Method coroutine

examples/demo.php:1757–1764

@return \Generator */

()

    /** @return \Generator<int, string, Pencil, void> */
    public function coroutine(): \Generator
    {
        // TSend inference: $var = yield gets the 3rd Generator type param.
        // yield produces 'ready' (TValue = string) to the consumer;
        // the yield expression evaluates to whatever was ->send()'d (TSend = Pencil).
        $pencil = yield 'ready';
        $pencil->sketch();                // resolves to Pencil (TSend)
    }

    /** @return \Generator<int, string, Pencil, void> */
    public function tsendInsideNestedBlocks(): \Generator