/compiler/iface/MkIface.lhs

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%
% (c) The University of Glasgow 2006-2008
% (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
%

\begin{code}
-- | Module for constructing @ModIface@ values (interface files),
-- writing them to disk and comparing two versions to see if
-- recompilation is required.
module MkIface ( 
        mkUsedNames,
        mkDependencies,
        mkIface,        -- Build a ModIface from a ModGuts, 
                        -- including computing version information

        mkIfaceTc,

        writeIfaceFile, -- Write the interface file

        checkOldIface,  -- See if recompilation is required, by
                        -- comparing version information
        RecompileRequired(..), recompileRequired,

        tyThingToIfaceDecl -- Converting things to their Iface equivalents
 ) where
\end{code}

  -----------------------------------------------
          Recompilation checking
  -----------------------------------------------

A complete description of how recompilation checking works can be
found in the wiki commentary:

 http://hackage.haskell.org/trac/ghc/wiki/Commentary/Compiler/RecompilationAvoidance

Please read the above page for a top-down description of how this all
works.  Notes below cover specific issues related to the implementation.

Basic idea: 

  * In the mi_usages information in an interface, we record the 
    fingerprint of each free variable of the module

  * In mkIface, we compute the fingerprint of each exported thing A.f.
    For each external thing that A.f refers to, we include the fingerprint
    of the external reference when computing the fingerprint of A.f.  So
    if anything that A.f depends on changes, then A.f's fingerprint will
    change.
    Also record any dependent files added with addDependentFile.
    In the future record any #include usages.

  * In checkOldIface we compare the mi_usages for the module with
    the actual fingerprint for all each thing recorded in mi_usages

\begin{code}
#include "HsVersions.h"

import IfaceSyn
import LoadIface
import FlagChecker

import Id
import IdInfo
import Demand
import Annotations
import CoreSyn
import CoreFVs
import Class
import Kind
import TyCon
import Coercion         ( coAxiomSplitLHS )
import DataCon
import Type
import TcType
import InstEnv
import FamInstEnv
import TcRnMonad
import HsSyn
import HscTypes
import Finder
import DynFlags
import VarEnv
import VarSet
import Var
import Name
import Avail
import RdrName
import NameEnv
import NameSet
import Module
import BinIface
import ErrUtils
import Digraph
import SrcLoc
import Outputable
import BasicTypes       hiding ( SuccessFlag(..) )
import UniqFM
import Unique
import Util             hiding ( eqListBy )
import FastString
import Maybes
import ListSetOps
import Binary
import Fingerprint
import Bag
import Exception

import Control.Monad
import Data.Function
import Data.List
import Data.Map (Map)
import qualified Data.Map as Map
import Data.Ord
import Data.IORef
import System.Directory
import System.FilePath
\end{code}



%************************************************************************
%*                                                                      *
\subsection{Completing an interface}
%*                                                                      *
%************************************************************************

\begin{code}
mkIface :: HscEnv
        -> Maybe Fingerprint    -- The old fingerprint, if we have it
        -> ModDetails           -- The trimmed, tidied interface
        -> ModGuts              -- Usages, deprecations, etc
        -> IO (Messages,
               Maybe (ModIface, -- The new one
                      Bool))    -- True <=> there was an old Iface, and the
                                --          new one is identical, so no need
                                --          to write it

mkIface hsc_env maybe_old_fingerprint mod_details
         ModGuts{     mg_module       = this_mod,
                      mg_boot         = is_boot,
                      mg_used_names   = used_names,
                      mg_used_th      = used_th,
                      mg_deps         = deps,
                      mg_dir_imps     = dir_imp_mods,
                      mg_rdr_env      = rdr_env,
                      mg_fix_env      = fix_env,
                      mg_warns        = warns,
                      mg_hpc_info     = hpc_info,
                      mg_safe_haskell = safe_mode,
                      mg_trust_pkg    = self_trust,
                      mg_dependent_files = dependent_files
                    }
        = mkIface_ hsc_env maybe_old_fingerprint
                   this_mod is_boot used_names used_th deps rdr_env fix_env
                   warns hpc_info dir_imp_mods self_trust dependent_files
                   safe_mode mod_details

-- | make an interface from the results of typechecking only.  Useful
-- for non-optimising compilation, or where we aren't generating any
-- object code at all ('HscNothing').
mkIfaceTc :: HscEnv
          -> Maybe Fingerprint  -- The old fingerprint, if we have it
          -> SafeHaskellMode    -- The safe haskell mode
          -> ModDetails         -- gotten from mkBootModDetails, probably
          -> TcGblEnv           -- Usages, deprecations, etc
          -> IO (Messages, Maybe (ModIface, Bool))
mkIfaceTc hsc_env maybe_old_fingerprint safe_mode mod_details
  tc_result@TcGblEnv{ tcg_mod = this_mod,
                      tcg_src = hsc_src,
                      tcg_imports = imports,
                      tcg_rdr_env = rdr_env,
                      tcg_fix_env = fix_env,
                      tcg_warns = warns,
                      tcg_hpc = other_hpc_info,
                      tcg_th_splice_used = tc_splice_used,
                      tcg_dependent_files = dependent_files
                    }
  = do
          let used_names = mkUsedNames tc_result
          deps <- mkDependencies tc_result
          let hpc_info = emptyHpcInfo other_hpc_info
          used_th <- readIORef tc_splice_used
          dep_files <- (readIORef dependent_files)
          mkIface_ hsc_env maybe_old_fingerprint
                   this_mod (isHsBoot hsc_src) used_names used_th deps rdr_env
                   fix_env warns hpc_info (imp_mods imports)
                   (imp_trust_own_pkg imports) dep_files safe_mode mod_details
        

mkUsedNames :: TcGblEnv -> NameSet
mkUsedNames TcGblEnv{ tcg_dus = dus } = allUses dus
        
