Add `#![feature(const_fn_floating_point_arithmetic)]`
cc #76618
This is a template for splitting up `const_fn` into granular feature gates. I think this will make it easier, both for us and for users, to track stabilization of each individual feature. We don't *have* to do this, however. We could also keep stabilizing things out from under `const_fn`.
cc @rust-lang/wg-const-eval
r? @oli-obk
Explicitly document the size guarantees that Option makes.
Triggered by a discussion on wg-unsafe-code-guidelines about which layouts of `Option<T>` one can guarantee are optimised to a single pointer.
CC @RalfJung
It's possible for method resolution to pick this method over a lower
priority stable method, causing compilation errors. Since this method
is permanently unstable, give it a name that is very unlikely to be used
in user code.
Make [].as_[mut_]ptr_range() (unstably) const.
Gated behind `const_ptr_offset`, as suggested by https://github.com/rust-lang/rust/issues/65807#issuecomment-697229404
This also marks `[].as_mut_ptr()` as const, because it's used by `as_mut_ptr_range`. I gated it behind the same feature, because I figured it's not worth adding a separate tracking issue for const `as_mut_ptr`.
Use `Self` in docs when possible
Fixes#76542.
I used `rg '\s*//[!/]\s+fn [\w_]+\(&?self, ' .` in `library/` to find instances, I found some with that and some by manually checking.
@rustbot modify labels: C-enhancement T-doc
add array::from_ref
mirrors the methods in `std::slice` with the same name.
I guess this method previously didn't exist as there was close to no reason to create an array of size `1`.
This will change due to const generics in the near future.
revert const_type_id stabilization
This reverts #72488, which is currently on beta and scheduled to stabilize in `1.47.0`, based on https://github.com/rust-lang/rust/pull/75923#issuecomment-696676511
It turns out we might not be quite ready to stabilize `TypeId` in const contexts before having a chance to rework its internals. Since `TypeId` is a bit of an oddity we want to be careful about how those internals are currently being relied on while making changes. That will be easier to do without having to also consider compile-time contexts.
r? `@eddyb`
Add #[track_caller] to more panicking Cell functions
Continuation of #74526
Adds the #[track_caller] attribute to almost all panicking Cell
functions. The ones that borrow two Cells in their function
body are spared, because the panic location helps pinpoint
which of the two borrows failed. You'd need to have
full debuginfo and backtraces enabled together with column
info in order to be able to discern the cases.
Column info in debuginfo is only available on non-Windows platforms.
Add cfg(target_has_atomic_equal_alignment) and use it for Atomic::from_mut.
Fixes some platform-specific problems with #74532 by using the actual alignment of the types instead of hardcoding a few `target_arch`s.
r? @RalfJung
Continuation of #74526
Adds the #[track_caller] attribute to almost all panicking Cell
functions. The ones that borrow two Cells in their function
body are spared, because the panic location helps pinpoint
which of the two borrows failed. You'd need to have
full debuginfo and backtraces enabled together with column
info in order to be able to discern the cases.
Column info is only available on non-Windows platforms.
Make some methods of `Pin` unstable const
Make the following methods unstable const under the `const_pin` feature:
- `new`
- `new_unchecked`
- `into_inner`
- `into_inner_unchecked`
- `get_ref`
- `into_ref`
- `get_mut`
- `get_unchecked_mut`
Of these, `into_inner` and `into_inner_unchecked` require the unstable `const_precise_live_drops`.
Also adds tests for these methods in a const context.
Tracking issue: #76654
r? @ecstatic-morse
Don't recommend ManuallyDrop to customize drop order
See
https://internals.rust-lang.org/t/need-for-controlling-drop-order-of-fields/12914/21
for the discussion.
TL;DR: ManuallyDrop is unsafe and footguny, but you can just ask the compiler to do all the work for you by re-ordering declarations.
Specifically, the original example from the docs is much better written as
```rust
struct Peach;
struct Banana;
struct Melon;
struct FruitBox {
melon: Melon,
// XXX: mind the relative drop order of the fields below
peach: Peach,
banana: Banana,
}
```
Revert adding Atomic::from_mut.
This reverts #74532, which made too many assumptions about platforms, breaking some things.
Will need to be added later with a better way of gating on proper alignment, without hardcoding cfg(target_arch)s.
