From: simonpj <unknown>
Date: Mon, 4 Jun 2001 16:47:06 +0000 (+0000)
Subject: [project @ 2001-06-04 16:47:06 by simonpj]
X-Git-Tag: Approximately_9120_patches~1812
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=59aaef6b00115e7a30e017362bdbc4475d8637d9;p=ghc-hetmet.git

[project @ 2001-06-04 16:47:06 by simonpj]
----------------------------------
	Fix an existential-constructor bug
	----------------------------------

		MERGE INTO 5.00.2

This fixes a long-standing bug that made the strictness
analyser go into a loop if it met a recursive newtype:

	newtype Void = MkVoid Void
---

diff --git a/ghc/compiler/stranal/SaAbsInt.lhs b/ghc/compiler/stranal/SaAbsInt.lhs
index 47afd99..4cef8c9 100644
--- a/ghc/compiler/stranal/SaAbsInt.lhs
+++ b/ghc/compiler/stranal/SaAbsInt.lhs
@@ -713,6 +713,10 @@ findRecDemand str_fn abs_fn ty
 				-- we don't exploit it yet, so don't bother
 
 	 Just (tycon,_,data_con,cmpnt_tys) 	-- Single constructor case
+	   | isRecursiveTyCon tycon		-- Recursive data type; don't unpack
+	   ->	wwStrict			-- 	(this applies to newtypes too:
+						--	e.g.  data Void = MkVoid Void)
+
 	   | isNewTyCon tycon 			-- A newtype!
 	   ->	ASSERT( null (tail cmpnt_tys) )
 		let
@@ -721,7 +725,6 @@ findRecDemand str_fn abs_fn ty
 		wwUnpackNew demand
 
 	   |  null compt_strict_infos 		-- A nullary data type
-	   || isRecursiveTyCon tycon		-- Recursive data type; don't unpack
 	   ->	wwStrict
 
 	   | otherwise				-- Some other data type