diff --git a/idl/SyntaxStateMachine.json5 b/idl/SyntaxStateMachine.json5
index fba93437..716b7268 100644
--- a/idl/SyntaxStateMachine.json5
+++ b/idl/SyntaxStateMachine.json5
@@ -82,6 +82,15 @@
                 {type: "ParserStateMachine *", name: "p_psm"},
             ],
         },
+        {
+            name: "on_parsed_formal_arglist",
+            doc: ["consume formal arglist emitted by nested ssm"],
+            return_type: "void",
+            args: [
+                {type: "DArray *", name: "arglist"},
+                {type: "ParserStateMachine *", name: "p_psm"},
+            ],
+        },
         {
             name: "on_parsed_expression",
             doc: ["update state machine for incoming parsed expression @p expr"],
diff --git a/include/xo/reader2/DDefineSsm.hpp b/include/xo/reader2/DDefineSsm.hpp
index bf0a3ffb..ebd454c0 100644
--- a/include/xo/reader2/DDefineSsm.hpp
+++ b/include/xo/reader2/DDefineSsm.hpp
@@ -202,6 +202,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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 for this syntax after parsing an expression @p expr,
              *  overall parser state in @p p_psm
              **/
diff --git a/include/xo/reader2/DExpectExprSsm.hpp b/include/xo/reader2/DExpectExprSsm.hpp
index 8e51124d..ae4154ef 100644
--- a/include/xo/reader2/DExpectExprSsm.hpp
+++ b/include/xo/reader2/DExpectExprSsm.hpp
@@ -142,6 +142,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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 for this syntax after parsing an expression @p expr,
              *  overall parser state in @p p_psm
              **/
diff --git a/include/xo/reader2/DExpectFormalArgSsm.hpp b/include/xo/reader2/DExpectFormalArgSsm.hpp
index ee5eb0ea..51eb6536 100644
--- a/include/xo/reader2/DExpectFormalArgSsm.hpp
+++ b/include/xo/reader2/DExpectFormalArgSsm.hpp
@@ -112,6 +112,12 @@ namespace xo {
                                   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
              **/
diff --git a/include/xo/reader2/DExpectFormalArglistSsm.hpp b/include/xo/reader2/DExpectFormalArglistSsm.hpp
index 2898fa7c..289b7cf5 100644
--- a/include/xo/reader2/DExpectFormalArglistSsm.hpp
+++ b/include/xo/reader2/DExpectFormalArglistSsm.hpp
@@ -114,6 +114,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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
              **/
@@ -144,7 +150,7 @@ namespace xo {
         private:
             /** parsing state-machine state **/
             formalarglstatetype fastate_ = formalarglstatetype::argl_0;
-            /** populate with (parmaeter-name, parameter-type) list
+            /** populate with (parameter-name, parameter-type) list
              *  as they're encountered.
              *
              *  Not using flexible array here since we don't know size at construction time
diff --git a/include/xo/reader2/DExpectSymbolSsm.hpp b/include/xo/reader2/DExpectSymbolSsm.hpp
index 080380b9..accfa936 100644
--- a/include/xo/reader2/DExpectSymbolSsm.hpp
+++ b/include/xo/reader2/DExpectSymbolSsm.hpp
@@ -85,6 +85,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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 for this syntax after parsing an expression @p expr
              *  in nested state machine.
              *  (provided to satisfy ASyntaxStateMachine api. not reachable)
diff --git a/include/xo/reader2/DExpectTypeSsm.hpp b/include/xo/reader2/DExpectTypeSsm.hpp
index 3ca99815..729eac83 100644
--- a/include/xo/reader2/DExpectTypeSsm.hpp
+++ b/include/xo/reader2/DExpectTypeSsm.hpp
@@ -136,6 +136,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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);
+
             /** operate state machine for this syntax on receiving expression
              *  from nested parser.
              *  (provided to satisfy ASyntaxStateMachine api. not reachable)
diff --git a/include/xo/reader2/DExprSeqState.hpp b/include/xo/reader2/DExprSeqState.hpp
index c718cbef..a7b19c28 100644
--- a/include/xo/reader2/DExprSeqState.hpp
+++ b/include/xo/reader2/DExprSeqState.hpp
@@ -145,6 +145,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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 for this syntax on parsed expression @p expr
              *  from nested ssm.
              *  overall parser state in @p p_psm
diff --git a/include/xo/reader2/DIfElseSsm.hpp b/include/xo/reader2/DIfElseSsm.hpp
index 647a5e34..62f7d137 100644
--- a/include/xo/reader2/DIfElseSsm.hpp
+++ b/include/xo/reader2/DIfElseSsm.hpp
@@ -159,6 +159,12 @@ namespace xo {
                                   TypeDescr param_type,
                                   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 for this syntax after parsing an expression @p expr,
              *  overall parser state in @p p_psm.
              **/
diff --git a/include/xo/reader2/DLambdaSsm.hpp b/include/xo/reader2/DLambdaSsm.hpp
index 69cb3322..8800ad1c 100644
--- a/include/xo/reader2/DLambdaSsm.hpp
+++ b/include/xo/reader2/DLambdaSsm.hpp
@@ -123,6 +123,12 @@ namespace xo {
                                   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 this ssm when nested parser
              *  emits expression @p expr
              **/
diff --git a/include/xo/reader2/DProgressSsm.hpp b/include/xo/reader2/DProgressSsm.hpp
index fa0ec733..ae9c2244 100644
--- a/include/xo/reader2/DProgressSsm.hpp
+++ b/include/xo/reader2/DProgressSsm.hpp
@@ -173,6 +173,8 @@ namespace xo {
             void on_parsed_formal(const DUniqueString * param_name,
                                   TypeDescr param_type,
                                   ParserStateMachine * p_psm);
+            void on_parsed_formal_arglist(DArray * arglist,
+                                          ParserStateMachine * p_psm);
             void on_parsed_expression(obj<AExpression>,
                                       ParserStateMachine * p_psm);
             void on_parsed_expression_with_semicolon(obj<AExpression> expr,
diff --git a/include/xo/reader2/ParserStateMachine.hpp b/include/xo/reader2/ParserStateMachine.hpp
index 74f27876..1c5729a6 100644
--- a/include/xo/reader2/ParserStateMachine.hpp
+++ b/include/xo/reader2/ParserStateMachine.hpp
@@ -9,6 +9,7 @@
 #include <xo/expression2/DVariable.hpp>
 #include <xo/expression2/StringTable.hpp>
 #include <xo/tokenizer2/Token.hpp>
+#include <xo/object2/DArray.hpp>
 #include <xo/alloc2/Allocator.hpp>
 #include <xo/arena/DArena.hpp>
 
