Remove methods under Implementors on trait pages
As discussed at https://github.com/rust-lang/rust/issues/84326#issuecomment-842652412.
On a trait page, the "Implementors" section currently lists all methods of each implementor. That duplicates the method definitions on the trait itself, and is usually not very useful. So the implementors are collapsed by default. This PR changes rustdoc to just not render them at all. Any documentation specific to an implementor can be found by clicking through to the implementor's page.
This moves the "portability" info inside the `<summary>` tags so it is still visible on trait pages (as originally implemented in #79201). That also means it will be visible on struct/enum pages when methods are collapsed.
Add `#[doc(hidden)]` to all implementations of `Iterator::__iterator_get_unchecked` that didn't already have it. Otherwise, due to #86145, the structs/enums with those implementations would generate documentation for them, and that documentation would have a broken link into the Iterator page. Those links were already "broken" but not detected by the link-checker, because they pointed to one of the Implementors on the Iterator page, which happened to have the right anchor name.
This reduces the Read trait's page size from 128kB to 68kB (uncompressed) and from 12,125 bytes to 9,989 bytes (gzipped
Demo:
https://hoffman-andrews.com/rust/remove-methods-implementors/std/string/struct.String.html#trait-implementationshttps://hoffman-andrews.com/rust/remove-methods-implementors/std/io/trait.Read.html#implementors
r? `@GuillaumeGomez`
This method on the Iterator trait is doc(hidden), and about half of
implementations were doc(hidden). This adds the attribute to the
remaining implementations.
Mention the `Borrow` guarantee on the `Hash` implementations for Arrays and `Vec`
To remind people like me who forget about it and send PRs to make them different, and to (probably) get a test failure if the code is changed to no longer uphold it.
To remind people like me who forget about it and send PRs to make them different, and to (probably) get a test failure if the code is changed to no longer uphold it.
String::remove_matches O(n^2) -> O(n)
Copy only non-matching bytes. Replace collection of matches into a
vector with iteration over rejections, exploiting the guarantee that we
mutate parts of the haystack that have already been searched over.
r? `@joshtriplett`
Update standard library for IntoIterator implementation of arrays
This PR partially resolves issue #84513 of updating the standard library part.
I haven't found any remaining doctest examples which are using iterators over e.g. &i32 instead of just i32 in the standard library. Can anyone point me to them if there's remaining any?
Thanks!
r? ```@m-ou-se```
## User-facing changes
- Intra-doc links to primitives that currently go to rust-lang.org/nightly/std/primitive.x.html will start going to channel that rustdoc was built with. Nightly will continue going to /nightly; Beta will link to /beta; stable compilers will link to /1.52.1 (or whatever version they were built as).
- Cross-crate links from std to core currently go to /nightly unconditionally. They will start going to /1.52.0 on stable channels (but remain the same on nightly channels).
- Intra-crate links from std to std (or core to core) currently go to the same URL they are hosted at; they will continue to do so. Notably, this is different from everything else because it can preserve the distinction between /stable and /1.52.0 by using relative links.
Note that "links" includes both intra-doc links and rustdoc's own
automatically generated hyperlinks.
## Implementation changes
- Update the testsuite to allow linking to /beta and /1.52.1 in docs
- Use an html_root_url for the standard library that's dependent on the channel
This avoids linking to nightly docs on stable.
- Update rustdoc to use channel-dependent links for primitives from an
unknown crate
- Set DOC_RUST_LANG_ORG_CHANNEL from bootstrap to ensure it's in sync
- Include doc.rust-lang.org in the channel
Add `String::extend_from_within`
This PR adds `String::extend_from_within` function under the `string_extend_from_within` feature gate similar to the [`Vec::extend_from_within`] function.
```rust
// String
pub fn extend_from_within<R>(&mut self, src: R)
where
R: RangeBounds<usize>;
```
[`Vec::extend_from_within`]: https://github.com/rust-lang/rust/issues/81656
This patch adds `String::extend_from_within` function under the
`string_extend_from_within` feature gate similar to the
`Vec::extend_from_within` function.
Enable Vec's calloc optimization for Option<NonZero>
Someone on discord noticed that `vec![None::<NonZeroU32>; N]` wasn't getting the optimization, so here's a PR 🙃
We can certainly do this in the standard library because we know for sure this is ok, but I think it's also a necessary consequence of documented guarantees like those in https://doc.rust-lang.org/std/option/#representation and https://doc.rust-lang.org/core/num/struct.NonZeroU32.html
It feels weird to do this without adding a test, but I wasn't sure where that would belong. Is it worth adding codegen tests for these?
Add `TrustedRandomAccess` specialization for `Vec::extend()`
This should do roughly the same as the `TrustedLen` specialization but result in less IR by using `__iterator_get_unchecked`
instead of `Iterator::for_each`
Conflicting specializations are manually prioritized by grouping them under yet another helper trait.
Weak's type parameter may dangle on drop
Way back in 34076bc0c9, #\[may_dangle\] was added to Rc\<T\> and Arc\<T\>'s Drop impls. That appears to have been because a test added in #28929 used Arc and Rc with dangling references at drop time. However, Weak was not covered by that test, and therefore no #\[may_dangle\] was forced to be added at the time.
