xo-reader2 stack: top-level lambda w/ apply parses

include/xo/expression2/DVarRef.hpp

@@ -0,0 +1,84 @@
+/** @file DVarRef.hpp
+ *
+ *  @author Roland Conybeare, Feb 2026
+ **/
+
+#pragma once
+
+#include "Variable.hpp"
+
+namespace xo {
+    namespace scm {
+
+        /** @class DVarRef
+         *  @brief syntax for a variable reference
+         *
+         *  Reference to a known variable possibly
+         *  defined in another scope.
+         *  For non-local non-global variables,
+         **/
+        class DVarRef {
+        public:
+            using ppindentinfo = xo::print::ppindentinfo;
+            using ACollector = xo::mm::ACollector;
+            using AAllocator = xo::mm::AAllocator;
+            using TypeDescr = xo::reflect::TypeDescr;
+
+        public:
+            DVarRef(DVariable * vardef,
+                    Binding path);
+
+            /** create instance
+             *  @p mm      memory allocator
+             *  @p vardef  variable definition (name, typeref, binding)
+             *  @p link    number of lexical scope boundaries we must cross
+             *             to reach scope containing @p vardef.
+             *             Only relevant for non-global vardef
+             **/
+            static DVarRef * make(obj<AAllocator> mm,
+                                  DVariable * vardef,
+                                  int32_t link);
+
+            const DUniqueString * name() const;
+            Binding path() const { return path_; }
+
+            /** @defgroup scm-variable-expression-facet **/
+            ///@{
+
+            exprtype extype() const noexcept { return exprtype::varref; }
+            TypeRef typeref() const noexcept;
+            TypeDescr valuetype() const noexcept;
+            void assign_valuetype(TypeDescr td) noexcept;
+
+            ///@}
+            /** @defgroup scm-variable-gcobject-facet **/
+            ///@{
+
+            size_t shallow_size() const noexcept;
+            DVarRef * shallow_copy(obj<AAllocator> mm) const noexcept;
+            size_t forward_children(obj<ACollector> gc) noexcept;
+
+            ///@}
+            /** @defgroup scm-variable-printable-facet **/
+            ///@{
+
+            bool pretty(const ppindentinfo & ppii) const;
+
+            ///@}
+
+        private:
+            /** variable definition. Created in the sccope where variable introduced.
+             *  Has an associated @ref Binding, but that binding is only correct
+             *  around any nested scopes.
+             **/
+            DVariable * vardef_ = nullptr;
+
+            /** at runtime: navigate environemnt via this path to get
+             *  runtime memory location for this variable
+             **/
+            Binding path_;
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DVarRef.hpp */