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, HsGroup )
47 import HscTypes ( FixityEnv,
48 HscEnv, TypeEnv, TyThing,
49 GenAvailInfo(..), AvailInfo, HscSource(..),
50 availName, IsBootInterface, Deprecations )
51 import Packages ( PackageId, HomeModules )
52 import Type ( Type, pprTyThingCategory )
53 import TcType ( TcTyVarSet, TcType, TcThetaType, SkolemInfo, TvSubst,
54 TcPredType, TcKind, tcCmpPred, tcCmpType, tcCmpTypes, pprSkolInfo )
55 import InstEnv ( Instance, InstEnv )
57 import RdrName ( GlobalRdrEnv, LocalRdrEnv )
60 import NameSet ( NameSet, unionNameSets, DefUses )
61 import OccName ( OccEnv )
62 import Var ( Id, TyVar )
63 import VarEnv ( TidyEnv )
65 import SrcLoc ( SrcSpan, SrcLoc, srcSpanStart )
66 import VarSet ( IdSet )
67 import ErrUtils ( Messages, Message )
68 import UniqSupply ( UniqSupply )
69 import BasicTypes ( IPName )
70 import Util ( thenCmp )
73 import Maybe ( mapMaybe )
74 import ListSetOps ( unionLists )
78 %************************************************************************
80 Standard monad definition for TcRn
81 All the combinators for the monad can be found in TcRnMonad
83 %************************************************************************
85 The monad itself has to be defined here, because it is mentioned by ErrCtxt
88 type TcRef a = IORef a
89 type TcId = Id -- Type may be a TcType
91 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
97 type IfG a = IfM () a -- Top level
98 type IfL a = IfM IfLclEnv a -- Nested
99 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
100 type RnM a = TcRn a -- Historical
101 type TcM a = TcRn a -- Historical
105 %************************************************************************
107 The main environment types
109 %************************************************************************
112 data Env gbl lcl -- Changes as we move into an expression
114 env_top :: HscEnv, -- Top-level stuff that never changes
115 -- Includes all info about imported things
117 env_us :: TcRef UniqSupply, -- Unique supply for local varibles
119 env_gbl :: gbl, -- Info about things defined at the top level
120 -- of the module being compiled
122 env_lcl :: lcl -- Nested stuff; changes as we go into
126 -- TcGblEnv describes the top-level of the module at the
127 -- point at which the typechecker is finished work.
128 -- It is this structure that is handed on to the desugarer
132 tcg_mod :: Module, -- Module being compiled
133 tcg_src :: HscSource, -- What kind of module
134 -- (regular Haskell, hs-boot, ext-core)
136 tcg_rdr_env :: GlobalRdrEnv, -- Top level envt; used during renaming
137 tcg_default :: Maybe [Type], -- Types used for defaulting
138 -- Nothing => no 'default' decl
140 tcg_fix_env :: FixityEnv, -- Just for things in this module
142 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
143 -- All TyCons and Classes (for this module) end up in here right away,
144 -- along with their derived constructors, selectors.
146 -- (Ids defined in this module start in the local envt,
147 -- though they move to the global envt during zonking)
149 tcg_type_env_var :: TcRef TypeEnv,
150 -- Used only to initialise the interface-file
151 -- typechecker in initIfaceTcRn, so that it can see stuff
152 -- bound in this module when dealing with hi-boot recursions
153 -- Updated at intervals (e.g. after dealing with types and classes)
155 tcg_inst_env :: InstEnv, -- Instance envt for *home-package* modules
156 -- Includes the dfuns in tcg_insts
157 -- Now a bunch of things about this module that are simply
158 -- accumulated, but never consulted until the end.
159 -- Nevertheless, it's convenient to accumulate them along
160 -- with the rest of the info from this module.
161 tcg_exports :: NameSet, -- What is exported
162 tcg_imports :: ImportAvails, -- Information about what was imported
163 -- from where, including things bound
166 tcg_home_mods :: HomeModules,
167 -- Calculated from ImportAvails, allows us to
168 -- call Packages.isHomeModule
170 tcg_dus :: DefUses, -- What is defined in this module and what is used.
171 -- The latter is used to generate
172 -- (a) version tracking; no need to recompile if these
173 -- things have not changed version stamp
174 -- (b) unused-import info
176 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
177 -- "Keep alive" means give them an Exported flag, so
178 -- that the simplifier does not discard them as dead
179 -- code, and so that they are exposed in the interface file
180 -- (but not to export to the user).
