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| 1 | +//! A test of `#[manually_drop]` on a type that *does* have a `Drop` impl. |
| 2 | +//! |
| 3 | +//! The mirror image of `manually_drop-nodestructor.rs` |
| 4 | +#![feature(manually_drop_attr)] |
| 5 | +// run-pass |
| 6 | +extern crate core; |
| 7 | +use core::cell::Cell; |
| 8 | + |
| 9 | +struct DropCounter<'a>(&'a Cell<isize>); |
| 10 | +impl<'a> Drop for DropCounter<'a> { |
| 11 | + fn drop(&mut self) { |
| 12 | + self.0.set(self.0.get() + 1); |
| 13 | + } |
| 14 | +} |
| 15 | + |
| 16 | +#[manually_drop] |
| 17 | +struct ManuallyDropped<'a> { |
| 18 | + field_1: DropCounter<'a>, |
| 19 | + field_2: DropCounter<'a>, |
| 20 | +} |
| 21 | + |
| 22 | +impl<'a> Drop for ManuallyDropped<'a> { |
| 23 | + fn drop(&mut self) { |
| 24 | + // just do a LITTLE dropping. |
| 25 | + unsafe { |
| 26 | + core::ptr::drop_in_place(&mut self.field_1) |
| 27 | + } |
| 28 | + } |
| 29 | +} |
| 30 | + |
| 31 | +#[manually_drop] |
| 32 | +enum ManuallyDroppedEnum<'a> { |
| 33 | + _A, |
| 34 | + B(DropCounter<'a>, DropCounter<'a>), |
| 35 | +} |
| 36 | + |
| 37 | +impl<'a> Drop for ManuallyDroppedEnum<'a> { |
| 38 | + fn drop(&mut self) { |
| 39 | + // just do a LITTLE dropping. |
| 40 | + if let ManuallyDroppedEnum::B(a, _) = self { |
| 41 | + unsafe { |
| 42 | + core::ptr::drop_in_place(a); |
| 43 | + } |
| 44 | + } |
| 45 | + } |
| 46 | +} |
| 47 | + |
| 48 | +/// Dropping a `#[manually_drop]` struct does not implicitly drop its fields. |
| 49 | +/// |
| 50 | +/// (Though it does run `Drop`, which can choose to drop them explicitly.) |
| 51 | +fn test_destruction() { |
| 52 | + let counter = Cell::new(0); |
| 53 | + core::mem::drop(ManuallyDropped { |
| 54 | + field_1: DropCounter(&counter), |
| 55 | + field_2: DropCounter(&counter), |
| 56 | + }); |
| 57 | + // We only run the drop specifically requested in the Drop impl. |
| 58 | + assert_eq!(counter.get(), 1); |
| 59 | + assert!(core::mem::needs_drop::<ManuallyDropped>()); |
| 60 | + |
| 61 | + core::mem::drop(ManuallyDroppedEnum::B(DropCounter(&counter), DropCounter(&counter))); |
| 62 | + assert_eq!(counter.get(), 2); |
| 63 | + assert!(core::mem::needs_drop::<ManuallyDroppedEnum>()); |
| 64 | + |
| 65 | +} |
| 66 | + |
| 67 | +/// Assignment does still drop the fields. |
| 68 | +fn test_assignment() { |
| 69 | + let counter = Cell::new(0); |
| 70 | + let mut manually_dropped = ManuallyDropped { |
| 71 | + field_1: DropCounter(&counter), |
| 72 | + field_2: DropCounter(&counter), |
| 73 | + }; |
| 74 | + assert_eq!(counter.get(), 0); |
| 75 | + manually_dropped.field_1 = DropCounter(&counter); |
| 76 | + manually_dropped.field_2 = DropCounter(&counter); |
| 77 | + assert_eq!(counter.get(), 2); |
| 78 | +} |
| 79 | + |
| 80 | +fn main() { |
| 81 | + test_destruction(); |
| 82 | + test_assignment(); |
| 83 | +} |
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