94 lines
2.3 KiB
Rust
94 lines
2.3 KiB
Rust
#![allow(unused)]
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use std::ops::{Deref, DerefMut};
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use std::mem::ManuallyDrop;
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#[derive(Default)]
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struct MockBox<T> {
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value: [T; 1],
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}
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impl<T> MockBox<T> {
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fn new(value: T) -> Self { MockBox { value: [value] } }
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}
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impl<T> Deref for MockBox<T> {
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type Target = T;
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fn deref(&self) -> &T { &self.value[0] }
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}
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impl<T> DerefMut for MockBox<T> {
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fn deref_mut(&mut self) -> &mut T { &mut self.value[0] }
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}
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#[derive(Default)]
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struct MockVec<T> {
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value: [T; 0],
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}
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impl<T> MockVec<T> {
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fn new() -> Self { MockVec { value: [] } }
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}
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impl<T> Deref for MockVec<T> {
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type Target = [T];
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fn deref(&self) -> &[T] { &self.value }
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}
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impl<T> DerefMut for MockVec<T> {
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fn deref_mut(&mut self) -> &mut [T] { &mut self.value }
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}
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union U {
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x: ManuallyDrop<((MockVec<u8>, MockVec<u8>), MockVec<u8>)>,
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y: ManuallyDrop<MockBox<MockVec<u8>>>,
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}
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fn use_borrow<T>(_: &T) {}
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unsafe fn parent_sibling_borrow() {
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let mut u = U { x: ManuallyDrop::new(((MockVec::new(), MockVec::new()), MockVec::new())) };
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let a = &mut (*u.x).0;
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let b = &u.y; //~ ERROR cannot borrow `u` (via `u.y`)
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use_borrow(a);
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}
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unsafe fn parent_sibling_move() {
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let u = U { x: ManuallyDrop::new(((MockVec::new(), MockVec::new()), MockVec::new())) };
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let a = u.x.0; //~ERROR cannot move out of dereference
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let a = u.x;
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let b = u.y; //~ ERROR use of moved value: `u`
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}
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unsafe fn grandparent_sibling_borrow() {
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let mut u = U { x: ManuallyDrop::new(((MockVec::new(), MockVec::new()), MockVec::new())) };
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let a = &mut ((*u.x).0).0;
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let b = &u.y; //~ ERROR cannot borrow `u` (via `u.y`)
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use_borrow(a);
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}
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unsafe fn grandparent_sibling_move() {
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let u = U { x: ManuallyDrop::new(((MockVec::new(), MockVec::new()), MockVec::new())) };
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let a = (u.x.0).0; //~ERROR cannot move out of dereference
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let a = u.x;
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let b = u.y; //~ ERROR use of moved value: `u`
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}
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unsafe fn deref_sibling_borrow() {
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let mut u = U { y: ManuallyDrop::new(MockBox::default()) };
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let a = &mut *u.y;
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let b = &u.x; //~ ERROR cannot borrow `u` (via `u.x`)
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use_borrow(a);
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}
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unsafe fn deref_sibling_move() {
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let u = U { x: ManuallyDrop::new(((MockVec::new(), MockVec::new()), MockVec::new())) };
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// No way to test deref-move without Box in union
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// let a = *u.y;
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// let b = u.x; ERROR use of moved value: `u`
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}
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fn main() {}
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