src/test/compile-fail/loop-proper-liveness.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 fn test1() {
  12     // In this test the outer 'a loop may terminate without `x` getting initialised. Although the
  13     // `x = loop { ... }` statement is reached, the value itself ends up never being computed and
  14     // thus leaving `x` uninit.
  15     let x: i32;
  16     'a: loop {
  17         x = loop { break 'a };
  18     }
  19     println!("{:?}", x); //~ ERROR use of possibly uninitialized variable
  20 }
  21
  22 // test2 and test3 should not fail.
  23 fn test2() {
  24     // In this test the `'a` loop will never terminate thus making the use of `x` unreachable.
  25     let x: i32;
  26     'a: loop {
  27         x = loop { continue 'a };
  28     }
  29     println!("{:?}", x);
  30 }
  31
  32 fn test3() {
  33     let x: i32;
  34     // Similarly, the use of variable `x` is unreachable.
  35     'a: loop {
  36         x = loop { return };
  37     }
  38     println!("{:?}", x);
  39 }
  40
  41 fn main() {
  42 }