xo-reader: prefer xo::bp spelling to xo::ref::brw

xo-reader/src/reader/envframestack.cpp

@@ -66,6 +66,14 @@ namespace xo {
             return nullptr;
         }
 
+        void
+        envframestack::upsert(bp<Variable> x) {
+            /* upsert should always happen in the innermost lexical context.
+             * We are providing new variable binding (perhaps shadowing an existing binding)
+             */
+            this->top_envframe().upsert(x);
+        }
+
         void
         envframestack::print(std::ostream & os) const {
             os << "<envframestack"