@@ -103,11 +104,16 @@ namespace xo {
             void on_parsed_typedescr(TypeDescr td);
 
             /** update state to consume param (name, value) emitted by
-             *  nested (but not popped) parsing state
+             *  nested (expired) parsing state
              **/
             void on_parsed_formal(const DUniqueString * param_name,
                                   TypeDescr param_type);
 
+            /** update state to consume formal arugment list
+             *  emitted by nested (expired) parsing state
+             **/
+            void on_parsed_formal_arglist(DArray * arglist);
+
             /** update state to respond to parsed expression @p expr
              *  (from nested parsing state)
              **/
@@ -178,6 +184,12 @@ namespace xo {
                                        TypeDescr param_type,
                                        std::string_view expect_str);
 
+            /** @p arglist stores obj<AGCObject,DVariable> pointers.
+             **/
+            void illegal_parsed_formal_arglist(std::string_view ssm_name,
+                                               DArray * arglist,
+                                               std::string_view expect_str);
+
             /** report illegal parsed expression from nested ssm.
              *  Introducing as placeholder; not clear if this will be reachable
              *  in full parser
diff --git a/include/xo/reader2/ssm/ASyntaxStateMachine.hpp b/include/xo/reader2/ssm/ASyntaxStateMachine.hpp
index 6cc3b829..b9df6e6d 100644
--- a/include/xo/reader2/ssm/ASyntaxStateMachine.hpp
+++ b/include/xo/reader2/ssm/ASyntaxStateMachine.hpp
@@ -65,6 +65,8 @@ public:
     virtual void on_parsed_typedescr(Opaque data, TypeDescr td, ParserStateMachine * p_psm)  = 0;
     /** operate state machine for formal emitted by nested ssm **/
     virtual void on_parsed_formal(Opaque data, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm)  = 0;
+    /** consume formal arglist emitted by nested ssm **/
+    virtual void on_parsed_formal_arglist(Opaque data, DArray * arglist, ParserStateMachine * p_psm)  = 0;
     /** update state machine for incoming parsed expression @p expr **/
     virtual void on_parsed_expression(Opaque data, obj<AExpression> expr, ParserStateMachine * p_psm)  = 0;
     /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_Any.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_Any.hpp
index 3faa0f67..e239c46b 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_Any.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_Any.hpp
@@ -64,6 +64,7 @@ namespace scm {
         [[noreturn]] void on_parsed_symbol(Opaque, std::string_view, ParserStateMachine *)  override;
         [[noreturn]] void on_parsed_typedescr(Opaque, TypeDescr, ParserStateMachine *)  override;
         [[noreturn]] void on_parsed_formal(Opaque, const DUniqueString *, TypeDescr, ParserStateMachine *)  override;
+        [[noreturn]] void on_parsed_formal_arglist(Opaque, DArray *, ParserStateMachine *)  override;
         [[noreturn]] void on_parsed_expression(Opaque, obj<AExpression>, ParserStateMachine *)  override;
         [[noreturn]] void on_parsed_expression_with_semicolon(Opaque, obj<AExpression>, ParserStateMachine *)  override;
 
