Test and fix Send and Sync traits of BTreeMap artefacts
Fixes#76686.
I'm not quite sure what all this implies. E.g. comparing with the definitions for `NodeRef` in node.rs, maybe an extra bound `T: 'a` is useful for something. The test compiles on stable/beta (apart from `drain_filter`) so I bet `Sync` is equally desirable.
r? @Mark-Simulacrum
BTreeMap: wrap node's raw parent pointer in NonNull
Now that the other `*const` (root) is gone, seemed like a small step forward.
r? `@Mark-Simulacrum`
Add as_str() to string::Drain.
Vec's Drain recently [had its `.as_slice()` stabilized](https://github.com/rust-lang/rust/pull/72584), but String's Drain was still missing the analogous `.as_str()`. This adds that.
Also improves the Debug implementation, which now shows the remaining data instead of just `"Drain { .. }"`.
Add associated constant `BITS` to all integer types
Recently I've regularly come across this snippet (in a few different crates, including `core` and `std`):
```rust
std::mem::size_of<usize>() * 8
```
I think it's time for a `usize::BITS`.
do not inline black_box when building for Miri
We cannot do the assembly trick in Miri, but let's at least make sure MIR inlining does not circumvent the black_box.
Also use black_box instead of local optimization barriers in a few const tests.
deny(unsafe_op_in_unsafe_fn) in libstd/path.rs
The libstd/path.rs part of #73904 . Wraps the two calls to an unsafe fn Initializer::nop() in an unsafe block.
BTreeMap: avoid slices even more
Epilogue to #73971: it seems the compiler is unable to realize that creating a slice and `get_unchecked`-ing one element is a simple fetch. So try to spell it out for the only remaining but often invoked case.
Also, the previous code doesn't seem fair game to me, using `get_unchecked` to reach beyond the end of a slice. Although the local function `slice_insert` also does that.
r? `@Mark-Simulacrum`
Small cleanups in Windows Mutex.
- Move `held` into the boxed part, since the SRW lock implementation does not use this. This makes the Mutex 50% smaller.
- Use `Cell` instead of `UnsafeCell` for `held`, such that `.replace()` can be used.
- Add some comments.
- Avoid creating multiple `&mut`s to the critical section object in `ReentrantMutex`.
[fuchsia] Propagate the userspace UTC clock
On Fuchsia, spawning a subprocess does not automatically
clone all of the parent process' capabilities. UTC time on
Fuchsia is managed by a top-level userspace clock capability
that is cloned and passed to subprocesses.
This change ensures that any Rust subprocess gets access to the
UTC clock, if the parent had access to it. This is critical for
tests, which on Fuchsia, use panic=abort and spawn subprocesses
per test.
Add array_windows fn
This mimicks the functionality added by array_chunks, and implements a const-generic form of
`windows`. It makes egregious use of `unsafe`, but by necessity because the array must be
re-interpreted as a slice of arrays, and unlike array_chunks this cannot be done by casting the
original array once, since each time the index is advanced it needs to move one element, not
`N`.
I'm planning on adding more tests, but this should be good enough as a premise for the functionality.
Notably: should there be more functions overwritten for the iterator implementation/in general?
~~I've marked the issue as #74985 as there is no corresponding exact issue for `array_windows`, but it's based of off `array_chunks`.~~
Edit: See Issue #75027 created by @lcnr for tracking issue
~~Do not merge until I add more tests, please.~~
r? @lcnr
