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(..),
15 EntityUsage, emptyUsages, ErrCtxt,
16 ImportAvails(..), emptyImportAvails, plusImportAvails,
17 plusAvail, pruneAvails,
18 AvailEnv, emptyAvailEnv, unitAvailEnv, plusAvailEnv,
19 mkAvailEnv, lookupAvailEnv, lookupAvailEnv_maybe, availEnvElts, addAvail,
20 WhereFrom(..), mkModDeps,
23 TcTyThing(..), GadtRefinement,
26 ThStage(..), topStage, topSpliceStage,
27 ThLevel, impLevel, topLevel,
30 ArrowCtxt(..), topArrowCtxt, ProcLevel, topProcLevel,
33 Inst(..), InstOrigin(..), InstLoc(..), pprInstLoc,
34 instLocSrcLoc, instLocSrcSpan,
35 LIE, emptyLIE, unitLIE, plusLIE, consLIE,
36 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
39 TcId, TcIdSet, TcDictBinds
42 #include "HsVersions.h"
44 import HsSyn ( PendingSplice, HsOverLit, LRuleDecl, LForeignDecl,
45 ArithSeqInfo, DictBinds, LHsBinds )
46 import HscTypes ( FixityEnv,
47 HscEnv, TypeEnv, TyThing,
48 GenAvailInfo(..), AvailInfo,
49 availName, IsBootInterface, Deprecations )
50 import Packages ( PackageName )
51 import Type ( Type, TvSubstEnv )
52 import TcType ( TcTyVarSet, TcType, TcTauType, TcThetaType, SkolemInfo,
53 TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes )
54 import InstEnv ( DFunId, InstEnv )
56 import RdrName ( GlobalRdrEnv, LocalRdrEnv )
59 import NameSet ( NameSet, emptyNameSet, DefUses )
60 import OccName ( OccEnv )
61 import Var ( Id, TyVar )
62 import VarEnv ( TidyEnv )
64 import SrcLoc ( SrcSpan, SrcLoc, srcSpanStart )
65 import VarSet ( IdSet )
66 import ErrUtils ( Messages, Message )
67 import UniqSupply ( UniqSupply )
68 import BasicTypes ( IPName )
69 import Util ( thenCmp )
72 import Maybe ( mapMaybe )
73 import ListSetOps ( unionLists )
77 %************************************************************************
79 Standard monad definition for TcRn
80 All the combinators for the monad can be found in TcRnMonad
82 %************************************************************************
84 The monad itself has to be defined here, because it is mentioned by ErrCtxt
87 type TcRef a = IORef a
88 type TcId = Id -- Type may be a TcType
90 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
94 type TcRnIf a b c = IOEnv (Env a b) c
95 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
96 type IfG a = IfM () a -- Top level
97 type IfL a = IfM IfLclEnv a -- Nested
98 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
99 type RnM a = TcRn a -- Historical
100 type TcM a = TcRn a -- Historical
104 %************************************************************************
106 The main environment types
108 %************************************************************************
111 data Env gbl lcl -- Changes as we move into an expression
113 env_top :: HscEnv, -- Top-level stuff that never changes
114 -- Includes all info about imported things
116 env_us :: TcRef UniqSupply, -- Unique supply for local varibles
118 env_gbl :: gbl, -- Info about things defined at the top level
119 -- of the module being compiled
121 env_lcl :: lcl -- Nested stuff; changes as we go into
125 -- TcGblEnv describes the top-level of the module at the
126 -- point at which the typechecker is finished work.
127 -- It is this structure that is handed on to the desugarer
131 tcg_mod :: Module, -- Module being compiled
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 -- The next fields accumulate the payload of the module
197 -- The binds, rules and foreign-decl fiels are collected
198 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
199 tcg_binds :: LHsBinds Id, -- Value bindings in this module
200 tcg_deprecs :: Deprecations, -- ...Deprecations
201 tcg_insts :: [DFunId], -- ...Instances
202 tcg_rules :: [LRuleDecl Id], -- ...Rules
203 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
207 %************************************************************************
209 The interface environments
210 Used when dealing with IfaceDecls
212 %************************************************************************
217 -- The type environment for the module being compiled,
218 -- in case the interface refers back to it via a reference that
219 -- was originally a hi-boot file.
