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, RefinementVisibility(..),
24 ThStage(..), topStage, topSpliceStage,
25 ThLevel, impLevel, topLevel,
28 ArrowCtxt(NoArrowCtxt), newArrowScope, escapeArrowScope,
31 Inst(..), EqInstCo, 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,
41 #include "HsVersions.h"
43 import HsSyn hiding (LIE)
75 %************************************************************************
77 Standard monad definition for TcRn
78 All the combinators for the monad can be found in TcRnMonad
80 %************************************************************************
82 The monad itself has to be defined here, because it is mentioned by ErrCtxt
85 type TcRef a = IORef a
86 type TcId = Id -- Type may be a TcType
88 type TcDictBinds = DictBinds TcId -- Bag of dictionary bindings
90 type TcRnIf a b c = IOEnv (Env a b) c
91 type IfM lcl a = TcRnIf IfGblEnv lcl a -- Iface stuff
93 type IfG a = IfM () a -- Top level
94 type IfL a = IfM IfLclEnv a -- Nested
95 type TcRn a = TcRnIf TcGblEnv TcLclEnv a
96 type RnM a = TcRn a -- Historical
97 type TcM a = TcRn a -- Historical
101 %************************************************************************
103 The main environment types
105 %************************************************************************
108 data Env gbl lcl -- Changes as we move into an expression
110 env_top :: HscEnv, -- Top-level stuff that never changes
111 -- Includes all info about imported things
113 env_us :: {-# UNPACK #-} !(IORef UniqSupply),
114 -- Unique supply for local varibles
116 env_gbl :: gbl, -- Info about things defined at the top level
117 -- of the module being compiled
119 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 tcg_rn_imports :: Maybe [LImportDecl Name],
212 tcg_rn_exports :: Maybe [Located (IE Name)],
213 tcg_rn_decls :: Maybe (HsGroup Name), -- renamed decls, maybe
214 -- Nothing <=> Don't retain renamed decls
216 tcg_binds :: LHsBinds Id, -- Value bindings in this module
217 tcg_warns :: Warnings, -- ...Warnings and deprecations
218 tcg_insts :: [Instance], -- ...Instances
219 tcg_fam_insts :: [FamInst], -- ...Family instances
220 tcg_rules :: [LRuleDecl Id], -- ...Rules
221 tcg_fords :: [LForeignDecl Id], -- ...Foreign import & exports
223 tcg_doc :: Maybe (HsDoc Name), -- Maybe Haddock documentation
224 tcg_hmi :: HaddockModInfo Name, -- Haddock module information
225 tcg_hpc :: AnyHpcUsage -- True if any part of the prog uses hpc instrumentation.
228 type RecFieldEnv = NameEnv [Name] -- Maps a constructor name *in this module*
229 -- to the fields for that constructor
230 -- This is used when dealing with ".." notation in record
231 -- construction and pattern matching.
232 -- The FieldEnv deals *only* with constructors defined in *thie*
233 -- module. For imported modules, we get the same info from the
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-programming 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 :: RefinementVisibility, -- Previously: Maybe HsWrapper
430 -- Nothing <=> Do not apply a GADT type refinement
431 -- I am wobbly, or have no free
433 -- Just co <=> Apply any type refinement to me,
434 -- and record it in the coercion
435 tct_type :: TcType, -- Type of (coercion applied to id)
436 tct_level :: ThLevel }
438 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
439 -- is currently refined. We only need the Name
440 -- for error-message purposes
442 | AThing TcKind -- Used temporarily, during kind checking, for the
443 -- tycons and clases in this recursive group
445 data RefinementVisibility
446 = Unrefineable -- Do not apply a GADT refinement
447 -- I have no free variables
449 | Rigid HsWrapper -- Apply any refinement to me
450 -- and record it in the coercion
452 | Wobbly -- Do not apply a GADT refinement
455 | WobblyInvisible -- Wobbly type, not available inside current
458 instance Outputable TcTyThing where -- Debugging only
459 ppr (AGlobal g) = pprTyThing g
460 ppr elt@(ATcId {}) = text "Identifier" <>
461 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
462 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
463 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
464 ppr (AThing k) = text "AThing" <+> ppr k
466 pprTcTyThingCategory :: TcTyThing -> SDoc
467 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
468 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
469 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
470 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
472 instance Outputable RefinementVisibility where
473 ppr Unrefineable = ptext (sLit "unrefineable")
474 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
475 ppr Wobbly = ptext (sLit "wobbly")
476 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
481 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
482 -- Innermost first. Monadic so that we have a chance
483 -- to deal with bound type variables just before error
484 -- message construction
488 %************************************************************************
490 Operations over ImportAvails
492 %************************************************************************
494 ImportAvails summarises what was imported from where, irrespective
495 of whether the imported things are actually used or not
496 It is used * when processing the export list
497 * when constructing usage info for the inteface file
498 * to identify the list of directly imported modules
499 for initialisation purposes and
500 for optimsed overlap checking of family instances
501 * when figuring out what things are really unused
506 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
507 -- Domain is all directly-imported modules
508 -- The ModuleName is what the module was imported as, e.g. in
512 -- True => import was "import Foo ()"
513 -- False => import was some other form
516 -- (a) to help construct the usage information in
517 -- the interface file; if we import somethign we
518 -- need to recompile if the export version changes
519 -- (b) to specify what child modules to initialise
521 -- We need a full ModuleEnv rather than a ModuleNameEnv
522 -- here, because we might be importing modules of the
523 -- same name from different packages. (currently not the case,
524 -- but might be in the future).
