array_splice with two lists should produce a list

[dbrekelmans]

I would not expect to see this error since list<E> and array<int, E> are practically the same.

https://psalm.dev/r/25b06d9cfd

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/25b06d9cfd

<?php

/**
 * @template E as object
 */
final class Foo {
    /** 
     * @psalm-var list<E>
     * @var array<int, object>
     **/
    private $elements;
    
    /**
     * @psalm-param array<array-key, E> $elements
     * @param array<int|string, object> $elements
     */
    public function __construct(array $elements = [])
    {
        $this->elements = array_values($elements);
    }
    
    /**
     * @psalm-param E $element
     */
    public function bar(int $index, object $element) : void
    {
        array_splice($this->elements, $index, 0, [$element]);
    }
}

Psalm output (using commit 8926f1d):

ERROR: PropertyTypeCoercion - 27:22 - $this->elements expects 'list<E:Foo as object>',  parent type 'array<int, E:Foo as object>' provided

[weirdan]

It shouldn't complain here, not for the reason you state (list and array<int,_> are different), but because array_splice on lists outputs lists.