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 ( DFunId, 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 -- The next fields accumulate the payload of the
197 -- module The binds, rules and foreign-decl fiels are
198 -- collected initially in un-zonked form and are
199 -- finally zonked in tcRnSrcDecls
201 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
202 -- Nothing <=> Don't retain renamed decls
204 tcg_binds :: LHsBinds Id, -- Value bindings in this module
205 tcg_deprecs :: Deprecations, -- ...Deprecations
206 tcg_insts :: [DFunId], -- ...Instances
207 tcg_rules :: [LRuleDecl Id], -- ...Rules
208 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
212 %************************************************************************
214 The interface environments
215 Used when dealing with IfaceDecls
217 %************************************************************************
222 -- The type environment for the module being compiled,
223 -- in case the interface refers back to it via a reference that
224 -- was originally a hi-boot file.
225 -- We need the module name so we can test when it's appropriate
226 -- to look in this env.
227 if_rec_types :: Maybe (Module, IfG TypeEnv)
228 -- Allows a read effect, so it can be in a mutable
229 -- variable; c.f. handling the external package type env
230 -- Nothing => interactive stuff, no loops possible
235 -- The module for the current IfaceDecl
236 -- So if we see f = \x -> x
237 -- it means M.f = \x -> x, where M is the if_mod
240 -- The field is used only for error reporting
241 -- if (say) there's a Lint error in it
243 -- Where the interface came from:
244 -- .hi file, or GHCi state, or ext core
245 -- plus which bit is currently being examined
247 if_tv_env :: OccEnv TyVar, -- Nested tyvar bindings
248 if_id_env :: OccEnv Id -- Nested id binding
253 %************************************************************************
255 The local typechecker environment
257 %************************************************************************
259 The Global-Env/Local-Env story
260 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
261 During type checking, we keep in the tcg_type_env
262 * All types and classes
263 * All Ids derived from types and classes (constructors, selectors)
265 At the end of type checking, we zonk the local bindings,
266 and as we do so we add to the tcg_type_env
267 * Locally defined top-level Ids
269 Why? Because they are now Ids not TcIds. This final GlobalEnv is
270 a) fed back (via the knot) to typechecking the
271 unfoldings of interface signatures
272 b) used in the ModDetails of this module
275 data TcLclEnv -- Changes as we move inside an expression
276 -- Discarded after typecheck/rename; not passed on to desugarer
278 tcl_loc :: SrcSpan, -- Source span
279 tcl_ctxt :: ErrCtxt, -- Error context
280 tcl_errs :: TcRef Messages, -- Place to accumulate errors
282 tcl_th_ctxt :: ThStage, -- Template Haskell context
284 tcl_rdr :: LocalRdrEnv, -- Local name envt
285 -- Maintained during renaming, of course, but also during
286 -- type checking, solely so that when renaming a Template-Haskell
287 -- splice we have the right environment for the renamer.
289 -- Does *not* include global name envt; may shadow it
290 -- Includes both ordinary variables and type variables;
291 -- they are kept distinct because tyvar have a different
292 -- occurrence contructor (Name.TvOcc)
293 -- We still need the unsullied global name env so that
294 -- we can look up record field names
296 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
297 -- defined in this module
299 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
300 -- Namely, the in-scope TyVars bound in tcl_env,
301 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
302 -- Why mutable? see notes with tcGetGlobalTyVars
304 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
305 tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
307 -----------------------------------------------------------
308 -- Not yet; it's a new complication and I want to see whether it bites
309 -- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
310 -----------------------------------------------------------
313 type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
315 {- Note [Given Insts]
317 Because of GADTs, we have to pass inwards the Insts provided by type signatures
318 and existential contexts. Consider
319 data T a where { T1 :: b -> b -> T [b] }
320 f :: Eq a => T a -> Bool
321 f (T1 x y) = [x]==[y]
