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(NoArrowCtxt), newArrowScope, escapeArrowScope,
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, HsGroup )
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, pprSkolInfo )
54 import InstEnv ( Instance, 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 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
200 -- It's convenient to allocate an External Name for a DFun, with
201 -- a permanently-fixed unique, just like other top-level functions
202 -- defined in this module. But that means we need a canonical
203 -- occurrence name, distinct from all other dfuns in this module,
204 -- and this name supply serves that purpose (df1, df2, etc).
206 -- The next fields accumulate the payload of the module
207 -- The binds, rules and foreign-decl fiels are collected
208 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
210 -- The next fields accumulate the payload of the
211 -- module The binds, rules and foreign-decl fiels are
212 -- collected initially in un-zonked form and are
213 -- finally zonked in tcRnSrcDecls
215 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
216 -- Nothing <=> Don't retain renamed decls
218 tcg_binds :: LHsBinds Id, -- Value bindings in this module
219 tcg_deprecs :: Deprecations, -- ...Deprecations
220 tcg_insts :: [Instance], -- ...Instances
221 tcg_rules :: [LRuleDecl Id], -- ...Rules
222 tcg_fords :: [LForeignDecl Id] -- ...Foreign import & exports
226 %************************************************************************
228 The interface environments
229 Used when dealing with IfaceDecls
231 %************************************************************************
236 -- The type environment for the module being compiled,
237 -- in case the interface refers back to it via a reference that
238 -- was originally a hi-boot file.
239 -- We need the module name so we can test when it's appropriate
240 -- to look in this env.
241 if_rec_types :: Maybe (Module, IfG TypeEnv)
242 -- Allows a read effect, so it can be in a mutable
243 -- variable; c.f. handling the external package type env
244 -- Nothing => interactive stuff, no loops possible
249 -- The module for the current IfaceDecl
250 -- So if we see f = \x -> x
251 -- it means M.f = \x -> x, where M is the if_mod
254 -- The field is used only for error reporting
255 -- if (say) there's a Lint error in it
257 -- Where the interface came from:
258 -- .hi file, or GHCi state, or ext core
259 -- plus which bit is currently being examined
261 if_tv_env :: OccEnv TyVar, -- Nested tyvar bindings
262 if_id_env :: OccEnv Id -- Nested id binding
267 %************************************************************************
269 The local typechecker environment
271 %************************************************************************
273 The Global-Env/Local-Env story
274 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
275 During type checking, we keep in the tcg_type_env
276 * All types and classes
277 * All Ids derived from types and classes (constructors, selectors)
279 At the end of type checking, we zonk the local bindings,
280 and as we do so we add to the tcg_type_env
281 * Locally defined top-level Ids
283 Why? Because they are now Ids not TcIds. This final GlobalEnv is
284 a) fed back (via the knot) to typechecking the
285 unfoldings of interface signatures
286 b) used in the ModDetails of this module
289 data TcLclEnv -- Changes as we move inside an expression
290 -- Discarded after typecheck/rename; not passed on to desugarer
292 tcl_loc :: SrcSpan, -- Source span
293 tcl_ctxt :: ErrCtxt, -- Error context
294 tcl_errs :: TcRef Messages, -- Place to accumulate errors
296 tcl_th_ctxt :: ThStage, -- Template Haskell context
297 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
299 tcl_rdr :: LocalRdrEnv, -- Local name envt
300 -- Maintained during renaming, of course, but also during
301 -- type checking, solely so that when renaming a Template-Haskell
302 -- splice we have the right environment for the renamer.
304 -- Does *not* include global name envt; may shadow it
305 -- Includes both ordinary variables and type variables;
306 -- they are kept distinct because tyvar have a different
307 -- occurrence contructor (Name.TvOcc)
308 -- We still need the unsullied global name env so that
309 -- we can look up record field names
311 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
312 -- defined in this module
314 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
315 -- Namely, the in-scope TyVars bound in tcl_env,
316 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
317 -- Why mutable? see notes with tcGetGlobalTyVars
319 tcl_lie :: TcRef LIE, -- Place to accumulate type constraints
320 tcl_gadt :: GadtRefinement -- The current type refinement for GADTs
322 -----------------------------------------------------------
323 -- Not yet; it's a new complication and I want to see whether it bites
324 -- tcl_given :: [Inst] -- Insts available in the current context (see Note [Given Insts])
325 -----------------------------------------------------------
328 type GadtRefinement = TvSubstEnv -- Binds rigid type variables to their refinements
330 {- Note [Given Insts]
332 Because of GADTs, we have to pass inwards the Insts provided by type signatures
333 and existential contexts. Consider
334 data T a where { T1 :: b -> b -> T [b] }
335 f :: Eq a => T a -> Bool
336 f (T1 x y) = [x]==[y]
