tests/ui-fulldeps/dropck-tarena-unsound-drop.rs

   1 // Check that an arena (TypedArena) cannot carry elements whose drop
   2 // methods might access borrowed data of lifetime that does not
   3 // strictly outlive the arena itself.
   4 //
   5 // Compare against run-pass/dropck_tarena_sound_drop.rs, which shows a
   6 // similar setup, but loosens `f` so that the struct `C<'a>` can be
   7 // fed a lifetime longer than that of the arena.
   8 //
   9 // (Also compare against dropck_tarena_cycle_checked.rs, from which
  10 // this was reduced to better understand its error message.)
  11
  12 #![feature(rustc_private)]
  13
  14 extern crate rustc_arena;
  15
  16 use rustc_arena::TypedArena;
  17
  18 trait HasId { fn count(&self) -> usize; }
  19
  20 struct CheckId<T:HasId> { v: T }
  21
  22 // In the code below, the impl of HasId for `&'a usize` does not
  23 // actually access the borrowed data, but the point is that the
  24 // interface to CheckId does not (and cannot) know that, and therefore
  25 // when encountering a value V of type CheckId<S>, we must
  26 // conservatively force the type S to strictly outlive V.
  27 impl<T:HasId> Drop for CheckId<T> {
  28     fn drop(&mut self) {
  29         assert!(self.v.count() > 0);
  30     }
  31 }
  32
  33 struct C<'a> { v: CheckId<&'a usize>, }
  34
  35 impl<'a> HasId for &'a usize { fn count(&self) -> usize { 1 } }
  36
  37 fn f<'a>(_arena: &'a TypedArena<C<'a>>) {}
  38
  39 fn main() {
  40     let arena: TypedArena<C> = TypedArena::default();
  41     f(&arena);
  42 } //~^ ERROR `arena` does not live long enough