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Auto merge of #77893 - petertodd:2020-impl-default-for-phantompinned, r=dtolnay

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Impl Default for PhantomPinned

`PhantomPinned` is just a marker type, with an obvious default value (the only value). So I can't think of a reason not to do this. Sure, it's used in exotic situations with unsafe code. But the people writing that code can decide for themselves if they can derive `Default`, and in many situations the derived impl will make sense:

```rust
#[derive(Default)]
struct NeedsPin {
   marker: PhantomPinned,
   buf: [u8; 1024],
   ptr_to_data: Option<*const u8>,
}
```
This commit is contained in:
bors 2020-11-23 07:00:30 +00:00
commit 068320b39e
1 changed files with 1 additions and 1 deletions
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library/core/src/marker.rs
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@ -775,7 +775,7 @@ pub auto trait Unpin {}
///
/// If a type contains a `PhantomPinned`, it will not implement `Unpin` by default.
#[stable(feature = "pin", since = "1.33.0")]
#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
#[derive(Debug, Default, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
pub struct PhantomPinned;
#[stable(feature = "pin", since = "1.33.0")]