content: {-
  (c) Rahul Muttineni 2016-2017
  (c) The University of Glasgow 2006
  (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
  
  
  Loading interface files
  -}
  
  {-# LANGUAGE CPP, BangPatterns, RecordWildCards, NondecreasingIndentation #-}
  {-# OPTIONS_GHC -fno-warn-orphans #-}
  module Eta.Iface.LoadIface (
          -- Importing one thing
          tcLookupImported_maybe, importDecl,
          checkWiredInTyCon, ifCheckWiredInThing,
  
          -- RnM/TcM functions
          loadModuleInterface, loadModuleInterfaces,
          loadSrcInterface, loadSrcInterface_maybe,
          loadInterfaceForName, loadInterfaceForModule,
  
          -- IfM functions
          loadInterface, loadWiredInHomeIface,
          loadSysInterface, loadUserInterface, loadPluginInterface,
          findAndReadIface, readIface,    -- Used when reading the module's old interface
          loadDecls,      -- Should move to TcIface and be renamed
          initExternalPackageState,
          moduleFreeHolesPrecise,
  
          pprModIfaceSimple,
  
          ifaceStats, pprModIface, showIface
     ) where
  
  import {-# SOURCE #-}   Eta.Iface.TcIface( tcIfaceDecl, tcIfaceRules, tcIfaceInst,
                                   tcIfaceFamInst, tcIfaceVectInfo, tcIfaceAnnotations )
  
  import {-# SOURCE #-}   Eta.Iface.MkJavaIface ( mkJavaIface )
  
  import Eta.Main.DynFlags
  import Eta.Iface.IfaceSyn
  import Eta.Iface.IfaceEnv
  import Eta.Main.HscTypes
  
  import Eta.BasicTypes.BasicTypes hiding (SuccessFlag(..))
  import Eta.TypeCheck.TcRnMonad
  
  import Eta.Main.Constants
  import Eta.Prelude.PrelNames
  import Eta.Prelude.PrelInfo
  import Eta.Prelude.PrimOp   ( allThePrimOps, primOpFixity, primOpOcc )
  import Eta.BasicTypes.MkId     ( seqId )
  import Eta.Specialise.Rules
  import Eta.Types.TyCon
  import Eta.Main.Annotations
  import Eta.Types.InstEnv
  import Eta.Types.FamInstEnv
  import Eta.BasicTypes.Name
  import Eta.BasicTypes.NameEnv
  import Eta.BasicTypes.Avail
  import Eta.BasicTypes.Module
  import Eta.Utils.Maybes
  import Eta.Main.ErrUtils
  import Eta.Main.Finder
  import Eta.Utils.UniqFM
  import Eta.BasicTypes.SrcLoc
  import Eta.Utils.Outputable
  import qualified Eta.Utils.Outputable as Outputable
  import Eta.Iface.BinIface
  import Eta.Utils.Panic
  import Eta.Utils.Util
  import Eta.Utils.FastString
  import Eta.Utils.Fingerprint
  import Eta.Main.Hooks
  import Eta.Backpack.RnModIface
  import Eta.Utils.UniqDSet
  
  import Control.Monad
  import Data.IORef
  import System.FilePath
  
  #include "HsVersions.h"
  
  {-
  ************************************************************************
  *                                                                      *
  *      tcImportDecl is the key function for "faulting in"              *
  *      imported things
  *                                                                      *
  ************************************************************************
  
  The main idea is this.  We are chugging along type-checking source code, and
  find a reference to GHC.Base.map.  We call tcLookupGlobal, which doesn't find
  it in the EPS type envt.  So it
          1 loads GHC.Base.hi
          2 gets the decl for GHC.Base.map
          3 typechecks it via tcIfaceDecl
          4 and adds it to the type env in the EPS
  
  Note that DURING STEP 4, we may find that map's type mentions a type
  constructor that also
  
  Notice that for imported things we read the current version from the EPS
  mutable variable.  This is important in situations like
          ...$(e1)...$(e2)...
  where the code that e1 expands to might import some defns that
  also turn out to be needed by the code that e2 expands to.
  -}
  
  tcLookupImported_maybe :: Name -> TcM (MaybeErr MsgDoc TyThing)
  -- Returns (Failed err) if we can't find the interface file for the thing
  tcLookupImported_maybe name
    = do  { hsc_env <- getTopEnv
          ; mb_thing <- liftIO (lookupTypeHscEnv hsc_env name)
          ; case mb_thing of
              Just thing -> return (Succeeded thing)
              Nothing    -> tcImportDecl_maybe name }
  
  tcImportDecl_maybe :: Name -> TcM (MaybeErr MsgDoc TyThing)
  -- Entry point for *source-code* uses of importDecl
  tcImportDecl_maybe name
    | Just thing <- wiredInNameTyThing_maybe name
    = do  { when (needWiredInHomeIface thing)
                 (initIfaceTcRn (loadWiredInHomeIface name))
                  -- See Note [Loading instances for wired-in things]
          ; return (Succeeded thing) }
    | otherwise
    = initIfaceTcRn (importDecl name)
  
  importDecl :: Name -> IfM lcl (MaybeErr MsgDoc TyThing)
  -- Get the TyThing for this Name from an interface file
  -- It's not a wired-in thing -- the caller caught that
  importDecl name
    = ASSERT( not (isWiredInName name) )
      do  { traceIf nd_doc
  
          -- Load the interface, which should populate the PTE
          ; mb_iface <- ASSERT2( isExternalName name, ppr name )
                        loadInterface nd_doc (nameModule name) ImportBySystem
          ; case mb_iface of {
                  Failed err_msg  -> return (Failed err_msg) ;
                  Succeeded _ -> do
  
          -- Now look it up again; this time we should find it
          { eps <- getEps
          ; case lookupTypeEnv (eps_PTE eps) name of
            Just thing -> return $ Succeeded thing
            Nothing    -> let doc = ifPprDebug (found_things_msg eps $$ empty)
                                    $$ not_found_msg
                          in return $ Failed doc
      }}}
    where
      nd_doc = ptext (sLit "Need decl for") <+> ppr name
      not_found_msg = hang (ptext (sLit "Can't find interface-file declaration for") <+>
                                  pprNameSpace (occNameSpace (nameOccName name)) <+> ppr name)
                         2 (vcat [ptext (sLit "Probable cause: bug in .hi-boot file, or inconsistent .hi file"),
                                  ptext (sLit "Use -ddump-if-trace to get an idea of which file caused the error")])
      found_things_msg eps =
              hang (text "Found the following declarations in" <+> ppr (nameModule name) <> colon)
                 2 (vcat (map ppr $ filter is_interesting $ nameEnvElts $ eps_PTE eps))
            where
              is_interesting thing = nameModule name == nameModule (getName thing)
  
  {-
  ************************************************************************
  *                                                                      *
             Checks for wired-in things
  *                                                                      *
  ************************************************************************
  
  Note [Loading instances for wired-in things]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  We need to make sure that we have at least *read* the interface files
  for any module with an instance decl or RULE that we might want.
  
