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Rename MaybeUninit::write_slice
A step to push #79995 forward.
https://github.com/rust-lang/libs-team/issues/122 also suggested to make them inherent methods, but they can't be — they'd conflict with slice's regular methods.
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Implement intrinsics with fallback bodies
fixes #93145 (though we can port many more intrinsics)
cc #63585
The way this works is that the backend logic for generating custom code for intrinsics has been made fallible. The only failure path is "this intrinsic is unknown". The `Instance` (that was `InstanceDef::Intrinsic`) then gets converted to `InstanceDef::Item`, which represents the fallback body. A regular function call to that body is then codegenned. This is currently implemented for
* codegen_ssa (so llvm and gcc)
* codegen_cranelift
other backends will need to adjust, but they can just keep doing what they were doing if they prefer (though adding new intrinsics to the compiler will then require them to implement them, instead of getting the fallback body).
cc `@scottmcm` `@WaffleLapkin`
### todo
* [ ] miri support
* [x] default intrinsic name to name of function instead of requiring it to be specified in attribute
* [x] make sure that the bodies are always available (must be collected for metadata)
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Use generic `NonZero` internally.
Tracking issue: https://github.com/rust-lang/rust/issues/120257
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doc: add note about panicking examples for strict_overflow_ops
The first commit adds a note before the panicking examples for strict_overflow_ops to make it clearer that the following examples should panic and why, without needing the reader to hover the mouse over the information icon.
The second commit adds panicking examples for division by zero operations for strict division operations on unsigned numbers. The signed numbers already have two panicking examples each: one for division by zero and one for overflowing division (`MIN/-1`); this commit includes the division by zero examples for the unsigned numbers.
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Fix comment in core/src/str/validations.rs
Fix minor issue in the comment
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Bump Unicode to version 15.1.0, regenerate tables
r? ```@Manishearth```
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Waker::will_wake: Compare vtable address instead of its content
Optimize will_wake implementation by comparing vtable address instead of its content.
The existing best practice to avoid false negatives from will_wake is to define a waker vtable as a static item. That approach continues to works with the new implementation.
While this potentially changes the observable behaviour, the function is documented to work on a best-effort basis. The PartialEq impl for RawWaker remains as it was.
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I discovered that `impl Debug for str` is quite slow because it ends up doing a `unicode_data::grapheme_extend::lookup` for each char, which ends up doing a binary search.
This introduces a fast-path for ASCII chars which do not have this property.
The `lookup` is thus completely gone from profiles.
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Clarified docs on non-atomic oprations on owned/mut refs to atomics
I originally misinterpreted the documentation to mean that the compiler can/will automatically optimise away atomic operations whenever the data is owned or mutably referenced.
On re-reading I think it is not technically incorrect, but specifically mentioning _how_ the atomic operations can be avoided also prevents this misunderstanding.
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Add known issue of let binding to format_args doc
Simply add doc about https://github.com/rust-lang/rust/issues/92698.
`@rustbot` label +T-rustdoc -T-libs
r? `@GuillaumeGomez`
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implement `Default` for `AsciiChar`
This implements `Default` for `AsciiChar` in order to match `char`'s implementation.
From all the different possible ways to do this I think the clearest one is to have both `char` and `AsciiChar` impls together.
I've also updated the doc-comment of the default variant since rustdoc doesn't seem to indicate it otherwise. Probably the text could be improved, though. I couldn't find any similar examples in the codebase and suggestions are welcomed.
r? `@scottmcm`
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Clarify the lifetimes of allocations returned by the `Allocator` trait
The previous definition (accidentally) disallowed the implementation of stack-based allocators whose memory would become invalid once the lifetime of the allocator type ended.
This also ensures the validity of the following blanket implementation:
```rust
impl<A: Allocator> Allocator for &'_ A {}
```
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Additional doc links and explanation of `Wake`.
This is intended to clarify:
* That `Wake` exists and can be used instead of `RawWaker`.
* How to construct a `Waker` when you are looking at `Wake` (which was previously only documented in the example).
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Only one example is given (for each method)
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Turn `is_val_statically_known` into such an intrinsic to demonstrate. It is perfectly safe to call after all.
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The previous definition (accidentally) disallowed the implementation of
stack-based allocators whose memory would become invalid once the
lifetime of the allocator type ended.
This also ensures the validity of the following blanket implementation:
```rust
impl<A: Allocator> Allocator for &'_ A {}
```
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assert_unsafe_precondition cleanup
I moved the polymorphic `is_nonoverlapping` into the `Cell` function that uses it and renamed `intrinsics::is_nonoverlapping_mono` to just `intrinsics::is_nonoverlapping`.
