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,
27 ThStage(..), topStage, topSpliceStage,
28 ThLevel, impLevel, topLevel,
31 ArrowCtxt(NoArrowCtxt), newArrowScope, escapeArrowScope,
34 Inst(..), InstOrigin(..), InstLoc(..), pprInstLoc,
35 instLocSrcLoc, instLocSrcSpan,
36 LIE, emptyLIE, unitLIE, plusLIE, consLIE,
37 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
40 TcId, TcIdSet, TcDictBinds
43 #include "HsVersions.h"
45 import HsSyn ( PendingSplice, HsOverLit, LRuleDecl, LForeignDecl,
46 ArithSeqInfo, DictBinds, LHsBinds, LImportDecl, HsGroup,
48 import HscTypes ( FixityEnv,
49 HscEnv, TypeEnv, TyThing,
50 GenAvailInfo(..), AvailInfo, HscSource(..),
51 availName, IsBootInterface, Deprecations )
52 import Packages ( PackageId )
53 import Type ( Type, pprTyThingCategory )
54 import TcType ( TcTyVarSet, TcType, TcThetaType, SkolemInfo, TvSubst,
55 TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes, pprSkolInfo )
56 import InstEnv ( Instance, InstEnv )
58 import RdrName ( GlobalRdrEnv, LocalRdrEnv )
61 import NameSet ( NameSet, unionNameSets, DefUses )
62 import Var ( Id, TyVar )
63 import VarEnv ( TidyEnv )
66 import SrcLoc ( SrcSpan, SrcLoc, Located, srcSpanStart )
67 import VarSet ( IdSet )
68 import ErrUtils ( Messages, Message )
69 import UniqFM ( UniqFM )
70 import UniqSupply ( UniqSupply )
71 import BasicTypes ( IPName )
72 import Util ( thenCmp )
75 import Maybe ( mapMaybe )
76 import ListSetOps ( unionLists )
80 %************************************************************************
82 Standard monad definition for TcRn
83 All the combinators for the monad can be found in TcRnMonad
85 %************************************************************************
87 The monad itself has to be defined here, because it is mentioned by ErrCtxt
90 type TcRef a = IORef a
91 type TcId = Id -- Type may be a TcType
93 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
95 type TcRnIf a b c = IOEnv (Env a b) c
96 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
98 type IfG a = IfM () a -- Top level
99 type IfL a = IfM IfLclEnv a -- Nested
100 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
101 type RnM a = TcRn a -- Historical
102 type TcM a = TcRn a -- Historical
106 %************************************************************************
108 The main environment types
110 %************************************************************************
113 data Env gbl lcl -- Changes as we move into an expression
115 env_top :: HscEnv, -- Top-level stuff that never changes
116 -- Includes all info about imported things
118 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
119 -- Unique supply for local varibles
121 env_gbl :: gbl, -- Info about things defined at the top level
122 -- of the module being compiled
124 env_lcl :: lcl -- Nested stuff; changes as we go into
128 -- TcGblEnv describes the top-level of the module at the
129 -- point at which the typechecker is finished work.
130 -- It is this structure that is handed on to the desugarer
134 tcg_mod :: Module, -- Module being compiled
135 tcg_src :: HscSource, -- What kind of module
136 -- (regular Haskell, hs-boot, ext-core)
138 tcg_rdr_env :: GlobalRdrEnv, -- Top level envt; used during renaming
139 tcg_default :: Maybe [Type], -- Types used for defaulting
140 -- Nothing => no 'default' decl
142 tcg_fix_env :: FixityEnv, -- Just for things in this module
144 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
145 -- All TyCons and Classes (for this module) end up in here right away,
146 -- along with their derived constructors, selectors.
148 -- (Ids defined in this module start in the local envt,
149 -- though they move to the global envt during zonking)
151 tcg_type_env_var :: TcRef TypeEnv,
152 -- Used only to initialise the interface-file
153 -- typechecker in initIfaceTcRn, so that it can see stuff
154 -- bound in this module when dealing with hi-boot recursions
155 -- Updated at intervals (e.g. after dealing with types and classes)
157 tcg_inst_env :: InstEnv, -- Instance envt for *home-package* modules
158 -- Includes the dfuns in tcg_insts
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 :: NameSet, -- What is exported
164 tcg_imports :: ImportAvails, -- Information about what was imported
165 -- from where, including things bound
168 tcg_dus :: DefUses, -- What is defined in this module and what is used.