  * If the instance decl is an orphan, we have a whole separate mechanism
    (loadOrphanModules)
  
  * If the instance decl is not an orphan, then the act of looking at the
    TyCon or Class will force in the defining module for the
    TyCon/Class, and hence the instance decl
  
  * BUT, if the TyCon is a wired-in TyCon, we don't really need its interface;
    but we must make sure we read its interface in case it has instances or
    rules.  That is what LoadIface.loadWiredInHomeInterface does.  It's called
    from TcIface.{tcImportDecl, checkWiredInTyCon, ifCheckWiredInThing}
  
  * HOWEVER, only do this for TyCons.  There are no wired-in Classes.  There
    are some wired-in Ids, but we don't want to load their interfaces. For
    example, Control.Exception.Base.recSelError is wired in, but that module
    is compiled late in the base library, and we don't want to force it to
    load before it's been compiled!
  
  All of this is done by the type checker. The renamer plays no role.
  (It used to, but no longer.)
  -}
  
  checkWiredInTyCon :: TyCon -> TcM ()
  -- Ensure that the home module of the TyCon (and hence its instances)
  -- are loaded. See Note [Loading instances for wired-in things]
  -- It might not be a wired-in tycon (see the calls in TcUnify),
  -- in which case this is a no-op.
  checkWiredInTyCon tc
    | not (isWiredInName tc_name)
    = return ()
    | otherwise
    = do  { mod <- getModule
          ; ASSERT( isExternalName tc_name )
            when (mod /= nameModule tc_name)
                 (initIfaceTcRn (loadWiredInHomeIface tc_name))
                  -- Don't look for (non-existent) Float.hi when
                  -- compiling Float.lhs, which mentions Float of course
                  -- A bit yukky to call initIfaceTcRn here
          }
    where
      tc_name = tyConName tc
  
  ifCheckWiredInThing :: TyThing -> IfL ()
  -- Even though we are in an interface file, we want to make
  -- sure the instances of a wired-in thing are loaded (imagine f :: Double -> Double)
  -- Ditto want to ensure that RULES are loaded too
  -- See Note [Loading instances for wired-in things]
  ifCheckWiredInThing thing
    = do  { mod <- getIfModule
                  -- Check whether we are typechecking the interface for this
                  -- very module.  E.g when compiling the base library in --make mode
                  -- we may typecheck GHC.Base.hi. At that point, GHC.Base is not in
                  -- the HPT, so without the test we'll demand-load it into the PIT!
                  -- C.f. the same test in checkWiredInTyCon above
          ; let name = getName thing
          ; ASSERT2( isExternalName name, ppr name )
            when (needWiredInHomeIface thing && mod /= nameModule name)
                 (loadWiredInHomeIface name) }
  
  needWiredInHomeIface :: TyThing -> Bool
  -- Only for TyCons; see Note [Loading instances for wired-in things]
  needWiredInHomeIface (ATyCon {}) = True
  needWiredInHomeIface _           = False
  
  
  {-
  ************************************************************************
  *                                                                      *
          loadSrcInterface, loadOrphanModules, loadInterfaceForName
  
                  These three are called from TcM-land
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Load the interface corresponding to an @import@ directive in
  -- source code.  On a failure, fail in the monad with an error message.
  
  loadSrcInterface :: SDoc
                   -> ModuleName
                   -> IsBootInterface     -- {-# SOURCE #-} ?
                   -> Maybe FastString    -- "package", if any
                   -> RnM ModIface
  
  loadSrcInterface doc mod want_boot maybe_pkg
    = do { res <- loadSrcInterface_maybe doc mod want_boot maybe_pkg
         ; case res of
             Failed err       -> failWithTc err
             Succeeded iface  -> return iface }
  
  -- | Like 'loadSrcInterface', but returns a 'MaybeErr'.  See also
  -- Note [Un-ambiguous multiple interfaces]
  loadSrcInterface_maybe :: SDoc
                         -> ModuleName
                         -> IsBootInterface     -- {-# SOURCE #-} ?
                         -> Maybe FastString    -- "package", if any
                         -> RnM (MaybeErr MsgDoc ModIface)
  
  loadSrcInterface_maybe doc mod want_boot maybe_pkg
    -- We must first find which Module this import refers to.  This involves
    -- calling the Finder, which as a side effect will search the filesystem
    -- and create a ModLocation.  If successful, loadIface will read the
    -- interface; it will call the Finder again, but the ModLocation will be
    -- cached from the first search.
    = do { hsc_env <- getTopEnv
         ; res <- liftIO $ findImportedModule hsc_env mod maybe_pkg
         ; case res of
             Found _ mod -> initIfaceTcRn $ loadInterface doc mod (ImportByUser want_boot)
             err         -> return (Failed (cannotFindModule (hsc_dflags hsc_env) mod err)) }
  
  -- | Load interface directly for a fully qualified 'Module'.  (This is a fairly
  -- rare operation, but in particular it is used to load orphan modules
  -- in order to pull their instances into the global package table and to
  -- handle some operations in GHCi).
  loadModuleInterface :: SDoc -> Module -> TcM ModIface
  loadModuleInterface doc mod = initIfaceTcRn (loadSysInterface doc mod)
  
  -- | Load interfaces for a collection of modules.
  loadModuleInterfaces :: SDoc -> [Module] -> TcM ()
  loadModuleInterfaces doc mods
    | null mods = return ()
    | otherwise = initIfaceTcRn (mapM_ load mods)
    where
      load mod = loadSysInterface (doc <+> parens (ppr mod)) mod
  
  -- | Loads the interface for a given Name.
  -- Should only be called for an imported name;
  -- otherwise loadSysInterface may not find the interface
  loadInterfaceForName :: SDoc -> Name -> TcRn ModIface
  loadInterfaceForName doc name
    = do { when debugIsOn $  -- Check pre-condition
           do { this_mod <- getModule
              ; MASSERT2( not (nameIsLocalOrFrom this_mod name), ppr name <+> parens doc ) }
        ; ASSERT2( isExternalName name, ppr name )
          initIfaceTcRn $ loadSysInterface doc (nameModule name) }
  
  -- | Loads the interface for a given Module.
  loadInterfaceForModule :: SDoc -> Module -> TcRn ModIface
  loadInterfaceForModule doc m
    = do
      -- Should not be called with this module
      when debugIsOn $ do
        this_mod <- getModule
        MASSERT2( this_mod /= m, ppr m <+> parens doc )
      initIfaceTcRn $ loadSysInterface doc m
  
  {-
  *********************************************************
  *                                                      *
                  loadInterface
  
          The main function to load an interface
          for an imported module, and put it in
          the External Package State
  *                                                      *
  *********************************************************
  -}
  