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DDefineSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DDefineSsm.hpp
index f4d0da9d..42616a38 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DDefineSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DDefineSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DDefineSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DDefineSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DDefineSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DDefineSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectExprSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectExprSsm.hpp
index 3ff00e07..53669967 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectExprSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectExprSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExpectExprSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExpectExprSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExpectExprSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExpectExprSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArgSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArgSsm.hpp
index adce6eb9..99d6c9a9 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArgSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArgSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExpectFormalArgSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExpectFormalArgSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExpectFormalArgSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExpectFormalArgSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArglistSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArglistSsm.hpp
index b8a3b416..570ee3a4 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArglistSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectFormalArglistSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExpectFormalArglistSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExpectFormalArglistSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExpectFormalArglistSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExpectFormalArglistSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectSymbolSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectSymbolSsm.hpp
index d778e293..2003db8a 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectSymbolSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectSymbolSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExpectSymbolSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExpectSymbolSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExpectSymbolSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExpectSymbolSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectTypeSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectTypeSsm.hpp
index 9d6f153a..acb752fe 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectTypeSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExpectTypeSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExpectTypeSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExpectTypeSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExpectTypeSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExpectTypeSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DExprSeqState.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DExprSeqState.hpp
index d958f1f8..3c160d00 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DExprSeqState.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DExprSeqState.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DExprSeqState & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DExprSeqState & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DExprSeqState & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DExprSeqState & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DIfElseSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DIfElseSsm.hpp
index 88a8b7d8..462172d2 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DIfElseSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DIfElseSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DIfElseSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DIfElseSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DIfElseSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DIfElseSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DLambdaSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DLambdaSsm.hpp
index 02582d0b..fa0cb0a2 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DLambdaSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DLambdaSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DLambdaSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DLambdaSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DLambdaSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DLambdaSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_DProgressSsm.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_DProgressSsm.hpp
index ee2dfbaf..ddd0c06e 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_DProgressSsm.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_DProgressSsm.hpp
@@ -62,6 +62,8 @@ namespace xo {
             static void on_parsed_typedescr(DProgressSsm & self, TypeDescr td, ParserStateMachine * p_psm);
             /** operate state machine for formal emitted by nested ssm **/
             static void on_parsed_formal(DProgressSsm & self, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm);
+            /** consume formal arglist emitted by nested ssm **/
+            static void on_parsed_formal_arglist(DProgressSsm & self, DArray * arglist, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr **/
             static void on_parsed_expression(DProgressSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm);
             /** update state machine for incoming parsed expression @p expr followed by semicolon **/