---
To be merged if fixing from_mut (#76965) takes too long.
r? @ghost
Add non-`unsafe` `.get_mut()` for `Unsafecell`
- Tracking issue: https://github.com/rust-lang/rust/issues/76943
As discussed in: https://internals.rust-lang.org/t/add-non-unsafe-get-mut-for-unsafecell/12407
- ### [Rendered documentation](https://modest-dubinsky-1f9f47.netlify.app/core/cell/struct.unsafecell)
This PR tries to move the sound `&mut UnsafeCell<T> -> &mut T` projection that all the "downstream" constructions were already relying on, up to the root abstraction, where it rightfully belongs, and officially blessing it.
- this **helps reduce the amount of `unsafe` snippets out there** (_c.f._, the second commit of this PR: 09503fd1b3)
The fact that this getter is now expose for `UnsafeCell<T>` itself, will also help convey the idea that **`UnsafeCell` is not magical _w.r.t._ `&mut` accesses**, contrary to what some people incorrectly think.
- Even the standard library itself at some point had such a confusion, _c.f._ this comment where there is a mention of multi-threaded (and thus _shared_) access despite dealing with exclusive references over unique ownership: 59fb88d061/library/core/src/cell.rs (L498-L499)
r? @RalfJung
Use intra-doc links in core/src/iter when possible
Helps with #75080.
I also updated lots of links to use `fn()` instead of `fn` when possible.
@rustbot modify labels: T-doc A-intra-doc-links
r? @jyn514
Stabilize some Option methods as const
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
These methods are currently const under the unstable feature `const_option` (tracking issue: #67441).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](https://github.com/rust-lang/rust/pull/75463).
Related: #76225
Remove MMX from Rust
Follow-up to https://github.com/rust-lang/stdarch/pull/890
This removes most of MMX from Rust (tests pass with small changes), keeping stable `is_x86_feature_detected!("mmx")` working.
Stabilize the following methods of `Option` as const:
- `is_some`
- `is_none`
- `as_ref`
Possible because of stabilization of #49146 (Allow if and match in constants).
Rollup of 15 pull requests
Successful merges:
- #76732 (Add docs for `BasicBlock`)
- #76832 (Let backends define custom targets)
- #76866 (Remove unused feature gates from library/ crates)
- #76875 (Move to intra-doc links in library/alloc/src/collections/binary_heap.rs)
- #76876 (Move to intra-doc links in collections/btree/map.rs and collections/linked_list.rs)
- #76877 (Move to intra-doc links in collections/vec_deque.rs and collections/vec_deque/drain.rs)
- #76878 (Move the version number to a plaintext file)
- #76883 (README.md: Remove prompts from code blocks)
- #76887 (Add missing examples on HashSet iter types)
- #76890 (use matches!() macro for simple if let conditions)
- #76891 (don't take `TyCtxt` by reference)
- #76910 (transmute: use diagnostic item)
- #76924 (Add tracking issue for feature(unix_socket_peek))
- #76926 (BTreeMap: code readability tweaks)
- #76940 (Don't allow implementing trait directly on type-alias-impl-trait)
Failed merges:
r? `@ghost`
transmute: use diagnostic item
closes#66075, we now have no remaining uses of `match_def_path` in the compiler while some uses still remain in `clippy`.
cc @RalfJung
Remove unused feature gates from library/ crates
Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.
Stabilize some Result methods as const
Stabilize the following methods of Result as const:
- `is_ok`
- `is_err`
- `as_ref`
A test is also included, analogous to the test for `const_option`.
These methods are currently const under the unstable feature `const_result` (tracking issue: #67520).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also: [PR#75463](https://github.com/rust-lang/rust/pull/75463) and [PR#76135](https://github.com/rust-lang/rust/pull/76135).
Note: these methods are the only methods currently under the `const_result` feature, thus this PR results in the removal of the feature.
Related: #76225
This made too many assumptions about platforms, breaking some things.
Will need to be added later with a better way of gating on proper
alignment, without hardcoding cfg(target_arch)s.
Add associated constant `BITS` to all integer types
Recently I've regularly come across this snippet (in a few different crates, including `core` and `std`):
```rust
std::mem::size_of<usize>() * 8
```
I think it's time for a `usize::BITS`.
do not inline black_box when building for Miri
We cannot do the assembly trick in Miri, but let's at least make sure MIR inlining does not circumvent the black_box.
