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,
33 LIE, emptyLIE, unitLIE, plusLIE, consLIE, instLoc, instSpan,
34 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
37 TcId, TcIdSet, TcDictBinds,
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
102 %************************************************************************
104 The main environment types
106 %************************************************************************
109 data Env gbl lcl -- Changes as we move into an expression
111 env_top :: HscEnv, -- Top-level stuff that never changes
112 -- Includes all info about imported things
114 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
115 -- Unique supply for local varibles
117 env_gbl :: gbl, -- Info about things defined at the top level
118 -- of the module being compiled
120 env_lcl :: lcl -- Nested stuff; changes as we go into
123 -- TcGblEnv describes the top-level of the module at the
124 -- point at which the typechecker is finished work.
125 -- It is this structure that is handed on to the desugarer
129 tcg_mod :: Module, -- ^ Module being compiled
130 tcg_src :: HscSource,
131 -- ^ What kind of module (regular Haskell, hs-boot, ext-core)
133 tcg_rdr_env :: GlobalRdrEnv, -- ^ Top level envt; used during renaming
134 tcg_default :: Maybe [Type],
135 -- ^ Types used for defaulting. @Nothing@ => no @default@ decl
137 tcg_fix_env :: FixityEnv, -- ^ Just for things in this module
138 tcg_field_env :: RecFieldEnv, -- ^ Just for things in this module
140 tcg_type_env :: TypeEnv,
141 -- ^ Global type env for the module we are compiling now. All
142 -- TyCons and Classes (for this module) end up in here right away,
143 -- along with their derived constructors, selectors.
145 -- (Ids defined in this module start in the local envt, though they
146 -- move to the global envt during zonking)
148 tcg_type_env_var :: TcRef TypeEnv,
149 -- Used only to initialise the interface-file
150 -- typechecker in initIfaceTcRn, so that it can see stuff
151 -- bound in this module when dealing with hi-boot recursions
152 -- Updated at intervals (e.g. after dealing with types and classes)
154 tcg_inst_env :: InstEnv,
155 -- ^ Instance envt for /home-package/ modules; Includes the dfuns in
157 tcg_fam_inst_env :: FamInstEnv, -- ^ Ditto for family instances
159 -- Now a bunch of things about this module that are simply
160 -- accumulated, but never consulted until the end.
161 -- Nevertheless, it's convenient to accumulate them along
162 -- with the rest of the info from this module.
163 tcg_exports :: [AvailInfo], -- ^ What is exported
164 tcg_imports :: ImportAvails,
165 -- ^ Information about what was imported from where, including
166 -- things bound in this module.
169 -- ^ What is defined in this module and what is used.
170 -- The latter is used to generate
172 -- (a) version tracking; no need to recompile if these things have
173 -- not changed version stamp
175 -- (b) unused-import info
177 tcg_keep :: TcRef NameSet,
178 -- ^ Locally-defined top-level names to keep alive.
180 -- "Keep alive" means give them an Exported flag, so that the
181 -- simplifier does not discard them as dead code, and so that they
182 -- are exposed in the interface file (but not to export to the
185 -- Some things, like dict-fun Ids and default-method Ids are "born"
186 -- with the Exported flag on, for exactly the above reason, but some
187 -- we only discover as we go. Specifically:
189 -- * The to/from functions for generic data types
191 -- * Top-level variables appearing free in the RHS of an orphan
194 -- * Top-level variables appearing free in a TH bracket
196 tcg_inst_uses :: TcRef NameSet,
197 -- ^ Home-package Dfuns actually used.
199 -- Used to generate version dependencies This records usages, rather
200 -- like tcg_dus, but it has to be a mutable variable so it can be
201 -- augmented when we look up an instance. These uses of dfuns are
202 -- rather like the free variables of the program, but are implicit
203 -- instead of explicit.
205 tcg_th_used :: TcRef Bool,
206 -- ^ @True@ <=> Template Haskell syntax used.
208 -- We need this so that we can generate a dependency on the Template
209 -- Haskell package, becuase the desugarer is going to emit loads of
210 -- references to TH symbols. It's rather like tcg_inst_uses; the
211 -- reference is implicit rather than explicit, so we have to zap a
214 tcg_dfun_n :: TcRef Int,
215 -- ^ Allows us to number off the names of DFuns.
