src/test/ui/span/issue28498-reject-lifetime-param.rs

   1 // Demonstrate that having a lifetime param causes dropck to reject code
   2 // that might indirectly access previously dropped value.
   3 //
   4 // Compare with run-pass/issue28498-ugeh-with-lifetime-param.rs
   5
   6 #[derive(Debug)]
   7 struct ScribbleOnDrop(String);
   8
   9 impl Drop for ScribbleOnDrop {
  10     fn drop(&mut self) {
  11         self.0 = format!("DROPPED");
  12     }
  13 }
  14
  15 struct Foo<'a>(u32, &'a ScribbleOnDrop);
  16
  17 impl<'a> Drop for Foo<'a> {
  18     fn drop(&mut self) {
  19         // Use of `may_dangle` is unsound, because destructor accesses borrowed data
  20         // in `self.1` and we must force that to strictly outlive `self`.
  21         println!("Dropping Foo({}, {:?})", self.0, self.1);
  22     }
  23 }
  24
  25 fn main() {
  26     let (last_dropped, foo0);
  27     let (foo1, first_dropped);
  28
  29     last_dropped = ScribbleOnDrop(format!("last"));
  30     first_dropped = ScribbleOnDrop(format!("first"));
  31     foo0 = Foo(0, &last_dropped); // OK
  32     foo1 = Foo(1, &first_dropped);
  33     //~^ ERROR `first_dropped` does not live long enough
  34
  35     println!("foo0.1: {:?} foo1.1: {:?}", foo0.1, foo1.1);
  36 }