As far as dropping, Weak has *even less need* to interact with the T than Rc and Arc do. Roughly speaking #\[may_dangle\] describes generic parameters that the outer type's Drop impl does not interact with except by possibly dropping them; no other interaction (such as trait method calls on the generic type) is permissible. It's clear this applies to Rc's and Arc's drop impl, which sometimes drop T but otherwise do not interact with one. It applies *even more* to Weak. Dropping a Weak cannot ever cause T's drop impl to run. Either there are strong references still in existence, in which case better not drop the T. Or there are no strong references still in existence, in which case the T would already have been dropped previously by the drop of the last strong count.
Avoid zero-length memcpy in formatting
This has two separate and somewhat orthogonal commits. The first change adjusts the ToString general impl for all types that implement Display; it no longer uses the full format machinery, rather directly falling onto a `std::fmt::Display::fmt` call. The second change directly adjusts the general core::fmt::write function which handles the production of format_args! to avoid zero-length push_str calls.
Both changes target the fact that push_str will still call memmove internally (or a similar function), as it doesn't know the length of the passed string. For zero-length strings in particular, this is quite expensive, and even for very short (several bytes long) strings, this is also expensive. Future work in this area may wish to have us fallback to write_char or similar, which may be cheaper on the (typically) short strings between the interpolated pieces in format_args!.
Implement the new desugaring from `try_trait_v2`
~~Currently blocked on https://github.com/rust-lang/rust/issues/84782, which has a PR in https://github.com/rust-lang/rust/pull/84811~~ Rebased atop that fix.
`try_trait_v2` tracking issue: https://github.com/rust-lang/rust/issues/84277
Unfortunately this is already touching a ton of things, so if you have suggestions for good ways to split it up, I'd be happy to hear them. (The combination between the use in the library, the compiler changes, the corresponding diagnostic differences, even MIR tests mean that I don't really have a great plan for it other than trying to have decently-readable commits.
r? `@ghost`
~~(This probably shouldn't go in during the last week before the fork anyway.)~~ Fork happened.
This avoids a zero-length write_str call, which boils down to a zero-length
memmove and ultimately costs quite a few instructions on some workloads.
This is approximately a 0.33% instruction count win on diesel-check.
BTree: no longer copy keys and values before dropping them
When dropping BTreeMap or BTreeSet instances, keys-value pairs are up to now each copied and then dropped, at least according to source code. This is because the code for dropping and for iterators is shared.
This PR postpones the treatment of doomed key-value pairs from the intermediate functions `deallocating_next`(`_back`) to the last minute, so the we can drop the keys and values in place. According to the library/alloc benchmarks, this does make a difference, (and a positive difference with an `#[inline]` on `drop_key_val`). It does not change anything for #81444 though.
r? `@Mark-Simulacrum`
Stablize {HashMap,BTreeMap}::into_{keys,values}
I would propose to stabilize `{HashMap,BTreeMap}::into_{keys,values}`( aka. `map_into_keys_values`).
Closes#75294.
For certain sorts of systems, programming, it's deemed essential that
all allocation failures be explicitly handled where they occur. For
example, see Linus Torvald's opinion in [1]. Merely not calling global
panic handlers, or always `try_reserving` first (for vectors), is not
deemed good enough, because the mere presence of the global OOM handlers
is burdens static analysis.
One option for these projects to use rust would just be to skip `alloc`,
rolling their own allocation abstractions. But this would, in my
opinion be a real shame. `alloc` has a few `try_*` methods already, and
we could easily have more. Features like custom allocator support also
demonstrate and existing to support diverse use-cases with the same
abstractions.
A natural way to add such a feature flag would a Cargo feature, but
there are currently uncertainties around how std library crate's Cargo
features may or not be stable, so to avoid any risk of stabilizing by
mistake we are going with a more low-level "raw cfg" token, which
cannot be interacted with via Cargo alone.
Note also that since there is no notion of "default cfg tokens" outside
of Cargo features, we have to invert the condition from
`global_oom_handling` to to `not(no_global_oom_handling)`. This breaks
the monotonicity that would be important for a Cargo feature (i.e.
turning on more features should never break compatibility), but it
doesn't matter for raw cfg tokens which are not intended to be
"constraint solved" by Cargo or anything else.
To support this use-case we create a new feature, "global-oom-handling",
on by default, and put the global OOM handler infra and everything else
it that depends on it behind it. By default, nothing is changed, but
users concerned about global handling can make sure it is disabled, and
be confident that all OOM handling is local and explicit.
For this first iteration, non-flat collections are outright disabled.
`Vec` and `String` don't yet have `try_*` allocation methods, but are
kept anyways since they can be oom-safely created "from parts", and we
hope to add those `try_` methods in the future.
[1]: https://lore.kernel.org/lkml/CAHk-=wh_sNLoz84AUUzuqXEsYH35u=8HV3vK-jbRbJ_B-JjGrg@mail.gmail.com/
Replace 'NULL' with 'null'
This replaces occurrences of "NULL" with "null" in docs, comments, and compiler error/lint messages. This is for the sake of consistency, as the lowercase "null" is already the dominant form in Rust. The all-caps NULL looks like the C macro (or SQL keyword), which seems out of place in a Rust context, given that NULL does not exist in the Rust language or standard library (instead having [`ptr::null()`](https://doc.rust-lang.org/stable/std/ptr/fn.null.html)).
i8 and u8::to_string() specialisation (far less asm).
