IsOptional() function of ExprFuncParam renamed as IdDefault(). A new IsOptional() function created to check if a param is optional without requiring a default value

function.go

@@ -91,7 +91,7 @@ func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (re
 			ctx.UnsafeSetVar(p.Name(), nil)
 		}
 	}
-	result, err = functor.expr.eval(ctx, false)
+	result, err = functor.expr.Eval(ctx)
 	return
 }
 
@@ -99,7 +99,8 @@ func (functor *exprFunctor) Invoke(ctx ExprContext, name string, args []any) (re
 type paramFlags uint16
 
 const (
-	PfOptional paramFlags = 1 << iota
+	PfDefault paramFlags = 1 << iota
+	PfOptional
 	PfRepeat
 )
 
@@ -126,7 +127,11 @@ func (param *funcParamInfo) Name() string {
 }
 
 func (param *funcParamInfo) Type() string {
-	return "any"
+	return TypeAny
+}
+
+func (param *funcParamInfo) IsDefault() bool {
+	return (param.flags & PfDefault) != 0
 }
 
 func (param *funcParamInfo) IsOptional() bool {
@@ -159,7 +164,7 @@ func newFuncInfo(name string, functor Functor, returnType string, params []ExprF
 			if maxArgs == -1 {
 				return nil, fmt.Errorf("no more params can be specified after the ellipsis symbol: %q", p.Name())
 			}
-			if p.IsOptional() {
+			if p.IsDefault() || p.IsOptional() {
 				maxArgs++
 			} else if maxArgs == minArgs {
 				minArgs++
@@ -207,7 +212,7 @@ func (info *funcInfo) ToString(opt FmtOpt) string {
 			}
 			sb.WriteString(p.Name())
 
-			if p.IsOptional() {
+			if p.IsDefault() {
 				sb.WriteByte('=')
 				if s, ok := p.DefaultValue().(string); ok {
 					sb.WriteByte('"')