  -- | An 'IfM' function to load the home interface for a wired-in thing,
  -- so that we're sure that we see its instance declarations and rules
  -- See Note [Loading instances for wired-in things] in TcIface
  loadWiredInHomeIface :: Name -> IfM lcl ()
  loadWiredInHomeIface name
    = ASSERT( isWiredInName name )
      do _ <- loadSysInterface doc (nameModule name); return ()
    where
      doc = ptext (sLit "Need home interface for wired-in thing") <+> ppr name
  
  ------------------
  -- | Loads a system interface and throws an exception if it fails
  loadSysInterface :: SDoc -> Module -> IfM lcl ModIface
  loadSysInterface doc mod_name = loadInterfaceWithException doc mod_name ImportBySystem
  
  ------------------
  -- | Loads a user interface and throws an exception if it fails. The first parameter indicates
  -- whether we should import the boot variant of the module
  loadUserInterface :: Bool -> SDoc -> Module -> IfM lcl ModIface
  loadUserInterface is_boot doc mod_name
    = loadInterfaceWithException doc mod_name (ImportByUser is_boot)
  
  loadPluginInterface :: SDoc -> Module -> IfM lcl ModIface
  loadPluginInterface doc mod_name
    = loadInterfaceWithException doc mod_name ImportByPlugin
  
  ------------------
  -- | A wrapper for 'loadInterface' that throws an exception if it fails
  loadInterfaceWithException :: SDoc -> Module -> WhereFrom -> IfM lcl ModIface
  loadInterfaceWithException doc mod_name where_from
    = withException (loadInterface doc mod_name where_from)
  
  ------------------
  loadInterface :: SDoc -> Module -> WhereFrom
                -> IfM lcl (MaybeErr MsgDoc ModIface)
  
  -- loadInterface looks in both the HPT and PIT for the required interface
  -- If not found, it loads it, and puts it in the PIT (always).
  
  -- If it can't find a suitable interface file, we
  --      a) modify the PackageIfaceTable to have an empty entry
  --              (to avoid repeated complaints)
  --      b) return (Left message)
  --
  -- It's not necessarily an error for there not to be an interface
  -- file -- perhaps the module has changed, and that interface
  -- is no longer used
  
  loadInterface doc_str mod from
    | isHoleModule mod
    -- Hole modules get special treatment
    = do dflags <- getDynFlags
         -- Redo search for our local hole module
         loadInterface doc_str (mkModule (thisPackage dflags) (moduleName mod)) from
    | otherwise
    = do  {       -- Read the state
            (eps,hpt) <- getEpsAndHpt
  
          ; traceIf (text "Considering whether to load" <+> ppr mod <+> ppr from)
  
                  -- Check whether we have the interface already
          ; dflags <- getDynFlags
          ; case lookupIfaceByModule dflags hpt (eps_PIT eps) mod of {
              Just iface
                  -> return (Succeeded iface) ;   -- Already loaded
                          -- The (src_imp == mi_boot iface) test checks that the already-loaded
                          -- interface isn't a boot iface.  This can conceivably happen,
                          -- if an earlier import had a before we got to real imports.   I think.
              _ -> do {
  
          -- READ THE MODULE IN
          ; read_result <- case (wantHiBootFile dflags eps mod from) of
                             Failed err             -> return (Failed err)
                             Succeeded hi_boot_file -> computeInterface doc_str hi_boot_file mod
          ; case read_result of {
              Failed err -> do
                  { let fake_iface = emptyModIface mod
  
                  ; updateEps_ $ \eps ->
                          eps { eps_PIT = extendModuleEnv (eps_PIT eps) (mi_module fake_iface) fake_iface }
                          -- Not found, so add an empty iface to
                          -- the EPS map so that we don't look again
  
                  ; return (Failed err) } ;
  
          -- Found and parsed!
          -- We used to have a sanity check here that looked for:
          --  * System importing ..
          --  * a home package module ..
          --  * that we know nothing about (mb_dep == Nothing)!
          --
          -- But this is no longer valid because thNameToGhcName allows users to
          -- cause the system to load arbitrary interfaces (by supplying an appropriate
          -- Template Haskell original-name).
              Succeeded (iface, loc) ->
  
          let
              loc_doc = text loc
          in
          initIfaceLcl (mi_semantic_module iface) loc_doc (mi_boot iface) $ do
  
          dontLeakTheHPT $ do
  
          --      Load the new ModIface into the External Package State
          -- Even home-package interfaces loaded by loadInterface
          --      (which only happens in OneShot mode; in Batch/Interactive
          --      mode, home-package modules are loaded one by one into the HPT)
          -- are put in the EPS.
          --
          -- The main thing is to add the ModIface to the PIT, but
          -- we also take the
          --      IfaceDecls, IfaceClsInst, IfaceFamInst, IfaceRules, IfaceVectInfo
          -- out of the ModIface and put them into the big EPS pools
  
          -- NB: *first* we do loadDecl, so that the provenance of all the locally-defined
          ---    names is done correctly (notably, whether this is an .hi file or .hi-boot file).
          --     If we do loadExport first the wrong info gets into the cache (unless we
          --      explicitly tag each export which seems a bit of a bore)
  
          ; ignore_prags      <- goptM Opt_IgnoreInterfacePragmas
          ; new_eps_decls     <- loadDecls ignore_prags (mi_decls iface)
          ; new_eps_insts     <- mapM tcIfaceInst (mi_insts iface)
          ; new_eps_fam_insts <- mapM tcIfaceFamInst (mi_fam_insts iface)
          ; new_eps_rules     <- tcIfaceRules ignore_prags (mi_rules iface)
          ; new_eps_anns      <- tcIfaceAnnotations (mi_anns iface)
          ; new_eps_vect_info <- tcIfaceVectInfo mod (mkNameEnv new_eps_decls) (mi_vect_info iface)
  
          ; let { final_iface = iface {
                                  mi_decls     = panic "No mi_decls in PIT",
                                  mi_insts     = panic "No mi_insts in PIT",
                                  mi_fam_insts = panic "No mi_fam_insts in PIT",
                                  mi_rules     = panic "No mi_rules in PIT",
                                  mi_anns      = panic "No mi_anns in PIT"
                                }
                 }
  
