2 % (c) The University of Glasgow, 2000
4 \section[HscTypes]{Types for the per-module compiler}
12 ModDetails(..), ModIface(..),
13 HomeSymbolTable, emptySymbolTable,
15 HomeIfaceTable, PackageIfaceTable, emptyIfaceTable,
16 lookupIface, lookupIfaceByModName,
19 InteractiveContext(..),
21 IfaceDecls, mkIfaceDecls, dcl_tycl, dcl_rules, dcl_insts,
23 VersionInfo(..), initialVersionInfo, lookupVersion,
25 TyThing(..), isTyClThing, implicitTyThingIds,
27 TypeEnv, lookupType, mkTypeEnv, emptyTypeEnv,
28 extendTypeEnvList, extendTypeEnvWithIds,
29 typeEnvElts, typeEnvClasses, typeEnvTyCons, typeEnvIds,
31 ImportedModuleInfo, WhetherHasOrphans, ImportVersion, WhatsImported(..),
32 PersistentRenamerState(..), IsBootInterface, DeclsMap,
33 IfaceInsts, IfaceRules, GatedDecl, GatedDecls, GateFn, IsExported,
34 NameSupply(..), OrigNameCache, OrigIParamCache,
35 Avails, AvailEnv, emptyAvailEnv,
36 GenAvailInfo(..), AvailInfo, RdrAvailInfo,
37 PersistentCompilerState(..),
39 Deprecations(..), lookupDeprec,
41 InstEnv, ClsInstEnv, DFunId,
42 PackageInstEnv, PackageRuleBase,
44 GlobalRdrEnv, GlobalRdrElt(..), pprGlobalRdrEnv,
45 LocalRdrEnv, extendLocalRdrEnv,
49 Provenance(..), ImportReason(..),
50 pprNameProvenance, hasBetterProv
54 #include "HsVersions.h"
56 import RdrName ( RdrName, RdrNameEnv, addListToRdrEnv, emptyRdrEnv,
57 mkRdrUnqual, rdrEnvToList )
58 import Name ( Name, NamedThing, getName, nameOccName, nameModule, nameSrcLoc )
60 import OccName ( OccName )
61 import Module ( Module, ModuleName, ModuleEnv,
62 lookupModuleEnv, lookupModuleEnvByName, emptyModuleEnv
64 import InstEnv ( InstEnv, ClsInstEnv, DFunId )
65 import Rules ( RuleBase )
66 import CoreSyn ( CoreBind )
68 import Class ( Class, classSelIds )
69 import TyCon ( TyCon, isNewTyCon, tyConGenIds, tyConSelIds, tyConDataConsIfAvailable )
70 import DataCon ( dataConId, dataConWrapId )
72 import BasicTypes ( Version, initialVersion, Fixity, IPName )
74 import HsSyn ( DeprecTxt, tyClDeclName, ifaceRuleDeclName )
75 import RdrHsSyn ( RdrNameInstDecl, RdrNameRuleDecl, RdrNameTyClDecl )
76 import RnHsSyn ( RenamedTyClDecl, RenamedRuleDecl, RenamedInstDecl )
78 import CoreSyn ( IdCoreRule )
80 import FiniteMap ( FiniteMap )
82 import Maybes ( seqMaybe, orElse )
84 import SrcLoc ( SrcLoc, isGoodSrcLoc )
85 import Util ( thenCmp, sortLt )
86 import UniqSupply ( UniqSupply )
89 %************************************************************************
91 \subsection{Which mode we're in
93 %************************************************************************
96 data GhciMode = Batch | Interactive | OneShot
101 %************************************************************************
103 \subsection{Module locations}
105 %************************************************************************
110 ml_hs_file :: Maybe FilePath,
111 ml_hspp_file :: Maybe FilePath, -- path of preprocessed source
112 ml_hi_file :: FilePath,
113 ml_obj_file :: Maybe FilePath
117 instance Outputable ModuleLocation where
121 For a module in another package, the hs_file and obj_file
122 components of ModuleLocation are undefined.
124 The locations specified by a ModuleLocation may or may not
125 correspond to actual files yet: for example, even if the object
126 file doesn't exist, the ModuleLocation still contains the path to
127 where the object file will reside if/when it is created.