217 -- It's convenient to allocate an External Name for a DFun, with
218 -- a permanently-fixed unique, just like other top-level functions
219 -- defined in this module. But that means we need a canonical
220 -- occurrence name, distinct from all other dfuns in this module,
221 -- and this name supply serves that purpose (df1, df2, etc).
223 -- The next fields accumulate the payload of the module
224 -- The binds, rules and foreign-decl fiels are collected
225 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
227 tcg_rn_imports :: Maybe [LImportDecl Name],
228 tcg_rn_exports :: Maybe [Located (IE Name)],
229 tcg_rn_decls :: Maybe (HsGroup Name),
230 -- ^ Renamed decls, maybe. @Nothing@ <=> Don't retain renamed
233 tcg_binds :: LHsBinds Id, -- Value bindings in this module
234 tcg_warns :: Warnings, -- ...Warnings and deprecations
235 tcg_anns :: [Annotation], -- ...Annotations
236 tcg_insts :: [Instance], -- ...Instances
237 tcg_fam_insts :: [FamInst], -- ...Family instances
238 tcg_rules :: [LRuleDecl Id], -- ...Rules
239 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
241 tcg_doc :: Maybe (HsDoc Name), -- ^ Maybe Haddock documentation
242 tcg_hmi :: HaddockModInfo Name, -- ^ Haddock module information
243 tcg_hpc :: AnyHpcUsage -- ^ @True@ if any part of the prog uses hpc
248 = RecFields (NameEnv [Name]) -- Maps a constructor name *in this module*
249 -- to the fields for that constructor
250 NameSet -- Set of all fields declared *in this module*;
251 -- used to suppress name-shadowing complaints
252 -- when using record wild cards
253 -- E.g. let fld = e in C {..}
254 -- This is used when dealing with ".." notation in record
255 -- construction and pattern matching.
256 -- The FieldEnv deals *only* with constructors defined in *this*
257 -- module. For imported modules, we get the same info from the
261 %************************************************************************
263 The interface environments
264 Used when dealing with IfaceDecls
266 %************************************************************************
271 -- The type environment for the module being compiled,
272 -- in case the interface refers back to it via a reference that
273 -- was originally a hi-boot file.
274 -- We need the module name so we can test when it's appropriate
275 -- to look in this env.
276 if_rec_types :: Maybe (Module, IfG TypeEnv)
277 -- Allows a read effect, so it can be in a mutable
278 -- variable; c.f. handling the external package type env
279 -- Nothing => interactive stuff, no loops possible
284 -- The module for the current IfaceDecl
285 -- So if we see f = \x -> x
286 -- it means M.f = \x -> x, where M is the if_mod
289 -- The field is used only for error reporting
290 -- if (say) there's a Lint error in it
292 -- Where the interface came from:
293 -- .hi file, or GHCi state, or ext core
294 -- plus which bit is currently being examined
296 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
297 if_id_env :: UniqFM Id -- Nested id binding
302 %************************************************************************
304 The local typechecker environment
306 %************************************************************************
308 The Global-Env/Local-Env story
309 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
310 During type checking, we keep in the tcg_type_env
311 * All types and classes
312 * All Ids derived from types and classes (constructors, selectors)
314 At the end of type checking, we zonk the local bindings,
315 and as we do so we add to the tcg_type_env
316 * Locally defined top-level Ids
318 Why? Because they are now Ids not TcIds. This final GlobalEnv is
319 a) fed back (via the knot) to typechecking the
320 unfoldings of interface signatures
321 b) used in the ModDetails of this module
324 data TcLclEnv -- Changes as we move inside an expression
325 -- Discarded after typecheck/rename; not passed on to desugarer
327 tcl_loc :: SrcSpan, -- Source span
328 tcl_ctxt :: ErrCtxt, -- Error context
329 tcl_errs :: TcRef Messages, -- Place to accumulate errors
331 tcl_th_ctxt :: ThStage, -- Template Haskell context
332 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
334 tcl_rdr :: LocalRdrEnv, -- Local name envt
335 -- Maintained during renaming, of course, but also during
336 -- type checking, solely so that when renaming a Template-Haskell
337 -- splice we have the right environment for the renamer.
