diff --git a/include/xo/reader2/DExpectFormalArgSsm.hpp b/include/xo/reader2/DExpectFormalArgSsm.hpp
index 51eb6536..5308c701 100644
--- a/include/xo/reader2/DExpectFormalArgSsm.hpp
+++ b/include/xo/reader2/DExpectFormalArgSsm.hpp
@@ -5,7 +5,7 @@
 
 #pragma once
 
-#include "SyntaxStateMachine.hpp"
+#include "DSyntaxStateMachine.hpp"
 //#include <xo/arena/DArena.hpp>
 //#include "exprstate.hpp"
 
@@ -44,8 +44,9 @@ namespace xo {
         /** @class expect_formal_xs
          *  @brief parser state-machine for a typed formal parameter
          **/
-        class DExpectFormalArgSsm {
+        class DExpectFormalArgSsm : public DSyntaxStateMachine<DExpectFormalArgSsm> {
         public:
+            using Super = DSyntaxStateMachine<DExpectFormalArgSsm>;
             using TypeDescr = xo::reflect::TypeDescr;
             using DArena = xo::mm::DArena;
             using ppindentinfo = xo::print::ppindentinfo;
@@ -70,6 +71,8 @@ namespace xo {
             /** @defgroup scm-expectformalargssm-methods general methods **/
             ///@{
 
+            const char * ssm_classname() const noexcept { return "DExpectFormalArgSsm"; }
+
             /** update state on incoming colon token @p tk;
              *  with overall parser state in @p p_psm
              **/
@@ -104,32 +107,6 @@ namespace xo {
             void on_parsed_typedescr(TypeDescr td,
                                      ParserStateMachine * p_psm);
 
-            /** consume parsed formal (name,type) = (@p sym, @p td) from nested ssm
-             *  with overall parser state in @p p_psm.
-             *  (In practice not reachable)
-             **/
-            void on_parsed_formal(const DUniqueString * sym,
-                                  TypeDescr td,
-                                  ParserStateMachine * p_psm);
-
-            /** consume formal params @p arglist from completed nested ssm,
-             *  with overall parser state in @p p_psm.
-             **/
-            void on_parsed_formal_arglist(DArray * arglist,
-                                          ParserStateMachine * p_psm);
-
-            /** update state on parsed expression emitted by nested ssm
-             *  with overall parser state in @p p_psm
-             **/
-            void on_parsed_expression(obj<AExpression> expr,
-                                      ParserStateMachine * p_psm);
-
-            /** update state on parsed expression, along with following semicolon,
-             *  emitted by nested ssm with overall parser state in @p p_psm
-             **/
-            void on_parsed_expression_with_semicolon(obj<AExpression> expr,
-                                                     ParserStateMachine * p_psm);
-
             ///@}
             /** @defgroup scm-expectformalargssm-printable-facet printable facet methods **/
             ///@{
@@ -139,26 +116,12 @@ namespace xo {
 
             ///@}
 
-#ifdef NOT_YET
-
-            virtual void on_symbol(const std::string & symbol_name,
-                                   parserstatemachine * p_psm) override;
-
-            // virtual void on_comma_token(...) override;
-
 #ifdef PROBABLY_NOT
             virtual void on_rightparen_token(const token_type & tk,
                                              exprstatestack * p_stack,
                                              rp<Expression> * p_emit_expr) override;
 #endif
 
-            virtual void on_typedescr(TypeDescr td,
-                                      parserstatemachine * p_psm) override;
-
-        private:
-            static std::unique_ptr<expect_formal_xs> make();
-#endif
-
         private:
             /** parsing state-machine state **/
             formalstatetype fstate_ = formalstatetype::formal_0;
diff --git a/src/reader2/DExpectFormalArgSsm.cpp b/src/reader2/DExpectFormalArgSsm.cpp
index 4aaf7c4b..d865cd71 100644
--- a/src/reader2/DExpectFormalArgSsm.cpp
+++ b/src/reader2/DExpectFormalArgSsm.cpp
@@ -138,9 +138,7 @@ namespace xo {
                 break;
             }
 
-            p_psm->illegal_input_on_token("DExpectFormalArgSsm::on_token",
-                                          tk,
-                                          this->get_expect_str());
+            Super::on_token(tk, p_psm);
         }
 
         void
@@ -156,9 +154,7 @@ namespace xo {
                 return;
             }
 
-            p_psm->illegal_input_on_token("DExpectFormalArgSsm::on_colon_token",
-                                          tk,
-                                          this->get_expect_str());
+            Super::on_token(tk, p_psm);
         }
 
         void
@@ -175,9 +171,7 @@ namespace xo {
                 return;
             }
 
-            p_psm->illegal_input_on_symbol("DExpectFormalArgSsm::on_parsed_symbol",
-                                           sym,
-                                           this->get_expect_str());
+            Super::on_parsed_symbol(sym, p_psm);
         }
 
         void
@@ -193,50 +187,7 @@ namespace xo {
                 return;
             }
 
-            p_psm->illegal_input_on_typedescr("DExpectFormalArgSsm::on_parsed_typedescr",
-                                              td,
-                                              this->get_expect_str());
-        }
-
-        void
-        DExpectFormalArgSsm::on_parsed_formal(const DUniqueString * param_name,
-                                              TypeDescr param_type,
-                                              ParserStateMachine * p_psm)
-        {
-            // NOTE: (param_name,param_type) *produced* by this SSM,
-            //       but never *consumed*
-
-            p_psm->illegal_parsed_formal("DExpectFormalArgSsm::on_parsed_formal",
-                                         param_name,
-                                         param_type,
-                                         this->get_expect_str());
-        }
-
-        void
-        DExpectFormalArgSsm::on_parsed_formal_arglist(DArray * arglist,
-                                                      ParserStateMachine * p_psm)
-        {
-            p_psm->illegal_parsed_formal_arglist("DExpectFormalArgSsm::on_parsed_formal_arglist",
-                                                 arglist,
-                                                 this->get_expect_str());
-        }
-
-        void
-        DExpectFormalArgSsm::on_parsed_expression(obj<AExpression> expr,
-                                                  ParserStateMachine * p_psm)
-        {
-            p_psm->illegal_parsed_expression("DExpectFormalArgSsm::on_parsed_expression",
-                                               expr,
-                                               this->get_expect_str());
-        }
-
-        void
-        DExpectFormalArgSsm::on_parsed_expression_with_semicolon(obj<AExpression> expr,
-                                                                 ParserStateMachine * p_psm)
-        {
-            p_psm->illegal_parsed_expression("DExpectFormalArgSsm::on_parsed_expression_with_semicolon",
-                                             expr,
-                                             this->get_expect_str());
+            Super::on_parsed_typedescr(td, p_psm);
         }
 
 #ifdef NOT_YET