Also use black_box instead of local optimization barriers in a few const tests.
Add array_windows fn
This mimicks the functionality added by array_chunks, and implements a const-generic form of
`windows`. It makes egregious use of `unsafe`, but by necessity because the array must be
re-interpreted as a slice of arrays, and unlike array_chunks this cannot be done by casting the
original array once, since each time the index is advanced it needs to move one element, not
`N`.
I'm planning on adding more tests, but this should be good enough as a premise for the functionality.
Notably: should there be more functions overwritten for the iterator implementation/in general?
~~I've marked the issue as #74985 as there is no corresponding exact issue for `array_windows`, but it's based of off `array_chunks`.~~
Edit: See Issue #75027 created by @lcnr for tracking issue
~~Do not merge until I add more tests, please.~~
r? @lcnr
Updated issue to #75027
Update to rm oob access
And hopefully fix docs as well
Fixed naming conflict in test
Fix test which used 1-indexing
Nth starts from 0, woops
Fix a bunch of off by 1 errors
See https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=757b311987e3fae1ca47122969acda5a
Add even more off by 1 errors
And also write `next` and `next_back` in terms of `nth` and `nth_back`.
Run fmt
Fix forgetting to change fn name in test
add nth_back test & document unsafe
Remove as_ref().unwrap()
Documented occurrences of unsafe, noting what invariants are maintained
Fix liballoc test suite for Miri
Mostly, fix the regression introduced by https://github.com/rust-lang/rust/pull/75207 that caused slices (i.e., references) to be created to invalid memory or memory that has aliasing pointers that we want to keep valid. @dylni this changes the type of `check_range` to only require the length, not the full reference to the slice, which indeed is all the information this function requires.
Also reduce the size of a test introduced in https://github.com/rust-lang/rust/pull/70793 to make it not take 3 minutes in Miri.
This makes https://github.com/RalfJung/miri-test-libstd work again.
Make all methods of `Duration` unstably const
Make the following methods of `Duration` unstable const under `duration_const_2`:
- `from_secs_f64`
- `from_secs_f32`
- `mul_f64`
- `mul_f32`
- `div_f64`
- `div_f32`
This results in all methods of `Duration` being (unstable) const.
Moved the tests to `library` as part of #76268.
Possible because of #72449, which made the relevant `f32` and `f64` methods const.
Tracking issue: #72440
r? @ecstatic-morse
Make some Ordering methods const
Resubmission of [PR#75463](https://github.com/rust-lang/rust/pull/75463) as per [PR#76172](https://github.com/rust-lang/rust/pull/76172).
Constify the following methods of `core::cmp::Ordering`:
- `reverse`
- `then`
Insta-stabilizes these methods as const under the `const_ordering` feature, as their implementation is a trivial match and the recent stabilization of #49146 (Allow `if` and `match` in constants).
Note: the `const_ordering` feature has never actually been used as these methods have not been `#[rustc_const_unstable]`.
Tracking issue: #76113
Note when a a move/borrow error is caused by a deref coercion
Fixes#73268
When a deref coercion occurs, we may end up with a move error if the
base value has been partially moved out of. However, we do not indicate
anywhere that a deref coercion is occuring, resulting in an error
message with a confusing span.
This PR adds an explicit note to move errors when a deref coercion is
involved. We mention the name of the type that the deref-coercion
resolved to, as well as the `Deref::Target` associated type being used.
Split `core::slice` to smaller mods
Unfortunately the `#[lang = "slice"]` is too big (3003 lines), I cannot split it further.
Note for reviewer:
* I split to multiple commits for easier reviewing, but I could git squash them all to one if requested.
* Recommend pulling this change locally and using advanced git diff viewer or this command:
```
git show --reverse --color-moved=dimmed-zebra master..
```
---
I split core/slice/mod.rs to these modules:
* `ascii`: For operations on `[u8]`.
* `cmp`: For comparison operations on `[T]`, like PartialEq and SliceContains impl.
* `index`: For indexing operations like Index/IndexMut and SliceIndex.
* `iter`: For Iterator definitions and implementation on `[T]`.
- `macros`: For iterator! and forward_iterator! macros.
* `raw`: For free function to create `&[T]` or `&mut [T]` from pointer + length or a reference.
The heapsort wrapper in mod.rs is removed in favor of reexport from `sort::heapsort`.