323 The constructor T1 binds an existential variable 'b', and we need Eq [b].
324 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
329 ---------------------------
330 -- Template Haskell levels
331 ---------------------------
334 -- Indicates how many levels of brackets we are inside
336 -- Incremented when going inside a bracket,
337 -- decremented when going inside a splice
339 impLevel, topLevel :: ThLevel
340 topLevel = 1 -- Things defined at top level of this module
341 impLevel = 0 -- Imported things; they can be used inside a top level splice
345 -- g1 = $(map ...) is OK
346 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
350 = Comp -- Ordinary compiling, at level topLevel
351 | Splice ThLevel -- Inside a splice
352 | Brack ThLevel -- Inside brackets;
353 (TcRef [PendingSplice]) -- accumulate pending splices here
354 (TcRef LIE) -- and type constraints here
355 topStage, topSpliceStage :: ThStage
357 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
360 ---------------------------
362 ---------------------------
365 = AGlobal TyThing -- Used only in the return type of a lookup
367 | ATcId TcId ThLevel -- Ids defined in this module; may not be fully zonked
369 | ATyVar Name TcType -- Type variables; tv -> type. It can't just be a TyVar
370 -- that is mutated to point to the type it is bound to,
371 -- because that would make it a wobbly type, and we
372 -- want pattern-bound lexically-scoped type variables to
373 -- be able to stand for rigid types
375 | AThing TcKind -- Used temporarily, during kind checking, for the
376 -- tycons and clases in this recursive group
378 instance Outputable TcTyThing where -- Debugging only
379 ppr (AGlobal g) = ppr g
380 ppr (ATcId g tl) = text "Identifier" <>
381 ifPprDebug (brackets (ppr g <> comma <> ppr tl))
382 ppr (ATyVar tv ty) = text "Type variable" <+> quotes (ppr tv) <+> pprParendType ty
383 ppr (AThing k) = text "AThing" <+> ppr k
385 pprTcTyThingCategory :: TcTyThing -> SDoc
386 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
387 pprTcTyThingCategory (ATyVar _ _) = ptext SLIT("Type variable")
388 pprTcTyThingCategory (ATcId _ _) = ptext SLIT("Local identifier")
389 pprTcTyThingCategory (AThing _) = ptext SLIT("Kinded thing")
393 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
394 -- Innermost first. Monadic so that we have a chance
395 -- to deal with bound type variables just before error
396 -- message construction
400 %************************************************************************
402 Operations over ImportAvails
404 %************************************************************************
406 ImportAvails summarises what was imported from where, irrespective
407 of whether the imported things are actually used or not
408 It is used * when processing the export list
409 * when constructing usage info for the inteface file
410 * to identify the list of directly imported modules
411 for initialisation purposes
412 * when figuring out what things are really unused
417 imp_env :: ModuleEnv NameSet,
418 -- All the things imported, classified by
419 -- the *module qualifier* for its import
420 -- e.g. import List as Foo
421 -- would add a binding Foo |-> ...stuff from List...
424 -- We need to classify them like this so that we can figure out
425 -- "module M" export specifiers in an export list
426 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
427 -- everything that is unambiguously in scope as 'M.x'
428 -- and where plain 'x' is (perhaps ambiguously) in scope.
429 -- So the starting point is all things that are in scope as 'M.x',
430 -- which is what this field tells us.
432 imp_mods :: ModuleEnv (Module, Maybe Bool, SrcSpan),
433 -- Domain is all directly-imported modules
434 -- Maybe value answers the question "is the import restricted?"
435 -- Nothing => unrestricted import (e.g., "import Foo")
436 -- Just True => restricted import, at least one entity (e.g., "import Foo(x)")
437 -- Just False => fully restricted import (e.g., "import Foo ()")
439 -- A distinction is made between the first and the third in order
440 -- to more precisely emit warnings about unused imports.
