Keeping previous type in @psalm-this-out

[olleharstedt]

Consider the following attempt to a type-safe query builder class:

<?php

class Nil {}

/**
 * @template S
 * @template T
 */
class QueryBuilder
{
    /**
     * @psalm-this-out QueryBuilder<Nil, Nil>
     */
    public function __construct()
    {
    }

    /**
     * @psalm-this-out QueryBuilder<HasSelect, null>
     */
    public function select(): void
    {
    }

    /**
     * @psalm-this-out QueryBuilder<null, HasFrom>
     */
    public function from(): void
    {
    }

    public function where(): void
    {
    }

    /**
     * @psalm-if-this-is QueryBuilder<HasSelect, HasFrom>
     */
    public function execute(): void
    {
    }
}

$qb = new QueryBuilder();
$qb->select();
$qb->from();
$qb->execute();

Now, the problem is, to properly code this, I need both functions select() and from() to know and use the incoming type, that is, what $this is. Any way to do that...?

Instead of

 * @psalm-this-out QueryBuilder<HasSelect, null>

it needs to be

* @psalm-this-out QueryBuilder<HasSelect, keep-the-previous-template-type here>

[olleharstedt]

OK, delete this, the solution is simply

* @psalm-this-out QueryBuilder<HasSelect, T>