-- | Extract information from the rename and typecheck phases to produce
-- a dependencies information for the module being compiled.
mkDependencies :: TcGblEnv -> IO Dependencies
mkDependencies
          TcGblEnv{ tcg_mod = mod,
                    tcg_imports = imports,
                    tcg_th_used = th_var
                  }
 = do 
      -- Template Haskell used?
      th_used <- readIORef th_var
      let dep_mods = eltsUFM (delFromUFM (imp_dep_mods imports) (moduleName mod))
                -- M.hi-boot can be in the imp_dep_mods, but we must remove
                -- it before recording the modules on which this one depends!
                -- (We want to retain M.hi-boot in imp_dep_mods so that 
                --  loadHiBootInterface can see if M's direct imports depend 
                --  on M.hi-boot, and hence that we should do the hi-boot consistency 
                --  check.)

          pkgs | th_used   = insertList thPackageId (imp_dep_pkgs imports)
               | otherwise = imp_dep_pkgs imports

          -- Set the packages required to be Safe according to Safe Haskell.
          -- See Note [RnNames . Tracking Trust Transitively]
          sorted_pkgs = sortBy stablePackageIdCmp pkgs
          trust_pkgs  = imp_trust_pkgs imports
          dep_pkgs'   = map (\x -> (x, x `elem` trust_pkgs)) sorted_pkgs

      return Deps { dep_mods   = sortBy (stableModuleNameCmp `on` fst) dep_mods,
                    dep_pkgs   = dep_pkgs',
                    dep_orphs  = sortBy stableModuleCmp (imp_orphs  imports),
                    dep_finsts = sortBy stableModuleCmp (imp_finsts imports) }
                    -- sort to get into canonical order
                    -- NB. remember to use lexicographic ordering

mkIface_ :: HscEnv -> Maybe Fingerprint -> Module -> IsBootInterface
         -> NameSet -> Bool -> Dependencies -> GlobalRdrEnv
         -> NameEnv FixItem -> Warnings -> HpcInfo
         -> ImportedMods -> Bool
         -> [FilePath]
         -> SafeHaskellMode
         -> ModDetails
         -> IO (Messages, Maybe (ModIface, Bool))
mkIface_ hsc_env maybe_old_fingerprint 
         this_mod is_boot used_names used_th deps rdr_env fix_env src_warns
         hpc_info dir_imp_mods pkg_trust_req dependent_files safe_mode
         ModDetails{  md_insts     = insts, 
                      md_fam_insts = fam_insts,
                      md_rules     = rules,
                      md_anns      = anns,
                      md_vect_info = vect_info,
                      md_types     = type_env,
                      md_exports   = exports }
-- NB:  notice that mkIface does not look at the bindings
--      only at the TypeEnv.  The previous Tidy phase has
--      put exactly the info into the TypeEnv that we want
--      to expose in the interface

  = do  { usages  <- mkUsageInfo hsc_env this_mod dir_imp_mods used_names dependent_files

        ; let   { entities = typeEnvElts type_env ;
                  decls  = [ tyThingToIfaceDecl entity
                           | entity <- entities,
                             let name = getName entity,
                             not (isImplicitTyThing entity),
                                -- No implicit Ids and class tycons in the interface file
                             not (isWiredInName name),
                                -- Nor wired-in things; the compiler knows about them anyhow
                             nameIsLocalOrFrom this_mod name  ]
                                -- Sigh: see Note [Root-main Id] in TcRnDriver

                ; fixities    = [(occ,fix) | FixItem occ fix <- nameEnvElts fix_env]
                ; warns       = src_warns
                ; iface_rules = map (coreRuleToIfaceRule this_mod) rules
                ; iface_insts = map instanceToIfaceInst insts
                ; iface_fam_insts = map famInstToIfaceFamInst fam_insts
                ; iface_vect_info = flattenVectInfo vect_info
                ; trust_info  = setSafeMode safe_mode

                ; intermediate_iface = ModIface { 
                        mi_module      = this_mod,
                        mi_boot        = is_boot,
                        mi_deps        = deps,
                        mi_usages      = usages,
                        mi_exports     = mkIfaceExports exports,
        
                        -- Sort these lexicographically, so that
                        -- the result is stable across compilations
                        mi_insts       = sortBy cmp_inst     iface_insts,
                        mi_fam_insts   = sortBy cmp_fam_inst iface_fam_insts,
                        mi_rules       = sortBy cmp_rule     iface_rules,

                        mi_vect_info   = iface_vect_info,

                        mi_fixities    = fixities,
                        mi_warns       = warns,
                        mi_anns        = mkIfaceAnnotations anns,
                        mi_globals     = maybeGlobalRdrEnv rdr_env,

                        -- Left out deliberately: filled in by addFingerprints
                        mi_iface_hash  = fingerprint0,
                        mi_mod_hash    = fingerprint0,
                        mi_flag_hash   = fingerprint0,
                        mi_exp_hash    = fingerprint0,
                        mi_used_th     = used_th,
                        mi_orphan_hash = fingerprint0,
                        mi_orphan      = False, -- Always set by addFingerprints, but
                                                -- it's a strict field, so we can't omit it.
                        mi_finsts      = False, -- Ditto
                        mi_decls       = deliberatelyOmitted "decls",
                        mi_hash_fn     = deliberatelyOmitted "hash_fn",
                        mi_hpc         = isHpcUsed hpc_info,
                        mi_trust       = trust_info,
                        mi_trust_pkg   = pkg_trust_req,

                        -- And build the cached values
                        mi_warn_fn     = mkIfaceWarnCache warns,
                        mi_fix_fn      = mkIfaceFixCache fixities }
                }

        ; (new_iface, no_change_at_all) 
                <- {-# SCC "versioninfo" #-}
                         addFingerprints hsc_env maybe_old_fingerprint
                                         intermediate_iface decls

