From 97236c9f9c903d01d99ada4e440fb9c37c6b27fd Mon Sep 17 00:00:00 2001
From: Manuel M T Chakravarty <chak@cse.unsw.edu.au>
Date: Thu, 19 Oct 2006 18:01:03 +0000
Subject: [PATCH] Fix family instance bug due to the name parent elimination -
 Its important that `isImplicitTyCon' considers   (a)
 associated families to be implicit, but   (b) considers
 family instances *not* to be implicit (for the same reasons
       that a dfun is not implicit).

---
 compiler/types/TyCon.lhs |   29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/compiler/types/TyCon.lhs b/compiler/types/TyCon.lhs
index eb0474b..2e7427c 100644
--- a/compiler/types/TyCon.lhs
+++ b/compiler/types/TyCon.lhs
@@ -13,7 +13,7 @@ module TyCon(
 	tyConPrimRep,
 
 	AlgTyConRhs(..), visibleDataCons, 
-        AlgTyConParent(..), hasParent,
+        AlgTyConParent(..), 
 	SynTyConRhs(..),
 
 	isFunTyCon, isUnLiftedTyCon, isProductTyCon, 
@@ -114,6 +114,8 @@ data TyCon
 					-- argument list (starting from 0).
 					-- NB: Length is less than tyConArity
 					--     if higher kind signature.
+					-- NB: Just _ <=> associated (not
+					--		  toplevel) family
 	
 	algTcSelIds :: [Id],  		-- Its record selectors (empty if none)
 
@@ -279,10 +281,6 @@ data AlgTyConParent = -- An ordinary type constructor has no parent.
 						-- the representation type
 						-- with the type instance
 
-hasParent :: AlgTyConParent -> Bool
-hasParent NoParentTyCon = False
-hasParent _other        = True
-
 data SynTyConRhs
   = OpenSynTyCon Kind	-- Type family: *result* kind given
   | SynonymTyCon Type   -- Mentioning head type vars.  Acts as a template for
@@ -674,11 +672,24 @@ isCoercionTyCon :: TyCon -> Bool
 isCoercionTyCon (CoercionTyCon {}) = True
 isCoercionTyCon other              = False
 
+-- Identifies implicit tycons that, in particular, do not go into interface
+-- files (because they are implicitly reconstructed when the interface is
+-- read).
+--
+-- Note that 
+--
+-- * associated families are implicit, as they are re-constructed from
+--   the class declaration in which they reside, and 
+-- * family instances are *not* implicit as they represent the instance body
+--   (similar to a dfun does that for a class instance).
+--
 isImplicitTyCon :: TyCon -> Bool
-isImplicitTyCon SynTyCon{}                     = False
-isImplicitTyCon AlgTyCon{algTcParent = parent} = hasParent parent
-isImplicitTyCon other                          = True
-        -- catches: FunTyCon, TupleTyCon, PrimTyCon, 
+isImplicitTyCon tycon | isTyConAssoc tycon           = True
+		      | isSynTyCon tycon	     = False
+		      | isAlgTyCon tycon	     = isClassTyCon tycon ||
+						       isTupleTyCon tycon
+isImplicitTyCon _other                               = True
+        -- catches: FunTyCon, PrimTyCon, 
         -- CoercionTyCon, SuperKindTyCon
 \end{code}
 
-- 
1.7.10.4