130 %************************************************************************
132 \subsection{Symbol tables and Module details}
134 %************************************************************************
136 A @ModIface@ plus a @ModDetails@ summarises everything we know
137 about a compiled module. The @ModIface@ is the stuff *before* linking,
138 and can be written out to an interface file. (The @ModDetails@ is after
139 linking; it is the "linked" form of the mi_decls field.)
141 When we *read* an interface file, we also construct a @ModIface@ from it,
142 except that the mi_decls part is empty; when reading we consolidate
143 the declarations into a single indexed map in the @PersistentRenamerState@.
148 mi_module :: !Module, -- Complete with package info
149 mi_version :: !VersionInfo, -- Module version number
151 mi_orphan :: WhetherHasOrphans, -- Whether this module has orphans
152 -- NOT STRICT! we fill this field with _|_ sometimes
154 mi_boot :: !IsBootInterface, -- read from an hi-boot file?
156 mi_usages :: ![ImportVersion Name],
157 -- Usages; kept sorted so that it's easy to decide
158 -- whether to write a new iface file (changing usages
159 -- doesn't affect the version of this module)
161 mi_exports :: ![(ModuleName,Avails)],
162 -- What it exports Kept sorted by (mod,occ), to make
163 -- version comparisons easier
165 mi_globals :: !(Maybe GlobalRdrEnv),
166 -- Its top level environment or Nothing if we read this
167 -- interface from a file.
169 mi_fixities :: !(NameEnv Fixity), -- Fixities
170 mi_deprecs :: !Deprecations, -- Deprecations
172 mi_decls :: IfaceDecls -- The RnDecls form of ModDetails
173 -- NOT STRICT! we fill this field with _|_ sometimes
176 data IfaceDecls = IfaceDecls { dcl_tycl :: [RenamedTyClDecl], -- Sorted
177 dcl_rules :: [RenamedRuleDecl], -- Sorted
178 dcl_insts :: [RenamedInstDecl] } -- Unsorted
180 mkIfaceDecls :: [RenamedTyClDecl] -> [RenamedRuleDecl] -> [RenamedInstDecl] -> IfaceDecls
181 mkIfaceDecls tycls rules insts
182 = IfaceDecls { dcl_tycl = sortLt lt_tycl tycls,
183 dcl_rules = sortLt lt_rule rules,
186 d1 `lt_tycl` d2 = tyClDeclName d1 < tyClDeclName d2
187 r1 `lt_rule` r2 = ifaceRuleDeclName r1 < ifaceRuleDeclName r2
190 -- typechecker should only look at this, not ModIface
191 -- Should be able to construct ModDetails from mi_decls in ModIface
194 -- The next three fields are created by the typechecker
195 md_types :: !TypeEnv,
196 md_insts :: ![DFunId], -- Dfun-ids for the instances in this module
197 md_rules :: ![IdCoreRule], -- Domain may include Ids from other modules
198 md_binds :: ![CoreBind]
201 -- The ModDetails takes on several slightly different forms:
203 -- After typecheck + desugar
204 -- md_types Contains TyCons, Classes, and implicit Ids
205 -- md_insts All instances from this module (incl derived ones)
206 -- md_rules All rules from this module
207 -- md_binds Desugared bindings
209 -- After simplification
210 -- md_types Same as after typecheck
212 -- md_rules Orphan rules only (local ones now attached to binds)
213 -- md_binds With rules attached
216 -- md_types Now contains Ids as well, replete with final IdInfo
217 -- The Ids are only the ones that are visible from
218 -- importing modules. Without -O that means only
219 -- exported Ids, but with -O importing modules may
220 -- see ids mentioned in unfoldings of exported Ids
222 -- md_insts Same DFunIds as before, but with final IdInfo,
223 -- and the unique might have changed; remember that
224 -- CoreTidy links up the uniques of old and new versions
226 -- md_rules All rules for exported things, substituted with final Ids
230 -- Passed back to compilation manager
231 -- Just as after CoreTidy, but with md_binds nuked
236 emptyModIface :: Module -> ModIface
238 = ModIface { mi_module = mod,
239 mi_version = initialVersionInfo,
244 mi_fixities = emptyNameEnv,
245 mi_globals = Nothing,
246 mi_deprecs = NoDeprecs,
247 mi_decls = panic "emptyModIface: decls"