                -- Warn about orphans
        ; let warn_orphs      = wopt Opt_WarnOrphans dflags
              warn_auto_orphs = wopt Opt_WarnAutoOrphans dflags
              orph_warnings   --- Laziness means no work done unless -fwarn-orphans
                | warn_orphs || warn_auto_orphs = rule_warns `unionBags` inst_warns
                | otherwise                     = emptyBag
              errs_and_warns = (orph_warnings, emptyBag)
              unqual = mkPrintUnqualified dflags rdr_env
              inst_warns = listToBag [ instOrphWarn dflags unqual d 
                                     | (d,i) <- insts `zip` iface_insts
                                     , isNothing (ifInstOrph i) ]
              rule_warns = listToBag [ ruleOrphWarn dflags unqual this_mod r 
                                     | r <- iface_rules
                                     , isNothing (ifRuleOrph r)
                                     , if ifRuleAuto r then warn_auto_orphs
                                                       else warn_orphs ]

        ; if errorsFound dflags errs_and_warns
            then return ( errs_and_warns, Nothing )
            else do {

                -- Debug printing
        ; dumpIfSet_dyn dflags Opt_D_dump_hi "FINAL INTERFACE" 
                        (pprModIface new_iface)

                -- bug #1617: on reload we weren't updating the PrintUnqualified
                -- correctly.  This stems from the fact that the interface had
                -- not changed, so addFingerprints returns the old ModIface
                -- with the old GlobalRdrEnv (mi_globals).
        ; let final_iface = new_iface{ mi_globals = maybeGlobalRdrEnv rdr_env }

        ; return (errs_and_warns, Just (final_iface, no_change_at_all)) }}
  where
     cmp_rule     = comparing ifRuleName
     -- Compare these lexicographically by OccName, *not* by unique,
     -- because the latter is not stable across compilations:
     cmp_inst     = comparing (nameOccName . ifDFun)
     cmp_fam_inst = comparing (nameOccName . ifFamInstTcName)

     dflags = hsc_dflags hsc_env

     -- We only fill in mi_globals if the module was compiled to byte
     -- code.  Otherwise, the compiler may not have retained all the
     -- top-level bindings and they won't be in the TypeEnv (see
     -- Desugar.addExportFlagsAndRules).  The mi_globals field is used
     -- by GHCi to decide whether the module has its full top-level
     -- scope available. (#5534)
     maybeGlobalRdrEnv :: GlobalRdrEnv -> Maybe GlobalRdrEnv
     maybeGlobalRdrEnv rdr_env
         | targetRetainsAllBindings (hscTarget dflags) = Just rdr_env
         | otherwise                                   = Nothing

     deliberatelyOmitted :: String -> a
     deliberatelyOmitted x = panic ("Deliberately omitted: " ++ x)

     ifFamInstTcName = ifFamInstFam

     flattenVectInfo (VectInfo { vectInfoVar          = vVar
                               , vectInfoTyCon        = vTyCon
                               , vectInfoScalarVars   = vScalarVars
                               , vectInfoScalarTyCons = vScalarTyCons
                               }) = 
       IfaceVectInfo
       { ifaceVectInfoVar          = [Var.varName v | (v, _  ) <- varEnvElts  vVar]
       , ifaceVectInfoTyCon        = [tyConName t   | (t, t_v) <- nameEnvElts vTyCon, t /= t_v]
       , ifaceVectInfoTyConReuse   = [tyConName t   | (t, t_v) <- nameEnvElts vTyCon, t == t_v]
       , ifaceVectInfoScalarVars   = [Var.varName v | v <- varSetElems vScalarVars]
       , ifaceVectInfoScalarTyCons = nameSetToList vScalarTyCons
       } 

-----------------------------
writeIfaceFile :: DynFlags -> ModLocation -> ModIface -> IO ()
writeIfaceFile dflags location new_iface
    = do createDirectoryIfMissing True (takeDirectory hi_file_path)
         writeBinIface dflags hi_file_path new_iface
    where hi_file_path = ml_hi_file location


-- -----------------------------------------------------------------------------
-- Look up parents and versions of Names

-- This is like a global version of the mi_hash_fn field in each ModIface.
-- Given a Name, it finds the ModIface, and then uses mi_hash_fn to get
-- the parent and version info.

mkHashFun
        :: HscEnv                       -- needed to look up versions
        -> ExternalPackageState         -- ditto
        -> (Name -> Fingerprint)
mkHashFun hsc_env eps
  = \name -> 
      let 
        mod = ASSERT2( isExternalName name, ppr name ) nameModule name
        occ = nameOccName name
        iface = lookupIfaceByModule (hsc_dflags hsc_env) hpt pit mod `orElse` 
                   pprPanic "lookupVers2" (ppr mod <+> ppr occ)
      in  
        snd (mi_hash_fn iface occ `orElse` 
                  pprPanic "lookupVers1" (ppr mod <+> ppr occ))
  where
      hpt = hsc_HPT hsc_env
      pit = eps_PIT eps

-- ---------------------------------------------------------------------------
-- Compute fingerprints for the interface

addFingerprints
        :: HscEnv
        -> Maybe Fingerprint -- the old fingerprint, if any
        -> ModIface          -- The new interface (lacking decls)
        -> [IfaceDecl]       -- The new decls
        -> IO (ModIface,     -- Updated interface
               Bool)         -- True <=> no changes at all; 
                             -- no need to write Iface

addFingerprints hsc_env mb_old_fingerprint iface0 new_decls
 = do
   eps <- hscEPS hsc_env
   let
        -- The ABI of a declaration represents everything that is made
        -- visible about the declaration that a client can depend on.
        -- see IfaceDeclABI below.
       declABI :: IfaceDecl -> IfaceDeclABI 
       declABI decl = (this_mod, decl, extras)
        where extras = declExtras fix_fn non_orph_rules non_orph_insts
                                  non_orph_fis decl

       edges :: [(IfaceDeclABI, Unique, [Unique])]
       edges = [ (abi, getUnique (ifName decl), out)
               | decl <- new_decls
               , let abi = declABI decl
               , let out = localOccs $ freeNamesDeclABI abi
               ]

       name_module n = ASSERT2( isExternalName n, ppr n ) nameModule n
       localOccs = map (getUnique . getParent . getOccName) 
                        . filter ((== this_mod) . name_module)
                        . nameSetToList
          where getParent occ = lookupOccEnv parent_map occ `orElse` occ