Take 2. Around 1/6th of the assembly to without specialisation.
https://godbolt.org/z/bzz8Mq
(partially fixes#73533 )
Remove slice diagnostic item
...because it is unusally placed on an impl and is redundant with a lang item.
Depends on rust-lang/rust-clippy#7074 (next clippy sync). ~I expect clippy tests to fail in the meantime.~ Nope tests passed...
CC `@flip1995`
further split up const_fn feature flag
This continues the work on splitting up `const_fn` into separate feature flags:
* `const_fn_trait_bound` for `const fn` with trait bounds
* `const_fn_unsize` for unsizing coercions in `const fn` (looks like only `dyn` unsizing is still guarded here)
I don't know if there are even any things left that `const_fn` guards... at least libcore and liballoc do not need it any more.
`@oli-obk` are you currently able to do reviews?
Remove duplicated fn(Box<[T]>) -> Vec<T>
`<[T]>::into_vec()` does the same thing as `Vec::from::<Box<[T]>>()`, so they can be implemented in terms of each other. This was the previous implementation of `Vec::from()`, but was changed in #78461. I'm not sure what the rationale was for that change, but it seems preferable to maintain a single implementation.
Replace all `fmt.pad` with `debug_struct`
This replaces any occurrence of:
- `f.pad("X")` with `f.debug_struct("X").finish()`
- `f.pad("X { .. }")` with `f.debug_struct("X").finish_non_exhaustive()`
This is in line with existing formatting code such as
1255053067/library/std/src/sync/mpsc/mod.rs (L1470-L1475)
Improve code example for length comparison
Small fix/improvement: it's much safer to check that you're under the length of an array rather than chacking that you're equal to it. It's even more true in case you update the length of the array while iterating.
Add strong_count mutation methods to Rc
The corresponding methods were stabilized on `Arc` in #79285 (tracking: #71983). This patch implements and stabilizes identical methods on the `Rc` types as well.
Bump bootstrap to 1.52 beta
This includes the standard bump, but also a workaround for new cargo behavior around clearing out the doc directory when the rustdoc version changes.
BTree: move blocks around in node.rs
Without changing any names or implementation, reorder some members:
- Move down the ones defined long ago on the demised `struct Root`, to below the definition of their current host `struct NodeRef`.
- Move up some defined on `struct NodeRef` that are interspersed with those defined on `struct Handle`.
- Move up the `correct_…` methods squeezed between the two flavours of `push`.
- Move the unchecked static downcasts (`cast_to_…`) after the upcasts (`forget_`) and the (weirdly named) dynamic downcasts (`force`).
r? ````@Mark-Simulacrum````
BTree: no longer search arrays twice to check Ord
A possible addition to / partial replacement of #83147: no longer linearly search the upper bound of a range in the initial portion of the keys we already know are below the lower bound.
- Should be faster: fewer key comparisons at the cost of some instructions dealing with offsets
- Makes code a little more complicated.
- No longer detects ill-defined `Ord` implementations, but that wasn't a publicised feature, and was quite incomplete, and was only done in the `range` and `range_mut` methods.
r? `@Mark-Simulacrum`
Fix double-drop in `Vec::from_iter(vec.into_iter())` specialization when items drop during panic
This fixes the double-drop but it leaves a behavioral difference compared to the default implementation intact: In the default implementation the source and the destination vec are separate objects, so they get dropped separately. Here they share an allocation and the latter only exists as a pointer into the former. So if dropping the former panics then this fix will leak more items than the default implementation would. Is this acceptable or should the specialization also mimic the default implementation's drops-during-panic behavior?
Fixes#83618
`@rustbot` label T-libs-impl
alloc: Added `as_slice` method to `BinaryHeap` collection
I initially asked about whether it is useful addition on https://internals.rust-lang.org/t/should-i-add-as-slice-method-to-binaryheap/13816, and it seems there were no objections, so went ahead with this PR.
> There is [`BinaryHeap::into_vec`](https://doc.rust-lang.org/std/collections/struct.BinaryHeap.html#method.into_vec), but it consumes the value. I wonder if there is API design limitation that should be taken into account. Implementation-wise, the inner buffer is just a Vec, so it is trivial to expose as_slice from it.
Please, guide me through if I need to add tests or something else.
UPD: Tracking issue #83659
may not -> might not
may not -> might not
"may not" has two possible meanings:
1. A command: "You may not stay up past your bedtime."
2. A fact that's only sometimes true: "Some cities may not have bike lanes."
In some cases, the meaning is ambiguous: "Some cars may not have snow
tires." (do the cars *happen* to not have snow tires, or is it
physically impossible for them to have snow tires?)
This changes places where the standard library uses the "description of
fact" meaning to say "might not" instead.
This is just `std::vec` for now - if you think this is a good idea I can
convert the rest of the standard library.
Adjust documentation links for slice::make_ascii_*case
The documentation for the functions `slice::to_ascii_lowercase` and `slice::to_ascii_uppercase` contain the suggestion
> To lowercase the value in-place, use `make_ascii_lowercase`
however the link to the suggested method takes you to the page for `u8`, rather than the method of that name on the same page.
