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)
76 %************************************************************************
78 Standard monad definition for TcRn
79 All the combinators for the monad can be found in TcRnMonad
81 %************************************************************************
83 The monad itself has to be defined here, because it is mentioned by ErrCtxt
86 type TcRef a = IORef a
87 type TcId = Id -- Type may be a TcType
89 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
91 type TcRnIf a b c = IOEnv (Env a b) c
92 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
94 type IfG a = IfM () a -- Top level
95 type IfL a = IfM IfLclEnv a -- Nested
96 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
97 type RnM a = TcRn a -- Historical
98 type TcM a = TcRn a -- Historical
101 Representation of type bindings to uninstantiated meta variables used during
105 data TcTyVarBind = TcTyVarBind TcTyVar TcType
107 type TcTyVarBinds = Bag TcTyVarBind
109 instance Outputable TcTyVarBind where
110 ppr (TcTyVarBind tv ty) = ppr tv <+> text ":=" <+> ppr ty
114 %************************************************************************
116 The main environment types
118 %************************************************************************
121 data Env gbl lcl -- Changes as we move into an expression
123 env_top :: HscEnv, -- Top-level stuff that never changes
124 -- Includes all info about imported things
126 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
127 -- Unique supply for local varibles
129 env_gbl :: gbl, -- Info about things defined at the top level
130 -- of the module being compiled
132 env_lcl :: lcl -- Nested stuff; changes as we go into
135 -- TcGblEnv describes the top-level of the module at the
136 -- point at which the typechecker is finished work.
137 -- It is this structure that is handed on to the desugarer
141 tcg_mod :: Module, -- ^ Module being compiled
142 tcg_src :: HscSource,
143 -- ^ What kind of module (regular Haskell, hs-boot, ext-core)
145 tcg_rdr_env :: GlobalRdrEnv, -- ^ Top level envt; used during renaming
146 tcg_default :: Maybe [Type],
147 -- ^ Types used for defaulting. @Nothing@ => no @default@ decl
149 tcg_fix_env :: FixityEnv, -- ^ Just for things in this module
150 tcg_field_env :: RecFieldEnv, -- ^ Just for things in this module
152 tcg_type_env :: TypeEnv,
153 -- ^ Global type env for the module we are compiling now. All
154 -- TyCons and Classes (for this module) end up in here right away,
155 -- along with their derived constructors, selectors.
157 -- (Ids defined in this module start in the local envt, though they
158 -- move to the global envt during zonking)
160 tcg_type_env_var :: TcRef TypeEnv,
161 -- Used only to initialise the interface-file
162 -- typechecker in initIfaceTcRn, so that it can see stuff
163 -- bound in this module when dealing with hi-boot recursions
164 -- Updated at intervals (e.g. after dealing with types and classes)
166 tcg_inst_env :: InstEnv,
167 -- ^ Instance envt for /home-package/ modules; Includes the dfuns in
169 tcg_fam_inst_env :: FamInstEnv, -- ^ Ditto for family instances
171 -- Now a bunch of things about this module that are simply
172 -- accumulated, but never consulted until the end.
173 -- Nevertheless, it's convenient to accumulate them along
174 -- with the rest of the info from this module.
175 tcg_exports :: [AvailInfo], -- ^ What is exported
176 tcg_imports :: ImportAvails,
177 -- ^ Information about what was imported from where, including
178 -- things bound in this module.
181 -- ^ What is defined in this module and what is used.
182 -- The latter is used to generate
184 -- (a) version tracking; no need to recompile if these things have
185 -- not changed version stamp
187 -- (b) unused-import info
189 tcg_keep :: TcRef NameSet,
190 -- ^ Locally-defined top-level names to keep alive.
192 -- "Keep alive" means give them an Exported flag, so that the
193 -- simplifier does not discard them as dead code, and so that they
194 -- are exposed in the interface file (but not to export to the
197 -- Some things, like dict-fun Ids and default-method Ids are "born"
198 -- with the Exported flag on, for exactly the above reason, but some
199 -- we only discover as we go. Specifically:
201 -- * The to/from functions for generic data types
203 -- * Top-level variables appearing free in the RHS of an orphan
206 -- * Top-level variables appearing free in a TH bracket
208 tcg_inst_uses :: TcRef NameSet,
209 -- ^ Home-package Dfuns actually used.
211 -- Used to generate version dependencies This records usages, rather
212 -- like tcg_dus, but it has to be a mutable variable so it can be
213 -- augmented when we look up an instance. These uses of dfuns are
214 -- rather like the free variables of the program, but are implicit
215 -- instead of explicit.
