From c3a91c815c73b8d41bf796db3eca47f776d4b212 Mon Sep 17 00:00:00 2001
From: Gareth Rees <gdr@ravenbrook.com>
Date: Mon, 22 Oct 2012 12:54:35 +0100
Subject: [PATCH] Fix bug in append when the first argument is nil.

Copied from Perforce
 Change: 180004
 ServerID: perforce.ravenbrook.com
---
 mps/example/scheme/scheme.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mps/example/scheme/scheme.c b/mps/example/scheme/scheme.c
index 97d414317e8..14bb43eccd6 100644
--- a/mps/example/scheme/scheme.c
+++ b/mps/example/scheme/scheme.c
@@ -1948,6 +1948,8 @@ static obj_t entry_append(obj_t env, obj_t op_env, obj_t operator, obj_t operand
   }
   if(arg1 != obj_empty)
     error("%s: applied to non-list", operator->operator.name);
+  if(result == obj_empty)
+    return arg2;
   CDR(end) = arg2;
   return result;
 }