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,
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, LImportDecl, HsGroup,
46 HsWrapper, IE, HsDoc, HaddockModInfo )
47 import HscTypes ( FixityEnv,
48 HscEnv, TypeEnv, TyThing,
49 GenAvailInfo(..), AvailInfo, HscSource(..),
50 availName, IsBootInterface, Deprecations )
51 import Packages ( PackageId )
52 import Type ( Type, pprTyThingCategory )
53 import TcType ( TcTyVarSet, TcType, TcThetaType, SkolemInfo,
54 TcPredType, TcKind, tcCmpPred, tcCmpType,
55 tcCmpTypes, pprSkolInfo )
56 import InstEnv ( Instance, InstEnv )
57 import FamInstEnv ( FamInstEnv )
59 import RdrName ( GlobalRdrEnv, LocalRdrEnv )
62 import NameSet ( NameSet, unionNameSets, DefUses )
63 import Var ( Id, TyVar )
64 import VarEnv ( TidyEnv )
67 import SrcLoc ( SrcSpan, SrcLoc, Located, srcSpanStart )
68 import VarSet ( IdSet )
69 import ErrUtils ( Messages, Message )
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*
158 -- modules; Includes the dfuns in
160 tcg_fam_inst_env :: FamInstEnv, -- Ditto for family instances
162 -- Now a bunch of things about this module that are simply
163 -- accumulated, but never consulted until the end.
164 -- Nevertheless, it's convenient to accumulate them along
165 -- with the rest of the info from this module.
166 tcg_exports :: NameSet, -- What is exported
167 tcg_imports :: ImportAvails, -- Information about what was imported
168 -- from where, including things bound
171 tcg_dus :: DefUses, -- What is defined in this module and what is used.
172 -- The latter is used to generate
173 -- (a) version tracking; no need to recompile if these
174 -- things have not changed version stamp
175 -- (b) unused-import info
177 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
178 -- "Keep alive" means give them an Exported flag, so
179 -- that the simplifier does not discard them as dead
180 -- code, and so that they are exposed in the interface file
181 -- (but not to export to the user).
183 -- Some things, like dict-fun Ids and default-method Ids are
184 -- "born" with the Exported flag on, for exactly the above reason,
185 -- but some we only discover as we go. Specifically:
186 -- * The to/from functions for generic data types
187 -- * Top-level variables appearing free in the RHS of an orphan rule
188 -- * Top-level variables appearing free in a TH bracket
190 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
191 -- Used to generate version dependencies
192 -- This records usages, rather like tcg_dus, but it has to
193 -- be a mutable variable so it can be augmented
194 -- when we look up an instance. These uses of dfuns are
195 -- rather like the free variables of the program, but
196 -- are implicit instead of explicit.
198 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
199 -- We need this so that we can generate a dependency on the
200 -- Template Haskell package, becuase the desugarer is going to
201 -- emit loads of references to TH symbols. It's rather like
202 -- tcg_inst_uses; the reference is implicit rather than explicit,
203 -- so we have to zap a mutable variable.
205 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
206 -- It's convenient to allocate an External Name for a DFun, with
207 -- a permanently-fixed unique, just like other top-level functions
208 -- defined in this module. But that means we need a canonical
209 -- occurrence name, distinct from all other dfuns in this module,
210 -- and this name supply serves that purpose (df1, df2, etc).
212 -- The next fields accumulate the payload of the module
213 -- The binds, rules and foreign-decl fiels are collected
214 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
216 -- The next fields accumulate the payload of the
217 -- module The binds, rules and foreign-decl fiels are
218 -- collected initially in un-zonked form and are
219 -- finally zonked in tcRnSrcDecls
221 tcg_rn_imports :: Maybe [LImportDecl Name],
222 tcg_rn_exports :: Maybe [Located (IE Name)],
223 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
224 -- Nothing <=> Don't retain renamed decls
226 tcg_binds :: LHsBinds Id, -- Value bindings in this module
227 tcg_deprecs :: Deprecations, -- ...Deprecations
228 tcg_insts :: [Instance], -- ...Instances
229 tcg_rules :: [LRuleDecl Id], -- ...Rules
230 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
232 tcg_doc :: Maybe (HsDoc Name), -- Maybe Haddock documentation
233 tcg_hmi :: HaddockModInfo Name -- Haddock module information
237 %************************************************************************
239 The interface environments
240 Used when dealing with IfaceDecls
242 %************************************************************************
247 -- The type environment for the module being compiled,
248 -- in case the interface refers back to it via a reference that
249 -- was originally a hi-boot file.
