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 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, HscSource(..),
49 availName, IsBootInterface, Deprecations )
50 import Packages ( PackageId )
51 import Type ( Type, TvSubstEnv, pprParendType, pprTyThingCategory )
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, unionNameSets, 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_src :: HscSource, -- What kind of module
133 -- (regular Haskell, hs-boot, ext-core)
135 tcg_rdr_env :: GlobalRdrEnv, -- Top level envt; used during renaming
136 tcg_default :: Maybe [Type], -- Types used for defaulting
137 -- Nothing => no 'default' decl
139 tcg_fix_env :: FixityEnv, -- Just for things in this module
141 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
142 -- All 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,
146 -- though they 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, -- Instance envt for *home-package* modules
155 -- Includes the dfuns in tcg_insts
156 -- Now a bunch of things about this module that are simply
157 -- accumulated, but never consulted until the end.
158 -- Nevertheless, it's convenient to accumulate them along
159 -- with the rest of the info from this module.
160 tcg_exports :: NameSet, -- What is exported
161 tcg_imports :: ImportAvails, -- Information about what was imported
162 -- from where, including things bound
165 tcg_dus :: DefUses, -- What is defined in this module and what is used.
166 -- The latter is used to generate
167 -- (a) version tracking; no need to recompile if these
168 -- things have not changed version stamp
169 -- (b) unused-import info
171 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
172 -- "Keep alive" means give them an Exported flag, so
173 -- that the simplifier does not discard them as dead
174 -- code, and so that they are exposed in the interface file
175 -- (but not to export to the user).
177 -- Some things, like dict-fun Ids and default-method Ids are
178 -- "born" with the Exported flag on, for exactly the above reason,
179 -- but some we only discover as we go. Specifically:
180 -- * The to/from functions for generic data types
181 -- * Top-level variables appearing free in the RHS of an orphan rule
182 -- * Top-level variables appearing free in a TH bracket
184 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
185 -- Used to generate version dependencies
186 -- This records usages, rather like tcg_dus, but it has to
187 -- be a mutable variable so it can be augmented
188 -- when we look up an instance. These uses of dfuns are
189 -- rather like the free variables of the program, but
190 -- are implicit instead of explicit.
192 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
193 -- We need this so that we can generate a dependency on the
194 -- Template Haskell package, becuase the desugarer is going to
195 -- emit loads of references to TH symbols. It's rather like
196 -- tcg_inst_uses; the reference is implicit rather than explicit,
197 -- so we have to zap a mutable variable.
199 -- The next fields accumulate the payload of the module
200 -- The binds, rules and foreign-decl fiels are collected
201 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
202 tcg_binds :: LHsBinds Id, -- Value bindings in this module
203 tcg_deprecs :: Deprecations, -- ...Deprecations
204 tcg_insts :: [DFunId], -- ...Instances
205 tcg_rules :: [LRuleDecl Id], -- ...Rules
206 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
210 %************************************************************************
212 The interface environments
213 Used when dealing with IfaceDecls
215 %************************************************************************
220 -- The type environment for the module being compiled,
221 -- in case the interface refers back to it via a reference that
222 -- was originally a hi-boot file.
223 -- We need the module name so we can test when it's appropriate
224 -- to look in this env.
