Refactor the imports of InteractiveContext

Instead of two fields
   ic_toplev_scope :: [Module]
   ic_imports      :: [ImportDecl RdrName]

we now just have one
   ic_imports :: [InteractiveImport]
with the auxiliary data type
   data InteractiveImport
    = IIDecl (ImportDecl RdrName)  -- Bring the exports of a particular module
    	   	       		   -- (filtered by an import decl) into scope

    | IIModule Module	-- Bring into scope the entire top-level envt of
    	     		-- of this module, including the things imported
			-- into it.

This makes lots of code less confusing.  No change in behaviour.
It's preparatory to fixing Trac #5147.

While I was at I also
  * Cleaned up the handling of the "implicit" Prelude import
    by adding a ideclImplicit field to ImportDecl.  This
    significantly reduces plumbing in the handling of
    the implicit Prelude import

  * Used record notation consistently for ImportDecl

6 files changed, 63 insertions, 50 deletions

diff --git a/compiler/main/GHC.hs b/compiler/main/GHC.hs
index 3ebfd52bad..c7b7687023 100644
--- a/compiler/main/GHC.hs
+++ b/compiler/main/GHC.hs
@@ -38,7 +38,7 @@ module GHC (
 	
 	-- * Loading\/compiling the program
 	depanal,
-	load, LoadHowMuch(..),
+	load, LoadHowMuch(..), InteractiveImport(..),
 	SuccessFlag(..), succeeded, failed,
         defaultWarnErrLogger, WarnErrLogger,
 	workingDirectoryChanged,
diff --git a/compiler/main/HeaderInfo.hs b/compiler/main/HeaderInfo.hs
index c7a281cff8..a3f7e79dde 100644
--- a/compiler/main/HeaderInfo.hs
+++ b/compiler/main/HeaderInfo.hs
@@ -100,19 +100,21 @@ mkPrelImports this_mod loc implicit_prelude import_decls
   | otherwise = [preludeImportDecl]
   where
       explicit_prelude_import
-       = notNull [ () | L _ (ImportDecl mod Nothing _ _ _ _ _) <- import_decls,
-	           unLoc mod == pRELUDE_NAME ]
+       = notNull [ () | L _ (ImportDecl { ideclName = mod
+                                        , ideclPkgQual = Nothing }) 
+                          <- import_decls
+	              , unLoc mod == pRELUDE_NAME ]
 
       preludeImportDecl :: LImportDecl RdrName
       preludeImportDecl
-        = L loc $
-          ImportDecl (L loc pRELUDE_NAME)
-               Nothing  {- No specific package -}
-               False    {- Not a boot interface -}
-               False    {- Not a safe import -}
-               False    {- Not qualified -}
-               Nothing  {- No "as" -}
-               Nothing  {- No import list -}
+        = L loc $ ImportDecl { ideclName      = L loc pRELUDE_NAME,
+      		    	       ideclPkgQual   = Nothing,
+      		    	       ideclSource    = False,
+      		    	       ideclSafe      = False,  -- Not a safe import
+      		    	       ideclQualified = False,
+      		    	       ideclImplicit  = True,	-- Implicit!
+      		    	       ideclAs        = Nothing,
+      		    	       ideclHiding    = Nothing  }
 
 parseError :: SrcSpan -> Message -> IO a
 parseError span err = throwOneError $ mkPlainErrMsg span err
diff --git a/compiler/main/HscMain.lhs b/compiler/main/HscMain.lhs
index 2603d21bc4..ff52d2de76 100644
--- a/compiler/main/HscMain.lhs
+++ b/compiler/main/HscMain.lhs
@@ -312,9 +312,7 @@ hscRnImportDecls hsc_env this_mod import_decls
   = runHsc hsc_env $ ioMsgMaybe $ 
     initTc hsc_env HsSrcFile False this_mod $
     fmap tcg_rdr_env $ 
-    tcRnImports hsc_env this_mod loc import_decls
-  where
-    loc = mkGeneralSrcSpan (mkFastString "In a call to hscRnImportDecls")
+    tcRnImports hsc_env this_mod import_decls
 #endif
 
