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
138 tcg_type_env :: TypeEnv, -- Global type env for the module we are compiling now
139 -- All TyCons and Classes (for this module) end up in here right away,
140 -- along with their derived constructors, selectors.
142 -- (Ids defined in this module start in the local envt,
143 -- though they move to the global envt during zonking)
145 tcg_type_env_var :: TcRef TypeEnv,
146 -- Used only to initialise the interface-file
147 -- typechecker in initIfaceTcRn, so that it can see stuff
148 -- bound in this module when dealing with hi-boot recursions
149 -- Updated at intervals (e.g. after dealing with types and classes)
151 tcg_inst_env :: InstEnv, -- Instance envt for *home-package*
152 -- modules; Includes the dfuns in
154 tcg_fam_inst_env :: FamInstEnv, -- Ditto for family instances
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 :: [AvailInfo], -- 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_imports :: Maybe [LImportDecl Name],
216 tcg_rn_exports :: Maybe [Located (IE Name)],
217 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
218 -- Nothing <=> Don't retain renamed decls
220 tcg_binds :: LHsBinds Id, -- Value bindings in this module
221 tcg_deprecs :: Deprecations, -- ...Deprecations
222 tcg_insts :: [Instance], -- ...Instances
223 tcg_fam_insts :: [FamInst], -- ...Family instances
224 tcg_rules :: [LRuleDecl Id], -- ...Rules
225 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
227 tcg_doc :: Maybe (HsDoc Name), -- Maybe Haddock documentation
228 tcg_hmi :: HaddockModInfo Name -- Haddock module information
232 %************************************************************************
234 The interface environments
235 Used when dealing with IfaceDecls
237 %************************************************************************
242 -- The type environment for the module being compiled,
243 -- in case the interface refers back to it via a reference that
244 -- was originally a hi-boot file.
245 -- We need the module name so we can test when it's appropriate
246 -- to look in this env.
247 if_rec_types :: Maybe (Module, IfG TypeEnv)
248 -- Allows a read effect, so it can be in a mutable
249 -- variable; c.f. handling the external package type env
250 -- Nothing => interactive stuff, no loops possible
255 -- The module for the current IfaceDecl
256 -- So if we see f = \x -> x
257 -- it means M.f = \x -> x, where M is the if_mod
260 -- The field is used only for error reporting
261 -- if (say) there's a Lint error in it
263 -- Where the interface came from:
264 -- .hi file, or GHCi state, or ext core
265 -- plus which bit is currently being examined
267 if_tv_env :: UniqFM TyVar, -- Nested tyvar bindings
268 if_id_env :: UniqFM Id -- Nested id binding
273 %************************************************************************
275 The local typechecker environment
277 %************************************************************************
279 The Global-Env/Local-Env story
280 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
281 During type checking, we keep in the tcg_type_env
282 * All types and classes
283 * All Ids derived from types and classes (constructors, selectors)
285 At the end of type checking, we zonk the local bindings,
286 and as we do so we add to the tcg_type_env
287 * Locally defined top-level Ids
289 Why? Because they are now Ids not TcIds. This final GlobalEnv is
290 a) fed back (via the knot) to typechecking the
291 unfoldings of interface signatures
292 b) used in the ModDetails of this module
295 data TcLclEnv -- Changes as we move inside an expression
296 -- Discarded after typecheck/rename; not passed on to desugarer
298 tcl_loc :: SrcSpan, -- Source span
299 tcl_ctxt :: ErrCtxt, -- Error context
300 tcl_errs :: TcRef Messages, -- Place to accumulate errors
302 tcl_th_ctxt :: ThStage, -- Template Haskell context
303 tcl_arrow_ctxt :: ArrowCtxt, -- Arrow-notation context
305 tcl_rdr :: LocalRdrEnv, -- Local name envt
306 -- Maintained during renaming, of course, but also during
307 -- type checking, solely so that when renaming a Template-Haskell
308 -- splice we have the right environment for the renamer.
310 -- Does *not* include global name envt; may shadow it
311 -- Includes both ordinary variables and type variables;
312 -- they are kept distinct because tyvar have a different
313 -- occurrence contructor (Name.TvOcc)
314 -- We still need the unsullied global name env so that
315 -- we can look up record field names
317 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
318 -- defined in this module
320 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
321 -- Namely, the in-scope TyVars bound in tcl_env,
322 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
323 -- Why mutable? see notes with tcGetGlobalTyVars
325 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
329 {- Note [Given Insts]
331 Because of GADTs, we have to pass inwards the Insts provided by type signatures
332 and existential contexts. Consider
333 data T a where { T1 :: b -> b -> T [b] }
334 f :: Eq a => T a -> Bool
335 f (T1 x y) = [x]==[y]
