[E037] Error: property `Foo::$s` cannot have type `callable`
   ,-[code.php:4:12]
   |
 3 | class Foo {
   *       ^^^  
   *             
 4 |     public callable $s;
   *            ^^^^|^^^ ^^  
   *                |         
   *                |        
   *                `-------- try using a different type
   * 
   * Note: `void`, `never`, and `callable` types are not allowed in properties
---'