message: remove too expensive debug assertion
diff: @@ -346,23 +346,6 @@ impl<'tcx> Stack {
  Ok(())
  }
  - /// `reborrow` helper function: test that the stack invariants are still maintained.
  - fn test_invariants(&self) {
  - let mut saw_shared_read_only = false;
  - for item in self.borrows.iter() {
  - match item.perm {
  - Permission::SharedReadOnly => {
  - saw_shared_read_only = true;
  - }
  - // Otherwise, if we saw one before, that's a bug.
  - perm if saw_shared_read_only => {
  - bug!("Found {:?} on top of a SharedReadOnly!", perm);
  - }
  - _ => {}
  - }
  - }
  - }
  -
  /// Derived a new pointer from one with the given tag.
  /// `weak` controls whether this operation is weak or strong: weak granting does not act as
  /// an access, and they add the new item directly on top of the one it is derived
  @@ -418,11 +401,6 @@ impl<'tcx> Stack {
  self.borrows.insert(new_idx, new);
  }
  - // Make sure that after all this, the stack's invariant is still maintained.
  - if cfg!(debug_assertions) {
  - self.test_invariants();
  - }
  -
  Ok(())
  }
  }
  