diff --git a/include/xo/reader2/ssm/ISyntaxStateMachine_Xfer.hpp b/include/xo/reader2/ssm/ISyntaxStateMachine_Xfer.hpp
index 51ab0f30..e89357ab 100644
--- a/include/xo/reader2/ssm/ISyntaxStateMachine_Xfer.hpp
+++ b/include/xo/reader2/ssm/ISyntaxStateMachine_Xfer.hpp
@@ -64,6 +64,9 @@ namespace scm {
         void on_parsed_formal(Opaque data, const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm)  override {
             return I::on_parsed_formal(_dcast(data), param_name, param_type, p_psm);
         }
+        void on_parsed_formal_arglist(Opaque data, DArray * arglist, ParserStateMachine * p_psm)  override {
+            return I::on_parsed_formal_arglist(_dcast(data), arglist, p_psm);
+        }
         void on_parsed_expression(Opaque data, obj<AExpression> expr, ParserStateMachine * p_psm)  override {
             return I::on_parsed_expression(_dcast(data), expr, p_psm);
         }
diff --git a/include/xo/reader2/ssm/RSyntaxStateMachine.hpp b/include/xo/reader2/ssm/RSyntaxStateMachine.hpp
index 3de33f8e..0e2b8636 100644
--- a/include/xo/reader2/ssm/RSyntaxStateMachine.hpp
+++ b/include/xo/reader2/ssm/RSyntaxStateMachine.hpp
@@ -68,6 +68,9 @@ public:
     void on_parsed_formal(const DUniqueString * param_name, TypeDescr param_type, ParserStateMachine * p_psm)  {
         return O::iface()->on_parsed_formal(O::data(), param_name, param_type, p_psm);
     }
+    void on_parsed_formal_arglist(DArray * arglist, ParserStateMachine * p_psm)  {
+        return O::iface()->on_parsed_formal_arglist(O::data(), arglist, p_psm);
+    }
     void on_parsed_expression(obj<AExpression> expr, ParserStateMachine * p_psm)  {
         return O::iface()->on_parsed_expression(O::data(), expr, p_psm);
     }
diff --git a/src/reader2/DDefineSsm.cpp b/src/reader2/DDefineSsm.cpp
index 65df6349..1636c4b0 100644
--- a/src/reader2/DDefineSsm.cpp
+++ b/src/reader2/DDefineSsm.cpp
@@ -715,6 +715,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DDefineSsm::on_parsed_formal_arglist(DArray * arglist,
+                                             ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DDefineSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DDefineSsm::on_parsed_expression(obj<AExpression> expr,
                                          ParserStateMachine * p_psm)
diff --git a/src/reader2/DExpectExprSsm.cpp b/src/reader2/DExpectExprSsm.cpp
index 2a836e87..c7fe298a 100644
--- a/src/reader2/DExpectExprSsm.cpp
+++ b/src/reader2/DExpectExprSsm.cpp
@@ -365,6 +365,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DExpectExprSsm::on_parsed_formal_arglist(DArray * arglist,
+                                                 ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DExpectExprSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DExpectExprSsm::on_parsed_expression(obj<AExpression> expr,
                                              ParserStateMachine * p_psm)
diff --git a/src/reader2/DExpectFormalArgSsm.cpp b/src/reader2/DExpectFormalArgSsm.cpp
index eb174fc9..4aaf7c4b 100644
--- a/src/reader2/DExpectFormalArgSsm.cpp
+++ b/src/reader2/DExpectFormalArgSsm.cpp
@@ -212,6 +212,15 @@ namespace xo {
                                          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)
diff --git a/src/reader2/DExpectFormalArglistSsm.cpp b/src/reader2/DExpectFormalArglistSsm.cpp
index 676e0a9e..63113f4e 100644
--- a/src/reader2/DExpectFormalArglistSsm.cpp
+++ b/src/reader2/DExpectFormalArglistSsm.cpp
@@ -241,6 +241,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DExpectFormalArglistSsm::on_parsed_formal_arglist(DArray * arglist,
+                                                          ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DExpectFormalArglistSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DExpectFormalArglistSsm::on_parsed_expression(obj<AExpression> expr,
                                                      ParserStateMachine * p_psm)
diff --git a/src/reader2/DExpectSymbolSsm.cpp b/src/reader2/DExpectSymbolSsm.cpp
index cee3a08c..60985cae 100644
--- a/src/reader2/DExpectSymbolSsm.cpp
+++ b/src/reader2/DExpectSymbolSsm.cpp
@@ -84,6 +84,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DExpectSymbolSsm::on_parsed_formal_arglist(DArray * arglist,
+                                                   ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DExpectSymbolSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DExpectSymbolSsm::on_parsed_expression(obj<AExpression> expr,
                                                ParserStateMachine * p_psm)
diff --git a/src/reader2/DExpectTypeSsm.cpp b/src/reader2/DExpectTypeSsm.cpp
index 8f848269..5e42f758 100644
--- a/src/reader2/DExpectTypeSsm.cpp
+++ b/src/reader2/DExpectTypeSsm.cpp
@@ -285,6 +285,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DExpectTypeSsm::on_parsed_formal_arglist(DArray * arglist,
+                                                 ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DExpectTypeSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DExpectTypeSsm::on_parsed_expression(obj<AExpression> expr,
                                              ParserStateMachine * p_psm)
diff --git a/src/reader2/DExprSeqState.cpp b/src/reader2/DExprSeqState.cpp
index 5d9fe9b1..12847350 100644
--- a/src/reader2/DExprSeqState.cpp
+++ b/src/reader2/DExprSeqState.cpp
@@ -460,6 +460,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DExprSeqState::on_parsed_formal_arglist(DArray * arglist,
+                                                ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DExprSeqState::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DExprSeqState::on_parsed_expression(obj<AExpression> expr,
                                             ParserStateMachine * p_psm)
diff --git a/src/reader2/DIfElseSsm.cpp b/src/reader2/DIfElseSsm.cpp
index 9f7d7167..f0bf9556 100644
--- a/src/reader2/DIfElseSsm.cpp
+++ b/src/reader2/DIfElseSsm.cpp
@@ -391,6 +391,15 @@ namespace xo {
 
