2 % (c) The University of Glasgow 2006
3 % (c) The GRASP Project, Glasgow University, 1992-2002
7 TcRnIf, TcRn, TcM, RnM, IfM, IfL, IfG, -- The monad is opaque outside this module
10 -- The environment types
12 TcGblEnv(..), TcLclEnv(..),
13 IfGblEnv(..), IfLclEnv(..),
17 ImportAvails(..), emptyImportAvails, plusImportAvails,
18 WhereFrom(..), mkModDeps,
21 TcTyThing(..), pprTcTyThingCategory,
24 ThStage(..), topStage, topSpliceStage,
25 ThLevel, impLevel, topLevel,
28 ArrowCtxt(NoArrowCtxt), newArrowScope, escapeArrowScope,
31 Inst(..), InstOrigin(..), InstLoc(..),
32 pprInstLoc, pprInstArising, instLocSpan, instLocOrigin,
33 LIE, emptyLIE, unitLIE, plusLIE, consLIE, instLoc, instSpan,
34 plusLIEs, mkLIE, isEmptyLIE, lieToList, listToLIE,
37 TcId, TcIdSet, TcDictBinds
40 #include "HsVersions.h"
42 import HsSyn hiding (LIE)
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
89 type TcRnIf a b c = IOEnv (Env a b) c
90 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
92 type IfG a = IfM () a -- Top level
93 type IfL a = IfM IfLclEnv a -- Nested
94 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
95 type RnM a = TcRn a -- Historical
96 type TcM a = TcRn a -- Historical
100 %************************************************************************
102 The main environment types
104 %************************************************************************
107 data Env gbl lcl -- Changes as we move into an expression
109 env_top :: HscEnv, -- Top-level stuff that never changes
110 -- Includes all info about imported things
112 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
113 -- 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
137 tcg_field_env :: RecFieldEnv, -- Just for things in this module
139 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
140 -- All TyCons and Classes (for this module) end up in here right away,
141 -- along with their derived constructors, selectors.
143 -- (Ids defined in this module start in the local envt,
144 -- though they move to the global envt during zonking)
146 tcg_type_env_var :: TcRef TypeEnv,
147 -- Used only to initialise the interface-file
148 -- typechecker in initIfaceTcRn, so that it can see stuff
149 -- bound in this module when dealing with hi-boot recursions
150 -- Updated at intervals (e.g. after dealing with types and classes)
152 tcg_inst_env :: InstEnv, -- Instance envt for *home-package*
153 -- modules; Includes the dfuns in
155 tcg_fam_inst_env :: FamInstEnv, -- Ditto for family instances
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 :: [AvailInfo], -- What is exported
162 tcg_imports :: ImportAvails, -- Information about what was imported
163 -- from where, including things bound
166 tcg_dus :: DefUses, -- What is defined in this module and what is used.
167 -- The latter is used to generate
168 -- (a) version tracking; no need to recompile if these
169 -- things have not changed version stamp
170 -- (b) unused-import info
172 tcg_keep :: TcRef NameSet, -- Locally-defined top-level names to keep alive
173 -- "Keep alive" means give them an Exported flag, so
174 -- that the simplifier does not discard them as dead
175 -- code, and so that they are exposed in the interface file
176 -- (but not to export to the user).
178 -- Some things, like dict-fun Ids and default-method Ids are
179 -- "born" with the Exported flag on, for exactly the above reason,
180 -- but some we only discover as we go. Specifically:
181 -- * The to/from functions for generic data types
182 -- * Top-level variables appearing free in the RHS of an orphan rule
183 -- * Top-level variables appearing free in a TH bracket
185 tcg_inst_uses :: TcRef NameSet, -- Home-package Dfuns actually used
186 -- Used to generate version dependencies
187 -- This records usages, rather like tcg_dus, but it has to
188 -- be a mutable variable so it can be augmented
189 -- when we look up an instance. These uses of dfuns are
190 -- rather like the free variables of the program, but
191 -- are implicit instead of explicit.
193 tcg_th_used :: TcRef Bool, -- True <=> Template Haskell syntax used
194 -- We need this so that we can generate a dependency on the
195 -- Template Haskell package, becuase the desugarer is going to
196 -- emit loads of references to TH symbols. It's rather like
197 -- tcg_inst_uses; the reference is implicit rather than explicit,
198 -- so we have to zap a mutable variable.
