Generalise Package Support

This patch pushes through one fundamental change: a module is now
identified by the pair of its package and module name, whereas
previously it was identified by its module name alone.  This means
that now a program can contain multiple modules with the same name, as
long as they belong to different packages.

This is a language change - the Haskell report says nothing about
packages, but it is now necessary to understand packages in order to
understand GHC's module system.  For example, a type T from module M
in package P is different from a type T from module M in package Q.
Previously this wasn't an issue because there could only be a single
module M in the program.

The "module restriction" on combining packages has therefore been
lifted, and a program can contain multiple versions of the same
package.

Note that none of the proposed syntax changes have yet been
implemented, but the architecture is geared towards supporting import
declarations qualified by package name, and that is probably the next
step.

It is now necessary to specify the package name when compiling a
package, using the -package-name flag (which has been un-deprecated).
Fortunately Cabal still uses -package-name.

Certain packages are "wired in".  Currently the wired-in packages are:
base, haskell98, template-haskell and rts, and are always referred to
by these versionless names.  Other packages are referred to with full
package IDs (eg. "network-1.0").  This is because the compiler needs
to refer to entities in the wired-in packages, and we didn't want to
bake the version of these packages into the comiler.  It's conceivable
that someone might want to upgrade the base package independently of
GHC.

Internal changes:

  - There are two module-related types:

        ModuleName      just a FastString, the name of a module
        Module          a pair of a PackageId and ModuleName

    A mapping from ModuleName can be a UniqFM, but a mapping from Module
    must be a FiniteMap (we provide it as ModuleEnv).

  - The "HomeModules" type that was passed around the compiler is now
    gone, replaced in most cases by the current package name which is
    contained in DynFlags.  We can tell whether a Module comes from the
    current package by comparing its package name against the current
    package.

  - While I was here, I changed PrintUnqual to be a little more useful:
    it now returns the ModuleName that the identifier should be qualified
    with according to the current scope, rather than its original
    module.  Also, PrintUnqual tells whether to qualify module names with
    package names (currently unused).

Docs to follow.

1 files changed, 70 insertions, 54 deletions

diff --git a/compiler/ghci/InteractiveUI.hs b/compiler/ghci/InteractiveUI.hs
index 55384bc63e..8a20fb1b99 100644
--- a/compiler/ghci/InteractiveUI.hs
+++ b/compiler/ghci/InteractiveUI.hs
@@ -31,9 +31,9 @@ import PrelNames        ( breakpointJumpName, breakpointCondJumpName )
 
 -- The GHC interface
 import qualified GHC
-import GHC		( Session, verbosity, dopt, DynFlag(..), Target(..),
+import GHC		( Session, dopt, DynFlag(..), Target(..),
 			  TargetId(..), DynFlags(..),
-			  pprModule, Type, Module, SuccessFlag(..),
+			  pprModule, Type, Module, ModuleName, SuccessFlag(..),
 			  TyThing(..), Name, LoadHowMuch(..), Phase,
 			  GhcException(..), showGhcException,
 			  CheckedModule(..), SrcLoc )
@@ -45,7 +45,6 @@ import PprTyThing
 import Outputable
 
 -- for createtags (should these come via GHC?)
-import Module		( moduleString )
 import Name		( nameSrcLoc, nameModule, nameOccName )
 import OccName		( pprOccName )
 import SrcLoc		( isGoodSrcLoc, srcLocFile, srcLocLine, srcLocCol )
@@ -95,7 +94,6 @@ import System.IO.Error as IO
 import Data.Char
 import Control.Monad as Monad
 import Foreign.StablePtr	( newStablePtr )
-import Text.Printf
 
 import GHC.Exts		( unsafeCoerce# )
 import GHC.IOBase	( IOErrorType(InvalidArgument) )
@@ -242,13 +240,15 @@ jumpFunction session@(Session ref) (I# idsPtr) hValues location b
 		  	      ic_type_env     = new_type_env }
          writeIORef ref (hsc_env { hsc_IC = new_ic })
          is_tty <- hIsTerminalDevice stdin
+         prel_mod <- GHC.findModule session prel_name Nothing
          withExtendedLinkEnv (zip names hValues) $
            startGHCi (interactiveLoop is_tty True)
                      GHCiState{ progname = "<interactive>",
                                 args = [],
                                 prompt = location++"> ",
                                 session = session,
-                                options = [] }
+                                options = [],
+                                prelude =  prel_mod }
          writeIORef ref hsc_env
          putStrLn $ "Returning to normal execution..."
          return b
@@ -284,7 +284,8 @@ interactiveUI session srcs maybe_expr = do
    hSetBuffering stdin NoBuffering
 