250 -- We need the module name so we can test when it's appropriate
251 -- to look in this env.
252 if_rec_types :: Maybe (Module, IfG TypeEnv)
253 -- Allows a read effect, so it can be in a mutable
254 -- variable; c.f. handling the external package type env
255 -- Nothing => interactive stuff, no loops possible
260 -- The module for the current IfaceDecl
261 -- So if we see f = \x -> x
262 -- it means M.f = \x -> x, where M is the if_mod
265 -- The field is used only for error reporting
266 -- if (say) there's a Lint error in it
268 -- Where the interface came from:
269 -- .hi file, or GHCi state, or ext core
270 -- plus which bit is currently being examined
272 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
273 if_id_env :: UniqFM Id -- Nested id binding
278 %************************************************************************
280 The local typechecker environment
282 %************************************************************************
284 The Global-Env/Local-Env story
285 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
286 During type checking, we keep in the tcg_type_env
287 * All types and classes
288 * All Ids derived from types and classes (constructors, selectors)
290 At the end of type checking, we zonk the local bindings,
291 and as we do so we add to the tcg_type_env
292 * Locally defined top-level Ids
294 Why? Because they are now Ids not TcIds. This final GlobalEnv is
295 a) fed back (via the knot) to typechecking the
296 unfoldings of interface signatures
297 b) used in the ModDetails of this module
300 data TcLclEnv -- Changes as we move inside an expression
301 -- Discarded after typecheck/rename; not passed on to desugarer
303 tcl_loc :: SrcSpan, -- Source span
304 tcl_ctxt :: ErrCtxt, -- Error context
305 tcl_errs :: TcRef Messages, -- Place to accumulate errors
307 tcl_th_ctxt :: ThStage, -- Template Haskell context
308 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
310 tcl_rdr :: LocalRdrEnv, -- Local name envt
311 -- Maintained during renaming, of course, but also during
312 -- type checking, solely so that when renaming a Template-Haskell
313 -- splice we have the right environment for the renamer.
315 -- Does *not* include global name envt; may shadow it
316 -- Includes both ordinary variables and type variables;
317 -- they are kept distinct because tyvar have a different
318 -- occurrence contructor (Name.TvOcc)
319 -- We still need the unsullied global name env so that
320 -- we can look up record field names
322 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
323 -- defined in this module
325 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
326 -- Namely, the in-scope TyVars bound in tcl_env,
327 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
328 -- Why mutable? see notes with tcGetGlobalTyVars
330 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
334 {- Note [Given Insts]
336 Because of GADTs, we have to pass inwards the Insts provided by type signatures
337 and existential contexts. Consider
338 data T a where { T1 :: b -> b -> T [b] }
339 f :: Eq a => T a -> Bool
340 f (T1 x y) = [x]==[y]
342 The constructor T1 binds an existential variable 'b', and we need Eq [b].
343 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
348 ---------------------------
349 -- Template Haskell levels
350 ---------------------------
353 -- Indicates how many levels of brackets we are inside
355 -- Incremented when going inside a bracket,
356 -- decremented when going inside a splice
357 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
358 -- original "Template meta-programmign for Haskell" paper
360 impLevel, topLevel :: ThLevel
361 topLevel = 1 -- Things defined at top level of this module
362 impLevel = 0 -- Imported things; they can be used inside a top level splice
366 -- g1 = $(map ...) is OK
367 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
371 = Comp -- Ordinary compiling, at level topLevel
372 | Splice ThLevel -- Inside a splice
373 | Brack ThLevel -- Inside brackets;
374 (TcRef [PendingSplice]) -- accumulate pending splices here
375 (TcRef LIE) -- and type constraints here
376 topStage, topSpliceStage :: ThStage
378 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
380 ---------------------------
381 -- Arrow-notation context
382 ---------------------------
385 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
386 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
391 Here, x is not in scope in e1, but it is in scope in e2. This can get
395 proc y -> (proc z -> e1) -< e2
397 Here, x and z are in scope in e1, but y is not. We implement this by
398 recording the environment when passing a proc (using newArrowScope),
399 and returning to that (using escapeArrowScope) on the left of -< and the
405 | ArrowCtxt (Env TcGblEnv TcLclEnv)
407 -- Record the current environment (outside a proc)
408 newArrowScope :: TcM a -> TcM a
411 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
413 -- Return to the stored environment (from the enclosing proc)
414 escapeArrowScope :: TcM a -> TcM a
416 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
418 ArrowCtxt env' -> env'
420 ---------------------------
422 ---------------------------
425 = AGlobal TyThing -- Used only in the return type of a lookup
427 | ATcId { -- Ids defined in this module; may not be fully zonked
429 tct_co :: Maybe HsWrapper, -- Nothing <=> Do not apply a GADT type refinement