251 Symbol tables map modules to ModDetails:
254 type SymbolTable = ModuleEnv ModDetails
255 type IfaceTable = ModuleEnv ModIface
257 type HomeIfaceTable = IfaceTable
258 type PackageIfaceTable = IfaceTable
260 type HomeSymbolTable = SymbolTable -- Domain = modules in the home package
262 emptySymbolTable :: SymbolTable
263 emptySymbolTable = emptyModuleEnv
265 emptyIfaceTable :: IfaceTable
266 emptyIfaceTable = emptyModuleEnv
269 Simple lookups in the symbol table.
272 lookupIface :: HomeIfaceTable -> PackageIfaceTable -> Name -> Maybe ModIface
273 -- We often have two IfaceTables, and want to do a lookup
274 lookupIface hit pit name
275 = lookupModuleEnv hit mod `seqMaybe` lookupModuleEnv pit mod
277 mod = nameModule name
279 lookupIfaceByModName :: HomeIfaceTable -> PackageIfaceTable -> ModuleName -> Maybe ModIface
280 -- We often have two IfaceTables, and want to do a lookup
281 lookupIfaceByModName hit pit mod
282 = lookupModuleEnvByName hit mod `seqMaybe` lookupModuleEnvByName pit mod
286 %************************************************************************
288 \subsection{The interactive context}
290 %************************************************************************
293 data InteractiveContext
294 = InteractiveContext {
295 ic_toplev_scope :: [Module], -- Include the "top-level" scope of
298 ic_exports :: [Module], -- Include just the exports of these
301 ic_rn_gbl_env :: GlobalRdrEnv, -- The cached GlobalRdrEnv, built from
302 -- ic_toplev_scope and ic_exports
304 ic_print_unqual :: PrintUnqualified,
305 -- cached PrintUnqualified, as above
307 ic_rn_local_env :: LocalRdrEnv, -- Lexical context for variables bound
308 -- during interaction
310 ic_type_env :: TypeEnv -- Ditto for types
315 %************************************************************************
317 \subsection{Type environment stuff}
319 %************************************************************************
322 data TyThing = AnId Id
326 isTyClThing :: TyThing -> Bool
327 isTyClThing (ATyCon _) = True
328 isTyClThing (AClass _) = True
329 isTyClThing (AnId _) = False
331 instance NamedThing TyThing where
332 getName (AnId id) = getName id
333 getName (ATyCon tc) = getName tc
334 getName (AClass cl) = getName cl
336 instance Outputable TyThing where
337 ppr (AnId id) = ptext SLIT("AnId") <+> ppr id
338 ppr (ATyCon tc) = ptext SLIT("ATyCon") <+> ppr tc
339 ppr (AClass cl) = ptext SLIT("AClass") <+> ppr cl
342 typeEnvElts :: TypeEnv -> [TyThing]
343 typeEnvClasses :: TypeEnv -> [Class]
344 typeEnvTyCons :: TypeEnv -> [TyCon]
345 typeEnvIds :: TypeEnv -> [Id]
347 typeEnvElts env = nameEnvElts env
348 typeEnvClasses env = [cl | AClass cl <- typeEnvElts env]
349 typeEnvTyCons env = [tc | ATyCon tc <- typeEnvElts env]
350 typeEnvIds env = [id | AnId id <- typeEnvElts env]
352 implicitTyThingIds :: [TyThing] -> [Id]
353 -- Add the implicit data cons and selectors etc
354 implicitTyThingIds things
355 = concat (map go things)
358 go (AClass cl) = classSelIds cl
359 go (ATyCon tc) = tyConGenIds tc ++
361 [ n | dc <- tyConDataConsIfAvailable tc,
362 n <- implicitConIds tc dc]
363 -- Synonyms return empty list of constructors and selectors
365 implicitConIds tc dc -- Newtypes have a constructor wrapper,
367 | isNewTyCon tc = [dataConWrapId dc]
368 | otherwise = [dataConId dc, dataConWrapId dc]
373 type TypeEnv = NameEnv TyThing
375 emptyTypeEnv = emptyNameEnv
377 mkTypeEnv :: [TyThing] -> TypeEnv
378 mkTypeEnv things = extendTypeEnvList emptyTypeEnv things
380 extendTypeEnvList :: TypeEnv -> [TyThing] -> TypeEnv
381 extendTypeEnvList env things
382 = extendNameEnvList env [(getName thing, thing) | thing <- things]
384 extendTypeEnvWithIds :: TypeEnv -> [Id] -> TypeEnv
385 extendTypeEnvWithIds env ids
386 = extendNameEnvList env [(getName id, AnId id) | id <- ids]
390 lookupType :: HomeSymbolTable -> PackageTypeEnv -> Name -> Maybe TyThing
391 lookupType hst pte name
392 = case lookupModuleEnv hst (nameModule name) of
393 Just details -> lookupNameEnv (md_types details) name
394 Nothing -> lookupNameEnv pte name
