larastan: Literal string is not a `non-empty-string`

• Larastan Version: 1.0.0
• --level used: 7
• Pull request with failing test:

Description

non-empty-string appeared as errors even no actually bugs happen

Laravel code where the issue was found

#  381
        $products = Product::whereIn((new Product())->getRouteKeyName(), $values)
            ->pluck('title', (new Product())->getRouteKeyName())
            ->toArray();

# 417
        $users = User::whereIn((new User())->getRouteKeyName(), $values)
            ->get()
            ->pluck('full_name', (new User())->getRouteKeyName())
            ->toArray();

# 610
       $products = Product::whereIn((new Product())->getRouteKeyName(), $this->freeProducts)->get();

# 627
       ? User::whereIn(
                (new User())->getRouteKeyName(),
                $this->specificCustomers
            )->get()->all()
            : [];

# models
    public function getRouteKeyName(): string
    {
        return 'slug';
    }

I try to search the solution but it was not found any

thank you