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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 09:22:09 +0000
commit43a97878ce14b72f0981164f87f2e35e14151312 (patch)
tree620249daf56c0258faa40cbdcf9cfba06de2a846 /third_party/rust/syn/src/drops.rs
parentInitial commit. (diff)
downloadfirefox-43a97878ce14b72f0981164f87f2e35e14151312.tar.xz
firefox-43a97878ce14b72f0981164f87f2e35e14151312.zip
Adding upstream version 110.0.1.upstream/110.0.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/rust/syn/src/drops.rs')
-rw-r--r--third_party/rust/syn/src/drops.rs58
1 files changed, 58 insertions, 0 deletions
diff --git a/third_party/rust/syn/src/drops.rs b/third_party/rust/syn/src/drops.rs
new file mode 100644
index 0000000000..89b42d82ef
--- /dev/null
+++ b/third_party/rust/syn/src/drops.rs
@@ -0,0 +1,58 @@
+use std::iter;
+use std::mem::ManuallyDrop;
+use std::ops::{Deref, DerefMut};
+use std::option;
+use std::slice;
+
+#[repr(transparent)]
+pub(crate) struct NoDrop<T: ?Sized>(ManuallyDrop<T>);
+
+impl<T> NoDrop<T> {
+ pub(crate) fn new(value: T) -> Self
+ where
+ T: TrivialDrop,
+ {
+ NoDrop(ManuallyDrop::new(value))
+ }
+}
+
+impl<T: ?Sized> Deref for NoDrop<T> {
+ type Target = T;
+ fn deref(&self) -> &Self::Target {
+ &self.0
+ }
+}
+
+impl<T: ?Sized> DerefMut for NoDrop<T> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.0
+ }
+}
+
+pub(crate) trait TrivialDrop {}
+
+impl<T> TrivialDrop for iter::Empty<T> {}
+impl<'a, T> TrivialDrop for slice::Iter<'a, T> {}
+impl<'a, T> TrivialDrop for slice::IterMut<'a, T> {}
+impl<'a, T> TrivialDrop for option::IntoIter<&'a T> {}
+impl<'a, T> TrivialDrop for option::IntoIter<&'a mut T> {}
+
+#[test]
+fn test_needs_drop() {
+ use std::mem::needs_drop;
+
+ struct NeedsDrop;
+
+ impl Drop for NeedsDrop {
+ fn drop(&mut self) {}
+ }
+
+ assert!(needs_drop::<NeedsDrop>());
+
+ // Test each of the types with a handwritten TrivialDrop impl above.
+ assert!(!needs_drop::<iter::Empty<NeedsDrop>>());
+ assert!(!needs_drop::<slice::Iter<NeedsDrop>>());
+ assert!(!needs_drop::<slice::IterMut<NeedsDrop>>());
+ assert!(!needs_drop::<option::IntoIter<&NeedsDrop>>());
+ assert!(!needs_drop::<option::IntoIter<&mut NeedsDrop>>());
+}