397 %************************************************************************
399 \subsection{Auxiliary types}
401 %************************************************************************
403 These types are defined here because they are mentioned in ModDetails,
404 but they are mostly elaborated elsewhere
409 vers_module :: Version, -- Changes when anything changes
410 vers_exports :: Version, -- Changes when export list changes
411 vers_rules :: Version, -- Changes when any rule changes
412 vers_decls :: NameEnv Version
413 -- Versions for "big" names only (not data constructors, class ops)
414 -- The version of an Id changes if its fixity changes
415 -- Ditto data constructors, class operations, except that the version of
416 -- the parent class/tycon changes
418 -- If a name isn't in the map, it means 'initialVersion'
421 initialVersionInfo :: VersionInfo
422 initialVersionInfo = VersionInfo { vers_module = initialVersion,
423 vers_exports = initialVersion,
424 vers_rules = initialVersion,
425 vers_decls = emptyNameEnv
428 lookupVersion :: NameEnv Version -> Name -> Version
429 lookupVersion env name = lookupNameEnv env name `orElse` initialVersion
431 data Deprecations = NoDeprecs
432 | DeprecAll DeprecTxt -- Whole module deprecated
433 | DeprecSome (NameEnv (Name,DeprecTxt)) -- Some things deprecated
435 -- We keep the Name in the range, so we can print them out
437 lookupDeprec :: Deprecations -> Name -> Maybe DeprecTxt
438 lookupDeprec NoDeprecs name = Nothing
439 lookupDeprec (DeprecAll txt) name = Just txt
440 lookupDeprec (DeprecSome env) name = case lookupNameEnv env name of
441 Just (_, txt) -> Just txt
444 instance Eq Deprecations where
445 -- Used when checking whether we need write a new interface
446 NoDeprecs == NoDeprecs = True
447 (DeprecAll t1) == (DeprecAll t2) = t1 == t2
448 (DeprecSome e1) == (DeprecSome e2) = nameEnvElts e1 == nameEnvElts e2
454 type Avails = [AvailInfo]
455 type AvailInfo = GenAvailInfo Name
456 type RdrAvailInfo = GenAvailInfo OccName
458 data GenAvailInfo name = Avail name -- An ordinary identifier
459 | AvailTC name -- The name of the type or class
460 [name] -- The available pieces of type/class.
461 -- NB: If the type or class is itself
462 -- to be in scope, it must be in this list.
463 -- Thus, typically: AvailTC Eq [Eq, ==, /=]
465 -- Equality used when deciding if the interface has changed
467 type AvailEnv = NameEnv AvailInfo -- Maps a Name to the AvailInfo that contains it
469 emptyAvailEnv :: AvailEnv
470 emptyAvailEnv = emptyNameEnv
472 instance Outputable n => Outputable (GenAvailInfo n) where
475 pprAvail :: Outputable n => GenAvailInfo n -> SDoc
476 pprAvail (AvailTC n ns) = ppr n <> case {- filter (/= n) -} ns of
478 ns' -> braces (hsep (punctuate comma (map ppr ns')))
480 pprAvail (Avail n) = ppr n
484 %************************************************************************
486 \subsection{ModIface}
488 %************************************************************************
491 type WhetherHasOrphans = Bool
493 -- * an instance decl in a module other than the defn module for
494 -- one of the tycons or classes in the instance head
495 -- * a transformation rule in a module other than the one defining
496 -- the function in the head of the rule.
498 type IsBootInterface = Bool
500 type ImportVersion name = (ModuleName, WhetherHasOrphans, IsBootInterface, WhatsImported name)
502 data WhatsImported name = NothingAtAll -- The module is below us in the
503 -- hierarchy, but we import nothing
505 | Everything Version -- Used for modules from other packages;
506 -- we record only the module's version number
509 Version -- Module version
510 (Maybe Version) -- Export-list version, if we depend on it
511 [(name,Version)] -- List guaranteed non-empty
512 Version -- Rules version
515 -- 'Specifically' doesn't let you say "I imported f but none of the rules in
516 -- the module". If you use anything in the module you get its rule version
517 -- So if the rules change, you'll recompile, even if you don't use them.