200 tcg_dfun_n :: TcRef Int, -- Allows us to number off the names of DFuns
201 -- It's convenient to allocate an External Name for a DFun, with
202 -- a permanently-fixed unique, just like other top-level functions
203 -- defined in this module. But that means we need a canonical
204 -- occurrence name, distinct from all other dfuns in this module,
205 -- and this name supply serves that purpose (df1, df2, etc).
207 -- The next fields accumulate the payload of the module
208 -- The binds, rules and foreign-decl fiels are collected
209 -- initially in un-zonked form and are finally zonked in tcRnSrcDecls
211 -- The next fields accumulate the payload of the
212 -- module The binds, rules and foreign-decl fiels are
213 -- collected initially in un-zonked form and are
214 -- finally zonked in tcRnSrcDecls
216 tcg_rn_imports :: Maybe [LImportDecl Name],
217 tcg_rn_exports :: Maybe [Located (IE Name)],
218 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
219 -- Nothing <=> Don't retain renamed decls
221 tcg_binds :: LHsBinds Id, -- Value bindings in this module
222 tcg_deprecs :: Deprecations, -- ...Deprecations
223 tcg_insts :: [Instance], -- ...Instances
224 tcg_fam_insts :: [FamInst], -- ...Family instances
225 tcg_rules :: [LRuleDecl Id], -- ...Rules
226 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
228 tcg_doc :: Maybe (HsDoc Name), -- Maybe Haddock documentation
229 tcg_hmi :: HaddockModInfo Name, -- Haddock module information
230 tcg_hpc :: AnyHpcUsage -- True if any part of the prog uses hpc instrumentation.
233 type RecFieldEnv = NameEnv [Name] -- Maps a constructor name *in this module*
234 -- to the fields for that constructor
235 -- This is used when dealing with ".." notation in record
236 -- construction and pattern matching.
237 -- The FieldEnv deals *only* with constructors defined in
238 -- *thie* module. For imported modules, we get the same info
242 %************************************************************************
244 The interface environments
245 Used when dealing with IfaceDecls
247 %************************************************************************
252 -- The type environment for the module being compiled,
253 -- in case the interface refers back to it via a reference that
254 -- was originally a hi-boot file.
255 -- We need the module name so we can test when it's appropriate
256 -- to look in this env.
257 if_rec_types :: Maybe (Module, IfG TypeEnv)
258 -- Allows a read effect, so it can be in a mutable
259 -- variable; c.f. handling the external package type env
260 -- Nothing => interactive stuff, no loops possible
265 -- The module for the current IfaceDecl
266 -- So if we see f = \x -> x
267 -- it means M.f = \x -> x, where M is the if_mod
270 -- The field is used only for error reporting
271 -- if (say) there's a Lint error in it
273 -- Where the interface came from:
274 -- .hi file, or GHCi state, or ext core
275 -- plus which bit is currently being examined
277 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
278 if_id_env :: UniqFM Id -- Nested id binding
283 %************************************************************************
285 The local typechecker environment
287 %************************************************************************
289 The Global-Env/Local-Env story
290 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
291 During type checking, we keep in the tcg_type_env
292 * All types and classes
293 * All Ids derived from types and classes (constructors, selectors)
295 At the end of type checking, we zonk the local bindings,
296 and as we do so we add to the tcg_type_env
297 * Locally defined top-level Ids
299 Why? Because they are now Ids not TcIds. This final GlobalEnv is
300 a) fed back (via the knot) to typechecking the
301 unfoldings of interface signatures
302 b) used in the ModDetails of this module
305 data TcLclEnv -- Changes as we move inside an expression
306 -- Discarded after typecheck/rename; not passed on to desugarer
308 tcl_loc :: SrcSpan, -- Source span
309 tcl_ctxt :: ErrCtxt, -- Error context
310 tcl_errs :: TcRef Messages, -- Place to accumulate errors
312 tcl_th_ctxt :: ThStage, -- Template Haskell context
313 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
315 tcl_rdr :: LocalRdrEnv, -- Local name envt
316 -- Maintained during renaming, of course, but also during
317 -- type checking, solely so that when renaming a Template-Haskell
318 -- splice we have the right environment for the renamer.
320 -- Used only for names bound within a value binding (bound by
321 -- lambda, case, where, let etc), but *not* for top-level names.
