: Maybe [Located (IE Name)],
233 tcg_rn_imports :: [LImportDecl Name],
234 -- Keep the renamed imports regardless. They are not
235 -- voluminous and are needed if you want to report unused imports
236 tcg_used_rdrnames :: TcRef (Set RdrName),
237 tcg_rn_decls :: Maybe (HsGroup Name),
238 -- ^ Renamed decls, maybe. @Nothing@ <=> Don't retain renamed
241 tcg_binds :: LHsBinds Id, -- Value bindings in this module
242 tcg_warns :: Warnings, -- ...Warnings and deprecations
243 tcg_anns :: [Annotation], -- ...Annotations
244 tcg_insts :: [Instance], -- ...Instances
245 tcg_fam_insts :: [FamInst], -- ...Family instances
246 tcg_rules :: [LRuleDecl Id], -- ...Rules
247 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
249 tcg_doc :: Maybe (HsDoc Name), -- ^ Maybe Haddock documentation
250 tcg_hmi :: HaddockModInfo Name, -- ^ Haddock module information
251 tcg_hpc :: AnyHpcUsage -- ^ @True@ if any part of the prog uses hpc
256 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
257 -- to the fields for that constructor
258 NameSet -- Set of all fields declared *in this module*;
259 -- used to suppress name-shadowing complaints
260 -- when using record wild cards
261 -- E.g. let fld = e in C {..}
262 -- This is used when dealing with ".." notation in record
263 -- construction and pattern matching.
264 -- The FieldEnv deals *only* with constructors defined in *this*
265 -- module. For imported modules, we get the same info from the
269 %************************************************************************
271 The interface environments
272 Used when dealing with IfaceDecls
274 %************************************************************************
279 -- The type environment for the module being compiled,
280 -- in case the interface refers back to it via a reference that
281 -- was originally a hi-boot file.
282 -- We need the module name so we can test when it's appropriate
283 -- to look in this env.
284 if_rec_types :: Maybe (Module, IfG TypeEnv)
285 -- Allows a read effect, so it can be in a mutable
286 -- variable; c.f. handling the external package type env
287 -- Nothing => interactive stuff, no loops possible
292 -- The module for the current IfaceDecl
293 -- So if we see f = \x -> x
294 -- it means M.f = \x -> x, where M is the if_mod
297 -- The field is used only for error reporting
298 -- if (say) there's a Lint error in it
300 -- Where the interface came from:
301 -- .hi file, or GHCi state, or ext core
302 -- plus which bit is currently being examined
304 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
305 if_id_env :: UniqFM Id -- Nested id binding
310 %************************************************************************
312 The local typechecker environment
314 %************************************************************************
316 The Global-Env/Local-Env story
317 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
318 During type checking, we keep in the tcg_type_env
319 * All types and classes
320 * All Ids derived from types and classes (constructors, selectors)
322 At the end of type checking, we zonk the local bindings,
323 and as we do so we add to the tcg_type_env
324 * Locally defined top-level Ids
326 Why? Because they are now Ids not TcIds. This final GlobalEnv is
327 a) fed back (via the knot) to typechecking the
328 unfoldings of interface signatures
329 b) used in the ModDetails of this module
332 data TcLclEnv -- Changes as we move inside an expression
333 -- Discarded after typecheck/rename; not passed on to desugarer
335 tcl_loc :: SrcSpan, -- Source span
336 tcl_ctxt :: [ErrCtxt], -- Error context, innermost on top
337 tcl_errs :: TcRef Messages, -- Place to accumulate errors
339 tcl_th_ctxt :: ThStage, -- Template Haskell context
340 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
342 tcl_rdr :: LocalRdrEnv, -- Local name envt
343 -- Maintained during renaming, of course, but also during
344 -- type checking, solely so that when renaming a Template-Haskell
345 -- splice we have the right environment for the renamer.
