From 2427987977bc68edacd7b552909bfdb264884b85 Mon Sep 17 00:00:00 2001
From: sof <unknown>
Date: Fri, 7 Dec 2001 07:37:43 +0000
Subject: [PATCH] [project @ 2001-12-07 07:37:43 by sof] Tidyup - previous
 instance-decl commit fell a bit short:

 * RnEnv.lookupInstDeclBndr unceremoniously fell over when passed
   an out-of-scope class name.

 * the AvailEnv carried around didn't common up type/class info
   (i.e.,  AvailTCs), but rather type/class and method/label names,
   causing the renamer to (semi)randomly report instance methods as
   being out-of-scope in the presence of multiple imports for a module.

 * didn't support 'hiding' of class / method names (for the purposes
   of checking instance decls).
---
 ghc/compiler/rename/RnEnv.lhs   |    3 +++
 ghc/compiler/rename/RnNames.lhs |   33 ++++++++++++++++++++++++++-------
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/ghc/compiler/rename/RnEnv.lhs b/ghc/compiler/rename/RnEnv.lhs
index a7fd614..affbcc9 100644
--- a/ghc/compiler/rename/RnEnv.lhs
+++ b/ghc/compiler/rename/RnEnv.lhs
@@ -258,6 +258,9 @@ lookupInstDeclBndr cls_name rdr_name
   | otherwise	
   = getGlobalAvails	`thenRn` \ avail_env ->
     case lookupNameEnv avail_env cls_name of
+	  -- class not in scope; don't fail as later checks will catch this,
+	  -- but just return (bogus) name. Icky.
+	Nothing -> returnRn (mkUnboundName rdr_name)
 	Just (AvailTC _ ns) -> case [n | n <- ns, nameOccName n == occ] of
 				(n:ns)-> ASSERT( null ns ) returnRn n
 				[]    -> failWithRn (mkUnboundName rdr_name)
diff --git a/ghc/compiler/rename/RnNames.lhs b/ghc/compiler/rename/RnNames.lhs
index 432fecf..8fe5622 100644
--- a/ghc/compiler/rename/RnNames.lhs
+++ b/ghc/compiler/rename/RnNames.lhs
@@ -178,7 +178,7 @@ importsFromImportDecl this_mod_name (ImportDecl imp_mod_name from qual_only as_m
 
 	mk_prov name = NonLocalDef (UserImport imp_mod iloc (name `elemNameSet` explicits)) 
 	gbl_env      = mkGlobalRdrEnv qual_mod unqual_imp mk_prov filtered_avails hides deprecs
-	exports      = mkExportAvails qual_mod unqual_imp gbl_env filtered_avails
+	exports      = mkExportAvails qual_mod unqual_imp gbl_env hides filtered_avails
     in
     returnRn (gbl_env, exports)
 \end{code}
@@ -220,7 +220,7 @@ importsFromLocalDecls this_mod decls
 	    -- the defn of a non-deprecated thing, when changing a module's 
 	    -- interface
 
-	exports    = mkExportAvails mod_name unqual_imp gbl_env            avails
+	exports    = mkExportAvails mod_name unqual_imp gbl_env hides avails
     in
     returnRn (gbl_env, exports)
 
@@ -367,8 +367,8 @@ filterImports mod from (Just (want_hiding, import_items)) total_avails
 mkEmptyExportAvails :: ModuleName -> ExportAvails
 mkEmptyExportAvails mod_name = (unitFM mod_name [], emptyNameEnv)
 
-mkExportAvails :: ModuleName -> Bool -> GlobalRdrEnv -> [AvailInfo] -> ExportAvails
-mkExportAvails mod_name unqual_imp gbl_env avails
+mkExportAvails :: ModuleName -> Bool -> GlobalRdrEnv -> [AvailInfo] -> [AvailInfo] -> ExportAvails
+mkExportAvails mod_name unqual_imp gbl_env hides avails 
   = (mod_avail_env, entity_avail_env)
   where
     mod_avail_env = unitFM mod_name unqual_avails 
@@ -383,7 +383,7 @@ mkExportAvails mod_name unqual_imp gbl_env avails
 		  | otherwise      = mapMaybe prune avails
 
     prune (Avail n) | unqual_in_scope n = Just (Avail n)
-    prune (Avail n) | otherwise		= Nothing
+                    | otherwise		= Nothing
     prune (AvailTC n ns) | null uqs     = Nothing
 			 | otherwise    = Just (AvailTC n uqs)
 			 where
@@ -391,8 +391,27 @@ mkExportAvails mod_name unqual_imp gbl_env avails
 
     unqual_in_scope n = unQualInScope gbl_env n
 
-    entity_avail_env = mkNameEnv [ (name,avail) | avail <- avails, 
-			  	   		  name  <- availNames avail]
+
+    entity_avail_env  = mkNameEnv ([ (availName avail,avail) | avail <- effective_avails ] ++
+					-- sigh - need to have the method/field names in
+					-- the environment also, so that export lists
+					-- can be computed precisely (cf. exportsFromAvail)
+    				   [ (name,avail) | avail <- effective_avails,
+				   		    name  <- availNames avail ])
+
+	-- remove 'hides' names from the avail list.
+    effective_avails = foldl wipeOut avails hides
+      where
+        wipeOut as (Avail n)       = mapMaybe (delName n) as
+	wipeOut as (AvailTC n ns)  = foldl wipeOut as (map Avail ns)
+
+	delName x a@(Avail n) 
+	  | n == x    = Nothing
+          | otherwise = Just a
+	delName x (AvailTC n ns) 
+	  = case (filter (/=x) ns) of
+	      [] -> Nothing
+	      xs -> Just (AvailTC n xs)
 
 plusExportAvails ::  ExportAvails ->  ExportAvails ->  ExportAvails
 plusExportAvails (m1, e1) (m2, e2)
-- 
1.7.10.4