From 823e3d7fb3f531077b97c83dcf65c3df9b9493aa Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Tue, 20 Jan 2026 22:39:01 -0500
Subject: [PATCH] xo-reader2: + DExpectTypeSsm [WIP] [NOBUILD]

---
 .../include/xo/reader2/DExpectTypeSsm.hpp     | 64 +++++++++++++++++++
 .../include/xo/reader2/syntaxstatetype.hpp    |  3 +
 xo-reader2/src/reader2/DExpectTypeSsm.cpp     | 44 +++++++++++++
 3 files changed, 111 insertions(+)
 create mode 100644 xo-reader2/include/xo/reader2/DExpectTypeSsm.hpp
 create mode 100644 xo-reader2/src/reader2/DExpectTypeSsm.cpp

diff --git a/xo-reader2/include/xo/reader2/DExpectTypeSsm.hpp b/xo-reader2/include/xo/reader2/DExpectTypeSsm.hpp
new file mode 100644
index 00000000..84654f83
--- /dev/null
+++ b/xo-reader2/include/xo/reader2/DExpectTypeSsm.hpp
@@ -0,0 +1,64 @@
+/** @file expect_type_xs.hpp
+ *
+ * @author Roland Conybeare, Aug 2024
+ **/
+
+#pragma once
+
+#include "SyntaxStateMachine.hpp"
+
+namespace xo {
+    namespace scm {
+        /** @class DExpectTypeSsm
+         *  @brief syntax state-machine for accepting a Schemtika typename-expression
+         *
+         *  Jan 2026
+         *  Placeholder implementation at present.
+         *  Only types are a handful of baked-in values
+         *
+         *  @pre
+         *
+         *  @endpre
+         **/
+        class DExpectTypeSsm {
+        public:
+            DExpectTypeSsm();
+
+            static DExpectTypeSsm * make(DArena & parser_mm);
+
+            static void start(DArena & parser_mm,
+                              //obj<AAllocator> expr_mm,
+                              ParserStateMachine * p_psm);
+
+            virtual const char * get_expect_str() const override;
+
+            virtual void on_symbol_token(const token_type & tk,
+                                         parserstatemachine * p_psm) override;
+
+            /** @defgroup scm-expecttype-ssm-facet syntaxstatemachine facet methods **/
+            ///@{
+
+            /** identifies the ssm implemented here **/
+            syntaxstatetype ssm_type() const noexcept;
+
+            /** text describing expected/allowed input to this ssm in current state.
+             *  Intended to drive error messages.
+             **/
+            std::string_view get_expect_str() const noexcept;
+
+            /** operate state machien for this syntax on incoming symbol-token @p tk
+             *  with overall parser state in @p p_psm
+             **/
+            void on_symbol_token(const Token & tk,
+                                 ParserStateMachine * p_psm);
+
+            ///@}
+
+        private:
+            static std::unique_ptr<expect_type_xs> make();
+        };
+    } /*namespace scm*/
+} /*namespace xo*/
+
+
+/* end expect_type_xs.hpp */
diff --git a/xo-reader2/include/xo/reader2/syntaxstatetype.hpp b/xo-reader2/include/xo/reader2/syntaxstatetype.hpp
index bf3e03f1..8cb48938 100644
--- a/xo-reader2/include/xo/reader2/syntaxstatetype.hpp
+++ b/xo-reader2/include/xo/reader2/syntaxstatetype.hpp
@@ -24,6 +24,9 @@ namespace xo {
             /** expecting a s symbol. See @ref DExpectSymbolSsm **/
             expect_symbol,
 
+            /** expecting a type. See @ref DExpectTypeSsm **/
+            expect_type,
+
             /** handle define-expression. See @ref DDefineSsm **/
             defexpr,
 
diff --git a/xo-reader2/src/reader2/DExpectTypeSsm.cpp b/xo-reader2/src/reader2/DExpectTypeSsm.cpp
new file mode 100644
index 00000000..b034ae23
--- /dev/null
+++ b/xo-reader2/src/reader2/DExpectTypeSsm.cpp
@@ -0,0 +1,44 @@
+/** @file DExpectTypeSsm.cpp
+ *
+ *  @author Roland Conybeare, Aug 2024
+ **/
+
+#include "DExpectTypeSsm.hpp"
+
+namespace xo {
+    namespace scm {
+        DExpectTypeSsm::DExpectTypeSsm()
+        {}
+
+        DExpectTypeSsm *
+        DExpectTypeSsm::make(DArena & mm)
+        {
+            void * mem = mm.alloc(typeseq::id<DArena>(),
+                                  sizeof(DArena));
+
+            return new (mem) DExpectTypeSsm();
+        }
+
+        void
+        DExpectTypeSsm::start(DArena & mm,
+        //obj<AAllocator> expr_mm,
+                          PArserStateMachine * p_psm)
+        {
+            DExpectTypeSsm * expect_type_ssm = DExpectTypeSsm::make(mm);
+
+            auto ssm
+                = with_facet<ASyntaxStateMachine>::mkobj(expect_type_ssm);
+
+            p_psm->push_ssm(ssm);
+        }
+
+        syntaxstatetype
+        DExpectTypeSsm::ssm_type() const noexcept
+        {
+            return syntaxstatetype::expect_type;
+        }
+
+    } /*namespace scm*/
+} /*namespace xo*/
+
+/* end DExpectTypeSsm.cpp */