225 if_rec_types :: Maybe (Module, IfG TypeEnv)
226 -- Allows a read effect, so it can be in a mutable
227 -- variable; c.f. handling the external package type env
228 -- Nothing => interactive stuff, no loops possible
233 -- The module for the current IfaceDecl
234 -- So if we see f = \x -> x
235 -- it means M.f = \x -> x, where M is the if_mod
238 -- The field is used only for error reporting
239 -- if (say) there's a Lint error in it
241 -- Where the interface came from:
242 -- .hi file, or GHCi state, or ext core
243 -- plus which bit is currently being examined
245 if_tv_env :: OccEnv TyVar, -- Nested tyvar bindings
246 if_id_env :: OccEnv Id -- Nested id binding
251 %************************************************************************
253 The local typechecker environment
255 %************************************************************************
257 The Global-Env/Local-Env story
258 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
259 During type checking, we keep in the tcg_type_env
260 * All types and classes
261 * All Ids derived from types and classes (constructors, selectors)
263 At the end of type checking, we zonk the local bindings,
264 and as we do so we add to the tcg_type_env
265 * Locally defined top-level Ids
267 Why? Because they are now Ids not TcIds. This final GlobalEnv is
268 a) fed back (via the knot) to typechecking the
269 unfoldings of interface signatures
270 b) used in the ModDetails of this module
273 data TcLclEnv -- Changes as we move inside an expression
274 -- Discarded after typecheck/rename; not passed on to desugarer
276 tcl_loc :: SrcSpan, -- Source span
277 tcl_ctxt :: ErrCtxt, -- Error context
278 tcl_errs :: TcRef Messages, -- Place to accumulate errors
280 tcl_th_ctxt :: ThStage, -- Template Haskell context
281 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
283 tcl_rdr :: LocalRdrEnv, -- Local name envt
284 -- Maintained during renaming, of course, but also during
285 -- type checking, solely so that when renaming a Template-Haskell
286 -- splice we have the right environment for the renamer.
288 -- Does *not* include global name envt; may shadow it
289 -- Includes both ordinary variables and type variables;
290 -- they are kept distinct because tyvar have a different
291 -- occurrence contructor (Name.TvOcc)
292 -- We still need the unsullied global name env so that
293 -- we can look up record field names
295 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
296 -- defined in this module
298 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
299 -- Namely, the in-scope TyVars bound in tcl_env,
300 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
301 -- Why mutable? see notes with tcGetGlobalTyVars
303 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
304 tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
306 -----------------------------------------------------------
307 -- Not yet; it's a new complication and I want to see whether it bites
308 -- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
309 -----------------------------------------------------------
312 type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
314 {- Note [Given Insts]
316 Because of GADTs, we have to pass inwards the Insts provided by type signatures
317 and existential contexts. Consider
318 data T a where { T1 :: b -> b -> T [b] }
319 f :: Eq a => T a -> Bool
320 f (T1 x y) = [x]==[y]
322 The constructor T1 binds an existential variable 'b', and we need Eq [b].
323 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
328 ---------------------------
329 -- Template Haskell levels
330 ---------------------------
333 -- Indicates how many levels of brackets we are inside
335 -- Incremented when going inside a bracket,
336 -- decremented when going inside a splice
338 impLevel, topLevel :: ThLevel
339 topLevel = 1 -- Things defined at top level of this module
340 impLevel = 0 -- Imported things; they can be used inside a top level splice
344 -- g1 = $(map ...) is OK
345 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
349 = Comp -- Ordinary compiling, at level topLevel
350 | Splice ThLevel -- Inside a splice
351 | Brack ThLevel -- Inside brackets;
352 (TcRef [PendingSplice]) -- accumulate pending splices here
353 (TcRef LIE) -- and type constraints here
354 topStage, topSpliceStage :: ThStage
356 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
359 ---------------------------
360 -- Arrow-notation stages
361 ---------------------------
363 -- In arrow notation, a variable bound by a proc (or enclosed let/kappa)
364 -- is not in scope to the left of an arrow tail (-<). For example
366 -- proc x -> (e1 -< e2)
368 -- Here, x is not in scope in e1, but it is in scope in e2. This can get
369 -- a bit complicated:
372 -- prox y -> (proc z -> e1) -< e2
374 -- Here, x and z are in scope in e1, but y is not. Here's how we track this:
375 -- a) Assign an "proc level" to each proc, being the number of
376 -- lexically-enclosing procs + 1.
