2 % (c) The GRASP Project, Glasgow University, 1992-2002
6 TcRnIf, TcRn, TcM, RnM, IfM, IfL, IfG, -- The monad is opaque outside this module
9 -- The environment types
11 TcGblEnv(..), TcLclEnv(..),
12 IfGblEnv(..), IfLclEnv(..),
16 ImportAvails(..), emptyImportAvails, plusImportAvails,
17 plusAvail, pruneAvails,
18 AvailEnv, emptyAvailEnv, unitAvailEnv, plusAvailEnv,
19 mkAvailEnv, lookupAvailEnv, lookupAvailEnv_maybe, availEnvElts, addAvail,
20 WhereFrom(..), mkModDeps,
23 TcTyThing(..), pprTcTyThingCategory, GadtRefinement,
26 ThStage(..), topStage, topSpliceStage,
27 ThLevel, impLevel, topLevel,
30 Inst(..), InstOrigin(..), InstLoc(..), pprInstLoc,
31 instLocSrcLoc, instLocSrcSpan,
32 LIE, emptyLIE, unitLIE, plusLIE, consLIE,
33 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
36 TcId, TcIdSet, TcDictBinds
39 #include "HsVersions.h"
41 import HsSyn ( PendingSplice, HsOverLit, LRuleDecl, LForeignDecl,
42 ArithSeqInfo, DictBinds, LHsBinds, HsGroup )
43 import HscTypes ( FixityEnv,
44 HscEnv, TypeEnv, TyThing,
45 GenAvailInfo(..), AvailInfo, HscSource(..),
46 availName, IsBootInterface, Deprecations )
47 import Packages ( PackageId )
48 import Type ( Type, TvSubstEnv, pprParendType, pprTyThingCategory )
49 import TcType ( TcTyVarSet, TcType, TcTauType, TcThetaType, SkolemInfo,
50 TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes, pprSkolInfo )
51 import InstEnv ( Instance, InstEnv )
53 import RdrName ( GlobalRdrEnv, LocalRdrEnv )
56 import NameSet ( NameSet, unionNameSets, DefUses )
57 import OccName ( OccEnv )
58 import Var ( Id, TyVar )
59 import VarEnv ( TidyEnv )
61 import SrcLoc ( SrcSpan, SrcLoc, srcSpanStart )
62 import VarSet ( IdSet )
63 import ErrUtils ( Messages, Message )
64 import UniqSupply ( UniqSupply )
65 import BasicTypes ( IPName )
66 import Util ( thenCmp )
69 import Maybe ( mapMaybe )
70 import ListSetOps ( unionLists )
74 %************************************************************************
76 Standard monad definition for TcRn
77 All the combinators for the monad can be found in TcRnMonad
79 %************************************************************************
81 The monad itself has to be defined here, because it is mentioned by ErrCtxt
84 type TcRef a = IORef a
85 type TcId = Id -- Type may be a TcType
87 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
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
101 %************************************************************************
103 The main environment types
105 %************************************************************************
108 data Env gbl lcl -- Changes as we move into an expression
110 env_top :: HscEnv, -- Top-level stuff that never changes
111 -- Includes all info about imported things
113 env_us :: TcRef UniqSupply, -- Unique supply for local varibles
115 env_gbl :: gbl, -- Info about things defined at the top level
116 -- of the module being compiled
118 env_lcl :: lcl -- Nested stuff; changes as we go into
122 -- TcGblEnv describes the top-level of the module at the
123 -- point at which the typechecker is finished work.
124 -- It is this structure that is handed on to the desugarer
128 tcg_mod :: Module, -- Module being compiled
129 tcg_src :: HscSource, -- What kind of module
130 -- (regular Haskell, hs-boot, ext-core)
132 tcg_rdr_env :: GlobalRdrEnv, -- Top level envt; used during renaming
133 tcg_default :: Maybe [Type], -- Types used for defaulting
134 -- Nothing => no 'default' decl
136 tcg_fix_env :: FixityEnv, -- Just for things in this module
138 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
139 -- All TyCons and Classes (for this module) end up in here right away,
140 -- along with their derived constructors, selectors.
142 -- (Ids defined in this module start in the local envt,
143 -- though they move to the global envt during zonking)
145 tcg_type_env_var :: TcRef TypeEnv,
146 -- Used only to initialise the interface-file
147 -- typechecker in initIfaceTcRn, so that it can see stuff
148 -- bound in this module when dealing with hi-boot recursions
149 -- Updated at intervals (e.g. after dealing with types and classes)
151 tcg_inst_env :: InstEnv, -- Instance envt for *home-package* modules
152 -- Includes the dfuns in tcg_insts
153 -- Now a bunch of things about this module that are simply
154 -- accumulated, but never consulted until the end.