338 The constructor T1 binds an existential variable 'b', and we need Eq [b].
339 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
344 ---------------------------
345 -- Template Haskell levels
346 ---------------------------
349 -- Indicates how many levels of brackets we are inside
351 -- Incremented when going inside a bracket,
352 -- decremented when going inside a splice
354 impLevel, topLevel :: ThLevel
355 topLevel = 1 -- Things defined at top level of this module
356 impLevel = 0 -- Imported things; they can be used inside a top level splice
360 -- g1 = $(map ...) is OK
361 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
365 = Comp -- Ordinary compiling, at level topLevel
366 | Splice ThLevel -- Inside a splice
367 | Brack ThLevel -- Inside brackets;
368 (TcRef [PendingSplice]) -- accumulate pending splices here
369 (TcRef LIE) -- and type constraints here
370 topStage, topSpliceStage :: ThStage
372 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
374 ---------------------------
375 -- Arrow-notation context
376 ---------------------------
379 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
380 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
385 Here, x is not in scope in e1, but it is in scope in e2. This can get
389 proc y -> (proc z -> e1) -< e2
391 Here, x and z are in scope in e1, but y is not. We implement this by
392 recording the environment when passing a proc (using newArrowScope),
393 and returning to that (using escapeArrowScope) on the left of -< and the
399 | ArrowCtxt (Env TcGblEnv TcLclEnv)
401 -- Record the current environment (outside a proc)
402 newArrowScope :: TcM a -> TcM a
405 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
407 -- Return to the stored environment (from the enclosing proc)
408 escapeArrowScope :: TcM a -> TcM a
410 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
412 ArrowCtxt env' -> env'
414 ---------------------------
416 ---------------------------
419 = AGlobal TyThing -- Used only in the return type of a lookup
421 | ATcId TcId ThLevel -- Ids defined in this module; may not be fully zonked
423 | ATyVar Name TcType -- Type variables; tv -> type. It can't just be a TyVar
424 -- that is mutated to point to the type it is bound to,
425 -- because that would make it a wobbly type, and we
426 -- want pattern-bound lexically-scoped type variables to
427 -- be able to stand for rigid types
429 | AThing TcKind -- Used temporarily, during kind checking, for the
430 -- tycons and clases in this recursive group
432 instance Outputable TcTyThing where -- Debugging only
433 ppr (AGlobal g) = ppr g
434 ppr (ATcId g tl) = text "Identifier" <>
435 ifPprDebug (brackets (ppr g <> comma <> ppr tl))
436 ppr (ATyVar tv ty) = text "Type variable" <+> quotes (ppr tv) <+> pprParendType ty
437 ppr (AThing k) = text "AThing" <+> ppr k
439 pprTcTyThingCategory :: TcTyThing -> SDoc
440 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
441 pprTcTyThingCategory (ATyVar _ _) = ptext SLIT("Type variable")
442 pprTcTyThingCategory (ATcId _ _) = ptext SLIT("Local identifier")
443 pprTcTyThingCategory (AThing _) = ptext SLIT("Kinded thing")
447 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
448 -- Innermost first. Monadic so that we have a chance
449 -- to deal with bound type variables just before error
450 -- message construction
454 %************************************************************************
456 Operations over ImportAvails
458 %************************************************************************
460 ImportAvails summarises what was imported from where, irrespective
461 of whether the imported things are actually used or not
462 It is used * when processing the export list
463 * when constructing usage info for the inteface file
464 * to identify the list of directly imported modules
465 for initialisation purposes
466 * when figuring out what things are really unused
471 imp_env :: ModuleEnv NameSet,
472 -- All the things imported, classified by
473 -- the *module qualifier* for its import
474 -- e.g. import List as Foo
475 -- would add a binding Foo |-> ...stuff from List...
478 -- We need to classify them like this so that we can figure out
479 -- "module M" export specifiers in an export list
480 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
481 -- everything that is unambiguously in scope as 'M.x'
482 -- and where plain 'x' is (perhaps ambiguously) in scope.
483 -- So the starting point is all things that are in scope as 'M.x',
484 -- which is what this field tells us.