169 -- The latter is used to generate
170 -- (a) version tracking; no need to recompile if these
171 -- things have not changed version stamp
172 -- (b) unused-import info
174 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
175 -- "Keep alive" means give them an Exported flag, so
176 -- that the simplifier does not discard them as dead
177 -- code, and so that they are exposed in the interface file
178 -- (but not to export to the user).
180 -- Some things, like dict-fun Ids and default-method Ids are
181 -- "born" with the Exported flag on, for exactly the above reason,
182 -- but some we only discover as we go. Specifically:
183 -- * The to/from functions for generic data types
184 -- * Top-level variables appearing free in the RHS of an orphan rule
185 -- * Top-level variables appearing free in a TH bracket
187 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
188 -- Used to generate version dependencies
189 -- This records usages, rather like tcg_dus, but it has to
190 -- be a mutable variable so it can be augmented
191 -- when we look up an instance. These uses of dfuns are
192 -- rather like the free variables of the program, but
193 -- are implicit instead of explicit.
195 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
196 -- We need this so that we can generate a dependency on the
197 -- Template Haskell package, becuase the desugarer is going to
198 -- emit loads of references to TH symbols. It's rather like
199 -- tcg_inst_uses; the reference is implicit rather than explicit,
200 -- so we have to zap a mutable variable.
202 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
203 -- It's convenient to allocate an External Name for a DFun, with
204 -- a permanently-fixed unique, just like other top-level functions
205 -- defined in this module. But that means we need a canonical
206 -- occurrence name, distinct from all other dfuns in this module,
207 -- and this name supply serves that purpose (df1, df2, etc).
209 -- The next fields accumulate the payload of the module
210 -- The binds, rules and foreign-decl fiels are collected
211 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
213 -- The next fields accumulate the payload of the
214 -- module The binds, rules and foreign-decl fiels are
215 -- collected initially in un-zonked form and are
216 -- finally zonked in tcRnSrcDecls
218 tcg_rn_imports :: Maybe [LImportDecl Name],
219 tcg_rn_exports :: Maybe [Located (IE Name)],
220 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
221 -- Nothing <=> Don't retain renamed decls
223 tcg_binds :: LHsBinds Id, -- Value bindings in this module
224 tcg_deprecs :: Deprecations, -- ...Deprecations
225 tcg_insts :: [Instance], -- ...Instances
226 tcg_rules :: [LRuleDecl Id], -- ...Rules
227 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
231 %************************************************************************
233 The interface environments
234 Used when dealing with IfaceDecls
236 %************************************************************************
241 -- The type environment for the module being compiled,
242 -- in case the interface refers back to it via a reference that
243 -- was originally a hi-boot file.
244 -- We need the module name so we can test when it's appropriate
245 -- to look in this env.
246 if_rec_types :: Maybe (Module, IfG TypeEnv)
247 -- Allows a read effect, so it can be in a mutable
248 -- variable; c.f. handling the external package type env
249 -- Nothing => interactive stuff, no loops possible
254 -- The module for the current IfaceDecl
255 -- So if we see f = \x -> x
256 -- it means M.f = \x -> x, where M is the if_mod
259 -- The field is used only for error reporting
260 -- if (say) there's a Lint error in it
262 -- Where the interface came from:
263 -- .hi file, or GHCi state, or ext core
264 -- plus which bit is currently being examined
266 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
267 if_id_env :: UniqFM Id -- Nested id binding
272 %************************************************************************
274 The local typechecker environment
276 %************************************************************************
278 The Global-Env/Local-Env story
279 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
280 During type checking, we keep in the tcg_type_env
281 * All types and classes
282 * All Ids derived from types and classes (constructors, selectors)
284 At the end of type checking, we zonk the local bindings,
285 and as we do so we add to the tcg_type_env
286 * Locally defined top-level Ids
288 Why? Because they are now Ids not TcIds. This final GlobalEnv is
289 a) fed back (via the knot) to typechecking the
290 unfoldings of interface signatures
291 b) used in the ModDetails of this module
294 data TcLclEnv -- Changes as we move inside an expression
295 -- Discarded after typecheck/rename; not passed on to desugarer
297 tcl_loc :: SrcSpan, -- Source span
298 tcl_ctxt :: ErrCtxt, -- Error context
299 tcl_errs :: TcRef Messages, -- Place to accumulate errors
301 tcl_th_ctxt :: ThStage, -- Template Haskell context
302 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
304 tcl_rdr :: LocalRdrEnv, -- Local name envt
305 -- Maintained during renaming, of course, but also during
306 -- type checking, solely so that when renaming a Template-Haskell
307 -- splice we have the right environment for the renamer.