442 -- We need the Module in the range because we can't get
443 -- the keys of a ModuleEnv
445 -- (a) to help construct the usage information in
446 -- the interface file; if we import everything we
447 -- need to recompile if the module version changes
448 -- (b) to specify what child modules to initialise
450 imp_dep_mods :: ModuleEnv (Module, IsBootInterface),
451 -- Home-package modules needed by the module being compiled
453 -- It doesn't matter whether any of these dependencies
454 -- are actually *used* when compiling the module; they
455 -- are listed if they are below it at all. For
456 -- example, suppose M imports A which imports X. Then
457 -- compiling M might not need to consult X.hi, but X
458 -- is still listed in M's dependencies.
460 imp_dep_pkgs :: [PackageId],
461 -- Packages needed by the module being compiled, whether
462 -- directly, or via other modules in this package, or via
463 -- modules imported from other packages.
465 imp_orphs :: [Module]
466 -- Orphan modules below us in the import tree
469 mkModDeps :: [(Module, IsBootInterface)]
470 -> ModuleEnv (Module, IsBootInterface)
471 mkModDeps deps = foldl add emptyModuleEnv deps
473 add env elt@(m,_) = extendModuleEnv env m elt
475 emptyImportAvails :: ImportAvails
476 emptyImportAvails = ImportAvails { imp_env = emptyModuleEnv,
477 imp_mods = emptyModuleEnv,
478 imp_dep_mods = emptyModuleEnv,
482 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
484 (ImportAvails { imp_env = env1, imp_mods = mods1,
485 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
486 (ImportAvails { imp_env = env2, imp_mods = mods2,
487 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
488 = ImportAvails { imp_env = plusModuleEnv_C unionNameSets env1 env2,
489 imp_mods = mods1 `plusModuleEnv` mods2,
490 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
491 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
492 imp_orphs = orphs1 `unionLists` orphs2 }
494 plus_mod_dep (m1, boot1) (m2, boot2)
495 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
496 -- Check mod-names match
497 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
500 %************************************************************************
502 Avails, AvailEnv, etc
504 v%************************************************************************
507 plusAvail (Avail n1) (Avail n2) = Avail n1
508 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
511 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
514 -------------------------
515 pruneAvails :: (Name -> Bool) -- Keep if this is True
518 pruneAvails keep avails
519 = mapMaybe del avails
521 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
522 del (Avail n) | keep n = Just (Avail n)
523 | otherwise = Nothing
524 del (AvailTC n ns) | null ns' = Nothing
525 | otherwise = Just (AvailTC n ns')
530 ---------------------------------------
532 ---------------------------------------
535 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
537 emptyAvailEnv :: AvailEnv
538 emptyAvailEnv = emptyNameEnv
540 unitAvailEnv :: AvailInfo -> AvailEnv
541 unitAvailEnv a = unitNameEnv (availName a) a
543 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
544 plusAvailEnv = plusNameEnv_C plusAvail
546 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
547 lookupAvailEnv_maybe = lookupNameEnv
549 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
550 lookupAvailEnv env n = case lookupNameEnv env n of
552 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
554 availEnvElts = nameEnvElts
556 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
557 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
559 mkAvailEnv :: [AvailInfo] -> AvailEnv
560 -- 'avails' may have several items with the same availName
561 -- E.g import Ix( Ix(..), index )
562 -- will give Ix(Ix,index,range) and Ix(index)
563 -- We want to combine these; addAvail does that
564 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
567 %************************************************************************
569 \subsection{Where from}
571 %************************************************************************
573 The @WhereFrom@ type controls where the renamer looks for an interface file
577 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
578 | ImportBySystem -- Non user import.
580 instance Outputable WhereFrom where
581 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
583 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
587 %************************************************************************
589 \subsection[Inst-types]{@Inst@ types}
591 v%************************************************************************
593 An @Inst@ is either a dictionary, an instance of an overloaded
594 literal, or an instance of an overloaded value. We call the latter a
595 ``method'' even though it may not correspond to a class operation.
596 For example, we might have an instance of the @double@ function at
597 type Int, represented by
599 Method 34 doubleId [Int] origin
611 TcId -- The overloaded function
612 -- This function will be a global, local, or ClassOpId;
613 -- inside instance decls (only) it can also be an InstId!