        -- maps OccNames to their parents in the current module.
        -- e.g. a reference to a constructor must be turned into a reference
        -- to the TyCon for the purposes of calculating dependencies.
       parent_map :: OccEnv OccName
       parent_map = foldr extend emptyOccEnv new_decls
          where extend d env = 
                  extendOccEnvList env [ (b,n) | b <- ifaceDeclImplicitBndrs d ]
                  where n = ifName d

        -- strongly-connected groups of declarations, in dependency order
       groups = stronglyConnCompFromEdgedVertices edges

       global_hash_fn = mkHashFun hsc_env eps

        -- how to output Names when generating the data to fingerprint.
        -- Here we want to output the fingerprint for each top-level
        -- Name, whether it comes from the current module or another
        -- module.  In this way, the fingerprint for a declaration will
        -- change if the fingerprint for anything it refers to (transitively)
        -- changes.
       mk_put_name :: (OccEnv (OccName,Fingerprint))
                   -> BinHandle -> Name -> IO  ()
       mk_put_name local_env bh name
          | isWiredInName name  =  putNameLiterally bh name 
           -- wired-in names don't have fingerprints
          | otherwise
          = ASSERT2( isExternalName name, ppr name )
            let hash | nameModule name /= this_mod =  global_hash_fn name
                     | otherwise = snd (lookupOccEnv local_env (getOccName name)
                           `orElse` pprPanic "urk! lookup local fingerprint" 
                                       (ppr name)) -- (undefined,fingerprint0))
                -- This panic indicates that we got the dependency
                -- analysis wrong, because we needed a fingerprint for
                -- an entity that wasn't in the environment.  To debug
                -- it, turn the panic into a trace, uncomment the
                -- pprTraces below, run the compile again, and inspect
                -- the output and the generated .hi file with
                -- --show-iface.
            in put_ bh hash

        -- take a strongly-connected group of declarations and compute
        -- its fingerprint.

       fingerprint_group :: (OccEnv (OccName,Fingerprint), 
                             [(Fingerprint,IfaceDecl)])
                         -> SCC IfaceDeclABI
                         -> IO (OccEnv (OccName,Fingerprint), 
                                [(Fingerprint,IfaceDecl)])

       fingerprint_group (local_env, decls_w_hashes) (AcyclicSCC abi)
          = do let hash_fn = mk_put_name local_env
                   decl = abiDecl abi
               -- pprTrace "fingerprinting" (ppr (ifName decl) ) $ do
               hash <- computeFingerprint hash_fn abi
               env' <- extend_hash_env local_env (hash,decl)
               return (env', (hash,decl) : decls_w_hashes)

       fingerprint_group (local_env, decls_w_hashes) (CyclicSCC abis)
          = do let decls = map abiDecl abis
               local_env1 <- foldM extend_hash_env local_env
                                   (zip (repeat fingerprint0) decls)
               let hash_fn = mk_put_name local_env1
               -- pprTrace "fingerprinting" (ppr (map ifName decls) ) $ do
               let stable_abis = sortBy cmp_abiNames abis
                -- put the cycle in a canonical order
               hash <- computeFingerprint hash_fn stable_abis
               let pairs = zip (repeat hash) decls
               local_env2 <- foldM extend_hash_env local_env pairs
               return (local_env2, pairs ++ decls_w_hashes)

       -- we have fingerprinted the whole declaration, but we now need
       -- to assign fingerprints to all the OccNames that it binds, to
       -- use when referencing those OccNames in later declarations.
       --
       extend_hash_env :: OccEnv (OccName,Fingerprint)
                       -> (Fingerprint,IfaceDecl)
                       -> IO (OccEnv (OccName,Fingerprint))
       extend_hash_env env0 (hash,d) = do
          return (foldr (\(b,fp) env -> extendOccEnv env b (b,fp)) env0
                 (ifaceDeclFingerprints hash d))

   --
   (local_env, decls_w_hashes) <- 
       foldM fingerprint_group (emptyOccEnv, []) groups

   -- when calculating fingerprints, we always need to use canonical
   -- ordering for lists of things.  In particular, the mi_deps has various
   -- lists of modules and suchlike, so put these all in canonical order:
   let sorted_deps = sortDependencies (mi_deps iface0)

   -- the export hash of a module depends on the orphan hashes of the
   -- orphan modules below us in the dependency tree.  This is the way
   -- that changes in orphans get propagated all the way up the
   -- dependency tree.  We only care about orphan modules in the current
   -- package, because changes to orphans outside this package will be
   -- tracked by the usage on the ABI hash of package modules that we import.
   let orph_mods = filter ((== this_pkg) . modulePackageId)
                   $ dep_orphs sorted_deps
   dep_orphan_hashes <- getOrphanHashes hsc_env orph_mods

   orphan_hash <- computeFingerprint (mk_put_name local_env)
                      (map ifDFun orph_insts, orph_rules, orph_fis)

   -- the export list hash doesn't depend on the fingerprints of
   -- the Names it mentions, only the Names themselves, hence putNameLiterally.
   export_hash <- computeFingerprint putNameLiterally
                      (mi_exports iface0,
                       orphan_hash,
                       dep_orphan_hashes,
                       dep_pkgs (mi_deps iface0),
                        -- dep_pkgs: see "Package Version Changes" on
                        -- wiki/Commentary/Compiler/RecompilationAvoidance
                       mi_trust iface0)
                        -- Make sure change of Safe Haskell mode causes recomp.

