diff --git a/lang/interfaces/ast.go b/lang/interfaces/ast.go
index c7b6605e..6f2aebc1 100644
--- a/lang/interfaces/ast.go
+++ b/lang/interfaces/ast.go
@@ -438,6 +438,22 @@ func (obj *Scope) PullIndexes() ([]Expr, bool) {
 	return indexes, exists
 }
 
+// Arg represents a name identifier for a func or class argument declaration and
+// is sometimes accompanied by a type. This does not satisfy the Expr interface.
+type Arg struct {
+	Name string
+	Type *types.Type // nil if unspecified (needs to be solved for)
+}
+
+// String returns a short representation of this arg.
+func (obj *Arg) String() string {
+	s := obj.Name
+	if obj.Type != nil {
+		s += fmt.Sprintf(" %s", obj.Type.String())
+	}
+	return s
+}
+
 // Edge is the data structure representing a compiled edge that is used in the
 // lang to express a dependency between two resources and optionally send/recv.
 type Edge struct {
diff --git a/lang/lexparse_test.go b/lang/lexparse_test.go
index 14ff238d..87fb3e39 100644
--- a/lang/lexparse_test.go
+++ b/lang/lexparse_test.go
@@ -1416,14 +1416,14 @@ func TestLexParse0(t *testing.T) {
 			Prog: []interfaces.Stmt{
 				&StmtClass{
 					Name: "x",
-					Args: []*Arg{},
+					Args: []*interfaces.Arg{},
 					Body: &StmtProg{
 						Prog: []interfaces.Stmt{},
 					},
 				},
 				&StmtClass{
 					Name: "y1",
-					Args: []*Arg{},
+					Args: []*interfaces.Arg{},
 					Body: &StmtProg{
 						Prog: []interfaces.Stmt{},
 					},
@@ -1462,7 +1462,7 @@ func TestLexParse0(t *testing.T) {
 			Prog: []interfaces.Stmt{
 				&StmtClass{
 					Name: "c1",
-					Args: []*Arg{
+					Args: []*interfaces.Arg{
 						{
 							Name: "a",
 							//Type: &types.Type{},
@@ -1535,7 +1535,7 @@ func TestLexParse0(t *testing.T) {
 			Prog: []interfaces.Stmt{
 				&StmtClass{
 					Name: "c1",
-					Args: []*Arg{
+					Args: []*interfaces.Arg{
 						{
 							Name: "a",
 							Type: types.TypeStr,
@@ -1727,7 +1727,7 @@ func TestLexParse0(t *testing.T) {
 				&StmtFunc{
 					Name: "f1",
 					Func: &ExprFunc{
-						Args: []*Arg{},
+						Args: []*interfaces.Arg{},
 						Body: &ExprInt{
 							V: 42,
 						},
@@ -1748,7 +1748,7 @@ func TestLexParse0(t *testing.T) {
 	}
 	{
 		fn := &ExprFunc{
-			Args:   []*Arg{},
+			Args:   []*interfaces.Arg{},
 			Return: types.TypeInt,
 			Body: &ExprCall{
 				Name: operatorFuncName,
@@ -1790,7 +1790,7 @@ func TestLexParse0(t *testing.T) {
 	}
 	{
 		fn := &ExprFunc{
-			Args: []*Arg{
+			Args: []*interfaces.Arg{
 				{
 					Name: "a",
 					Type: types.TypeInt,
@@ -1841,7 +1841,7 @@ func TestLexParse0(t *testing.T) {
 	}
 	{
 		fn := &ExprFunc{
-			Args: []*Arg{
+			Args: []*interfaces.Arg{
 				{
 					Name: "x",
 					Type: types.TypeStr,
@@ -1888,7 +1888,7 @@ func TestLexParse0(t *testing.T) {
 	{
 
 		fn := &ExprFunc{
-			Args: []*Arg{},
+			Args: []*interfaces.Arg{},
 			Body: &ExprInt{
 				V: 42,
 			},
@@ -1915,7 +1915,7 @@ func TestLexParse0(t *testing.T) {
 	}
 	{
 		fn := &ExprFunc{
-			Args: []*Arg{
+			Args: []*interfaces.Arg{
 				{
 					Name: "x",
 					Type: types.TypeStr,
@@ -1962,7 +1962,7 @@ func TestLexParse0(t *testing.T) {
 	}
 	{
 		fn := &ExprFunc{
-			Args: []*Arg{
+			Args: []*interfaces.Arg{
 				{
 					Name: "x",
 					Type: types.TypeStr,
@@ -2027,10 +2027,10 @@ func TestLexParse0(t *testing.T) {
 					Name: "funcgen",
 					// This is the outer function...
 					Func: &ExprFunc{
-						Args: []*Arg{},
+						Args: []*interfaces.Arg{},
 						// This is the inner function...
 						Body: &ExprFunc{
-							Args: []*Arg{},
+							Args: []*interfaces.Arg{},
 							Body: &ExprStr{
 								V: "hello",
 							},
diff --git a/lang/parser.y b/lang/parser.y
index 07b273fd..d4d32e04 100644
--- a/lang/parser.y
+++ b/lang/parser.y
@@ -62,8 +62,8 @@ func init() {
 	structFields []*ExprStructField
 	structField  *ExprStructField
 
