tests/ui-fulldeps/dropck_tarena_sound_drop.rs

   1 // run-pass
   2
   3 #![allow(unknown_lints)]
   4 // Check that an arena (TypedArena) can carry elements whose drop
   5 // methods might access borrowed data, as long as the borrowed data
   6 // has lifetime that strictly outlives the arena itself.
   7 //
   8 // Compare against ui-fulldeps/dropck-tarena-unsound-drop.rs, which
   9 // shows a similar setup, but restricts `f` so that the struct `C<'a>`
  10 // is force-fed a lifetime equal to that of the borrowed arena.
  11
  12 #![allow(unstable)]
  13 #![feature(rustc_private)]
  14
  15 extern crate rustc_arena;
  16
  17 // Necessary to pull in object code as the rest of the rustc crates are shipped only as rmeta
  18 // files.
  19 #[allow(unused_extern_crates)]
  20 extern crate rustc_driver;
  21
  22 use rustc_arena::TypedArena;
  23
  24 trait HasId { fn count(&self) -> usize; }
  25
  26 struct CheckId<T:HasId> { v: T }
  27
  28 // In the code below, the impl of HasId for `&'a usize` does not
  29 // actually access the borrowed data, but the point is that the
  30 // interface to CheckId does not (and cannot) know that, and therefore
  31 // when encountering a value V of type CheckId<S>, we must
  32 // conservatively force the type S to strictly outlive V.
  33 impl<T:HasId> Drop for CheckId<T> {
  34     fn drop(&mut self) {
  35         assert!(self.v.count() > 0);
  36     }
  37 }
  38
  39 struct C<'a> { _v: CheckId<&'a usize>, }
  40
  41 impl<'a> HasId for &'a usize { fn count(&self) -> usize { 1 } }
  42
  43 fn f<'a, 'b>(_arena: &'a TypedArena<C<'b>>) {}
  44
  45 fn main() {
  46     let arena: TypedArena<C> = TypedArena::default();
  47     f(&arena);
  48 }