diff options
| -rw-r--r-- | library/core/src/cell/lazy.rs | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/library/core/src/cell/lazy.rs b/library/core/src/cell/lazy.rs index 4039cc26812..aff3388529a 100644 --- a/library/core/src/cell/lazy.rs +++ b/library/core/src/cell/lazy.rs @@ -115,16 +115,15 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> { // SAFETY: // If the closure accessed the cell through something like a reentrant // mutex, but caught the panic resulting from the state being poisoned, - // the mutable borrow for `state` will be invalidated, so create a new - // one here. - let state = unsafe { &mut *this.state.get() }; - *state = State::Init(data); + // the mutable borrow for `state` will be invalidated, so we need to + // go through the `UnsafeCell` pointer here. The state can only be + // poisoned at this point, so using `write` to skip the destructor + // of `State` should help the optimizer. + unsafe { this.state.get().write(State::Init(data)) }; // SAFETY: - // A reference obtained by downcasting from the mutable borrow would - // become stale the next time `force` is called (since there is a conflict - // between the mutable reference here and the shared reference there). - // Do a new shared borrow of the state instead. + // The previous references were invalidated by the `write` call above, + // so do a new shared borrow of the state instead. let state = unsafe { &*this.state.get() }; let State::Init(data) = state else { unreachable!() }; data |