[commit: ghc] master: Fix #7487 (31d8900)

Repository : ssh://darcs.haskell.org//srv/darcs/ghc

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/31d8900dbcf87fc32ac9e3de2ea0ed2039e72ee4

>---------------------------------------------------------------

commit 31d8900dbcf87fc32ac9e3de2ea0ed2039e72ee4
Author: Jose Pedro Magalhaes <[email protected]>
Date:   Fri Dec 7 16:24:06 2012 +0000

    Fix #7487
    
    Signed-off-by: Jose Pedro Magalhaes <[email protected]>

>---------------------------------------------------------------

 compiler/typecheck/TcGenGenerics.lhs |   10 ++++------
 1 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/compiler/typecheck/TcGenGenerics.lhs b/compiler/typecheck/TcGenGenerics.lhs
index d1746fe..0109a99 100644
--- a/compiler/typecheck/TcGenGenerics.lhs
+++ b/compiler/typecheck/TcGenGenerics.lhs
@@ -324,17 +324,15 @@ canDoGenerics1_w rep_tc
     representable ty = case tcSplitTyConApp_maybe ty of
       Nothing -> return Nothing
       -- if it's a type constructor, it has to be representable
-      Just (tc, tc_args) -> do
+      Just (tc, _) -> do
         let n = tyConName tc
         s <- S.get
         -- internally assume that recursive occurrences are OK
         if n `elem` s then return Nothing else do
           S.put (n : s)
-          fmap {-maybe-} (\_ -> bad_app tc) -- don't give the message, just name what wasn't representable
-            `fmap` {-state-} case canDoGenerics tc tc_args of
-              j@(Just _) -> return j
-              -- only check Generic1 if it passes Generic
-              Nothing -> canDoGenerics1_w tc
+          fmap {-maybe-} (\_ -> bad_app tc) -- don't give the message, just
+                                            -- name what wasn't representable
+            `fmap` {-state-} canDoGenerics1_w tc
 
     existential = (ptext . sLit) "must not have existential arguments"
     covariant   = (ptext . sLit) "must not use the last type parameter in a function argument"