526 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
527 -- Home-package modules needed by the module being compiled
529 -- It doesn't matter whether any of these dependencies
530 -- are actually *used* when compiling the module; they
531 -- are listed if they are below it at all. For
532 -- example, suppose M imports A which imports X. Then
533 -- compiling M might not need to consult X.hi, but X
534 -- is still listed in M's dependencies.
536 imp_dep_pkgs :: [PackageId],
537 -- Packages needed by the module being compiled, whether
538 -- directly, or via other modules in this package, or via
539 -- modules imported from other packages.
541 imp_orphs :: [Module],
542 -- Orphan modules below us in the import tree (and maybe
543 -- including us for imported modules)
545 imp_finsts :: [Module]
546 -- Family instance modules below us in the import tree (and
547 -- maybe including us for imported modules)
550 mkModDeps :: [(ModuleName, IsBootInterface)]
551 -> ModuleNameEnv (ModuleName, IsBootInterface)
552 mkModDeps deps = foldl add emptyUFM deps
554 add env elt@(m,_) = addToUFM env m elt
556 emptyImportAvails :: ImportAvails
557 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
558 imp_dep_mods = emptyUFM,
563 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
565 (ImportAvails { imp_mods = mods1,
566 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
567 imp_orphs = orphs1, imp_finsts = finsts1 })
568 (ImportAvails { imp_mods = mods2,
569 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
570 imp_orphs = orphs2, imp_finsts = finsts2 })
571 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
572 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
573 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
574 imp_orphs = orphs1 `unionLists` orphs2,
575 imp_finsts = finsts1 `unionLists` finsts2 }
577 plus_mod_dep (m1, boot1) (m2, boot2)
578 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
579 -- Check mod-names match
580 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
583 %************************************************************************
585 \subsection{Where from}
587 %************************************************************************
589 The @WhereFrom@ type controls where the renamer looks for an interface file
593 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
594 | ImportBySystem -- Non user import.
596 instance Outputable WhereFrom where
597 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
599 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
603 %************************************************************************
605 \subsection[Inst-types]{@Inst@ types}
607 v%************************************************************************
609 An @Inst@ is either a dictionary, an instance of an overloaded
610 literal, or an instance of an overloaded value. We call the latter a
611 ``method'' even though it may not correspond to a class operation.
612 For example, we might have an instance of the @double@ function at
613 type Int, represented by
615 Method 34 doubleId [Int] origin
617 In addition to the basic Haskell variants of 'Inst's, they can now also
618 represent implication constraints 'forall tvs. given => wanted'
619 and equality constraints 'co :: ty1 ~ ty2'.