217 tcg_th_used :: TcRef Bool,
218 -- ^ @True@ <=> Template Haskell syntax used.
220 -- We need this so that we can generate a dependency on the Template
221 -- Haskell package, becuase the desugarer is going to emit loads of
222 -- references to TH symbols. It's rather like tcg_inst_uses; the
223 -- reference is implicit rather than explicit, so we have to zap a
226 tcg_dfun_n :: TcRef Int,
227 -- ^ Allows us to number off the names of DFuns.
229 -- It's convenient to allocate an External Name for a DFun, with
230 -- a permanently-fixed unique, just like other top-level functions
231 -- defined in this module. But that means we need a canonical
232 -- occurrence name, distinct from all other dfuns in this module,
233 -- and this name supply serves that purpose (df1, df2, etc).
235 -- The next fields accumulate the payload of the module
236 -- The binds, rules and foreign-decl fiels are collected
237 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
239 tcg_rn_imports :: Maybe [LImportDecl Name],
240 tcg_rn_exports :: Maybe [Located (IE Name)],
241 tcg_rn_decls :: Maybe (HsGroup Name),
242 -- ^ Renamed decls, maybe. @Nothing@ <=> Don't retain renamed
245 tcg_binds :: LHsBinds Id, -- Value bindings in this module
246 tcg_warns :: Warnings, -- ...Warnings and deprecations
247 tcg_anns :: [Annotation], -- ...Annotations
248 tcg_insts :: [Instance], -- ...Instances
249 tcg_fam_insts :: [FamInst], -- ...Family instances
250 tcg_rules :: [LRuleDecl Id], -- ...Rules
251 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
253 tcg_doc :: Maybe (HsDoc Name), -- ^ Maybe Haddock documentation
254 tcg_hmi :: HaddockModInfo Name, -- ^ Haddock module information
255 tcg_hpc :: AnyHpcUsage -- ^ @True@ if any part of the prog uses hpc
260 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
261 -- to the fields for that constructor
262 NameSet -- Set of all fields declared *in this module*;
263 -- used to suppress name-shadowing complaints
264 -- when using record wild cards
265 -- E.g. let fld = e in C {..}
266 -- This is used when dealing with ".." notation in record
267 -- construction and pattern matching.
268 -- The FieldEnv deals *only* with constructors defined in *this*
269 -- module. For imported modules, we get the same info from the
273 %************************************************************************
275 The interface environments
276 Used when dealing with IfaceDecls
278 %************************************************************************
283 -- The type environment for the module being compiled,
284 -- in case the interface refers back to it via a reference that
285 -- was originally a hi-boot file.
286 -- We need the module name so we can test when it's appropriate
287 -- to look in this env.
288 if_rec_types :: Maybe (Module, IfG TypeEnv)
289 -- Allows a read effect, so it can be in a mutable
290 -- variable; c.f. handling the external package type env
291 -- Nothing => interactive stuff, no loops possible
296 -- The module for the current IfaceDecl
297 -- So if we see f = \x -> x
298 -- it means M.f = \x -> x, where M is the if_mod
301 -- The field is used only for error reporting
302 -- if (say) there's a Lint error in it
304 -- Where the interface came from:
305 -- .hi file, or GHCi state, or ext core
306 -- plus which bit is currently being examined
308 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
309 if_id_env :: UniqFM Id -- Nested id binding
314 %************************************************************************
316 The local typechecker environment
318 %************************************************************************
320 The Global-Env/Local-Env story
321 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
322 During type checking, we keep in the tcg_type_env
323 * All types and classes
324 * All Ids derived from types and classes (constructors, selectors)
326 At the end of type checking, we zonk the local bindings,
327 and as we do so we add to the tcg_type_env
328 * Locally defined top-level Ids
330 Why? Because they are now Ids not TcIds. This final GlobalEnv is
331 a) fed back (via the knot) to typechecking the
332 unfoldings of interface signatures
333 b) used in the ModDetails of this module
336 data TcLclEnv -- Changes as we move inside an expression
337 -- Discarded after typecheck/rename; not passed on to desugarer
339 tcl_loc :: SrcSpan, -- Source span
340 tcl_ctxt :: ErrCtxt, -- Error context
341 tcl_errs :: TcRef Messages, -- Place to accumulate errors
343 tcl_th_ctxt :: ThStage, -- Template Haskell context
344 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
346 tcl_rdr :: LocalRdrEnv, -- Local name envt
347 -- Maintained during renaming, of course, but also during
348 -- type checking, solely so that when renaming a Template-Haskell
349 -- splice we have the right environment for the renamer.
