psalm/src/Psalm/Internal/Stubs/Amp.php

<?php

namespace Amp;

/**
 * @template TReturn
 * @param callable():\Generator<mixed, mixed, mixed, TReturn> $gen
 * @return Promise<TReturn>
 */
function coroutine(callable $gen) : Promise {}

/**
 * @template TReturn
 * @param callable():(\Generator<mixed, mixed, mixed, TReturn>|null) $gen
 * @return Promise<TReturn>
 */
function call(callable $gen) : Promise {}

/**
 * @template TReturn
 */
interface Promise {
    /**
     * @param callable(\Throwable|null $exception, TReturn|null $result):void
     * @return void
     */
    function onResolve(callable $onResolved);
}

/**
 * @template TReturn
 *
 * @template-implements Promise<TReturn>
 */
class Success implements Promise {
    /**
     * @param callable(\Throwable|null $exception, TReturn|null $result):void
     * @return void
     */
    function onResolve(callable $onResolved) {}
}