From 900a53da25fc560769e485558b60f36d9b48840d Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 28 Oct 2006 23:55:19 +0000
Subject: [PATCH] fix 'disappeared-binding info for letrecs generated by
 internal definitions

svn: r4693
---
 src/mzscheme/src/syntax.c | 35 +++++++++++++++++++++++++----------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/src/mzscheme/src/syntax.c b/src/mzscheme/src/syntax.c
index 935eb94798..a48e446421 100644
--- a/src/mzscheme/src/syntax.c
+++ b/src/mzscheme/src/syntax.c
@@ -5077,19 +5077,34 @@ do_letrec_syntaxes(const char *where,
   SCHEME_EXPAND_OBSERVE_NEXT_GROUP(rec[drec].observer);
 
   if (names_to_disappear) {
-    /* Need to add renaming for disappeared bindings --- unless
-       they originated for internal definitions, in which case
-       adding the renaming is unnecessary and intereferes with the
-       comparsion (due to limitations of the syntax-object
-       representation for internal definitions). */
-    if (!(origenv->flags & SCHEME_FOR_INTDEF)) {
-      Scheme_Object *l, *a;
+    /* Need to add renaming for disappeared bindings. If they
+       originated for internal definitions, then we need both
+       pre-renamed and renamed, since some might have been
+       expanded to determine definitions. */
+    Scheme_Object *l, *a, *pf = NULL, *pl = NULL;
+
+    if (origenv->flags & SCHEME_FOR_INTDEF) {
       for (l = names_to_disappear; !SCHEME_NULLP(l); l = SCHEME_CDR(l)) {
-	a = SCHEME_CAR(l);
-	a = scheme_add_env_renames(a, stx_env, origenv);
-	SCHEME_CAR(l) = a;
+        a = SCHEME_CAR(l);
+        a = icons(a, scheme_null);
+        if (pl)
+          SCHEME_CDR(pl) = a;
+        else
+          pf = a;
+        pl = a;
       }
     }
+
+    for (l = names_to_disappear; !SCHEME_NULLP(l); l = SCHEME_CDR(l)) {
+      a = SCHEME_CAR(l);
+      a = scheme_add_env_renames(a, stx_env, origenv);
+      SCHEME_CAR(l) = a;
+    }
+
+    if (pf) {
+      SCHEME_CDR(pl) = names_to_disappear;
+      names_to_disappear = pf;
+    }
   }
 
   if (!var_env) {