From b23e6e00a3f4d02e6095b2033fa0dc97e4176c59 Mon Sep 17 00:00:00 2001
From: sof <unknown>
Date: Tue, 23 Sep 2003 16:52:45 +0000
Subject: [PATCH] [project @ 2003-09-23 16:52:44 by sof] If the user
 explicitly did an instances-only import, i.e., "import Foo
 ()", don't emit an unused-import warning.

---
 ghc/compiler/main/MkIface.lhs        |    4 ++--
 ghc/compiler/rename/RnNames.lhs      |   18 +++++++++++++-----
 ghc/compiler/typecheck/TcRnTypes.lhs |   12 +++++++++---
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/ghc/compiler/main/MkIface.lhs b/ghc/compiler/main/MkIface.lhs
index 0172930..9f31e70 100644
--- a/ghc/compiler/main/MkIface.lhs
+++ b/ghc/compiler/main/MkIface.lhs
@@ -519,8 +519,8 @@ mkUsageInfo hsc_env eps
     pit = eps_PIT eps
     
     import_all mod = case lookupModuleEnv dir_imp_mods mod of
-    			Just (_,imp_all) -> imp_all
-    			Nothing		 -> False
+    			Just (_, Nothing) -> True
+			_                 -> False
     
     -- ent_map groups together all the things imported and used
     -- from a particular module in this package
diff --git a/ghc/compiler/rename/RnNames.lhs b/ghc/compiler/rename/RnNames.lhs
index 9197fd9..d1a4f01 100644
--- a/ghc/compiler/rename/RnNames.lhs
+++ b/ghc/compiler/rename/RnNames.lhs
@@ -193,9 +193,10 @@ importsFromImportDecl this_mod
 	not_self (m, _) = m /= this_mod_name
 
 	import_all = case imp_spec of
-			(Just (False, _)) -> False	-- Imports are spec'd explicitly
-			other	   	  -> True	-- Everything is imported, 
-							-- (or almost everything [hiding])
+			Just (isHid, ls) -- Imports are spec'd explicitly
+			  | not isHid  -> Just (not (null ls)) 
+			_       -> Nothing	-- Everything is imported, 
+						-- (or almost everything [hiding])
 
 	qual_mod_name = case as_mod of
 			  Nothing  	    -> imp_mod_name
@@ -788,14 +789,21 @@ reportUnusedNames gbl_env dus
     direct_import_mods = map (moduleName . fst) 
 			     (moduleEnvElts (imp_mods imports))
 
+    hasEmptyImpList :: ModuleName -> Bool
+    hasEmptyImpList m = 
+       case lookupModuleEnvByName (imp_mods imports) m of
+	 Just (_,Just x) -> not x
+	 _ -> False
+
     -- unused_imp_mods are the directly-imported modules 
     -- that are not mentioned in minimal_imports1
     -- [Note: not 'minimal_imports', because that includes direcly-imported
     --	      modules even if we use nothing from them; see notes above]
     unused_imp_mods = [m | m <- direct_import_mods,
     		       isNothing (lookupFM minimal_imports1 m),
-    		       m /= pRELUDE_Name]
-    
+    		       m /= pRELUDE_Name,
+		       not (hasEmptyImpList m)]
+
     module_unused :: Module -> Bool
     module_unused mod = moduleName mod `elem` unused_imp_mods
 
diff --git a/ghc/compiler/typecheck/TcRnTypes.lhs b/ghc/compiler/typecheck/TcRnTypes.lhs
index 1408eda..47a9ed8 100644
--- a/ghc/compiler/typecheck/TcRnTypes.lhs
+++ b/ghc/compiler/typecheck/TcRnTypes.lhs
@@ -595,10 +595,16 @@ data ImportAvails
 		-- combine stuff coming from different (unqualified) 
 		-- imports of the same module
 
-	imp_mods :: ModuleEnv (Module, Bool),
+	imp_mods :: ModuleEnv (Module, Maybe Bool),
 		-- Domain is all directly-imported modules
-		-- Bool is True if there was an unrestricted import
-		--	(i.e. not a selective list)
+		-- Maybe value answers the question "is the import restricted?"
+		--   Nothing    => unrestricted import (e.g., "import Foo")
+		--   Just True  => restricted import, at least one entity (e.g., "import Foo(x)")
+		--   Just False => fully restricted import (e.g., "import Foo ()")
+		--
+		--  A distinction is made between the first and the third in order
+		--  to more precisely emit warnings about unused imports.
+		--
 		-- We need the Module in the range because we can't get
 		-- 	the keys of a ModuleEnv
 		-- Used 
-- 
1.7.10.4