220 -- We need the module name so we can test when it's appropriate
221 -- to look in this env.
222 if_rec_types :: Maybe (Module, IfG TypeEnv)
223 -- Allows a read effect, so it can be in a mutable
224 -- variable; c.f. handling the external package type env
225 -- Nothing => interactive stuff, no loops possible
230 -- The module for the current IfaceDecl
231 -- So if we see f = \x -> x
232 -- it means M.f = \x -> x, where M is the if_mod
233 if_mod :: ModuleName,
235 if_tv_env :: OccEnv TyVar, -- Nested tyvar bindings
236 if_id_env :: OccEnv Id -- Nested id binding
241 %************************************************************************
243 The local typechecker environment
245 %************************************************************************
247 The Global-Env/Local-Env story
248 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
249 During type checking, we keep in the tcg_type_env
250 * All types and classes
251 * All Ids derived from types and classes (constructors, selectors)
253 At the end of type checking, we zonk the local bindings,
254 and as we do so we add to the tcg_type_env
255 * Locally defined top-level Ids
257 Why? Because they are now Ids not TcIds. This final GlobalEnv is
258 a) fed back (via the knot) to typechecking the
259 unfoldings of interface signatures
260 b) used in the ModDetails of this module
263 data TcLclEnv -- Changes as we move inside an expression
264 -- Discarded after typecheck/rename; not passed on to desugarer
266 tcl_loc :: SrcSpan, -- Source span
267 tcl_ctxt :: ErrCtxt, -- Error context
268 tcl_errs :: TcRef Messages, -- Place to accumulate errors
270 tcl_th_ctxt :: ThStage, -- Template Haskell context
271 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
273 tcl_rdr :: LocalRdrEnv, -- Local name envt
274 -- Maintained during renaming, of course, but also during
275 -- type checking, solely so that when renaming a Template-Haskell
276 -- splice we have the right environment for the renamer.
278 -- Does *not* include global name envt; may shadow it
279 -- Includes both ordinary variables and type variables;
280 -- they are kept distinct because tyvar have a different
281 -- occurrence contructor (Name.TvOcc)
282 -- We still need the unsullied global name env so that
283 -- we can look up record field names
285 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
286 -- defined in this module
288 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
289 -- Namely, the in-scope TyVars bound in tcl_env,
290 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
291 -- Why mutable? see notes with tcGetGlobalTyVars
293 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
294 tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
296 -----------------------------------------------------------
297 -- Not yet; it's a new complication and I want to see whether it bites
298 -- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
299 -----------------------------------------------------------
302 type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
304 {- Note [Given Insts]
306 Because of GADTs, we have to pass inwards the Insts provided by type signatures
307 and existential contexts. Consider
308 data T a where { T1 :: b -> b -> T [b] }
309 f :: Eq a => T a -> Bool
310 f (T1 x y) = [x]==[y]
312 The constructor T1 binds an existential variable 'b', and we need Eq [b].
313 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
318 ---------------------------
319 -- Template Haskell levels
320 ---------------------------
323 -- Indicates how many levels of brackets we are inside
325 -- Incremented when going inside a bracket,
326 -- decremented when going inside a splice
328 impLevel, topLevel :: ThLevel
329 topLevel = 1 -- Things defined at top level of this module
330 impLevel = 0 -- Imported things; they can be used inside a top level splice
334 -- g1 = $(map ...) is OK
335 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
339 = Comp -- Ordinary compiling, at level topLevel
340 | Splice ThLevel -- Inside a splice
341 | Brack ThLevel -- Inside brackets;
342 (TcRef [PendingSplice]) -- accumulate pending splices here
343 (TcRef LIE) -- and type constraints here
344 topStage, topSpliceStage :: ThStage
346 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
349 ---------------------------
350 -- Arrow-notation stages
351 ---------------------------
353 -- In arrow notation, a variable bound by a proc (or enclosed let/kappa)
354 -- is not in scope to the left of an arrow tail (-<). For example
356 -- proc x -> (e1 -< e2)
358 -- Here, x is not in scope in e1, but it is in scope in e2. This can get
359 -- a bit complicated:
362 -- prox y -> (proc z -> e1) -< e2
364 -- Here, x and z are in scope in e1, but y is not. Here's how we track this:
365 -- a) Assign an "proc level" to each proc, being the number of
366 -- lexically-enclosing procs + 1.