377 -- b) Assign to each local variable the proc-level of its lexically
379 -- c) Keep a list of out-of-scope procs. When moving to the left of
380 -- an arrow-tail, add the proc-level of the immediately enclosing
382 -- d) When looking up a variable, complain if its proc-level is in
385 type ProcLevel = Int -- Always >= 0
386 topProcLevel = 0 -- Not inside any proc
388 data ArrowCtxt = ArrCtxt { proc_level :: ProcLevel, -- Current level
389 proc_banned :: [ProcLevel] } -- Out of scope proc-levels
391 topArrowCtxt = ArrCtxt { proc_level = topProcLevel, proc_banned = [] }
393 ---------------------------
395 ---------------------------
398 = AGlobal TyThing -- Used only in the return type of a lookup
400 | ATcId TcId ThLevel ProcLevel -- Ids defined in this module; may not be fully zonked
402 | ATyVar Name TcType -- Type variables; tv -> type. It can't just be a TyVar
403 -- that is mutated to point to the type it is bound to,
404 -- because that would make it a wobbly type, and we
405 -- want pattern-bound lexically-scoped type variables to
406 -- be able to stand for rigid types
408 | AThing TcKind -- Used temporarily, during kind checking, for the
409 -- tycons and clases in this recursive group
411 instance Outputable TcTyThing where -- Debugging only
412 ppr (AGlobal g) = ppr g
413 ppr (ATcId g tl pl) = text "Identifier" <>
414 ifPprDebug (brackets (ppr g <> comma <> ppr tl <> comma <> ppr pl))
415 ppr (ATyVar tv ty) = text "Type variable" <+> quotes (ppr tv) <+> pprParendType ty
416 ppr (AThing k) = text "AThing" <+> ppr k
418 pprTcTyThingCategory :: TcTyThing -> SDoc
419 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
420 pprTcTyThingCategory (ATyVar _ _) = ptext SLIT("Type variable")
421 pprTcTyThingCategory (ATcId _ _ _) = ptext SLIT("Local identifier")
422 pprTcTyThingCategory (AThing _) = ptext SLIT("Kinded thing")
426 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
427 -- Innermost first. Monadic so that we have a chance
428 -- to deal with bound type variables just before error
429 -- message construction
433 %************************************************************************
435 Operations over ImportAvails
437 %************************************************************************
439 ImportAvails summarises what was imported from where, irrespective
440 of whether the imported things are actually used or not
441 It is used * when processing the export list
442 * when constructing usage info for the inteface file
443 * to identify the list of directly imported modules
444 for initialisation purposes
445 * when figuring out what things are really unused
450 imp_env :: ModuleEnv NameSet,
451 -- All the things imported, classified by
452 -- the *module qualifier* for its import
453 -- e.g. import List as Foo
454 -- would add a binding Foo |-> ...stuff from List...
457 -- We need to classify them like this so that we can figure out
458 -- "module M" export specifiers in an export list
459 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
460 -- everything that is unambiguously in scope as 'M.x'
461 -- and where plain 'x' is (perhaps ambiguously) in scope.
462 -- So the starting point is all things that are in scope as 'M.x',
463 -- which is what this field tells us.
465 imp_mods :: ModuleEnv (Module, Maybe Bool, SrcSpan),
466 -- Domain is all directly-imported modules
467 -- Maybe value answers the question "is the import restricted?"
468 -- Nothing => unrestricted import (e.g., "import Foo")
469 -- Just True => restricted import, at least one entity (e.g., "import Foo(x)")
470 -- Just False => fully restricted import (e.g., "import Foo ()")
472 -- A distinction is made between the first and the third in order
473 -- to more precisely emit warnings about unused imports.
475 -- We need the Module in the range because we can't get
476 -- the keys of a ModuleEnv
478 -- (a) to help construct the usage information in
479 -- the interface file; if we import everything we
480 -- need to recompile if the module version changes
481 -- (b) to specify what child modules to initialise
483 imp_dep_mods :: ModuleEnv (Module, IsBootInterface),
484 -- Home-package modules needed by the module being compiled
486 -- It doesn't matter whether any of these dependencies
487 -- are actually *used* when compiling the module; they
488 -- are listed if they are below it at all. For
489 -- example, suppose M imports A which imports X. Then
490 -- compiling M might not need to consult X.hi, but X
491 -- is still listed in M's dependencies.
