From f18c33b24937f66d857fe098887bb08991bea721 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Wed, 3 Jul 2024 14:43:34 -0400
Subject: [PATCH] xo-expression: bugfix: ensure in-layer uniqueness of vars

---
 include/xo/expression/Variable.hpp | 5 +++++
 src/expression/Lambda.cpp          | 6 ++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/xo/expression/Variable.hpp b/include/xo/expression/Variable.hpp
index 713da66f..8ca2cb2b 100644
--- a/include/xo/expression/Variable.hpp
+++ b/include/xo/expression/Variable.hpp
@@ -25,6 +25,11 @@ namespace xo {
                 return new Variable(name, var_type);
             }
 
+            /** return copy of x:  same var, different object identity **/
+            static ref::rp<Variable> copy(ref::brw<Variable> x) {
+                return new Variable(x->name(), x->valuetype());
+            }
+
             /** downcast from Expression **/
             static ref::brw<Variable> from(ref::brw<Expression> x) {
                 return ref::brw<Variable>::from(x);
diff --git a/src/expression/Lambda.cpp b/src/expression/Lambda.cpp
index 833c998f..72459fe5 100644
--- a/src/expression/Lambda.cpp
+++ b/src/expression/Lambda.cpp
@@ -103,9 +103,11 @@ namespace xo {
 
                                 auto ix = var_map.find(var->name());
                                 if (ix == var_map.end()) {
-                                    /* add to var_map */
+                                    /* add to var_map,  copy to ensure Variable
+                                     * is unique to layer
+                                     */
 
-                                    var_map[var->name()] = var.get();
+                                    var_map[var->name()] = Variable::copy(var);
 
                                     return var.get();
                                 } else {