486 imp_mods :: ModuleEnv (Module, Maybe Bool, SrcSpan),
487 -- Domain is all directly-imported modules
488 -- Maybe value answers the question "is the import restricted?"
489 -- Nothing => unrestricted import (e.g., "import Foo")
490 -- Just True => restricted import, at least one entity (e.g., "import Foo(x)")
491 -- Just False => fully restricted import (e.g., "import Foo ()")
493 -- A distinction is made between the first and the third in order
494 -- to more precisely emit warnings about unused imports.
496 -- We need the Module in the range because we can't get
497 -- the keys of a ModuleEnv
499 -- (a) to help construct the usage information in
500 -- the interface file; if we import everything we
501 -- need to recompile if the module version changes
502 -- (b) to specify what child modules to initialise
504 imp_dep_mods :: ModuleEnv (Module, IsBootInterface),
505 -- Home-package modules needed by the module being compiled
507 -- It doesn't matter whether any of these dependencies
508 -- are actually *used* when compiling the module; they
509 -- are listed if they are below it at all. For
510 -- example, suppose M imports A which imports X. Then
511 -- compiling M might not need to consult X.hi, but X
512 -- is still listed in M's dependencies.
514 imp_dep_pkgs :: [PackageId],
515 -- Packages needed by the module being compiled, whether
516 -- directly, or via other modules in this package, or via
517 -- modules imported from other packages.
519 imp_orphs :: [Module]
520 -- Orphan modules below us in the import tree
523 mkModDeps :: [(Module, IsBootInterface)]
524 -> ModuleEnv (Module, IsBootInterface)
525 mkModDeps deps = foldl add emptyModuleEnv deps
527 add env elt@(m,_) = extendModuleEnv env m elt
529 emptyImportAvails :: ImportAvails
530 emptyImportAvails = ImportAvails { imp_env = emptyModuleEnv,
531 imp_mods = emptyModuleEnv,
532 imp_dep_mods = emptyModuleEnv,
536 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
538 (ImportAvails { imp_env = env1, imp_mods = mods1,
539 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
540 (ImportAvails { imp_env = env2, imp_mods = mods2,
541 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
542 = ImportAvails { imp_env = plusModuleEnv_C unionNameSets env1 env2,
543 imp_mods = mods1 `plusModuleEnv` mods2,
544 imp_dep_mods = plusModuleEnv_C plus_mod_dep dmods1 dmods2,
545 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
546 imp_orphs = orphs1 `unionLists` orphs2 }
548 plus_mod_dep (m1, boot1) (m2, boot2)
549 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
550 -- Check mod-names match
551 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
554 %************************************************************************
556 Avails, AvailEnv, etc
558 v%************************************************************************
561 plusAvail (Avail n1) (Avail n2) = Avail n1
562 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
565 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
568 -------------------------
569 pruneAvails :: (Name -> Bool) -- Keep if this is True
572 pruneAvails keep avails
573 = mapMaybe del avails
575 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
576 del (Avail n) | keep n = Just (Avail n)
577 | otherwise = Nothing
578 del (AvailTC n ns) | null ns' = Nothing
579 | otherwise = Just (AvailTC n ns')
584 ---------------------------------------
586 ---------------------------------------
589 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
591 emptyAvailEnv :: AvailEnv
592 emptyAvailEnv = emptyNameEnv
594 unitAvailEnv :: AvailInfo -> AvailEnv
595 unitAvailEnv a = unitNameEnv (availName a) a
597 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
598 plusAvailEnv = plusNameEnv_C plusAvail
600 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
601 lookupAvailEnv_maybe = lookupNameEnv
603 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
604 lookupAvailEnv env n = case lookupNameEnv env n of
606 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
608 availEnvElts = nameEnvElts
610 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
611 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
613 mkAvailEnv :: [AvailInfo] -> AvailEnv
614 -- 'avails' may have several items with the same availName
615 -- E.g import Ix( Ix(..), index )
616 -- will give Ix(Ix,index,range) and Ix(index)
617 -- We want to combine these; addAvail does that
618 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
621 %************************************************************************
623 \subsection{Where from}
625 %************************************************************************
627 The @WhereFrom@ type controls where the renamer looks for an interface file
631 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
632 | ImportBySystem -- Non user import.
634 instance Outputable WhereFrom where
635 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
637 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
641 %************************************************************************
643 \subsection[Inst-types]{@Inst@ types}
645 v%************************************************************************
647 An @Inst@ is either a dictionary, an instance of an overloaded
648 literal, or an instance of an overloaded value. We call the latter a
649 ``method'' even though it may not correspond to a class operation.