   -- put the declarations in a canonical order, sorted by OccName
   let sorted_decls = Map.elems $ Map.fromList $
                          [(ifName d, e) | e@(_, d) <- decls_w_hashes]
   
   -- the flag hash depends on:
   --   - (some of) dflags
   -- it returns two hashes, one that shouldn't change
   -- the abi hash and one that should
   flag_hash <- fingerprintDynFlags dflags this_mod putNameLiterally

   -- the ABI hash depends on:
   --   - decls
   --   - export list
   --   - orphans
   --   - deprecations
   --   - vect info
   --   - flag abi hash
   mod_hash <- computeFingerprint putNameLiterally
                      (map fst sorted_decls,
                       export_hash,  -- includes orphan_hash
                       mi_warns iface0,
                       mi_vect_info iface0)

   -- The interface hash depends on:
   --   - the ABI hash, plus
   --   - usages
   --   - deps
   --   - hpc
   iface_hash <- computeFingerprint putNameLiterally
                      (mod_hash, 
                       mi_usages iface0,
                       sorted_deps,
                       mi_hpc iface0)

   let
    no_change_at_all = Just iface_hash == mb_old_fingerprint

    final_iface = iface0 {
                mi_mod_hash    = mod_hash,
                mi_iface_hash  = iface_hash,
                mi_exp_hash    = export_hash,
                mi_orphan_hash = orphan_hash,
                mi_flag_hash   = flag_hash,
                mi_orphan      = not (   null orph_rules
                                      && null orph_insts
                                      && null orph_fis
                                      && isNoIfaceVectInfo (mi_vect_info iface0)),
                mi_finsts      = not . null $ mi_fam_insts iface0,
                mi_decls       = sorted_decls,
                mi_hash_fn     = lookupOccEnv local_env }
   --
   return (final_iface, no_change_at_all)

  where
    this_mod = mi_module iface0
    dflags = hsc_dflags hsc_env
    this_pkg = thisPackage dflags
    (non_orph_insts, orph_insts) = mkOrphMap ifInstOrph    (mi_insts iface0)
    (non_orph_rules, orph_rules) = mkOrphMap ifRuleOrph    (mi_rules iface0)
    (non_orph_fis,   orph_fis)   = mkOrphMap ifFamInstOrph (mi_fam_insts iface0)
    fix_fn = mi_fix_fn iface0


getOrphanHashes :: HscEnv -> [Module] -> IO [Fingerprint]
getOrphanHashes hsc_env mods = do
  eps <- hscEPS hsc_env
  let 
    hpt        = hsc_HPT hsc_env
    pit        = eps_PIT eps
    dflags     = hsc_dflags hsc_env
    get_orph_hash mod = 
          case lookupIfaceByModule dflags hpt pit mod of
            Nothing    -> pprPanic "moduleOrphanHash" (ppr mod)
            Just iface -> mi_orphan_hash iface
  --
  return (map get_orph_hash mods)


sortDependencies :: Dependencies -> Dependencies
sortDependencies d
 = Deps { dep_mods   = sortBy (compare `on` (moduleNameFS.fst)) (dep_mods d),
          dep_pkgs   = sortBy (stablePackageIdCmp `on` fst) (dep_pkgs d),
          dep_orphs  = sortBy stableModuleCmp (dep_orphs d),
          dep_finsts = sortBy stableModuleCmp (dep_finsts d) }
\end{code}


%************************************************************************
%*                                                                      *
          The ABI of an IfaceDecl                                                                               
%*                                                                      *
%************************************************************************

Note [The ABI of an IfaceDecl]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The ABI of a declaration consists of:

   (a) the full name of the identifier (inc. module and package,
       because these are used to construct the symbol name by which
       the identifier is known externally).

   (b) the declaration itself, as exposed to clients.  That is, the
       definition of an Id is included in the fingerprint only if
       it is made available as as unfolding in the interface.

   (c) the fixity of the identifier
   (d) for Ids: rules
   (e) for classes: instances, fixity & rules for methods
   (f) for datatypes: instances, fixity & rules for constrs

Items (c)-(f) are not stored in the IfaceDecl, but instead appear
elsewhere in the interface file.  But they are *fingerprinted* with
the declaration itself. This is done by grouping (c)-(f) in IfaceDeclExtras,
and fingerprinting that as part of the declaration.

\begin{code}
type IfaceDeclABI = (Module, IfaceDecl, IfaceDeclExtras)

data IfaceDeclExtras 
  = IfaceIdExtras    Fixity [IfaceRule]

  | IfaceDataExtras  
       Fixity                   -- Fixity of the tycon itself
       [IfaceInstABI]           -- Local class and family instances of this tycon
                                -- See Note [Orphans] in IfaceSyn
       [(Fixity,[IfaceRule])]   -- For each construcotr, fixity and RULES

  | IfaceClassExtras 
       Fixity                   -- Fixity of the class itself
       [IfaceInstABI]           -- Local instances of this class *or*
                                --   of its associated data types
                                -- See Note [Orphans] in IfaceSyn
       [(Fixity,[IfaceRule])]   -- For each class method, fixity and RULES

  | IfaceSynExtras   Fixity [IfaceInstABI]

  | IfaceOtherDeclExtras

-- When hashing a class or family instance, we hash only the 
-- DFunId or CoAxiom, because that depends on all the 
-- information about the instance.
--
type IfaceInstABI = IfExtName   -- Name of DFunId or CoAxiom that is evidence for the instance

abiDecl :: IfaceDeclABI -> IfaceDecl
abiDecl (_, decl, _) = decl

cmp_abiNames :: IfaceDeclABI -> IfaceDeclABI -> Ordering
cmp_abiNames abi1 abi2 = ifName (abiDecl abi1) `compare` 
                         ifName (abiDecl abi2)

freeNamesDeclABI :: IfaceDeclABI -> NameSet
freeNamesDeclABI (_mod, decl, extras) =
  freeNamesIfDecl decl `unionNameSets` freeNamesDeclExtras extras

freeNamesDeclExtras :: IfaceDeclExtras -> NameSet
freeNamesDeclExtras (IfaceIdExtras    _ rules)
  = unionManyNameSets (map freeNamesIfRule rules)
freeNamesDeclExtras (IfaceDataExtras  _ insts subs)
  = unionManyNameSets (mkNameSet insts : map freeNamesSub subs)
freeNamesDeclExtras (IfaceClassExtras _ insts subs)
  = unionManyNameSets (mkNameSet insts : map freeNamesSub subs)
freeNamesDeclExtras (IfaceSynExtras _ insts)
  = mkNameSet insts
freeNamesDeclExtras IfaceOtherDeclExtras
  = emptyNameSet

