[project @ 2005-05-04 11:23:28 by simonpj]

Further wibbles to unused-import reporting; merge to stable

diff --git a/ghc/compiler/rename/RnNames.lhs b/ghc/compiler/rename/RnNames.lhs
index bd4e0f5..2cc62f8 100644 (file)
--- a/ghc/compiler/rename/RnNames.lhs
+++ b/ghc/compiler/rename/RnNames.lhs
@@ -898,16 +898,23 @@ warnDuplicateImports gres
          | red_imp <- imps
          , cov_imp <- take 1 (filter (covers red_imp) imps) ]
 
+       -- "red_imp" is a putative redundant import
+       -- "cov_imp" potentially covers it
+       -- This test decides
     covers red_imp cov_imp
        | red_loc == cov_loc
-       = False         -- The diagonal elements
-       | not $ (is_qual red_imp && is_as red_imp == is_as cov_imp)
-               || not (is_qual cov_imp)
-       = False         -- Covering one doesn't cover!
-       | is_explicit red_imp           -- Tie-breaking
-       = not cov_explicit || red_later
-       | otherwise
-       = not cov_explicit && red_later
+       = False         -- Ignore diagonal elements
+       | not (is_as red_imp == is_as cov_imp)
+       = False         -- They bring into scope different qualified names
+       | not (is_qual red_imp) && is_qual cov_imp
+       = False         -- Covering one doesn't bring unqualified name into scope
+       | is_explicit red_imp   
+       = not cov_explicit      -- Redundant one is explicit and covering one isn't
+         || red_later          -- Both are explicit; tie-break using red_later
+       | otherwise             
+       = not cov_explicit      -- Neither import is explicit
+         && (is_mod red_imp == is_mod cov_imp) -- They import the same module
+         && red_later          -- Tie-break
        where
          cov_explicit = is_explicit cov_imp
          red_loc   = is_loc red_imp