From 8feb1e761e28949174e71dc39e5f5775907ac545 Mon Sep 17 00:00:00 2001
From: Alex Shinn <alexshinn@gmail.com>
Date: Mon, 10 Apr 2017 22:36:53 +0900
Subject: [PATCH] alternate approach to handling renamed forward refs

---
 eval.c | 10 +---------
 vm.c   | 12 ++++++++++--
 2 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/eval.c b/eval.c
index f6160827..4fd78faa 100644
--- a/eval.c
+++ b/eval.c
@@ -58,6 +58,7 @@ sexp sexp_warn_undefs_op (sexp ctx, sexp self, sexp_sint_t n, sexp from, sexp to
   if (sexp_envp(from)) from = sexp_env_bindings(from);
   for (x=from; sexp_pairp(x) && x!=to; x=sexp_env_next_cell(x))
     if (sexp_cdr(x) == SEXP_UNDEF && sexp_car(x) != ignore
+        && !sexp_synclop(sexp_car(x))
         && sexp_not(sexp_memq(ctx, sexp_car(x), ignore)))
       sexp_warn(ctx, "reference to undefined variable: ", sexp_car(x));
   return SEXP_VOID;
@@ -150,15 +151,6 @@ sexp sexp_env_cell_define (sexp ctx, sexp env, sexp key,
     if (sexp_car(ls) == key) {
       sexp_cdr(ls) = value;
       return ls;
-    } else if (sexp_cdr(ls) == SEXP_UNDEF &&
-               sexp_synclop(sexp_car(ls)) &&
-               !sexp_synclop(key) &&
-               sexp_identifier_eq(ctx, env, key, sexp_synclo_env(sexp_car(ls)), sexp_synclo_expr(sexp_car(ls)))) {
-      /* handle an undefined renamed reference that would have */
-      /* resolved to this binding, renamed to what we define here */
-      sexp_car(ls) = key;
-      sexp_cdr(ls) = value;
-      return ls;
     }
   sexp_gc_preserve2(ctx, cell, ls);
   sexp_env_push(ctx, env, cell, key, value);
diff --git a/vm.c b/vm.c
index a16af9b4..960d7809 100644
--- a/vm.c
+++ b/vm.c
@@ -1326,8 +1326,16 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
     break;
   case SEXP_OP_GLOBAL_REF:
     _ALIGN_IP();
-    if (sexp_cdr(_WORD0) == SEXP_UNDEF)
-      sexp_raise("undefined variable", sexp_list1(ctx, sexp_car(_WORD0)));
+    if (sexp_cdr(_WORD0) == SEXP_UNDEF) {
+      /* handle renamed forward references by doing a final delayed */
+      /* lookup before throwing an undefined variable error */
+      if (sexp_synclop(sexp_car(_WORD0))) {
+        tmp1 = sexp_env_cell(ctx, sexp_synclo_env(sexp_car(_WORD0)), sexp_synclo_expr(sexp_car(_WORD0)), 0);
+        if (tmp1 != NULL) _WORD0 = tmp1;
+      }
+      if (sexp_cdr(_WORD0) == SEXP_UNDEF)
+        sexp_raise("undefined variable", sexp_list1(ctx, sexp_car(_WORD0)));
+    }
     /* ... FALLTHROUGH ... */
   case SEXP_OP_GLOBAL_KNOWN_REF:
     _ALIGN_IP();