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
232 type RecFieldEnv = NameEnv [Name] -- Maps a constructor name *in this module*
233 -- to the fields for that constructor
234 -- This is used when dealing with ".." notation in record
235 -- construction and pattern matching.
236 -- The FieldEnv deals *only* with constructors defined in
237 -- *thie* module. For imported modules, we get the same info
241 %************************************************************************
243 The interface environments
244 Used when dealing with IfaceDecls
246 %************************************************************************
251 -- The type environment for the module being compiled,
252 -- in case the interface refers back to it via a reference that
253 -- was originally a hi-boot file.
254 -- We need the module name so we can test when it's appropriate
255 -- to look in this env.
256 if_rec_types :: Maybe (Module, IfG TypeEnv)
257 -- Allows a read effect, so it can be in a mutable
258 -- variable; c.f. handling the external package type env
259 -- Nothing => interactive stuff, no loops possible
264 -- The module for the current IfaceDecl
265 -- So if we see f = \x -> x
266 -- it means M.f = \x -> x, where M is the if_mod
269 -- The field is used only for error reporting
270 -- if (say) there's a Lint error in it
272 -- Where the interface came from:
273 -- .hi file, or GHCi state, or ext core
274 -- plus which bit is currently being examined
276 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
277 if_id_env :: UniqFM Id -- Nested id binding
282 %************************************************************************
284 The local typechecker environment
286 %************************************************************************
288 The Global-Env/Local-Env story
289 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
290 During type checking, we keep in the tcg_type_env
291 * All types and classes
292 * All Ids derived from types and classes (constructors, selectors)
294 At the end of type checking, we zonk the local bindings,
295 and as we do so we add to the tcg_type_env
296 * Locally defined top-level Ids
298 Why? Because they are now Ids not TcIds. This final GlobalEnv is
299 a) fed back (via the knot) to typechecking the
300 unfoldings of interface signatures
301 b) used in the ModDetails of this module
304 data TcLclEnv -- Changes as we move inside an expression
305 -- Discarded after typecheck/rename; not passed on to desugarer
307 tcl_loc :: SrcSpan, -- Source span
308 tcl_ctxt :: ErrCtxt, -- Error context
309 tcl_errs :: TcRef Messages, -- Place to accumulate errors
311 tcl_th_ctxt :: ThStage, -- Template Haskell context
312 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
314 tcl_rdr :: LocalRdrEnv, -- Local name envt
315 -- Maintained during renaming, of course, but also during
316 -- type checking, solely so that when renaming a Template-Haskell
317 -- splice we have the right environment for the renamer.
319 -- Used only for names bound within a value binding (bound by
320 -- lambda, case, where, let etc), but *not* for top-level names.
322 -- Does *not* include global name envt; may shadow it
323 -- Includes both ordinary variables and type variables;
324 -- they are kept distinct because tyvar have a different
325 -- occurrence contructor (Name.TvOcc)
327 -- We still need the unsullied global name env so that
328 -- we can look up record field names
330 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
331 -- defined in this module
333 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
334 -- Namely, the in-scope TyVars bound in tcl_env,
335 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
336 -- Why mutable? see notes with tcGetGlobalTyVars
338 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
342 {- Note [Given Insts]
344 Because of GADTs, we have to pass inwards the Insts provided by type signatures
345 and existential contexts. Consider
346 data T a where { T1 :: b -> b -> T [b] }
347 f :: Eq a => T a -> Bool
348 f (T1 x y) = [x]==[y]
