src/test/ui/lint/unused_labels.rs

   1 // The output should warn when a loop label is not used. However, it
   2 // should also deal with the edge cases where a label is shadowed,
   3 // within nested loops
   4
   5 // build-pass (FIXME(62277): could be check-pass?)
   6
   7 #![feature(label_break_value)]
   8 #![warn(unused_labels)]
   9
  10 fn main() {
  11     'unused_while_label: while 0 == 0 {
  12         //~^ WARN unused label
  13     }
  14
  15     let opt = Some(0);
  16     'unused_while_let_label: while let Some(_) = opt {
  17         //~^ WARN unused label
  18     }
  19
  20     'unused_for_label: for _ in 0..10 {
  21         //~^ WARN unused label
  22     }
  23
  24     'used_loop_label: loop {
  25         break 'used_loop_label;
  26     }
  27
  28     'used_loop_label_outer_1: for _ in 0..10 {
  29         'used_loop_label_inner_1: for _ in 0..10 {
  30             break 'used_loop_label_inner_1;
  31         }
  32         break 'used_loop_label_outer_1;
  33     }
  34
  35     'used_loop_label_outer_2: for _ in 0..10 {
  36         'unused_loop_label_inner_2: for _ in 0..10 {
  37             //~^ WARN unused label
  38             break 'used_loop_label_outer_2;
  39         }
  40     }
  41
  42     'unused_loop_label_outer_3: for _ in 0..10 {
  43         //~^ WARN unused label
  44         'used_loop_label_inner_3: for _ in 0..10 {
  45             break 'used_loop_label_inner_3;
  46         }
  47     }
  48
  49     // You should be able to break the same label many times
  50     'many_used: loop {
  51         if true {
  52             break 'many_used;
  53         } else {
  54             break 'many_used;
  55         }
  56     }
  57
  58     // Test breaking many times with the same inner label doesn't break the
  59     // warning on the outer label
  60     'many_used_shadowed: for _ in 0..10 {
  61         //~^ WARN unused label
  62         'many_used_shadowed: for _ in 0..10 {
  63             //~^ WARN label name `'many_used_shadowed` shadows a label name that is already in scope
  64             if 1 % 2 == 0 {
  65                 break 'many_used_shadowed;
  66             } else {
  67                 break 'many_used_shadowed;
  68             }
  69         }
  70     }
  71
  72     'unused_loop_label: loop {
  73         //~^ WARN unused label
  74         break;
  75     }
  76
  77     // Make sure unused block labels give warnings...
  78     'unused_block_label: {
  79         //~^ WARN unused label
  80     }
  81
  82     // ...and that used ones don't:
  83     'used_block_label: {
  84         break 'used_block_label;
  85     }
  86 }