Less unsafe in the array example of MaybeUninit docs
I believe this is an acceptable way to initialize elements of `[MaybeUninit<T>; _]` arrays. Miri agrees. Conceptually, we are working at the array level, above the `MaybeUninit`, and as we are replacing it wholesale, this should pose no problem to soundness. And the code is easier to read.
r? @RalfJung
Revert "Set test flag when rustdoc is running with --test option"
Reverts https://github.com/rust-lang/rust/pull/59940.
It caused doctests in this repository to no longer be tested including all of the core crate.
Add std::mem::take as suggested in #61129
This PR implements #61129 by adding `std::mem::take`.
The added function is equivalent to:
```rust
std::mem::replace(dest, Default::default())
```
This particular pattern is fairly common, especially when implementing `Future::poll`, where you often need to yield an owned value in `Async::Ready`. This change allows you to write
```rust
return Async::Ready(std::mem::take(self.result));
```
instead of
```rust
return Async::Ready(std::mem::replace(self.result, Vec::new()));
```
EDIT: Changed name from `take` to `swap_default`.
EDIT: Changed name back to `take`.
The name `swap_default` was suggested but rejected. @SimonSapin observed
that this operation isn't really a `swap` in the same sense as
`mem::swap`; it is a `replace`. Since `replace_default` is a bit
misleading, the "correct" name would be `replace_with_default`, which is
quite verbose.
@czipperz observed that we have precedence for using `take` to refer to
methods that replace with `Default` in `Cell::take` and `Option::take`,
so this reverts commit 99c00591c29b472c8a87c4a9342d0e0c508647a3 to
return to the original `take` method name.
The name `replace_with_default` was suggested, but was deemed too
verbose, especially given that we use `take` for methods that replace
with `Default` elsewhere.
