[catnaroek]

Default arguments, at least as done in C++, complicate the language's semantics (e.g., template specialization selection) far more than they raise the level abstraction. Definitely not a well-designed feature.

And Rust's traits are a far more principled (and thus better!) approach to overloading than anything C++ has (Boost's concept checks?). Traits turn concepts into language entities that are directly expressible in Rust syntax, rather than in awkward English documentation.