From 2720c6609b7b7f6002dd0ffcc31ed0363f1208d9 Mon Sep 17 00:00:00 2001
From: simonpj <unknown>
Date: Tue, 28 Oct 2003 13:16:01 +0000
Subject: [PATCH] [project @ 2003-10-28 13:15:58 by simonpj] Wibbles about
 argument variance

---
 ghc/compiler/parser/RdrHsSyn.lhs     |    2 ++
 ghc/compiler/typecheck/TcTyDecls.lhs |   25 ++-----------------------
 ghc/compiler/types/TyCon.lhs         |    6 +++---
 3 files changed, 7 insertions(+), 26 deletions(-)

diff --git a/ghc/compiler/parser/RdrHsSyn.lhs b/ghc/compiler/parser/RdrHsSyn.lhs
index feee920..7d51a54 100644
--- a/ghc/compiler/parser/RdrHsSyn.lhs
+++ b/ghc/compiler/parser/RdrHsSyn.lhs
@@ -360,6 +360,8 @@ hsIfaceDecl (TyClD decl@(TyData {}))
 		ifCtxt = hsIfaceCtxt (tcdCtxt decl),
 		ifCons = Unknown, ifRec = NonRecursive,
 		ifVrcs = [], ifGeneric = False }
+	-- I'm not sure that [] is right for ifVrcs, but
+	-- since we don't use them I'm not going to fiddle
 
 hsIfaceDecl (TyClD decl@(ClassDecl {}))
   = IfaceClass { ifName = rdrNameOcc (tcdName decl), 
diff --git a/ghc/compiler/typecheck/TcTyDecls.lhs b/ghc/compiler/typecheck/TcTyDecls.lhs
index e67cabe..46a7892 100644
--- a/ghc/compiler/typecheck/TcTyDecls.lhs
+++ b/ghc/compiler/typecheck/TcTyDecls.lhs
@@ -333,11 +333,7 @@ calcTyConArgVrcs tyclss
     initial_oi :: NameEnv (TyCon, ArgVrcs)
     initial_oi = mkNameEnv [(tyConName tc, (tc, initial tc))
 			   | tc <- tycons]
-    initial tc = if isAlgTyCon tc && isNothing (tyConDataCons_maybe tc) then
-                         -- make pessimistic assumption (and warn)
-                         abstractVrcs tc
-                       else
-                         replicate (tyConArity tc) (False,False)
+    initial tc = replicate (tyConArity tc) (False,False)
 
     tcaoFix :: NameEnv (TyCon, ArgVrcs)   -- initial ArgVrcs per tycon
 	    -> NameEnv (TyCon, ArgVrcs)   -- fixpointed ArgVrcs per tycon
@@ -358,10 +354,7 @@ calcTyConArgVrcs tyclss
 	     -> ArgVrcs                   -- new ArgVrcs for tycon
 
     tcaoIter oi tc | isAlgTyCon tc
-      = if null data_cons then
-	    abstractVrcs tc		-- Data types with no constructors
-	else
-            map (\v -> anyVrc (vrcInTy (lookup oi) v) argtys) vs
+      = map (\v -> anyVrc (vrcInTy (lookup oi) v) argtys) vs
       where
        	data_cons = tyConDataCons tc
        	vs        = tyConTyVars tc
@@ -376,20 +369,6 @@ calcTyConArgVrcs tyclss
 			Just (_, pms) -> pms
 			Nothing	      -> tyConArgVrcs tc
 	 -- We use the already-computed result for tycons not in this SCC
-
-
-abstractVrcs :: TyCon -> ArgVrcs
-abstractVrcs tc = 
-#ifdef DEBUG
-                  pprTrace "Vrc: abstract tycon:" (ppr tc) $
-#endif
-                  warn_abstract_vrcs `seq` replicate (tyConArity tc) (True,True)
-
-warn_abstract_vrcs
--- we pull the message out as a CAF so the warning only appears *once*
-  = trace ("WARNING: tyConArgVrc info inaccurate due to unavailable constructors.\n"
-        ++ "         Use -fno-prune-tydecls to fix.") $
-                ()
 \end{code}
 
 
diff --git a/ghc/compiler/types/TyCon.lhs b/ghc/compiler/types/TyCon.lhs
index 9b40a44..dc81d81 100644
--- a/ghc/compiler/types/TyCon.lhs
+++ b/ghc/compiler/types/TyCon.lhs
@@ -195,8 +195,8 @@ data DataConDetails datacon
   = DataCons [datacon]	-- Its data constructors, with fully polymorphic types
 			-- A type can have zero constructors
 
-  | Unknown		-- We're importing this data type from an hi-boot file
-			-- and we don't know what its constructors are
+  | Unknown		-- Used only when We're importing this data type from an 
+			-- hi-boot file, so we don't know what its constructors are
 
 visibleDataCons (DataCons cs) = cs
 visibleDataCons other	      = []
@@ -452,7 +452,7 @@ tyConHasGenerics other				 = False	-- Synonyms
 tyConDataConDetails :: TyCon -> DataConDetails DataCon
 tyConDataConDetails (AlgTyCon {dataCons = cons}) = cons
 tyConDataConDetails (TupleTyCon {dataCon = con}) = DataCons [con]
-tyConDataConDetails other			 = Unknown
+tyConDataConDetails other			 = pprPanic "tyConDataConDetails" (ppr other)
 
 tyConDataCons :: TyCon -> [DataCon]
 -- It's convenient for tyConDataCons to return the
-- 
1.7.10.4