493 imp_dep_pkgs :: [PackageId],
494 -- Packages needed by the module being compiled, whether
495 -- directly, or via other modules in this package, or via
496 -- modules imported from other packages.
498 imp_orphs :: [Module]
499 -- Orphan modules below us in the import tree
502 mkModDeps :: [(Module, IsBootInterface)]
503 -> ModuleEnv (Module, IsBootInterface)
504 mkModDeps deps = foldl add emptyModuleEnv deps
506 add env elt@(m,_) = extendModuleEnv env m elt
508 emptyImportAvails :: ImportAvails
509 emptyImportAvails = ImportAvails { imp_env = emptyModuleEnv,
510 imp_mods = emptyModuleEnv,
511 imp_dep_mods = emptyModuleEnv,
515 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
517 (ImportAvails { imp_env = env1, imp_mods = mods1,
518 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
519 (ImportAvails { imp_env = env2, imp_mods = mods2,
520 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
521 = ImportAvails { imp_env = plusModuleEnv_C unionNameSets env1 env2,
522 imp_mods = mods1 `plusModuleEnv` mods2,
523 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
524 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
525 imp_orphs = orphs1 `unionLists` orphs2 }
527 plus_mod_dep (m1, boot1) (m2, boot2)
528 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
529 -- Check mod-names match
530 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
533 %************************************************************************
535 Avails, AvailEnv, etc
537 v%************************************************************************
540 plusAvail (Avail n1) (Avail n2) = Avail n1
541 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
544 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
547 -------------------------
548 pruneAvails :: (Name -> Bool) -- Keep if this is True
551 pruneAvails keep avails
552 = mapMaybe del avails
554 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
555 del (Avail n) | keep n = Just (Avail n)
556 | otherwise = Nothing
557 del (AvailTC n ns) | null ns' = Nothing
558 | otherwise = Just (AvailTC n ns')
563 ---------------------------------------
565 ---------------------------------------
568 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
570 emptyAvailEnv :: AvailEnv
571 emptyAvailEnv = emptyNameEnv
573 unitAvailEnv :: AvailInfo -> AvailEnv
574 unitAvailEnv a = unitNameEnv (availName a) a
576 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
577 plusAvailEnv = plusNameEnv_C plusAvail
579 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
580 lookupAvailEnv_maybe = lookupNameEnv
582 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
583 lookupAvailEnv env n = case lookupNameEnv env n of
585 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
587 availEnvElts = nameEnvElts
589 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
590 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
592 mkAvailEnv :: [AvailInfo] -> AvailEnv
593 -- 'avails' may have several items with the same availName
594 -- E.g import Ix( Ix(..), index )
595 -- will give Ix(Ix,index,range) and Ix(index)
596 -- We want to combine these; addAvail does that
597 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
600 %************************************************************************
602 \subsection{Where from}
604 %************************************************************************
606 The @WhereFrom@ type controls where the renamer looks for an interface file
610 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
611 | ImportBySystem -- Non user import.
613 instance Outputable WhereFrom where
614 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
616 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
620 %************************************************************************
622 \subsection[Inst-types]{@Inst@ types}
624 v%************************************************************************
626 An @Inst@ is either a dictionary, an instance of an overloaded
627 literal, or an instance of an overloaded value. We call the latter a
628 ``method'' even though it may not correspond to a class operation.
629 For example, we might have an instance of the @double@ function at
630 type Int, represented by
632 Method 34 doubleId [Int] origin
644 TcId -- The overloaded function
645 -- This function will be a global, local, or ClassOpId;
646 -- inside instance decls (only) it can also be an InstId!
647 -- The id needn't be completely polymorphic.