367 -- b) Assign to each local variable the proc-level of its lexically
369 -- c) Keep a list of out-of-scope procs. When moving to the left of
370 -- an arrow-tail, add the proc-level of the immediately enclosing
372 -- d) When looking up a variable, complain if its proc-level is in
375 type ProcLevel = Int -- Always >= 0
376 topProcLevel = 0 -- Not inside any proc
378 data ArrowCtxt = ArrCtxt { proc_level :: ProcLevel, -- Current level
379 proc_banned :: [ProcLevel] } -- Out of scope proc-levels
381 topArrowCtxt = ArrCtxt { proc_level = topProcLevel, proc_banned = [] }
383 ---------------------------
385 ---------------------------
388 = AGlobal TyThing -- Used only in the return type of a lookup
389 | ATcId TcId ThLevel ProcLevel -- Ids defined in this module; may not be fully zonked
390 | ATyVar TyVar -- Type variables
391 | AThing TcKind -- Used temporarily, during kind checking, for the
392 -- tycons and clases in this recursive group
394 instance Outputable TcTyThing where -- Debugging only
395 ppr (AGlobal g) = text "AGlobal" <+> ppr g
396 ppr (ATcId g tl pl) = text "ATcId" <+> ppr g <+> ppr tl <+> ppr pl
397 ppr (ATyVar t) = text "ATyVar" <+> ppr t
398 ppr (AThing k) = text "AThing" <+> ppr k
402 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
403 -- Innermost first. Monadic so that we have a chance
404 -- to deal with bound type variables just before error
405 -- message construction
409 %************************************************************************
413 %************************************************************************
415 EntityUsage tells what things are actually need in order to compile this
416 module. It is used for generating the usage-version field of the ModIface.
418 Note that we do not record version info for entities from
419 other (non-home) packages. If the package changes, GHC doesn't help.
422 type EntityUsage = NameSet
423 -- The Names are all the (a) home-package
424 -- (b) "big" (i.e. no data cons, class ops)
425 -- (c) non-locally-defined
427 -- names that have been slurped in so far.
428 -- This is used to generate the "usage" information for this module.
430 emptyUsages :: EntityUsage
431 emptyUsages = emptyNameSet
435 %************************************************************************
437 Operations over ImportAvails
439 %************************************************************************
441 ImportAvails summarises what was imported from where, irrespective
442 of whether the imported things are actually used or not
443 It is used * when processing the export list
444 * when constructing usage info for the inteface file
445 * to identify the list of directly imported modules
446 for initialisation purposes
447 * when figuring out what things are really unused
453 -- All the things that are available from the import
454 -- Its domain is all the "main" things;
455 -- i.e. *excluding* class ops and constructors
456 -- (which appear inside their parent AvailTC)
458 imp_qual :: ModuleEnv AvailEnv,
459 -- Used to figure out "module M" export specifiers
460 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
461 -- everything that is unambiguously in scope as 'M.x'
462 -- and where plain 'x' is (perhaps ambiguously) in scope.
463 -- So the starting point is all things that are in scope as 'M.x',
464 -- which is what this field tells us.
466 -- Domain is the *module qualifier* for imports.
467 -- e.g. import List as Foo
468 -- would add a binding Foo |-> ...stuff from List...
470 -- We keep the stuff as an AvailEnv so that it's easy to
471 -- combine stuff coming from different (unqualified)
472 -- imports of the same module
474 imp_mods :: ModuleEnv (Module, Maybe Bool, SrcSpan),
475 -- Domain is all directly-imported modules
476 -- Maybe value answers the question "is the import restricted?"
477 -- Nothing => unrestricted import (e.g., "import Foo")
478 -- Just True => restricted import, at least one entity (e.g., "import Foo(x)")
479 -- Just False => fully restricted import (e.g., "import Foo ()")
481 -- A distinction is made between the first and the third in order
482 -- to more precisely emit warnings about unused imports.