"may not" has two possible meanings:
1. A command: "You may not stay up past your bedtime."
2. A fact that's only sometimes true: "Some cities may not have bike lanes."
In some cases, the meaning is ambiguous: "Some cars may not have snow
tires." (do the cars *happen* to not have snow tires, or is it
physically impossible for them to have snow tires?)
This changes places where the standard library uses the "description of
fact" meaning to say "might not" instead.
This is just `std::vec` for now - if you think this is a good idea I can
convert the rest of the standard library.
Add function core::iter::zip
This makes it a little easier to `zip` iterators:
```rust
for (x, y) in zip(xs, ys) {}
// vs.
for (x, y) in xs.into_iter().zip(ys) {}
```
You can `zip(&mut xs, &ys)` for the conventional `iter_mut()` and
`iter()`, respectively. This can also support arbitrary nesting, where
it's easier to see the item layout than with arbitrary `zip` chains:
```rust
for ((x, y), z) in zip(zip(xs, ys), zs) {}
for (x, (y, z)) in zip(xs, zip(ys, zs)) {}
// vs.
for ((x, y), z) in xs.into_iter().zip(ys).zip(xz) {}
for (x, (y, z)) in xs.into_iter().zip((ys.into_iter().zip(xz)) {}
```
It may also format more nicely, especially when the first iterator is a
longer chain of methods -- for example:
```rust
iter::zip(
trait_ref.substs.types().skip(1),
impl_trait_ref.substs.types().skip(1),
)
// vs.
trait_ref
.substs
.types()
.skip(1)
.zip(impl_trait_ref.substs.types().skip(1))
```
This replaces the tuple-pair `IntoIterator` in #78204.
There is prior art for the utility of this in [`itertools::zip`].
[`itertools::zip`]: https://docs.rs/itertools/0.10.0/itertools/fn.zip.html
Add IEEE 754 compliant fmt/parse of -0, infinity, NaN
This pull request improves the Rust float formatting/parsing libraries to comply with IEEE 754's formatting expectations around certain special values, namely signed zero, the infinities, and NaN. It also adds IEEE 754 compliance tests that, while less stringent in certain places than many of the existing flt2dec/dec2flt capability tests, are intended to serve as the beginning of a roadmap to future compliance with the standard. Some relevant documentation is also adjusted with clarifying remarks.
This PR follows from discussion in https://github.com/rust-lang/rfcs/issues/1074, and closes#24623.
The most controversial change here is likely to be that -0 is now printed as -0. Allow me to explain: While there appears to be community support for an opt-in toggle of printing floats as if they exist in the naively expected domain of numbers, i.e. not the extended reals (where floats live), IEEE 754-2019 is clear that a float converted to a string should be capable of being transformed into the original floating point bit-pattern when it satisfies certain conditions (namely, when it is an actual numeric value i.e. not a NaN and the original and destination float width are the same). -0 is given special attention here as a value that should have its sign preserved. In addition, the vast majority of other programming languages not only output `-0` but output `-0.0` here.
While IEEE 754 offers a broad leeway in how to handle producing what it calls a "decimal character sequence", it is clear that the operations a language provides should be capable of round tripping, and it is confusing to advertise the f32 and f64 types as binary32 and binary64 yet have the most basic way of producing a string and then reading it back into a floating point number be non-conformant with the standard. Further, existing documentation suggested that e.g. -0 would be printed with -0 regardless of the presence of the `+` fmt character, but it prints "+0" instead if given such (which was what led to the opening of #24623).
There are other parsing and formatting issues for floating point numbers which prevent Rust from complying with the standard, as well as other well-documented challenges on the arithmetic level, but I hope that this can be the beginning of motion towards solving those challenges.
Make # pretty print format easier to discover
# Rationale:
I use (cargo cult?) three formats in rust: `{}`, debug `{:?}`, and pretty-print debug `{:#?}`. I discovered `{:#?}` in some blog post or guide when I started working in Rust. While `#` is documented I think it is hard to discover. So taking the good advice of ```@carols10cents``` I am trying to improve the docs with a PR
As a reminder "pretty print" means that where `{:?}` will print something like
```
foo: { b1: 1, b2: 2}
```
`{:#?}` will prints something like
```
foo {
b1: 1
b2: 3
}
```
# Changes
Add an example to `fmt` to try and make it easier to discover `#`
This seems to have been omitted from the beginning when this feature
was first introduced in 86bf96291d.
Most users won't need to name this type which is probably why this
wasn't noticed in the meantime.
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
"semantic equivalence" is too strong a phrasing here, which is why
actually explaining what kind of circumstances might produce a -0
was chosen instead.
Fix invalid slice access in String::retain
As noted in #78499, the previous fix was technically still unsound because it accessed elements of a slice outside its bounds (even though they were still inside the same allocation). This PR addresses that concern by switching to a dropguard approach.
This allows the optimizer to turn certain iterator pipelines such as
```rust
let vec = vec![0usize; 100];
vec.into_iter().map(|e| e as isize).collect::<Vec<_>>()
```
into a noop.
The optimization only applies when iterator sources are `T: Copy`
since `impl TrustedRandomAccess for IntoIter<T>`.
No such requirement applies to the output type (`Iterator::Item`).
