Stratadox / ImmutableCollection

src/Merging.php

<?php

declare(strict_types=1);

namespace Stratadox\ImmutableCollection;

use function array_merge;
use Stratadox\Collection\Collection;
use Stratadox\Collection\Mergeable;

/**
 * Behaviour to allow "merging" the immutable collection.
 *
 * Provides access to merging behaviour in the form of a method that
 * returns a modified copy of the original (immutable) collection.
 *
 * @package Stratadox\Collection
 * @author  Stratadox
 */
trait Merging
{
    /**
     * @see Mergeable::merge()
     * @param Collection $other
     * @return static
     */
    public function merge(Collection $other)
    {
        return $this->newCopy(array_merge($this->items(), $other->items()));

The expression return $this->newCopy(array_merge($this->items(), $other->items())) returns the type Stratadox\Collection\Collection which is incompatible with the documented return type Stratadox\ImmutableCollection\Merging.

    }

    /** @see Collection::items() */
    abstract public function items(): array;

    /**
     * @see ImmutableCollection::newCopy()
     * @param array $items
     * @return Collection|static
     */
    abstract protected function newCopy(array $items): Collection;
}