309 -- Does *not* include global name envt; may shadow it
310 -- Includes both ordinary variables and type variables;
311 -- they are kept distinct because tyvar have a different
312 -- occurrence contructor (Name.TvOcc)
313 -- We still need the unsullied global name env so that
314 -- we can look up record field names
316 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
317 -- defined in this module
319 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
320 -- Namely, the in-scope TyVars bound in tcl_env,
321 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
322 -- Why mutable? see notes with tcGetGlobalTyVars
324 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
327 type GadtRefinement = TvSubst
329 {- Note [Given Insts]
331 Because of GADTs, we have to pass inwards the Insts provided by type signatures
332 and existential contexts. Consider
333 data T a where { T1 :: b -> b -> T [b] }
334 f :: Eq a => T a -> Bool
335 f (T1 x y) = [x]==[y]
337 The constructor T1 binds an existential variable 'b', and we need Eq [b].
338 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
343 ---------------------------
344 -- Template Haskell levels
345 ---------------------------
348 -- Indicates how many levels of brackets we are inside
350 -- Incremented when going inside a bracket,
351 -- decremented when going inside a splice
352 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
353 -- original "Template meta-programmign for Haskell" paper
355 impLevel, topLevel :: ThLevel
356 topLevel = 1 -- Things defined at top level of this module
357 impLevel = 0 -- Imported things; they can be used inside a top level splice
361 -- g1 = $(map ...) is OK
362 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
366 = Comp -- Ordinary compiling, at level topLevel
367 | Splice ThLevel -- Inside a splice
368 | Brack ThLevel -- Inside brackets;
369 (TcRef [PendingSplice]) -- accumulate pending splices here
370 (TcRef LIE) -- and type constraints here
371 topStage, topSpliceStage :: ThStage
373 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
375 ---------------------------
376 -- Arrow-notation context
377 ---------------------------
380 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
381 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
386 Here, x is not in scope in e1, but it is in scope in e2. This can get
390 proc y -> (proc z -> e1) -< e2
392 Here, x and z are in scope in e1, but y is not. We implement this by
393 recording the environment when passing a proc (using newArrowScope),
394 and returning to that (using escapeArrowScope) on the left of -< and the
400 | ArrowCtxt (Env TcGblEnv TcLclEnv)
402 -- Record the current environment (outside a proc)
403 newArrowScope :: TcM a -> TcM a
406 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
408 -- Return to the stored environment (from the enclosing proc)
409 escapeArrowScope :: TcM a -> TcM a
411 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
413 ArrowCtxt env' -> env'
415 ---------------------------
417 ---------------------------
420 = AGlobal TyThing -- Used only in the return type of a lookup
422 | ATcId TcId -- Ids defined in this module; may not be fully zonked
424 Bool -- True <=> apply the type refinement to me
426 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
427 -- is currently refined. We only need the Name
428 -- for error-message purposes
430 | AThing TcKind -- Used temporarily, during kind checking, for the
431 -- tycons and clases in this recursive group
433 instance Outputable TcTyThing where -- Debugging only
434 ppr (AGlobal g) = ppr g
435 ppr (ATcId g tl rig) = text "Identifier" <>
436 ifPprDebug (brackets (ppr g <> comma <> ppr tl <+> ppr rig))
437 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
438 ppr (AThing k) = text "AThing" <+> ppr k
440 pprTcTyThingCategory :: TcTyThing -> SDoc
441 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
442 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
443 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
444 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
448 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
449 -- Innermost first. Monadic so that we have a chance
450 -- to deal with bound type variables just before error
451 -- message construction
455 %************************************************************************
457 Operations over ImportAvails
459 %************************************************************************
461 ImportAvails summarises what was imported from where, irrespective
462 of whether the imported things are actually used or not
463 It is used * when processing the export list
464 * when constructing usage info for the inteface file
465 * to identify the list of directly imported modules
466 for initialisation purposes
467 * when figuring out what things are really unused
472 imp_env :: ModuleNameEnv NameSet,
473 -- All the things imported, classified by
474 -- the *module qualifier* for its import
475 -- e.g. import List as Foo
476 -- would add a binding Foo |-> ...stuff from List...