351 -- Does *not* include global name envt; may shadow it
352 -- Includes both ordinary variables and type variables;
353 -- they are kept distinct because tyvar have a different
354 -- occurrence contructor (Name.TvOcc)
355 -- We still need the unsullied global name env so that
356 -- we can look up record field names
358 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and
359 -- TyVars defined in this module
361 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
362 -- Namely, the in-scope TyVars bound in tcl_env,
363 -- plus the tyvars mentioned in the types of Ids bound
365 -- Why mutable? see notes with tcGetGlobalTyVars
367 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
369 tcl_tybinds :: TcRef TcTyVarBinds -- Meta and coercion type variable
370 -- bindings accumulated during
371 -- constraint solving
375 {- Note [Given Insts]
377 Because of GADTs, we have to pass inwards the Insts provided by type signatures
378 and existential contexts. Consider
379 data T a where { T1 :: b -> b -> T [b] }
380 f :: Eq a => T a -> Bool
381 f (T1 x y) = [x]==[y]
383 The constructor T1 binds an existential variable 'b', and we need Eq [b].
384 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
389 ---------------------------
390 -- Template Haskell levels
391 ---------------------------
394 -- Indicates how many levels of brackets we are inside
396 -- Incremented when going inside a bracket,
397 -- decremented when going inside a splice
398 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
399 -- original "Template meta-programming for Haskell" paper
401 impLevel, topLevel :: ThLevel
402 topLevel = 1 -- Things defined at top level of this module
403 impLevel = 0 -- Imported things; they can be used inside a top level splice
407 -- g1 = $(map ...) is OK
408 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
412 = Comp ThLevel -- Ordinary compiling, usually at level topLevel but annotations use a lower level
413 | Splice ThLevel -- Inside a splice
414 | Brack ThLevel -- Inside brackets;
415 (TcRef [PendingSplice]) -- accumulate pending splices here
416 (TcRef LIE) -- and type constraints here
417 topStage, topAnnStage, topSpliceStage :: ThStage
418 topStage = Comp topLevel
419 topAnnStage = Comp (topLevel - 1)
420 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
422 ---------------------------
423 -- Arrow-notation context
424 ---------------------------
427 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
428 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
433 Here, x is not in scope in e1, but it is in scope in e2. This can get
437 proc y -> (proc z -> e1) -< e2
439 Here, x and z are in scope in e1, but y is not. We implement this by
440 recording the environment when passing a proc (using newArrowScope),
441 and returning to that (using escapeArrowScope) on the left of -< and the
447 | ArrowCtxt (Env TcGblEnv TcLclEnv)
449 -- Record the current environment (outside a proc)
450 newArrowScope :: TcM a -> TcM a
453 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
455 -- Return to the stored environment (from the enclosing proc)
456 escapeArrowScope :: TcM a -> TcM a
458 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
460 ArrowCtxt env' -> env'
462 ---------------------------
464 ---------------------------
467 = AGlobal TyThing -- Used only in the return type of a lookup
469 | ATcId { -- Ids defined in this module; may not be fully zonked
471 tct_co :: RefinementVisibility, -- Previously: Maybe HsWrapper
472 -- Nothing <=> Do not apply a GADT type refinement
473 -- I am wobbly, or have no free
475 -- Just co <=> Apply any type refinement to me,
476 -- and record it in the coercion
477 tct_type :: TcType, -- Type of (coercion applied to id)
478 tct_level :: ThLevel }
480 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
481 -- is currently refined. We only need the Name
482 -- for error-message purposes
484 | AThing TcKind -- Used temporarily, during kind checking, for the
485 -- tycons and clases in this recursive group
487 data RefinementVisibility
488 = Unrefineable -- Do not apply a GADT refinement
489 -- I have no free variables
491 | Rigid HsWrapper -- Apply any refinement to me
492 -- and record it in the coercion
494 | Wobbly -- Do not apply a GADT refinement
497 | WobblyInvisible -- Wobbly type, not available inside current
500 instance Outputable TcTyThing where -- Debugging only
501 ppr (AGlobal g) = pprTyThing g
502 ppr elt@(ATcId {}) = text "Identifier" <>
503 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
504 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
505 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
506 ppr (AThing k) = text "AThing" <+> ppr k
508 pprTcTyThingCategory :: TcTyThing -> SDoc
509 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
510 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
511 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
512 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
514 instance Outputable RefinementVisibility where
