/compiler/iface/MkIface.hs

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

{-# LANGUAGE CPP, NondecreasingIndentation #-}

-- | Module for constructing @ModIface@ values (interface files),
-- writing them to disk and comparing two versions to see if
-- recompilation is required.
module MkIface (
        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

{-
  -----------------------------------------------
          Recompilation checking
  -----------------------------------------------

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

 http://ghc.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
      * #include
      * -optP-include

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

#include "HsVersions.h"

import IfaceSyn
import LoadIface
import FlagChecker

import Desugar ( mkUsageInfo, mkUsedNames, mkDependencies )
import Id
import IdInfo
import Demand
import Coercion( tidyCo )
import Annotations
import CoreSyn
import Class
import TyCon
import CoAxiom
import ConLike
import DataCon
import PatSyn
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 Unique
import Util             hiding ( eqListBy )
import FastString
import FastStringEnv
import Maybes
import Binary
import Fingerprint
import Exception
import UniqFM
import UniqDFM

import Control.Monad
import Data.Function
import Data.List
import qualified Data.Map as Map
import Data.Ord
import Data.IORef
import System.Directory
import System.FilePath

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

mkIface :: HscEnv
        -> Maybe Fingerprint    -- The old fingerprint, if we have it
        -> ModDetails           -- The trimmed, tidied interface
        -> ModGuts              -- Usages, deprecations, etc
        -> IO (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_hsc_src      = hsc_src,
                      mg_usages       = usages,
                      mg_used_th      = used_th,
                      mg_deps         = deps,
                      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
                    }
        = mkIface_ hsc_env maybe_old_fingerprint
                   this_mod hsc_src used_th deps rdr_env fix_env
                   warns hpc_info self_trust
                   safe_mode usages 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 (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)
          usages <- mkUsageInfo hsc_env this_mod (imp_mods imports) used_names dep_files
          mkIface_ hsc_env maybe_old_fingerprint
                   this_mod hsc_src
                   used_th deps rdr_env
                   fix_env warns hpc_info
                   (imp_trust_own_pkg imports) safe_mode usages mod_details


mkIface_ :: HscEnv -> Maybe Fingerprint -> Module -> HscSource
         -> Bool -> Dependencies -> GlobalRdrEnv
         -> NameEnv FixItem -> Warnings -> HpcInfo
         -> Bool
         -> SafeHaskellMode
         -> [Usage]
         -> ModDetails
         -> IO (ModIface, Bool)
mkIface_ hsc_env maybe_old_fingerprint
         this_mod hsc_src used_th deps rdr_env fix_env src_warns
         hpc_info pkg_trust_req safe_mode usages
         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
    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    = sortBy (comparing fst)
          [(occ,fix) | FixItem occ fix <- nameEnvElts fix_env]
          -- The order of fixities returned from nameEnvElts is not
          -- deterministic, so we sort by OccName to canonicalize it.
          -- See Note [Deterministic UniqFM] in UniqDFM for more details.
        warns       = src_warns
        iface_rules = map coreRuleToIfaceRule rules
        iface_insts = map instanceToIfaceInst $ fixSafeInstances safe_mode insts
        iface_fam_insts = map famInstToIfaceFamInst fam_insts
        iface_vect_info = flattenVectInfo vect_info
        trust_info  = setSafeMode safe_mode
        annotations = map mkIfaceAnnotation anns
        sig_of = getSigOf dflags (moduleName this_mod)

        intermediate_iface = ModIface {
              mi_module      = this_mod,
              mi_sig_of      = sig_of,
              mi_hsc_src     = hsc_src,
              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        = annotations,
              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

    -- 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 (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
                               , vectInfoParallelVars     = vParallelVars
                               , vectInfoParallelTyCons = vParallelTyCons
                               }) =
       IfaceVectInfo
       { ifaceVectInfoVar            = [Var.varName v | (v, _  ) <- dVarEnvElts vVar]
       , ifaceVectInfoTyCon          = [tyConName t   | (t, t_v) <- nameEnvElts vTyCon, t /= t_v]
       , ifaceVectInfoTyConReuse     = [tyConName t   | (t, t_v) <- nameEnvElts vTyCon, t == t_v]
       , ifaceVectInfoParallelVars   = [Var.varName v | v <- dVarSetElems vParallelVars]
       , ifaceVectInfoParallelTyCons = nameSetElemsStable vParallelTyCons
       }

