src/test/ui/hygiene/hygienic-labels.rs

   1 // run-pass
   2 #![allow(unreachable_code)]
   3 // Test that labels injected by macros do not break hygiene.
   4
   5 // Issue #24278: The label/lifetime shadowing checker from #24162
   6 // conservatively ignores hygiene, and thus issues warnings that are
   7 // both true- and false-positives for this test.
   8
   9 macro_rules! loop_x {
  10     ($e: expr) => {
  11         // $e shouldn't be able to interact with this 'x
  12         'x: loop { $e }
  13     }
  14 }
  15
  16 macro_rules! run_once {
  17     ($e: expr) => {
  18         // ditto
  19         'x: for _ in 0..1 { $e }
  20     }
  21 }
  22
  23 macro_rules! while_x {
  24     ($e: expr) => {
  25         // ditto
  26         'x: while 1 + 1 == 2 { $e }
  27     }
  28 }
  29
  30 pub fn main() {
  31     'x: for _ in 0..1 {
  32         // this 'x should refer to the outer loop, lexically
  33         loop_x!(break 'x);
  34         panic!("break doesn't act hygienically inside for loop");
  35     }
  36
  37     'x: loop {
  38         // ditto
  39         loop_x!(break 'x);
  40         panic!("break doesn't act hygienically inside infinite loop");
  41     }
  42
  43     'x: while 1 + 1 == 2 {
  44         while_x!(break 'x);
  45         panic!("break doesn't act hygienically inside infinite while loop");
  46     }
  47
  48     'x: for _ in 0..1 {
  49         // ditto
  50         run_once!(continue 'x);
  51         panic!("continue doesn't act hygienically inside for loop");
  52     }
  53 }