Add `std:#️⃣:{DefaultHasher, RandomState}` exports (needs FCP)
This implements rust-lang/libs-team#267 to move the libstd hasher types to `std::hash` where they belong, instead of `std::collections::hash_map`.
<details><summary>The below no longer applies, but is kept for clarity.</summary>
This is a small refactor for #27242, which moves the definitions of `RandomState` and `DefaultHasher` into `std::hash`, but in a way that won't be noticed in the public API.
I've opened rust-lang/libs-team#267 as a formal ACP to move these directly into the root of `std::hash`, but for now, they're at least separated out from the collections code in a way that will make moving that around easier.
I decided to simply copy the rustdoc for `std::hash` from `core::hash` since I think it would be ideal for the two to diverge longer-term, especially if the ACP is accepted. However, I would be willing to factor them out into a common markdown document if that's preferred.
</details>
Clarify UB in `get_unchecked(_mut)`
Inspired by #116915, it was unclear to me what exactly "out-of-bounds index" means in `get_unchecked`.
One could [potentially](https://rust.godbolt.org/z/hxM764orW) interpret it that `get_unchecked` is just another way to write `offset`, but I think `get_unchecked(len)` is supposed to be UB even though `.offet(len)` is well-defined (as is `.get_unchecked(..len)`), so write that more directly in the docs.
**libs-api folks**: Can you confirm whether this is what you expect this to mean? And is the situation any different for `<*const [T]>::get_unchecked`?
patterns: reject raw pointers that are not just integers
Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.
This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See [here](https://github.com/rust-lang/rust/pull/116930#issuecomment-1784654073) for some more explanation and context.
Also fixes https://github.com/rust-lang/rust/issues/116929.
Cc `@oli-obk` `@lcnr`
Documentation cleanup for core::error::Request.
This part of the documentation currently render like this:
The new version renders like this:
Fixes:
* Add missing closing back tick.
* Remove spurious double back ticks.
* Add missing newline to render bullet point correctly.
* Fix grammar "there are methods calledrequest_ref and request_value are available" -> "there are methods calledrequest_ref and request_value".
* Change "methods" to "functions", which seems more appropriate for free functions.
document that the null pointer has the 0 address
Fixes https://github.com/rust-lang/rust/issues/116895
Will need t-lang FCP, but I think this is fairly uncontroversial -- there's probably already tons of code out there that relies on this.
Override `Waker::clone_from` to avoid cloning `Waker`s unnecessarily
This would be very useful for futures — I think it’s pretty much always what they want to do instead of `*waker = cx.waker().clone()`.
Tracking issue: https://github.com/rust-lang/rust/issues/98287
r? rust-lang/libs-api `@rustbot` label +T-libs-api -T-libs
Avoid unnecessary comparison in partition_equal
The branchy Hoare partition `partition_equal` as part of `slice::sort_unstable` has a bug that makes it perform a comparison of the last element twice.
Measuring inputs with a Zipfian distribution with characterizing exponent s == 1.0, yields a ~0.05% reduction in the total number of comparisons performed.
Add diagnostic items for a few of core's builtin macros
Specifically, `env`, `option_env`, and `include`. There are a number of reasons why people might want to look at these in lints (For example, to ensure that things behave consistently, detect things that might make builds less reproducible, etc).
Concretely, in PL/Rust (well, `plrustc`) we have lints that forbid these (which I'd like to [add to clippy as restriction lints](https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/Landing.20a.20flotilla.20of.20lints.3F) eventually), and `dylint` also has [lints that look for `env!`/`option_env!`](109a07e9f2/examples/general/env_cargo_path/src/lib.rs) (although perhaps not `include`), which would benefit from this.
My experience is that it's pretty annoying to (robustly) check uses of builtin macros without these IME, although that's perhaps just my own fault (e.g. I could be doing it wrong).
At `@Nilstrieb's` suggestion, I've added a comment that explains why these are here, even though they are not used in the compiler. This is mostly to discourage removal, although it's not a big deal if it happens (I'm certainly not suggesting the presence of these be in any way stable).
---
In theory this is a library PR (in that it's in library/core), but I'm going to roll compiler because the existence of this or not is much more likely something they care about rather than libs. Hopefully nobody objects to this.
r? compiler
Stabilize `const_maybe_uninit_zeroed` and `const_mem_zeroed`
Make `MaybeUninit::zeroed` and `mem::zeroed` const stable. Newly stable API:
```rust
// core::mem
pub const unsafe fn zeroed<T>() ->;
impl<T> MaybeUninit<T> {
pub const fn zeroed() -> MaybeUninit<T>;
}
```
This relies on features based around `const_mut_refs`. Per `@RalfJung,` this should be OK since we do not leak any `&mut` to the user.
For this to be possible, intrinsics `assert_zero_valid` and `assert_mem_uninitialized_valid` were made const stable.
Tracking issue: #91850
Zulip discussion: https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/.60const_mut_refs.60.20dependents
r? libs-api
`@rustbot` label -T-libs +T-libs-api +A-const-eval
cc `@RalfJung` `@oli-obk` `@rust-lang/wg-const-eval`
Deref docs: expand and remove "smart pointer" qualifier
**Ready for review**
~~This is an unpolished draft to be sanity-checked~~
Fixes#91004
~~Comments on substance and content of this are welcome. This is deliberately unpolished until ready to review so please try to stay focused on the big-picture.~~
~~Once this has been sanity checked, I will similarly update `DerefMut` and polish for review.~~
Make `core::mem::zeroed` const stable. Newly stable API:
// core::mem
pub const unsafe fn zeroed<T>() -> T;
This is stabilized with `const_maybe_uninit_zeroed` since it is a simple
wrapper.
