Matthias Krüger b55cabe636
Rollup merge of #126285 - kpreid:unique-rc, r=dtolnay
`UniqueRc`: support allocators and `T: ?Sized`.

Added the following (all unstable):

* Defaulted type pararameter `A: Allocator`.
* `UniqueRc::new_in()`.
* `T:  ?Sized` where possible.
* `impl CoerceUnsized for UniqueRc`.

These changes are motivated by supporting the implementation of unsized `Rc::make_mut()` (PR #116113), but are also intended to be obvious generalizations of `UniqueRc` to support the things `Rc` does.

r? ``````@the8472``````
2024-06-14 12:23:37 +02:00
..