At compile time, Rust guaranteed memory safety here by ensuring a runtime check was present, which your code triggered, resulting in a panic. A panic is not a

At compile time, Rust guaranteed memory safety here by ensuring a runtime check was present, which your code triggered, resulting in a panic. A panic is not a violation of memory safety; if you wanted to violate memory safety you'd need to have caused that deref to succeed, and println to spit out the result. EDIT: let me guess, did the panic message include "index out of bounds: the len is 5 but the index is 10"?