          ; updateEps_  $ \ eps ->
              if elemModuleEnv mod (eps_PIT eps) || is_external_sig dflags iface
              then eps else
                case from of  -- See Note [Care with plugin imports]
                  ImportByPlugin -> eps {
                    eps_PIT          = extendModuleEnv (eps_PIT eps) mod final_iface,
                    eps_PTE          = addDeclsToPTE   (eps_PTE eps) new_eps_decls}
                  _              -> eps {
                    eps_PIT          = extendModuleEnv (eps_PIT eps) mod final_iface,
                    eps_PTE          = addDeclsToPTE   (eps_PTE eps) new_eps_decls,
                    eps_rule_base    = extendRuleBaseList (eps_rule_base eps)
                                                          new_eps_rules,
                    eps_inst_env     = extendInstEnvList (eps_inst_env eps)
                                                         new_eps_insts,
                    eps_fam_inst_env = extendFamInstEnvList (eps_fam_inst_env eps)
                                                            new_eps_fam_insts,
                    eps_vect_info    = plusVectInfo (eps_vect_info eps)
                                                    new_eps_vect_info,
                    eps_ann_env      = extendAnnEnvList (eps_ann_env eps)
                                                        new_eps_anns,
                    eps_mod_fam_inst_env
                                     = let
                                         fam_inst_env =
                                           extendFamInstEnvList emptyFamInstEnv
                                                                new_eps_fam_insts
                                       in
                                       extendModuleEnv (eps_mod_fam_inst_env eps)
                                                       mod
                                                       fam_inst_env,
                    eps_stats        = addEpsInStats (eps_stats eps)
                                                     (length new_eps_decls)
                                                     (length new_eps_insts)
                                                     (length new_eps_rules) }
  
          ; return (Succeeded final_iface)
      }}}}
  
  -- | Returns @True@ if a 'ModIface' comes from an external package.
  -- In this case, we should NOT load it into the EPS; the entities
  -- should instead come from the local merged signature interface.
  is_external_sig :: DynFlags -> ModIface -> Bool
  is_external_sig dflags iface =
      -- It's a signature iface...
      mi_semantic_module iface /= mi_module iface &&
      -- and it's not from the local package
      moduleUnitId (mi_module iface) /= thisPackage dflags
  
  -- | This is an improved version of 'findAndReadIface' which can also
  -- handle the case when a user requests @p[A=<B>]:M@ but we only
  -- have an interface for @p[A=<A>]:M@ (the indefinite interface.
  -- If we are not trying to build code, we load the interface we have,
  -- *instantiating it* according to how the holes are specified.
  -- (Of course, if we're actually building code, this is a hard error.)
  --
  -- In the presence of holes, 'computeInterface' has an important invariant:
  -- to load module M, its set of transitively reachable requirements must
  -- have an up-to-date local hi file for that requirement.  Note that if
  -- we are loading the interface of a requirement, this does not
  -- apply to the requirement itself; e.g., @p[A=<A>]:A@ does not require
  -- A.hi to be up-to-date (and indeed, we MUST NOT attempt to read A.hi, unless
  -- we are actually typechecking p.)
  computeInterface ::
         SDoc -> IsBootInterface -> Module
      -> TcRnIf gbl lcl (MaybeErr MsgDoc (ModIface, FilePath))
  computeInterface doc_str hi_boot_file mod0 = do
      MASSERT( not (isHoleModule mod0) )
      dflags <- getDynFlags
      case splitModuleInsts mod0 of
          (imod, Just indef) | not (unitIdIsDefinite (thisPackage dflags)) -> do
              r <- findAndReadIface doc_str imod mod0 hi_boot_file
              case r of
                  Succeeded (iface0, path) -> do
                      hsc_env <- getTopEnv
                      r <- liftIO $
                            rnModIface hsc_env (indefUnitIdInsts (indefModuleUnitId indef)) Nothing iface0
                      return (Succeeded (r, path))
                  Failed err -> return (Failed err)
          (mod, _) ->
              findAndReadIface doc_str mod mod0 hi_boot_file
  
  -- | Compute the signatures which must be compiled in order to
  -- load the interface for a 'Module'.  The output of this function
  -- is always a subset of 'moduleFreeHoles'; it is more precise
  -- because in signature @p[A=<A>,B=<B>]:B@, although the free holes
  -- are A and B, B might not depend on A at all!
  --
  -- If this is invoked on a signature, this does NOT include the
  -- signature itself; e.g. precise free module holes of
  -- @p[A=<A>,B=<B>]:B@ never includes B.
  moduleFreeHolesPrecise
      :: SDoc -> Module
      -> TcRnIf gbl lcl (MaybeErr MsgDoc (UniqDSet ModuleName))
  moduleFreeHolesPrecise doc_str mod
   | moduleIsDefinite mod = return (Succeeded emptyUniqDSet)
   | otherwise =
     case splitModuleInsts mod of
      (imod, Just indef) -> do
          let insts = indefUnitIdInsts (indefModuleUnitId indef)
          traceIf (text "Considering whether to load" <+> ppr mod <+>
                   text "to compute precise free module holes")
          (eps, hpt) <- getEpsAndHpt
          dflags <- getDynFlags
          case tryEpsAndHpt dflags eps hpt `firstJust` tryDepsCache eps imod insts of
              Just r -> return (Succeeded r)
              Nothing -> readAndCache imod insts
      (_, Nothing) -> return (Succeeded emptyUniqDSet)
    where
      tryEpsAndHpt dflags eps hpt =
          fmap mi_free_holes (lookupIfaceByModule dflags hpt (eps_PIT eps) mod)
      tryDepsCache eps imod insts =
          case lookupInstalledModuleEnv (eps_free_holes eps) imod of
              Just ifhs  -> Just (renameFreeHoles ifhs insts)
              _otherwise -> Nothing
      readAndCache imod insts = do
          mb_iface <- findAndReadIface (text "moduleFreeHolesPrecise" <+> doc_str) imod mod False
          case mb_iface of
              Succeeded (iface, _) -> do
                  let ifhs = mi_free_holes iface
                  -- Cache it
                  updateEps_ (\eps ->
                      eps { eps_free_holes = extendInstalledModuleEnv (eps_free_holes eps) imod ifhs })
                  return (Succeeded (renameFreeHoles ifhs insts))
              Failed err -> return (Failed err)
  
  -- Note [HPT space leak] (#15111)
  --
  -- In IfL, we defer some work until it is demanded using forkM, such
  -- as building TyThings from IfaceDecls. These thunks are stored in
  -- the ExternalPackageState, and they might never be poked.  If we're
  -- not careful, these thunks will capture the state of the loaded
  -- program when we read an interface file, and retain all that data
  -- for ever.
  --
  -- Therefore, when loading a package interface file , we use a "clean"
  -- version of the HscEnv with all the data about the currently loaded
  -- program stripped out. Most of the fields can be panics because
  -- we'll never read them, but hsc_HPT needs to be empty because this
  -- interface will cause other interfaces to be loaded recursively, and
  -- when looking up those interfaces we use the HPT in loadInterface.
  -- We know that none of the interfaces below here can refer to
  -- home-package modules however, so it's safe for the HPT to be empty.
  --
  dontLeakTheHPT :: IfL a -> IfL a
  dontLeakTheHPT thing_inside = do
    let
      cleanTopEnv HscEnv{..} =
         let
           -- wrinkle: when we're typechecking in --backpack mode, the
           -- instantiation of a signature might reside in the HPT, so
           -- this case breaks the assumption that EPS interfaces only
           -- refer to other EPS interfaces. We can detect when we're in
           -- typechecking-only mode by using hscTarget==HscNothing, and
           -- in that case we don't empty the HPT.  (admittedly this is
           -- a bit of a hack, better suggestions welcome). A number of
           -- tests in testsuite/tests/backpack break without this
           -- tweak.
           !hpt | hscTarget hsc_dflags == HscNothing = hsc_HPT
                | otherwise = emptyHomePackageTable
         in
         HscEnv {  hsc_targets      = panic "cleanTopEnv: hsc_targets"
                ,  hsc_mod_graph    = panic "cleanTopEnv: hsc_mod_graph"
                ,  hsc_IC           = panic "cleanTopEnv: hsc_IC"
                ,  hsc_HPT          = hpt
                , .. }
  
