What are some common pitfalls or downsides of overusing traits extensively throughout a large codebase, particularly regarding code readability and maintainability?

While traits are a genuinely useful tool for legitimate code reuse, overusing them extensively throughout a large codebase can make it significantly harder to understand a class's full actual behavior at a glance, since a developer reading a class definition may need to separately look up several different trait files to understand where each of that class's various methods actually come from, and traits can also make certain kinds of state management surprising if a developer does not carefully consider how instance properties defined within a trait interact with a specific using class, so many experienced teams recommend using traits sparingly and deliberately, favoring composition for cases involving anything beyond genuinely simple, self contained, cross cutting behavior.

// A class using five different traits can become hard to fully understand
class Order {
    use Loggable, Cacheable, Searchable, Sortable, Validatable;
}