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Adjust argument type for mutable with_metadata_of (#75091) #103346

Merged
merged 2 commits into from
Oct 22, 2022
Merged

Adjust argument type for mutable with_metadata_of (#75091) #103346

merged 2 commits into from
Oct 22, 2022

Commits on Oct 21, 2022

  1. Argument type for mutable with_metadata_of (rust-lang#75091) 

    The method takes two pointer arguments: one `self` supplying the pointer
value, and a second pointer supplying the metadata.

The new parameter type more clearly reflects the actual requirements.
The provenance of the metadata parameter is disregarded completely.
Using a mutable pointer in the call site can be coerced to a const
pointer while the reverse is not true.

An example of the current use:

```rust
// Manually taking an unsized object from a `ManuallyDrop` into another allocation.
let val: &core::mem::ManuallyDrop<T> = …;

let ptr = val as *const _ as *mut T;
let ptr = uninit.as_ptr().with_metadata_of(ptr);
```

This could then instead be simplified to:

```rust
// Manually taking an unsized object from a `ManuallyDrop` into another allocation.
let val: &core::mem::ManuallyDrop<T> = …;

let ptr = uninit.as_ptr().with_metadata_of(&**val);
```
    Andreas Molzer committed Oct 21, 2022
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  2. Reduce mutability in std-use of with_metadata_of

    Andreas Molzer committed Oct 21, 2022
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