    updTopEnv cleanTopEnv $ do
    !_ <- getTopEnv        -- force the updTopEnv
    thing_inside
  
  wantHiBootFile :: DynFlags -> ExternalPackageState -> Module -> WhereFrom
                 -> MaybeErr MsgDoc IsBootInterface
  -- Figure out whether we want Foo.hi or Foo.hi-boot
  wantHiBootFile dflags eps mod from
    = case from of
         ImportByUser usr_boot
            | usr_boot && not this_package
            -> Failed (badSourceImport mod)
            | otherwise -> Succeeded usr_boot
  
         ImportByPlugin
            -> Succeeded False
  
         ImportBySystem
            | not this_package   -- If the module to be imported is not from this package
            -> Succeeded False   -- don't look it up in eps_is_boot, because that is keyed
                                 -- on the ModuleName of *home-package* modules only.
                                 -- We never import boot modules from other packages!
  
            | otherwise
            -> case lookupUFM (eps_is_boot eps) (moduleName mod) of
                  Just (_, is_boot) -> Succeeded is_boot
                  Nothing           -> Succeeded False
                       -- The boot-ness of the requested interface,
                       -- based on the dependencies in directly-imported modules
    where
      this_package = thisPackage dflags == moduleUnitId mod
  
  badSourceImport :: Module -> SDoc
  badSourceImport mod
    = hang (ptext (sLit "You cannot {-# SOURCE #-} import a module from another package"))
         2 (ptext (sLit "but") <+> quotes (ppr mod) <+> ptext (sLit "is from package")
            <+> quotes (ppr (moduleUnitId mod)))
  
  {-
  Note [Care with plugin imports]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  When dynamically loading a plugin (via loadPluginInterface) we
  populate the same External Package State (EPS), even though plugin
  modules are to link with the compiler itself, and not with the
  compiled program.  That's fine: mostly the EPS is just a cache for
  the interace files on disk.
  
  But it's NOT ok for the RULES or instance environment.  We do not want
  to fire a RULE from the plugin on the code we are compiling, otherwise
  the code we are compiling will have a reference to a RHS of the rule
  that exists only in the compiler!  This actually happened to Daniel,
  via a RULE arising from a specialisation of (^) in the plugin.
  
  Solution: when loading plugins, do not extend the rule and instance
  environments.  We are only interested in the type environment, so that
  we can check that the plugin exports a function with the type that the
  compiler expects.
  -}
  
  -----------------------------------------------------
  --      Loading type/class/value decls
  -- We pass the full Module name here, replete with
  -- its package info, so that we can build a Name for
  -- each binder with the right package info in it
  -- All subsequent lookups, including crucially lookups during typechecking
  -- the declaration itself, will find the fully-glorious Name
  --
  -- We handle ATs specially.  They are not main declarations, but also not
  -- implicit things (in particular, adding them to `implicitTyThings' would mess
  -- things up in the renaming/type checking of source programs).
  -----------------------------------------------------
  
  addDeclsToPTE :: PackageTypeEnv -> [(Name,TyThing)] -> PackageTypeEnv
  addDeclsToPTE pte things = extendNameEnvList pte things
  
  loadDecls :: Bool
            -> [(Fingerprint, IfaceDecl)]
            -> IfL [(Name,TyThing)]
  loadDecls ignore_prags ver_decls
     = do { mod <- getIfModule
          ; thingss <- mapM (loadDecl ignore_prags mod) ver_decls
          ; return (concat thingss)
          }
  
  loadDecl :: Bool                    -- Don't load pragmas into the decl pool
           -> Module
            -> (Fingerprint, IfaceDecl)
            -> IfL [(Name,TyThing)]   -- The list can be poked eagerly, but the
                                      -- TyThings are forkM'd thunks
  loadDecl ignore_prags mod (_version, decl)
    = do  {       -- Populate the name cache with final versions of all
                  -- the names associated with the decl
            let main_name = ifName decl
  
          -- Typecheck the thing, lazily
          -- NB. Firstly, the laziness is there in case we never need the
          -- declaration (in one-shot mode), and secondly it is there so that
          -- we don't look up the occurrence of a name before calling mk_new_bndr
          -- on the binder.  This is important because we must get the right name
          -- which includes its nameParent.
  
          ; thing <- forkM doc $ do { bumpDeclStats main_name
                                    ; tcIfaceDecl ignore_prags decl }
  
          -- Populate the type environment with the implicitTyThings too.
          --
          -- Note [Tricky iface loop]
          -- ~~~~~~~~~~~~~~~~~~~~~~~~
          -- Summary: The delicate point here is that 'mini-env' must be
          -- buildable from 'thing' without demanding any of the things
          -- 'forkM'd by tcIfaceDecl.
          --
          -- In more detail: Consider the example
          --      data T a = MkT { x :: T a }
          -- The implicitTyThings of T are:  [ <datacon MkT>, <selector x>]
          -- (plus their workers, wrappers, coercions etc etc)
          --
          -- We want to return an environment
          --      [ "MkT" -> <datacon MkT>, "x" -> <selector x>, ... ]
          -- (where the "MkT" is the *Name* associated with MkT, etc.)
          --
          -- We do this by mapping the implicit_names to the associated
          -- TyThings.  By the invariant on ifaceDeclImplicitBndrs and
          -- implicitTyThings, we can use getOccName on the implicit
          -- TyThings to make this association: each Name's OccName should
          -- be the OccName of exactly one implicitTyThing.  So the key is
          -- to define a "mini-env"
          --
          -- [ 'MkT' -> <datacon MkT>, 'x' -> <selector x>, ... ]
          -- where the 'MkT' here is the *OccName* associated with MkT.
          --
          -- However, there is a subtlety: due to how type checking needs
          -- to be staged, we can't poke on the forkM'd thunks inside the
          -- implicitTyThings while building this mini-env.
          -- If we poke these thunks too early, two problems could happen:
          --    (1) When processing mutually recursive modules across
          --        hs-boot boundaries, poking too early will do the
          --        type-checking before the recursive knot has been tied,
          --        so things will be type-checked in the wrong
          --        environment, and necessary variables won't be in
          --        scope.
          --
          --    (2) Looking up one OccName in the mini_env will cause
          --        others to be looked up, which might cause that
          --        original one to be looked up again, and hence loop.
          --
          -- The code below works because of the following invariant:
          -- getOccName on a TyThing does not force the suspended type
          -- checks in order to extract the name. For example, we don't
          -- poke on the "T a" type of <selector x> on the way to
          -- extracting <selector x>'s OccName. Of course, there is no
          -- reason in principle why getting the OccName should force the
          -- thunks, but this means we need to be careful in
          -- implicitTyThings and its helper functions.
          --
          -- All a bit too finely-balanced for my liking.
  