347 -- Does *not* include global name envt; may shadow it
348 -- Includes both ordinary variables and type variables;
349 -- they are kept distinct because tyvar have a different
350 -- occurrence contructor (Name.TvOcc)
351 -- We still need the unsullied global name env so that
352 -- we can look up record field names
354 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and
355 -- TyVars defined in this module
357 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
358 -- Namely, the in-scope TyVars bound in tcl_env,
359 -- plus the tyvars mentioned in the types of Ids bound
361 -- Why mutable? see notes with tcGetGlobalTyVars
363 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
365 tcl_tybinds :: TcRef TcTyVarBinds -- Meta and coercion type variable
366 -- bindings accumulated during
367 -- constraint solving
371 {- Note [Given Insts]
373 Because of GADTs, we have to pass inwards the Insts provided by type signatures
374 and existential contexts. Consider
375 data T a where { T1 :: b -> b -> T [b] }
376 f :: Eq a => T a -> Bool
377 f (T1 x y) = [x]==[y]
379 The constructor T1 binds an existential variable 'b', and we need Eq [b].
380 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
385 ---------------------------
386 -- Template Haskell levels
387 ---------------------------
390 -- Indicates how many levels of brackets we are inside
392 -- Incremented when going inside a bracket,
393 -- decremented when going inside a splice
394 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
395 -- original "Template meta-programming for Haskell" paper
397 impLevel, topLevel :: ThLevel
398 topLevel = 1 -- Things defined at top level of this module
399 impLevel = 0 -- Imported things; they can be used inside a top level splice
403 -- g1 = $(map ...) is OK
404 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
408 = Comp ThLevel -- Ordinary compiling, usually at level topLevel but annotations use a lower level
409 | Splice ThLevel -- Inside a splice
410 | Brack ThLevel -- Inside brackets;
411 (TcRef [PendingSplice]) -- accumulate pending splices here
412 (TcRef LIE) -- and type constraints here
413 topStage, topAnnStage, topSpliceStage :: ThStage
414 topStage = Comp topLevel
415 topAnnStage = Comp (topLevel - 1)
416 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
418 ---------------------------
419 -- Arrow-notation context
420 ---------------------------
423 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
424 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
429 Here, x is not in scope in e1, but it is in scope in e2. This can get
433 proc y -> (proc z -> e1) -< e2
435 Here, x and z are in scope in e1, but y is not. We implement this by
436 recording the environment when passing a proc (using newArrowScope),
437 and returning to that (using escapeArrowScope) on the left of -< and the
443 | ArrowCtxt (Env TcGblEnv TcLclEnv)
445 -- Record the current environment (outside a proc)
446 newArrowScope :: TcM a -> TcM a
449 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
451 -- Return to the stored environment (from the enclosing proc)
452 escapeArrowScope :: TcM a -> TcM a
454 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
456 ArrowCtxt env' -> env'
458 ---------------------------
460 ---------------------------
463 = AGlobal TyThing -- Used only in the return type of a lookup
465 | ATcId { -- Ids defined in this module; may not be fully zonked
467 tct_co :: RefinementVisibility, -- Previously: Maybe HsWrapper
468 -- Nothing <=> Do not apply a GADT type refinement
469 -- I am wobbly, or have no free
471 -- Just co <=> Apply any type refinement to me,
472 -- and record it in the coercion
473 tct_type :: TcType, -- Type of (coercion applied to id)
474 tct_level :: ThLevel }
476 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
477 -- is currently refined. We only need the Name
478 -- for error-message purposes
480 | AThing TcKind -- Used temporarily, during kind checking, for the
481 -- tycons and clases in this recursive group
483 data RefinementVisibility
484 = Unrefineable -- Do not apply a GADT refinement
485 -- I have no free variables
487 | Rigid HsWrapper -- Apply any refinement to me
488 -- and record it in the coercion
490 | Wobbly -- Do not apply a GADT refinement
493 | WobblyInvisible -- Wobbly type, not available inside current
496 instance Outputable TcTyThing where -- Debugging only
497 ppr (AGlobal g) = pprTyThing g
498 ppr elt@(ATcId {}) = text "Identifier" <>
499 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
500 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
501 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
502 ppr (AThing k) = text "AThing" <+> ppr k
504 pprTcTyThingCategory :: TcTyThing -> SDoc
505 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
506 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
507 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
508 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
510 instance Outputable RefinementVisibility where
511 ppr Unrefineable = ptext (sLit "unrefineable")
512 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
513 ppr Wobbly = ptext (sLit "wobbly")
514 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
519 type ErrCtxt = (Bool, TidyEnv -> TcM (TidyEnv, Message))
520 -- Monadic so that we have a chance
521 -- to deal with bound type variables just before error
522 -- message construction
524 -- Bool: True <=> this is a landmark context; do not
525 -- discard it when trimming for display
529 %************************************************************************
531 Operations over ImportAvails
533 %************************************************************************
536 -- | 'ImportAvails' summarises what was imported from where, irrespective of
537 -- whether the imported things are actually used or not. It is used:
539 -- * when processing the export list,
541 -- * when constructing usage info for the interface file,
543 -- * to identify the list of directly imported modules for initialisation
544 -- purposes and for optimised overlap checking of family instances,
546 -- * when figuring out what things are really unused
550 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
551 -- ^ Domain is all directly-imported modules
552 -- The 'ModuleName' is what the module was imported as, e.g. in
560 -- - @True@ => import was @import Foo ()@
562 -- - @False@ => import was some other form
566 -- (a) to help construct the usage information in the interface
567 -- file; if we import somethign we need to recompile if the
568 -- export version changes
570 -- (b) to specify what child modules to initialise
572 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
573 -- because we might be importing modules of the same name from
574 -- different packages. (currently not the case, but might be in the
577 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
578 -- ^ Home-package modules needed by the module being compiled
580 -- It doesn't matter whether any of these dependencies
581 -- are actually /used/ when compiling the module; they
582 -- are listed if they are below it at all. For
583 -- example, suppose M imports A which imports X. Then
584 -- compiling M might not need to consult X.hi, but X
585 -- is still listed in M's dependencies.
