macros: lexical-var-p: don't report t for specials.

The lexical-var-p function wrongly reports true for locally
rebound special variables, which are not lexical.

* eval.c (special_var_p): Static function moved to avoid
forward declaration.
(lexical_var_p): Bail if sym satisfies special_var_p.
(old_lexical_var_p): New function, copy of old lexical_var_p
before this bugfix.
(eval_init): Conditionally register lexical-var-p as either
lexical_var_p or old_lexical_var_p depending on the compat
value.

* txr.1: Update documentation for lexical-var-p to clarify
that it doesn't report true for specials. Also make note that
it doesn't report true for global lexicals, and likewise that
lexical-fun-p doesn't report global functions.
Added compat note.

1 files changed, 30 insertions, 8 deletions

diff --git a/eval.c b/eval.c
index 5983f2cd..b2e0605a 100644
--- a/eval.c
+++ b/eval.c
@@ -715,10 +715,19 @@ static val reparent_env(val child, val parent)
   return child;
 }
 
+static val special_var_p(val sym)
+{
+  uses_or2;
+  return or2(gethash(special, sym),
+             if2(lisplib_try_load(sym), gethash(special, sym)));
+}
+
 static val lexical_var_p(val menv, val sym)
 {
   if (nilp(menv)) {
     return nil;
+  } else if (special_var_p(sym)) {
+    return nil;
   } else {
     type_check(lit("lexical-var-p"), menv, ENV);
 
@@ -732,6 +741,23 @@ static val lexical_var_p(val menv, val sym)
   }
 }
 
+static val old_lexical_var_p(val menv, val sym)
+{
+  if (nilp(menv)) {
+    return nil;
+  } else {
+    type_check(lit("lexical-var-p"), menv, ENV);
+
+    {
+      val binding = assoc(sym, menv->e.vbindings);
+
+      if (binding)
+        return tnil(cdr(binding) == special_s);
+      return lexical_var_p(menv->e.up_env, sym);
+    }
+  }
+}
+
 static val lexical_fun_p(val menv, val sym)
 {
   if (nilp(menv)) {
@@ -780,13 +806,6 @@ static val mark_special(val sym)
   return sethash(special, sym, t);
 }
 
-static val special_var_p(val sym)
-{
-  uses_or2;
-  return or2(gethash(special, sym),
-             if2(lisplib_try_load(sym), gethash(special, sym)));
-}
-
 static void copy_env_handler(mem_t *ptr)
 {
   val *penv = coerce(val *, ptr);
@@ -6793,7 +6812,10 @@ void eval_init(void)
   reg_fun(intern(lit("env-vbindings"), user_package), func_n1(env_vbindings));
   reg_fun(intern(lit("env-fbindings"), user_package), func_n1(env_fbindings));
   reg_fun(intern(lit("env-next"), user_package), func_n1(env_next));
-  reg_fun(intern(lit("lexical-var-p"), user_package), func_n2(lexical_var_p));
+  reg_fun(intern(lit("lexical-var-p"), user_package),
+          func_n2(if3(opt_compat && opt_compat <= 257,
+                      old_lexical_var_p,
+                      lexical_var_p)));
   reg_fun(intern(lit("lexical-fun-p"), user_package), func_n2(lexical_fun_p));
   reg_fun(intern(lit("lexical-lisp1-binding"), user_package),
           func_n2(lexical_lisp1_binding));