-----------------------------
writeIfaceFile :: DynFlags -> FilePath -> ModIface -> IO ()
writeIfaceFile dflags hi_file_path new_iface
    = do createDirectoryIfMissing True (takeDirectory hi_file_path)
         writeBinIface dflags hi_file_path new_iface


-- -----------------------------------------------------------------------------
-- 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 dflags 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
      dflags = hsc_dflags hsc_env
      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 ann_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)
                        . nonDetEltsUFM
                   -- It's OK to use nonDetEltsUFM as localOccs is only
                   -- used to construct the edges and
                   -- stronglyConnCompFromEdgedVertices is deterministic
                   -- even with non-deterministic order of edges as
                   -- explained in Note [Deterministic SCC] in Digraph.
          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 = stronglyConnCompFromEdgedVerticesUniq 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_mod) -- Note [Do not update EPS with your own hi-boot]
        . filter ((== this_pkg) . moduleUnitId)
        $ dep_orphs sorted_deps
   dep_orphan_hashes <- getOrphanHashes hsc_env orph_mods

   -- Note [Do not update EPS with your own hi-boot]
   -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   -- (See also Trac #10182).  When your hs-boot file includes an orphan
   -- instance declaration, you may find that the dep_orphs of a module you
   -- import contains reference to yourself.  DO NOT actually load this module
   -- or add it to the orphan hashes: you're going to provide the orphan
   -- instances yourself, no need to consult hs-boot; if you do load the
   -- interface into EPS, you will see a duplicate orphan instance.

   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
   --   - the module level annotations,
   --   - usages
   --   - deps (home and external packages, dependent files)
   --   - hpc
   iface_hash <- computeFingerprint putNameLiterally
                      (mod_hash,
                       ann_fn (mkVarOcc "module"),  -- See mkIfaceAnnCache
                       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 (   all ifRuleAuto orph_rules
                                           -- See Note [Orphans and auto-generated 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
    ann_fn = mkIfaceAnnCache (mi_anns 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 (stableUnitIdCmp `on` fst) (dep_pkgs d),
          dep_orphs  = sortBy stableModuleCmp (dep_orphs d),
          dep_finsts = sortBy stableModuleCmp (dep_finsts d) }

-- | Creates cached lookup for the 'mi_anns' field of ModIface
-- Hackily, we use "module" as the OccName for any module-level annotations
mkIfaceAnnCache :: [IfaceAnnotation] -> OccName -> [AnnPayload]
mkIfaceAnnCache anns
  = \n -> lookupOccEnv env n `orElse` []
  where
    pair (IfaceAnnotation target value) =
      (case target of
          NamedTarget occn -> occn
          ModuleTarget _   -> mkVarOcc "module"
      , [value])
    -- flipping (++), so the first argument is always short
    env = mkOccEnv_C (flip (++)) (map pair anns)

{-
************************************************************************
*                                                                      *
          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 an unfolding in the interface.

   (c) the fixity of the identifier (if it exists)
   (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.
-}

type IfaceDeclABI = (Module, IfaceDecl, IfaceDeclExtras)

data IfaceDeclExtras
  = IfaceIdExtras IfaceIdExtras

  | IfaceDataExtras
       (Maybe Fixity)           -- Fixity of the tycon itself (if it exists)
       [IfaceInstABI]           -- Local class and family instances of this tycon
                                -- See Note [Orphans] in InstEnv
       [AnnPayload]             -- Annotations of the type itself
       [IfaceIdExtras]          -- For each constructor: fixity, RULES and annotations

  | IfaceClassExtras
       (Maybe Fixity)           -- Fixity of the class itself (if it exists)
       [IfaceInstABI]           -- Local instances of this class *or*
                                --   of its associated data types
                                -- See Note [Orphans] in InstEnv
       [AnnPayload]             -- Annotations of the type itself
       [IfaceIdExtras]          -- For each class method: fixity, RULES and annotations

  | IfaceSynonymExtras (Maybe Fixity) [AnnPayload]

  | IfaceFamilyExtras   (Maybe Fixity) [IfaceInstABI] [AnnPayload]

  | IfaceOtherDeclExtras

data IfaceIdExtras
  = IdExtras
       (Maybe Fixity)           -- Fixity of the Id (if it exists)
       [IfaceRule]              -- Rules for the Id
       [AnnPayload]             -- Annotations for the Id

