fn fib(n: i32) -> i32 so unnecesary, just extra writing. We're developers, we understand that function return types are after first () let mut i = 0;

fn fib(n: i32) -> i32 so unnecesary, just extra writing. We're developers, we understand that function return types are after first () let mut i = 0; No, no, copy Go here, i := 0 is just fine