From: simonpj <unknown>
Date: Thu, 14 Feb 2002 14:56:04 +0000 (+0000)
Subject: [project @ 2002-02-14 14:56:04 by simonpj]
X-Git-Tag: Approximately_9120_patches~52
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=6aa2bf20adef309cbf6ff39f4989a96ef0338138;p=ghc-hetmet.git

[project @ 2002-02-14 14:56:04 by simonpj]
---------------------------------------
	Record updates are ok for types involving
	existential data constructors, so long as the
	existential ones aren't the ones updated.
	---------------------------------------

This check was already in the type checker, but
the desugarer had an over-zealous assert.
---

diff --git a/ghc/compiler/deSugar/DsExpr.lhs b/ghc/compiler/deSugar/DsExpr.lhs
index 5560d36..45b02fb 100644
--- a/ghc/compiler/deSugar/DsExpr.lhs
+++ b/ghc/compiler/deSugar/DsExpr.lhs
@@ -454,7 +454,7 @@ dictionaries.
 dsExpr (RecordUpdOut record_expr record_in_ty record_out_ty dicts [])
   = dsExpr record_expr
 
-dsExpr (RecordUpdOut record_expr record_in_ty record_out_ty dicts rbinds)
+dsExpr expr@(RecordUpdOut record_expr record_in_ty record_out_ty dicts rbinds)
   = getSrcLocDs			`thenDs` \ src_loc ->
     dsExpr record_expr	 	`thenDs` \ record_expr' ->
 
@@ -488,7 +488,9 @@ dsExpr (RecordUpdOut record_expr record_in_ty record_out_ty dicts rbinds)
 				    src_loc)
     in
 	-- Record stuff doesn't work for existentials
-    ASSERT( all (not . isExistentialDataCon) data_cons )
+	-- The type checker checks for this, but we need 
+	-- worry only about the constructors that are to be updated
+    ASSERT2( all (not . isExistentialDataCon) cons_to_upd, ppr expr )
 
 	-- It's important to generate the match with matchWrapper,
 	-- and the right hand sides with applications of the wrapper Id