182 -- Some things, like dict-fun Ids and default-method Ids are
183 -- "born" with the Exported flag on, for exactly the above reason,
184 -- but some we only discover as we go. Specifically:
185 -- * The to/from functions for generic data types
186 -- * Top-level variables appearing free in the RHS of an orphan rule
187 -- * Top-level variables appearing free in a TH bracket
189 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
190 -- Used to generate version dependencies
191 -- This records usages, rather like tcg_dus, but it has to
192 -- be a mutable variable so it can be augmented
193 -- when we look up an instance. These uses of dfuns are
194 -- rather like the free variables of the program, but
195 -- are implicit instead of explicit.
197 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
198 -- We need this so that we can generate a dependency on the
199 -- Template Haskell package, becuase the desugarer is going to
200 -- emit loads of references to TH symbols. It's rather like
201 -- tcg_inst_uses; the reference is implicit rather than explicit,
202 -- so we have to zap a mutable variable.
204 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
205 -- It's convenient to allocate an External Name for a DFun, with
206 -- a permanently-fixed unique, just like other top-level functions
207 -- defined in this module. But that means we need a canonical
208 -- occurrence name, distinct from all other dfuns in this module,
209 -- and this name supply serves that purpose (df1, df2, etc).
211 -- The next fields accumulate the payload of the module
212 -- The binds, rules and foreign-decl fiels are collected
213 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
215 -- The next fields accumulate the payload of the
216 -- module The binds, rules and foreign-decl fiels are
217 -- collected initially in un-zonked form and are
218 -- finally zonked in tcRnSrcDecls
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 :: OccEnv TyVar, -- Nested tyvar bindings
267 if_id_env :: OccEnv 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
353 impLevel, topLevel :: ThLevel
354 topLevel = 1 -- Things defined at top level of this module
355 impLevel = 0 -- Imported things; they can be used inside a top level splice
359 -- g1 = $(map ...) is OK
360 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
364 = Comp -- Ordinary compiling, at level topLevel
365 | Splice ThLevel -- Inside a splice
366 | Brack ThLevel -- Inside brackets;
367 (TcRef [PendingSplice]) -- accumulate pending splices here
368 (TcRef LIE) -- and type constraints here
369 topStage, topSpliceStage :: ThStage
371 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
373 ---------------------------
374 -- Arrow-notation context
375 ---------------------------
378 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
379 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
384 Here, x is not in scope in e1, but it is in scope in e2. This can get
388 proc y -> (proc z -> e1) -< e2
390 Here, x and z are in scope in e1, but y is not. We implement this by
391 recording the environment when passing a proc (using newArrowScope),
392 and returning to that (using escapeArrowScope) on the left of -< and the
398 | ArrowCtxt (Env TcGblEnv TcLclEnv)
400 -- Record the current environment (outside a proc)
401 newArrowScope :: TcM a -> TcM a
404 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
406 -- Return to the stored environment (from the enclosing proc)
407 escapeArrowScope :: TcM a -> TcM a
409 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
411 ArrowCtxt env' -> env'
413 ---------------------------
415 ---------------------------
418 = AGlobal TyThing -- Used only in the return type of a lookup
420 | ATcId TcId -- Ids defined in this module; may not be fully zonked
422 Bool -- True <=> apply the type refinement to me
424 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
425 -- is currently refined. We only need the Name
426 -- for error-message purposes
428 | AThing TcKind -- Used temporarily, during kind checking, for the
429 -- tycons and clases in this recursive group
431 instance Outputable TcTyThing where -- Debugging only
432 ppr (AGlobal g) = ppr g
433 ppr (ATcId g tl rig) = text "Identifier" <>
434 ifPprDebug (brackets (ppr g <> comma <> ppr tl <+> ppr rig))
435 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
436 ppr (AThing k) = text "AThing" <+> ppr k
438 pprTcTyThingCategory :: TcTyThing -> SDoc
439 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
440 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
441 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
442 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
446 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
447 -- Innermost first. Monadic so that we have a chance
448 -- to deal with bound type variables just before error
449 -- message construction
453 %************************************************************************
455 Operations over ImportAvails
457 %************************************************************************
459 ImportAvails summarises what was imported from where, irrespective
460 of whether the imported things are actually used or not
461 It is used * when processing the export list
462 * when constructing usage info for the inteface file
463 * to identify the list of directly imported modules
464 for initialisation purposes
465 * when figuring out what things are really unused
470 imp_env :: ModuleEnv NameSet,
471 -- All the things imported, classified by
472 -- the *module qualifier* for its import
473 -- e.g. import List as Foo
474 -- would add a binding Foo |-> ...stuff from List...