Fix overflowing length in Vec<ZST> to VecDeque
`Vec` can hold up to `usize::MAX` ZST items, but `VecDeque` has a lower
limit to keep its raw capacity as a power of two, so we should check
that in `From<Vec<T>> for VecDeque<T>`. We can also simplify the
capacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
```
thread 'collections::vec_deque::tests::test_from_vec_zst_overflow' panicked at 'assertion failed: `(left == right)`
left: `0`,
right: `9223372036854775808`', library/alloc/src/collections/vec_deque/tests.rs:474:5
note: panic did not contain expected string
panic message: `"assertion failed: `(left == right)`\n left: `0`,\n right: `9223372036854775808`"`,
expected substring: `"capacity overflow"`
```
That was a result of `len()` using a mask `& (size - 1)` with the
improper length. Now we do get a "capacity overflow" panic as soon as
that `VecDeque::from(vec)` is attempted.
Fixes#80167.
Implement String::remove_matches
Closes#50206.
I lifted the function help from `@frewsxcv's` original PR (#50015), hope they don't mind.
I'm also wondering whether it would be useful for `remove_matches` to collect up the removed substrings into a `Vec` and return them, right now they're just overwritten by the copy and lost.
Add more links between hash and btree collections
- Link from `core::hash` to `HashMap` and `HashSet`
- Link from HashMap and HashSet to the module-level documentation on
when to use the collection
- Link from several collections to Wikipedia articles on the general
concept
See also https://github.com/rust-lang/rust/pull/81989#issuecomment-783920840.
Vec::dedup_by optimization
Now `Vec::dedup_by` drops items in-place as it goes through them.
From my benchmarks, it is around 10% faster when T is small, with no major regression when otherwise.
I used `ptr::copy` instead of conditional `ptr::copy_nonoverlapping`, because the latter had some weird performance issues on my ryzen laptop (it was 50% slower on it than on intel/sandybridge laptop)
It would be good if someone was able to reproduce these results.
`Vec` can hold up to `usize::MAX` ZST items, but `VecDeque` has a lower
limit to keep its raw capacity as a power of two, so we should check
that in `From<Vec<T>> for VecDeque<T>`. We can also simplify the
capacity check for the remaining non-ZST case.
Before this fix, the new test would fail on the length:
```
thread 'collections::vec_deque::tests::test_from_vec_zst_overflow' panicked at 'assertion failed: `(left == right)`
left: `0`,
right: `9223372036854775808`', library/alloc/src/collections/vec_deque/tests.rs:474:5
note: panic did not contain expected string
panic message: `"assertion failed: `(left == right)`\n left: `0`,\n right: `9223372036854775808`"`,
expected substring: `"capacity overflow"`
```
That was a result of `len()` using a mask `& (size - 1)` with the
improper length. Now we do get a "capacity overflow" panic as soon as
that `VecDeque::from(vec)` is attempted.
convert slice doc link to intra-doc links
Continuing where #80189 stopped, with `core::slice`.
I had an issue with two dead links in my doc when implementing `Deref<Target = [T]>` for one of my type. This means that [`binary_search_by_key`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.binary_search_by_key) was available, but not [`sort_by_key`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.sort_by_key) even though it was linked in it's doc (same issue with [`as_ptr`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_ptr) and [`as_mut_pbr`](https://doc.rust-lang.org/nightly/std/primitive.slice.html#method.as_mut_ptr)). It becomes available if I implement `DerefMut`, as it needs an `&mut self`.
<details>
<summary>Code that will have dead links in its doc</summary>
```rust
pub struct A;
pub struct B;
impl std::ops::Deref for B{
type Target = [A];
fn deref(&self) -> &Self::Target {
&A
}
}
```
</details>
I removed the link to `sort_by_key` from `binary_search_by_key` doc as I didn't find a nice way to have a live link:
- `binary_search_by_key` is in `core`
- `sort_by_key` is in `alloc`
- intra-doc link `slice::sort_by_key` doesn't work, as `alloc` is not available when `core` is being build (the warning can't be ignored: ```error[E0710]: an unknown tool name found in scoped lint: `rustdoc::broken_intra_doc_links` ```)
- keeping the link as an anchor `#method.sort_by_key` meant a dead link
- an absolute link would work but doesn't feel right...
Stabilize `unsafe_op_in_unsafe_fn` lint
This makes it possible to override the level of the `unsafe_op_in_unsafe_fn`, as proposed in https://github.com/rust-lang/rust/issues/71668#issuecomment-729770896.
Tracking issue: #71668
r? ```@nikomatsakis``` cc ```@SimonSapin``` ```@RalfJung```
# Stabilization report
This is a stabilization report for `#![feature(unsafe_block_in_unsafe_fn)]`.
## Summary
Currently, the body of unsafe functions is an unsafe block, i.e. you can perform unsafe operations inside.
The `unsafe_op_in_unsafe_fn` lint, stabilized here, can be used to change this behavior, so performing unsafe operations in unsafe functions requires an unsafe block.
For now, the lint is allow-by-default, which means that this PR does not change anything without overriding the lint level.
For more information, see [RFC 2585](https://github.com/rust-lang/rfcs/blob/master/text/2585-unsafe-block-in-unsafe-fn.md)
### Example
```rust
// An `unsafe fn` for demonstration purposes.