515 ppr Unrefineable = ptext (sLit "unrefineable")
516 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
517 ppr Wobbly = ptext (sLit "wobbly")
518 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
523 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
524 -- Innermost first. Monadic so that we have a chance
525 -- to deal with bound type variables just before error
526 -- message construction
530 %************************************************************************
532 Operations over ImportAvails
534 %************************************************************************
537 -- | 'ImportAvails' summarises what was imported from where, irrespective of
538 -- whether the imported things are actually used or not. It is used:
540 -- * when processing the export list,
542 -- * when constructing usage info for the interface file,
544 -- * to identify the list of directly imported modules for initialisation
545 -- purposes and for optimised overlap checking of family instances,
547 -- * when figuring out what things are really unused
551 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
552 -- ^ Domain is all directly-imported modules
553 -- The 'ModuleName' is what the module was imported as, e.g. in
561 -- - @True@ => import was @import Foo ()@
563 -- - @False@ => import was some other form
567 -- (a) to help construct the usage information in the interface
568 -- file; if we import somethign we need to recompile if the
569 -- export version changes
571 -- (b) to specify what child modules to initialise
573 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
574 -- because we might be importing modules of the same name from
575 -- different packages. (currently not the case, but might be in the
578 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
579 -- ^ Home-package modules needed by the module being compiled
581 -- It doesn't matter whether any of these dependencies
582 -- are actually /used/ when compiling the module; they
583 -- are listed if they are below it at all. For
584 -- example, suppose M imports A which imports X. Then
585 -- compiling M might not need to consult X.hi, but X
586 -- is still listed in M's dependencies.
588 imp_dep_pkgs :: [PackageId],
589 -- ^ Packages needed by the module being compiled, whether directly,
590 -- or via other modules in this package, or via modules imported
591 -- from other packages.
593 imp_orphs :: [Module],
594 -- ^ Orphan modules below us in the import tree (and maybe including
595 -- us for imported modules)
597 imp_finsts :: [Module]
598 -- ^ Family instance modules below us in the import tree (and maybe
599 -- including us for imported modules)
602 mkModDeps :: [(ModuleName, IsBootInterface)]
603 -> ModuleNameEnv (ModuleName, IsBootInterface)
604 mkModDeps deps = foldl add emptyUFM deps
606 add env elt@(m,_) = addToUFM env m elt
608 emptyImportAvails :: ImportAvails
609 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
610 imp_dep_mods = emptyUFM,
615 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
617 (ImportAvails { imp_mods = mods1,
618 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
619 imp_orphs = orphs1, imp_finsts = finsts1 })
620 (ImportAvails { imp_mods = mods2,
621 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
622 imp_orphs = orphs2, imp_finsts = finsts2 })
623 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
624 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
625 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
626 imp_orphs = orphs1 `unionLists` orphs2,
627 imp_finsts = finsts1 `unionLists` finsts2 }
629 plus_mod_dep (m1, boot1) (m2, boot2)
630 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
631 -- Check mod-names match
632 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
635 %************************************************************************
637 \subsection{Where from}
639 %************************************************************************
641 The @WhereFrom@ type controls where the renamer looks for an interface file
645 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
646 | ImportBySystem -- Non user import.
648 instance Outputable WhereFrom where
649 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
651 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
655 %************************************************************************
657 \subsection[Inst-types]{@Inst@ types}
659 v%************************************************************************
661 An @Inst@ is either a dictionary, an instance of an overloaded
662 literal, or an instance of an overloaded value. We call the latter a
663 ``method'' even though it may not correspond to a class operation.
664 For example, we might have an instance of the @double@ function at
665 type Int, represented by
667 Method 34 doubleId [Int] origin
669 In addition to the basic Haskell variants of 'Inst's, they can now also
670 represent implication constraints 'forall tvs. given => wanted'
671 and equality constraints 'co :: ty1 ~ ty2'.
