Why do you mention lifetimes here? They are exclusively a compile-time pointer annotation, they have no runtime behavior, thus no overhead.
Dynamic dispatch in general is much, much faster than many people’s intuition seems to indicate. Your function doesn’t have to be going much at all for the difference to become irrelevant. Where it matters is for inlining.
Dynamic dispatch in Rust is expected to be very slightly faster than in C++ (due to one fewer indirections, because Rust uses fat pointers instead of an object prefix).
Dynamic dispatch in general is much, much faster than many people’s intuition seems to indicate. Your function doesn’t have to be going much at all for the difference to become irrelevant. Where it matters is for inlining.
Dynamic dispatch in Rust is expected to be very slightly faster than in C++ (due to one fewer indirections, because Rust uses fat pointers instead of an object prefix).