src/test/ui/loops/loop-proper-liveness.rs

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

fn test1() {
    // In this test the outer 'a loop may terminate without `x` getting initialised. Although the
    // `x = loop { ... }` statement is reached, the value itself ends up never being computed and
    // thus leaving `x` uninit.
    let x: i32;
    'a: loop {
        x = loop { break 'a };
    }
    println!("{:?}", x); //~ ERROR use of possibly uninitialized variable
}

// test2 and test3 should not fail.
fn test2() {
    // In this test the `'a` loop will never terminate thus making the use of `x` unreachable.
    let x: i32;
    'a: loop {
        x = loop { continue 'a };
    }
    println!("{:?}", x);
}

fn test3() {
    let x: i32;
    // Similarly, the use of variable `x` is unreachable.
    'a: loop {
        x = loop { return };
    }
    println!("{:?}", x);
}

fn main() {
}