430 -- I am wobbly, or have no free
432 -- Just co <=> Apply any type refinement to me,
433 -- and record it in the coercion
434 tct_type :: TcType, -- Type of (coercion applied to id)
435 tct_level :: ThLevel }
437 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
438 -- is currently refined. We only need the Name
439 -- for error-message purposes
441 | AThing TcKind -- Used temporarily, during kind checking, for the
442 -- tycons and clases in this recursive group
444 instance Outputable TcTyThing where -- Debugging only
445 ppr (AGlobal g) = ppr g
446 ppr elt@(ATcId {}) = text "Identifier" <>
447 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
448 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
449 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
450 ppr (AThing k) = text "AThing" <+> ppr k
452 pprTcTyThingCategory :: TcTyThing -> SDoc
453 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
454 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
455 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
456 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
460 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
461 -- Innermost first. Monadic so that we have a chance
462 -- to deal with bound type variables just before error
463 -- message construction
467 %************************************************************************
469 Operations over ImportAvails
471 %************************************************************************
473 ImportAvails summarises what was imported from where, irrespective
474 of whether the imported things are actually used or not
475 It is used * when processing the export list
476 * when constructing usage info for the inteface file
477 * to identify the list of directly imported modules
478 for initialisation purposes
479 * when figuring out what things are really unused
484 imp_env :: ModuleNameEnv NameSet,
485 -- All the things imported, classified by
486 -- the *module qualifier* for its import
487 -- e.g. import List as Foo
488 -- would add a binding Foo |-> ...stuff from List...
491 -- We need to classify them like this so that we can figure out
492 -- "module M" export specifiers in an export list
493 -- (see 1.4 Report Section 5.1.1). Ultimately, we want to find
494 -- everything that is unambiguously in scope as 'M.x'
495 -- and where plain 'x' is (perhaps ambiguously) in scope.
496 -- So the starting point is all things that are in scope as 'M.x',
497 -- which is what this field tells us.
499 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
500 -- Domain is all directly-imported modules
502 -- True => import was "import Foo ()"
503 -- False => import was some other form
505 -- We need the Module in the range because we can't get
506 -- the keys of a ModuleEnv
508 -- (a) to help construct the usage information in
509 -- the interface file; if we import somethign we
510 -- need to recompile if the export version changes
511 -- (b) to specify what child modules to initialise
513 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
514 -- Home-package modules needed by the module being compiled
516 -- It doesn't matter whether any of these dependencies
517 -- are actually *used* when compiling the module; they
518 -- are listed if they are below it at all. For
519 -- example, suppose M imports A which imports X. Then
520 -- compiling M might not need to consult X.hi, but X
521 -- is still listed in M's dependencies.
523 imp_dep_pkgs :: [PackageId],
524 -- Packages needed by the module being compiled, whether
525 -- directly, or via other modules in this package, or via
526 -- modules imported from other packages.
528 imp_orphs :: [Module]
529 -- Orphan modules below us in the import tree
532 mkModDeps :: [(ModuleName, IsBootInterface)]
533 -> ModuleNameEnv (ModuleName, IsBootInterface)
534 mkModDeps deps = foldl add emptyUFM deps
536 add env elt@(m,_) = addToUFM env m elt
538 emptyImportAvails :: ImportAvails
539 emptyImportAvails = ImportAvails { imp_env = emptyUFM,
540 imp_mods = emptyModuleEnv,
541 imp_dep_mods = emptyUFM,
545 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
547 (ImportAvails { imp_env = env1, imp_mods = mods1,
548 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1, imp_orphs = orphs1 })
549 (ImportAvails { imp_env = env2, imp_mods = mods2,
550 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2, imp_orphs = orphs2 })
551 = ImportAvails { imp_env = plusUFM_C unionNameSets env1 env2,
552 imp_mods = mods1 `plusModuleEnv` mods2,
553 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
554 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
555 imp_orphs = orphs1 `unionLists` orphs2 }
557 plus_mod_dep (m1, boot1) (m2, boot2)
558 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
559 -- Check mod-names match
560 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
563 %************************************************************************
565 Avails, AvailEnv, etc
567 v%************************************************************************
570 plusAvail (Avail n1) (Avail n2) = Avail n1
571 plusAvail (AvailTC n1 ns1) (AvailTC n2 ns2) = AvailTC n2 (ns1 `unionLists` ns2)
574 plusAvail a1 a2 = pprPanic "RnEnv.plusAvail" (hsep [ppr a1,ppr a2])
577 -------------------------
578 pruneAvails :: (Name -> Bool) -- Keep if this is True
581 pruneAvails keep avails
582 = mapMaybe del avails
584 del :: AvailInfo -> Maybe AvailInfo -- Nothing => nothing left!
