Consolidate Result's and Option's methods into fewer impl blocks
`Result`'s and `Option`'s methods have historically been separated up into `impl` blocks based on their trait bounds, with the bounds specified on type parameters of the impl block. I find this unhelpful because closely related methods, like `unwrap_or` and `unwrap_or_default`, end up disproportionately far apart in source code and rustdocs:
<pre>
impl<T> Option<T> {
pub fn unwrap_or(self, default: T) -> T {
...
}
<img alt="one eternity later" src="https://user-images.githubusercontent.com/1940490/147780325-ad4e01a4-c971-436e-bdf4-e755f2d35f15.jpg" width="750">
}
impl<T: Default> Option<T> {
pub fn unwrap_or_default(self) -> T {
...
}
}
</pre>
I'd prefer for method to be in as few impl blocks as possible, with the most logical grouping within each impl block. Any bounds needed can be written as `where` clauses on the method instead:
```rust
impl<T> Option<T> {
pub fn unwrap_or(self, default: T) -> T {
...
}
pub fn unwrap_or_default(self) -> T
where
T: Default,
{
...
}
}
```
*Warning: the end-to-end diff of this PR is computed confusingly by git / rendered confusingly by GitHub; it's practically impossible to review that way. I've broken the PR into commits that move small groups of methods for which git behaves better — these each should be easily individually reviewable.*
Track caller of slice split and swap
Improves error location for `slice.split_at*()` and `slice.swap()`.
These are generic inline functions, so the `#[track_caller]` on them is free — only changes a value of an argument already passed to panicking code.
Rollup of 7 pull requests
Successful merges:
- #84083 (Clarify the guarantees that ThreadId does and doesn't make.)
- #91593 (Remove unnecessary bounds for some Hash{Map,Set} methods)
- #92297 (Reduce compile time of rustbuild)
- #92332 (Add test for where clause order)
- #92438 (Enforce formatting for rustc_codegen_cranelift)
- #92463 (Remove pronunciation guide from Vec<T>)
- #92468 (Emit an error for `--cfg=)`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Remove unnecessary bounds for some Hash{Map,Set} methods
This PR moves `HashMap::{into_keys,into_values,retain}` and `HashSet::retain` from `impl` blocks with `K: Eq + Hash, S: BuildHasher` into the blocks without them. It doesn't seem to me there is any reason these methods need to be bounded by that. This change brings `HashMap::{into_keys,into_values}` on par with `HashMap::{keys,values,values_mut}` which are not bounded either.
Clarify the guarantees that ThreadId does and doesn't make.
The existing documentation does not spell out whether `ThreadId`s are unique during the lifetime of a thread or of a process. I had to examine the source code to realise (pleasingly!) that they're unique for the lifetime of a process. That seems worth documenting clearly, as it's a strong guarantee.
Examining the way `ThreadId`s are created also made me realise that the `as_u64` method on `ThreadId` could be a trap for the unwary on those platforms where the platform's notion of a thread identifier is also a 64 bit integer (particularly if they happen to use a similar identifier scheme to `ThreadId`). I therefore think it's worth being even clearer that there's no relationship between the two.
Remove CommandEnv::apply
It's not being used and uses unsound set_var and remove_var functions. This is an internal function that isn't exported (even with `process_internals` feature), so this shouldn't break anything.
Also see #92365. Note that this isn't the only use of those methods in standard library, so that particular pull request will need more changes than just this to work (in particular, `test_capture_env_at_spawn` is using `set_var` and `remove_var`).
Implement split_at_spare_mut without Deref to a slice so that the spare slice is valid
~I'm not sure I understand what's going on here correctly. And I'm pretty sure this safety comment needs to be changed. I'm just referring to the same thing that `as_mut_ptr_range` does.~ (Thanks `@RalfJung` for the guidance and clearing things up)
I tried to run https://github.com/rust-lang/miri-test-libstd on alloc with -Zmiri-track-raw-pointers, and got a failure on the test `vec::test_extend_from_within`.
I minimized the test failure into this program:
```rust
#![feature(vec_split_at_spare)]
fn main() {
Vec::<i32>::with_capacity(1).split_at_spare_mut();
}
```
The problem is that the existing implementation is actually getting a pointer range where both pointers are derived from the initialized region of the Vec's allocation, but we need the second one to be valid for the region between len and capacity. (thanks Ralf for clearing this up)
Add try_reserve and try_reserve_exact for OsString
Add `try_reserve` and `try_reserve_exact` for OsString.
Part of https://github.com/rust-lang/rust/issues/91789
I will squash the commits after PR is ready to merge.
Signed-off-by: Xuanwo <github@xuanwo.io>
It appears `find_max_slow` comes from the BinaryHeap docs, where the
try_reserve example is a slow implementation of find_max. It has no
relevance to this code in OsString though.
The crate name is already set in Cargo.toml. The comment says there is
some logic in the compiler that reads #![crate_name] and not
--crate-name, but I can't find it. Removing it seems to work fine.
Remove `maybe_uninit_extra` feature from Vec docs
In `Vec`, two doc tests are using `MaybeUninit::write` , stabilized in 1.55. This makes docs' usage of `maybe_uninit_extra` feature unnecessary.
Add `#[inline]` modifier to `TypeId::of`
It was already inlined but it happened only in 4th InlinerPass on my testcase.
With `#[inline]` modifier it happens on 2nd pass.
Closes#74362
RawVec: don't recompute capacity after allocating.
Currently it sets the capacity to `ptr.len() / mem::size_of::<T>()`
after any buffer allocation/reallocation. This would be useful if
allocators ever returned a `NonNull<[u8]>` with a size larger than
requested. But this never happens, so it's not useful.