freeNamesSub :: (Fixity,[IfaceRule]) -> NameSet
freeNamesSub (_,rules) = unionManyNameSets (map freeNamesIfRule rules)

instance Outputable IfaceDeclExtras where
  ppr IfaceOtherDeclExtras       = empty
  ppr (IfaceIdExtras  fix rules) = ppr_id_extras fix rules
  ppr (IfaceSynExtras fix finsts) = vcat [ppr fix, ppr finsts]
  ppr (IfaceDataExtras fix insts stuff) = vcat [ppr fix, ppr_insts insts,
                                                ppr_id_extras_s stuff]
  ppr (IfaceClassExtras fix insts stuff) = vcat [ppr fix, ppr_insts insts,
                                                 ppr_id_extras_s stuff]

ppr_insts :: [IfaceInstABI] -> SDoc
ppr_insts _ = ptext (sLit "<insts>")

ppr_id_extras_s :: [(Fixity, [IfaceRule])] -> SDoc
ppr_id_extras_s stuff = vcat [ppr_id_extras f r | (f,r)<- stuff]

ppr_id_extras :: Fixity -> [IfaceRule] -> SDoc
ppr_id_extras fix rules = ppr fix $$ vcat (map ppr rules)

-- This instance is used only to compute fingerprints
instance Binary IfaceDeclExtras where
  get _bh = panic "no get for IfaceDeclExtras"
  put_ bh (IfaceIdExtras fix rules) = do
   putByte bh 1; put_ bh fix; put_ bh rules
  put_ bh (IfaceDataExtras fix insts cons) = do
   putByte bh 2; put_ bh fix; put_ bh insts; put_ bh cons
  put_ bh (IfaceClassExtras fix insts methods) = do
   putByte bh 3; put_ bh fix; put_ bh insts; put_ bh methods
  put_ bh (IfaceSynExtras fix finsts) = do
   putByte bh 4; put_ bh fix; put_ bh finsts
  put_ bh IfaceOtherDeclExtras = do
   putByte bh 5

declExtras :: (OccName -> Fixity)
           -> OccEnv [IfaceRule]
           -> OccEnv [IfaceClsInst]
           -> OccEnv [IfaceFamInst]
           -> IfaceDecl
           -> IfaceDeclExtras

declExtras fix_fn rule_env inst_env fi_env decl
  = case decl of
      IfaceId{} -> IfaceIdExtras (fix_fn n) 
                        (lookupOccEnvL rule_env n)
      IfaceData{ifCons=cons} -> 
                     IfaceDataExtras (fix_fn n)
                        (map ifFamInstAxiom (lookupOccEnvL fi_env n) ++
                         map ifDFun         (lookupOccEnvL inst_env n))
                        (map (id_extras . ifConOcc) (visibleIfConDecls cons))
      IfaceClass{ifSigs=sigs, ifATs=ats} -> 
                     IfaceClassExtras (fix_fn n)
                        (map ifDFun $ (concatMap at_extras ats)
                                    ++ lookupOccEnvL inst_env n)
                           -- Include instances of the associated types
                           -- as well as instances of the class (Trac #5147)
                        [id_extras op | IfaceClassOp op _ _ <- sigs]
      IfaceSyn{} -> IfaceSynExtras (fix_fn n) 
                        (map ifFamInstAxiom (lookupOccEnvL fi_env n))
      _other -> IfaceOtherDeclExtras
  where
        n = ifName decl
        id_extras occ = (fix_fn occ, lookupOccEnvL rule_env occ)
        at_extras (IfaceAT decl _) = lookupOccEnvL inst_env (ifName decl)


lookupOccEnvL :: OccEnv [v] -> OccName -> [v]
lookupOccEnvL env k = lookupOccEnv env k `orElse` []

-- used when we want to fingerprint a structure without depending on the
-- fingerprints of external Names that it refers to.
putNameLiterally :: BinHandle -> Name -> IO ()
putNameLiterally bh name = ASSERT( isExternalName name ) 
  do { put_ bh $! nameModule name
     ; put_ bh $! nameOccName name }

{-
-- for testing: use the md5sum command to generate fingerprints and
-- compare the results against our built-in version.
  fp' <- oldMD5 dflags bh
  if fp /= fp' then pprPanic "computeFingerprint" (ppr fp <+> ppr fp')
               else return fp

oldMD5 dflags bh = do
  tmp <- newTempName dflags "bin"
  writeBinMem bh tmp
  tmp2 <- newTempName dflags "md5"
  let cmd = "md5sum " ++ tmp ++ " >" ++ tmp2
  r <- system cmd
  case r of
    ExitFailure _ -> ghcError (PhaseFailed cmd r)
    ExitSuccess -> do
        hash_str <- readFile tmp2
        return $! readHexFingerprint hash_str
-}

instOrphWarn :: DynFlags -> PrintUnqualified -> ClsInst -> WarnMsg
instOrphWarn dflags unqual inst
  = mkWarnMsg dflags (getSrcSpan inst) unqual $
    hang (ptext (sLit "Orphan instance:")) 2 (pprInstanceHdr inst)

ruleOrphWarn :: DynFlags -> PrintUnqualified -> Module -> IfaceRule -> WarnMsg
ruleOrphWarn dflags unqual mod rule
  = mkWarnMsg dflags silly_loc unqual $
    ptext (sLit "Orphan rule:") <+> ppr rule
  where
    silly_loc = srcLocSpan (mkSrcLoc (moduleNameFS (moduleName mod)) 1 1)
    -- We don't have a decent SrcSpan for a Rule, not even the CoreRule
    -- Could readily be fixed by adding a SrcSpan to CoreRule, if we wanted to

