fix: unused const, type cast

src/Field/CheckboxField.php

@@ -6,9 +6,6 @@ use WPDesk\Forms\Field;
 
 class CheckboxField extends BasicField {
 
-	const VALUE_TRUE  = 'yes';
-	const VALUE_FALSE = 'no';
-
 	public function get_type(): string {
 		return 'checkbox';
 	}

src/Field/DateField.php

@@ -7,15 +7,14 @@ use WPDesk\Forms\Sanitizer\TextFieldSanitizer;
 class DateField extends BasicField {
 
 	public function __construct() {
-		parent::__construct();
 		$this->set_placeholder('YYYY-MM-DD');
 	}
 
-	public function get_type() {
+	public function get_type(): string {
 		return 'date';
 	}
 
-	public function get_template_name() {
+	public function get_template_name(): string {
 		return 'input-text';
 	}