587 imp_dep_pkgs :: [PackageId],
588 -- ^ Packages needed by the module being compiled, whether directly,
589 -- or via other modules in this package, or via modules imported
590 -- from other packages.
592 imp_orphs :: [Module],
593 -- ^ Orphan modules below us in the import tree (and maybe including
594 -- us for imported modules)
596 imp_finsts :: [Module]
597 -- ^ Family instance modules below us in the import tree (and maybe
598 -- including us for imported modules)
601 mkModDeps :: [(ModuleName, IsBootInterface)]
602 -> ModuleNameEnv (ModuleName, IsBootInterface)
603 mkModDeps deps = foldl add emptyUFM deps
605 add env elt@(m,_) = addToUFM env m elt
607 emptyImportAvails :: ImportAvails
608 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
609 imp_dep_mods = emptyUFM,
614 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
616 (ImportAvails { imp_mods = mods1,
617 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
618 imp_orphs = orphs1, imp_finsts = finsts1 })
619 (ImportAvails { imp_mods = mods2,
620 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
621 imp_orphs = orphs2, imp_finsts = finsts2 })
622 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
623 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
624 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
625 imp_orphs = orphs1 `unionLists` orphs2,
626 imp_finsts = finsts1 `unionLists` finsts2 }
628 plus_mod_dep (m1, boot1) (m2, boot2)
629 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
630 -- Check mod-names match
631 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
634 %************************************************************************
636 \subsection{Where from}
638 %************************************************************************
640 The @WhereFrom@ type controls where the renamer looks for an interface file
644 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
645 | ImportBySystem -- Non user import.
647 instance Outputable WhereFrom where
648 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
650 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
654 %************************************************************************
656 \subsection[Inst-types]{@Inst@ types}
658 v%************************************************************************
660 An @Inst@ is either a dictionary, an instance of an overloaded
661 literal, or an instance of an overloaded value. We call the latter a
662 ``method'' even though it may not correspond to a class operation.
663 For example, we might have an instance of the @double@ function at
664 type Int, represented by
666 Method 34 doubleId [Int] origin
668 In addition to the basic Haskell variants of 'Inst's, they can now also
669 represent implication constraints 'forall tvs. given => wanted'
670 and equality constraints 'co :: ty1 ~ ty2'.
672 NB: Equalities occur in two flavours:
674 (1) Dict {tci_pred = EqPred ty1 ty2}
675 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
677 The former arises from equalities in contexts, whereas the latter is used
678 whenever the type checker introduces an equality (e.g., during deferring
681 I am not convinced that this duplication is necessary or useful! -=chak
687 tci_pred :: TcPredType, -- Class or implicit parameter only
691 | ImplicInst { -- An implication constraint
692 -- forall tvs. given => wanted
694 tci_tyvars :: [TcTyVar], -- Quantified type variables
695 tci_given :: [Inst], -- Only Dicts and EqInsts
696 -- (no Methods, LitInsts, ImplicInsts)
697 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
698 -- (no Methods or LitInsts)
702 -- NB: the tci_given are not necessarily rigid
705 tci_id :: TcId, -- The Id for the Inst
707 tci_oid :: TcId, -- The overloaded function
708 -- This function will be a global, local, or ClassOpId;
709 -- inside instance decls (only) it can also be an InstId!