          -- This mini-env and lookup function mediates between the
          --'Name's n and the map from 'OccName's to the implicit TyThings
          ; let mini_env = mkOccEnv [(getOccName t, t) | t <- implicitTyThings thing]
                lookup n = case lookupOccEnv mini_env (getOccName n) of
                             Just thing -> thing
                             Nothing    ->
                               pprPanic "loadDecl" (ppr main_name <+> ppr n $$ ppr (decl))
  
          ; implicit_names <- mapM (lookupOrig mod) (ifaceDeclImplicitBndrs decl)
  
  --         ; traceIf (text "Loading decl for " <> ppr main_name $$ ppr implicit_names)
          ; return $ (main_name, thing) :
                        -- uses the invariant that implicit_names and
                        -- implicitTyThings are bijective
                        [(n, lookup n) | n <- implicit_names]
          }
    where
      doc = ptext (sLit "Declaration for") <+> ppr (ifName decl)
  
  bumpDeclStats :: Name -> IfL ()         -- Record that one more declaration has actually been used
  bumpDeclStats name
    = do  { traceIf (text "Loading decl for" <+> ppr name)
          ; updateEps_ (\eps -> let stats = eps_stats eps
                                in eps { eps_stats = stats { n_decls_out = n_decls_out stats + 1 } })
          }
  
  {-
  *********************************************************
  *                                                      *
  \subsection{Reading an interface file}
  *                                                      *
  *********************************************************
  
  Note [Home module load error]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  If the sought-for interface is in the current package (as determined
  by -package-name flag) then it jolly well should already be in the HPT
  because we process home-package modules in dependency order.  (Except
  in one-shot mode; see notes with hsc_HPT decl in HscTypes).
  
  It is possible (though hard) to get this error through user behaviour.
    * Suppose package P (modules P1, P2) depends on package Q (modules Q1,
      Q2, with Q2 importing Q1)
    * We compile both packages.
    * Now we edit package Q so that it somehow depends on P
    * Now recompile Q with --make (without recompiling P).
    * Then Q1 imports, say, P1, which in turn depends on Q2. So Q2
      is a home-package module which is not yet in the HPT!  Disaster.
  
  This actually happened with P=base, Q=ghc-prim, via the AMP warnings.
  See Trac #8320.
  -}
  
  findAndReadIface :: SDoc
                   -> InstalledModule
                   -> Module
                   -> IsBootInterface     -- True  <=> Look for a .hi-boot file
                                          -- False <=> Look for .hi file
                   -> TcRnIf gbl lcl (MaybeErr MsgDoc (ModIface, FilePath))
          -- Nothing <=> file not found, or unreadable, or illegible
          -- Just x  <=> successfully found and parsed
  
          -- It *doesn't* add an error to the monad, because
          -- sometimes it's ok to fail... see notes with loadInterface
  
  findAndReadIface doc_str mod wanted_mod_with_insts hi_boot_file
    = do traceIf (sep [hsep [ptext (sLit "Reading"),
                             if hi_boot_file
                               then ptext (sLit "[boot]")
                               else Outputable.empty,
                             ptext (sLit "interface for"),
                             ppr mod <> semi],
                       nest 4 (ptext (sLit "reason:") <+> doc_str)])
  
         -- Check for GHC.Prim, and return its static interface
         -- TODO: make this check a function
         if mod `installedModuleEq` gHC_PRIM
         then do iface <- getHooked ghcPrimIfaceHook ghcPrimIface
                 return (Succeeded (iface, "<built in interface for GHC.Prim>"))
         else do
           dflags <- getDynFlags
           -- Look for the file
           hsc_env <- getTopEnv
           mb_found <- liftIO (findExactModule hsc_env mod)
           case mb_found of
               InstalledFound loc mod
                 | installedModuleUnitId mod `installedUnitIdEq` javaUnitId -> do
  
                   -- Direct java interop
                   let mod_name = moduleNameString (installedModuleName mod)
                   javaIface <- mkJavaIface mod_name
                   return (Succeeded (javaIface, mod_name))
  
                 | otherwise -> do
  
                   -- Found file, so read it
                   let file_path = addBootSuffix_maybe hi_boot_file
                                                       (ml_hi_file loc)
  
                   -- See Note [Home module load error]
                   if installedModuleUnitId mod `installedUnitIdEq` thisPackage dflags &&
                       not (isOneShot (ghcMode dflags))
                       then return (Failed (homeModError mod loc))
                       else do r <- read_file file_path
                               checkBuildDynamicToo r
                               return r
               err -> do
                 traceIf (ptext (sLit "...not found"))
                 dflags <- getDynFlags
                 return (Failed (cannotFindInterface dflags (installedModuleName mod) err))
      where read_file file_path = do
                traceIf (ptext (sLit "readIFace") <+> text file_path)
                dflags <- getDynFlags
                let wanted_mod =
                      case splitModuleInsts wanted_mod_with_insts of
                          (_, Nothing) -> wanted_mod_with_insts
                          (_, Just indef_mod) ->
                            indefModuleToModule dflags
                              (generalizeIndefModule indef_mod)
                read_result <- readIface wanted_mod file_path
                case read_result of
                  Failed err -> return (Failed (badIfaceFile file_path err))
                  Succeeded iface -> return (Succeeded (iface, file_path))
  
                              -- Don't forget to fill in the package name...
            checkBuildDynamicToo (Succeeded (iface, filePath)) = do
                dflags <- getDynFlags
                -- Indefinite interfaces are ALWAYS non-dynamic, and
                -- that's OK.
                let is_definite_iface = moduleIsDefinite (mi_module iface)
                when is_definite_iface $
                  whenGeneratingDynamicToo dflags $ withDoDynamicToo $ do
                    let ref = canGenerateDynamicToo dflags
                        dynFilePath = addBootSuffix_maybe hi_boot_file
                                    $ replaceExtension filePath (dynHiSuf dflags)
                    r <- read_file dynFilePath
                    case r of
                        Succeeded (dynIface, _)
                         | mi_mod_hash iface == mi_mod_hash dynIface ->
                            return ()
                         | otherwise ->
                            do traceIf (text "Dynamic hash doesn't match")
                               liftIO $ writeIORef ref False
                        Failed err ->
                            do traceIf (text "Failed to load dynamic interface file:" $$ err)
                               liftIO $ writeIORef ref False
            checkBuildDynamicToo _ = return ()
  