323 -- Does *not* include global name envt; may shadow it
324 -- Includes both ordinary variables and type variables;
325 -- they are kept distinct because tyvar have a different
326 -- occurrence contructor (Name.TvOcc)
328 -- We still need the unsullied global name env so that
329 -- we can look up record field names
331 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
332 -- defined in this module
334 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
335 -- Namely, the in-scope TyVars bound in tcl_env,
336 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
337 -- Why mutable? see notes with tcGetGlobalTyVars
339 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
343 {- Note [Given Insts]
345 Because of GADTs, we have to pass inwards the Insts provided by type signatures
346 and existential contexts. Consider
347 data T a where { T1 :: b -> b -> T [b] }
348 f :: Eq a => T a -> Bool
349 f (T1 x y) = [x]==[y]
351 The constructor T1 binds an existential variable 'b', and we need Eq [b].
352 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
357 ---------------------------
358 -- Template Haskell levels
359 ---------------------------
362 -- Indicates how many levels of brackets we are inside
364 -- Incremented when going inside a bracket,
365 -- decremented when going inside a splice
366 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
367 -- original "Template meta-programmign for Haskell" paper
369 impLevel, topLevel :: ThLevel
370 topLevel = 1 -- Things defined at top level of this module
371 impLevel = 0 -- Imported things; they can be used inside a top level splice
375 -- g1 = $(map ...) is OK
376 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
380 = Comp -- Ordinary compiling, at level topLevel
381 | Splice ThLevel -- Inside a splice
382 | Brack ThLevel -- Inside brackets;
383 (TcRef [PendingSplice]) -- accumulate pending splices here
384 (TcRef LIE) -- and type constraints here
385 topStage, topSpliceStage :: ThStage
387 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
389 ---------------------------
390 -- Arrow-notation context
391 ---------------------------
394 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
395 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
400 Here, x is not in scope in e1, but it is in scope in e2. This can get
404 proc y -> (proc z -> e1) -< e2
406 Here, x and z are in scope in e1, but y is not. We implement this by
407 recording the environment when passing a proc (using newArrowScope),
408 and returning to that (using escapeArrowScope) on the left of -< and the
414 | ArrowCtxt (Env TcGblEnv TcLclEnv)
416 -- Record the current environment (outside a proc)
417 newArrowScope :: TcM a -> TcM a
420 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
422 -- Return to the stored environment (from the enclosing proc)
423 escapeArrowScope :: TcM a -> TcM a
425 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
427 ArrowCtxt env' -> env'
429 ---------------------------
431 ---------------------------
434 = AGlobal TyThing -- Used only in the return type of a lookup
436 | ATcId { -- Ids defined in this module; may not be fully zonked
438 tct_co :: Maybe HsWrapper, -- Nothing <=> Do not apply a GADT type refinement
439 -- I am wobbly, or have no free
441 -- Just co <=> Apply any type refinement to me,
442 -- and record it in the coercion
443 tct_type :: TcType, -- Type of (coercion applied to id)
444 tct_level :: ThLevel }
446 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
447 -- is currently refined. We only need the Name
448 -- for error-message purposes
450 | AThing TcKind -- Used temporarily, during kind checking, for the
451 -- tycons and clases in this recursive group
453 instance Outputable TcTyThing where -- Debugging only
454 ppr (AGlobal g) = ppr g
455 ppr elt@(ATcId {}) = text "Identifier" <>
456 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
457 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
458 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
459 ppr (AThing k) = text "AThing" <+> ppr k
461 pprTcTyThingCategory :: TcTyThing -> SDoc
462 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
463 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
464 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
465 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
469 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
470 -- Innermost first. Monadic so that we have a chance
471 -- to deal with bound type variables just before error
472 -- message construction
476 %************************************************************************
478 Operations over ImportAvails
480 %************************************************************************
482 ImportAvails summarises what was imported from where, irrespective
483 of whether the imported things are actually used or not
484 It is used * when processing the export list
485 * when constructing usage info for the inteface file
486 * to identify the list of directly imported modules
487 for initialisation purposes and
488 for optimsed overlap checking of family instances
489 * when figuring out what things are really unused
494 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
495 -- Domain is all directly-imported modules
497 -- True => import was "import Foo ()"
498 -- False => import was some other form
500 -- We need the Module in the range because we can't get
501 -- the keys of a ModuleEnv
503 -- (a) to help construct the usage information in
504 -- the interface file; if we import somethign we
505 -- need to recompile if the export version changes
506 -- (b) to specify what child modules to initialise
508 -- We need a full ModuleEnv rather than a ModuleNameEnv
509 -- here, because we might be importing modules of the
510 -- same name from different packages. (currently not the case,
511 -- but might be in the future).