650 For example, we might have an instance of the @double@ function at
651 type Int, represented by
653 Method 34 doubleId [Int] origin
665 TcId -- The overloaded function
666 -- This function will be a global, local, or ClassOpId;
667 -- inside instance decls (only) it can also be an InstId!
668 -- The id needn't be completely polymorphic.
669 -- You'll probably find its name (for documentation purposes)
670 -- inside the InstOrigin
672 [TcType] -- The types to which its polymorphic tyvars
673 -- should be instantiated.
674 -- These types must saturate the Id's foralls.
676 TcThetaType -- The (types of the) dictionaries to which the function
677 -- must be applied to get the method
679 TcTauType -- The tau-type of the method
683 -- INVARIANT 1: in (Method u f tys theta tau loc)
684 -- type of (f tys dicts(from theta)) = tau
686 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
687 -- Reason: two methods are considered equal if the
688 -- base Id matches, and the instantiating types
689 -- match. The TcThetaType should then match too.
690 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
694 (HsOverLit Name) -- The literal from the occurrence site
695 -- INVARIANT: never a rebindable-syntax literal
696 -- Reason: tcSyntaxName does unification, and we
697 -- don't want to deal with that during tcSimplify,
698 -- when resolving LitInsts
699 TcType -- The type at which the literal is used
703 @Insts@ are ordered by their class/type info, rather than by their
704 unique. This allows the context-reduction mechanism to use standard finite
705 maps to do their stuff.
708 instance Ord Inst where
711 instance Eq Inst where
712 (==) i1 i2 = case i1 `cmpInst` i2 of
716 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
717 cmpInst (Dict _ _ _) other = LT
719 cmpInst (Method _ _ _ _ _ _) (Dict _ _ _) = GT
720 cmpInst (Method _ id1 tys1 _ _ _) (Method _ id2 tys2 _ _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
721 cmpInst (Method _ _ _ _ _ _) other = LT
723 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
724 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _ _) = GT
725 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
729 %************************************************************************
731 \subsection[Inst-collections]{LIE: a collection of Insts}
733 %************************************************************************
738 isEmptyLIE = isEmptyBag
740 unitLIE inst = unitBag inst
741 mkLIE insts = listToBag insts
742 plusLIE lie1 lie2 = lie1 `unionBags` lie2
743 consLIE inst lie = inst `consBag` lie
744 plusLIEs lies = unionManyBags lies
745 lieToList = bagToList
746 listToLIE = listToBag
750 %************************************************************************
752 \subsection[Inst-origin]{The @InstOrigin@ type}
754 %************************************************************************
756 The @InstOrigin@ type gives information about where a dictionary came from.
757 This is important for decent error message reporting because dictionaries
758 don't appear in the original source code. Doubtless this type will evolve...
760 It appears in TcMonad because there are a couple of error-message-generation
761 functions that deal with it.
764 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
766 instLocSrcLoc :: InstLoc -> SrcLoc
767 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
769 instLocSrcSpan :: InstLoc -> SrcSpan
770 instLocSrcSpan (InstLoc _ src_span _) = src_span
773 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
774 -- Places that bind type variables and introduce
775 -- available constraints
777 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
779 -------------------------------------------------------
780 -- The rest are all occurrences: Insts that are 'wanted'
781 -------------------------------------------------------
782 | OccurrenceOf Name -- Occurrence of an overloaded identifier
784 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
786 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
788 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
789 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
791 | InstSigOrigin -- A dict occurrence arising from instantiating
792 -- a polymorphic type during a subsumption check
795 | InstScOrigin -- Typechecking superclasses of an instance declaration
796 | DerivOrigin -- Typechecking deriving
797 | DefaultOrigin -- Typechecking a default decl
798 | DoOrigin -- Arising from a do expression
799 | ProcOrigin -- Arising from a proc expression
803 pprInstLoc :: InstLoc -> SDoc
804 pprInstLoc (InstLoc orig locn _)
805 = hsep [text "arising from", pp_orig orig, text "at", ppr locn]
807 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
808 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
809 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
810 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
811 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
812 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
813 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
814 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
815 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
816 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
817 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
818 pp_orig DoOrigin = ptext SLIT("a do statement")
819 pp_orig ProcOrigin = ptext SLIT("a proc expression")
820 pp_orig (SigOrigin info) = pprSkolInfo info