479 -- We need to classify them like this so that we can figure out
480 -- "module M" export specifiers in an export list
481 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
482 -- everything that is unambiguously in scope as 'M.x'
483 -- and where plain 'x' is (perhaps ambiguously) in scope.
484 -- So the starting point is all things that are in scope as 'M.x',
485 -- which is what this field tells us.
487 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
488 -- Domain is all directly-imported modules
490 -- True => import was "import Foo ()"
491 -- False => import was some other form
493 -- We need the Module in the range because we can't get
494 -- the keys of a ModuleEnv
496 -- (a) to help construct the usage information in
497 -- the interface file; if we import somethign we
498 -- need to recompile if the export version changes
499 -- (b) to specify what child modules to initialise
501 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
502 -- Home-package modules needed by the module being compiled
504 -- It doesn't matter whether any of these dependencies
505 -- are actually *used* when compiling the module; they
506 -- are listed if they are below it at all. For
507 -- example, suppose M imports A which imports X. Then
508 -- compiling M might not need to consult X.hi, but X
509 -- is still listed in M's dependencies.
511 imp_dep_pkgs :: [PackageId],
512 -- Packages needed by the module being compiled, whether
513 -- directly, or via other modules in this package, or via
514 -- modules imported from other packages.
516 imp_orphs :: [Module]
517 -- Orphan modules below us in the import tree
520 mkModDeps :: [(ModuleName, IsBootInterface)]
521 -> ModuleNameEnv (ModuleName, IsBootInterface)
522 mkModDeps deps = foldl add emptyUFM deps
524 add env elt@(m,_) = addToUFM env m elt
526 emptyImportAvails :: ImportAvails
527 emptyImportAvails = ImportAvails { imp_env = emptyUFM,
528 imp_mods = emptyModuleEnv,
529 imp_dep_mods = emptyUFM,
533 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
535 (ImportAvails { imp_env = env1, imp_mods = mods1,
536 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
537 (ImportAvails { imp_env = env2, imp_mods = mods2,
538 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
539 = ImportAvails { imp_env = plusUFM_C unionNameSets env1 env2,
540 imp_mods = mods1 `plusModuleEnv` mods2,
541 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
542 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
543 imp_orphs = orphs1 `unionLists` orphs2 }
545 plus_mod_dep (m1, boot1) (m2, boot2)
546 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
547 -- Check mod-names match
548 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
551 %************************************************************************
553 Avails, AvailEnv, etc
555 v%************************************************************************
558 plusAvail (Avail n1) (Avail n2) = Avail n1
559 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
562 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
565 -------------------------
566 pruneAvails :: (Name -> Bool) -- Keep if this is True
569 pruneAvails keep avails
570 = mapMaybe del avails
572 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
573 del (Avail n) | keep n = Just (Avail n)
574 | otherwise = Nothing
575 del (AvailTC n ns) | null ns' = Nothing
576 | otherwise = Just (AvailTC n ns')
581 ---------------------------------------
583 ---------------------------------------
586 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
588 emptyAvailEnv :: AvailEnv
589 emptyAvailEnv = emptyNameEnv
591 unitAvailEnv :: AvailInfo -> AvailEnv
592 unitAvailEnv a = unitNameEnv (availName a) a
594 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
595 plusAvailEnv = plusNameEnv_C plusAvail
597 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
598 lookupAvailEnv_maybe = lookupNameEnv
600 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
601 lookupAvailEnv env n = case lookupNameEnv env n of
603 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
605 availEnvElts = nameEnvElts
607 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
608 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
610 mkAvailEnv :: [AvailInfo] -> AvailEnv
611 -- 'avails' may have several items with the same availName
612 -- E.g import Ix( Ix(..), index )
613 -- will give Ix(Ix,index,range) and Ix(index)
614 -- We want to combine these; addAvail does that
615 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
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
662 TcId -- The overloaded function
663 -- This function will be a global, local, or ClassOpId;
664 -- inside instance decls (only) it can also be an InstId!