         }
 
+        void
+        DIfElseSsm::on_parsed_formal_arglist(DArray * arglist,
+                                             ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DIfElseSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
 #ifdef NOT_YET
         void
         if_else_xs::on_expr(bp<Expression> expr,
diff --git a/src/reader2/DLambdaSsm.cpp b/src/reader2/DLambdaSsm.cpp
index f9fcd6ae..99e01ffd 100644
--- a/src/reader2/DLambdaSsm.cpp
+++ b/src/reader2/DLambdaSsm.cpp
@@ -349,6 +349,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DLambdaSsm::on_parsed_formal_arglist(DArray * arglist,
+                                             ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DLambdaSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DLambdaSsm::on_parsed_expression(obj<AExpression> expr,
                                          ParserStateMachine * p_psm)
diff --git a/src/reader2/DProgressSsm.cpp b/src/reader2/DProgressSsm.cpp
index 1233c198..57e21ec8 100644
--- a/src/reader2/DProgressSsm.cpp
+++ b/src/reader2/DProgressSsm.cpp
@@ -566,6 +566,15 @@ namespace xo {
                                          this->get_expect_str());
         }
 
+        void
+        DProgressSsm::on_parsed_formal_arglist(DArray * arglist,
+                                               ParserStateMachine * p_psm)
+        {
+            p_psm->illegal_parsed_formal_arglist("DProgressSsm::on_parsed_formal_arglist",
+                                                 arglist,
+                                                 this->get_expect_str());
+        }
+
         void
         DProgressSsm::on_parsed_expression(obj<AExpression> expr,
                                            ParserStateMachine * p_psm)
diff --git a/src/reader2/ISyntaxStateMachine_Any.cpp b/src/reader2/ISyntaxStateMachine_Any.cpp
index 2a16a292..18510abb 100644
--- a/src/reader2/ISyntaxStateMachine_Any.cpp
+++ b/src/reader2/ISyntaxStateMachine_Any.cpp
@@ -58,6 +58,12 @@ ISyntaxStateMachine_Any::on_parsed_formal(Opaque, const DUniqueString *, TypeDes
     _fatal();
 }
 