710 -- The id needn't be completely polymorphic.
711 -- You'll probably find its name (for documentation purposes)
712 -- inside the InstOrigin
714 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
715 -- should be instantiated.
716 -- These types must saturate the Id's foralls.
718 tci_theta :: TcThetaType,
719 -- The (types of the) dictionaries to which the function
720 -- must be applied to get the method
724 -- INVARIANT 1: in (Method m f tys theta tau loc)
725 -- type of m = type of (f tys dicts(from theta))
727 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
728 -- Reason: two methods are considered equal if the
729 -- base Id matches, and the instantiating types
730 -- match. The TcThetaType should then match too.
731 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
735 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
736 -- INVARIANT: never a rebindable-syntax literal
737 -- Reason: tcSyntaxName does unification, and we
738 -- don't want to deal with that during tcSimplify,
739 -- when resolving LitInsts
741 tci_ty :: TcType, -- The type at which the literal is used
745 | EqInst { -- delayed unification of the form
747 tci_left :: TcType, -- ty1 -- both types are...
748 tci_right :: TcType, -- ty2 -- ...free of boxes
749 tci_co :: EqInstCo, -- co
752 tci_name :: Name -- Debugging help only: this makes it easier to
753 -- follow where a constraint is used in a morass
754 -- of trace messages! Unlike other Insts, it
755 -- has no semantic significance whatsoever.
758 type EqInstCo = Either -- Distinguish between given and wanted coercions
759 TcTyVar -- - a wanted equation, with a hole, to be filled
760 -- with a witness for the equality; for equation
761 -- arising from deferring unification, 'ty1' is
762 -- the actual and 'ty2' the expected type
763 Coercion -- - a given equation, with a coercion witnessing
764 -- the equality; a coercion that originates
765 -- from a signature or a GADT is a CoVar, but
766 -- after normalisation of coercions, they can
767 -- be arbitrary Coercions involving constructors
768 -- and pseudo-constructors like sym and trans.
771 @Insts@ are ordered by their class/type info, rather than by their
772 unique. This allows the context-reduction mechanism to use standard finite
773 maps to do their stuff. It's horrible that this code is here, rather
774 than with the Avails handling stuff in TcSimplify
777 instance Ord Inst where
779 -- Used *only* for AvailEnv in TcSimplify
781 instance Eq Inst where
782 (==) i1 i2 = case i1 `cmpInst` i2 of
786 cmpInst :: Inst -> Inst -> Ordering
787 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
788 cmpInst (Dict {}) _ = LT
790 cmpInst (Method {}) (Dict {}) = GT
791 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
792 (tci_tys m1 `tcCmpTypes` tci_tys m2)
793 cmpInst (Method {}) _ = LT
795 cmpInst (LitInst {}) (Dict {}) = GT
796 cmpInst (LitInst {}) (Method {}) = GT
797 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
798 (tci_ty l1 `tcCmpType` tci_ty l2)
799 cmpInst (LitInst {}) _ = LT
801 -- Implication constraints are compared by *name*
802 -- not by type; that is, we make no attempt to do CSE on them
803 cmpInst (ImplicInst {}) (Dict {}) = GT
804 cmpInst (ImplicInst {}) (Method {}) = GT
805 cmpInst (ImplicInst {}) (LitInst {}) = GT
806 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
807 cmpInst (ImplicInst {}) _ = LT
809 -- same for Equality constraints
810 cmpInst (EqInst {}) (Dict {}) = GT
811 cmpInst (EqInst {}) (Method {}) = GT
812 cmpInst (EqInst {}) (LitInst {}) = GT
813 cmpInst (EqInst {}) (ImplicInst {}) = GT
814 cmpInst i1@(EqInst {}) i2@(EqInst {}) = (tci_left i1 `tcCmpType` tci_left i2) `thenCmp`
815 (tci_right i1 `tcCmpType` tci_right i2)
819 %************************************************************************
821 \subsection[Inst-collections]{LIE: a collection of Insts}
823 %************************************************************************
826 -- FIXME: Rename this. It clashes with (Located (IE ...))