 	-- initial context is just the Prelude
-   GHC.setContext session [] [prelude_mod]
+   prel_mod <- GHC.findModule session prel_name Nothing
+   GHC.setContext session [] [prel_mod]
 
 #ifdef USE_READLINE
    Readline.initialize
@@ -305,7 +306,8 @@ interactiveUI session srcs maybe_expr = do
 		   args = [],
                    prompt = "%s> ",
 		   session = session,
-		   options = [] }
+		   options = [],
+                   prelude = prel_mod }
 
 #ifdef USE_READLINE
    Readline.resetTerminal Nothing
@@ -313,6 +315,8 @@ interactiveUI session srcs maybe_expr = do
 
    return ()
 
+prel_name = GHC.mkModuleName "Prelude"
+
 runGHCi :: [(FilePath, Maybe Phase)] -> Maybe String -> GHCi ()
 runGHCi paths maybe_expr = do
   let read_dot_files = not opt_IgnoreDotGhci
@@ -807,7 +811,7 @@ loadModule' files = do
 
 checkModule :: String -> GHCi ()
 checkModule m = do
-  let modl = GHC.mkModule m
+  let modl = GHC.mkModuleName m
   session <- getSession
   result <- io (GHC.checkModule session modl)
   case result of
@@ -816,7 +820,7 @@ checkModule m = do
 	case checkedModuleInfo r of
 	   Just cm | Just scope <- GHC.modInfoTopLevelScope cm -> 
 		let
-		    (local,global) = partition ((== modl) . GHC.nameModule) scope
+		    (local,global) = partition ((== modl) . GHC.moduleName . GHC.nameModule) scope
 		in
 			(text "global names: " <+> ppr global) $$
 		        (text "local  names: " <+> ppr local)
@@ -832,22 +836,23 @@ reloadModule "" = do
 reloadModule m = do
   io (revertCAFs)		-- always revert CAFs on reload.
   session <- getSession
-  ok <- io (GHC.load session (LoadUpTo (GHC.mkModule m)))
+  ok <- io (GHC.load session (LoadUpTo (GHC.mkModuleName m)))
   afterLoad ok session
 
 afterLoad ok session = do
   io (revertCAFs)  -- always revert CAFs on load.
   graph <- io (GHC.getModuleGraph session)
-  graph' <- filterM (io . GHC.isLoaded session . GHC.ms_mod) graph
+  graph' <- filterM (io . GHC.isLoaded session . GHC.ms_mod_name) graph
   setContextAfterLoad session graph'
-  modulesLoadedMsg ok (map GHC.ms_mod graph')
+  modulesLoadedMsg ok (map GHC.ms_mod_name graph')
 #if defined(GHCI) && defined(BREAKPOINT)
   io (extendLinkEnv [(breakpointJumpName,unsafeCoerce# (jumpFunction session))
                     ,(breakpointCondJumpName,unsafeCoerce# (jumpCondFunction session))])
 #endif
 
 setContextAfterLoad session [] = do
-  io (GHC.setContext session [] [prelude_mod])
+  prel_mod <- getPrelude
+  io (GHC.setContext session [] [prel_mod])
 setContextAfterLoad session ms = do
   -- load a target if one is available, otherwise load the topmost module.
   targets <- io (GHC.getTargets session)
@@ -864,7 +869,7 @@ setContextAfterLoad session ms = do
 	(m:_) -> Just m
 
    summary `matches` Target (TargetModule m) _
-	= GHC.ms_mod summary == m
+	= GHC.ms_mod_name summary == m
    summary `matches` Target (TargetFile f _) _ 
 	| Just f' <- GHC.ml_hs_file (GHC.ms_location summary)	= f == f'
    summary `matches` target
@@ -873,17 +878,19 @@ setContextAfterLoad session ms = do
    load_this summary | m <- GHC.ms_mod summary = do
 	b <- io (GHC.moduleIsInterpreted session m)
 	if b then io (GHC.setContext session [m] []) 
-       	     else io (GHC.setContext session []  [prelude_mod,m])
+       	     else do
+                   prel_mod <- getPrelude
+                   io (GHC.setContext session []  [prel_mod,m])
 
