diff options
Diffstat (limited to 'vendor/syn/src/thread.rs')
| -rw-r--r-- | vendor/syn/src/thread.rs | 20 |
1 files changed, 15 insertions, 5 deletions
diff --git a/vendor/syn/src/thread.rs b/vendor/syn/src/thread.rs index 63fdea834..b33d248af 100644 --- a/vendor/syn/src/thread.rs +++ b/vendor/syn/src/thread.rs @@ -12,6 +12,9 @@ pub(crate) struct ThreadBound<T> { unsafe impl<T> Sync for ThreadBound<T> {} // Send bound requires Copy, as otherwise Drop could run in the wrong place. +// +// Today Copy and Drop are mutually exclusive so `T: Copy` implies `T: !Drop`. +// This impl needs to be revisited if that restriction is relaxed in the future. unsafe impl<T: Copy> Send for ThreadBound<T> {} impl<T> ThreadBound<T> { @@ -40,11 +43,18 @@ impl<T: Debug> Debug for ThreadBound<T> { } } -impl<T: Clone> Clone for ThreadBound<T> { +// Copy the bytes of T, even if the currently running thread is the "wrong" +// thread. This is fine as long as the original thread is not simultaneously +// mutating this value via interior mutability, which would be a data race. +// +// Currently `T: Copy` is sufficient to guarantee that T contains no interior +// mutability, because _all_ interior mutability in Rust is built on +// std::cell::UnsafeCell, which has no Copy impl. This impl needs to be +// revisited if that restriction is relaxed in the future. +impl<T: Copy> Copy for ThreadBound<T> {} + +impl<T: Copy> Clone for ThreadBound<T> { fn clone(&self) -> Self { - ThreadBound { - value: self.value.clone(), - thread_id: self.thread_id, - } + *self } } |