155 -- Nevertheless, it's convenient to accumulate them along
156 -- with the rest of the info from this module.
157 tcg_exports :: NameSet, -- What is exported
158 tcg_imports :: ImportAvails, -- Information about what was imported
159 -- from where, including things bound
162 tcg_dus :: DefUses, -- What is defined in this module and what is used.
163 -- The latter is used to generate
164 -- (a) version tracking; no need to recompile if these
165 -- things have not changed version stamp
166 -- (b) unused-import info
168 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
169 -- "Keep alive" means give them an Exported flag, so
170 -- that the simplifier does not discard them as dead
171 -- code, and so that they are exposed in the interface file
172 -- (but not to export to the user).
174 -- Some things, like dict-fun Ids and default-method Ids are
175 -- "born" with the Exported flag on, for exactly the above reason,
176 -- but some we only discover as we go. Specifically:
177 -- * The to/from functions for generic data types
178 -- * Top-level variables appearing free in the RHS of an orphan rule
179 -- * Top-level variables appearing free in a TH bracket
181 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
182 -- Used to generate version dependencies
183 -- This records usages, rather like tcg_dus, but it has to
184 -- be a mutable variable so it can be augmented
185 -- when we look up an instance. These uses of dfuns are
186 -- rather like the free variables of the program, but
187 -- are implicit instead of explicit.
189 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
190 -- We need this so that we can generate a dependency on the
191 -- Template Haskell package, becuase the desugarer is going to
192 -- emit loads of references to TH symbols. It's rather like
193 -- tcg_inst_uses; the reference is implicit rather than explicit,
194 -- so we have to zap a mutable variable.
196 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
197 -- It's convenient to allocate an External Name for a DFun, with
198 -- a permanently-fixed unique, just like other top-level functions
199 -- defined in this module. But that means we need a canonical
200 -- occurrence name, distinct from all other dfuns in this module,
201 -- and this name supply serves that purpose (df1, df2, etc).
203 -- The next fields accumulate the payload of the module
204 -- The binds, rules and foreign-decl fiels are collected
205 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
207 -- The next fields accumulate the payload of the
208 -- module The binds, rules and foreign-decl fiels are
209 -- collected initially in un-zonked form and are
210 -- finally zonked in tcRnSrcDecls
212 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
213 -- Nothing <=> Don't retain renamed decls
215 tcg_binds :: LHsBinds Id, -- Value bindings in this module
216 tcg_deprecs :: Deprecations, -- ...Deprecations
217 tcg_insts :: [Instance], -- ...Instances
218 tcg_rules :: [LRuleDecl Id], -- ...Rules
219 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
223 %************************************************************************
225 The interface environments
226 Used when dealing with IfaceDecls
228 %************************************************************************
233 -- The type environment for the module being compiled,
234 -- in case the interface refers back to it via a reference that
235 -- was originally a hi-boot file.
236 -- We need the module name so we can test when it's appropriate
237 -- to look in this env.
238 if_rec_types :: Maybe (Module, IfG TypeEnv)
239 -- Allows a read effect, so it can be in a mutable
240 -- variable; c.f. handling the external package type env
241 -- Nothing => interactive stuff, no loops possible
246 -- The module for the current IfaceDecl
247 -- So if we see f = \x -> x
248 -- it means M.f = \x -> x, where M is the if_mod
251 -- The field is used only for error reporting
252 -- if (say) there's a Lint error in it
254 -- Where the interface came from:
255 -- .hi file, or GHCi state, or ext core
256 -- plus which bit is currently being examined
258 if_tv_env :: OccEnv TyVar, -- Nested tyvar bindings
259 if_id_env :: OccEnv Id -- Nested id binding
264 %************************************************************************
266 The local typechecker environment
268 %************************************************************************
270 The Global-Env/Local-Env story
271 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
272 During type checking, we keep in the tcg_type_env
273 * All types and classes
274 * All Ids derived from types and classes (constructors, selectors)
276 At the end of type checking, we zonk the local bindings,
277 and as we do so we add to the tcg_type_env
278 * Locally defined top-level Ids
280 Why? Because they are now Ids not TcIds. This final GlobalEnv is
281 a) fed back (via the knot) to typechecking the
282 unfoldings of interface signatures
283 b) used in the ModDetails of this module
286 data TcLclEnv -- Changes as we move inside an expression
287 -- Discarded after typecheck/rename; not passed on to desugarer
289 tcl_loc :: SrcSpan, -- Source span
290 tcl_ctxt :: ErrCtxt, -- Error context
291 tcl_errs :: TcRef Messages, -- Place to accumulate errors
293 tcl_th_ctxt :: ThStage, -- Template Haskell context
295 tcl_rdr :: LocalRdrEnv, -- Local name envt
296 -- Maintained during renaming, of course, but also during
297 -- type checking, solely so that when renaming a Template-Haskell
298 -- splice we have the right environment for the renamer.