 
-modulesLoadedMsg :: SuccessFlag -> [Module] -> GHCi ()
+modulesLoadedMsg :: SuccessFlag -> [ModuleName] -> GHCi ()
 modulesLoadedMsg ok mods = do
   dflags <- getDynFlags
   when (verbosity dflags > 0) $ do
    let mod_commas 
 	| null mods = text "none."
 	| otherwise = hsep (
-	    punctuate comma (map pprModule mods)) <> text "."
+	    punctuate comma (map ppr mods)) <> text "."
    case ok of
     Failed ->
        io (putStrLn (showSDoc (text "Failed, modules loaded: " <> mod_commas)))
@@ -950,8 +957,9 @@ createTagsFile session tagskind tagFile = do
         is_interpreted <- GHC.moduleIsInterpreted session m
         -- should we just skip these?
         when (not is_interpreted) $
-          throwDyn (CmdLineError ("module '" ++ moduleString m ++ "' is not interpreted"))
-
+          throwDyn (CmdLineError ("module '" 
+                                ++ GHC.moduleNameString (GHC.moduleName m)
+                                ++ "' is not interpreted"))
         mbModInfo <- GHC.getModuleInfo session m
         let unqual 
 	      | Just modinfo <- mbModInfo,
@@ -1039,8 +1047,7 @@ browseCmd m =
 
 browseModule m exports_only = do
   s <- getSession
-
-  let modl = GHC.mkModule m
+  modl <- io $ GHC.findModule s (GHC.mkModuleName m) Nothing
   is_interpreted <- io (GHC.moduleIsInterpreted s modl)
   when (not is_interpreted && not exports_only) $
 	throwDyn (CmdLineError ("module '" ++ m ++ "' is not interpreted"))
@@ -1048,7 +1055,8 @@ browseModule m exports_only = do
   -- Temporarily set the context to the module we're interested in,
   -- just so we can get an appropriate PrintUnqualified
   (as,bs) <- io (GHC.getContext s)
-  io (if exports_only then GHC.setContext s [] [prelude_mod,modl]
+  prel_mod <- getPrelude
+  io (if exports_only then GHC.setContext s [] [prel_mod,modl]
 		      else GHC.setContext s [modl] [])
   unqual <- io (GHC.getPrintUnqual s)
   io (GHC.setContext s as bs)
@@ -1089,47 +1097,53 @@ setContext str
     sensible ('*':m) = looksLikeModuleName m
     sensible m       = looksLikeModuleName m
 
-newContext mods = do
-  session <- getSession
-  (as,bs) <- separate session mods [] []
-  let bs' = if null as && prelude_mod `notElem` bs then prelude_mod:bs else bs
-  io (GHC.setContext session as bs')
-
-separate :: Session -> [String] -> [Module] -> [Module]
-  -> GHCi ([Module],[Module])
+separate :: Session -> [String] -> [Module] -> [Module] 
+        -> GHCi ([Module],[Module])
 separate session []           as bs = return (as,bs)
-separate session (('*':m):ms) as bs = do
-   let modl = GHC.mkModule m
-   b <- io (GHC.moduleIsInterpreted session modl)
-   if b then separate session ms (modl:as) bs
-   	else throwDyn (CmdLineError ("module '" ++ m ++ "' is not interpreted"))
-separate session (m:ms)       as bs = separate session ms as (GHC.mkModule m:bs)
-
-prelude_mod = GHC.mkModule "Prelude"
+separate session (('*':str):ms) as bs = do
+   m <- io $ GHC.findModule session (GHC.mkModuleName str) Nothing
+   b <- io $ GHC.moduleIsInterpreted session m
+   if b then separate session ms (m:as) bs
+   	else throwDyn (CmdLineError ("module '"
+                        ++ GHC.moduleNameString (GHC.moduleName m)
+                        ++ "' is not interpreted"))
+separate session (str:ms) as bs = do
+  m <- io $ GHC.findModule session (GHC.mkModuleName str) Nothing
+  separate session ms as (m:bs)
+
+newContext :: [String] -> GHCi ()
+newContext strs = do
+  s <- getSession
+  (as,bs) <- separate s strs [] []
+  prel_mod <- getPrelude
+  let bs' = if null as && prel_mod `notElem` bs then prel_mod:bs else bs
+  io $ GHC.setContext s as bs'
 
