tests/ui/mir/mir_drop_order.rs

   1 // run-pass
   2 // needs-unwind
   3
   4 use std::cell::RefCell;
   5 use std::panic;
   6
   7 pub struct DropLogger<'a> {
   8     id: usize,
   9     log: &'a panic::AssertUnwindSafe<RefCell<Vec<usize>>>
  10 }
  11
  12 impl<'a> Drop for DropLogger<'a> {
  13     fn drop(&mut self) {
  14         self.log.0.borrow_mut().push(self.id);
  15     }
  16 }
  17
  18 struct InjectedFailure;
  19
  20 #[allow(unreachable_code)]
  21 fn main() {
  22     let log = panic::AssertUnwindSafe(RefCell::new(vec![]));
  23     let d = |id| DropLogger { id: id, log: &log };
  24     let get = || -> Vec<_> {
  25         let mut m = log.0.borrow_mut();
  26         let n = m.drain(..);
  27         n.collect()
  28     };
  29
  30     {
  31         let _x = (d(0), &d(1), d(2), &d(3));
  32         // all borrows are extended - nothing has been dropped yet
  33         assert_eq!(get(), vec![]);
  34     }
  35     // in a let-statement, extended places are dropped
  36     // *after* the let result (tho they have the same scope
  37     // as far as scope-based borrowck goes).
  38     assert_eq!(get(), vec![0, 2, 3, 1]);
  39
  40     let _ = std::panic::catch_unwind(|| {
  41         (d(4), &d(5), d(6), &d(7), panic::panic_any(InjectedFailure));
  42     });
  43
  44     // here, the temporaries (5/7) live until the end of the
  45     // containing statement, which is destroyed after the operands
  46     // (4/6) on a panic.
  47     assert_eq!(get(), vec![6, 4, 7, 5]);
  48 }