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 (and maybe
530 -- including us for imported modules)
532 imp_finsts :: [Module]
533 -- Family instance modules below us in the import tree (and
534 -- maybe including us for imported modules)
537 mkModDeps :: [(ModuleName, IsBootInterface)]
538 -> ModuleNameEnv (ModuleName, IsBootInterface)
539 mkModDeps deps = foldl add emptyUFM deps
541 add env elt@(m,_) = addToUFM env m elt
543 emptyImportAvails :: ImportAvails
544 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
545 imp_dep_mods = emptyUFM,
550 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
552 (ImportAvails { imp_mods = mods1,
553 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
554 imp_orphs = orphs1, imp_finsts = finsts1 })
555 (ImportAvails { imp_mods = mods2,
556 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
557 imp_orphs = orphs2, imp_finsts = finsts2 })
558 = ImportAvails { imp_mods = mods1 `plusModuleEnv` mods2,
559 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
560 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
561 imp_orphs = orphs1 `unionLists` orphs2,
562 imp_finsts = finsts1 `unionLists` finsts2 }
564 plus_mod_dep (m1, boot1) (m2, boot2)
565 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
566 -- Check mod-names match
567 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
570 %************************************************************************
572 \subsection{Where from}
574 %************************************************************************
576 The @WhereFrom@ type controls where the renamer looks for an interface file
580 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
581 | ImportBySystem -- Non user import.
583 instance Outputable WhereFrom where
584 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
586 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
590 %************************************************************************
592 \subsection[Inst-types]{@Inst@ types}
594 v%************************************************************************
596 An @Inst@ is either a dictionary, an instance of an overloaded
597 literal, or an instance of an overloaded value. We call the latter a
598 ``method'' even though it may not correspond to a class operation.
599 For example, we might have an instance of the @double@ function at
600 type Int, represented by
602 Method 34 doubleId [Int] origin
608 tci_pred :: TcPredType,
612 | ImplicInst { -- An implication constraint
613 -- forall tvs. (reft, given) => wanted
615 tci_tyvars :: [TcTyVar], -- Quantified type variables
616 -- Includes coercion variables
617 -- mentioned in tci_reft
618 tci_reft :: Refinement,
619 tci_given :: [Inst], -- Only Dicts
620 -- (no Methods, LitInsts, ImplicInsts)
621 tci_wanted :: [Inst], -- Only Dicts and ImplicInsts
622 -- (no Methods or LitInsts)
626 -- NB: the tci_given are not necessarily rigid,
627 -- although they will be if the tci_reft is non-trivial
628 -- NB: the tci_reft is already applied to tci_given and tci_wanted
631 tci_id :: TcId, -- The Id for the Inst
633 tci_oid :: TcId, -- The overloaded function
634 -- This function will be a global, local, or ClassOpId;
635 -- inside instance decls (only) it can also be an InstId!
636 -- The id needn't be completely polymorphic.
637 -- You'll probably find its name (for documentation purposes)
638 -- inside the InstOrigin
640 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
641 -- should be instantiated.
642 -- These types must saturate the Id's foralls.
644 tci_theta :: TcThetaType,
645 -- The (types of the) dictionaries to which the function
646 -- must be applied to get the method
650 -- INVARIANT 1: in (Method m f tys theta tau loc)
651 -- type of m = type of (f tys dicts(from theta))
653 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
654 -- Reason: two methods are considered equal if the
655 -- base Id matches, and the instantiating types
656 -- match. The TcThetaType should then match too.
657 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
661 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
662 -- INVARIANT: never a rebindable-syntax literal
663 -- Reason: tcSyntaxName does unification, and we
664 -- don't want to deal with that during tcSimplify,
665 -- when resolving LitInsts
667 tci_ty :: TcType, -- The type at which the literal is used
672 @Insts@ are ordered by their class/type info, rather than by their
673 unique. This allows the context-reduction mechanism to use standard finite
674 maps to do their stuff. It's horrible that this code is here, rather
675 than with the Avails handling stuff in TcSimplify
678 instance Ord Inst where
681 instance Eq Inst where
682 (==) i1 i2 = case i1 `cmpInst` i2 of
686 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
687 cmpInst (Dict {}) other = LT
689 cmpInst (Method {}) (Dict {}) = GT
690 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
691 (tci_tys m1 `tcCmpTypes` tci_tys m2)
692 cmpInst (Method {}) other = LT
694 cmpInst (LitInst {}) (Dict {}) = GT
695 cmpInst (LitInst {}) (Method {}) = GT
696 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
697 (tci_ty l1 `tcCmpType` tci_ty l2)
698 cmpInst (LitInst {}) other = LT
700 -- Implication constraints are compared by *name*
701 -- not by type; that is, we make no attempt to do CSE on them
702 cmpInst (ImplicInst {}) (Dict {}) = GT
703 cmpInst (ImplicInst {}) (Method {}) = GT
704 cmpInst (ImplicInst {}) (LitInst {}) = GT
705 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
709 %************************************************************************
711 \subsection[Inst-collections]{LIE: a collection of Insts}
713 %************************************************************************
716 -- FIXME: Rename this. It clashes with (Located (IE ...))