477 -- We need to classify them like this so that we can figure out
478 -- "module M" export specifiers in an export list
479 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
480 -- everything that is unambiguously in scope as 'M.x'
481 -- and where plain 'x' is (perhaps ambiguously) in scope.
482 -- So the starting point is all things that are in scope as 'M.x',
483 -- which is what this field tells us.
485 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
486 -- Domain is all directly-imported modules
488 -- True => import was "import Foo ()"
489 -- False => import was some other form
491 -- We need the Module in the range because we can't get
492 -- the keys of a ModuleEnv
494 -- (a) to help construct the usage information in
495 -- the interface file; if we import somethign we
496 -- need to recompile if the export version changes
497 -- (b) to specify what child modules to initialise
499 imp_dep_mods :: ModuleEnv (Module, IsBootInterface),
500 -- Home-package modules needed by the module being compiled
502 -- It doesn't matter whether any of these dependencies
503 -- are actually *used* when compiling the module; they
504 -- are listed if they are below it at all. For
505 -- example, suppose M imports A which imports X. Then
506 -- compiling M might not need to consult X.hi, but X
507 -- is still listed in M's dependencies.
509 imp_dep_pkgs :: [PackageId],
510 -- Packages needed by the module being compiled, whether
511 -- directly, or via other modules in this package, or via
512 -- modules imported from other packages.
514 imp_orphs :: [Module]
515 -- Orphan modules below us in the import tree
518 mkModDeps :: [(Module, IsBootInterface)]
519 -> ModuleEnv (Module, IsBootInterface)
520 mkModDeps deps = foldl add emptyModuleEnv deps
522 add env elt@(m,_) = extendModuleEnv env m elt
524 emptyImportAvails :: ImportAvails
525 emptyImportAvails = ImportAvails { imp_env = emptyModuleEnv,
526 imp_mods = emptyModuleEnv,
527 imp_dep_mods = emptyModuleEnv,
531 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
533 (ImportAvails { imp_env = env1, imp_mods = mods1,
534 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
535 (ImportAvails { imp_env = env2, imp_mods = mods2,
536 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
537 = ImportAvails { imp_env = plusModuleEnv_C unionNameSets env1 env2,
538 imp_mods = mods1 `plusModuleEnv` mods2,
539 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
540 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
541 imp_orphs = orphs1 `unionLists` orphs2 }
543 plus_mod_dep (m1, boot1) (m2, boot2)
544 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
545 -- Check mod-names match
546 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
549 %************************************************************************
551 Avails, AvailEnv, etc
553 v%************************************************************************
556 plusAvail (Avail n1) (Avail n2) = Avail n1
557 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
560 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
563 -------------------------
564 pruneAvails :: (Name -> Bool) -- Keep if this is True
567 pruneAvails keep avails
568 = mapMaybe del avails
570 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
571 del (Avail n) | keep n = Just (Avail n)
572 | otherwise = Nothing
573 del (AvailTC n ns) | null ns' = Nothing
574 | otherwise = Just (AvailTC n ns')
579 ---------------------------------------
581 ---------------------------------------
584 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
586 emptyAvailEnv :: AvailEnv
587 emptyAvailEnv = emptyNameEnv
589 unitAvailEnv :: AvailInfo -> AvailEnv
590 unitAvailEnv a = unitNameEnv (availName a) a
592 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
593 plusAvailEnv = plusNameEnv_C plusAvail
595 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
596 lookupAvailEnv_maybe = lookupNameEnv
598 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
599 lookupAvailEnv env n = case lookupNameEnv env n of
601 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
603 availEnvElts = nameEnvElts
605 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
606 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
608 mkAvailEnv :: [AvailInfo] -> AvailEnv
609 -- 'avails' may have several items with the same availName
610 -- E.g import Ix( Ix(..), index )
611 -- will give Ix(Ix,index,range) and Ix(index)
612 -- We want to combine these; addAvail does that
613 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
616 %************************************************************************
618 \subsection{Where from}
620 %************************************************************************
622 The @WhereFrom@ type controls where the renamer looks for an interface file
626 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
627 | ImportBySystem -- Non user import.