-	args []*Arg
-	arg  *Arg
+	args []*interfaces.Arg
+	arg  *interfaces.Arg
 
 	resContents []StmtResContents // interface
 	resField    *StmtResField
@@ -828,7 +828,7 @@ args:
 	/* end of list */
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = []*Arg{}
+		$$.args = []*interfaces.Arg{}
 	}
 |	args COMMA arg
 	{
@@ -838,21 +838,21 @@ args:
 |	arg
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = append([]*Arg{}, $1.arg)
+		$$.args = append([]*interfaces.Arg{}, $1.arg)
 	}
 ;
 arg:
 	// `$x`
 	VAR_IDENTIFIER
 	{
-		$$.arg = &Arg{
+		$$.arg = &interfaces.Arg{
 			Name: $1.str,
 		}
 	}
 	// `$x <type>`
 |	VAR_IDENTIFIER type
 	{
-		$$.arg = &Arg{
+		$$.arg = &interfaces.Arg{
 			Name: $1.str,
 			Type: $2.typ,
 		}
@@ -1242,7 +1242,7 @@ type_struct_fields:
 	/* end of list */
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = []*Arg{}
+		$$.args = []*interfaces.Arg{}
 	}
 |	type_struct_fields SEMICOLON type_struct_field
 	{
@@ -1252,14 +1252,14 @@ type_struct_fields:
 |	type_struct_field
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = append([]*Arg{}, $1.arg)
+		$$.args = append([]*interfaces.Arg{}, $1.arg)
 	}
 ;
 type_struct_field:
 	IDENTIFIER type
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.arg = &Arg{ // re-use the Arg struct
+		$$.arg = &interfaces.Arg{ // re-use the Arg struct
 			Name: $1.str,
 			Type: $2.typ,
 		}
@@ -1269,7 +1269,7 @@ type_func_args:
 	/* end of list */
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = []*Arg{}
+		$$.args = []*interfaces.Arg{}
 	}
 |	type_func_args COMMA type_func_arg
 	{
@@ -1279,15 +1279,15 @@ type_func_args:
 |	type_func_arg
 	{
 		posLast(yylex, yyDollar) // our pos
-		$$.args = append([]*Arg{}, $1.arg)
-		//$$.args = []*Arg{$1.arg} // TODO: is this equivalent?
+		$$.args = append([]*interfaces.Arg{}, $1.arg)
+		//$$.args = []*interfaces.Arg{$1.arg} // TODO: is this equivalent?
 	}
 ;
 type_func_arg:
 	// `<type>`
 	type
 	{
-		$$.arg = &Arg{
+		$$.arg = &interfaces.Arg{
 			Type: $1.typ,
 		}
 	}
@@ -1295,7 +1295,7 @@ type_func_arg:
 	// XXX: should we allow specifying the arg name here?
 |	VAR_IDENTIFIER type
 	{
-		$$.arg = &Arg{
+		$$.arg = &interfaces.Arg{
 			Name: $1.str,
 			Type: $2.typ,
 		}
diff --git a/lang/structs.go b/lang/structs.go
index 0a95b0af..41210e05 100644
--- a/lang/structs.go
+++ b/lang/structs.go
@@ -3970,7 +3970,7 @@ type StmtClass struct {
 	scope *interfaces.Scope // store for referencing this later
 
 	Name string
-	Args []*Arg
+	Args []*interfaces.Arg
 	Body interfaces.Stmt // probably a *StmtProg
 }
 
@@ -4008,7 +4008,7 @@ func (obj *StmtClass) Interpolate() (interfaces.Stmt, error) {
 
 	args := obj.Args
 	if obj.Args == nil {
-		args = []*Arg{}
+		args = []*interfaces.Arg{}
 	}
 
 	return &StmtClass{
@@ -4032,7 +4032,7 @@ func (obj *StmtClass) Copy() (interfaces.Stmt, error) {
 
 	args := obj.Args
 	if obj.Args == nil {
-		args = []*Arg{}
+		args = []*interfaces.Arg{}
 	}
 
 	if !copied { // it's static
@@ -6507,7 +6507,7 @@ type ExprFunc struct {
 	// Args are the list of args that were used when defining the function.
 	// This can include a string name and a type, however the type might be
 	// absent here.
-	Args []*Arg
+	Args []*interfaces.Arg
 	// Return is the return type of the function if it was defined.
 	Return *types.Type // return type if specified
 	// Body is the contents of the function. It can be any expression.
@@ -6647,7 +6647,7 @@ func (obj *ExprFunc) Interpolate() (interfaces.Expr, error) {
 
 	args := obj.Args
 	if obj.Args == nil {
-		args = []*Arg{}
+		args = []*interfaces.Arg{}
 	}
 
 	return &ExprFunc{
@@ -8600,22 +8600,6 @@ func (obj *ExprVar) Value() (types.Value, error) {
 	return expr.Value() // recurse
 }
 
-// Arg represents a name identifier for a func or class argument declaration and
-// is sometimes accompanied by a type. This does not satisfy the Expr interface.
-type Arg struct {
-	Name string
-	Type *types.Type // nil if unspecified (needs to be solved for)
-}
-
-// String returns a short representation of this arg.
-func (obj *Arg) String() string {
-	s := obj.Name
-	if obj.Type != nil {
-		s += fmt.Sprintf(" %s", obj.Type.String())
-	}
-	return s
-}
-
 // ExprIf represents an if expression which *must* have both branches, and which
 // returns a value. As a result, it has a type. This is different from a StmtIf,
 // which does not need to have both branches, and which does not return a value.