 
-addToContext mods = do
-  cms <- getSession
-  (as,bs) <- io (GHC.getContext cms)
+addToContext :: [String] -> GHCi ()
+addToContext strs = do
+  s <- getSession
+  (as,bs) <- io $ GHC.getContext s
 
-  (as',bs') <- separate cms mods [] []
+  (new_as,new_bs) <- separate s strs [] []
 
-  let as_to_add = as' \\ (as ++ bs)
-      bs_to_add = bs' \\ (as ++ bs)
+  let as_to_add = new_as \\ (as ++ bs)
+      bs_to_add = new_bs \\ (as ++ bs)
 
-  io (GHC.setContext cms (as ++ as_to_add) (bs ++ bs_to_add))
+  io $ GHC.setContext s (as ++ as_to_add) (bs ++ bs_to_add)
 
 
-removeFromContext mods = do
-  cms <- getSession
-  (as,bs) <- io (GHC.getContext cms)
+removeFromContext :: [String] -> GHCi ()
+removeFromContext strs = do
+  s <- getSession
+  (as,bs) <- io $ GHC.getContext s
 
-  (as_to_remove,bs_to_remove) <- separate cms mods [] []
+  (as_to_remove,bs_to_remove) <- separate s strs [] []
 
   let as' = as \\ (as_to_remove ++ bs_to_remove)
       bs' = bs \\ (as_to_remove ++ bs_to_remove)
 
-  io (GHC.setContext cms as' bs')
+  io $ GHC.setContext s as' bs'
 
 ----------------------------------------------------------------------------
 -- Code for `:set'
@@ -1357,7 +1371,7 @@ completeModule w = do
 completeHomeModule w = do
   s <- restoreSession
   g <- GHC.getModuleGraph s
-  let home_mods = map GHC.ms_mod g
+  let home_mods = map GHC.ms_mod_name g
   return (filter (w `isPrefixOf`) (map (showSDoc.ppr) home_mods))
 
 completeSetOptions w = do
@@ -1393,9 +1407,9 @@ getCommonPrefix (s:ss) = foldl common s ss
 	   | c == d = c : common cs ds
 	   | otherwise = ""
 
-allExposedModules :: DynFlags -> [Module]
+allExposedModules :: DynFlags -> [ModuleName]
 allExposedModules dflags 
- = map GHC.mkModule (concat (map exposedModules (filter exposed (eltsUFM pkg_db))))
+ = map GHC.mkModuleName (concat (map exposedModules (filter exposed (eltsUFM pkg_db))))
  where
   pkg_db = pkgIdMap (pkgState dflags)
 #else
@@ -1418,7 +1432,8 @@ data GHCiState = GHCiState
 	args	       :: [String],
         prompt         :: String,
 	session        :: GHC.Session,
-	options        :: [GHCiOption]
+	options        :: [GHCiOption],
+        prelude        :: Module
      }
 
 data GHCiOption 
@@ -1445,6 +1460,7 @@ setGHCiState s = GHCi $ \r -> writeIORef r s
 
 -- for convenience...
 getSession = getGHCiState >>= return . session
+getPrelude = getGHCiState >>= return . prelude
 
 GLOBAL_VAR(saved_sess, no_saved_sess, Session)
 no_saved_sess = error "no saved_ses"