src/test/ui/closures/2229_closure_analysis/diagnostics/liveness.rs

   1 // edition:2021
   2
   3 // check-pass
   4 #![allow(unreachable_code)]
   5 #![warn(unused)]
   6
   7 #[derive(Debug)]
   8 struct Point {
   9     x: i32,
  10     y: i32,
  11 }
  12
  13 pub fn f() {
  14     let mut a = 1;
  15     let mut c = Point{ x:1, y:0 };
  16
  17     // Captured by value, but variable is dead on entry.
  18     (move || {
  19         // This will not trigger a warning for unused variable as
  20         // c.x will be treated as a Non-tracked place
  21         c.x = 1;
  22         println!("{}", c.x);
  23         a = 1; //~ WARN value captured by `a` is never read
  24         println!("{}", a);
  25     })();
  26
  27     // Read and written to, but never actually used.
  28     (move || {
  29         // This will not trigger a warning for unused variable as
  30         // c.x will be treated as a Non-tracked place
  31         c.x += 1;
  32         a += 1; //~ WARN unused variable: `a`
  33     })();
  34
  35     (move || {
  36         println!("{}", c.x);
  37         // Value is read by closure itself on later invocations.
  38         // This will not trigger a warning for unused variable as
  39         // c.x will be treated as a Non-tracked place
  40         c.x += 1;
  41         println!("{}", a);
  42         a += 1;
  43     })();
  44     let b = Box::new(42);
  45     (move || {
  46         println!("{}", c.x);
  47         // Never read because this is FnOnce closure.
  48         // This will not trigger a warning for unused variable as
  49         // c.x will be treated as a Non-tracked place
  50         c.x += 1;
  51         println!("{}", a);
  52         a += 1; //~ WARN value assigned to `a` is never read
  53         drop(b);
  54     })();
  55 }
  56
  57 #[derive(Debug)]
  58 struct MyStruct<'a>  {
  59     x: Option<& 'a str>,
  60     y: i32,
  61 }
  62
  63 pub fn nested() {
  64     let mut a : Option<& str>;
  65     a = None;
  66     let mut b : Option<& str>;
  67     b = None;
  68     let mut d = MyStruct{ x: None, y: 1};
  69     let mut e = MyStruct{ x: None, y: 1};
  70     (|| {
  71         (|| {
  72             // This will not trigger a warning for unused variable as
  73             // d.x will be treated as a Non-tracked place
  74             d.x = Some("d1");
  75             d.x = Some("d2");
  76             a = Some("d1"); //~ WARN value assigned to `a` is never read
  77             a = Some("d2");
  78         })();
  79         (move || {
  80             // This will not trigger a warning for unused variable as
  81             //e.x will be treated as a Non-tracked place
  82             e.x = Some("e1");
  83             e.x = Some("e2");
  84             b = Some("e1"); //~ WARN value assigned to `b` is never read
  85                             //~| WARN unused variable: `b`
  86             b = Some("e2"); //~ WARN value assigned to `b` is never read
  87         })();
  88     })();
  89 }
  90
  91 fn main() {}