829 isEmptyLIE :: LIE -> Bool
830 isEmptyLIE = isEmptyBag
835 unitLIE :: Inst -> LIE
836 unitLIE inst = unitBag inst
838 mkLIE :: [Inst] -> LIE
839 mkLIE insts = listToBag insts
841 plusLIE :: LIE -> LIE -> LIE
842 plusLIE lie1 lie2 = lie1 `unionBags` lie2
844 plusLIEs :: [LIE] -> LIE
845 plusLIEs lies = unionManyBags lies
847 lieToList :: LIE -> [Inst]
848 lieToList = bagToList
850 listToLIE :: [Inst] -> LIE
851 listToLIE = listToBag
853 consLIE :: Inst -> LIE -> LIE
854 consLIE inst lie = lie `snocBag` inst
855 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
856 -- to ensure that we tend to report the *leftmost* type-constraint error
859 -- we'd like to complain about the '1', not the '3'.
861 -- "Half-hearted" because the rest of the type checker makes no great
862 -- claims for retaining order in the constraint set. Still, this
863 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
867 %************************************************************************
869 \subsection[Inst-origin]{The @InstOrigin@ type}
871 %************************************************************************
873 The @InstOrigin@ type gives information about where a dictionary came from.
874 This is important for decent error message reporting because dictionaries
875 don't appear in the original source code. Doubtless this type will evolve...
877 It appears in TcMonad because there are a couple of error-message-generation
878 functions that deal with it.
881 -------------------------------------------
882 data InstLoc = InstLoc InstOrigin SrcSpan [ErrCtxt]
884 instLoc :: Inst -> InstLoc
885 instLoc inst = tci_loc inst
887 setInstLoc :: Inst -> InstLoc -> Inst
888 setInstLoc inst new_loc = inst { tci_loc = new_loc }
890 instSpan :: Inst -> SrcSpan
891 instSpan wanted = instLocSpan (instLoc wanted)
893 instLocSpan :: InstLoc -> SrcSpan
894 instLocSpan (InstLoc _ s _) = s
896 instLocOrigin :: InstLoc -> InstOrigin
897 instLocOrigin (InstLoc o _ _) = o
899 pprInstArising :: Inst -> SDoc
900 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
902 pprInstLoc :: InstLoc -> SDoc
903 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
905 -------------------------------------------
907 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
908 -- Places that bind type variables and introduce
909 -- available constraints
911 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
913 -------------------------------------------------------
914 -- The rest are all occurrences: Insts that are 'wanted'
915 -------------------------------------------------------
916 | OccurrenceOf Name -- Occurrence of an overloaded identifier
917 | SpecPragOrigin Name -- Specialisation pragma for identifier
919 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
921 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
922 | NegateOrigin -- Occurrence of syntactic negation
924 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
925 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
926 | TupleOrigin -- (..,..)
928 | InstSigOrigin -- A dict occurrence arising from instantiating
929 -- a polymorphic type during a subsumption check
931 | ExprSigOrigin -- e :: ty
935 | InstScOrigin -- Typechecking superclasses of an instance declaration
937 | NoScOrigin -- A very special hack; see TcSimplify,
938 -- Note [Recursive instances and superclases]
941 | DerivOrigin -- Typechecking deriving
942 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
943 | DefaultOrigin -- Typechecking a default decl
944 | DoOrigin -- Arising from a do expression
945 | ProcOrigin -- Arising from a proc expression
946 | ImplicOrigin SDoc -- An implication constraint
947 | EqOrigin -- A type equality
948 | AnnOrigin -- An annotation
950 instance Outputable InstOrigin where
951 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
952 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
953 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
954 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
955 ppr RecordUpdOrigin = ptext (sLit "a record update")
956 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
957 ppr ViewPatOrigin = ptext (sLit "a view pattern")
958 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
959 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
960 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
961 ppr TupleOrigin = ptext (sLit "a tuple")
962 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
963 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
964 ppr NoScOrigin = ptext (sLit "an instance declaration")
965 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
966 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
967 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
968 ppr DoOrigin = ptext (sLit "a do statement")
969 ppr ProcOrigin = ptext (sLit "a proc expression")
970 ppr (ImplicOrigin doc) = doc
971 ppr (SigOrigin info) = pprSkolInfo info
972 ppr EqOrigin = ptext (sLit "a type equality")
973 ppr InstSigOrigin = panic "ppr InstSigOrigin"
974 ppr AnnOrigin = ptext (sLit "an annotation")