339 -- Does *not* include global name envt; may shadow it
340 -- Includes both ordinary variables and type variables;
341 -- they are kept distinct because tyvar have a different
342 -- occurrence contructor (Name.TvOcc)
343 -- We still need the unsullied global name env so that
344 -- we can look up record field names
346 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
347 -- defined in this module
349 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
350 -- Namely, the in-scope TyVars bound in tcl_env,
351 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
352 -- Why mutable? see notes with tcGetGlobalTyVars
354 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
358 {- Note [Given Insts]
360 Because of GADTs, we have to pass inwards the Insts provided by type signatures
361 and existential contexts. Consider
362 data T a where { T1 :: b -> b -> T [b] }
363 f :: Eq a => T a -> Bool
364 f (T1 x y) = [x]==[y]
366 The constructor T1 binds an existential variable 'b', and we need Eq [b].
367 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
372 ---------------------------
373 -- Template Haskell levels
374 ---------------------------
377 -- Indicates how many levels of brackets we are inside
379 -- Incremented when going inside a bracket,
380 -- decremented when going inside a splice
381 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
382 -- original "Template meta-programming for Haskell" paper
384 impLevel, topLevel :: ThLevel
385 topLevel = 1 -- Things defined at top level of this module
386 impLevel = 0 -- Imported things; they can be used inside a top level splice
390 -- g1 = $(map ...) is OK
391 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
395 = Comp ThLevel -- Ordinary compiling, usually at level topLevel but annotations use a lower level
396 | Splice ThLevel -- Inside a splice
397 | Brack ThLevel -- Inside brackets;
398 (TcRef [PendingSplice]) -- accumulate pending splices here
399 (TcRef LIE) -- and type constraints here
400 topStage, topAnnStage, topSpliceStage :: ThStage
401 topStage = Comp topLevel
402 topAnnStage = Comp (topLevel - 1)
403 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
405 ---------------------------
406 -- Arrow-notation context
407 ---------------------------
410 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
411 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
416 Here, x is not in scope in e1, but it is in scope in e2. This can get
420 proc y -> (proc z -> e1) -< e2
422 Here, x and z are in scope in e1, but y is not. We implement this by
423 recording the environment when passing a proc (using newArrowScope),
424 and returning to that (using escapeArrowScope) on the left of -< and the
430 | ArrowCtxt (Env TcGblEnv TcLclEnv)
432 -- Record the current environment (outside a proc)
433 newArrowScope :: TcM a -> TcM a
436 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
438 -- Return to the stored environment (from the enclosing proc)
439 escapeArrowScope :: TcM a -> TcM a
441 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
443 ArrowCtxt env' -> env'
445 ---------------------------
447 ---------------------------
450 = AGlobal TyThing -- Used only in the return type of a lookup
452 | ATcId { -- Ids defined in this module; may not be fully zonked
454 tct_co :: RefinementVisibility, -- Previously: Maybe HsWrapper
455 -- Nothing <=> Do not apply a GADT type refinement
456 -- I am wobbly, or have no free
458 -- Just co <=> Apply any type refinement to me,
459 -- and record it in the coercion
460 tct_type :: TcType, -- Type of (coercion applied to id)
461 tct_level :: ThLevel }
463 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
464 -- is currently refined. We only need the Name
465 -- for error-message purposes
467 | AThing TcKind -- Used temporarily, during kind checking, for the
468 -- tycons and clases in this recursive group
470 data RefinementVisibility
471 = Unrefineable -- Do not apply a GADT refinement
472 -- I have no free variables
474 | Rigid HsWrapper -- Apply any refinement to me
475 -- and record it in the coercion
477 | Wobbly -- Do not apply a GADT refinement
480 | WobblyInvisible -- Wobbly type, not available inside current
483 instance Outputable TcTyThing where -- Debugging only
484 ppr (AGlobal g) = pprTyThing g
485 ppr elt@(ATcId {}) = text "Identifier" <>
486 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
487 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
488 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
489 ppr (AThing k) = text "AThing" <+> ppr k
491 pprTcTyThingCategory :: TcTyThing -> SDoc
492 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
493 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
494 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
495 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
497 instance Outputable RefinementVisibility where
498 ppr Unrefineable = ptext (sLit "unrefineable")
499 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
500 ppr Wobbly = ptext (sLit "wobbly")
501 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
506 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
507 -- Innermost first. Monadic so that we have a chance
508 -- to deal with bound type variables just before error
509 -- message construction
513 %************************************************************************
515 Operations over ImportAvails
517 %************************************************************************