621 NB: Equalities occur in two flavours:
623 (1) Dict {tci_pred = EqPred ty1 ty2}
624 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
626 The former arises from equalities in contexts, whereas the latter is used
627 whenever the type checker introduces an equality (e.g., during deferring
630 I am not convinced that this duplication is necessary or useful! -=chak
636 tci_pred :: TcPredType, -- Class or implicit parameter only
640 | ImplicInst { -- An implication constraint
641 -- forall tvs. given => wanted
643 tci_tyvars :: [TcTyVar], -- Quantified type variables
644 tci_given :: [Inst], -- Only Dicts and EqInsts
645 -- (no Methods, LitInsts, ImplicInsts)
646 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
647 -- (no Methods or LitInsts)
651 -- NB: the tci_given are not necessarily rigid
654 tci_id :: TcId, -- The Id for the Inst
656 tci_oid :: TcId, -- The overloaded function
657 -- This function will be a global, local, or ClassOpId;
658 -- inside instance decls (only) it can also be an InstId!
659 -- The id needn't be completely polymorphic.
660 -- You'll probably find its name (for documentation purposes)
661 -- inside the InstOrigin
663 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
664 -- should be instantiated.
665 -- These types must saturate the Id's foralls.
667 tci_theta :: TcThetaType,
668 -- The (types of the) dictionaries to which the function
669 -- must be applied to get the method
673 -- INVARIANT 1: in (Method m f tys theta tau loc)
674 -- type of m = type of (f tys dicts(from theta))
676 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
677 -- Reason: two methods are considered equal if the
678 -- base Id matches, and the instantiating types
679 -- match. The TcThetaType should then match too.
680 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
684 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
685 -- INVARIANT: never a rebindable-syntax literal
686 -- Reason: tcSyntaxName does unification, and we
687 -- don't want to deal with that during tcSimplify,
688 -- when resolving LitInsts
690 tci_ty :: TcType, -- The type at which the literal is used
694 | EqInst { -- delayed unification of the form
696 tci_left :: TcType, -- ty1 -- both types are...
697 tci_right :: TcType, -- ty2 -- ...free of boxes
698 tci_co :: EqInstCo, -- co
701 tci_name :: Name -- Debugging help only: this makes it easier to
702 -- follow where a constraint is used in a morass
703 -- of trace messages! Unlike other Insts, it
704 -- has no semantic significance whatsoever.
707 type EqInstCo = Either -- Distinguish between given and wanted coercions
708 TcTyVar -- - a wanted equation, with a hole, to be filled
709 -- with a witness for the equality; for equation
710 -- arising from deferring unification, 'ty1' is
711 -- the actual and 'ty2' the expected type
712 Coercion -- - a given equation, with a coercion witnessing
713 -- the equality; a coercion that originates
714 -- from a signature or a GADT is a CoVar, but
715 -- after normalisation of coercions, they can
716 -- be arbitrary Coercions involving constructors
717 -- and pseudo-constructors like sym and trans.
720 @Insts@ are ordered by their class/type info, rather than by their
721 unique. This allows the context-reduction mechanism to use standard finite
722 maps to do their stuff. It's horrible that this code is here, rather
723 than with the Avails handling stuff in TcSimplify
726 instance Ord Inst where
728 -- Used *only* for AvailEnv in TcSimplify
730 instance Eq Inst where
731 (==) i1 i2 = case i1 `cmpInst` i2 of
735 cmpInst :: Inst -> Inst -> Ordering
736 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
737 cmpInst (Dict {}) _ = LT
739 cmpInst (Method {}) (Dict {}) = GT
740 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
741 (tci_tys m1 `tcCmpTypes` tci_tys m2)
742 cmpInst (Method {}) _ = LT
744 cmpInst (LitInst {}) (Dict {}) = GT
745 cmpInst (LitInst {}) (Method {}) = GT
746 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
747 (tci_ty l1 `tcCmpType` tci_ty l2)
748 cmpInst (LitInst {}) _ = LT
750 -- Implication constraints are compared by *name*
751 -- not by type; that is, we make no attempt to do CSE on them
752 cmpInst (ImplicInst {}) (Dict {}) = GT
753 cmpInst (ImplicInst {}) (Method {}) = GT
754 cmpInst (ImplicInst {}) (LitInst {}) = GT
755 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
756 cmpInst (ImplicInst {}) _ = LT
758 -- same for Equality constraints
759 cmpInst (EqInst {}) (Dict {}) = GT
760 cmpInst (EqInst {}) (Method {}) = GT
761 cmpInst (EqInst {}) (LitInst {}) = GT
762 cmpInst (EqInst {}) (ImplicInst {}) = GT
763 cmpInst i1@(EqInst {}) i2@(EqInst {}) = (tci_left i1 `tcCmpType` tci_left i2) `thenCmp`
764 (tci_right i1 `tcCmpType` tci_right i2)
768 %************************************************************************
770 \subsection[Inst-collections]{LIE: a collection of Insts}
772 %************************************************************************
775 -- FIXME: Rename this. It clashes with (Located (IE ...))