614 -- The id needn't be completely polymorphic.
615 -- You'll probably find its name (for documentation purposes)
616 -- inside the InstOrigin
618 [TcType] -- The types to which its polymorphic tyvars
619 -- should be instantiated.
620 -- These types must saturate the Id's foralls.
622 TcThetaType -- The (types of the) dictionaries to which the function
623 -- must be applied to get the method
625 TcTauType -- The tau-type of the method
629 -- INVARIANT 1: in (Method u f tys theta tau loc)
630 -- type of (f tys dicts(from theta)) = tau
632 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
633 -- Reason: two methods are considered equal if the
634 -- base Id matches, and the instantiating types
635 -- match. The TcThetaType should then match too.
636 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
640 (HsOverLit Name) -- The literal from the occurrence site
641 -- INVARIANT: never a rebindable-syntax literal
642 -- Reason: tcSyntaxName does unification, and we
643 -- don't want to deal with that during tcSimplify,
644 -- when resolving LitInsts
645 TcType -- The type at which the literal is used
649 @Insts@ are ordered by their class/type info, rather than by their
650 unique. This allows the context-reduction mechanism to use standard finite
651 maps to do their stuff.
654 instance Ord Inst where
657 instance Eq Inst where
658 (==) i1 i2 = case i1 `cmpInst` i2 of
662 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
663 cmpInst (Dict _ _ _) other = LT
665 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
666 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
667 cmpInst (Method _ _ _ _ _ _) other = LT
669 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
670 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _ _) = GT
671 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
675 %************************************************************************
677 \subsection[Inst-collections]{LIE: a collection of Insts}
679 %************************************************************************
684 isEmptyLIE = isEmptyBag
686 unitLIE inst = unitBag inst
687 mkLIE insts = listToBag insts
688 plusLIE lie1 lie2 = lie1 `unionBags` lie2
689 consLIE inst lie = inst `consBag` lie
690 plusLIEs lies = unionManyBags lies
691 lieToList = bagToList
692 listToLIE = listToBag
696 %************************************************************************
698 \subsection[Inst-origin]{The @InstOrigin@ type}
700 %************************************************************************
702 The @InstOrigin@ type gives information about where a dictionary came from.
703 This is important for decent error message reporting because dictionaries
704 don't appear in the original source code. Doubtless this type will evolve...
706 It appears in TcMonad because there are a couple of error-message-generation
707 functions that deal with it.
710 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
712 instLocSrcLoc :: InstLoc -> SrcLoc
713 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
715 instLocSrcSpan :: InstLoc -> SrcSpan
716 instLocSrcSpan (InstLoc _ src_span _) = src_span
719 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
720 -- Places that bind type variables and introduce
721 -- available constraints
723 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
725 -------------------------------------------------------
726 -- The rest are all occurrences: Insts that are 'wanted'
727 -------------------------------------------------------
728 | OccurrenceOf Name -- Occurrence of an overloaded identifier
730 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
732 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
734 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
735 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
737 | InstSigOrigin -- A dict occurrence arising from instantiating
738 -- a polymorphic type during a subsumption check
741 | InstScOrigin -- Typechecking superclasses of an instance declaration
742 | DerivOrigin -- Typechecking deriving
743 | DefaultOrigin -- Typechecking a default decl
744 | DoOrigin -- Arising from a do expression
745 | ProcOrigin -- Arising from a proc expression
749 pprInstLoc :: InstLoc -> SDoc
750 pprInstLoc (InstLoc orig locn _)
751 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
753 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
754 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
755 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
756 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
757 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
758 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
759 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
760 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
761 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
762 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
763 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
764 pp_orig DoOrigin = ptext SLIT("a do statement")
765 pp_orig ProcOrigin = ptext SLIT("a proc expression")
766 pp_orig (SigOrigin info) = pprSkolInfo info