// Calling this is an unsafe operation.
unsafe fn unsf() {}
// #[allow(unsafe_op_in_unsafe_fn)] by default,
// the behavior of `unsafe fn` is unchanged
unsafe fn allowed() {
// Here, no `unsafe` block is needed to
// perform unsafe operations...
unsf();
// ...and any `unsafe` block is considered
// unused and is warned on by the compiler.
unsafe {
unsf();
}
}
#[warn(unsafe_op_in_unsafe_fn)]
unsafe fn warned() {
// Removing this `unsafe` block will
// cause the compiler to emit a warning.
// (Also, no "unused unsafe" warning will be emitted here.)
unsafe {
unsf();
}
}
#[deny(unsafe_op_in_unsafe_fn)]
unsafe fn denied() {
// Removing this `unsafe` block will
// cause a compilation error.
// (Also, no "unused unsafe" warning will be emitted here.)
unsafe {
unsf();
}
}
```
Improve sift_down performance in BinaryHeap
Replacing `child < end - 1` with `child <= end.saturating_sub(2)` in `BinaryHeap::sift_down_range` (surprisingly) results in a significant speedup of `BinaryHeap::into_sorted_vec`. The same substitution can be done for `BinaryHeap::sift_down_to_bottom`, which causes a slight but probably statistically insignificant speedup for `BinaryHeap::pop`. It's interesting that benchmarks aside from `bench_into_sorted_vec` are barely affected, even those that do use `sift_down_*` methods internally.
| Benchmark | Before (ns/iter) | After (ns/iter) | Speedup |
|--------------------------|------------------|-----------------|---------|
| bench_find_smallest_1000<sup>1</sup> | 392,617 | 385,200 | 1.02 |
| bench_from_vec<sup>1</sup> | 506,016 | 504,444 | 1.00 |
| bench_into_sorted_vec<sup>1</sup> | 476,869 | 384,458 | 1.24 |
| bench_peek_mut_deref_mut<sup>3</sup> | 518,753 | 519,792 | 1.00 |
| bench_pop<sup>2</sup> | 446,718 | 444,409 | 1.01 |
| bench_push<sup>3</sup> | 772,481 | 770,208 | 1.00 |
<sup>1</sup>: internally calls `sift_down_range`
<sup>2</sup>: internally calls `sift_down_to_bottom`
<sup>3</sup>: should not be affected
Add {BTreeMap,HashMap}::try_insert
`{BTreeMap,HashMap}::insert(key, new_val)` returns `Some(old_val)` if the key was already in the map. It's often useful to assert no duplicate values are inserted.
We experimented with `map.insert(key, val).unwrap_none()` (https://github.com/rust-lang/rust/issues/62633), but decided that that's not the kind of method we'd like to have on `Option`s.
`insert` always succeeds because it replaces the old value if it exists. One could argue that `insert()` is never the right method for panicking on duplicates, since already handles that case by replacing the value, only allowing you to panic after that already happened.
This PR adds a `try_insert` method that instead returns a `Result::Err` when the key already exists. This error contains both the `OccupiedEntry` and the value that was supposed to be inserted. This means that unwrapping that result gives more context:
```rust
map.insert(10, "world").unwrap_none();
// thread 'main' panicked at 'called `Option::unwrap_none()` on a `Some` value: "hello"', src/main.rs:8:29
```
```rust
map.try_insert(10, "world").unwrap();
// thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value:
// OccupiedError { key: 10, old_value: "hello", new_value: "world" }', src/main.rs:6:33
```
It also allows handling the failure in any other way, as you have full access to the `OccupiedEntry` and the value.
`try_insert` returns a reference to the value in case of success, making it an alternative to `.entry(key).or_insert(value)`.
r? ```@Amanieu```
Fixes https://github.com/rust-lang/rfcs/issues/3092
Implement NOOP_METHOD_CALL lint
Implements the beginnings of https://github.com/rust-lang/lang-team/issues/67 - a lint for detecting noop method calls (e.g, calling `<&T as Clone>::clone()` when `T: !Clone`).
This PR does not fully realize the vision and has a few limitations that need to be addressed either before merging or in subsequent PRs:
* [ ] No UFCS support
* [ ] The warning message is pretty plain
* [ ] Doesn't work for `ToOwned`
The implementation uses [`Instance::resolve`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/instance/struct.Instance.html#method.resolve) which is normally later in the compiler. It seems that there are some invariants that this function relies on that we try our best to respect. For instance, it expects substitutions to have happened, which haven't yet performed, but we check first for `needs_subst` to ensure we're dealing with a monomorphic type.
Thank you to ```@davidtwco,``` ```@Aaron1011,``` and ```@wesleywiser``` for helping me at various points through out this PR ❤️.
Previously vec's len was updated only after full copy, making the method
leak if T::clone panic!s.
This commit makes `Vec::extend_from_within` (or, more accurately, it's
`T: Clone` specialization) update vec's len on every iteration, fixing
the issue.
`T: Copy` specialization was not affected by the issue b/c it doesn't
call user specified code (as, e.g. `T::clone`), and instead calls
`ptr::copy_nonoverlapping`.
Revert `Vec::spare_capacity_mut` impl to prevent pointers invalidation
The implementation was changed in #79015.