In order to make this possible, intrinsics `assert_zero_valid` was made
const stable under `const_assert_type2`.
`assert_mem_uninitialized_valid` was also made const stable since it is
under the same gate.
Make `MaybeUninit::zeroed` const stable. Newly stable API:
// core::mem
impl<T> MaybeUninit<T> {
pub const fn zeroed() -> MaybeUninit<T>;
}
Use of `const_mut_refs` should be acceptable since we do not leak the
mutability.
Tracking issue: #91850
Re-draft Deref docs
Make general advice more explicit and note the difference between
generic and specific implementations.
Re-draft DerefMut docs in-line with Deref
Fix Deref docs typos
Fix broken links
Clarify advice for specific-over-generic impls
Add comment addressing Issue #73682
x fmt
Copy faillibility warning to DerefMut
Remove support for compiler plugins.
They've been deprecated for four years.
This commit includes the following changes.
- It eliminates the `rustc_plugin_impl` crate.
- It changes the language used for lints in `compiler/rustc_driver_impl/src/lib.rs` and `compiler/rustc_lint/src/context.rs`. External lints are now called "loaded" lints, rather than "plugins" to avoid confusion with the old plugins. This only has a tiny effect on the output of `-W help`.
- E0457 and E0498 are no longer used.
- E0463 is narrowed, now only relating to unfound crates, not plugins.
- The `plugin` feature was moved from "active" to "removed".
- It removes the entire plugins chapter from the unstable book.
- It removes quite a few tests, mostly all of those in `tests/ui-fulldeps/plugin/`.
Closes#29597.
r? `@ghost`
They've been deprecated for four years.
This commit includes the following changes.
- It eliminates the `rustc_plugin_impl` crate.
- It changes the language used for lints in
`compiler/rustc_driver_impl/src/lib.rs` and
`compiler/rustc_lint/src/context.rs`. External lints are now called
"loaded" lints, rather than "plugins" to avoid confusion with the old
plugins. This only has a tiny effect on the output of `-W help`.
- E0457 and E0498 are no longer used.
- E0463 is narrowed, now only relating to unfound crates, not plugins.
- The `plugin` feature was moved from "active" to "removed".
- It removes the entire plugins chapter from the unstable book.
- It removes quite a few tests, mostly all of those in
`tests/ui-fulldeps/plugin/`.
Closes#29597.
Guarantee representation of None in NPO
This allows users to soundly transmute zeroes into `Option` types subject to the null pointer optimization (NPO). It unblocks https://github.com/google/zerocopy/issues/293.
Add track_caller to transmute_copy
Currently if `size_of::<Src>() < size_of::<Dst>()` you will see the following error:
```rust
thread 'test' panicked at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/mem/mod.rs:1056:5:
cannot transmute_copy if Dst is larger than Src
```
This fixes it so it will show the invocation location
Clarify `Unsize` documentation
The documentation erroneously says that:
```rust
/// - Types implementing a trait `Trait` also implement `Unsize<dyn Trait>`.
/// - Structs `Foo<..., T, ...>` implement `Unsize<Foo<..., U, ...>>` if all of these conditions
/// are met:
/// - `T: Unsize<U>`.
/// - Only the last field of `Foo` has a type involving `T`.
/// - `Bar<T>: Unsize<Bar<U>>`, where `Bar<T>` stands for the actual type of that last field.
```
Specifically, `T: Unsize<U>` is not required to hold -- only the final field must implement `FinalField<T>: Unsize<FinalField<U>>`. This can be demonstrated by the test I added.
---
Second commit fleshes out the documentation a lot more.
Support enum variants in offset_of!
This MR implements support for navigating through enum variants in `offset_of!`, placing the enum variant name in the second argument to `offset_of!`. The RFC placed it in the first argument, but I think it interacts better with nested field access in the second, as you can then write things like
```rust
offset_of!(Type, field.Variant.field)
```
Alternatively, a syntactic distinction could be made between variants and fields (e.g. `field::Variant.field`) but I'm not convinced this would be helpful.
[RFC 3308 # Enum Support](https://rust-lang.github.io/rfcs/3308-offset_of.html#enum-support-offset_ofsomeenumstructvariant-field_on_variant)
Tracking Issue #106655.
Clean up unchecked_math, separate out unchecked_shifts
Tracking issue: #85122
Changes:
1. Remove `const_inherent_unchecked_arith` flag and make const-stability flags the same as the method feature flags. Given the number of other unsafe const fns already stabilised, it makes sense to just stabilise these in const context when they're stabilised.
2. Move `unchecked_shl` and `unchecked_shr` into a separate `unchecked_shifts` flag, since the semantics for them are unclear and they'll likely be stabilised separately as a result.
3. Add an `unchecked_neg` method exclusively to signed integers, under the `unchecked_neg` flag. This is because it's a new API and probably needs some time to marinate before it's stabilised, and while it *would* make sense to have a similar version for unsigned integers since `checked_neg` also exists for those there is absolutely no case where that would be a good idea, IMQHO.
The longer-term goal here is to prepare the `unchecked_math` methods for an FCP and stabilisation since they've existed for a while, their semantics are clear, and people seem in favour of stabilising them.
