Make CoreTidy retain deadness info (better -ddump-simpl)

[ghc-hetmet.git] / compiler / coreSyn / CoreTidy.lhs

diff --git a/compiler/coreSyn/CoreTidy.lhs b/compiler/coreSyn/CoreTidy.lhs
index 3f84021..586f032 100644 (file)
--- a/compiler/coreSyn/CoreTidy.lhs
+++ b/compiler/coreSyn/CoreTidy.lhs
@@ -176,15 +176,21 @@ tidyIdBndr env@(tidy_env, var_env) id
        -- though we could extract it from the Id
        -- 
        -- All nested Ids now have the same IdInfo, namely vanillaIdInfo,
-       -- which should save some space.
+       -- which should save some space; except that we hang onto dead-ness
+       -- (at the moment, solely to make printing tidy core nicer)
        -- But note that tidyLetBndr puts some of it back.
-        ty'              = tidyType env (idType id)
-       id'               = mkUserLocal occ' (idUnique id) ty' noSrcSpan
-                               `setIdInfo` vanillaIdInfo
-       var_env'          = extendVarEnv var_env id id'
+        ty'      = tidyType env (idType id)
+        name'    = mkInternalName (idUnique id) occ' noSrcSpan
+       id'      = mkLocalIdWithInfo name' ty' new_info
+       var_env' = extendVarEnv var_env id id'
+        new_info | isDeadOcc (idOccInfo id) = deadIdInfo
+                | otherwise                = vanillaIdInfo
     in
      ((tidy_env', var_env'), id')
    }
+
+deadIdInfo :: IdInfo
+deadIdInfo = vanillaIdInfo `setOccInfo` IAmDead
 \end{code}
 
 \begin{code}