520 -- | 'ImportAvails' summarises what was imported from where, irrespective of
521 -- whether the imported things are actually used or not. It is used:
523 -- * when processing the export list,
525 -- * when constructing usage info for the interface file,
527 -- * to identify the list of directly imported modules for initialisation
528 -- purposes and for optimised overlap checking of family instances,
530 -- * when figuring out what things are really unused
534 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
535 -- ^ Domain is all directly-imported modules
536 -- The 'ModuleName' is what the module was imported as, e.g. in
544 -- - @True@ => import was @import Foo ()@
546 -- - @False@ => import was some other form
550 -- (a) to help construct the usage information in the interface
551 -- file; if we import somethign we need to recompile if the
552 -- export version changes
554 -- (b) to specify what child modules to initialise
556 -- We need a full ModuleEnv rather than a ModuleNameEnv here,
557 -- because we might be importing modules of the same name from
558 -- different packages. (currently not the case, but might be in the
561 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
562 -- ^ Home-package modules needed by the module being compiled
564 -- It doesn't matter whether any of these dependencies
565 -- are actually /used/ when compiling the module; they
566 -- are listed if they are below it at all. For
567 -- example, suppose M imports A which imports X. Then
568 -- compiling M might not need to consult X.hi, but X
569 -- is still listed in M's dependencies.
571 imp_dep_pkgs :: [PackageId],
572 -- ^ Packages needed by the module being compiled, whether directly,
573 -- or via other modules in this package, or via modules imported
574 -- from other packages.
576 imp_orphs :: [Module],
577 -- ^ Orphan modules below us in the import tree (and maybe including
578 -- us for imported modules)
580 imp_finsts :: [Module]
581 -- ^ Family instance modules below us in the import tree (and maybe
582 -- including us for imported modules)
585 mkModDeps :: [(ModuleName, IsBootInterface)]
586 -> ModuleNameEnv (ModuleName, IsBootInterface)
587 mkModDeps deps = foldl add emptyUFM deps
589 add env elt@(m,_) = addToUFM env m elt
591 emptyImportAvails :: ImportAvails
592 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
593 imp_dep_mods = emptyUFM,
598 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
600 (ImportAvails { imp_mods = mods1,
601 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
602 imp_orphs = orphs1, imp_finsts = finsts1 })
603 (ImportAvails { imp_mods = mods2,
604 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
605 imp_orphs = orphs2, imp_finsts = finsts2 })
606 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
607 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
608 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
609 imp_orphs = orphs1 `unionLists` orphs2,
610 imp_finsts = finsts1 `unionLists` finsts2 }
612 plus_mod_dep (m1, boot1) (m2, boot2)
613 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
614 -- Check mod-names match
615 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
618 %************************************************************************
620 \subsection{Where from}
622 %************************************************************************
624 The @WhereFrom@ type controls where the renamer looks for an interface file
628 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
629 | ImportBySystem -- Non user import.
631 instance Outputable WhereFrom where
632 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
634 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
638 %************************************************************************
640 \subsection[Inst-types]{@Inst@ types}
642 v%************************************************************************
644 An @Inst@ is either a dictionary, an instance of an overloaded
645 literal, or an instance of an overloaded value. We call the latter a
646 ``method'' even though it may not correspond to a class operation.
647 For example, we might have an instance of the @double@ function at
648 type Int, represented by
650 Method 34 doubleId [Int] origin
652 In addition to the basic Haskell variants of 'Inst's, they can now also
653 represent implication constraints 'forall tvs. given => wanted'
654 and equality constraints 'co :: ty1 ~ ty2'.
656 NB: Equalities occur in two flavours:
658 (1) Dict {tci_pred = EqPred ty1 ty2}
659 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
661 The former arises from equalities in contexts, whereas the latter is used
662 whenever the type checker introduces an equality (e.g., during deferring
665 I am not convinced that this duplication is necessary or useful! -=chak
671 tci_pred :: TcPredType, -- Class or implicit parameter only
675 | ImplicInst { -- An implication constraint
676 -- forall tvs. given => wanted
678 tci_tyvars :: [TcTyVar], -- Quantified type variables
679 tci_given :: [Inst], -- Only Dicts and EqInsts
680 -- (no Methods, LitInsts, ImplicInsts)
681 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
682 -- (no Methods or LitInsts)
686 -- NB: the tci_given are not necessarily rigid
689 tci_id :: TcId, -- The Id for the Inst
691 tci_oid :: TcId, -- The overloaded function
692 -- This function will be a global, local, or ClassOpId;
693 -- inside instance decls (only) it can also be an InstId!