673 NB: Equalities occur in two flavours:
675 (1) Dict {tci_pred = EqPred ty1 ty2}
676 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
678 The former arises from equalities in contexts, whereas the latter is used
679 whenever the type checker introduces an equality (e.g., during deferring
682 I am not convinced that this duplication is necessary or useful! -=chak
688 tci_pred :: TcPredType, -- Class or implicit parameter only
692 | ImplicInst { -- An implication constraint
693 -- forall tvs. given => wanted
695 tci_tyvars :: [TcTyVar], -- Quantified type variables
696 tci_given :: [Inst], -- Only Dicts and EqInsts
697 -- (no Methods, LitInsts, ImplicInsts)
698 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
699 -- (no Methods or LitInsts)
703 -- NB: the tci_given are not necessarily rigid
706 tci_id :: TcId, -- The Id for the Inst
708 tci_oid :: TcId, -- The overloaded function
709 -- This function will be a global, local, or ClassOpId;
710 -- inside instance decls (only) it can also be an InstId!
711 -- The id needn't be completely polymorphic.
712 -- You'll probably find its name (for documentation purposes)
713 -- inside the InstOrigin
715 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
716 -- should be instantiated.
717 -- These types must saturate the Id's foralls.
719 tci_theta :: TcThetaType,
720 -- The (types of the) dictionaries to which the function
721 -- must be applied to get the method
725 -- INVARIANT 1: in (Method m f tys theta tau loc)
726 -- type of m = type of (f tys dicts(from theta))
728 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
729 -- Reason: two methods are considered equal if the
730 -- base Id matches, and the instantiating types
731 -- match. The TcThetaType should then match too.
732 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
736 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
737 -- INVARIANT: never a rebindable-syntax literal
738 -- Reason: tcSyntaxName does unification, and we
739 -- don't want to deal with that during tcSimplify,
740 -- when resolving LitInsts
742 tci_ty :: TcType, -- The type at which the literal is used
746 | EqInst { -- delayed unification of the form
748 tci_left :: TcType, -- ty1 -- both types are...
749 tci_right :: TcType, -- ty2 -- ...free of boxes
750 tci_co :: EqInstCo, -- co
753 tci_name :: Name -- Debugging help only: this makes it easier to
754 -- follow where a constraint is used in a morass
755 -- of trace messages! Unlike other Insts, it
756 -- has no semantic significance whatsoever.
759 type EqInstCo = Either -- Distinguish between given and wanted coercions
760 TcTyVar -- - a wanted equation, with a hole, to be filled
761 -- with a witness for the equality; for equation
762 -- arising from deferring unification, 'ty1' is
763 -- the actual and 'ty2' the expected type
764 Coercion -- - a given equation, with a coercion witnessing
765 -- the equality; a coercion that originates
766 -- from a signature or a GADT is a CoVar, but
767 -- after normalisation of coercions, they can
768 -- be arbitrary Coercions involving constructors
769 -- and pseudo-constructors like sym and trans.
772 @Insts@ are ordered by their class/type info, rather than by their
773 unique. This allows the context-reduction mechanism to use standard finite
774 maps to do their stuff. It's horrible that this code is here, rather
775 than with the Avails handling stuff in TcSimplify
778 instance Ord Inst where
780 -- Used *only* for AvailEnv in TcSimplify
782 instance Eq Inst where
783 (==) i1 i2 = case i1 `cmpInst` i2 of
787 cmpInst :: Inst -> Inst -> Ordering
788 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
789 cmpInst (Dict {}) _ = LT
791 cmpInst (Method {}) (Dict {}) = GT
792 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
793 (tci_tys m1 `tcCmpTypes` tci_tys m2)
794 cmpInst (Method {}) _ = LT
796 cmpInst (LitInst {}) (Dict {}) = GT
797 cmpInst (LitInst {}) (Method {}) = GT
798 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
799 (tci_ty l1 `tcCmpType` tci_ty l2)
800 cmpInst (LitInst {}) _ = LT
802 -- Implication constraints are compared by *name*
803 -- not by type; that is, we make no attempt to do CSE on them
804 cmpInst (ImplicInst {}) (Dict {}) = GT
805 cmpInst (ImplicInst {}) (Method {}) = GT
806 cmpInst (ImplicInst {}) (LitInst {}) = GT
807 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
808 cmpInst (ImplicInst {}) _ = LT
810 -- same for Equality constraints
811 cmpInst (EqInst {}) (Dict {}) = GT
812 cmpInst (EqInst {}) (Method {}) = GT
813 cmpInst (EqInst {}) (LitInst {}) = GT
814 cmpInst (EqInst {}) (ImplicInst {}) = GT
815 cmpInst i1@(EqInst {}) i2@(EqInst {}) = (tci_left i1 `tcCmpType` tci_left i2) `thenCmp`
816 (tci_right i1 `tcCmpType` tci_right i2)
820 %************************************************************************
822 \subsection[Inst-collections]{LIE: a collection of Insts}
824 %************************************************************************
827 -- FIXME: Rename this. It clashes with (Located (IE ...))
