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(..), 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 -- 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 -- Does *not* include global name envt; may shadow it
321 -- Includes both ordinary variables and type variables;
322 -- they are kept distinct because tyvar have a different
323 -- occurrence contructor (Name.TvOcc)
324 -- We still need the unsullied global name env so that
325 -- we can look up record field names
327 tcl_env :: NameEnv TcTyThing, -- The local type environment: Ids and TyVars
328 -- defined in this module
330 tcl_tyvars :: TcRef TcTyVarSet, -- The "global tyvars"
331 -- Namely, the in-scope TyVars bound in tcl_env,
332 -- plus the tyvars mentioned in the types of Ids bound in tcl_lenv
333 -- Why mutable? see notes with tcGetGlobalTyVars
335 tcl_lie :: TcRef LIE -- Place to accumulate type constraints
339 {- Note [Given Insts]
341 Because of GADTs, we have to pass inwards the Insts provided by type signatures
342 and existential contexts. Consider
343 data T a where { T1 :: b -> b -> T [b] }
344 f :: Eq a => T a -> Bool
345 f (T1 x y) = [x]==[y]
347 The constructor T1 binds an existential variable 'b', and we need Eq [b].
348 Well, we have it, because Eq a refines to Eq [b], but we can only spot that if we
353 ---------------------------
354 -- Template Haskell levels
355 ---------------------------
358 -- Indicates how many levels of brackets we are inside
360 -- Incremented when going inside a bracket,
361 -- decremented when going inside a splice
362 -- NB: ThLevel is one greater than the 'n' in Fig 2 of the
363 -- original "Template meta-programming for Haskell" paper
365 impLevel, topLevel :: ThLevel
366 topLevel = 1 -- Things defined at top level of this module
367 impLevel = 0 -- Imported things; they can be used inside a top level splice
371 -- g1 = $(map ...) is OK
372 -- g2 = $(f ...) is not OK; because we havn't compiled f yet
376 = Comp -- Ordinary compiling, at level topLevel
377 | Splice ThLevel -- Inside a splice
378 | Brack ThLevel -- Inside brackets;
379 (TcRef [PendingSplice]) -- accumulate pending splices here
380 (TcRef LIE) -- and type constraints here
381 topStage, topSpliceStage :: ThStage
383 topSpliceStage = Splice (topLevel - 1) -- Stage for the body of a top-level splice
385 ---------------------------
386 -- Arrow-notation context
387 ---------------------------
390 In arrow notation, a variable bound by a proc (or enclosed let/kappa)
391 is not in scope to the left of an arrow tail (-<) or the head of (|..|).
396 Here, x is not in scope in e1, but it is in scope in e2. This can get
400 proc y -> (proc z -> e1) -< e2
402 Here, x and z are in scope in e1, but y is not. We implement this by
403 recording the environment when passing a proc (using newArrowScope),
404 and returning to that (using escapeArrowScope) on the left of -< and the
410 | ArrowCtxt (Env TcGblEnv TcLclEnv)
412 -- Record the current environment (outside a proc)
413 newArrowScope :: TcM a -> TcM a
416 env { env_lcl = (env_lcl env) { tcl_arrow_ctxt = ArrowCtxt env } }
418 -- Return to the stored environment (from the enclosing proc)
419 escapeArrowScope :: TcM a -> TcM a
421 = updEnv $ \ env -> case tcl_arrow_ctxt (env_lcl env) of
423 ArrowCtxt env' -> env'
425 ---------------------------
427 ---------------------------
430 = AGlobal TyThing -- Used only in the return type of a lookup
432 | ATcId { -- Ids defined in this module; may not be fully zonked
434 tct_co :: RefinementVisibility, -- Previously: Maybe HsWrapper
435 -- Nothing <=> Do not apply a GADT type refinement
436 -- I am wobbly, or have no free
438 -- Just co <=> Apply any type refinement to me,
439 -- and record it in the coercion
440 tct_type :: TcType, -- Type of (coercion applied to id)
441 tct_level :: ThLevel }
443 | ATyVar Name TcType -- The type to which the lexically scoped type vaiable
444 -- is currently refined. We only need the Name
445 -- for error-message purposes
447 | AThing TcKind -- Used temporarily, during kind checking, for the
448 -- tycons and clases in this recursive group
450 data RefinementVisibility
451 = Unrefineable -- Do not apply a GADT refinement
452 -- I have no free variables
454 | Rigid HsWrapper -- Apply any refinement to me
455 -- and record it in the coercion
457 | Wobbly -- Do not apply a GADT refinement
460 | WobblyInvisible -- Wobbly type, not available inside current
463 instance Outputable TcTyThing where -- Debugging only
464 ppr (AGlobal g) = pprTyThing g
465 ppr elt@(ATcId {}) = text "Identifier" <>
466 ifPprDebug (brackets (ppr (tct_id elt) <> dcolon <> ppr (tct_type elt) <> comma
467 <+> ppr (tct_level elt) <+> ppr (tct_co elt)))
