root/compiler/iface/LoadIface.lhs

%
% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%

Loading interface files

\begin{code}
module LoadIface (
        -- RnM/TcM functions
        loadModuleInterface, loadModuleInterfaces, 
        loadSrcInterface, loadInterfaceForName, 

        -- IfM functions
        loadInterface, loadWiredInHomeIface, 
        loadSysInterface, loadUserInterface, 
        findAndReadIface, readIface,    -- Used when reading the module's old interface
        loadDecls,      -- Should move to TcIface and be renamed
        initExternalPackageState,

        ifaceStats, pprModIface, showIface
   ) where

#include "HsVersions.h"

import {-# SOURCE #-}   TcIface( tcIfaceDecl, tcIfaceRules, tcIfaceInst, 
                                 tcIfaceFamInst, tcIfaceVectInfo, tcIfaceAnnotations )

import DynFlags
import IfaceSyn
import IfaceEnv
import HscTypes

import BasicTypes hiding (SuccessFlag(..))
import TcRnMonad

import PrelNames
import PrelInfo
import MkId     ( seqId )
import Rules
import Annotations
import InstEnv
import FamInstEnv
import Name
import NameEnv
import Avail
import Module
import Maybes
import ErrUtils
import Finder
import UniqFM
import StaticFlags
import Outputable
import BinIface
import Panic
import Util
import FastString
import Fingerprint

import Control.Monad
\end{code}


%************************************************************************
%*                                                                      *
        loadSrcInterface, loadOrphanModules, loadInterfaceForName

                These three are called from TcM-land    
%*                                                                      *
%************************************************************************

\begin{code}
-- | 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
  -- 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.
  hsc_env <- getTopEnv
  res <- liftIO $ findImportedModule hsc_env mod maybe_pkg
  case res of
    Found _ mod -> do
      mb_iface <- initIfaceTcRn $ loadInterface doc mod (ImportByUser want_boot)
      case mb_iface of
        Failed err      -> failWithTc err
        Succeeded iface -> return iface
    err ->
        let dflags = hsc_dflags hsc_env in
        failWithTc (cannotFindInterface dflags mod err)

-- | Load interface for a module.
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.
loadInterfaceForName :: SDoc -> Name -> TcRn ModIface
loadInterfaceForName doc name
  = do { 
    when debugIsOn $ do
        -- Should not be called with a name from the module being compiled
        { this_mod <- getModule
        ; MASSERT2( not (nameIsLocalOrFrom this_mod name), ppr name <+> parens doc )
        }
  ; ASSERT2( isExternalName name, ppr name ) 
    initIfaceTcRn $ loadSysInterface doc (nameModule name)
  }
\end{code}


%*********************************************************
%*                                                      *
                loadInterface

        The main function to load an interface
        for an imported module, and put it in
        the External Package State
%*                                                      *
%*********************************************************

\begin{code}
-- | 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)

------------------
-- | A wrapper for 'loadInterface' that throws an exception if it fails
loadInterfaceWithException :: SDoc -> Module -> WhereFrom -> IfM lcl ModIface
loadInterfaceWithException doc mod_name where_from
  = do  { mb_iface <- loadInterface doc mod_name where_from
        ; case mb_iface of 
            Failed err      -> ghcError (ProgramError (showSDoc err))
            Succeeded iface -> return iface }

------------------
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
  = 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 -> findAndReadIface doc_str mod hi_boot_file
        ; 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, file_path) ->

        let 
            loc_doc = text file_path
        in 
        initIfaceLcl mod loc_doc $ 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      <- doptM 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) then eps else
            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)
    }}}}

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

       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 == modulePackageId 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 (modulePackageId mod)))
\end{code}

{-
Used to be used for the loadInterface sanity check on system imports. That has been removed, but I'm leaving this in pending
review of this decision by SPJ - MCB 10/2008

badDepMsg :: Module -> SDoc
badDepMsg mod 
  = hang (ptext (sLit "Interface file inconsistency:"))
       2 (sep [ptext (sLit "home-package module") <+> quotes (ppr mod) <+> ptext (sLit "is needed,"), 
               ptext (sLit "but is not listed in the dependencies of the interfaces directly imported by the module being compiled")])
-}

\begin{code}
-----------------------------------------------------
--      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
-- implict 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
          main_name      <- lookupOrig mod (ifName decl)
--        ; traceIf (text "Loading decl for " <> ppr main_name)

        -- 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 implict_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 implictTyThing.  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
        -- implictTyThings 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)
        ; return $ (main_name, thing) :
                      -- uses the invariant that implicit_names and
                      -- implictTyThings 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 } })
        }
\end{code}


%*********************************************************
%*                                                      *
\subsection{Reading an interface file}
%*                                                      *
%*********************************************************

\begin{code}
findAndReadIface :: SDoc -> 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 hi_boot_file
  = do  { traceIf (sep [hsep [ptext (sLit "Reading"), 
                              if hi_boot_file 
                                then ptext (sLit "[boot]") 
                                else empty,
                              ptext (sLit "interface for"), 
                              ppr mod <> semi],
                        nest 4 (ptext (sLit "reason:") <+> doc_str)])

        -- Check for GHC.Prim, and return its static interface
        ; dflags <- getDynFlags
        ; if mod == gHC_PRIM
          then return (Succeeded (ghcPrimIface,
                                   "<built in interface for GHC.Prim>"))
          else do

        -- Look for the file
        ; hsc_env <- getTopEnv
        ; mb_found <- liftIO (findExactModule hsc_env mod)
        ; case mb_found of {
              
              Found loc mod -> do 

        -- Found file, so read it
        { let { file_path = addBootSuffix_maybe hi_boot_file (ml_hi_file loc) }