350 The constructor T1 binds an existential variable 'b', and we need Eq [b].
351 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
356 ---------------------------
357 -- Template Haskell levels
358 ---------------------------
361 -- Indicates how many levels of brackets we are inside
363 -- Incremented when going inside a bracket,
364 -- decremented when going inside a splice
365 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
366 -- original "Template meta-programmign for Haskell" paper
368 impLevel, topLevel :: ThLevel
369 topLevel = 1 -- Things defined at top level of this module
370 impLevel = 0 -- Imported things; they can be used inside a top level splice
374 -- g1 = $(map ...) is OK
375 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
379 = Comp -- Ordinary compiling, at level topLevel
380 | Splice ThLevel -- Inside a splice
381 | Brack ThLevel -- Inside brackets;
382 (TcRef [PendingSplice]) -- accumulate pending splices here
383 (TcRef LIE) -- and type constraints here
384 topStage, topSpliceStage :: ThStage
386 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
388 ---------------------------
389 -- Arrow-notation context
390 ---------------------------
393 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
394 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
399 Here, x is not in scope in e1, but it is in scope in e2. This can get
403 proc y -> (proc z -> e1) -< e2
405 Here, x and z are in scope in e1, but y is not. We implement this by
406 recording the environment when passing a proc (using newArrowScope),
407 and returning to that (using escapeArrowScope) on the left of -< and the
413 | ArrowCtxt (Env TcGblEnv TcLclEnv)
415 -- Record the current environment (outside a proc)
416 newArrowScope :: TcM a -> TcM a
419 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
421 -- Return to the stored environment (from the enclosing proc)
422 escapeArrowScope :: TcM a -> TcM a
424 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
426 ArrowCtxt env' -> env'
428 ---------------------------
430 ---------------------------
433 = AGlobal TyThing -- Used only in the return type of a lookup
435 | ATcId { -- Ids defined in this module; may not be fully zonked
437 tct_co :: Maybe HsWrapper, -- Nothing <=> Do not apply a GADT type refinement
438 -- I am wobbly, or have no free
440 -- Just co <=> Apply any type refinement to me,
441 -- and record it in the coercion
442 tct_type :: TcType, -- Type of (coercion applied to id)
443 tct_level :: ThLevel }
445 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
446 -- is currently refined. We only need the Name
447 -- for error-message purposes
449 | AThing TcKind -- Used temporarily, during kind checking, for the
450 -- tycons and clases in this recursive group
452 instance Outputable TcTyThing where -- Debugging only
453 ppr (AGlobal g) = ppr g
454 ppr elt@(ATcId {}) = text "Identifier" <>
455 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
456 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
457 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
458 ppr (AThing k) = text "AThing" <+> ppr k
460 pprTcTyThingCategory :: TcTyThing -> SDoc
461 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
462 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
463 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
464 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
468 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
469 -- Innermost first. Monadic so that we have a chance
470 -- to deal with bound type variables just before error
471 -- message construction
475 %************************************************************************
477 Operations over ImportAvails
479 %************************************************************************
481 ImportAvails summarises what was imported from where, irrespective
482 of whether the imported things are actually used or not
483 It is used * when processing the export list
484 * when constructing usage info for the inteface file
485 * to identify the list of directly imported modules
486 for initialisation purposes and
487 for optimsed overlap checking of family instances
488 * when figuring out what things are really unused
493 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
494 -- Domain is all directly-imported modules
496 -- True => import was "import Foo ()"
497 -- False => import was some other form
499 -- We need the Module in the range because we can't get
500 -- the keys of a ModuleEnv
502 -- (a) to help construct the usage information in
503 -- the interface file; if we import somethign we
504 -- need to recompile if the export version changes
505 -- (b) to specify what child modules to initialise
507 -- We need a full ModuleEnv rather than a ModuleNameEnv
508 -- here, because we might be importing modules of the
509 -- same name from different packages. (currently not the case,
510 -- but might be in the future).
512 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
513 -- Home-package modules needed by the module being compiled
515 -- It doesn't matter whether any of these dependencies
516 -- are actually *used* when compiling the module; they
517 -- are listed if they are below it at all. For
518 -- example, suppose M imports A which imports X. Then
519 -- compiling M might not need to consult X.hi, but X
520 -- is still listed in M's dependencies.
522 imp_dep_pkgs :: [PackageId],
523 -- Packages needed by the module being compiled, whether
524 -- directly, or via other modules in this package, or via
525 -- modules imported from other packages.