468 ppr (ATyVar tv _) = text "Type variable" <+> quotes (ppr tv)
469 ppr (AThing k) = text "AThing" <+> ppr k
471 pprTcTyThingCategory :: TcTyThing -> SDoc
472 pprTcTyThingCategory (AGlobal thing) = pprTyThingCategory thing
473 pprTcTyThingCategory (ATyVar {}) = ptext (sLit "Type variable")
474 pprTcTyThingCategory (ATcId {}) = ptext (sLit "Local identifier")
475 pprTcTyThingCategory (AThing {}) = ptext (sLit "Kinded thing")
477 instance Outputable RefinementVisibility where
478 ppr Unrefineable = ptext (sLit "unrefineable")
479 ppr (Rigid co) = ptext (sLit "rigid") <+> ppr co
480 ppr Wobbly = ptext (sLit "wobbly")
481 ppr WobblyInvisible = ptext (sLit "wobbly-invisible")
486 type ErrCtxt = [TidyEnv -> TcM (TidyEnv, Message)]
487 -- Innermost first. Monadic so that we have a chance
488 -- to deal with bound type variables just before error
489 -- message construction
493 %************************************************************************
495 Operations over ImportAvails
497 %************************************************************************
499 ImportAvails summarises what was imported from where, irrespective
500 of whether the imported things are actually used or not
501 It is used * when processing the export list
502 * when constructing usage info for the inteface file
503 * to identify the list of directly imported modules
504 for initialisation purposes and
505 for optimsed overlap checking of family instances
506 * when figuring out what things are really unused
511 imp_mods :: ModuleEnv [(ModuleName, Bool, SrcSpan)],
512 -- Domain is all directly-imported modules
513 -- The ModuleName is what the module was imported as, e.g. in
517 -- True => import was "import Foo ()"
518 -- False => import was some other form
521 -- (a) to help construct the usage information in
522 -- the interface file; if we import somethign we
523 -- need to recompile if the export version changes
524 -- (b) to specify what child modules to initialise
526 -- We need a full ModuleEnv rather than a ModuleNameEnv
527 -- here, because we might be importing modules of the
528 -- same name from different packages. (currently not the case,
529 -- but might be in the future).
531 imp_dep_mods :: ModuleNameEnv (ModuleName, IsBootInterface),
532 -- Home-package modules needed by the module being compiled
534 -- It doesn't matter whether any of these dependencies
535 -- are actually *used* when compiling the module; they
536 -- are listed if they are below it at all. For
537 -- example, suppose M imports A which imports X. Then
538 -- compiling M might not need to consult X.hi, but X
539 -- is still listed in M's dependencies.
541 imp_dep_pkgs :: [PackageId],
542 -- Packages needed by the module being compiled, whether
543 -- directly, or via other modules in this package, or via
544 -- modules imported from other packages.
546 imp_orphs :: [Module],
547 -- Orphan modules below us in the import tree (and maybe
548 -- including us for imported modules)
550 imp_finsts :: [Module]
551 -- Family instance modules below us in the import tree (and
552 -- maybe including us for imported modules)
555 mkModDeps :: [(ModuleName, IsBootInterface)]
556 -> ModuleNameEnv (ModuleName, IsBootInterface)
557 mkModDeps deps = foldl add emptyUFM deps
559 add env elt@(m,_) = addToUFM env m elt
561 emptyImportAvails :: ImportAvails
562 emptyImportAvails = ImportAvails { imp_mods = emptyModuleEnv,
563 imp_dep_mods = emptyUFM,
568 plusImportAvails :: ImportAvails -> ImportAvails -> ImportAvails
570 (ImportAvails { imp_mods = mods1,
571 imp_dep_mods = dmods1, imp_dep_pkgs = dpkgs1,
572 imp_orphs = orphs1, imp_finsts = finsts1 })
573 (ImportAvails { imp_mods = mods2,
574 imp_dep_mods = dmods2, imp_dep_pkgs = dpkgs2,
575 imp_orphs = orphs2, imp_finsts = finsts2 })
576 = ImportAvails { imp_mods = plusModuleEnv_C (++) mods1 mods2,
577 imp_dep_mods = plusUFM_C plus_mod_dep dmods1 dmods2,
578 imp_dep_pkgs = dpkgs1 `unionLists` dpkgs2,
579 imp_orphs = orphs1 `unionLists` orphs2,
580 imp_finsts = finsts1 `unionLists` finsts2 }
582 plus_mod_dep (m1, boot1) (m2, boot2)
583 = WARN( not (m1 == m2), (ppr m1 <+> ppr m2) $$ (ppr boot1 <+> ppr boot2) )
584 -- Check mod-names match
585 (m1, boot1 && boot2) -- If either side can "see" a non-hi-boot interface, use that
588 %************************************************************************
590 \subsection{Where from}
592 %************************************************************************
594 The @WhereFrom@ type controls where the renamer looks for an interface file
598 = ImportByUser IsBootInterface -- Ordinary user import (perhaps {-# SOURCE #-})
599 | ImportBySystem -- Non user import.