648 -- You'll probably find its name (for documentation purposes)
649 -- inside the InstOrigin
651 [TcType] -- The types to which its polymorphic tyvars
652 -- should be instantiated.
653 -- These types must saturate the Id's foralls.
655 TcThetaType -- The (types of the) dictionaries to which the function
656 -- must be applied to get the method
658 TcTauType -- The tau-type of the method
662 -- INVARIANT 1: in (Method u f tys theta tau loc)
663 -- type of (f tys dicts(from theta)) = tau
665 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
666 -- Reason: two methods are considered equal if the
667 -- base Id matches, and the instantiating types
668 -- match. The TcThetaType should then match too.
669 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
673 HsOverLit -- The literal from the occurrence site
674 -- INVARIANT: never a rebindable-syntax literal
675 -- Reason: tcSyntaxName does unification, and we
676 -- don't want to deal with that during tcSimplify
677 TcType -- The type at which the literal is used
681 @Insts@ are ordered by their class/type info, rather than by their
682 unique. This allows the context-reduction mechanism to use standard finite
683 maps to do their stuff.
686 instance Ord Inst where
689 instance Eq Inst where
690 (==) i1 i2 = case i1 `cmpInst` i2 of
694 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
695 cmpInst (Dict _ _ _) other = LT
697 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
698 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
699 cmpInst (Method _ _ _ _ _ _) other = LT
701 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
702 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _ _) = GT
703 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
707 %************************************************************************
709 \subsection[Inst-collections]{LIE: a collection of Insts}
711 %************************************************************************
716 isEmptyLIE = isEmptyBag
718 unitLIE inst = unitBag inst
719 mkLIE insts = listToBag insts
720 plusLIE lie1 lie2 = lie1 `unionBags` lie2
721 consLIE inst lie = inst `consBag` lie
722 plusLIEs lies = unionManyBags lies
723 lieToList = bagToList
724 listToLIE = listToBag
728 %************************************************************************
730 \subsection[Inst-origin]{The @InstOrigin@ type}
732 %************************************************************************
734 The @InstOrigin@ type gives information about where a dictionary came from.
735 This is important for decent error message reporting because dictionaries
736 don't appear in the original source code. Doubtless this type will evolve...
738 It appears in TcMonad because there are a couple of error-message-generation
739 functions that deal with it.
742 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
744 instLocSrcLoc :: InstLoc -> SrcLoc
745 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
747 instLocSrcSpan :: InstLoc -> SrcSpan
748 instLocSrcSpan (InstLoc _ src_span _) = src_span
751 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
752 -- Places that bind type variables and introduce
753 -- available constraints
755 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
757 -------------------------------------------------------
758 -- The rest are all occurrences: Insts that are 'wanted'
759 -------------------------------------------------------
760 | OccurrenceOf Name -- Occurrence of an overloaded identifier
762 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
764 | LiteralOrigin HsOverLit -- Occurrence of a literal
766 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
767 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
769 | InstSigOrigin -- A dict occurrence arising from instantiating
770 -- a polymorphic type during a subsumption check
773 | InstScOrigin -- Typechecking superclasses of an instance declaration
774 | DerivOrigin -- Typechecking deriving
775 | DefaultOrigin -- Typechecking a default decl
776 | DoOrigin -- Arising from a do expression
777 | ProcOrigin -- Arising from a proc expression
781 pprInstLoc :: InstLoc -> SDoc
782 pprInstLoc (InstLoc (SigOrigin info) locn _)
783 = text "arising from" <+> ppr info -- I don't think this happens much, if at all
784 pprInstLoc (InstLoc orig locn _)
785 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
787 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
788 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
789 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
790 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
791 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
792 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
793 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
794 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
795 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
796 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
797 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
798 pp_orig DoOrigin = ptext SLIT("a do statement")
799 pp_orig ProcOrigin = ptext SLIT("a proc expression")
800 pp_orig (SigOrigin info) = ppr info