diff --git a/bind-expr-functions.go b/bind-expr-functions.go
index f39d5fc..02427d3 100644
--- a/bind-expr-functions.go
+++ b/bind-expr-functions.go
@@ -29,6 +29,10 @@ func newExprFunctor(e Expr, params []ExprFuncParam, ctx ExprContext) *exprFuncto
 	return &exprFunctor{expr: e, params: params, defCtx: defCtx}
 }
 
+func (functor *exprFunctor) TypeName() string {
+	return "ExprFunctor"
+}
+
 func (functor *exprFunctor) GetDefinitionContext() ExprContext {
 	return functor.defCtx
 }
diff --git a/bind-go-functions.go b/bind-go-functions.go
index d525ef6..c120f5f 100644
--- a/bind-go-functions.go
+++ b/bind-go-functions.go
@@ -14,6 +14,10 @@ func NewGolangFunctor(f FuncTemplate) *golangFunctor {
 	return &golangFunctor{f: f}
 }
 
+func (functor *golangFunctor) TypeName() string {
+	return "GoFunctor"
+}
+
 func (functor *golangFunctor) Invoke(ctx ExprContext, name string, args []any) (result any, err error) {
 	return functor.f(ctx, name, args)
 }
diff --git a/expr-function.go b/expr-function.go
index 9e33051..d8520ae 100644
--- a/expr-function.go
+++ b/expr-function.go
@@ -6,6 +6,7 @@ package expr
 
 // ---- Functor interface
 type Functor interface {
+	Typer
 	Invoke(ctx ExprContext, name string, args []any) (result any, err error)
 	SetFunc(info ExprFunc)
 	GetFunc() ExprFunc