300 -- Does *not* include global name envt; may shadow it
301 -- Includes both ordinary variables and type variables;
302 -- they are kept distinct because tyvar have a different
303 -- occurrence contructor (Name.TvOcc)
304 -- We still need the unsullied global name env so that
305 -- we can look up record field names
307 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
308 -- defined in this module
310 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
311 -- Namely, the in-scope TyVars bound in tcl_env,
312 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
313 -- Why mutable? see notes with tcGetGlobalTyVars
315 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
316 tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
318 -----------------------------------------------------------
319 -- Not yet; it's a new complication and I want to see whether it bites
320 -- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
321 -----------------------------------------------------------
324 type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
326 {- Note [Given Insts]
328 Because of GADTs, we have to pass inwards the Insts provided by type signatures
329 and existential contexts. Consider
330 data T a where { T1 :: b -> b -> T [b] }
331 f :: Eq a => T a -> Bool
332 f (T1 x y) = [x]==[y]
334 The constructor T1 binds an existential variable 'b', and we need Eq [b].
335 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
340 ---------------------------
341 -- Template Haskell levels
342 ---------------------------
345 -- Indicates how many levels of brackets we are inside
347 -- Incremented when going inside a bracket,
348 -- decremented when going inside a splice
350 impLevel, topLevel :: ThLevel
351 topLevel = 1 -- Things defined at top level of this module
352 impLevel = 0 -- Imported things; they can be used inside a top level splice
356 -- g1 = $(map ...) is OK
357 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
361 = Comp -- Ordinary compiling, at level topLevel
362 | Splice ThLevel -- Inside a splice
363 | Brack ThLevel -- Inside brackets;
364 (TcRef [PendingSplice]) -- accumulate pending splices here
365 (TcRef LIE) -- and type constraints here
366 topStage, topSpliceStage :: ThStage
368 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
371 ---------------------------
373 ---------------------------
376 = AGlobal TyThing -- Used only in the return type of a lookup
378 | ATcId TcId ThLevel -- Ids defined in this module; may not be fully zonked
380 | ATyVar Name TcType -- Type variables; tv -> type. It can't just be a TyVar
381 -- that is mutated to point to the type it is bound to,
382 -- because that would make it a wobbly type, and we
383 -- want pattern-bound lexically-scoped type variables to
384 -- be able to stand for rigid types
386 | AThing TcKind -- Used temporarily, during kind checking, for the
387 -- tycons and clases in this recursive group
389 instance Outputable TcTyThing where -- Debugging only
390 ppr (AGlobal g) = ppr g
391 ppr (ATcId g tl) = text "Identifier" <>
392 ifPprDebug (brackets (ppr g <> comma <> ppr tl))
393 ppr (ATyVar tv ty) = text "Type variable" <+> quotes (ppr tv) <+> pprParendType ty
394 ppr (AThing k) = text "AThing" <+> ppr k
396 pprTcTyThingCategory :: TcTyThing -> SDoc
397 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
398 pprTcTyThingCategory (ATyVar _ _) = ptext SLIT("Type variable")
399 pprTcTyThingCategory (ATcId _ _) = ptext SLIT("Local identifier")
400 pprTcTyThingCategory (AThing _) = ptext SLIT("Kinded thing")
404 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
405 -- Innermost first. Monadic so that we have a chance
406 -- to deal with bound type variables just before error
407 -- message construction
411 %************************************************************************
413 Operations over ImportAvails
415 %************************************************************************
417 ImportAvails summarises what was imported from where, irrespective
418 of whether the imported things are actually used or not
419 It is used * when processing the export list
420 * when constructing usage info for the inteface file
421 * to identify the list of directly imported modules
422 for initialisation purposes
423 * when figuring out what things are really unused
428 imp_env :: ModuleEnv NameSet,
429 -- All the things imported, classified by
430 -- the *module qualifier* for its import
431 -- e.g. import List as Foo
432 -- would add a binding Foo |-> ...stuff from List...