----------------------
-- mkOrphMap partitions instance decls or rules into
--      (a) an OccEnv for ones that are not orphans, 
--          mapping the local OccName to a list of its decls
--      (b) a list of orphan decls
mkOrphMap :: (decl -> Maybe OccName)    -- (Just occ) for a non-orphan decl, keyed by occ
                                        -- Nothing for an orphan decl
          -> [decl]                     -- Sorted into canonical order
          -> (OccEnv [decl],            -- Non-orphan decls associated with their key;
                                        --      each sublist in canonical order
              [decl])                   -- Orphan decls; in canonical order
mkOrphMap get_key decls
  = foldl go (emptyOccEnv, []) decls
  where
    go (non_orphs, orphs) d
        | Just occ <- get_key d
        = (extendOccEnv_Acc (:) singleton non_orphs occ d, orphs)
        | otherwise = (non_orphs, d:orphs)
\end{code}


%************************************************************************
%*                                                                      *
       Keeping track of what we've slurped, and fingerprints
%*                                                                      *
%************************************************************************

\begin{code}
mkUsageInfo :: HscEnv -> Module -> ImportedMods -> NameSet -> [FilePath] -> IO [Usage]
mkUsageInfo hsc_env this_mod dir_imp_mods used_names dependent_files
  = do  { eps <- hscEPS hsc_env
    ; mtimes <- mapM getModificationUTCTime dependent_files
        ; let mod_usages = mk_mod_usage_info (eps_PIT eps) hsc_env this_mod
                                     dir_imp_mods used_names
        ; let usages = mod_usages ++ map to_file_usage (zip dependent_files mtimes)
        ; usages `seqList`  return usages }
         -- seq the list of Usages returned: occasionally these
         -- don't get evaluated for a while and we can end up hanging on to
         -- the entire collection of Ifaces.
   where
     to_file_usage (f, mtime) = UsageFile { usg_file_path = f, usg_mtime = mtime }

mk_mod_usage_info :: PackageIfaceTable
              -> HscEnv
              -> Module
              -> ImportedMods
              -> NameSet
              -> [Usage]
mk_mod_usage_info pit hsc_env this_mod direct_imports used_names
  = mapCatMaybes mkUsage usage_mods
  where
    hpt = hsc_HPT hsc_env
    dflags = hsc_dflags hsc_env
    this_pkg = thisPackage dflags

    used_mods    = moduleEnvKeys ent_map
    dir_imp_mods = moduleEnvKeys direct_imports
    all_mods     = used_mods ++ filter (`notElem` used_mods) dir_imp_mods
    usage_mods   = sortBy stableModuleCmp all_mods
                        -- canonical order is imported, to avoid interface-file
                        -- wobblage.

    -- ent_map groups together all the things imported and used
    -- from a particular module
    ent_map :: ModuleEnv [OccName]
    ent_map  = foldNameSet add_mv emptyModuleEnv used_names
     where
      add_mv name mv_map
        | isWiredInName name = mv_map  -- ignore wired-in names
        | otherwise
        = case nameModule_maybe name of
             Nothing  -> ASSERT2( isSystemName name, ppr name ) mv_map
                -- See Note [Internal used_names]

             Just mod -> -- This lambda function is really just a
                         -- specialised (++); originally came about to
                         -- avoid quadratic behaviour (trac #2680)
                         extendModuleEnvWith (\_ xs -> occ:xs) mv_map mod [occ]
                where occ = nameOccName name
    
    -- We want to create a Usage for a home module if 
    --  a) we used something from it; has something in used_names
    --  b) we imported it, even if we used nothing from it
    --     (need to recompile if its export list changes: export_fprint)
    mkUsage :: Module -> Maybe Usage
    mkUsage mod
      | isNothing maybe_iface           -- We can't depend on it if we didn't
                                        -- load its interface.
      || mod == this_mod                -- We don't care about usages of
                                        -- things in *this* module
      = Nothing

      | modulePackageId mod /= this_pkg
      = Just UsagePackageModule{ usg_mod      = mod,
                                 usg_mod_hash = mod_hash,
                                 usg_safe     = imp_safe }
        -- for package modules, we record the module hash only

      | (null used_occs
          && isNothing export_hash
          && not is_direct_import
          && not finsts_mod)
      = Nothing                 -- Record no usage info
        -- for directly-imported modules, we always want to record a usage
        -- on the orphan hash.  This is what triggers a recompilation if
        -- an orphan is added or removed somewhere below us in the future.
    
      | otherwise       
      = Just UsageHomeModule { 
                      usg_mod_name = moduleName mod,
                      usg_mod_hash = mod_hash,
                      usg_exports  = export_hash,
                      usg_entities = Map.toList ent_hashs,
                      usg_safe     = imp_safe }
      where
        maybe_iface  = lookupIfaceByModule dflags hpt pit mod
                -- In one-shot mode, the interfaces for home-package
                -- modules accumulate in the PIT not HPT.  Sigh.

        Just iface   = maybe_iface
        finsts_mod   = mi_finsts    iface
        hash_env     = mi_hash_fn   iface
        mod_hash     = mi_mod_hash  iface
        export_hash | depend_on_exports = Just (mi_exp_hash iface)
                    | otherwise         = Nothing

        (is_direct_import, imp_safe)
            = case lookupModuleEnv direct_imports mod of
                Just ((_,_,_,safe):_xs) -> (True, safe)
                Just _                  -> pprPanic "mkUsage: empty direct import" empty
                Nothing                 -> (False, safeImplicitImpsReq dflags)
                -- Nothing case is for implicit imports like 'System.IO' when 'putStrLn'
                -- is used in the source code. We require them to be safe in Safe Haskell
    
        used_occs = lookupModuleEnv ent_map mod `orElse` []

