xo-expression2: symtab scaffold [WIP] [COSMETIC]

xo-expression2/include/xo/expression2/DLocalSymtab.hpp

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+/** @file DLocalSymtab.hpp
+ *
+ *  @author Roland Conybeare, Jan 2026
+ **/
+
+#pragma once
+
+#include "TypeRef.hpp"
+#include "exprtype.hpp"
+#include <xo/reflect/TaggedPtr.hpp>
+#include <xo/gc/GCObject.hpp>
+
+namespace xo {
+    namespace scm {
+        /** @class DLocalSymtab
+         *  @brief Schematika expression respresenting a literal constant
+         **/
+        struct DLocalSymtab {
+        public:
+            using TaggedPtr = xo::reflect::TaggedPtr;
+            using TypeDescr = xo::reflect::TypeDescr;
+            using AGCObject = xo::mm::AGCObject;
+            using typeseq = xo::reflect::typeseq;
+
+        public:
+            explicit DLocalSymtab(obj<AGCObject> value) noexcept;
+
+            bool is_resolved() const noexcept { return typeref_.is_resolved(); }
+
+            exprtype extype() const noexcept { return exprtype::constant; }
+            TypeDescr value_td() const noexcept { return typeref_.td(); }
+            TaggedPtr value_tp() const noexcept { return TaggedPtr(typeref_.td(), value_.data()); }
+
+            TypeRef typeref() const noexcept { return typeref_; }
+            TypeDescr valuetype() const noexcept { return typeref_.td(); }
+            obj<AGCObject> value() const noexcept { return value_; }
+
+            void assign_valuetype(TypeDescr td) noexcept { typeref_.resolve(td); }
+
+        private:
+            static TypeDescr _lookup_td(typeseq tseq);
+
+        private:
+            /** type for value of this expression
+             *  or unification breadcrumb before unification
+             **/
+            TypeRef typeref_;
+            /** literal value **/
+            obj<AGCObject> value_;
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DLocalSymtab.hpp */