830 isEmptyLIE :: LIE -> Bool
831 isEmptyLIE = isEmptyBag
836 unitLIE :: Inst -> LIE
837 unitLIE inst = unitBag inst
839 mkLIE :: [Inst] -> LIE
840 mkLIE insts = listToBag insts
842 plusLIE :: LIE -> LIE -> LIE
843 plusLIE lie1 lie2 = lie1 `unionBags` lie2
845 plusLIEs :: [LIE] -> LIE
846 plusLIEs lies = unionManyBags lies
848 lieToList :: LIE -> [Inst]
849 lieToList = bagToList
851 listToLIE :: [Inst] -> LIE
852 listToLIE = listToBag
854 consLIE :: Inst -> LIE -> LIE
855 consLIE inst lie = lie `snocBag` inst
856 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
857 -- to ensure that we tend to report the *leftmost* type-constraint error
860 -- we'd like to complain about the '1', not the '3'.
862 -- "Half-hearted" because the rest of the type checker makes no great
863 -- claims for retaining order in the constraint set. Still, this
864 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
868 %************************************************************************
870 \subsection[Inst-origin]{The @InstOrigin@ type}
872 %************************************************************************
874 The @InstOrigin@ type gives information about where a dictionary came from.
875 This is important for decent error message reporting because dictionaries
876 don't appear in the original source code. Doubtless this type will evolve...
878 It appears in TcMonad because there are a couple of error-message-generation
879 functions that deal with it.
882 -------------------------------------------
883 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
885 instLoc :: Inst -> InstLoc
886 instLoc inst = tci_loc inst
888 setInstLoc :: Inst -> InstLoc -> Inst
889 setInstLoc inst new_loc = inst { tci_loc = new_loc }
891 instSpan :: Inst -> SrcSpan
892 instSpan wanted = instLocSpan (instLoc wanted)
894 instLocSpan :: InstLoc -> SrcSpan
895 instLocSpan (InstLoc _ s _) = s
897 instLocOrigin :: InstLoc -> InstOrigin
898 instLocOrigin (InstLoc o _ _) = o
900 pprInstArising :: Inst -> SDoc
901 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
903 pprInstLoc :: InstLoc -> SDoc
904 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
906 -------------------------------------------
908 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
909 -- Places that bind type variables and introduce
910 -- available constraints
912 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
914 -------------------------------------------------------
915 -- The rest are all occurrences: Insts that are 'wanted'
916 -------------------------------------------------------
917 | OccurrenceOf Name -- Occurrence of an overloaded identifier
918 | SpecPragOrigin Name -- Specialisation pragma for identifier
920 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
922 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
923 | NegateOrigin -- Occurrence of syntactic negation
925 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
926 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
927 | TupleOrigin -- (..,..)
929 | InstSigOrigin -- A dict occurrence arising from instantiating
930 -- a polymorphic type during a subsumption check
932 | ExprSigOrigin -- e :: ty
936 | InstScOrigin -- Typechecking superclasses of an instance declaration
938 | NoScOrigin -- A very special hack; see TcSimplify,
939 -- Note [Recursive instances and superclases]
942 | DerivOrigin -- Typechecking deriving
943 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
944 | DefaultOrigin -- Typechecking a default decl
945 | DoOrigin -- Arising from a do expression
946 | ProcOrigin -- Arising from a proc expression
947 | ImplicOrigin SDoc -- An implication constraint
948 | EqOrigin -- A type equality
949 | AnnOrigin -- An annotation
951 instance Outputable InstOrigin where
952 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
953 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
954 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
955 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
956 ppr RecordUpdOrigin = ptext (sLit "a record update")
957 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
958 ppr ViewPatOrigin = ptext (sLit "a view pattern")
959 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
960 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
961 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
962 ppr TupleOrigin = ptext (sLit "a tuple")
963 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
964 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
965 ppr NoScOrigin = ptext (sLit "an instance declaration")
966 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
967 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
968 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
969 ppr DoOrigin = ptext (sLit "a do statement")
970 ppr ProcOrigin = ptext (sLit "a proc expression")
971 ppr (ImplicOrigin doc) = doc
972 ppr (SigOrigin info) = pprSkolInfo info
973 ppr EqOrigin = ptext (sLit "a type equality")
974 ppr InstSigOrigin = panic "ppr InstSigOrigin"
975 ppr AnnOrigin = ptext (sLit "an annotation")