484 -- We need the Module in the range because we can't get
485 -- the keys of a ModuleEnv
487 -- (a) to help construct the usage information in
488 -- the interface file; if we import everything we
489 -- need to recompile if the module version changes
490 -- (b) to specify what child modules to initialise
492 imp_dep_mods :: ModuleEnv (ModuleName, IsBootInterface),
493 -- Home-package modules needed by the module being compiled
495 -- It doesn't matter whether any of these dependencies are actually
496 -- *used* when compiling the module; they are listed if they are below
497 -- it at all. For example, suppose M imports A which imports X. Then
498 -- compiling M might not need to consult X.hi, but X is still listed
499 -- in M's dependencies.
501 imp_dep_pkgs :: [PackageName],
502 -- Packages needed by the module being compiled, whether
503 -- directly, or via other modules in this package, or via
504 -- modules imported from other packages.
506 imp_orphs :: [ModuleName]
507 -- Orphan modules below us in the import tree
510 mkModDeps :: [(ModuleName, IsBootInterface)]
511 -> ModuleEnv (ModuleName, IsBootInterface)
512 mkModDeps deps = foldl add emptyModuleEnv deps
514 add env elt@(m,_) = extendModuleEnvByName env m elt
516 emptyImportAvails :: ImportAvails
517 emptyImportAvails = ImportAvails { imp_env = emptyAvailEnv,
518 imp_qual = emptyModuleEnv,
519 imp_mods = emptyModuleEnv,
520 imp_dep_mods = emptyModuleEnv,
524 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
526 (ImportAvails { imp_env = env1, imp_qual = unqual1, imp_mods = mods1,
527 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
528 (ImportAvails { imp_env = env2, imp_qual = unqual2, imp_mods = mods2,
529 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
530 = ImportAvails { imp_env = env1 `plusAvailEnv` env2,
531 imp_qual = plusModuleEnv_C plusAvailEnv unqual1 unqual2,
532 imp_mods = mods1 `plusModuleEnv` mods2,
533 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
534 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
535 imp_orphs = orphs1 `unionLists` orphs2 }
537 plus_mod_dep (m1, boot1) (m2, boot2)
538 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
539 -- Check mod-names match
540 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
543 %************************************************************************
545 Avails, AvailEnv, etc
547 v%************************************************************************
550 plusAvail (Avail n1) (Avail n2) = Avail n1
551 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
554 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
557 -------------------------
558 pruneAvails :: (Name -> Bool) -- Keep if this is True
561 pruneAvails keep avails
562 = mapMaybe del avails
564 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
565 del (Avail n) | keep n = Just (Avail n)
566 | otherwise = Nothing
567 del (AvailTC n ns) | null ns' = Nothing
568 | otherwise = Just (AvailTC n ns')
573 ---------------------------------------
575 ---------------------------------------
578 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
580 emptyAvailEnv :: AvailEnv
581 emptyAvailEnv = emptyNameEnv
583 unitAvailEnv :: AvailInfo -> AvailEnv
584 unitAvailEnv a = unitNameEnv (availName a) a
586 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
587 plusAvailEnv = plusNameEnv_C plusAvail
589 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
590 lookupAvailEnv_maybe = lookupNameEnv
592 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
593 lookupAvailEnv env n = case lookupNameEnv env n of
595 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
597 availEnvElts = nameEnvElts
599 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
600 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
602 mkAvailEnv :: [AvailInfo] -> AvailEnv
603 -- 'avails' may have several items with the same availName
604 -- E.g import Ix( Ix(..), index )
605 -- will give Ix(Ix,index,range) and Ix(index)
606 -- We want to combine these; addAvail does that
607 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
610 %************************************************************************
612 \subsection{Where from}
614 %************************************************************************
616 The @WhereFrom@ type controls where the renamer looks for an interface file
620 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
621 | ImportBySystem -- Non user import.
623 instance Outputable WhereFrom where
624 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
626 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
630 %************************************************************************
632 \subsection[Inst-types]{@Inst@ types}
634 v%************************************************************************
636 An @Inst@ is either a dictionary, an instance of an overloaded
637 literal, or an instance of an overloaded value. We call the latter a
638 ``method'' even though it may not correspond to a class operation.