719 isEmptyLIE = isEmptyBag
721 unitLIE inst = unitBag inst
722 mkLIE insts = listToBag insts
723 plusLIE lie1 lie2 = lie1 `unionBags` lie2
724 plusLIEs lies = unionManyBags lies
725 lieToList = bagToList
726 listToLIE = listToBag
728 consLIE inst lie = lie `snocBag` inst
729 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
730 -- to ensure that we tend to report the *leftmost* type-constraint error
733 -- we'd like to complain about the '1', not the '3'.
735 -- "Half-hearted" because the rest of the type checker makes no great
736 -- claims for retaining order in the constraint set. Still, this
737 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
741 %************************************************************************
743 \subsection[Inst-origin]{The @InstOrigin@ type}
745 %************************************************************************
747 The @InstOrigin@ type gives information about where a dictionary came from.
748 This is important for decent error message reporting because dictionaries
749 don't appear in the original source code. Doubtless this type will evolve...
751 It appears in TcMonad because there are a couple of error-message-generation
752 functions that deal with it.
755 -------------------------------------------
756 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
758 instLoc :: Inst -> InstLoc
759 instLoc inst = tci_loc inst
761 instSpan :: Inst -> SrcSpan
762 instSpan wanted = instLocSpan (instLoc wanted)
764 instLocSpan :: InstLoc -> SrcSpan
765 instLocSpan (InstLoc _ s _) = s
767 instLocOrigin :: InstLoc -> InstOrigin
768 instLocOrigin (InstLoc o _ _) = o
770 pprInstArising :: Inst -> SDoc
771 pprInstArising loc = ptext SLIT("arising from") <+> pprInstLoc (tci_loc loc)
773 pprInstLoc :: InstLoc -> SDoc
774 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
776 -------------------------------------------
778 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
779 -- Places that bind type variables and introduce
780 -- available constraints
782 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
784 -------------------------------------------------------
785 -- The rest are all occurrences: Insts that are 'wanted'
786 -------------------------------------------------------
787 | OccurrenceOf Name -- Occurrence of an overloaded identifier
789 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
791 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
793 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
794 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
796 | InstSigOrigin -- A dict occurrence arising from instantiating
797 -- a polymorphic type during a subsumption check
800 | InstScOrigin -- Typechecking superclasses of an instance declaration
801 | DerivOrigin -- Typechecking deriving
802 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
803 | DefaultOrigin -- Typechecking a default decl
804 | DoOrigin -- Arising from a do expression
805 | ProcOrigin -- Arising from a proc expression
806 | ImplicOrigin SDoc -- An implication constraint
808 instance Outputable InstOrigin where
809 ppr (OccurrenceOf name) = hsep [ptext SLIT("a use of"), quotes (ppr name)]
810 ppr (IPOccOrigin name) = hsep [ptext SLIT("a use of implicit parameter"), quotes (ppr name)]
811 ppr (IPBindOrigin name) = hsep [ptext SLIT("a binding for implicit parameter"), quotes (ppr name)]
812 ppr RecordUpdOrigin = ptext SLIT("a record update")
813 ppr (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
814 ppr (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
815 ppr (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
816 ppr InstSigOrigin = ptext SLIT("instantiating a type signature")
817 ppr InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
818 ppr DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
819 ppr StandAloneDerivOrigin = ptext SLIT("a 'deriving' declaration")
820 ppr DefaultOrigin = ptext SLIT("a 'default' declaration")
821 ppr DoOrigin = ptext SLIT("a do statement")
822 ppr ProcOrigin = ptext SLIT("a proc expression")
823 ppr (ImplicOrigin doc) = doc
824 ppr (SigOrigin info) = pprSkolInfo info