> Only in debug builds does it raise a panic.

Correctness in debug builds is important, isn't it?

That said, panic on integer overflow in debug builds is unfortunate behavior. Overflow should cause an abort, not a panic.

> make the performance tradeoff that C++ does and defines signed integer math to wrap 2’s complement

In C++, signed overflow is undefined behavior, not wraparound. This property is useful to the optimizer for things like inferring loop bounds. The optimizer has less flexibility in equivalent Rust code.

You can enable overflow panics in release build, so if you're a library, you have to play it safe because you don't know how people will build your library.