-- 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 `unionNameSet` freeNamesDeclExtras extras

freeNamesDeclExtras :: IfaceDeclExtras -> NameSet
freeNamesDeclExtras (IfaceIdExtras id_extras)
  = freeNamesIdExtras id_extras
freeNamesDeclExtras (IfaceDataExtras  _ insts _ subs)
  = unionNameSets (mkNameSet insts : map freeNamesIdExtras subs)
freeNamesDeclExtras (IfaceClassExtras _ insts _ subs)
  = unionNameSets (mkNameSet insts : map freeNamesIdExtras subs)
freeNamesDeclExtras (IfaceSynonymExtras _ _)
  = emptyNameSet
freeNamesDeclExtras (IfaceFamilyExtras _ insts _)
  = mkNameSet insts
freeNamesDeclExtras IfaceOtherDeclExtras
  = emptyNameSet

freeNamesIdExtras :: IfaceIdExtras -> NameSet
freeNamesIdExtras (IdExtras _ rules _) = unionNameSets (map freeNamesIfRule rules)

instance Outputable IfaceDeclExtras where
  ppr IfaceOtherDeclExtras       = Outputable.empty
  ppr (IfaceIdExtras  extras)    = ppr_id_extras extras
  ppr (IfaceSynonymExtras fix anns) = vcat [ppr fix, ppr anns]
  ppr (IfaceFamilyExtras fix finsts anns) = vcat [ppr fix, ppr finsts, ppr anns]
  ppr (IfaceDataExtras fix insts anns stuff) = vcat [ppr fix, ppr_insts insts, ppr anns,
                                                ppr_id_extras_s stuff]
  ppr (IfaceClassExtras fix insts anns stuff) = vcat [ppr fix, ppr_insts insts, ppr anns,
                                                 ppr_id_extras_s stuff]

ppr_insts :: [IfaceInstABI] -> SDoc
ppr_insts _ = text "<insts>"

ppr_id_extras_s :: [IfaceIdExtras] -> SDoc
ppr_id_extras_s stuff = vcat (map ppr_id_extras stuff)

ppr_id_extras :: IfaceIdExtras -> SDoc
ppr_id_extras (IdExtras fix rules anns) = ppr fix $$ vcat (map ppr rules) $$ vcat (map ppr anns)

-- This instance is used only to compute fingerprints
instance Binary IfaceDeclExtras where
  get _bh = panic "no get for IfaceDeclExtras"
  put_ bh (IfaceIdExtras extras) = do
   putByte bh 1; put_ bh extras
  put_ bh (IfaceDataExtras fix insts anns cons) = do
   putByte bh 2; put_ bh fix; put_ bh insts; put_ bh anns; put_ bh cons
  put_ bh (IfaceClassExtras fix insts anns methods) = do
   putByte bh 3; put_ bh fix; put_ bh insts; put_ bh anns; put_ bh methods
  put_ bh (IfaceSynonymExtras fix anns) = do
   putByte bh 4; put_ bh fix; put_ bh anns
  put_ bh (IfaceFamilyExtras fix finsts anns) = do
   putByte bh 5; put_ bh fix; put_ bh finsts; put_ bh anns
  put_ bh IfaceOtherDeclExtras = putByte bh 6

instance Binary IfaceIdExtras where
  get _bh = panic "no get for IfaceIdExtras"
  put_ bh (IdExtras fix rules anns)= do { put_ bh fix; put_ bh rules; put_ bh anns }

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

declExtras fix_fn ann_fn rule_env inst_env fi_env decl
  = case decl of
      IfaceId{} -> IfaceIdExtras (id_extras n)
      IfaceData{ifCons=cons} ->
                     IfaceDataExtras (fix_fn n)
                        (map ifFamInstAxiom (lookupOccEnvL fi_env n) ++
                         map ifDFun         (lookupOccEnvL inst_env n))
                        (ann_fn 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)
                        (ann_fn n)
                        [id_extras op | IfaceClassOp op _ _ <- sigs]
      IfaceSynonym{} -> IfaceSynonymExtras (fix_fn n)
                                           (ann_fn n)
      IfaceFamily{} -> IfaceFamilyExtras (fix_fn n)
                        (map ifFamInstAxiom (lookupOccEnvL fi_env n))
                        (ann_fn n)
      _other -> IfaceOtherDeclExtras
  where
        n = ifName decl
        id_extras occ = IdExtras (fix_fn occ) (lookupOccEnvL rule_env occ) (ann_fn 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 _ -> throwGhcExceptionIO (PhaseFailed cmd r)
    ExitSuccess -> do
        hash_str <- readFile tmp2
        return $! readHexFingerprint hash_str
-}