435 -- We need to classify them like this so that we can figure out
436 -- "module M" export specifiers in an export list
437 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
438 -- everything that is unambiguously in scope as 'M.x'
439 -- and where plain 'x' is (perhaps ambiguously) in scope.
440 -- So the starting point is all things that are in scope as 'M.x',
441 -- which is what this field tells us.
443 imp_mods :: ModuleEnv (Module, Maybe Bool, SrcSpan),
444 -- Domain is all directly-imported modules
445 -- Maybe value answers the question "is the import restricted?"
446 -- Nothing => unrestricted import (e.g., "import Foo")
447 -- Just True => restricted import, at least one entity (e.g., "import Foo(x)")
448 -- Just False => fully restricted import (e.g., "import Foo ()")
450 -- A distinction is made between the first and the third in order
451 -- to more precisely emit warnings about unused imports.
453 -- We need the Module in the range because we can't get
454 -- the keys of a ModuleEnv
456 -- (a) to help construct the usage information in
457 -- the interface file; if we import everything we
458 -- need to recompile if the module version changes
459 -- (b) to specify what child modules to initialise
461 imp_dep_mods :: ModuleEnv (Module, IsBootInterface),
462 -- Home-package modules needed by the module being compiled
464 -- It doesn't matter whether any of these dependencies
465 -- are actually *used* when compiling the module; they
466 -- are listed if they are below it at all. For
467 -- example, suppose M imports A which imports X. Then
468 -- compiling M might not need to consult X.hi, but X
469 -- is still listed in M's dependencies.
471 imp_dep_pkgs :: [PackageId],
472 -- Packages needed by the module being compiled, whether
473 -- directly, or via other modules in this package, or via
474 -- modules imported from other packages.
476 imp_orphs :: [Module]
477 -- Orphan modules below us in the import tree
480 mkModDeps :: [(Module, IsBootInterface)]
481 -> ModuleEnv (Module, IsBootInterface)
482 mkModDeps deps = foldl add emptyModuleEnv deps
484 add env elt@(m,_) = extendModuleEnv env m elt
486 emptyImportAvails :: ImportAvails
487 emptyImportAvails = ImportAvails { imp_env = emptyModuleEnv,
488 imp_mods = emptyModuleEnv,
489 imp_dep_mods = emptyModuleEnv,
493 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
495 (ImportAvails { imp_env = env1, imp_mods = mods1,
496 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
497 (ImportAvails { imp_env = env2, imp_mods = mods2,
498 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
499 = ImportAvails { imp_env = plusModuleEnv_C unionNameSets env1 env2,
500 imp_mods = mods1 `plusModuleEnv` mods2,
501 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
502 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
503 imp_orphs = orphs1 `unionLists` orphs2 }
505 plus_mod_dep (m1, boot1) (m2, boot2)
506 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
507 -- Check mod-names match
508 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
511 %************************************************************************
513 Avails, AvailEnv, etc
515 v%************************************************************************
518 plusAvail (Avail n1) (Avail n2) = Avail n1
519 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
522 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
525 -------------------------
526 pruneAvails :: (Name -> Bool) -- Keep if this is True
529 pruneAvails keep avails
530 = mapMaybe del avails
532 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
533 del (Avail n) | keep n = Just (Avail n)
534 | otherwise = Nothing
535 del (AvailTC n ns) | null ns' = Nothing
536 | otherwise = Just (AvailTC n ns')
541 ---------------------------------------
543 ---------------------------------------
546 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
548 emptyAvailEnv :: AvailEnv
549 emptyAvailEnv = emptyNameEnv
551 unitAvailEnv :: AvailInfo -> AvailEnv
552 unitAvailEnv a = unitNameEnv (availName a) a
554 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
555 plusAvailEnv = plusNameEnv_C plusAvail
557 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
558 lookupAvailEnv_maybe = lookupNameEnv
560 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
561 lookupAvailEnv env n = case lookupNameEnv env n of
563 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
565 availEnvElts = nameEnvElts
567 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
568 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
570 mkAvailEnv :: [AvailInfo] -> AvailEnv
571 -- 'avails' may have several items with the same availName
572 -- E.g import Ix( Ix(..), index )
573 -- will give Ix(Ix,index,range) and Ix(index)
574 -- We want to combine these; addAvail does that
575 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
578 %************************************************************************
580 \subsection{Where from}
582 %************************************************************************
584 The @WhereFrom@ type controls where the renamer looks for an interface file
588 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
589 | ImportBySystem -- Non user import.