601 instance Outputable WhereFrom where
602 ppr (ImportByUser is_boot) | is_boot = ptext (sLit "{- SOURCE -}")
604 ppr ImportBySystem = ptext (sLit "{- SYSTEM -}")
608 %************************************************************************
610 \subsection[Inst-types]{@Inst@ types}
612 v%************************************************************************
614 An @Inst@ is either a dictionary, an instance of an overloaded
615 literal, or an instance of an overloaded value. We call the latter a
616 ``method'' even though it may not correspond to a class operation.
617 For example, we might have an instance of the @double@ function at
618 type Int, represented by
620 Method 34 doubleId [Int] origin
622 In addition to the basic Haskell variants of 'Inst's, they can now also
623 represent implication constraints 'forall tvs. given => wanted'
624 and equality constraints 'co :: ty1 ~ ty2'.
626 NB: Equalities occur in two flavours:
628 (1) Dict {tci_pred = EqPred ty1 ty2}
629 (2) EqInst {tci_left = ty1, tci_right = ty2, tci_co = coe}
631 The former arises from equalities in contexts, whereas the latter is used
632 whenever the type checker introduces an equality (e.g., during deferring
635 I am not convinced that this duplication is necessary or useful! -=chak
641 tci_pred :: TcPredType,
645 | ImplicInst { -- An implication constraint
646 -- forall tvs. given => wanted
648 tci_tyvars :: [TcTyVar], -- Quantified type variables
649 tci_given :: [Inst], -- Only Dicts and EqInsts
650 -- (no Methods, LitInsts, ImplicInsts)
651 tci_wanted :: [Inst], -- Only Dicts, EqInst, and ImplicInsts
652 -- (no Methods or LitInsts)
656 -- NB: the tci_given are not necessarily rigid
659 tci_id :: TcId, -- The Id for the Inst
661 tci_oid :: TcId, -- The overloaded function
662 -- This function will be a global, local, or ClassOpId;
663 -- inside instance decls (only) it can also be an InstId!
664 -- The id needn't be completely polymorphic.
665 -- You'll probably find its name (for documentation purposes)
666 -- inside the InstOrigin
668 tci_tys :: [TcType], -- The types to which its polymorphic tyvars
669 -- should be instantiated.
670 -- These types must saturate the Id's foralls.
672 tci_theta :: TcThetaType,
673 -- The (types of the) dictionaries to which the function
674 -- must be applied to get the method
678 -- INVARIANT 1: in (Method m f tys theta tau loc)
679 -- type of m = type of (f tys dicts(from theta))
681 -- INVARIANT 2: type of m must not be of form (Pred -> Tau)
682 -- Reason: two methods are considered equal if the
683 -- base Id matches, and the instantiating types
684 -- match. The TcThetaType should then match too.
685 -- This only bites in the call to tcInstClassOp in TcClassDcl.mkMethodBind
689 tci_lit :: HsOverLit Name, -- The literal from the occurrence site
690 -- INVARIANT: never a rebindable-syntax literal
691 -- Reason: tcSyntaxName does unification, and we
692 -- don't want to deal with that during tcSimplify,
693 -- when resolving LitInsts
695 tci_ty :: TcType, -- The type at which the literal is used
699 | EqInst { -- delayed unification of the form
701 tci_left :: TcType, -- ty1 -- both types are...
702 tci_right :: TcType, -- ty2 -- ...free of boxes
703 tci_co :: Either -- co
704 TcTyVar -- - a wanted equation, with a hole, to be
705 -- filled with a witness for the equality;
706 -- for equation arising from deferring
707 -- unification, 'ty1' is the actual and
708 -- 'ty2' the expected type
709 Coercion, -- - a given equation, with a coercion
710 -- witnessing the equality;
711 -- a coercion that originates from a
712 -- signature or a GADT is a CoVar, but
713 -- after normalisation of coercions, they
714 -- can be arbitrary Coercions involving
715 -- constructors and pseudo-constructors
716 -- like sym and trans.