Later it was [pointed out](https://github.com/rust-lang/rust/issues/81944#issuecomment-782849785) that the implementation invalidates pointers to the buffer (initialized elements) by creating a unique reference to the buffer. This PR reverts the implementation.
r? ```@RalfJung```
Turn may_have_side_effect into an associated constant
The `may_have_side_effect` is an implementation detail of `TrustedRandomAccess`
trait. It describes if obtaining an iterator element may have side effects. It
is currently implemented as an associated function.
Turn `may_have_side_effect` into an associated constant. This makes the
value immediately available to the optimizer.
Convert primitives in the standard library to intra-doc links
Blocked on https://github.com/rust-lang/rust/pull/80181. I forgot that this needs to wait for the beta bump so the standard library can be documented with `doc --stage 0`.
Notably I didn't convert `core::slice` because it's like 50 links and I got scared 😨
BTree: no longer define impossible casts
Casts to leaf to internal only make sense when the original has a chance of being the thing it's cast to.
r? `@Mark-Simulacrum`
BTreeMap: split up range_search into two stages
`range_search` expects the caller to pass the same root twice and starts searching a node for both bounds of a range. It's not very clear that in the early iterations, it searches twice in the same node. This PR splits that search up in an initial `find_leaf_edges_spanning_range` that postpones aliasing until the last second, and a second phase for continuing the search for the range in the each subtree independently (`find_lower_bound_edge` & `find_upper_bound_edge`), which greatly helps for use in #81075. It also moves those functions over to the search module.
r? `@Mark-Simulacrum`
Almost all safety comments are of the form `// SAFETY:`,
so normalize the rest and fix a few of them that should
have been a `/// # Safety` section instead.
Furthermore, make `tidy` only allow the uppercase form. While
currently `tidy` only checks `core`, it is a good idea to prevent
`core` from drifting to non-uppercase comments, so that later
we can start checking `alloc` etc. too.
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Improve non_fmt_panic lint.
This change:
- fixes the span used by this lint in the case the panic argument is a single macro expansion (e.g. `panic!(a!())`);
- adds a suggestion for `panic!(format!(..))` to remove `format!()` instead of adding `"{}", ` or using `panic_any` like it does now; and
- fixes the incorrect suggestion to replace `panic![123]` by `panic_any(123]`.
Fixes#82109.
Fixes#82110.
Fixes#82111.
Example output:
```
warning: panic message is not a string literal
--> src/main.rs:8:12
|
8 | panic!(format!("error: {}", "oh no"));
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `#[warn(non_fmt_panic)]` on by default
= note: this is no longer accepted in Rust 2021
= note: the panic!() macro supports formatting, so there's no need for the format!() macro here
help: remove the `format!(..)` macro call
|
8 | panic!("error: {}", "oh no");
| -- --
```
r? `@estebank`
Update the bootstrap compiler
This updates the bootstrap compiler, notably leaving out a change to enable semicolon in macro expressions lint, because stdarch still depends on the old behavior.
- Link from `core::hash` to `HashMap` and `HashSet`
- Link from HashMap and HashSet to the module-level documentation on
when to use the collection
- Link from several collections to Wikipedia articles on the general
concept
add diagnostic items for OsString/PathBuf/Owned as well as to_vec on slice
This is adding diagnostic items to be used by rust-lang/rust-clippy#6730, but my understanding is the clippy-side change does need to be done over there since I am adding a new clippy feature.
Add diagnostic items to the following types:
OsString (os_string_type)
PathBuf (path_buf_type)
Owned (to_owned_trait)
As well as the to_vec method on slice/[T]
Improve design of `assert_len`
It was discussed in the [tracking issue](https://github.com/rust-lang/rust/issues/76393#issuecomment-761765448) that `assert_len`'s name and usage are confusing. This PR improves them based on a suggestion by ``@scottmcm`` in that issue.
I also improved the documentation to make it clearer when you might want to use this method.
Old example:
```rust
let range = range.assert_len(slice.len());
```
New example:
```rust
let range = range.ensure_subset_of(..slice.len());
```
Fixes#81157
BTree: move more shared iterator code into navigate.rs
The functions in navigate.rs only exist to support iterators, and these look easier on my eyes if there is a shared `struct` with the recurring pair of handles.
r? `@Mark-Simulacrum`
BTreeMap: gather and decompose reusable tree fixing functions
This is kind of pushing it as a standalone refactor, probably only useful for #81075 (or similar).
r? `@Mark-Simulacrum`
Because child > 0, the two statements are equivalent, but using
saturating_sub and <= yields in faster code. This is most notable in the
binary_heap::bench_into_sorted_vec benchmark, which shows a speedup of
1.26x, which uses sift_down_range internally. The speedup of pop (that
uses sift_down_to_bottom internally) is much less significant as the
sifting method is not called in a loop.
Document BinaryHeap unsafe functions
`BinaryHeap` contains some private safe functions but that are actually unsafe to call. This PR marks them `unsafe` and documents all the `unsafe` function calls inside them.
While doing this I might also have found a bug: some "SAFETY" comments in `sift_down_range` and `sift_down_to_bottom` are valid only if you assume that `child` doesn't overflow. However it may overflow if `end > isize::MAX` which can be true for ZSTs (but I think only for them). I guess the easiest fix would be to skip any sifting if `mem::size_of::<T> == 0`.
Probably conflicts with #81127 but solving the eventual merge conflict should be pretty easy.