Removing this slightly reduces the size of generated LLVM IR, and
slightly speeds up the hot path of `RawVec` growth.
r? `@ghost`
disable test with self-referential generator on Miri
Running the libcore test suite in Miri currently fails due to the known incompatibility of self-referential generators with Miri's aliasing checks (https://github.com/rust-lang/unsafe-code-guidelines/issues/148). So let's disable that test in Miri for now.
Use panic() instead of panic!() in some places in core.
See https://github.com/rust-lang/rust/pull/92068 and https://github.com/rust-lang/rust/pull/92140.
This avoids the `panic!()` macro in a few potentially hot paths. This becomes more relevant when switching `core` to Rust 2021, as it'll avoid format_args!() and save some compilation time. (It doesn't make a huge difference, but still.) (Also the errors in const panic become slightly nicer.)
Quote bat script command line
Fixes#91991
[`CreateProcessW`](https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessw#parameters) should only be used to run exe files but it does have some (undocumented) special handling for files with `.bat` and `.cmd` extensions. Essentially those magic extensions will cause the parameters to be automatically rewritten. Example pseudo Rust code (note that `CreateProcess` starts with an optional application name followed by the application arguments):
```rust
// These arguments...
CreateProcess(None, `@"foo.bat` "hello world""`@,` ...);
// ...are rewritten as
CreateProcess(Some(r"C:\Windows\System32\cmd.exe"), `@""foo.bat` "hello world"""`@,` ...);
```
However, when setting the first parameter (the application name) as we now do, it will omit the extra level of quotes around the arguments:
```rust
// These arguments...
CreateProcess(Some("foo.bat"), `@"foo.bat` "hello world""`@,` ...);
// ...are rewritten as
CreateProcess(Some(r"C:\Windows\System32\cmd.exe"), `@"foo.bat` "hello world""`@,` ...);
```
This means the arguments won't be passed to the script as intended.
Note that running batch files this way is undocumented but people have relied on this so we probably shouldn't break it.
Change Backtrace::enabled atomic from SeqCst to Relaxed
This atomic is not synchronizing anything outside of its own value, so we don't need the `Acquire`/`Release` guarantee that all memory operations prior to the store are visible after the subsequent load, nor the `SeqCst` guarantee of all threads seeing all of the sequentially consistent operations in the same order.
Using `Relaxed` reduces the overhead of `Backtrace::capture()` in the case that backtraces are not enabled.
## Benchmark
```rust
#![feature(backtrace)]
use std::backtrace::Backtrace;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread;
use std::time::Instant;
fn main() {
let begin = Instant::now();
let mut threads = Vec::new();
for _ in 0..64 {
threads.push(thread::spawn(|| {
for _ in 0..10_000_000 {
let _ = Backtrace::capture();
static LOL: AtomicUsize = AtomicUsize::new(0);
LOL.store(1, Ordering::Release);
}
}));
}
for thread in threads {
let _ = thread.join();
}
println!("{:?}", begin.elapsed());
}
```
**Before:** 6.73 seconds
**After:** 5.18 seconds
Allow reverse iteration of lowercase'd/uppercase'd chars
The PR implements `DoubleEndedIterator` trait for `ToLowercase` and `ToUppercase`.
This enables reverse iteration of lowercase/uppercase variants of character sequences.
One of use cases: determining whether a char sequence is a suffix of another one.
Example:
```rust
fn endswith_ignore_case(s1: &str, s2: &str) -> bool {
for eob in s1
.chars()
.flat_map(|c| c.to_lowercase())
.rev()
.zip_longest(s2.chars().flat_map(|c| c.to_lowercase()).rev())
{
match eob {
EitherOrBoth::Both(c1, c2) => {
if c1 != c2 {
return false;
}
}
EitherOrBoth::Left(_) => return true,
EitherOrBoth::Right(_) => return false,
}
}
true
}
```
Currently it sets the capacity to `ptr.len() / mem::size_of::<T>()`
after any buffer allocation/reallocation. This would be useful if
allocators ever returned a `NonNull<[u8]>` with a size larger than
requested. But this never happens, so it's not useful.
Removing this slightly reduces the size of generated LLVM IR, and
slightly speeds up the hot path of `RawVec` growth.
The previous implementation used slice::as_mut_ptr_range to derive the
pointer for the spare capacity slice. This is invalid, because that
pointer is derived from the initialized region, so it does not have
provenance over the uninitialized region.
Update example code for Vec::splice to change the length
The current example for `Vec::splice` illustrates the replacement of a section of length 2 with a new section of length 2. This isn't a particularly interesting case for splice, and makes it look a bit like a shorthand for the kind of manipulations that could be done with a mutable slice.
In order to provide a stronger example, this updates the example to use different lengths for the source and destination regions, and uses a slice from the middle of the vector to illustrate that this does not necessarily have to be at the beginning or the end.
Resolves#92067
Revert "Temporarily rename int_roundings functions to avoid conflicts"
This reverts commit 3ece63b64e.
This should be okay because #90329 has been merged.
r? `@joshtriplett`
The src pointers in CopyOnDrop and InsertionHole used to be *mut T, and
were derived via automatic conversion from &mut T. According to Stacked
Borrows 2.1, this means that those pointers become invalidated by
interior mutation in the comparison function.
But there's no need for mutability in this code path. Thus, we can
change the drop guards to use *const and derive those from &T.
Add a space and 2 grave accents
I only noticed this because I have this implementation copy pasted in some places in my code and I really can't wait for this to be stabilized...
Update stdlib to the 2021 edition
progress towards https://github.com/rust-lang/rust/issues/88638
I couldnt find a way to run the 2018 style panic tests against 2018 so I just deleted them, maybe theres a way to do it that I missed though?