+auto
+ISyntaxStateMachine_Any::on_parsed_formal_arglist(Opaque, DArray *, ParserStateMachine *)  -> void
+{
+    _fatal();
+}
+
 auto
 ISyntaxStateMachine_Any::on_parsed_expression(Opaque, obj<AExpression>, ParserStateMachine *)  -> void
 {
diff --git a/src/reader2/ISyntaxStateMachine_DDefineSsm.cpp b/src/reader2/ISyntaxStateMachine_DDefineSsm.cpp
index 7117484b..80dc0c81 100644
--- a/src/reader2/ISyntaxStateMachine_DDefineSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DDefineSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DDefineSsm::on_parsed_formal_arglist(DDefineSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DDefineSsm::on_parsed_expression(DDefineSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExpectExprSsm.cpp b/src/reader2/ISyntaxStateMachine_DExpectExprSsm.cpp
index b0f5861d..d6b44995 100644
--- a/src/reader2/ISyntaxStateMachine_DExpectExprSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExpectExprSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExpectExprSsm::on_parsed_formal_arglist(DExpectExprSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExpectExprSsm::on_parsed_expression(DExpectExprSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExpectFormalArgSsm.cpp b/src/reader2/ISyntaxStateMachine_DExpectFormalArgSsm.cpp
index a242df29..b3337d4e 100644
--- a/src/reader2/ISyntaxStateMachine_DExpectFormalArgSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExpectFormalArgSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExpectFormalArgSsm::on_parsed_formal_arglist(DExpectFormalArgSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExpectFormalArgSsm::on_parsed_expression(DExpectFormalArgSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExpectFormalArglistSsm.cpp b/src/reader2/ISyntaxStateMachine_DExpectFormalArglistSsm.cpp
index 006d122b..318283a3 100644
--- a/src/reader2/ISyntaxStateMachine_DExpectFormalArglistSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExpectFormalArglistSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExpectFormalArglistSsm::on_parsed_formal_arglist(DExpectFormalArglistSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExpectFormalArglistSsm::on_parsed_expression(DExpectFormalArglistSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExpectSymbolSsm.cpp b/src/reader2/ISyntaxStateMachine_DExpectSymbolSsm.cpp
index b7f208e8..77b083d6 100644
--- a/src/reader2/ISyntaxStateMachine_DExpectSymbolSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExpectSymbolSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExpectSymbolSsm::on_parsed_formal_arglist(DExpectSymbolSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExpectSymbolSsm::on_parsed_expression(DExpectSymbolSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExpectTypeSsm.cpp b/src/reader2/ISyntaxStateMachine_DExpectTypeSsm.cpp
index 473bd4b7..ffd0b209 100644
--- a/src/reader2/ISyntaxStateMachine_DExpectTypeSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExpectTypeSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExpectTypeSsm::on_parsed_formal_arglist(DExpectTypeSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExpectTypeSsm::on_parsed_expression(DExpectTypeSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DExprSeqState.cpp b/src/reader2/ISyntaxStateMachine_DExprSeqState.cpp
index d11ab3b7..5a9c2e3a 100644
--- a/src/reader2/ISyntaxStateMachine_DExprSeqState.cpp
+++ b/src/reader2/ISyntaxStateMachine_DExprSeqState.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DExprSeqState::on_parsed_formal_arglist(DExprSeqState & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DExprSeqState::on_parsed_expression(DExprSeqState & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DIfElseSsm.cpp b/src/reader2/ISyntaxStateMachine_DIfElseSsm.cpp
index 39a3abb2..94aa8be5 100644
--- a/src/reader2/ISyntaxStateMachine_DIfElseSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DIfElseSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DIfElseSsm::on_parsed_formal_arglist(DIfElseSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DIfElseSsm::on_parsed_expression(DIfElseSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DLambdaSsm.cpp b/src/reader2/ISyntaxStateMachine_DLambdaSsm.cpp
index e59546c8..2a03a774 100644
--- a/src/reader2/ISyntaxStateMachine_DLambdaSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DLambdaSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DLambdaSsm::on_parsed_formal_arglist(DLambdaSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DLambdaSsm::on_parsed_expression(DLambdaSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ISyntaxStateMachine_DProgressSsm.cpp b/src/reader2/ISyntaxStateMachine_DProgressSsm.cpp
index 6fe3f822..1f161ffc 100644
--- a/src/reader2/ISyntaxStateMachine_DProgressSsm.cpp
+++ b/src/reader2/ISyntaxStateMachine_DProgressSsm.cpp
@@ -48,6 +48,11 @@ namespace xo {
             self.on_parsed_formal(param_name, param_type, p_psm);
         }
         auto
+        ISyntaxStateMachine_DProgressSsm::on_parsed_formal_arglist(DProgressSsm & self, DArray * arglist, ParserStateMachine * p_psm) -> void
+        {
+            self.on_parsed_formal_arglist(arglist, p_psm);
+        }
+        auto
         ISyntaxStateMachine_DProgressSsm::on_parsed_expression(DProgressSsm & self, obj<AExpression> expr, ParserStateMachine * p_psm) -> void
         {
             self.on_parsed_expression(expr, p_psm);
diff --git a/src/reader2/ParserStateMachine.cpp b/src/reader2/ParserStateMachine.cpp
index 911b594a..0316515e 100644
--- a/src/reader2/ParserStateMachine.cpp
+++ b/src/reader2/ParserStateMachine.cpp
@@ -6,6 +6,8 @@
 #include "ParserStateMachine.hpp"
 #include "ParserStack.hpp"
 #include "SyntaxStateMachine.hpp"
+#include <xo/object2/array/IPrintable_DArray.hpp>
+#include <xo/printable2/Printable.hpp>
 #include <xo/alloc2/arena/IAllocator_DArena.hpp>
 #include <xo/indentlog/scope.hpp>
 #include <xo/indentlog/print/tostr.hpp>
@@ -13,6 +15,7 @@
 #include <stdexcept>
 
