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

1 files changed, 12 insertions, 10 deletions

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