1: <?php
 2: 
 3: namespace Alchemy\util\promise;
 4: 
 5: 
 6: /**
 7:  * An interface for objects that are functionally identical when composed
 8:  * with Promises; in other words, they must be immutable and time-independent.
 9:  */
10: interface IPromisable {
11: 
12:     /**
13:      * Returns an array mapping promisable methods to return types.
14:      * A promisable method is one that is dependent only on immutable inputs
15:      * and is guaranteed to return an instance of a certain type.
16:      *
17:      * @return array(method_name => class_name, ...)
18:      */
19:     public static function list_promisable_methods();
20: }