694 -- The id needn't be completely polymorphic.
695 -- You'll probably find its name (for documentation purposes)
696 -- inside the InstOrigin
698 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
699 -- should be instantiated.
700 -- These types must saturate the Id's foralls.
702 tci_theta :: TcThetaType,
703 -- The (types of the) dictionaries to which the function
704 -- must be applied to get the method
708 -- INVARIANT 1: in (Method m f tys theta tau loc)
709 -- type of m = type of (f tys dicts(from theta))
711 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
712 -- Reason: two methods are considered equal if the
713 -- base Id matches, and the instantiating types
714 -- match. The TcThetaType should then match too.
715 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
719 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
720 -- INVARIANT: never a rebindable-syntax literal
721 -- Reason: tcSyntaxName does unification, and we
722 -- don't want to deal with that during tcSimplify,
723 -- when resolving LitInsts
725 tci_ty :: TcType, -- The type at which the literal is used
729 | EqInst { -- delayed unification of the form
731 tci_left :: TcType, -- ty1 -- both types are...
732 tci_right :: TcType, -- ty2 -- ...free of boxes
733 tci_co :: EqInstCo, -- co
736 tci_name :: Name -- Debugging help only: this makes it easier to
737 -- follow where a constraint is used in a morass
738 -- of trace messages! Unlike other Insts, it
739 -- has no semantic significance whatsoever.
742 type EqInstCo = Either -- Distinguish between given and wanted coercions
743 TcTyVar -- - a wanted equation, with a hole, to be filled
744 -- with a witness for the equality; for equation
745 -- arising from deferring unification, 'ty1' is
746 -- the actual and 'ty2' the expected type
747 Coercion -- - a given equation, with a coercion witnessing
748 -- the equality; a coercion that originates
749 -- from a signature or a GADT is a CoVar, but
750 -- after normalisation of coercions, they can
751 -- be arbitrary Coercions involving constructors
752 -- and pseudo-constructors like sym and trans.
755 @Insts@ are ordered by their class/type info, rather than by their
756 unique. This allows the context-reduction mechanism to use standard finite
757 maps to do their stuff. It's horrible that this code is here, rather
758 than with the Avails handling stuff in TcSimplify
761 instance Ord Inst where
763 -- Used *only* for AvailEnv in TcSimplify
765 instance Eq Inst where
766 (==) i1 i2 = case i1 `cmpInst` i2 of
770 cmpInst :: Inst -> Inst -> Ordering
771 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
772 cmpInst (Dict {}) _ = LT
774 cmpInst (Method {}) (Dict {}) = GT
775 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
776 (tci_tys m1 `tcCmpTypes` tci_tys m2)
777 cmpInst (Method {}) _ = LT
779 cmpInst (LitInst {}) (Dict {}) = GT
780 cmpInst (LitInst {}) (Method {}) = GT
781 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
782 (tci_ty l1 `tcCmpType` tci_ty l2)
783 cmpInst (LitInst {}) _ = LT
785 -- Implication constraints are compared by *name*
786 -- not by type; that is, we make no attempt to do CSE on them
787 cmpInst (ImplicInst {}) (Dict {}) = GT
788 cmpInst (ImplicInst {}) (Method {}) = GT
789 cmpInst (ImplicInst {}) (LitInst {}) = GT
790 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
791 cmpInst (ImplicInst {}) _ = LT
793 -- same for Equality constraints
794 cmpInst (EqInst {}) (Dict {}) = GT
795 cmpInst (EqInst {}) (Method {}) = GT
796 cmpInst (EqInst {}) (LitInst {}) = GT
797 cmpInst (EqInst {}) (ImplicInst {}) = GT
798 cmpInst i1@(EqInst {}) i2@(EqInst {}) = (tci_left i1 `tcCmpType` tci_left i2) `thenCmp`
799 (tci_right i1 `tcCmpType` tci_right i2)
803 %************************************************************************
805 \subsection[Inst-collections]{LIE: a collection of Insts}
807 %************************************************************************
810 -- FIXME: Rename this. It clashes with (Located (IE ...))
