208         // INVARIANT: The refcount is initialised to a non-zero value.  in new()
232         // INVARIANT: By the safety requirements, the invariants hold.  in from_inner()
333             // INVARIANT: We own the only refcount to this arc, so we may create a `UniqueArc`. We  in into_unique_or_drop()
385         // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is  in deref()
399         // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is  in clone()
403         // INVARIANT: C `refcount_inc` saturates the refcount, so it cannot overflow to zero.  in clone()
404         // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is  in clone()
415         // SAFETY: By the type invariant, there is necessarily a reference to the object. We cannot  in drop()
421         // INVARIANT: If the refcount reaches zero, there are no other instances of `Arc`, and  in drop()
422         // this instance is being dropped, so the broken invariant is not observable.  in drop()
423         // SAFETY: Also by the type invariant, we are allowed to decrement the refcount.  in drop()
534         // INVARIANT: The safety requirements guarantee the invariants.  in new()
578         // SAFETY: By the type invariant, the underlying object is still alive with no mutable  in deref()
666             // INVARIANT: The newly-created object has a refcount of 1.  in new()
673         // INVARIANT: The refcount is initialised to a non-zero value.  in new_uninit()
683             // INVARIANT: The newly-created object has a refcount of 1.  in new_uninit()
756         // SAFETY: By the `Arc` type invariant, there is necessarily a reference to the object, so  in deref_mut()