Currently, Vec has a resize method which takes a new parameter so that if the resize involves growing the vector, the new parameter is cloned into each newly-created cell in the vector. T must implement Clone in order for this method to be available.

It would be useful to add a resize_default method that instead requires that T: Default, and calls T::default() to fill the newly-created cells. Not only would this be ergonomic, but for certain implementations of T::default, it might allow the compiler to make better optimizations.