 namespace xo {
+    using xo::print::APrintable;
     using xo::facet::with_facet;
 
     namespace scm {
@@ -140,6 +143,17 @@ namespace xo {
             this->stack_->top().on_parsed_formal(sym, td, this);
         }
 
+        void
+        ParserStateMachine::on_parsed_formal_arglist(DArray * arglist)
+        {
+            scope log(XO_DEBUG(debug_flag_),
+                      xtag("arglist", obj<APrintable,DArray>(arglist)));
+
+            assert(stack_);
+
+            this->stack_->top().on_parsed_formal_arglist(arglist, this);
+        }
+
         void
         ParserStateMachine::on_parsed_expression(obj<AExpression> expr)
         {
@@ -269,7 +283,7 @@ namespace xo {
             // - want to write error message using DArena
             // - need something like log_streambuf and/or tostr() that's arena-aware
 
-            auto errmsg_string = tostr("Unexpected expression",
+            auto errmsg_string = tostr("Unexpected formal",
                                        xtag("param_name", std::string_view(*param_name)),
                                        xtag("param_type", param_type),
                                        xtag("expecting", expect_str),
@@ -284,6 +298,20 @@ namespace xo {
             this->capture_error(ssm_name, errmsg);
         }
 
+        void
+        ParserStateMachine::illegal_parsed_formal_arglist(std::string_view ssm_name,
+                                                          DArray * arglist,
+                                                          std::string_view expect_str)
+        {
+            obj<APrintable,DArray> arglist_pr(arglist);
+
+            auto errmsg_string = tostr("Unexpected formal arglist",
+                                       xtag("arglist", arglist_pr),
+                                       xtag("expecting", expect_str),
+                                       xtag("ssm", ssm_name),
+                                       xtag("via", "ParserStateMachine::illegal_parsed_formal_arglist"));
+        }
+
         void
         ParserStateMachine::illegal_parsed_expression(std::string_view ssm_name,
                                                       obj<AExpression> expr,