 -- -----------------------------------------------------------------------------
diff --git a/compiler/main/HscStats.lhs b/compiler/main/HscStats.lhs
index 76699a5f85..34310e038c 100644
--- a/compiler/main/HscStats.lhs
+++ b/compiler/main/HscStats.lhs
@@ -123,7 +123,8 @@ ppSourceStats short (L _ (HsModule _ exports imports ldecls _ _))
     sig_info (GenericSig _ _)   = (0,0,0,0,1)
     sig_info _                  = (0,0,0,0,0)
 
-    import_info (L _ (ImportDecl _ _ _ safe qual as spec))
+    import_info (L _ (ImportDecl { ideclSafe = safe, ideclQualified = qual
+                                 , ideclAs = as, ideclHiding = spec }))
 	= add7 (1, safe_info safe, qual_info qual, as_info as, 0,0,0) (spec_info spec)
     safe_info = qual_info
     qual_info False  = 0
diff --git a/compiler/main/HscTypes.lhs b/compiler/main/HscTypes.lhs
index d43105b02d..436feb0094 100644
--- a/compiler/main/HscTypes.lhs
+++ b/compiler/main/HscTypes.lhs
@@ -42,6 +42,7 @@ module HscTypes (
 
         -- * Interactive context
 	InteractiveContext(..), emptyInteractiveContext, 
+        InteractiveImport(..),
 	icPrintUnqual, extendInteractiveContext,
         substInteractiveContext,
         mkPrintUnqualified, pprModulePrefix,
@@ -883,15 +884,12 @@ emptyModIface mod
 --
 data InteractiveContext 
   = InteractiveContext { 
-         -- These two fields are only stored here so that the client
-         -- can retrieve them with GHC.getContext.  GHC itself doesn't
-         -- use them, but it does reset them to empty sometimes (such
+         -- This field is only stored here so that the client
+         -- can retrieve it with GHC.getContext.  GHC itself doesn't
+         -- use it, but does reset it to empty sometimes (such
          -- as before a GHC.load).  The context is set with GHC.setContext.
-         ic_toplev_scope :: [Module],
-             -- ^ The context includes the "top-level" scope of
-             -- these modules
-         ic_imports :: [ImportDecl RdrName],
-             -- ^ The context is extended with these import declarations
+         ic_imports :: [InteractiveImport],
+             -- ^ The GHCi context is extended with these imports
 
          ic_rn_gbl_env :: GlobalRdrEnv,
              -- ^ The contexts' cached 'GlobalRdrEnv', built by
@@ -914,11 +912,17 @@ data InteractiveContext
              -- virtual CWD of the program
     }
 
+data InteractiveImport 
+  = IIDecl (ImportDecl RdrName)	-- Bring the exports of a particular module
+    	   	       		-- (filtered by an import decl) into scope
 
+  | IIModule Module	-- Bring into scope the entire top-level envt of
+    	     		-- of this module, including the things imported
+			-- into it.
+ 
 emptyInteractiveContext :: InteractiveContext
 emptyInteractiveContext
-  = InteractiveContext { ic_toplev_scope = [],
-                         ic_imports = [],
+  = InteractiveContext { ic_imports = [],
 			 ic_rn_gbl_env = emptyGlobalRdrEnv,
 			 ic_tmp_ids = []
 #ifdef GHCI
@@ -948,6 +952,10 @@ substInteractiveContext ictxt@InteractiveContext{ic_tmp_ids=ids} subst
   = ictxt { ic_tmp_ids = map subst_ty ids }
   where
    subst_ty id = id `setIdType` substTy subst (idType id)
+
+instance Outputable InteractiveImport where
+  ppr (IIModule m) = char '*' <> ppr m
+  ppr (IIDecl d)   = ppr d
 \end{code}
 
