mirror of https://github.com/torvalds/linux.git
61 lines
1.4 KiB
Rust
61 lines
1.4 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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use std::iter;
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use std::mem::ManuallyDrop;
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use std::ops::{Deref, DerefMut};
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use std::option;
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use std::slice;
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#[repr(transparent)]
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pub(crate) struct NoDrop<T: ?Sized>(ManuallyDrop<T>);
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impl<T> NoDrop<T> {
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pub(crate) fn new(value: T) -> Self
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where
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T: TrivialDrop,
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{
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NoDrop(ManuallyDrop::new(value))
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}
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}
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impl<T: ?Sized> Deref for NoDrop<T> {
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type Target = T;
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fn deref(&self) -> &Self::Target {
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&self.0
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}
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}
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impl<T: ?Sized> DerefMut for NoDrop<T> {
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fn deref_mut(&mut self) -> &mut Self::Target {
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&mut self.0
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}
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}
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pub(crate) trait TrivialDrop {}
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impl<T> TrivialDrop for iter::Empty<T> {}
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impl<T> TrivialDrop for slice::Iter<'_, T> {}
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impl<T> TrivialDrop for slice::IterMut<'_, T> {}
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impl<T> TrivialDrop for option::IntoIter<&T> {}
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impl<T> TrivialDrop for option::IntoIter<&mut T> {}
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#[test]
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fn test_needs_drop() {
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use std::mem::needs_drop;
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struct NeedsDrop;
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impl Drop for NeedsDrop {
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fn drop(&mut self) {}
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}
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assert!(needs_drop::<NeedsDrop>());
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// Test each of the types with a handwritten TrivialDrop impl above.
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assert!(!needs_drop::<iter::Empty<NeedsDrop>>());
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assert!(!needs_drop::<slice::Iter<NeedsDrop>>());
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assert!(!needs_drop::<slice::IterMut<NeedsDrop>>());
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assert!(!needs_drop::<option::IntoIter<&NeedsDrop>>());
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assert!(!needs_drop::<option::IntoIter<&mut NeedsDrop>>());
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}
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