Formatter::with_options takes self as a mutable reference (`&'a mut
Formatter<'b>`). `'a` and `'b` need to be different lifetimes. Just taking `&'a
mut Formatter<'a>` and trusting in Rust being able to implicitely convert from
`&'a mut Formatter<'b>` if necessary (after all, `'a` must be smaller than `'b`
anyway) fails because `'b` is behind a *mutable* reference. For background on
on this behavior, see https://doc.rust-lang.org/nomicon/subtyping.html#variance.
The idea behind this is to make implementing `fmt::FormattingOptions` (as well
as any future changes to `std::Formatter`) easier.
In theory, this might have a negative performance impact because of the
additional function calls. However, I strongly believe that those will be
inlined anyway, thereby producing assembly code that has comparable performance.
clarify simd_relaxed_fma non-determinism
This is the safer spec in the sense that it is more likely to be satisfied by the backend -- and if people are okay with a non-deterministic result, I assume they don't care whether it's the same choice across all lanes or not?
Cc ``@calebzulawski`` ``@workingjubilee``
Rename `core_pattern_type` and `core_pattern_types` lib feature gates to `pattern_type_macro`
That's what the gates are actually gating, and the single char difference in naming was not helpful either
fixes#128987
Add lint against function pointer comparisons
This is kind of a follow-up to https://github.com/rust-lang/rust/pull/117758 where we added a lint against wide pointer comparisons for being ambiguous and unreliable; well function pointer comparisons are also unreliable. We should IMO follow a similar logic and warn people about it.
-----
## `unpredictable_function_pointer_comparisons`
*warn-by-default*
The `unpredictable_function_pointer_comparisons` lint checks comparison of function pointer as the operands.
### Example
```rust
fn foo() {}
let a = foo as fn();
let _ = a == foo;
```
### Explanation
Function pointers comparisons do not produce meaningful result since they are never guaranteed to be unique and could vary between different code generation units. Furthermore different function could have the same address after being merged together.
----
This PR also uplift the very similar `clippy::fn_address_comparisons` lint, which only linted on if one of the operand was an `ty::FnDef` while this PR lints proposes to lint on all `ty::FnPtr` and `ty::FnDef`.
```@rustbot``` labels +I-lang-nominated
~~Edit: Blocked on https://github.com/rust-lang/libs-team/issues/323 being accepted and it's follow-up pr~~
Update `NonZero` and `NonNull` to not field-project (per MCP#807)
https://github.com/rust-lang/compiler-team/issues/807#issuecomment-2506098540 was accepted, so this is the first PR towards moving the library to not using field projections into `[rustc_layout_scalar_valid_range_*]` types.
`NonZero` was already using `transmute` nearly everywhere, so there are very few changes to it.
`NonNull` needed more changes, but they're mostly simple, changing `.pointer` to `.as_ptr()`.
r? libs
cc #133324, which will tidy up some of the MIR from this a bit more, but isn't a blocker.
LLVM does not include an implementation of the va_arg instruction for
Xtensa. From what I understand, this is a conscious decision and
instead language frontends are encouraged to implement it themselves.
The rationale seems to be that loading values correctly requires
language and ABI-specific knowledge that LLVM lacks.
This is true of most architectures, and rustc already provides
implementation for a number of them. This commit extends the support to
include Xtensa.
See https://lists.llvm.org/pipermail/llvm-dev/2017-August/116337.html
for some discussion on the topic.
Unfortunately there does not seem to be a reference document for the
semantics of the va_list and va_arg on Xtensa. The most reliable source
is the GCC implementation, which this commit tries to follow. Clang also
provides its own compatible implementation.
This was tested for all the types that rustc allows in variadics.
Co-authored-by: Brian Tarricone <brian@tarricone.org>
Co-authored-by: Jonathan Bastien-Filiatrault <joe@x2a.org>
Co-authored-by: Paul Lietar <paul@lietar.net>
Approved in [ACP 491](https://github.com/rust-lang/libs-team/issues/491).
Remove the `unsafe` on `core::intrinsics::breakpoint()`, since it's a
safe intrinsic to call and has no prerequisites.
(Thanks to @zachs18 for figuring out the `bootstrap`/`not(bootstrap)`
logic.)
Stabilize `const_maybe_uninit_write`
Mark the following API const stable:
```rust
impl<T> MaybeUninit<T> {
pub const fn write(&mut self, val: T) -> &mut T;
}
```
This depends on `const_mut_refs` and [`const_maybe_uninit_assume_init`](https://github.com/rust-lang/rust/issues/86722), both of which have recently been stabilized.
Closes: <https://github.com/rust-lang/rust/issues/63567>
Mark the following API const stable:
impl<T> MaybeUninit<T> {
pub const fn write(&mut self, val: T) -> &mut T;
}
This depends on `const_mut_refs` and `const_maybe_uninit_assume_init`,
both of which have recently been stabilized.
Tracking issue: <https://github.com/rust-lang/rust/issues/63567>
Stabilize unsigned and float variants of `num_midpoint` feature
This PR proposes that we stabilize the unsigned variants of the [`num_midpoint`](https://github.com/rust-lang/rust/issues/110840#issue-1684506201) feature as well as the floats variants, since they are not subject to any unresolved questions, which is equivalent to doing `(a + b) / 2` (and `(a + b) >> 1`) in a sufficiently large number.
The stabilized API surface would be:
```rust
/// Calculates the middle point of `self` and `rhs`.
///
/// `midpoint(a, b)` is `(a + b) / 2` as if it were performed in a sufficiently-large unsigned integral type.
/// This implies that the result is always rounded towards negative infinity and that no overflow will ever occur.
impl u{8,16,32,64,128,size} {
pub const fn midpoint(self, rhs: Self) -> Self;
}
impl NonZeroU{8,16,32,64,size} {
pub const fn midpoint(self, rhs: Self) -> Self;
}
impl f{32,64} {
pub const fn midpoint(self, rhs: Self) -> Self;
}
```
The signed variants `u{8,16,32,64,128,size}` would remain gated, until a decision is made about the rounding mode, in other words that the [unresolved questions](https://github.com/rust-lang/rust/issues/110840#issue-1684506201) are resolved.
cc `@rust-lang/libs-api`
cc `@scottmcm`
r? libs-api
Mark `slice::copy_from_slice` unstably const
Tracking issue #131415
I used `const_eval_select` for runtime and const panic functions because const formatting isn't available yet.
Add diagnostic item for `std::ops::ControlFlow`
This will be used in Clippy to detect useless conversions done through `ControlFlow::map_break()` and `ControlFlow::map_continue()`.