527 imp_orphs :: [Module],
528 -- Orphan modules below us in the import tree (and maybe
529 -- including us for imported modules)
531 imp_finsts :: [Module]
532 -- Family instance modules below us in the import tree (and
533 -- maybe including us for imported modules)
536 mkModDeps :: [(ModuleName, IsBootInterface)]
537 -> ModuleNameEnv (ModuleName, IsBootInterface)
538 mkModDeps deps = foldl add emptyUFM deps
540 add env elt@(m,_) = addToUFM env m elt
542 emptyImportAvails :: ImportAvails
543 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
544 imp_dep_mods = emptyUFM,
549 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
551 (ImportAvails { imp_mods = mods1,
552 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
553 imp_orphs = orphs1, imp_finsts = finsts1 })
554 (ImportAvails { imp_mods = mods2,
555 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
556 imp_orphs = orphs2, imp_finsts = finsts2 })
557 = ImportAvails { imp_mods = mods1 `plusModuleEnv` mods2,
558 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
559 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
560 imp_orphs = orphs1 `unionLists` orphs2,
561 imp_finsts = finsts1 `unionLists` finsts2 }
563 plus_mod_dep (m1, boot1) (m2, boot2)
564 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
565 -- Check mod-names match
566 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
569 %************************************************************************
571 \subsection{Where from}
573 %************************************************************************
575 The @WhereFrom@ type controls where the renamer looks for an interface file
579 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
580 | ImportBySystem -- Non user import.
582 instance Outputable WhereFrom where
583 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
585 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
589 %************************************************************************
591 \subsection[Inst-types]{@Inst@ types}
593 v%************************************************************************
595 An @Inst@ is either a dictionary, an instance of an overloaded
596 literal, or an instance of an overloaded value. We call the latter a
597 ``method'' even though it may not correspond to a class operation.
598 For example, we might have an instance of the @double@ function at
599 type Int, represented by
601 Method 34 doubleId [Int] origin
607 tci_pred :: TcPredType,
611 | ImplicInst { -- An implication constraint
612 -- forall tvs. (reft, given) => wanted
614 tci_tyvars :: [TcTyVar], -- Quantified type variables
615 -- Includes coercion variables
616 -- mentioned in tci_reft
617 tci_reft :: Refinement,
618 tci_given :: [Inst], -- Only Dicts
619 -- (no Methods, LitInsts, ImplicInsts)
620 tci_wanted :: [Inst], -- Only Dicts and ImplicInsts
621 -- (no Methods or LitInsts)
625 -- NB: the tci_given are not necessarily rigid,
626 -- although they will be if the tci_reft is non-trivial
627 -- NB: the tci_reft is already applied to tci_given and tci_wanted
630 tci_id :: TcId, -- The Id for the Inst
632 tci_oid :: TcId, -- The overloaded function
633 -- This function will be a global, local, or ClassOpId;
634 -- inside instance decls (only) it can also be an InstId!
635 -- The id needn't be completely polymorphic.
636 -- You'll probably find its name (for documentation purposes)
637 -- inside the InstOrigin
639 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
640 -- should be instantiated.
641 -- These types must saturate the Id's foralls.
643 tci_theta :: TcThetaType,
644 -- The (types of the) dictionaries to which the function
645 -- must be applied to get the method
649 -- INVARIANT 1: in (Method m f tys theta tau loc)
650 -- type of m = type of (f tys dicts(from theta))
652 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
653 -- Reason: two methods are considered equal if the
654 -- base Id matches, and the instantiating types
655 -- match. The TcThetaType should then match too.
656 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
660 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
661 -- INVARIANT: never a rebindable-syntax literal
662 -- Reason: tcSyntaxName does unification, and we
663 -- don't want to deal with that during tcSimplify,
664 -- when resolving LitInsts
666 tci_ty :: TcType, -- The type at which the literal is used
671 @Insts@ are ordered by their class/type info, rather than by their
672 unique. This allows the context-reduction mechanism to use standard finite
673 maps to do their stuff. It's horrible that this code is here, rather
674 than with the Avails handling stuff in TcSimplify
677 instance Ord Inst where
680 instance Eq Inst where
681 (==) i1 i2 = case i1 `cmpInst` i2 of
685 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
686 cmpInst (Dict {}) other = LT
688 cmpInst (Method {}) (Dict {}) = GT
689 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
690 (tci_tys m1 `tcCmpTypes` tci_tys m2)
691 cmpInst (Method {}) other = LT
693 cmpInst (LitInst {}) (Dict {}) = GT
694 cmpInst (LitInst {}) (Method {}) = GT
695 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
696 (tci_ty l1 `tcCmpType` tci_ty l2)
697 cmpInst (LitInst {}) other = LT
699 -- Implication constraints are compared by *name*
700 -- not by type; that is, we make no attempt to do CSE on them
701 cmpInst (ImplicInst {}) (Dict {}) = GT
702 cmpInst (ImplicInst {}) (Method {}) = GT
703 cmpInst (ImplicInst {}) (LitInst {}) = GT
704 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
708 %************************************************************************
710 \subsection[Inst-collections]{LIE: a collection of Insts}
712 %************************************************************************
715 -- FIXME: Rename this. It clashes with (Located (IE ...))