 %************************************************************************
@@ -1675,6 +1683,7 @@ ms_imps ms = ms_textual_imps ms ++ map mk_additional_import (dynFlagDependencies
       ideclName = noLoc mod_nm,
       ideclPkgQual = Nothing,
       ideclSource = False,
+      ideclImplicit = True,	-- Maybe implicit because not "in the program text"
       ideclQualified = False,
       ideclAs = Nothing,
       ideclHiding = Nothing,
diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs
index 0386273de8..24f340b33d 100644
--- a/compiler/main/InteractiveEval.hs
+++ b/compiler/main/InteractiveEval.hs
@@ -778,29 +778,32 @@ fromListBL bound l = BL (length l) bound l []
 -- Setting the context doesn't throw away any bindings; the bindings
 -- we've built up in the InteractiveContext simply move to the new
 -- module.  They always shadow anything in scope in the current context.
-setContext :: GhcMonad m =>
-        [Module]	-- ^ entire top level scope of these modules
-        -> [ImportDecl RdrName]       -- ^ these import declarations
-        -> m ()
-setContext toplev_mods import_decls = do
-    hsc_env <- getSession
-    let old_ic  = hsc_IC     hsc_env
-        hpt     = hsc_HPT    hsc_env
-        imprt_decls = map noLoc import_decls
-    --
-    import_env  <-
-        if null imprt_decls then return emptyGlobalRdrEnv else do
-            let this_mod | null toplev_mods = pRELUDE
-                         | otherwise        = head toplev_mods
-            liftIO $ hscRnImportDecls hsc_env this_mod imprt_decls
-
-    toplev_envs <- liftIO $ mapM (mkTopLevEnv hpt) toplev_mods
-
-    let all_env = foldr plusGlobalRdrEnv import_env toplev_envs
-    modifySession $ \_ ->
-        hsc_env{ hsc_IC = old_ic { ic_toplev_scope = toplev_mods,
-                                   ic_imports      = import_decls,
-                                   ic_rn_gbl_env   = all_env }}
+setContext :: GhcMonad m => [InteractiveImport] -> m ()
+setContext imports
+  = do { hsc_env <- getSession
+       ; let old_ic = hsc_IC hsc_env
+       ; all_env <- liftIO $ findGlobalRdrEnv hsc_env imports
+       ; modifySession $ \_ ->
+         hsc_env{ hsc_IC = old_ic { ic_imports      = imports
+                                  , ic_rn_gbl_env   = all_env }}}
+
+findGlobalRdrEnv :: HscEnv -> [InteractiveImport] -> IO GlobalRdrEnv
+-- Compute the GlobalRdrEnv for the interactive context
+findGlobalRdrEnv hsc_env imports
+  = do { idecls_env <- hscRnImportDecls hsc_env this_mod idecls
+       	 	    -- This call also loads any orphan modules
+       ; imods_env  <- mapM (mkTopLevEnv (hsc_HPT hsc_env)) imods
+       ; return (foldr plusGlobalRdrEnv idecls_env imods_env) }
+  where
+    idecls :: [LImportDecl RdrName]
+    idecls = [noLoc d | IIDecl d <- imports]
+
+    imods :: [Module]
+    imods = [m | IIModule m <- imports]
+
+    this_mod = case imods of 
+                 []    -> pRELUDE
+                 (m:_) -> m
 
 availsToGlobalRdrEnv :: ModuleName -> [AvailInfo] -> GlobalRdrEnv
 availsToGlobalRdrEnv mod_name avails
@@ -828,9 +831,9 @@ mkTopLevEnv hpt modl
 -- | Get the interactive evaluation context, consisting of a pair of the
 -- set of modules from which we take the full top-level scope, and the set
 -- of modules from which we take just the exports respectively.
-getContext :: GhcMonad m => m ([Module],[ImportDecl RdrName])
+getContext :: GhcMonad m => m [InteractiveImport]
 getContext = withSession $ \HscEnv{ hsc_IC=ic } ->
-               return (ic_toplev_scope ic, ic_imports ic)
+             return (ic_imports ic)
 
 -- | Returns @True@ if the specified module is interpreted, and hence has
 -- its full top-level scope available.