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

   1 // run-pass
   2 #![allow(unreachable_code)]
   3 #![allow(unused_labels)]
   4
   5 // Test that labels injected by macros do not break hygiene.  This
   6 // checks cases where the macros invocations are under the rhs of a
   7 // let statement.
   8
   9 // Issue #24278: The label/lifetime shadowing checker from #24162
  10 // conservatively ignores hygiene, and thus issues warnings that are
  11 // both true- and false-positives for this test.
  12
  13 macro_rules! loop_x {
  14     ($e: expr) => {
  15         // $e shouldn't be able to interact with this 'x
  16         'x: loop {
  17             $e
  18         }
  19     };
  20 }
  21
  22 macro_rules! while_true {
  23     ($e: expr) => {
  24         // $e shouldn't be able to interact with this 'x
  25         'x: while 1 + 1 == 2 {
  26             $e
  27         }
  28     };
  29 }
  30
  31 macro_rules! run_once {
  32     ($e: expr) => {
  33         // ditto
  34         'x: for _ in 0..1 {
  35             $e
  36         }
  37     };
  38 }
  39
  40 pub fn main() {
  41     let mut i = 0;
  42
  43     let j: isize = {
  44         'x: loop {
  45             // this 'x should refer to the outer loop, lexically
  46             loop_x!(break 'x);
  47             i += 1;
  48         }
  49         i + 1
  50     };
  51     assert_eq!(j, 1);
  52
  53     let k: isize = {
  54         'x: for _ in 0..1 {
  55             // ditto
  56             loop_x!(break 'x);
  57             i += 1;
  58         }
  59         i + 1
  60     };
  61     assert_eq!(k, 1);
  62
  63     let l: isize = {
  64         'x: for _ in 0..1 {
  65             // ditto
  66             while_true!(break 'x);
  67             i += 1;
  68         }
  69         i + 1
  70     };
  71     assert_eq!(l, 1);
  72
  73     let n: isize = {
  74         'x: for _ in 0..1 {
  75             // ditto
  76             run_once!(continue 'x);
  77             i += 1;
  78         }
  79         i + 1
  80     };
  81     assert_eq!(n, 1);
  82 }