        -- Making a Map here ensures that (a) we remove duplicates
        -- when we have usages on several subordinates of a single parent,
        -- and (b) that the usages emerge in a canonical order, which
        -- is why we use Map rather than OccEnv: Map works
        -- using Ord on the OccNames, which is a lexicographic ordering.
        ent_hashs :: Map OccName Fingerprint
        ent_hashs = Map.fromList (map lookup_occ used_occs)
        
        lookup_occ occ = 
            case hash_env occ of
                Nothing -> pprPanic "mkUsage" (ppr mod <+> ppr occ <+> ppr used_names)
                Just r  -> r

        depend_on_exports = is_direct_import
        {- True
              Even if we used 'import M ()', we have to register a
              usage on the export list because we are sensitive to
              changes in orphan instances/rules.
           False
              In GHC 6.8.x we always returned true, and in
              fact it recorded a dependency on *all* the
              modules underneath in the dependency tree.  This
              happens to make orphans work right, but is too
              expensive: it'll read too many interface files.
              The 'isNothing maybe_iface' check above saved us
              from generating many of these usages (at least in
              one-shot mode), but that's even more bogus!
        -}
\end{code}

\begin{code}
mkIfaceAnnotations :: [Annotation] -> [IfaceAnnotation]
mkIfaceAnnotations = map mkIfaceAnnotation

mkIfaceAnnotation :: Annotation -> IfaceAnnotation
mkIfaceAnnotation (Annotation { ann_target = target, ann_value = serialized }) = IfaceAnnotation { 
        ifAnnotatedTarget = fmap nameOccName target,
        ifAnnotatedValue = serialized
    }
\end{code}

\begin{code}
mkIfaceExports :: [AvailInfo] -> [IfaceExport]  -- Sort to make canonical
mkIfaceExports exports
  = sortBy stableAvailCmp (map sort_subs exports)
  where
    sort_subs :: AvailInfo -> AvailInfo
    sort_subs (Avail n) = Avail n
    sort_subs (AvailTC n []) = AvailTC n []
    sort_subs (AvailTC n (m:ms)) 
       | n==m      = AvailTC n (m:sortBy stableNameCmp ms)
       | otherwise = AvailTC n (sortBy stableNameCmp (m:ms))
       -- Maintain the AvailTC Invariant
\end{code}

Note [Orignal module]
~~~~~~~~~~~~~~~~~~~~~
Consider this:
        module X where { data family T }
        module Y( T(..) ) where { import X; data instance T Int = MkT Int }
The exported Avail from Y will look like
        X.T{X.T, Y.MkT}
That is, in Y, 
  - only MkT is brought into scope by the data instance;
  - but the parent (used for grouping and naming in T(..) exports) is X.T
  - and in this case we export X.T too

In the result of MkIfaceExports, the names are grouped by defining module,
so we may need to split up a single Avail into multiple ones.

Note [Internal used_names]
~~~~~~~~~~~~~~~~~~~~~~~~~~
Most of the used_names are External Names, but we can have Internal
Names too: see Note [Binders in Template Haskell] in Convert, and
Trac #5362 for an example.  Such Names are always
  - Such Names are always for locally-defined things, for which we
    don't gather usage info, so we can just ignore them in ent_map
  - They are always System Names, hence the assert, just as a double check.


%************************************************************************
%*                                                                      *
        Load the old interface file for this module (unless
        we have it already), and check whether it is up to date
%*                                                                      *
%************************************************************************

\begin{code}
data RecompileRequired
  = UpToDate
       -- ^ everything is up to date, recompilation is not required
  | MustCompile
       -- ^ The .hs file has been touched, or the .o/.hi file does not exist
  | RecompBecause String
       -- ^ The .o/.hi files are up to date, but something else has changed
       -- to force recompilation; the String says what (one-line summary)
   deriving Eq

recompileRequired :: RecompileRequired -> Bool
recompileRequired UpToDate = False
recompileRequired _ = True



-- | Top level function to check if the version of an old interface file
-- is equivalent to the current source file the user asked us to compile.
-- If the same, we can avoid recompilation. We return a tuple where the
-- first element is a bool saying if we should recompile the object file
-- and the second is maybe the interface file, where Nothng means to
-- rebuild the interface file not use the exisitng one.
checkOldIface :: HscEnv
              -> ModSummary
              -> SourceModified
              -> Maybe ModIface         -- Old interface from compilation manager, if any
              -> IO (RecompileRequired, Maybe ModIface)

checkOldIface hsc_env mod_summary source_modified maybe_iface
  = do  let dflags = hsc_dflags hsc_env
        showPass dflags $
            "Checking old interface for " ++ (showPpr dflags $ ms_mod mod_summary)
        initIfaceCheck hsc_env $
            check_old_iface hsc_env mod_summary source_modified maybe_iface

check_old_iface :: HscEnv -> ModSummary -> SourceModified -> Maybe ModIface
                -> IfG (RecompileRequired, Maybe ModIface)
check_old_iface hsc_env mod_summary src_modified maybe_iface
  = let dflags = hsc_dflags hsc_env
        getIface =
            case maybe_iface of
                Just _  -> do
                    traceIf (text "We already have the old interface for" <+> ppr (ms_mod mod_summary))
                    return maybe_iface
                Nothing -> loadIface

        loadIface = do
             let iface_path = msHiFilePath mod_summary
             read_result <- readIface (ms_mod mod_summary) iface_path False
             case read_result of
                 Failed err -> do
                     traceIf (text "FYI: cannont read old interface file:" $$ nest 4 err)
                     return Nothing
                 Succeeded iface -> do
                     traceIf (text "Read the interface file" <+> text iface_path)
                     return $ Just iface

        src_changed
            | dopt Opt_ForceRecomp (hsc_dflags hsc_env) = True
            | SourceModified <- src_modified = True
            | otherwise = False
    in do
        when src_changed $
            traceHiDiffs (nest 4 $ text "Source file changed or recompilation check turned off")

        case src_changed of
            -- If the source has changed and we're in interactive mode,
            -- avoid reading an interface; just return the one we might
            -- have been supplied with.
            True | not (isObjectTarget $ hscTarget dflags) ->
                return (MustCompile, maybe_iface)

            -- Try and read the old interface for the current module
            -- from the .hi file left from the last time we compiled it
            True -> do
                maybe_iface' <- getIface
                return (MustCompile, maybe_iface')

            False -> do
                maybe_iface' <- getIface
                case maybe_iface' of
                    -- We can't retrieve the iface
                    Nothing    -> return (MustCompile, Nothing)

                    -- We have got the old iface; check its versions
                    -- even in the SourceUnmodifiedAndStable case we
                    -- should check versions because some packages
                    -- might have changed or gone away.
          …