----------------------
-- 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 -> IsOrphan) -- Extract orphan status from 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
        | NotOrphan occ <- get_key d
        = (extendOccEnv_Acc (:) singleton non_orphs occ d, orphs)
        | otherwise = (non_orphs, d:orphs)

{-
************************************************************************
*                                                                      *
       Keeping track of what we've slurped, and fingerprints
*                                                                      *
************************************************************************
-}


mkIfaceAnnotation :: Annotation -> IfaceAnnotation
mkIfaceAnnotation (Annotation { ann_target = target, ann_value = payload })
  = IfaceAnnotation {
        ifAnnotatedTarget = fmap nameOccName target,
        ifAnnotatedValue = payload
    }

mkIfaceExports :: [AvailInfo] -> [IfaceExport]  -- Sort to make canonical
mkIfaceExports exports
  = sortBy stableAvailCmp (map sort_subs exports)
  where
    sort_subs :: AvailInfo -> AvailInfo
    sort_subs (Avail b n) = Avail b n
    sort_subs (AvailTC n [] fs) = AvailTC n [] (sort_flds fs)
    sort_subs (AvailTC n (m:ms) fs)
       | n==m      = AvailTC n (m:sortBy stableNameCmp ms) (sort_flds fs)
       | otherwise = AvailTC n (sortBy stableNameCmp (m:ms)) (sort_flds fs)
       -- Maintain the AvailTC Invariant

    sort_flds = sortBy (stableNameCmp `on` flSelector)

{-
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
*                                                                      *
************************************************************************
-}

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
             case read_result of
                 Failed err -> do
                     traceIf (text "FYI: cannot 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
            | gopt 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.
                    Just iface -> checkVersions hsc_env mod_summary iface

-- | Check if a module is still the same 'version'.
--
-- This function is called in the recompilation checker after we have
-- determined that the module M being checked hasn't had any changes
-- to its source file since we last compiled M. So at this point in general
-- two things may have changed that mean we should recompile M:
--   * The interface export by a dependency of M has changed.
--   * The compiler flags specified this time for M have changed
--     in a manner that is significant for recompilaiton.
-- We return not just if we should recompile the object file but also
-- if we should rebuild the interface file.
checkVersions :: HscEnv
              -> ModSummary
              -> ModIface       -- Old interface
              -> IfG (RecompileRequired, Maybe ModIface)
checkVersions hsc_env mod_summary iface
  = do { traceHiDiffs (text "Considering whether compilation is required for" <+>
                        ppr (mi_module iface) <> colon)

       ; recomp <- checkFlagHash hsc_env iface
       ; if recompileRequired recomp then return (recomp, Nothing) else do {
       ; if getSigOf (hsc_dflags hsc_env) (moduleName (mi_module iface))
                /= mi_sig_of iface
            then return (RecompBecause "sig-of changed", Nothing) else do {
       ; recomp <- checkDependencies hsc_env mod_summary iface
       ; if recompileRequired recomp then return (recomp, Just iface) else do {

       -- Source code unchanged and no errors yet... carry on
       --
       -- First put the dependent-module info, read from the old
       -- interface, into the envt, so that when we look for
       -- interfaces we look for the right one (.hi or .hi-boot)
       --
       -- It's just temporary because either the usage check will succeed
       -- (in which case we are done with this module) or it'll fail (in which
       -- case we'll compile the module from scratch anyhow).
       --
       -- We do this regardless of compilation mode, although in --make mode
       -- all the dependent modules should be in the HPT already, so it's
       -- quite redundant
       ; updateEps_ $ \eps  -> eps { eps_is_boot = udfmToUfm mod_deps }
       ; recomp <- checkList [checkModUsage this_pkg u | u <- mi_usages iface]
       ; return (recomp, Just iface)
    }}}}
  where
    this_pkg = thisPackage (hsc_dflags hsc_env)
    -- This is a bit of a hack really
    mod_deps :: DModuleNameEnv (ModuleName, IsBootInterface)
    mod_deps = mkModDeps (dep_mods (mi_deps iface))

-- | Check the flags haven't changed
checkFlagHash :: HscEnv -> ModIface -> IfG RecompileRequired
checkFlagHash hsc_env iface = do
    let old_hash = mi_flag_hash iface
    new_hash <- liftIO $ fingerprintDynFlags (hsc_dflags hsc_env)
                                             (mi_module iface)
                                             putNameLiterally
    case old_hash == new_hash of
        True  -> up_to_date (text "Module flags unchanged")
        False -> out_of_date_hash "flags changed"
                     (text "  Module flags have changed")
                     old_hash new_hash

