`pluck($value, $key)->all()` returns `array<array-key, mixed>` instead of `array<KeyType, ValueType>` from @property annotations

[alies-dev]

Summary

When Collection::pluck($valueColumn, $keyColumn) is called on an Eloquent collection with both arguments, and both columns have known types via @property annotations on the model, the resulting ->all() is still inferred as array<array-key, mixed> instead of array<KeyType, ValueType>. This forces a LessSpecificReturnStatement on any method that declares the narrowed shape as its return type.

This is the two-argument sibling of #486 (which covered single-argument pluck('column') and is closed completed). Two-argument pluck is not narrowed today.

Repro

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Relations\HasMany;

/**
 * @property string $title
 * @property string $slug
 */
class Article extends Model {}

/**
 * @property string $name
 *
 * @method HasMany<Article, $this> articles()
 */
class Author extends Model
{
    public function articles(): HasMany
    {
        return $this->hasMany(Article::class);
    }
}

class Presenter
{
    /**
     * @return array<string, string>
     */
    public function titlesBySlug(Author $author): array
    {
        return $author->articles()->pluck('title', 'slug')->all();
    }
}

Psalm reports:

ERROR: LessSpecificReturnStatement
The type 'array<array-key, mixed>' is more general than the declared return type
'array<string, string>' for Presenter::titlesBySlug (see https://psalm.dev/129)
    return $author->articles()->pluck('title', 'slug')->all();

Same shape applies when the collection comes from Model::query()->get()->pluck('value_col', 'key_col'), or from any Eloquent\Collection whose model declares both columns via @property.

Expected

For Collection<TKey, TModel of Model>::pluck(string \$value, string \$key):

• if TModel has @property V \$value and @property K \$key (where K resolves to an array-key type), the return should be Support\Collection<K, V>;
• consequently ->all() should resolve to array<K, V>.

Today the plugin appears to leave both TKey and TValue unresolved, so the call chain collapses to array<array-key, mixed>.

Environment

• psalm/plugin-laravel: dev-master
• vimeo/psalm: 7.0.0-beta19
• PHP: 8.4

Workaround

/** @var array<string, string> $titlesBySlug */
$titlesBySlug = $author->articles()->pluck('title', 'slug')->all();
return $titlesBySlug;

…or splitting into two pluck calls and recombining, which is strictly worse.

Related

• pluck() should infer value type from @property annotations #486 — closed; covered single-argument pluck('column') value inference. The fix there did not extend to the two-argument form, so the key side is still array-key and the value side falls back to mixed.