BTree: share panicky test code & test panic during clear, clone
Bases almost all tests of panic on the same, richer definition, and extends it to cloning to test panic during clone.
r? ```@Mark-Simulacrum```
The `may_have_side_effect` is an implementation detail of `TrustedRandomAccess`
trait. It describes if obtaining an iterator element may have side effects. It
is currently implemented as an associated function.
Turn `may_have_side_effect` into an associated constant. This makes the
value immediately available to the optimizer.
Add diagnostic items to the following types:
OsString (os_string_type)
PathBuf (path_buf_type)
Owned (to_owned_trait)
As well as the to_vec method on slice/[T]
BTree: remove outdated traces of coercions
The introduction of `marker::ValMut` (#75200) meant iterators no longer see mutable keys but their code still pretends it does. And settle on the majority style `Some(unsafe {…})` over `unsafe { Some(…) }`.
r? `@Mark-Simulacrum`
Initialize BTree nodes directly in the heap
We can avoid any stack-local nodes entirely by using `Box::new_uninit`, and since the nodes are mostly `MaybeUninit` fields, we only need a couple of actual writes before `assume_init`. This should help with the stack overflows in #81444, and may also improve performance in general.
r? `@Mark-Simulacrum`
cc `@ssomers`
Add docs for shared_from_slice From impls
The advantage of making these docs is mostly in pointing out that these
functions all make new allocations and copy/clone/move the source into them.
These docs are on the function, and not the `impl` block, to avoid showing
the "[+] show undocumented items" button.
CC #51430
Fix doc test for Vec::retain(), now passes clippy::eval_order_dependence
Doc test for Vec::retain() works correctly but is flagged by clippy::eval_order_dependence. Fix avoids the issue by using an iterator instead of an index.
The advantage of making these docs is mostly in pointing out that these
functions all make new allocations and copy/clone/move the source into them.
These docs are on the function, and not the `impl` block, to avoid showing
the "[+] show undocumented items" button.
CC #51430
BTreeMap: disentangle Drop implementation from IntoIter
No longer require every `BTreeMap` to dig up its last leaf edge before dying. This speeds up the `clone_` benchmarks by 25% for normal keys and values (far less for huge values).
r? `@Mark-Simulacrum`
Optimize Vec::retain
Use `copy_non_overlapping` instead of `swap` to reduce memory writes, like what we've done in #44355 and `String::retain`.
#48065 already tried to do this optimization but it is reverted in #67300 due to bad codegen of `DrainFilter::drop`.
This PR re-implement the drop-then-move approach. I did a [benchmark](https://gist.github.com/oxalica/3360eec9376f22533fcecff02798b698) on small-no-drop, small-need-drop, large-no-drop elements with different predicate functions. It turns out that the new implementation is >20% faster in average for almost all cases. Only 2/24 cases are slower by 3% and 5%. See the link above for more detail.
I think regression in may-panic cases is due to drop-guard preventing some optimization. If it's permitted to leak elements when predicate function of element's `drop` panic, the new implementation should be almost always faster than current one.
I'm not sure if we should leak on panic, since there is indeed an issue (#52267) complains about it before.
Make Vec::split_at_spare_mut public
This PR introduces a new method to the public API, under
`vec_split_at_spare` feature gate:
```rust
impl<T, A: Allocator> impl Vec<T, A> {
pub fn split_at_spare_mut(&mut self) -> (&mut [T], &mut [MaybeUninit<T>]);
}
```
The method returns 2 slices, one slice references the content of the vector,
and the other references the remaining spare capacity.
The method was previously implemented while adding `Vec::extend_from_within` in #79015,
and used to implement `Vec::spare_capacity_mut` (as the later is just a
subset of former one).
See also previous [discussion in `Vec::spare_capacity_mut` tracking issue](https://github.com/rust-lang/rust/issues/75017#issuecomment-770381335).
## Unresolved questions
- [ ] Should we consider changing the name? `split_at_spare_mut` doesn't seem like an intuitive name
- [ ] Should we deprecate `Vec::spare_capacity_mut`? Any usecase of `Vec::spare_capacity_mut` can be replaced with `Vec::split_at_spare_mut` (but not vise-versa)
r? `@KodrAus`
Add `Box::into_inner`.
This adds a `Box::into_inner` method to the `Box` type. <del>I actually suggest deprecating the compiler magic of `*b` if this gets stablized in the future.</del>
r? `@m-ou-se`
Rollup of 11 pull requests
Successful merges:
- #72209 (Add checking for no_mangle to unsafe_code lint)
- #80732 (Allow Trait inheritance with cycles on associated types take 2)
- #81697 (Add "every" as a doc alias for "all".)
- #81826 (Prefer match over combinators to make some Box methods inlineable)
- #81834 (Resolve typedef in HashMap lldb pretty-printer only if possible)
- #81841 ([rustbuild] Output rustdoc-json-types docs )
- #81849 (Expand the docs for ops::ControlFlow a bit)
- #81876 (parser: Fix panic in 'const impl' recovery)
- #81882 (⬆️ rust-analyzer)
- #81888 (Fix pretty printer macro_rules with semicolon.)
- #81896 (Remove outdated comment in windows' mutex.rs)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Prefer match over combinators to make some Box methods inlineable
Hopefully this patch would make two snippets generated identical code: <https://rust.godbolt.org/z/fjrj4E>.