337 The constructor T1 binds an existential variable 'b', and we need Eq [b].
338 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
343 ---------------------------
344 -- Template Haskell levels
345 ---------------------------
348 -- Indicates how many levels of brackets we are inside
350 -- Incremented when going inside a bracket,
351 -- decremented when going inside a splice
352 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
353 -- original "Template meta-programmign for Haskell" paper
355 impLevel, topLevel :: ThLevel
356 topLevel = 1 -- Things defined at top level of this module
357 impLevel = 0 -- Imported things; they can be used inside a top level splice
361 -- g1 = $(map ...) is OK
362 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
366 = Comp -- Ordinary compiling, at level topLevel
367 | Splice ThLevel -- Inside a splice
368 | Brack ThLevel -- Inside brackets;
369 (TcRef [PendingSplice]) -- accumulate pending splices here
370 (TcRef LIE) -- and type constraints here
371 topStage, topSpliceStage :: ThStage
373 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
375 ---------------------------
376 -- Arrow-notation context
377 ---------------------------
380 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
381 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
386 Here, x is not in scope in e1, but it is in scope in e2. This can get
390 proc y -> (proc z -> e1) -< e2
392 Here, x and z are in scope in e1, but y is not. We implement this by
393 recording the environment when passing a proc (using newArrowScope),
394 and returning to that (using escapeArrowScope) on the left of -< and the
400 | ArrowCtxt (Env TcGblEnv TcLclEnv)
402 -- Record the current environment (outside a proc)
403 newArrowScope :: TcM a -> TcM a
406 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
408 -- Return to the stored environment (from the enclosing proc)
409 escapeArrowScope :: TcM a -> TcM a
411 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
413 ArrowCtxt env' -> env'
415 ---------------------------
417 ---------------------------
420 = AGlobal TyThing -- Used only in the return type of a lookup
422 | ATcId { -- Ids defined in this module; may not be fully zonked
424 tct_co :: Maybe HsWrapper, -- Nothing <=> Do not apply a GADT type refinement
425 -- I am wobbly, or have no free
427 -- Just co <=> Apply any type refinement to me,
428 -- and record it in the coercion
429 tct_type :: TcType, -- Type of (coercion applied to id)
430 tct_level :: ThLevel }
432 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
433 -- is currently refined. We only need the Name
434 -- for error-message purposes
436 | AThing TcKind -- Used temporarily, during kind checking, for the
437 -- tycons and clases in this recursive group
439 instance Outputable TcTyThing where -- Debugging only
440 ppr (AGlobal g) = ppr g
441 ppr elt@(ATcId {}) = text "Identifier" <>
442 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
443 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
444 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
445 ppr (AThing k) = text "AThing" <+> ppr k
447 pprTcTyThingCategory :: TcTyThing -> SDoc
448 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
449 pprTcTyThingCategory (ATyVar {}) = ptext SLIT("Type variable")
450 pprTcTyThingCategory (ATcId {}) = ptext SLIT("Local identifier")
451 pprTcTyThingCategory (AThing {}) = ptext SLIT("Kinded thing")
455 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
456 -- Innermost first. Monadic so that we have a chance
457 -- to deal with bound type variables just before error
458 -- message construction
462 %************************************************************************
464 Operations over ImportAvails
466 %************************************************************************
468 ImportAvails summarises what was imported from where, irrespective
469 of whether the imported things are actually used or not
470 It is used * when processing the export list
471 * when constructing usage info for the inteface file
472 * to identify the list of directly imported modules
473 for initialisation purposes and
474 for optimsed overlap checking of family instances
475 * when figuring out what things are really unused
480 imp_mods :: ModuleEnv (Module, Bool, SrcSpan),
481 -- Domain is all directly-imported modules
483 -- True => import was "import Foo ()"
484 -- False => import was some other form
486 -- We need the Module in the range because we can't get
487 -- the keys of a ModuleEnv
489 -- (a) to help construct the usage information in
490 -- the interface file; if we import somethign we
491 -- need to recompile if the export version changes
492 -- (b) to specify what child modules to initialise
494 -- We need a full ModuleEnv rather than a ModuleNameEnv
495 -- here, because we might be importing modules of the
496 -- same name from different packages. (currently not the case,
497 -- but might be in the future).
499 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
500 -- Home-package modules needed by the module being compiled
502 -- It doesn't matter whether any of these dependencies
503 -- are actually *used* when compiling the module; they
504 -- are listed if they are below it at all. For
505 -- example, suppose M imports A which imports X. Then
506 -- compiling M might not need to consult X.hi, but X
507 -- is still listed in M's dependencies.
509 imp_dep_pkgs :: [PackageId],
510 -- Packages needed by the module being compiled, whether
511 -- directly, or via other modules in this package, or via
512 -- modules imported from other packages.