629 instance Outputable WhereFrom where
630 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
632 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
636 %************************************************************************
638 \subsection[Inst-types]{@Inst@ types}
640 v%************************************************************************
642 An @Inst@ is either a dictionary, an instance of an overloaded
643 literal, or an instance of an overloaded value. We call the latter a
644 ``method'' even though it may not correspond to a class operation.
645 For example, we might have an instance of the @double@ function at
646 type Int, represented by
648 Method 34 doubleId [Int] origin
660 TcId -- The overloaded function
661 -- This function will be a global, local, or ClassOpId;
662 -- inside instance decls (only) it can also be an InstId!
663 -- The id needn't be completely polymorphic.
664 -- You'll probably find its name (for documentation purposes)
665 -- inside the InstOrigin
667 [TcType] -- The types to which its polymorphic tyvars
668 -- should be instantiated.
669 -- These types must saturate the Id's foralls.
671 TcThetaType -- The (types of the) dictionaries to which the function
672 -- must be applied to get the method
676 -- INVARIANT 1: in (Method u f tys theta tau loc)
677 -- type of (f tys dicts(from theta)) = tau
679 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
680 -- Reason: two methods are considered equal if the
681 -- base Id matches, and the instantiating types
682 -- match. The TcThetaType should then match too.
683 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
687 (HsOverLit Name) -- The literal from the occurrence site
688 -- INVARIANT: never a rebindable-syntax literal
689 -- Reason: tcSyntaxName does unification, and we
690 -- don't want to deal with that during tcSimplify,
691 -- when resolving LitInsts
692 TcType -- The type at which the literal is used
696 @Insts@ are ordered by their class/type info, rather than by their
697 unique. This allows the context-reduction mechanism to use standard finite
698 maps to do their stuff.
701 instance Ord Inst where
704 instance Eq Inst where
705 (==) i1 i2 = case i1 `cmpInst` i2 of
709 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
710 cmpInst (Dict _ _ _) other = LT
712 cmpInst (Method _ _ _ _ _) (Dict _ _ _) = GT
713 cmpInst (Method _ id1 tys1 _ _) (Method _ id2 tys2 _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
714 cmpInst (Method _ _ _ _ _) other = LT
716 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
717 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _) = GT
718 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
722 %************************************************************************
724 \subsection[Inst-collections]{LIE: a collection of Insts}
726 %************************************************************************
731 isEmptyLIE = isEmptyBag
733 unitLIE inst = unitBag inst
734 mkLIE insts = listToBag insts
735 plusLIE lie1 lie2 = lie1 `unionBags` lie2
736 consLIE inst lie = inst `consBag` lie
737 plusLIEs lies = unionManyBags lies
738 lieToList = bagToList
739 listToLIE = listToBag
743 %************************************************************************
745 \subsection[Inst-origin]{The @InstOrigin@ type}
747 %************************************************************************
749 The @InstOrigin@ type gives information about where a dictionary came from.
750 This is important for decent error message reporting because dictionaries
751 don't appear in the original source code. Doubtless this type will evolve...
753 It appears in TcMonad because there are a couple of error-message-generation
754 functions that deal with it.
757 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
759 instLocSrcLoc :: InstLoc -> SrcLoc
760 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
762 instLocSrcSpan :: InstLoc -> SrcSpan
763 instLocSrcSpan (InstLoc _ src_span _) = src_span
766 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
767 -- Places that bind type variables and introduce
768 -- available constraints
770 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
772 -------------------------------------------------------
773 -- The rest are all occurrences: Insts that are 'wanted'
774 -------------------------------------------------------
775 | OccurrenceOf Name -- Occurrence of an overloaded identifier
777 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
779 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
781 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
782 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
784 | InstSigOrigin -- A dict occurrence arising from instantiating
785 -- a polymorphic type during a subsumption check
788 | InstScOrigin -- Typechecking superclasses of an instance declaration
789 | DerivOrigin -- Typechecking deriving
790 | DefaultOrigin -- Typechecking a default decl
791 | DoOrigin -- Arising from a do expression
792 | ProcOrigin -- Arising from a proc expression
796 pprInstLoc :: InstLoc -> SDoc
797 pprInstLoc (InstLoc orig locn _)
798 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
800 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
801 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
802 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
803 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
804 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
805 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
806 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
807 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
808 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
809 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
810 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
811 pp_orig DoOrigin = ptext SLIT("a do statement")
812 pp_orig ProcOrigin = ptext SLIT("a proc expression")
813 pp_orig (SigOrigin info) = pprSkolInfo info