585 del (Avail n) | keep n = Just (Avail n)
586 | otherwise = Nothing
587 del (AvailTC n ns) | null ns' = Nothing
588 | otherwise = Just (AvailTC n ns')
593 ---------------------------------------
595 ---------------------------------------
598 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
600 emptyAvailEnv :: AvailEnv
601 emptyAvailEnv = emptyNameEnv
603 unitAvailEnv :: AvailInfo -> AvailEnv
604 unitAvailEnv a = unitNameEnv (availName a) a
606 plusAvailEnv :: AvailEnv -> AvailEnv -> AvailEnv
607 plusAvailEnv = plusNameEnv_C plusAvail
609 lookupAvailEnv_maybe :: AvailEnv -> Name -> Maybe AvailInfo
610 lookupAvailEnv_maybe = lookupNameEnv
612 lookupAvailEnv :: AvailEnv -> Name -> AvailInfo
613 lookupAvailEnv env n = case lookupNameEnv env n of
615 Nothing -> pprPanic "lookupAvailEnv" (ppr n)
617 availEnvElts = nameEnvElts
619 addAvail :: AvailEnv -> AvailInfo -> AvailEnv
620 addAvail avails avail = extendNameEnv_C plusAvail avails (availName avail) avail
622 mkAvailEnv :: [AvailInfo] -> AvailEnv
623 -- 'avails' may have several items with the same availName
624 -- E.g import Ix( Ix(..), index )
625 -- will give Ix(Ix,index,range) and Ix(index)
626 -- We want to combine these; addAvail does that
627 mkAvailEnv avails = foldl addAvail emptyAvailEnv avails
630 %************************************************************************
632 \subsection{Where from}
634 %************************************************************************
636 The @WhereFrom@ type controls where the renamer looks for an interface file
640 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
641 | ImportBySystem -- Non user import.
643 instance Outputable WhereFrom where
644 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
646 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
650 %************************************************************************
652 \subsection[Inst-types]{@Inst@ types}
654 v%************************************************************************
656 An @Inst@ is either a dictionary, an instance of an overloaded
657 literal, or an instance of an overloaded value. We call the latter a
658 ``method'' even though it may not correspond to a class operation.
659 For example, we might have an instance of the @double@ function at
660 type Int, represented by
662 Method 34 doubleId [Int] origin
674 TcId -- The overloaded function
675 -- This function will be a global, local, or ClassOpId;
676 -- inside instance decls (only) it can also be an InstId!
677 -- The id needn't be completely polymorphic.
678 -- You'll probably find its name (for documentation purposes)
679 -- inside the InstOrigin
681 [TcType] -- The types to which its polymorphic tyvars
682 -- should be instantiated.
683 -- These types must saturate the Id's foralls.
685 TcThetaType -- The (types of the) dictionaries to which the function
686 -- must be applied to get the method
690 -- INVARIANT 1: in (Method u f tys theta tau loc)
691 -- type of (f tys dicts(from theta)) = tau
693 -- INVARIANT 2: tau must not be of form (Pred -> Tau)
694 -- Reason: two methods are considered equal if the
695 -- base Id matches, and the instantiating types
696 -- match. The TcThetaType should then match too.
697 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
701 (HsOverLit Name) -- The literal from the occurrence site
702 -- INVARIANT: never a rebindable-syntax literal
703 -- Reason: tcSyntaxName does unification, and we
704 -- don't want to deal with that during tcSimplify,
705 -- when resolving LitInsts
706 TcType -- The type at which the literal is used
710 @Insts@ are ordered by their class/type info, rather than by their
711 unique. This allows the context-reduction mechanism to use standard finite
712 maps to do their stuff.
