Add proc_macro::Span::{before, after}.
This adds `proc_macro::Span::before()` and `proc_macro::Span::after()` to get a zero width span at the start or end of the span.
These are equivalent to rustc's `Span::shrink_to_lo()` and `Span::shrink_to_hi()` but with a less cryptic name. They are useful when generating diagnostlics like "missing \<thing\> after \<thing\>".
E.g.
```rust
syn::Error::new(ident.span().after(), "missing `:` after field name").into_compile_error()
```
Correct “copies” to “moves” in `<Option<T> as From<T>>::from` doc, and other copyediting
The `impl<T> From<T> for Option<T>` has no `Copy` or `Clone` bound, so its operation is guaranteed to be a move. The call site might copy, but the function itself cannot.
Since that would have been a rather small PR, I also reviewed the other documentation in the file and made other improvements (in separate commits): adding periods and commas, linking `Deref::Target`, and clarifying what "a container" is in `FromIterator`.
More symbolic doc aliases
A bunch of small changes, mostly adding `#[doc(alias = "…")]` entries for symbolic `"…"`.
Also a small change in documentation of `const` keywords.
Suggest deriving traits if possible
This only applies to builtin derives as I don't think there is a
clean way to get the available derives in typeck.
Closes#85851
BTreeMap/BTreeSet::from_iter: use bulk building to improve the performance
Bulk building is a common technique to increase the performance of building a fresh btree map. Instead of inserting items one-by-one, we sort all the items beforehand then create the BtreeMap in bulk.
Benchmark
```
./x.py bench library/alloc --test-args btree::map::from_iter
```
* Before
```
test btree::map::from_iter_rand_100 ... bench: 3,694 ns/iter (+/- 840)
test btree::map::from_iter_rand_10_000 ... bench: 1,033,446 ns/iter (+/- 192,950)
test btree::map::from_iter_seq_100 ... bench: 5,689 ns/iter (+/- 1,259)
test btree::map::from_iter_seq_10_000 ... bench: 861,033 ns/iter (+/- 118,815)
```
* After
```
test btree::map::from_iter_rand_100 ... bench: 3,033 ns/iter (+/- 707)
test btree::map::from_iter_rand_10_000 ... bench: 775,958 ns/iter (+/- 105,152)
test btree::map::from_iter_seq_100 ... bench: 2,969 ns/iter (+/- 336)
test btree::map::from_iter_seq_10_000 ... bench: 258,292 ns/iter (+/- 29,364)
```
Document when to use Windows' `symlink_dir` vs. `symlink_file`
It was previously unclear why there are two functions and when they should be used.
Fixes: #88635
Add links in docs for some primitive types
This pull request adds additional links in existing documentation of some of the primitive types.
Where items are linked only once, I have used the `[link](destination)` format. For items in `std`, I have linked directly to the HTML, since although the primitives are in `core`, they are not displayed on `core` documentation. I was unsure of what length I should keep lines of documentation to, so I tried to keep them within reason.
Additionally, I have avoided excessively linking to keywords like `self` when they are not relevant to the documentation. I can add these links if it would be an improvement.
I hope this can improve Rust. Please let me know if there's anything I did wrong!
This implementation has no `Copy` or `Clone` bound, so its operation is
guaranteed to be a move. The call site might copy, but the function
itself cannot.
Also linkify `Some` while we're touching the line anyway.
remove redundant / misplaced sentence from docs
Removes sentence that seems to have drifted down into the examples section. Luckily, someone already added an explanation of what happens with packed structs back into the initial section of the doc entry and this wayward sentence can likely just be deleted.
Add an example for deriving PartialOrd on enums
For some reason, I always forget which variants are smaller and which
are larger when you derive PartialOrd on an enum. And the wording in the
current docs is not entirely clear to me.
So, I often end up making a small enum, deriving PartialOrd on it, and
then writing a `#[test]` with an assert that the top one is smaller than
the bottom one (or the other way around) to figure out which way the
deriving goes.
So then I figured, it would be great if the standard library docs just
had that example, so if I keep forgetting, at least I can figure it out
quickly by looking at std's docs.
`fmt::Formatter::pad`: don't call chars().count() more than one time
First commit merges two branches of match to call chars().count() only once: that should be faster if this method hits place of 3rd (previous) branch, plus quarter shorter.
Second commit fixes some clippy lints while i'm here (should it be separate PR?).
Stabilize std::os::unix::fs::chroot
I've verified that this works as documented, and I've tested it in (a nightly
build of) production software as a replacement for an unsafe call to
`libc::chroot`. It's been available in nightly for a few releases. I think it's
ready to stabilize.
---
Tracking issue: https://github.com/rust-lang/rust/issues/84715
Allow writing of incomplete UTF-8 sequences to the Windows console via stdout/stderr
# Problem
Writes of just an incomplete UTF-8 byte sequence (e.g. `b"\xC3"` or `b"\xF0\x9F"`) to stdout/stderr with a Windows console attached error with `io::ErrorKind::InvalidData, "Windows stdio in console mode does not support writing non-UTF-8 byte sequences"` even though further writes could complete the codepoint. This is currently a rare occurence since the [linewritershim](2c56ea38b0/library/std/src/io/buffered/linewritershim.rs) implementation flushes complete lines immediately and buffers up to 1024 bytes for incomplete lines. It can still happen as described in #83258.
The problem will become more pronounced once the developer can switch stdout/stderr from line-buffered to block-buffered or immediate when the changes in the "Switchable buffering for Stdout" pull request (#78515) get merged.
# Patch description
If there is at least one valid UTF-8 codepoint all valid UTF-8 is passed through to the extracted `write_valid_utf8_to_console()` fn. The new code only comes into play if `write()` is being passed a short byte slice comprising an incomplete UTF-8 codepoint. In this case up to three bytes are buffered in the `IncompleteUtf8` struct associated with `Stdout` / `Stderr`. The bytes are accepted one at a time. As soon as an error can be detected `io::ErrorKind::InvalidData, "Windows stdio in console mode does not support writing non-UTF-8 byte sequences"` is returned. Once a complete UTF-8 codepoint is received it is passed to the `write_valid_utf8_to_console()` and the buffer length is set to zero.
Calling `flush()` will neither error nor write anything if an incomplete codepoint is present in the buffer.
# Tests
Currently there are no Windows-specific tests for console writing code at all. Writing (regression) tests for this problem is a bit challenging since unit tests and UI tests don't run in a console and suddenly popping up another console window might be surprising to developers running the testsuite and it might not work at all in CI builds. To just test the new functionality in unit tests the code would need to be refactored. Some guidance on how to proceed would be appreciated.
# Public API changes
* `std::str::verifications::utf8_char_width()` would be exposed as `std::str::utf8_char_width()` behind the "str_internals" feature gate.
# Related issues
* Fixes#83258.
* PR #78515 will exacerbate the problem.
# Open questions
* Add tests?
* Squash into one commit with better commit message?