813 isEmptyLIE :: LIE -> Bool
814 isEmptyLIE = isEmptyBag
819 unitLIE :: Inst -> LIE
820 unitLIE inst = unitBag inst
822 mkLIE :: [Inst] -> LIE
823 mkLIE insts = listToBag insts
825 plusLIE :: LIE -> LIE -> LIE
826 plusLIE lie1 lie2 = lie1 `unionBags` lie2
828 plusLIEs :: [LIE] -> LIE
829 plusLIEs lies = unionManyBags lies
831 lieToList :: LIE -> [Inst]
832 lieToList = bagToList
834 listToLIE :: [Inst] -> LIE
835 listToLIE = listToBag
837 consLIE :: Inst -> LIE -> LIE
838 consLIE inst lie = lie `snocBag` inst
839 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
840 -- to ensure that we tend to report the *leftmost* type-constraint error
843 -- we'd like to complain about the '1', not the '3'.
845 -- "Half-hearted" because the rest of the type checker makes no great
846 -- claims for retaining order in the constraint set. Still, this
847 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
851 %************************************************************************
853 \subsection[Inst-origin]{The @InstOrigin@ type}
855 %************************************************************************
857 The @InstOrigin@ type gives information about where a dictionary came from.
858 This is important for decent error message reporting because dictionaries
859 don't appear in the original source code. Doubtless this type will evolve...
861 It appears in TcMonad because there are a couple of error-message-generation
862 functions that deal with it.
865 -------------------------------------------
866 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
868 instLoc :: Inst -> InstLoc
869 instLoc inst = tci_loc inst
871 instSpan :: Inst -> SrcSpan
872 instSpan wanted = instLocSpan (instLoc wanted)
874 instLocSpan :: InstLoc -> SrcSpan
875 instLocSpan (InstLoc _ s _) = s
877 instLocOrigin :: InstLoc -> InstOrigin
878 instLocOrigin (InstLoc o _ _) = o
880 pprInstArising :: Inst -> SDoc
881 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
883 pprInstLoc :: InstLoc -> SDoc
884 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
886 -------------------------------------------
888 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
889 -- Places that bind type variables and introduce
890 -- available constraints
892 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
894 -------------------------------------------------------
895 -- The rest are all occurrences: Insts that are 'wanted'
896 -------------------------------------------------------
897 | OccurrenceOf Name -- Occurrence of an overloaded identifier
898 | SpecPragOrigin Name -- Specialisation pragma for identifier
900 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
902 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
903 | NegateOrigin -- Occurrence of syntactic negation
905 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
906 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
907 | TupleOrigin -- (..,..)
909 | InstSigOrigin -- A dict occurrence arising from instantiating
910 -- a polymorphic type during a subsumption check
912 | ExprSigOrigin -- e :: ty
915 | InstScOrigin -- Typechecking superclasses of an instance declaration
916 | DerivOrigin -- Typechecking deriving
917 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
918 | DefaultOrigin -- Typechecking a default decl
919 | DoOrigin -- Arising from a do expression
920 | ProcOrigin -- Arising from a proc expression
921 | ImplicOrigin SDoc -- An implication constraint
922 | EqOrigin -- A type equality
923 | AnnOrigin -- An annotation
925 instance Outputable InstOrigin where
926 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
927 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
928 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
929 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
930 ppr RecordUpdOrigin = ptext (sLit "a record update")
931 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
932 ppr ViewPatOrigin = ptext (sLit "a view pattern")
933 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
934 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
935 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
936 ppr TupleOrigin = ptext (sLit "a tuple")
937 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
938 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
939 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
940 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
941 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
942 ppr DoOrigin = ptext (sLit "a do statement")
943 ppr ProcOrigin = ptext (sLit "a proc expression")
944 ppr (ImplicOrigin doc) = doc
945 ppr (SigOrigin info) = pprSkolInfo info
946 ppr EqOrigin = ptext (sLit "a type equality")
947 ppr InstSigOrigin = panic "ppr InstSigOrigin"
948 ppr AnnOrigin = ptext (sLit "an annotation")