-- If the direct imports of this module are resolved to targets that
-- are not among the dependencies of the previous interface file,
-- then we definitely need to recompile.  This catches cases like
--   - an exposed package has been upgraded
--   - we are compiling with different package flags
--   - a home module that was shadowing a package module has been removed
--   - a new home module has been added that shadows a package module
-- See bug #1372.
--
-- Returns True if recompilation is required.
checkDependencies :: HscEnv -> ModSummary -> ModIface -> IfG RecompileRequired
checkDependencies hsc_env summary iface
 = checkList (map dep_missing (ms_imps summary ++ ms_srcimps summary))
  where
   prev_dep_mods = dep_mods (mi_deps iface)
   prev_dep_pkgs = dep_pkgs (mi_deps iface)

   this_pkg = thisPackage (hsc_dflags hsc_env)

   dep_missing (mb_pkg, L _ mod) = do
     find_res <- liftIO $ findImportedModule hsc_env mod (mb_pkg)
     let reason = moduleNameString mod ++ " changed"
     case find_res of
        Found _ mod
          | pkg == this_pkg
           -> if moduleName mod `notElem` map fst prev_dep_mods
                 then do traceHiDiffs $
                           text "imported module " <> quotes (ppr mod) <>
                           text " not among previous dependencies"
                         return (RecompBecause reason)
                 else
                         return UpToDate
          | otherwise
           -> if pkg `notElem` (map fst prev_dep_pkgs)
                 then do traceHiDiffs $
                           text "imported module " <> quotes (ppr mod) <>
                           text " is from package " <> quotes (ppr pkg) <>
                           text ", which is not among previous dependencies"
                         return (RecompBecause reason)
                 else
                         return UpToDate
           where pkg = moduleUnitId mod
        _otherwise  -> return (RecompBecause reason)

needInterface :: Module -> (ModIface -> IfG RecompileRequired)
              -> IfG RecompileRequired
needInterface mod continue
  = do  -- Load the imported interface if possible
    let doc_str = sep [text "need version info for", ppr mod]
    traceHiDiffs (text "Checking usages for module" <+> ppr mod)

    mb_iface <- loadInterface doc_str mod ImportBySystem
        -- Load the interface, but don't complain on failure;
        -- Instead, get an Either back which we can test

    case mb_iface of
      Failed _ -> do
        traceHiDiffs (sep [text "Couldn't load interface for module",
                           ppr mod])
        return MustCompile
                  -- Couldn't find or parse a module mentioned in the
                  -- old interface file.  Don't complain: it might
                  -- just be that the current module doesn't need that
                  -- import and it's been deleted
      Succeeded iface -> continue iface


-- | Given the usage information extracted from the old
-- M.hi file for the module being compiled, figure out
-- whether M needs to be recompiled.
checkModUsage :: UnitId -> Usage -> IfG RecompileRequired
checkModUsage _this_pkg UsagePackageModule{
                                usg_mod = mod,
                                usg_mod_hash = old_mod_hash }
  = needInterface mod $ \iface -> do
    let reason = moduleNameString (moduleName mod) ++ " changed"
    checkModuleFingerprint reason old_mod_hash (mi_mod_hash iface)
        -- We only track the ABI hash of package modules, rather than
        -- individual entity usages, so if the ABI hash changes we must
        -- recompile.  This is safe but may entail more recompilation when
        -- a dependent package has changed.

checkModUsage this_pkg UsageHomeModule{
                                usg_mod_name = mod_name,
                                usg_mod_hash = old_mod_hash,
                                usg_exports = maybe_old_export_hash,
                                usg_entities = old_decl_hash }
  = do
    let mod = mkModule this_pkg mod_name
    needInterface mod $ \iface -> do

    let
        new_mod_hash    = mi_mod_hash    iface
        new_decl_hash   = mi_hash_fn     iface
        new_export_hash = mi_exp_hash    iface

        reason = moduleNameString mod_name ++ " changed"

        -- CHECK MODULE
    recompile <- checkModuleFingerprint reason old_mod_hash new_mod_hash
    if not (recompileRequired recompile)
      then return UpToDate
      else do

        -- CHECK EXPORT LIST
        checkMaybeHash reason maybe_old_export_hash new_export_hash
            (text "  Export list changed") $ do

        -- CHECK ITEMS ONE BY ONE
        recompile <- checkList [ checkEntityUsage reason new_decl_hash u
                               | u <- old_decl_has…