518 -- This is easy to implement, and it's safer: you might not have used the rules last
519 -- time round, but if someone has added a new rule you might need it this time
521 -- The export list field is (Just v) if we depend on the export list:
522 -- we imported the module without saying exactly what we imported
523 -- We need to recompile if the module exports changes, because we might
524 -- now have a name clash in the importing module.
526 type IsExported = Name -> Bool -- True for names that are exported from this module
530 %************************************************************************
532 \subsection{The persistent compiler state}
534 %************************************************************************
536 The @PersistentCompilerState@ persists across successive calls to the
539 * A ModIface for each non-home-package module
541 * An accumulated TypeEnv from all the modules in imported packages
543 * An accumulated InstEnv from all the modules in imported packages
544 The point is that we don't want to keep recreating it whenever
545 we compile a new module. The InstEnv component of pcPST is empty.
546 (This means we might "see" instances that we shouldn't "really" see;
547 but the Haskell Report is vague on what is meant to be visible,
548 so we just take the easy road here.)
552 * The persistent renamer state
555 data PersistentCompilerState
557 pcs_PIT :: !PackageIfaceTable, -- Domain = non-home-package modules
558 -- the mi_decls component is empty
560 pcs_PTE :: !PackageTypeEnv, -- Domain = non-home-package modules
561 -- except that the InstEnv components is empty
563 pcs_insts :: !PackageInstEnv, -- The total InstEnv accumulated from all
564 -- the non-home-package modules
566 pcs_rules :: !PackageRuleBase, -- Ditto RuleEnv
568 pcs_PRS :: !PersistentRenamerState
573 The persistent renamer state contains:
575 * A name supply, which deals with allocating unique names to
576 (Module,OccName) original names,
578 * A "holding pen" for declarations that have been read out of
579 interface files but not yet sucked in, renamed, and typechecked
582 type PackageTypeEnv = TypeEnv
583 type PackageRuleBase = RuleBase
584 type PackageInstEnv = InstEnv
586 data PersistentRenamerState
587 = PRS { prsOrig :: !NameSupply,
588 prsImpMods :: !ImportedModuleInfo,
590 -- Holding pens for stuff that has been read in
591 -- but not yet slurped into the renamer
592 prsDecls :: !DeclsMap,
593 prsInsts :: !IfaceInsts,
594 prsRules :: !IfaceRules
598 The NameSupply makes sure that there is just one Unique assigned for
599 each original name; i.e. (module-name, occ-name) pair. The Name is
600 always stored as a Global, and has the SrcLoc of its binding location.
601 Actually that's not quite right. When we first encounter the original
602 name, we might not be at its binding site (e.g. we are reading an
603 interface file); so we give it 'noSrcLoc' then. Later, when we find
604 its binding site, we fix it up.
606 Exactly the same is true of the Module stored in the Name. When we first
607 encounter the occurrence, we may not know the details of the module, so
608 we just store junk. Then when we find the binding site, we fix it up.
612 = NameSupply { nsUniqs :: UniqSupply,
614 nsNames :: OrigNameCache,
615 -- Ensures that one original name gets one unique
616 nsIPs :: OrigIParamCache
617 -- Ensures that one implicit parameter name gets one unique
620 type OrigNameCache = FiniteMap (ModuleName,OccName) Name
621 type OrigIParamCache = FiniteMap (IPName RdrName) (IPName Name)
624 @ImportedModuleInfo@ contains info ONLY about modules that have not yet
625 been loaded into the iPIT. These modules are mentioned in interfaces we've
626 already read, so we know a tiny bit about them, but we havn't yet looked
627 at the interface file for the module itself. It needs to persist across
628 invocations of the renamer, at least from Rename.checkOldIface to Rename.renameSource.
629 And there's no harm in it persisting across multiple compilations.
632 type ImportedModuleInfo = FiniteMap ModuleName (WhetherHasOrphans, IsBootInterface)
635 A DeclsMap contains a binding for each Name in the declaration
636 including the constructors of a type decl etc. The Bool is True just
640 type DeclsMap = (NameEnv (AvailInfo, Bool, (Module, RdrNameTyClDecl)), Int)
641 -- The Int says how many have been sucked in
643 type IfaceInsts = GatedDecls RdrNameInstDecl
644 type IfaceRules = GatedDecls RdrNameRuleDecl
646 type GatedDecls d = (Bag (GatedDecl d), Int) -- The Int says how many have been sucked in
647 type GatedDecl d = (GateFn, (Module, d))
648 type GateFn = (Name -> Bool) -> Bool -- Returns True <=> gate is open
649 -- The (Name -> Bool) fn returns True for visible Names
650 -- For example, suppose this is in an interface file
651 -- instance C T where ...