719 tci_name :: Name -- Debugging help only: this makes it easier to
720 -- follow where a constraint is used in a morass
721 -- of trace messages! Unlike other Insts, it has
722 -- no semantic significance whatsoever.
726 @Insts@ are ordered by their class/type info, rather than by their
727 unique. This allows the context-reduction mechanism to use standard finite
728 maps to do their stuff. It's horrible that this code is here, rather
729 than with the Avails handling stuff in TcSimplify
732 instance Ord Inst where
735 instance Eq Inst where
736 (==) i1 i2 = case i1 `cmpInst` i2 of
740 cmpInst :: Inst -> Inst -> Ordering
741 cmpInst d1@(Dict {}) d2@(Dict {}) = tci_pred d1 `tcCmpPred` tci_pred d2
742 cmpInst (Dict {}) _ = LT
744 cmpInst (Method {}) (Dict {}) = GT
745 cmpInst m1@(Method {}) m2@(Method {}) = (tci_oid m1 `compare` tci_oid m2) `thenCmp`
746 (tci_tys m1 `tcCmpTypes` tci_tys m2)
747 cmpInst (Method {}) _ = LT
749 cmpInst (LitInst {}) (Dict {}) = GT
750 cmpInst (LitInst {}) (Method {}) = GT
751 cmpInst l1@(LitInst {}) l2@(LitInst {}) = (tci_lit l1 `compare` tci_lit l2) `thenCmp`
752 (tci_ty l1 `tcCmpType` tci_ty l2)
753 cmpInst (LitInst {}) _ = LT
755 -- Implication constraints are compared by *name*
756 -- not by type; that is, we make no attempt to do CSE on them
757 cmpInst (ImplicInst {}) (Dict {}) = GT
758 cmpInst (ImplicInst {}) (Method {}) = GT
759 cmpInst (ImplicInst {}) (LitInst {}) = GT
760 cmpInst i1@(ImplicInst {}) i2@(ImplicInst {}) = tci_name i1 `compare` tci_name i2
761 cmpInst (ImplicInst {}) _ = LT
763 -- same for Equality constraints
764 cmpInst (EqInst {}) (Dict {}) = GT
765 cmpInst (EqInst {}) (Method {}) = GT
766 cmpInst (EqInst {}) (LitInst {}) = GT
767 cmpInst (EqInst {}) (ImplicInst {}) = GT
768 cmpInst i1@(EqInst {}) i2@(EqInst {}) = tci_name i1 `compare` tci_name i2
772 %************************************************************************
774 \subsection[Inst-collections]{LIE: a collection of Insts}
776 %************************************************************************
779 -- FIXME: Rename this. It clashes with (Located (IE ...))
782 isEmptyLIE :: LIE -> Bool
783 isEmptyLIE = isEmptyBag
788 unitLIE :: Inst -> LIE
789 unitLIE inst = unitBag inst
791 mkLIE :: [Inst] -> LIE
792 mkLIE insts = listToBag insts
794 plusLIE :: LIE -> LIE -> LIE
795 plusLIE lie1 lie2 = lie1 `unionBags` lie2
797 plusLIEs :: [LIE] -> LIE
798 plusLIEs lies = unionManyBags lies
800 lieToList :: LIE -> [Inst]
801 lieToList = bagToList
803 listToLIE :: [Inst] -> LIE
804 listToLIE = listToBag
806 consLIE :: Inst -> LIE -> LIE
807 consLIE inst lie = lie `snocBag` inst
808 -- Putting the new Inst at the *end* of the bag is a half-hearted attempt
809 -- to ensure that we tend to report the *leftmost* type-constraint error
812 -- we'd like to complain about the '1', not the '3'.
814 -- "Half-hearted" because the rest of the type checker makes no great
815 -- claims for retaining order in the constraint set. Still, this
816 -- seems to improve matters slightly. Exampes: mdofail001, tcfail015
820 %************************************************************************
822 \subsection[Inst-origin]{The @InstOrigin@ type}
824 %************************************************************************
826 The @InstOrigin@ type gives information about where a dictionary came from.
827 This is important for decent error message reporting because dictionaries
828 don't appear in the original source code. Doubtless this type will evolve...
830 It appears in TcMonad because there are a couple of error-message-generation
831 functions that deal with it.