715 instance Ord Inst where
718 instance Eq Inst where
719 (==) i1 i2 = case i1 `cmpInst` i2 of
723 cmpInst (Dict _ pred1 _) (Dict _ pred2 _) = pred1 `tcCmpPred` pred2
724 cmpInst (Dict _ _ _) other = LT
726 cmpInst (Method _ _ _ _ _) (Dict _ _ _) = GT
727 cmpInst (Method _ id1 tys1 _ _) (Method _ id2 tys2 _ _) = (id1 `compare` id2) `thenCmp` (tys1 `tcCmpTypes` tys2)
728 cmpInst (Method _ _ _ _ _) other = LT
730 cmpInst (LitInst _ _ _ _) (Dict _ _ _) = GT
731 cmpInst (LitInst _ _ _ _) (Method _ _ _ _ _) = GT
732 cmpInst (LitInst _ lit1 ty1 _) (LitInst _ lit2 ty2 _) = (lit1 `compare` lit2) `thenCmp` (ty1 `tcCmpType` ty2)
736 %************************************************************************
738 \subsection[Inst-collections]{LIE: a collection of Insts}
740 %************************************************************************
743 -- FIXME: Rename this. It clashes with (Located (IE ...))
746 isEmptyLIE = isEmptyBag
748 unitLIE inst = unitBag inst
749 mkLIE insts = listToBag insts
750 plusLIE lie1 lie2 = lie1 `unionBags` lie2
751 consLIE inst lie = inst `consBag` lie
752 plusLIEs lies = unionManyBags lies
753 lieToList = bagToList
754 listToLIE = listToBag
758 %************************************************************************
760 \subsection[Inst-origin]{The @InstOrigin@ type}
762 %************************************************************************
764 The @InstOrigin@ type gives information about where a dictionary came from.
765 This is important for decent error message reporting because dictionaries
766 don't appear in the original source code. Doubtless this type will evolve...
768 It appears in TcMonad because there are a couple of error-message-generation
769 functions that deal with it.
772 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
774 instLocSrcLoc :: InstLoc -> SrcLoc
775 instLocSrcLoc (InstLoc _ src_span _) = srcSpanStart src_span
777 instLocSrcSpan :: InstLoc -> SrcSpan
778 instLocSrcSpan (InstLoc _ src_span _) = src_span
781 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
782 -- Places that bind type variables and introduce
783 -- available constraints
785 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
787 -------------------------------------------------------
788 -- The rest are all occurrences: Insts that are 'wanted'
789 -------------------------------------------------------
790 | OccurrenceOf Name -- Occurrence of an overloaded identifier
792 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
794 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
796 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
797 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
799 | InstSigOrigin -- A dict occurrence arising from instantiating
800 -- a polymorphic type during a subsumption check
803 | InstScOrigin -- Typechecking superclasses of an instance declaration
804 | DerivOrigin -- Typechecking deriving
805 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
806 | DefaultOrigin -- Typechecking a default decl
807 | DoOrigin -- Arising from a do expression
808 | ProcOrigin -- Arising from a proc expression
812 pprInstLoc :: InstLoc -> SDoc
813 pprInstLoc (InstLoc orig locn _)
814 = sep [text "arising from" <+> pp_orig orig,
815 text "at" <+> ppr locn]
817 pp_orig (OccurrenceOf name) = hsep [ptext SLIT("use of"), quotes (ppr name)]
818 pp_orig (IPOccOrigin name) = hsep [ptext SLIT("use of implicit parameter"), quotes (ppr name)]
819 pp_orig (IPBindOrigin name) = hsep [ptext SLIT("binding for implicit parameter"), quotes (ppr name)]
820 pp_orig RecordUpdOrigin = ptext SLIT("a record update")
821 pp_orig (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
822 pp_orig (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
823 pp_orig (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
824 pp_orig InstSigOrigin = ptext SLIT("instantiating a type signature")
825 pp_orig InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
826 pp_orig DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
827 pp_orig StandAloneDerivOrigin = ptext SLIT("a 'deriving' declaration")
828 pp_orig DefaultOrigin = ptext SLIT("a 'default' declaration")
829 pp_orig DoOrigin = ptext SLIT("a do statement")
830 pp_orig ProcOrigin = ptext SLIT("a proc expression")
831 pp_orig (SigOrigin info) = pprSkolInfo info