Migrate unit tests of btree collections to their native breeding ground
There's one BTreeSet test case that I couldn't easily convince to come along, maybe because it truly is an integration test. But leaving it in place would mean git wouldn't see the move so I also moved it to a new file.
r? @Mark-Simulacrum
BTreeMap: purge innocent use of into_kv_mut
Replace the use of `into_kv_mut` into more precise calls. This makes more sense if you know that the single remaining use of `into_kv_mut` is in fact evil and can be trialled in court (#75200) and sent to a correction facility (#73971).
No real performance difference reported (but functions that might benefit a tiny constant bit like `BTreeMap::get_mut` aren't benchmarked):
```
benchcmp old new --threshold 5
name old ns/iter new ns/iter diff ns/iter diff % speedup
btree::map::clone_fat_100 63,073 59,256 -3,817 -6.05% x 1.06
btree::map::iter_100 3,514 3,235 -279 -7.94% x 1.09
```
Change Debug impl of SocketAddr and IpAddr to match their Display output
This has already been done for `SocketAddrV4`, `SocketAddrV6`, `IpAddrV4` and `IpAddrV6`. I don't see a point to keep the rather bad to read derived impl, especially so when pretty printing:
V4(
127.0.0.1
)
From the `Display`, one can easily and unambiguously see if it's V4 or V6. Two examples:
```
127.0.0.1:443
[2001:db8:85a3::8a2e:370:7334]:443
```
Luckily the docs explicitly state that `Debug` output is not stable and that it may be changed at any time.
Using `Display` as `Debug` is very convenient for configuration structs (e.g. for webservers) that often just have a `derive(Debug)` and are printed that way to the one starting the server.
Improve documentation on process::Child.std* fields
As a relative beginner, it took a while for me to figure out I could just steal the references to avoid partially moving the child and thus retain ability to call functions on it (and store it in structs etc).
This solves several problems
- race conditions where a file is truncated while copying from it. if we blindly trusted
the file size this would lead to an infinite loop
- proc files appearing empty to copy_file_range but not to read/write
https://github.com/coreutils/coreutils/commit/4b04a0c
- copy_file_range returning 0 for some filesystems (overlay? bind mounts?)
inside docker, again leading to an infinite loop
Constified str::from_utf8_unchecked
This would be useful for const code to use an array to construct a string using guaranteed utf8 inputs, and then create a `&str` from it.
As a relative beginner, it took a while for me to figure out I could just steal the references to avoid partially moving the child and thus retain ability to call functions on it (and store it in structs etc).
Stop BTreeMap casts from reborrowing
Down in btree/node.rs, the interface and use of `cast_unchecked` look a bit shady. It's really just there for inverting `forget_type` which does not borrow. By borrowing we can't write the same `cast_unchecked` in the same way at the Handle level.
No change in undefined behaviour or performance.
Expand function pointer docs
Be more explicit in the ABI section, and add a section on how to obtain a function pointer, which can be somewhat confusing.
Cc https://github.com/rust-lang/rust/issues/75239
Hard way to respect BTreeMap's minimum node length
Resolves#74834 the hard way (though not the hardest imaginable).
Benchmarks (which are all biased/realistic, inserting keys in ascending order) say:
```
benchcmp r0 r1 --threshold 10
name r0 ns/iter r1 ns/iter diff ns/iter diff % speedup
btree::map::clone_slim_100_and_clear 2,183 2,723 540 24.74% x 0.80
btree::map::clone_slim_100_and_drain_all 3,652 4,173 521 14.27% x 0.88
btree::map::clone_slim_100_and_drain_half 3,320 3,940 620 18.67% x 0.84
btree::map::clone_slim_100_and_into_iter 2,154 2,717 563 26.14% x 0.79
btree::map::clone_slim_100_and_pop_all 3,372 3,870 498 14.77% x 0.87
btree::map::clone_slim_100_and_remove_all 5,111 5,647 536 10.49% x 0.91
btree::map::clone_slim_100_and_remove_half 3,259 3,821 562 17.24% x 0.85
btree::map::iter_0 1,733 1,509 -224 -12.93% x 1.15
btree::map::iter_100 2,714 3,739 1,025 37.77% x 0.73
btree::map::iter_10k 3,728 4,269 541 14.51% x 0.87
btree::map::range_unbounded_unbounded 28,426 36,631 8,205 28.86% x 0.78
btree::map::range_unbounded_vs_iter 28,808 34,056 5,248 18.22% x 0.85
```
This difference is not caused by the `debug_assert`-related code in the function `splitpoint`, it's the same without.
Add `array` lang item and `[T; N]::map(f: FnMut(T) -> S)`
This introduces an `array` lang item so functions can be defined on top of `[T; N]`. This was previously not done because const-generics was not complete enough to allow for this. Now it is in a state that is usable enough to start adding functions.
The function added is a monadic (I think?) map from `[T; N] -> [S; N]`. Until transmute can function on arrays, it also allocates an extra temporary array, but this can be removed at some point.
r? @lcnr
Switch from indexing to zip, and also use `write` on `MaybeUninit`.
Add array_map feature to core/src/lib
Attempt to fix issue of no such feature
Update w/ pickfire's review
This changes a couple of names around, adds another small test of variable size,
and hides the rustdoc #![feature(..)].
Fmt doctest
Add suggestions from lcnr
Add basic test
And also run fmt which is where the other changes are from
Fix mut issues
These only appear when running tests, so resolved by adding mut
Swap order of forget
Add pub and rm guard impl
Add explicit type to guard
Add safety note
Change guard type from T to S
It should never have been T, as it guards over [MaybeUninit<S>; N]
Also add feature to test
This creates the language item for arrays, and adds the map fn which is like map in options or
iterators. It currently allocates an extra array, unfortunately.
Added fixme for transmuting
Fix typo
Add drop guard