665 -- The id needn't be completely polymorphic.
666 -- You'll probably find its name (for documentation purposes)
667 -- inside the InstOrigin
669 [TcType] -- The types to which its polymorphic tyvars
670 -- should be instantiated.
671 -- These types must saturate the Id's foralls.
673 TcThetaType -- The (types of the) dictionaries to which the function
674 -- must be applied to get the method
678 -- INVARIANT 1: in (Method u f tys theta tau loc)
679 -- type of (f tys dicts(from theta)) = tau
681 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
682 -- Reason: two methods are considered equal if the
683 -- base Id matches, and the instantiating types
684 -- match. The TcThetaType should then match too.
685 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
689 (HsOverLit Name) -- The literal from the occurrence site
690 -- INVARIANT: never a rebindable-syntax literal
691 -- Reason: tcSyntaxName does unification, and we
692 -- don't want to deal with that during tcSimplify,
693 -- when resolving LitInsts
694 TcType -- The type at which the literal is used
698 @Insts@ are ordered by their class/type info, rather than by their
699 unique. This allows the context-reduction mechanism to use standard finite
700 maps to do their stuff.
703 instance Ord Inst where
706 instance Eq Inst where
707 (==) i1 i2 = case i1 `cmpInst` i2 of
711 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
712 cmpInst (Dict _ _ _) other = LT
714 cmpInst (Method _ _ _ _ _) (Dict _ _ _) = GT
715 cmpInst (Method _ id1 tys1 _ _) (Method _ id2 tys2 _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
716 cmpInst (Method _ _ _ _ _) other = LT
718 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
719 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _) = GT
720 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
724 %************************************************************************
726 \subsection[Inst-collections]{LIE: a collection of Insts}
728 %************************************************************************
731 -- FIXME: Rename this. It clashes with (Located (IE ...))
734 isEmptyLIE = isEmptyBag
736 unitLIE inst = unitBag inst
737 mkLIE insts = listToBag insts
738 plusLIE lie1 lie2 = lie1 `unionBags` lie2
739 consLIE inst lie = inst `consBag` lie
740 plusLIEs lies = unionManyBags lies
741 lieToList = bagToList
742 listToLIE = listToBag
746 %************************************************************************
748 \subsection[Inst-origin]{The @InstOrigin@ type}
750 %************************************************************************
752 The @InstOrigin@ type gives information about where a dictionary came from.
753 This is important for decent error message reporting because dictionaries
754 don't appear in the original source code. Doubtless this type will evolve...
756 It appears in TcMonad because there are a couple of error-message-generation
757 functions that deal with it.
760 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
762 instLocSrcLoc :: InstLoc -> SrcLoc
763 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
765 instLocSrcSpan :: InstLoc -> SrcSpan
766 instLocSrcSpan (InstLoc _ src_span _) = src_span
769 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
770 -- Places that bind type variables and introduce
771 -- available constraints
773 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
775 -------------------------------------------------------
776 -- The rest are all occurrences: Insts that are 'wanted'
777 -------------------------------------------------------
778 | OccurrenceOf Name -- Occurrence of an overloaded identifier
780 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
782 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
784 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
785 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
787 | InstSigOrigin -- A dict occurrence arising from instantiating
788 -- a polymorphic type during a subsumption check
791 | InstScOrigin -- Typechecking superclasses of an instance declaration
792 | DerivOrigin -- Typechecking deriving
793 | DefaultOrigin -- Typechecking a default decl
794 | DoOrigin -- Arising from a do expression
795 | ProcOrigin -- Arising from a proc expression
799 pprInstLoc :: InstLoc -> SDoc
800 pprInstLoc (InstLoc orig locn _)
801 = sep [text "arising from" <+> pp_orig orig,
802 text "at" <+> ppr locn]
804 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
805 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
806 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
807 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
808 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
809 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
810 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
811 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
812 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
813 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
814 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
815 pp_orig DoOrigin = ptext SLIT("a do statement")
816 pp_orig ProcOrigin = ptext SLIT("a proc expression")
817 pp_orig (SigOrigin info) = pprSkolInfo info