  -- @readIface@ tries just the one file.
  
  readIface :: Module -> FilePath
            -> TcRnIf gbl lcl (MaybeErr MsgDoc ModIface)
          -- Failed err    <=> file not found, or unreadable, or illegible
          -- Succeeded iface <=> successfully found and parsed
  
  readIface wanted_mod file_path
    = do  { res <- tryMostM $
                   readBinIface CheckHiWay QuietBinIFaceReading file_path
          ; dflags <- getDynFlags
          ; case res of
              Right iface
                  -- NB: This check is NOT just a sanity check, it is
                  -- critical for correctness of recompilation checking
                  -- (it lets us tell when -this-unit-id has changed.)
                  | wanted_mod == actual_mod -> return (Succeeded iface)
                  | otherwise                -> return (Failed err)
                  where
                    actual_mod = mi_module iface
                    err = hiModuleNameMismatchWarn dflags wanted_mod actual_mod
  
              Left exn    -> return (Failed (text (showException exn)))
      }
  
  {-
  *********************************************************
  *                                                       *
          Wired-in interface for GHC.Prim
  *                                                       *
  *********************************************************
  -}
  
  initExternalPackageState :: ExternalPackageState
  initExternalPackageState
    = EPS {
        eps_is_boot      = emptyUFM,
        eps_PIT          = emptyPackageIfaceTable,
        eps_free_holes   = emptyInstalledModuleEnv,
        eps_PTE          = emptyTypeEnv,
        eps_inst_env     = emptyInstEnv,
        eps_fam_inst_env = emptyFamInstEnv,
        eps_rule_base    = mkRuleBase builtinRules,
          -- Initialise the EPS rule pool with the built-in rules
        eps_mod_fam_inst_env
                         = emptyModuleEnv,
        eps_vect_info    = noVectInfo,
        eps_ann_env      = emptyAnnEnv,
        eps_stats = EpsStats { n_ifaces_in = 0, n_decls_in = 0, n_decls_out = 0
                             , n_insts_in = 0, n_insts_out = 0
                             , n_rules_in = length builtinRules, n_rules_out = 0 }
      }
  
  {-
  *********************************************************
  *                                                       *
          Wired-in interface for GHC.Prim
  *                                                       *
  *********************************************************
  -}
  
  ghcPrimIface :: ModIface
  ghcPrimIface
    = (emptyModIface gHC_PRIM) {
          mi_exports  = ghcPrimExports,
          mi_decls    = [],
          mi_fixities = fixities,
          mi_fix_fn  = mkIfaceFixCache fixities
      }
    where
      fixities = (getOccName seqId, Fixity 0 InfixR)  -- seq is infixr 0
               : mapMaybe mkFixity allThePrimOps
      mkFixity op = (,) (primOpOcc op) <$> primOpFixity op
  
  {-
  *********************************************************
  *                                                      *
  \subsection{Statistics}
  *                                                      *
  *********************************************************
  -}
  
  ifaceStats :: ExternalPackageState -> SDoc
  ifaceStats eps
    = hcat [text "Renamer stats: ", msg]
    where
      stats = eps_stats eps
      msg = vcat
          [int (n_ifaces_in stats) <+> text "interfaces read",
           hsep [ int (n_decls_out stats), text "type/class/variable imported, out of",
                  int (n_decls_in stats), text "read"],
           hsep [ int (n_insts_out stats), text "instance decls imported, out of",
                  int (n_insts_in stats), text "read"],
           hsep [ int (n_rules_out stats), text "rule decls imported, out of",
                  int (n_rules_in stats), text "read"]
          ]
  
  {-
  ************************************************************************
  *                                                                      *
                  Printing interfaces
  *                                                                      *
  ************************************************************************
  -}
  
  -- | Read binary interface, and print it out
  showIface :: HscEnv -> FilePath -> IO ()
  showIface hsc_env filename = do
     -- skip the hi way check; we don't want to worry about profiled vs.
     -- non-profiled interfaces, for example.
     iface <- initTcRnIf 's' hsc_env () () $
         readBinIface IgnoreHiWay TraceBinIFaceReading filename
     let dflags = hsc_dflags hsc_env
     putLogMsg dflags NoReason SevDump noSrcSpan (defaultDumpStyle dflags) (pprModIface iface)
  
  -- Show a ModIface but don't display details; suitable for ModIfaces stored in
  -- the EPT.
  pprModIfaceSimple :: ModIface -> SDoc
  pprModIfaceSimple iface = ppr (mi_module iface) $$ pprDeps
      (mi_deps iface) $$ nest 2 (vcat (map pprExport (mi_exports iface)))
  
  
  pprModIface :: ModIface -> SDoc
  -- Show a ModIface
  pprModIface iface
   = vcat [ ptext (sLit "interface")
                  <+> ppr (mi_module iface) <+> pp_hsc_src (mi_hsc_src iface)
                  <+> (if mi_orphan iface then ptext (sLit "[orphan module]") else Outputable.empty)
                  <+> (if mi_finsts iface then ptext (sLit "[family instance module]") else Outputable.empty)
                  <+> (if mi_hpc    iface then ptext (sLit "[hpc]") else Outputable.empty)
                  <+> integer hiVersion
          , nest 2 (text "interface hash:" <+> ppr (mi_iface_hash iface))
          , nest 2 (text "ABI hash:" <+> ppr (mi_mod_hash iface))
          , nest 2 (text "export-list hash:" <+> ppr (mi_exp_hash iface))
          , nest 2 (text "orphan hash:" <+> ppr (mi_orphan_hash iface))
          , nest 2 (text "flag hash:" <+> ppr (mi_flag_hash iface))
          , nest 2 (text "sig of:" <+> ppr (mi_sig_of iface))
          , nest 2 (text "used TH splices:" <+> ppr (mi_used_th iface))
          , nest 2 (ptext (sLit "where"))
          , ptext (sLit "exports:")
          , nest 2 (vcat (map pprExport (mi_exports iface)))
          , pprDeps (mi_deps iface)
          , vcat (map pprUsage (mi_usages iface))
          , vcat (map pprIfaceAnnotation (mi_anns iface))
          , pprFixities (mi_fixities iface)
          , vcat [ppr ver $$ nest 2 (ppr decl) | (ver,decl) <- mi_decls iface]
          , vcat (map ppr (mi_insts iface))
          , vcat (map ppr (mi_fam_insts iface))
          , vcat (map ppr (mi_rules iface))
          , pprVectInfo (mi_vect_info iface)
          , ppr (mi_warns iface)
          , pprTrustInfo (mi_trust iface)
          , pprTrustPkg (mi_trust_pkg iface)
          ]
    where
      pp_hsc_src HsBootFile = ptext (sLit "[boot]")
      pp_hsc_src HsigFile = ptext (sLit "[hsig]")
      pp_hsc_src HsSrcFile = Outputable.empty
  
