tests/ui/closures/2229_closure_analysis/diagnostics/liveness.rs

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