834 -------------------------------------------
835 data InstLoc = InstLoc InstOrigin SrcSpan ErrCtxt
837 instLoc :: Inst -> InstLoc
838 instLoc inst = tci_loc inst
840 instSpan :: Inst -> SrcSpan
841 instSpan wanted = instLocSpan (instLoc wanted)
843 instLocSpan :: InstLoc -> SrcSpan
844 instLocSpan (InstLoc _ s _) = s
846 instLocOrigin :: InstLoc -> InstOrigin
847 instLocOrigin (InstLoc o _ _) = o
849 pprInstArising :: Inst -> SDoc
850 pprInstArising loc = ptext (sLit "arising from") <+> pprInstLoc (tci_loc loc)
852 pprInstLoc :: InstLoc -> SDoc
853 pprInstLoc (InstLoc orig span _) = sep [ppr orig, text "at" <+> ppr span]
855 -------------------------------------------
857 = SigOrigin SkolemInfo -- Pattern, class decl, inst decl etc;
858 -- Places that bind type variables and introduce
859 -- available constraints
861 | IPBindOrigin (IPName Name) -- Binding site of an implicit parameter
863 -------------------------------------------------------
864 -- The rest are all occurrences: Insts that are 'wanted'
865 -------------------------------------------------------
866 | OccurrenceOf Name -- Occurrence of an overloaded identifier
867 | SpecPragOrigin Name -- Specialisation pragma for identifier
869 | IPOccOrigin (IPName Name) -- Occurrence of an implicit parameter
871 | LiteralOrigin (HsOverLit Name) -- Occurrence of a literal
872 | NegateOrigin -- Occurrence of syntactic negation
874 | ArithSeqOrigin (ArithSeqInfo Name) -- [x..], [x..y] etc
875 | PArrSeqOrigin (ArithSeqInfo Name) -- [:x..y:] and [:x,y..z:]
876 | TupleOrigin -- (..,..)
878 | InstSigOrigin -- A dict occurrence arising from instantiating
879 -- a polymorphic type during a subsumption check
881 | ExprSigOrigin -- e :: ty
884 | InstScOrigin -- Typechecking superclasses of an instance declaration
885 | DerivOrigin -- Typechecking deriving
886 | StandAloneDerivOrigin -- Typechecking stand-alone deriving
887 | DefaultOrigin -- Typechecking a default decl
888 | DoOrigin -- Arising from a do expression
889 | ProcOrigin -- Arising from a proc expression
890 | ImplicOrigin SDoc -- An implication constraint
891 | EqOrigin -- A type equality
893 instance Outputable InstOrigin where
894 ppr (OccurrenceOf name) = hsep [ptext (sLit "a use of"), quotes (ppr name)]
895 ppr (SpecPragOrigin name) = hsep [ptext (sLit "a specialisation pragma for"), quotes (ppr name)]
896 ppr (IPOccOrigin name) = hsep [ptext (sLit "a use of implicit parameter"), quotes (ppr name)]
897 ppr (IPBindOrigin name) = hsep [ptext (sLit "a binding for implicit parameter"), quotes (ppr name)]
898 ppr RecordUpdOrigin = ptext (sLit "a record update")
899 ppr ExprSigOrigin = ptext (sLit "an expression type signature")
900 ppr ViewPatOrigin = ptext (sLit "a view pattern")
901 ppr (LiteralOrigin lit) = hsep [ptext (sLit "the literal"), quotes (ppr lit)]
902 ppr (ArithSeqOrigin seq) = hsep [ptext (sLit "the arithmetic sequence"), quotes (ppr seq)]
903 ppr (PArrSeqOrigin seq) = hsep [ptext (sLit "the parallel array sequence"), quotes (ppr seq)]
904 ppr TupleOrigin = ptext (sLit "a tuple")
905 ppr NegateOrigin = ptext (sLit "a use of syntactic negation")
906 ppr InstScOrigin = ptext (sLit "the superclasses of an instance declaration")
907 ppr DerivOrigin = ptext (sLit "the 'deriving' clause of a data type declaration")
908 ppr StandAloneDerivOrigin = ptext (sLit "a 'deriving' declaration")
909 ppr DefaultOrigin = ptext (sLit "a 'default' declaration")
910 ppr DoOrigin = ptext (sLit "a do statement")
911 ppr ProcOrigin = ptext (sLit "a proc expression")
912 ppr (ImplicOrigin doc) = doc
913 ppr (SigOrigin info) = pprSkolInfo info
914 ppr EqOrigin = ptext (sLit "a type equality")
915 ppr InstSigOrigin = panic "ppr InstSigOrigin"