514 imp_orphs :: [Module],
515 -- Orphan modules below us in the import tree (and maybe
516 -- including us for imported modules)
518 imp_finsts :: [Module]
519 -- Family instance modules below us in the import tree (and
520 -- maybe including us for imported modules)
523 mkModDeps :: [(ModuleName, IsBootInterface)]
524 -> ModuleNameEnv (ModuleName, IsBootInterface)
525 mkModDeps deps = foldl add emptyUFM deps
527 add env elt@(m,_) = addToUFM env m elt
529 emptyImportAvails :: ImportAvails
530 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
531 imp_dep_mods = emptyUFM,
536 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
538 (ImportAvails { imp_mods = mods1,
539 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
540 imp_orphs = orphs1, imp_finsts = finsts1 })
541 (ImportAvails { imp_mods = mods2,
542 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
543 imp_orphs = orphs2, imp_finsts = finsts2 })
544 = ImportAvails { imp_mods = mods1 `plusModuleEnv` mods2,
545 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
546 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
547 imp_orphs = orphs1 `unionLists` orphs2,
548 imp_finsts = finsts1 `unionLists` finsts2 }
550 plus_mod_dep (m1, boot1) (m2, boot2)
551 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
552 -- Check mod-names match
553 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
556 %************************************************************************
558 \subsection{Where from}
560 %************************************************************************
562 The @WhereFrom@ type controls where the renamer looks for an interface file
566 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
567 | ImportBySystem -- Non user import.
569 instance Outputable WhereFrom where
570 ppr (ImportByUser is_boot) | is_boot = ptext SLIT("{- SOURCE -}")
572 ppr ImportBySystem = ptext SLIT("{- SYSTEM -}")
576 %************************************************************************
578 \subsection[Inst-types]{@Inst@ types}
580 v%************************************************************************
582 An @Inst@ is either a dictionary, an instance of an overloaded
583 literal, or an instance of an overloaded value. We call the latter a
584 ``method'' even though it may not correspond to a class operation.
585 For example, we might have an instance of the @double@ function at
586 type Int, represented by
588 Method 34 doubleId [Int] origin
594 tci_pred :: TcPredType,
598 | ImplicInst { -- An implication constraint
599 -- forall tvs. (reft, given) => wanted
601 tci_tyvars :: [TcTyVar], -- Includes coercion variables
602 -- mentioned in tci_reft
603 tci_reft :: Refinement,
604 tci_given :: [Inst], -- Only Dicts
605 -- (no Methods, LitInsts, ImplicInsts)
606 tci_wanted :: [Inst], -- Only Dicts and ImplicInsts
607 -- (no Methods or LitInsts)
612 tci_id :: TcId, -- The Id for the Inst
614 tci_oid :: TcId, -- The overloaded function
615 -- This function will be a global, local, or ClassOpId;
616 -- inside instance decls (only) it can also be an InstId!
617 -- The id needn't be completely polymorphic.
618 -- You'll probably find its name (for documentation purposes)
619 -- inside the InstOrigin
621 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
622 -- should be instantiated.
623 -- These types must saturate the Id's foralls.
625 tci_theta :: TcThetaType,
626 -- The (types of the) dictionaries to which the function
627 -- must be applied to get the method
631 -- INVARIANT 1: in (Method m f tys theta tau loc)
632 -- type of m = type of (f tys dicts(from theta))
634 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
635 -- Reason: two methods are considered equal if the
636 -- base Id matches, and the instantiating types
637 -- match. The TcThetaType should then match too.
638 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
642 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
643 -- INVARIANT: never a rebindable-syntax literal
644 -- Reason: tcSyntaxName does unification, and we
645 -- don't want to deal with that during tcSimplify,
646 -- when resolving LitInsts
648 tci_ty :: TcType, -- The type at which the literal is used
653 @Insts@ are ordered by their class/type info, rather than by their
654 unique. This allows the context-reduction mechanism to use standard finite
655 maps to do their stuff. It's horrible that this code is here, rather
656 than with the Avails handling stuff in TcSimplify
659 instance Ord Inst where
662 instance Eq Inst where
663 (==) i1 i2 = case i1 `cmpInst` i2 of
667 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
668 cmpInst (Dict {}) other = LT
670 cmpInst (Method {}) (Dict {}) = GT
671 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
672 (tci_tys m1 `tcCmpTypes` tci_tys m2)
673 cmpInst (Method {}) other = LT
675 cmpInst (LitInst {}) (Dict {}) = GT
676 cmpInst (LitInst {}) (Method {}) = GT
677 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
678 (tci_ty l1 `tcCmpType` tci_ty l2)
679 cmpInst (LitInst {}) other = LT
681 -- Implication constraints are compared by *name*
682 -- not by type; that is, we make no attempt to do CSE on them
683 cmpInst (ImplicInst {}) (Dict {}) = GT
684 cmpInst (ImplicInst {}) (Method {}) = GT
685 cmpInst (ImplicInst {}) (LitInst {}) = GT
686 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
690 %************************************************************************
692 \subsection[Inst-collections]{LIE: a collection of Insts}
694 %************************************************************************
697 -- FIXME: Rename this. It clashes with (Located (IE ...))