652 -- We want to slurp this decl if both C and T are "visible" in
653 -- the importing module. See "The gating story" in RnIfaces for details.
657 %************************************************************************
659 \subsection{Provenance and export info}
661 %************************************************************************
663 A LocalRdrEnv is used for local bindings (let, where, lambda, case)
666 type LocalRdrEnv = RdrNameEnv Name
668 extendLocalRdrEnv :: LocalRdrEnv -> [Name] -> LocalRdrEnv
669 extendLocalRdrEnv env names
670 = addListToRdrEnv env [(mkRdrUnqual (nameOccName n), n) | n <- names]
673 The GlobalRdrEnv gives maps RdrNames to Names. There is a separate
674 one for each module, corresponding to that module's top-level scope.
677 type GlobalRdrEnv = RdrNameEnv [GlobalRdrElt]
678 -- The list is because there may be name clashes
679 -- These only get reported on lookup, not on construction
681 data GlobalRdrElt = GRE Name Provenance (Maybe DeprecTxt)
682 -- The Maybe DeprecTxt tells whether this name is deprecated
685 = vcat (map pp (rdrEnvToList env))
687 pp (rn, nps) = ppr rn <> colon <+>
688 vcat [ppr n <+> pprNameProvenance n p | (GRE n p _) <- nps]
691 The "provenance" of something says how it came to be in scope.
695 = LocalDef -- Defined locally
697 | NonLocalDef -- Defined non-locally
700 -- Just used for grouping error messages (in RnEnv.warnUnusedBinds)
701 instance Eq Provenance where
702 p1 == p2 = case p1 `compare` p2 of EQ -> True; _ -> False
704 instance Eq ImportReason where
705 p1 == p2 = case p1 `compare` p2 of EQ -> True; _ -> False
707 instance Ord Provenance where
708 compare LocalDef LocalDef = EQ
709 compare LocalDef (NonLocalDef _) = LT
710 compare (NonLocalDef _) LocalDef = GT
712 compare (NonLocalDef reason1) (NonLocalDef reason2)
713 = compare reason1 reason2
715 instance Ord ImportReason where
716 compare ImplicitImport ImplicitImport = EQ
717 compare ImplicitImport (UserImport _ _ _) = LT
718 compare (UserImport _ _ _) ImplicitImport = GT
719 compare (UserImport m1 loc1 _) (UserImport m2 loc2 _)
720 = (m1 `compare` m2) `thenCmp` (loc1 `compare` loc2)
724 = UserImport Module SrcLoc Bool -- Imported from module M on line L
725 -- Note the M may well not be the defining module
727 -- The Bool is true iff the thing was named *explicitly* in the import spec,
728 -- rather than being imported as part of a group; e.g.
731 -- Here, everything imported by B, and the constructors of T
732 -- are not named explicitly; only T is named explicitly.
733 -- This info is used when warning of unused names.
735 | ImplicitImport -- Imported implicitly for some other reason
739 hasBetterProv :: Provenance -> Provenance -> Bool
741 -- a local thing over an imported thing
742 -- a user-imported thing over a non-user-imported thing
743 -- an explicitly-imported thing over an implicitly imported thing
744 hasBetterProv LocalDef _ = True
745 hasBetterProv (NonLocalDef (UserImport _ _ _ )) (NonLocalDef ImplicitImport) = True
746 hasBetterProv _ _ = False
748 pprNameProvenance :: Name -> Provenance -> SDoc
749 pprNameProvenance name LocalDef = ptext SLIT("defined at") <+> ppr (nameSrcLoc name)
750 pprNameProvenance name (NonLocalDef why) = sep [ppr_reason why,
751 nest 2 (ppr_defn (nameSrcLoc name))]
753 ppr_reason ImplicitImport = ptext SLIT("implicitly imported")
754 ppr_reason (UserImport mod loc _) = ptext SLIT("imported from") <+> ppr mod <+> ptext SLIT("at") <+> ppr loc
756 ppr_defn loc | isGoodSrcLoc loc = parens (ptext SLIT("at") <+> ppr loc)