778 isEmptyLIE :: LIE -> Bool
779 isEmptyLIE = isEmptyBag
784 unitLIE :: Inst -> LIE
785 unitLIE inst = unitBag inst
787 mkLIE :: [Inst] -> LIE
788 mkLIE insts = listToBag insts
790 plusLIE :: LIE -> LIE -> LIE
791 plusLIE lie1 lie2 = lie1 `unionBags` lie2
793 plusLIEs :: [LIE] -> LIE
794 plusLIEs lies = unionManyBags lies
796 lieToList :: LIE -> [Inst]
797 lieToList = bagToList
799 listToLIE :: [Inst] -> LIE
800 listToLIE = listToBag
802 consLIE :: Inst -> LIE -> LIE
803 consLIE inst lie = lie `snocBag` inst
804 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
805 -- to ensure that we tend to report the *leftmost* type-constraint error
808 -- we'd like to complain about the '1', not the '3'.
810 -- "Half-hearted" because the rest of the type checker makes no great
811 -- claims for retaining order in the constraint set. Still, this
812 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
816 %************************************************************************
818 \subsection[Inst-origin]{The @InstOrigin@ type}
820 %************************************************************************
822 The @InstOrigin@ type gives information about where a dictionary came from.
823 This is important for decent error message reporting because dictionaries
824 don't appear in the original source code. Doubtless this type will evolve...
826 It appears in TcMonad because there are a couple of error-message-generation
827 functions that deal with it.
830 -------------------------------------------
831 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
833 instLoc :: Inst -> InstLoc
834 instLoc inst = tci_loc inst
836 instSpan :: Inst -> SrcSpan
837 instSpan wanted = instLocSpan (instLoc wanted)
839 instLocSpan :: InstLoc -> SrcSpan
840 instLocSpan (InstLoc _ s _) = s
842 instLocOrigin :: InstLoc -> InstOrigin
843 instLocOrigin (InstLoc o _ _) = o
845 pprInstArising :: Inst -> SDoc
846 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
848 pprInstLoc :: InstLoc -> SDoc
849 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
851 -------------------------------------------
853 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
854 -- Places that bind type variables and introduce
855 -- available constraints
857 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
859 -------------------------------------------------------
860 -- The rest are all occurrences: Insts that are 'wanted'
861 -------------------------------------------------------
862 | OccurrenceOf Name -- Occurrence of an overloaded identifier
863 | SpecPragOrigin Name -- Specialisation pragma for identifier
865 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
867 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
868 | NegateOrigin -- Occurrence of syntactic negation
870 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
871 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
872 | TupleOrigin -- (..,..)
874 | InstSigOrigin -- A dict occurrence arising from instantiating
875 -- a polymorphic type during a subsumption check
877 | ExprSigOrigin -- e :: ty
880 | InstScOrigin -- Typechecking superclasses of an instance declaration
881 | DerivOrigin -- Typechecking deriving
882 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
883 | DefaultOrigin -- Typechecking a default decl
884 | DoOrigin -- Arising from a do expression
885 | ProcOrigin -- Arising from a proc expression
886 | ImplicOrigin SDoc -- An implication constraint
887 | EqOrigin -- A type equality
889 instance Outputable InstOrigin where
890 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
891 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
892 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
893 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
894 ppr RecordUpdOrigin = ptext (sLit "a record update")
895 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
896 ppr ViewPatOrigin = ptext (sLit "a view pattern")
897 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
898 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
899 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
900 ppr TupleOrigin = ptext (sLit "a tuple")
901 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
902 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
903 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
904 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
905 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
906 ppr DoOrigin = ptext (sLit "a do statement")
907 ppr ProcOrigin = ptext (sLit "a proc expression")
908 ppr (ImplicOrigin doc) = doc
909 ppr (SigOrigin info) = pprSkolInfo info
910 ppr EqOrigin = ptext (sLit "a type equality")
911 ppr InstSigOrigin = panic "ppr InstSigOrigin"