700 isEmptyLIE = isEmptyBag
702 unitLIE inst = unitBag inst
703 mkLIE insts = listToBag insts
704 plusLIE lie1 lie2 = lie1 `unionBags` lie2
705 plusLIEs lies = unionManyBags lies
706 lieToList = bagToList
707 listToLIE = listToBag
709 consLIE inst lie = lie `snocBag` inst
710 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
711 -- to ensure that we tend to report the *leftmost* type-constraint error
714 -- we'd like to complain about the '1', not the '3'.
716 -- "Half-hearted" because the rest of the type checker makes no great
717 -- claims for retaining order in the constraint set. Still, this
718 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
722 %************************************************************************
724 \subsection[Inst-origin]{The @InstOrigin@ type}
726 %************************************************************************
728 The @InstOrigin@ type gives information about where a dictionary came from.
729 This is important for decent error message reporting because dictionaries
730 don't appear in the original source code. Doubtless this type will evolve...
732 It appears in TcMonad because there are a couple of error-message-generation
733 functions that deal with it.
736 -------------------------------------------
737 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
739 instLoc :: Inst -> InstLoc
740 instLoc inst = tci_loc inst
742 instSpan :: Inst -> SrcSpan
743 instSpan wanted = instLocSpan (instLoc wanted)
745 instLocSpan :: InstLoc -> SrcSpan
746 instLocSpan (InstLoc _ s _) = s
748 instLocOrigin :: InstLoc -> InstOrigin
749 instLocOrigin (InstLoc o _ _) = o
751 pprInstArising :: Inst -> SDoc
752 pprInstArising loc = ptext SLIT("arising from") <+> pprInstLoc (tci_loc loc)
754 pprInstLoc :: InstLoc -> SDoc
755 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
757 -------------------------------------------
759 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
760 -- Places that bind type variables and introduce
761 -- available constraints
763 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
765 -------------------------------------------------------
766 -- The rest are all occurrences: Insts that are 'wanted'
767 -------------------------------------------------------
768 | OccurrenceOf Name -- Occurrence of an overloaded identifier
770 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
772 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
774 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
775 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
777 | InstSigOrigin -- A dict occurrence arising from instantiating
778 -- a polymorphic type during a subsumption check
781 | InstScOrigin -- Typechecking superclasses of an instance declaration
782 | DerivOrigin -- Typechecking deriving
783 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
784 | DefaultOrigin -- Typechecking a default decl
785 | DoOrigin -- Arising from a do expression
786 | ProcOrigin -- Arising from a proc expression
787 | ImplicOrigin SDoc -- An implication constraint
789 instance Outputable InstOrigin where
790 ppr (OccurrenceOf name) = hsep [ptext SLIT("a use of"), quotes (ppr name)]
791 ppr (IPOccOrigin name) = hsep [ptext SLIT("a use of implicit parameter"), quotes (ppr name)]
792 ppr (IPBindOrigin name) = hsep [ptext SLIT("a binding for implicit parameter"), quotes (ppr name)]
793 ppr RecordUpdOrigin = ptext SLIT("a record update")
794 ppr (LiteralOrigin lit) = hsep [ptext SLIT("the literal"), quotes (ppr lit)]
795 ppr (ArithSeqOrigin seq) = hsep [ptext SLIT("the arithmetic sequence"), quotes (ppr seq)]
796 ppr (PArrSeqOrigin seq) = hsep [ptext SLIT("the parallel array sequence"), quotes (ppr seq)]
797 ppr InstSigOrigin = ptext SLIT("instantiating a type signature")
798 ppr InstScOrigin = ptext SLIT("the superclasses of an instance declaration")
799 ppr DerivOrigin = ptext SLIT("the 'deriving' clause of a data type declaration")
800 ppr StandAloneDerivOrigin = ptext SLIT("a 'deriving' declaration")
801 ppr DefaultOrigin = ptext SLIT("a 'default' declaration")
802 ppr DoOrigin = ptext SLIT("a do statement")
803 ppr ProcOrigin = ptext SLIT("a proc expression")
804 ppr (ImplicOrigin doc) = doc
805 ppr (SigOrigin info) = pprSkolInfo info