let mut variable: Type;
loop {
    variable = value;
}

or

loop {
    let variable: Type = value;
}
  • 1rre
    11·
    2 days ago

    This is Rust not Python

    They’re both optimised out by the compiler. If you disable compiler optimisations, they’re identical in machine code anyway, unless you introduce a second loop, in which case the first will be more memory efficient as the memory used in the first loop can be reused in the second loop, whereas if you declare the variable outside the loop it can’t (again, without compiler optimisations, which make the whole comparison pointless).