        -- If the interface is in the current package then if we could
        -- load it would already be in the HPT and we assume that our
        -- callers checked that.
        ; if thisPackage dflags == modulePackageId mod
                && not (isOneShot (ghcMode dflags))
            then return (Failed (homeModError mod loc))
            else do {

        ; traceIf (ptext (sLit "readIFace") <+> text file_path)
        ; read_result <- readIface mod file_path hi_boot_file
        ; case read_result of
            Failed err -> return (Failed (badIfaceFile file_path err))
            Succeeded iface 
                | mi_module iface /= mod ->
                  return (Failed (wrongIfaceModErr iface mod file_path))
                | otherwise ->
                  return (Succeeded (iface, file_path))
                        -- Don't forget to fill in the package name...
        }}
            ; err -> do
                { traceIf (ptext (sLit "...not found"))
                ; dflags <- getDynFlags
                ; return (Failed (cannotFindInterface dflags 
                                        (moduleName mod) err)) }
        }
        }
\end{code}

@readIface@ tries just the one file.

\begin{code}
readIface :: Module -> FilePath -> IsBootInterface 
          -> 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
        ; case res of
            Right iface 
                | wanted_mod == actual_mod -> return (Succeeded iface)
                | otherwise                -> return (Failed err)
                where
                  actual_mod = mi_module iface
                  err = hiModuleNameMismatchWarn wanted_mod actual_mod

            Left exn    -> return (Failed (text (showException exn)))
    }
\end{code}


%*********************************************************
%*                                                       *
        Wired-in interface for GHC.Prim
%*                                                       *
%*********************************************************

\begin{code}
initExternalPackageState :: ExternalPackageState
initExternalPackageState
  = EPS { 
      eps_is_boot      = emptyUFM,
      eps_PIT          = emptyPackageIfaceTable,
      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 }
    }
\end{code}


%*********************************************************
%*                                                       *
        Wired-in interface for GHC.Prim
%*                                                       *
%*********************************************************

\begin{code}
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
\end{code}

%*********************************************************
%*                                                      *
\subsection{Statistics}
%*                                                      *
%*********************************************************

\begin{code}
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"]
        ]
\end{code}


%************************************************************************
%*                                                                      *
                Printing interfaces
%*                                                                      *
%************************************************************************

\begin{code}
-- | 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
   printDump (pprModIface iface)
\end{code}

\begin{code}
pprModIface :: ModIface -> SDoc
-- Show a ModIface
pprModIface iface
 = vcat [ ptext (sLit "interface")
                <+> ppr (mi_module iface) <+> pp_boot
                <+> (if mi_orphan iface then ptext (sLit "[orphan module]") else empty)
                <+> (if mi_finsts iface then ptext (sLit "[family instance module]") else empty)
                <+> (if mi_hpc    iface then ptext (sLit "[hpc]") else empty)
                <+> integer opt_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 "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 (map pprIfaceDecl (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_boot | mi_boot iface = ptext (sLit "[boot]")
            | otherwise     = empty
\end{code}

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

\begin{code}
pprExport :: IfaceExport -> SDoc
pprExport (Avail n)      = ppr n
pprExport (AvailTC _ []) = empty
pprExport (AvailTC n (n':ns)) 
  | n==n'     = ppr n <> pp_export ns
  | otherwise = ppr n <> char '|' <> pp_export (n':ns)
  where  
    pp_export []    = 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 $$
    nest 2 (
        maybe empty (\v -> text "exports: " <> ppr v) (usg_exports usage) $$
        vcat [ ppr n <+> ppr v | (n,v) <- usg_entities usage ]
        )
pprUsage usage@UsageFile{}
  = hsep [ptext (sLit "addDependentFile"),
          doubleQuotes (text (usg_file_path usage))]

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 empty)
    ppr_boot True  = text "[boot]"
    ppr_boot False = empty

pprIfaceDecl :: (Fingerprint, IfaceDecl) -> SDoc
pprIfaceDecl (ver, decl)
  = ppr ver $$ nest 2 (ppr decl)

pprFixities :: [(OccName, Fixity)] -> SDoc
pprFixities []    = 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
                           , ifaceVectInfoScalarVars   = scalarVars
                           , ifaceVectInfoScalarTyCons = scalarTyCons
                           }) = 
  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 "scalar variables:") <+> hsep (map ppr scalarVars)
  , ptext (sLit "scalar tycons:") <+> hsep (map ppr scalarTyCons)
  ]

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         = 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
\end{code}


%*********************************************************
%*                                                       *
\subsection{Errors}
%*                                                       *
%*********************************************************

\begin{code}
badIfaceFile :: String -> SDoc -> SDoc
badIfaceFile file err
  = vcat [ptext (sLit "Bad interface file:") <+> text file, 
          nest 4 err]

hiModuleNameMismatchWarn :: Module -> Module -> MsgDoc
hiModuleNameMismatchWarn requested_mod read_mod = 
  withPprStyle defaultUserStyle $
    -- 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
         ]

wrongIfaceModErr :: ModIface -> Module -> String -> SDoc
wrongIfaceModErr iface mod_name file_path 
  = sep [ptext (sLit "Interface file") <+> iface_file,
         ptext (sLit "contains module") <+> quotes (ppr (mi_module iface)) <> comma,
         ptext (sLit "but we were expecting module") <+> quotes (ppr mod_name),
         sep [ptext (sLit "Probable cause: the source code which generated"),
             nest 2 iface_file,
             ptext (sLit "has an incompatible module name")
            ]
        ]
  where iface_file = doubleQuotes (text file_path)

homeModError :: Module -> ModLocation -> SDoc
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   -> empty)
    <+> ptext (sLit "which is not loaded")
\end{code}