639 For example, we might have an instance of the @double@ function at
640 type Int, represented by
642 Method 34 doubleId [Int] origin
654 TcId -- The overloaded function
655 -- This function will be a global, local, or ClassOpId;
656 -- inside instance decls (only) it can also be an InstId!
657 -- The id needn't be completely polymorphic.
658 -- You'll probably find its name (for documentation purposes)
659 -- inside the InstOrigin
661 [TcType] -- The types to which its polymorphic tyvars
662 -- should be instantiated.
663 -- These types must saturate the Id's foralls.
665 TcThetaType -- The (types of the) dictionaries to which the function
666 -- must be applied to get the method
668 TcTauType -- The tau-type of the method
672 -- INVARIANT 1: in (Method u f tys theta tau loc)
673 -- type of (f tys dicts(from theta)) = tau
675 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
676 -- Reason: two methods are considered equal if the
677 -- base Id matches, and the instantiating types
678 -- match. The TcThetaType should then match too.
679 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
683 HsOverLit -- The literal from the occurrence site
684 -- INVARIANT: never a rebindable-syntax literal
685 -- Reason: tcSyntaxName does unification, and we
686 -- don't want to deal with that during tcSimplify
687 TcType -- The type at which the literal is used
691 @Insts@ are ordered by their class/type info, rather than by their
692 unique. This allows the context-reduction mechanism to use standard finite
693 maps to do their stuff.
696 instance Ord Inst where
699 instance Eq Inst where
700 (==) i1 i2 = case i1 `cmpInst` i2 of
704 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
705 cmpInst (Dict _ _ _) other = LT
707 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
708 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
709 cmpInst (Method _ _ _ _ _ _) other = LT
711 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
712 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _ _) = GT
713 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
717 %************************************************************************
719 \subsection[Inst-collections]{LIE: a collection of Insts}
721 %************************************************************************
726 isEmptyLIE = isEmptyBag
728 unitLIE inst = unitBag inst
729 mkLIE insts = listToBag insts
730 plusLIE lie1 lie2 = lie1 `unionBags` lie2
731 consLIE inst lie = inst `consBag` lie
732 plusLIEs lies = unionManyBags lies
733 lieToList = bagToList
734 listToLIE = listToBag
738 %************************************************************************
740 \subsection[Inst-origin]{The @InstOrigin@ type}
742 %************************************************************************
744 The @InstOrigin@ type gives information about where a dictionary came from.
745 This is important for decent error message reporting because dictionaries
746 don't appear in the original source code. Doubtless this type will evolve...
748 It appears in TcMonad because there are a couple of error-message-generation
749 functions that deal with it.
752 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
754 instLocSrcLoc :: InstLoc -> SrcLoc
755 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
757 instLocSrcSpan :: InstLoc -> SrcSpan
758 instLocSrcSpan (InstLoc _ src_span _) = src_span
761 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
762 -- Places that bind type variables and introduce
763 -- available constraints
765 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
767 -------------------------------------------------------
768 -- The rest are all occurrences: Insts that are 'wanted'
769 -------------------------------------------------------
770 | OccurrenceOf Name -- Occurrence of an overloaded identifier
772 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
774 | LiteralOrigin HsOverLit -- Occurrence of a literal
776 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
777 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
779 | InstSigOrigin -- A dict occurrence arising from instantiating
780 -- a polymorphic type during a subsumption check
783 | InstScOrigin -- Typechecking superclasses of an instance declaration
784 | DerivOrigin -- Typechecking deriving
785 | DefaultOrigin -- Typechecking a default decl
786 | DoOrigin -- Arising from a do expression
787 | ProcOrigin -- Arising from a proc expression
791 pprInstLoc :: InstLoc -> SDoc
792 pprInstLoc (InstLoc (SigOrigin info) locn _)
793 = text "arising from" <+> ppr info -- I don't think this happens much, if at all
794 pprInstLoc (InstLoc orig locn _)
795 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
797 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
798 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
799 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
800 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
801 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
802 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
803 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
804 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
805 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
806 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
807 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
808 pp_orig DoOrigin = ptext SLIT("a do statement")
809 pp_orig ProcOrigin = ptext SLIT("a proc expression")
810 pp_orig (SigOrigin info) = ppr info