591 instance Outputable WhereFrom where
592 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
594 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
598 %************************************************************************
600 \subsection[Inst-types]{@Inst@ types}
602 v%************************************************************************
604 An @Inst@ is either a dictionary, an instance of an overloaded
605 literal, or an instance of an overloaded value. We call the latter a
606 ``method'' even though it may not correspond to a class operation.
607 For example, we might have an instance of the @double@ function at
608 type Int, represented by
610 Method 34 doubleId [Int] origin
622 TcId -- The overloaded function
623 -- This function will be a global, local, or ClassOpId;
624 -- inside instance decls (only) it can also be an InstId!
625 -- The id needn't be completely polymorphic.
626 -- You'll probably find its name (for documentation purposes)
627 -- inside the InstOrigin
629 [TcType] -- The types to which its polymorphic tyvars
630 -- should be instantiated.
631 -- These types must saturate the Id's foralls.
633 TcThetaType -- The (types of the) dictionaries to which the function
634 -- must be applied to get the method
636 TcTauType -- The tau-type of the method
640 -- INVARIANT 1: in (Method u f tys theta tau loc)
641 -- type of (f tys dicts(from theta)) = tau
643 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
644 -- Reason: two methods are considered equal if the
645 -- base Id matches, and the instantiating types
646 -- match. The TcThetaType should then match too.
647 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
651 (HsOverLit Name) -- The literal from the occurrence site
652 -- INVARIANT: never a rebindable-syntax literal
653 -- Reason: tcSyntaxName does unification, and we
654 -- don't want to deal with that during tcSimplify,
655 -- when resolving LitInsts
656 TcType -- The type at which the literal is used
660 @Insts@ are ordered by their class/type info, rather than by their
661 unique. This allows the context-reduction mechanism to use standard finite
662 maps to do their stuff.
665 instance Ord Inst where
668 instance Eq Inst where
669 (==) i1 i2 = case i1 `cmpInst` i2 of
673 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
674 cmpInst (Dict _ _ _) other = LT
676 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
677 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
678 cmpInst (Method _ _ _ _ _ _) other = LT
680 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
681 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _ _) = GT
682 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
686 %************************************************************************
688 \subsection[Inst-collections]{LIE: a collection of Insts}
690 %************************************************************************
695 isEmptyLIE = isEmptyBag
697 unitLIE inst = unitBag inst
698 mkLIE insts = listToBag insts
699 plusLIE lie1 lie2 = lie1 `unionBags` lie2
700 consLIE inst lie = inst `consBag` lie
701 plusLIEs lies = unionManyBags lies
702 lieToList = bagToList
703 listToLIE = listToBag
707 %************************************************************************
709 \subsection[Inst-origin]{The @InstOrigin@ type}
711 %************************************************************************
713 The @InstOrigin@ type gives information about where a dictionary came from.
714 This is important for decent error message reporting because dictionaries
715 don't appear in the original source code. Doubtless this type will evolve...
717 It appears in TcMonad because there are a couple of error-message-generation
718 functions that deal with it.
721 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
723 instLocSrcLoc :: InstLoc -> SrcLoc
724 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
726 instLocSrcSpan :: InstLoc -> SrcSpan
727 instLocSrcSpan (InstLoc _ src_span _) = src_span
730 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
731 -- Places that bind type variables and introduce
732 -- available constraints
734 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
736 -------------------------------------------------------
737 -- The rest are all occurrences: Insts that are 'wanted'
738 -------------------------------------------------------
739 | OccurrenceOf Name -- Occurrence of an overloaded identifier
741 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
743 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
745 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
746 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
748 | InstSigOrigin -- A dict occurrence arising from instantiating
749 -- a polymorphic type during a subsumption check
752 | InstScOrigin -- Typechecking superclasses of an instance declaration
753 | DerivOrigin -- Typechecking deriving
754 | DefaultOrigin -- Typechecking a default decl
755 | DoOrigin -- Arising from a do expression
756 | ProcOrigin -- Arising from a proc expression
760 pprInstLoc :: InstLoc -> SDoc
761 pprInstLoc (InstLoc orig locn _)
762 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
764 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
765 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
766 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
767 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
768 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
769 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
770 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
771 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
772 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
773 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
774 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
775 pp_orig DoOrigin = ptext SLIT("a do statement")
776 pp_orig ProcOrigin = ptext SLIT("a proc expression")
777 pp_orig (SigOrigin info) = pprSkolInfo info