718 isEmptyLIE = isEmptyBag
720 unitLIE inst = unitBag inst
721 mkLIE insts = listToBag insts
722 plusLIE lie1 lie2 = lie1 `unionBags` lie2
723 plusLIEs lies = unionManyBags lies
724 lieToList = bagToList
725 listToLIE = listToBag
727 consLIE inst lie = lie `snocBag` inst
728 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
729 -- to ensure that we tend to report the *leftmost* type-constraint error
732 -- we'd like to complain about the '1', not the '3'.
734 -- "Half-hearted" because the rest of the type checker makes no great
735 -- claims for retaining order in the constraint set. Still, this
736 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
740 %************************************************************************
742 \subsection[Inst-origin]{The @InstOrigin@ type}
744 %************************************************************************
746 The @InstOrigin@ type gives information about where a dictionary came from.
747 This is important for decent error message reporting because dictionaries
748 don't appear in the original source code. Doubtless this type will evolve...
750 It appears in TcMonad because there are a couple of error-message-generation
751 functions that deal with it.
754 -------------------------------------------
755 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
757 instLoc :: Inst -> InstLoc
758 instLoc inst = tci_loc inst
760 instSpan :: Inst -> SrcSpan
761 instSpan wanted = instLocSpan (instLoc wanted)
763 instLocSpan :: InstLoc -> SrcSpan
764 instLocSpan (InstLoc _ s _) = s
766 instLocOrigin :: InstLoc -> InstOrigin
767 instLocOrigin (InstLoc o _ _) = o
769 pprInstArising :: Inst -> SDoc
770 pprInstArising loc = ptext SLIT("arising from") <+> pprInstLoc (tci_loc loc)
772 pprInstLoc :: InstLoc -> SDoc
773 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
775 -------------------------------------------
777 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
778 -- Places that bind type variables and introduce
779 -- available constraints
781 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
783 -------------------------------------------------------
784 -- The rest are all occurrences: Insts that are 'wanted'
785 -------------------------------------------------------
786 | OccurrenceOf Name -- Occurrence of an overloaded identifier
788 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
790 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
792 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
793 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
795 | InstSigOrigin -- A dict occurrence arising from instantiating
796 -- a polymorphic type during a subsumption check
799 | InstScOrigin -- Typechecking superclasses of an instance declaration
800 | DerivOrigin -- Typechecking deriving
801 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
802 | DefaultOrigin -- Typechecking a default decl
803 | DoOrigin -- Arising from a do expression
804 | ProcOrigin -- Arising from a proc expression
805 | ImplicOrigin SDoc -- An implication constraint
807 instance Outputable InstOrigin where
808 ppr (OccurrenceOf name) = hsep [ptext SLIT("a use of"), quotes (ppr name)]
809 ppr (IPOccOrigin name) = hsep [ptext SLIT("a use of implicit parameter"), quotes (ppr name)]
810 ppr (IPBindOrigin name) = hsep [ptext SLIT("a binding for implicit parameter"), quotes (ppr name)]
811 ppr RecordUpdOrigin = ptext SLIT("a record update")
812 ppr (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
813 ppr (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
814 ppr (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
815 ppr InstSigOrigin = ptext SLIT("instantiating a type signature")
816 ppr InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
817 ppr DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
818 ppr StandAloneDerivOrigin = ptext SLIT("a 'deriving' declaration")
819 ppr DefaultOrigin = ptext SLIT("a 'default' declaration")
820 ppr DoOrigin = ptext SLIT("a do statement")
821 ppr ProcOrigin = ptext SLIT("a proc expression")
822 ppr (ImplicOrigin doc) = doc
823 ppr (SigOrigin info) = pprSkolInfo info