  {-
  When printing export lists, we print like this:
          Avail   f               f
          AvailTC C [C, x, y]     C(x,y)
          AvailTC C [x, y]        C!(x,y)         -- Exporting x, y but not C
  -}
  
  pprExport :: IfaceExport -> SDoc
  pprExport (Avail n)      = ppr n
  pprExport (AvailTC _ []) = Outputable.empty
  pprExport (AvailTC n (n':ns))
    | n==n'     = ppr n <> pp_export ns
    | otherwise = ppr n <> char '|' <> pp_export (n':ns)
    where
      pp_export []    = Outputable.empty
      pp_export names = braces (hsep (map ppr names))
  
  pprUsage :: Usage -> SDoc
  pprUsage usage@UsagePackageModule{}
    = pprUsageImport usage usg_mod
  pprUsage usage@UsageHomeModule{}
    = pprUsageImport usage usg_mod_name $$
      nest 2 (
          maybe Outputable.empty (\v -> text "exports: " <> ppr v) (usg_exports usage) $$
          vcat [ ppr n <+> ppr v | (n,v) <- usg_entities usage ]
          )
  pprUsage usage@UsageFile{}
    = hsep [ptext (sLit "addDependentFile"),
            doubleQuotes (text (usg_file_path usage))]
  
  pprUsage usage@UsageMergedRequirement{}
    = hsep [text "merged", ppr (usg_mod usage), ppr (usg_mod_hash usage)]
  
  pprUsageImport :: Outputable a => Usage -> (Usage -> a) -> SDoc
  pprUsageImport usage usg_mod'
    = hsep [ptext (sLit "import"), safe, ppr (usg_mod' usage),
                         ppr (usg_mod_hash usage)]
      where
          safe | usg_safe usage = ptext $ sLit "safe"
               | otherwise      = ptext $ sLit " -/ "
  
  pprDeps :: Dependencies -> SDoc
  pprDeps (Deps { dep_mods = mods, dep_pkgs = pkgs, dep_orphs = orphs,
                  dep_finsts = finsts })
    = vcat [ptext (sLit "module dependencies:") <+> fsep (map ppr_mod mods),
            ptext (sLit "package dependencies:") <+> fsep (map ppr_pkg pkgs),
            ptext (sLit "orphans:") <+> fsep (map ppr orphs),
            ptext (sLit "family instance modules:") <+> fsep (map ppr finsts)
          ]
    where
      ppr_mod (mod_name, boot) = ppr mod_name <+> ppr_boot boot
      ppr_pkg (pkg,trust_req)  = ppr pkg <>
                                 (if trust_req then text "*" else Outputable.empty)
      ppr_boot True  = text "[boot]"
      ppr_boot False = Outputable.empty
  
  pprFixities :: [(OccName, Fixity)] -> SDoc
  pprFixities []    = Outputable.empty
  pprFixities fixes = ptext (sLit "fixities") <+> pprWithCommas pprFix fixes
                    where
                      pprFix (occ,fix) = ppr fix <+> ppr occ
  
  pprVectInfo :: IfaceVectInfo -> SDoc
  pprVectInfo (IfaceVectInfo { ifaceVectInfoVar            = vars
                             , ifaceVectInfoTyCon          = tycons
                             , ifaceVectInfoTyConReuse     = tyconsReuse
                             , ifaceVectInfoParallelVars   = parallelVars
                             , ifaceVectInfoParallelTyCons = parallelTyCons
                             }) =
    vcat
    [ ptext (sLit "vectorised variables:") <+> hsep (map ppr vars)
    , ptext (sLit "vectorised tycons:") <+> hsep (map ppr tycons)
    , ptext (sLit "vectorised reused tycons:") <+> hsep (map ppr tyconsReuse)
    , ptext (sLit "parallel variables:") <+> hsep (map ppr parallelVars)
    , ptext (sLit "parallel tycons:") <+> hsep (map ppr parallelTyCons)
    ]
  
  pprTrustInfo :: IfaceTrustInfo -> SDoc
  pprTrustInfo trust = ptext (sLit "trusted:") <+> ppr trust
  
  pprTrustPkg :: Bool -> SDoc
  pprTrustPkg tpkg = ptext (sLit "require own pkg trusted:") <+> ppr tpkg
  
  instance Outputable Warnings where
      ppr = pprWarns
  
  pprWarns :: Warnings -> SDoc
  pprWarns NoWarnings         = Outputable.empty
  pprWarns (WarnAll txt)  = ptext (sLit "Warn all") <+> ppr txt
  pprWarns (WarnSome prs) = ptext (sLit "Warnings")
                          <+> vcat (map pprWarning prs)
      where pprWarning (name, txt) = ppr name <+> ppr txt
  
  pprIfaceAnnotation :: IfaceAnnotation -> SDoc
  pprIfaceAnnotation (IfaceAnnotation { ifAnnotatedTarget = target, ifAnnotatedValue = serialized })
    = ppr target <+> ptext (sLit "annotated by") <+> ppr serialized
  
  {-
  *********************************************************
  *                                                       *
  \subsection{Errors}
  *                                                       *
  *********************************************************
  -}
  
  badIfaceFile :: String -> SDoc -> SDoc
  badIfaceFile file err
    = vcat [ptext (sLit "Bad interface file:") <+> text file,
            nest 4 err]
  
  hiModuleNameMismatchWarn :: DynFlags -> Module -> Module -> MsgDoc
  hiModuleNameMismatchWarn dflags requested_mod read_mod
    | moduleUnitId requested_mod == moduleUnitId read_mod =
     sep [text "Interface file contains module" <+> quotes (ppr read_mod) <> comma,
          text "but we were expecting module" <+> quotes (ppr requested_mod),
          sep [text "Probable cause: the source code which generated interface file",
              text "has an incompatible module name"
             ]
         ]
   | otherwise =
    -- ToDo: This will fail to have enough qualification when the package IDs
    -- are the same
    withPprStyle (mkUserStyle dflags alwaysQualify AllTheWay) $
      -- we want the Modules below to be qualified with package names,
      -- so reset the PrintUnqualified setting.
      hsep [ ptext (sLit "Something is amiss; requested module ")
           , ppr requested_mod
           , ptext (sLit "differs from name found in the interface file")
           , ppr read_mod
           , parens (text "if these names look the same, try again with -dppr-debug")
           ]
  
  homeModError :: InstalledModule -> ModLocation -> SDoc
  -- See Note [Home module load error]
  homeModError mod location
    = ptext (sLit "attempting to use module ") <> quotes (ppr mod)
      <> (case ml_hs_file location of
             Just file -> space <> parens (text file)
             Nothing   -> Outputable.empty)
      <+> ptext (sLit "which is not loaded")
  