We now also have some docs for `intrinsics::debug_assertions`.
r? RalfJung
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add note on comparing vtables / function pointers
Fixes https://github.com/rust-lang/rust/issues/99388
Fixes https://github.com/rust-lang/rust/issues/117047
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Rollup of 9 pull requests
Successful merges:
- #119213 (simd intrinsics: add simd_shuffle_generic and other missing intrinsics)
- #120272 (Suppress suggestions in derive macro)
- #120773 (large_assignments: Allow moves into functions)
- #120874 (Take empty `where` bounds into account when suggesting predicates)
- #120882 (interpret/write_discriminant: when encoding niched variant, ensure the stored value matches)
- #120883 (interpret: rename ReadExternStatic → ExternStatic)
- #120890 (Adapt `llvm-has-rust-patches` validation to take `llvm-config` into account.)
- #120895 (don't skip coercions for types with errors)
- #120896 (Print kind of coroutine closure)
r? `@ghost`
`@rustbot` modify labels: rollup
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Make the polymorphic is_nonoverlapping private
Fix assert_unsafe_precondition doc typos
Add docs for intrinsics::debug_assertions
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core: add Duration constructors
Add more `Duration` constructors.
Tracking issue: #120301.
These match similar convenience constructors available on both `chrono::Duration` and `time::Duration`.
What's the best ordering for these with respect to the existing constructors?
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Fix `clippy::correctness` in the library
needs https://github.com/rust-lang/backtrace-rs/pull/579 to be complete
for https://github.com/rust-lang/compiler-team/issues/709
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Suggest less bug-prone construction of Duration in docs
std::time::Duration has a well-known quirk: Duration::as_nanos() returns u128 [1], but Duration::from_nanos() takes u64 [2]. So these methods cannot easily roundtrip [3]. It is not possible to simply accept u128 in from_nanos [4], because it requires breaking other API [5].
It seems to me that callers have basically only two options:
1. `Duration::from_nanos(d.as_nanos() as u64)`, which is the "obvious" and buggy approach.
2. `Duration::new(d.as_secs(), d.subsecs_nanos())`, which only becomes apparent after reading and digesting the entire Duration struct documentation.
I suggest that the documentation of `from_nanos` is changed to make option 2 more easily discoverable.
There are two major usecases for this:
- "Weird math" operations that should not be supported directly by `Duration`, like squaring.
- "Disconnected roundtrips", where the u128 value is passed through various other stack frames, and perhaps reconstructed into a Duration on a different machine.
In both cases, it seems like a good idea to not tempt people into thinking "Eh, u64 is good enough, what could possibly go wrong!". That's why I want to add a note that points out the similarly-easy and *safe* way to reconstruct a Duration.
[1] https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.as_nanos
[2] https://doc.rust-lang.org/stable/std/time/struct.Duration.html#method.from_nanos
[3] https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=fa6bab2b6b72f20c14b5243610ea1dde
[4] https://github.com/rust-lang/rust/issues/103332
[5] https://github.com/rust-lang/rust/issues/51107#issuecomment-392353166
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Remove an unneeded helper from the tuple library code
Thanks to https://github.com/rust-lang/rust/pull/107022, this is just what `==` does, so we don't need the helper here anymore.
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This is intended to clarify:
* That `Wake` exists and can be used instead of `RawWaker`.
* How to construct a `Waker` when you are looking at `Wake`
(which was previously only documented in the example).
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simd intrinsics: add simd_shuffle_generic and other missing intrinsics
Also tweak the simd_shuffle docs a bit.
r? `@calebzulawski`
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Clarify that atomic and regular integers can differ in alignment
The documentation for atomic integers says that they have the "same in-memory representation" as their underlying integers. This might be misconstrued as implying that they have the same layout. Therefore, clarify that atomic integers' alignment is equal to their size.
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Add documentation on `str::starts_with`
Add documentation about a current footgun of `str::starts_with`
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Harmonize `AsyncFn` implementations, make async closures conditionally impl `Fn*` traits
This PR implements several changes to the built-in and libcore-provided implementations of `Fn*` and `AsyncFn*` to address two problems:
1. async closures do not implement the `Fn*` family traits, leading to breakage: https://crater-reports.s3.amazonaws.com/pr-120361/index.html
2. *references* to async closures do not implement `AsyncFn*`, as a consequence of the existing blanket impls of the shape `AsyncFn for F where F: Fn, F::Output: Future`.
In order to fix (1.), we implement `Fn` traits appropriately for async closures. It turns out that async closures can:
* always implement `FnOnce`, meaning that they're drop-in compatible with `FnOnce`-bound combinators like `Option::map`.
* conditionally implement `Fn`/`FnMut` if they have no captures, which means that existing usages of async closures should *probably* work without breakage (crater checking this: https://github.com/rust-lang/rust/pull/120712#issuecomment-1930587805).
In order to fix (2.), we make all of the built-in callables implement `AsyncFn*` via built-in impls, and instead adjust the blanket impls for `AsyncFn*` provided by libcore to match the blanket impls for `Fn*`.
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