Eliminate bounds checking in slice::Windows
This is how `<core::slice::Windows as Iterator>::next` looks right now:
```rust
fn next(&mut self) -> Option<&'a [T]> {
if self.size > self.v.len() {
None
} else {
let ret = Some(&self.v[..self.size]);
self.v = &self.v[1..];
ret
}
}
```
The line with `self.v = &self.v[1..];` relies on assumption that `self.v` is definitely not empty at this point. Else branch is taken when `self.size <= self.v.len()`, so `self.v` can be empty if `self.size` is zero. In practice, since `Windows` is never created directly but rather trough `[T]::windows` which panics when `size` is zero, `self.size` is never zero. However, the compiler doesn't know about this check, so it keeps the code which checks bounds and panics.
Using `NonZeroUsize` lets the compiler know about this invariant and reliably eliminate bounds checking without `unsafe` on `-O2`. Here is assembly of `Windows<'a, u32>::next` before and after this change ([goldbolt](https://godbolt.org/z/xrefzx)):
<details>
<summary>Before</summary>
```
example::next:
push rax
mov rcx, qword ptr [rdi + 8]
mov rdx, qword ptr [rdi + 16]
cmp rdx, rcx
jbe .LBB0_2
xor eax, eax
pop rcx
ret
.LBB0_2:
test rcx, rcx
je .LBB0_5
mov rax, qword ptr [rdi]
mov rsi, rax
add rsi, 4
add rcx, -1
mov qword ptr [rdi], rsi
mov qword ptr [rdi + 8], rcx
pop rcx
ret
.LBB0_5:
lea rdx, [rip + .L__unnamed_1]
mov edi, 1
xor esi, esi
call qword ptr [rip + core::slice::slice_index_order_fail@GOTPCREL]
ud2
.L__unnamed_2:
.ascii "./example.rs"
.L__unnamed_1:
.quad .L__unnamed_2
.asciz "\f\000\000\000\000\000\000\000\016\000\000\000\027\000\000"
```
</details>
<details>
<summary>After</summary>
```
example::next:
mov rcx, qword ptr [rdi + 8]
mov rdx, qword ptr [rdi + 16]
cmp rdx, rcx
jbe .LBB0_2
xor eax, eax
ret
.LBB0_2:
mov rax, qword ptr [rdi]
lea rsi, [rax + 4]
add rcx, -1
mov qword ptr [rdi], rsi
mov qword ptr [rdi + 8], rcx
ret
```
</details>
Note the lack of call to `core::slice::slice_index_order_fail` in second snippet.
#### Possible reasons _not_ to merge this PR:
* this changes the error message on panic in `[T]::windows`. However, AFAIK this messages are not covered by backwards compatibility policy.
resolve: improve "try using the enum's variant"
Fixes#73427.
This PR improves the "try using the enum's variant" suggestion:
- Variants in suggestions would not result in more errors (e.g. use of a struct variant is only suggested if the suggestion can trivially construct that variant). Therefore, suggestions are only emitted for variants that have no fields (since the suggestion can't know what value fields would have).
- Suggestions include the syntax for constructing the variant. If a struct or tuple variant is suggested, then it is constructed in the suggestion - unless in pattern-matching or when arguments are already provided.
- A help message is added which mentions the variants which are no longer suggested.
All of the diagnostic logic introduced by this PR is separated from the normal code path for a successful compilation.
r? `@estebank`
Add PartialEq impls for Vec <-> slice
This is a follow-up to #71660 and rust-lang/rfcs#2917 to add two more missing vec/slice PartialEq impls:
```
impl<A, B> PartialEq<[B]> for Vec<A> where A: PartialEq<B> { .. }
impl<A, B> PartialEq<Vec<B>> for [A] where A: PartialEq<B> { .. }
```
Since this is insta-stable, it should go through the `@rust-lang/libs` FCP process. Note that I used version 1.47.0 for the `stable` attribute because I assume this will not merge before the 1.46.0 branch is cut next week.
Rollup of 11 pull requests
Successful merges:
- #76784 (Add some docs to rustdoc::clean::inline and def_id functions)
- #76911 (fix VecDeque::iter_mut aliasing issues)
- #77400 (Fix suggestions for x.py setup)
- #77515 (Update to chalk 0.31)
- #77568 (inliner: use caller param_env)
- #77571 (Use matches! for core::char methods)
- #77582 (Move `EarlyOtherwiseBranch` to mir-opt-level 2)
- #77590 (Update RLS and Rustfmt)
- #77605 (Fix rustc_def_path to show the full path and not the trimmed one)
- #77614 (Let backends access span information)
- #77624 (Add c as a shorthand check alternative for new options #77603)
Failed merges:
r? `@ghost`
Add c as a shorthand check alternative for new options #77603
There is a missing "c" that is a shorthand for "check" in newly added match arm for handling check-specific options.
Let backends access span information
Sometimes, a backend may need to emit warnings, errors, or otherwise need to know the span of the current item in a basic block. So, add a `set_span` method to give the backend that information.
The `set_source_location` method already partially does this, however, it's disabled when debug info is disabled. There needs to be a way to unconditionally provide the span.
inliner: use caller param_env
We used the callee param env instead of the caller param env by accident in #77430, this PR fixes that and caches it in the `Inliner` struct.
fixes#77564
r? @ecstatic-morse
Update to chalk 0.31
Gonna assign @nikomatsakis to the review here, but since he is pretty busy recently, if anyone else wants to review this, that would be much appreciated.
r? @nikomatsakis
Fix suggestions for x.py setup
#76631 introduced a new `setup` command to x.py
By default the command prompts for a profile to use:
```
Welcome to the Rust project! What do you want to do with x.py?
a) Contribute to the standard library
b) Contribute to the compiler
c) Contribute to the compiler, and also modify LLVM or codegen
d) Install Rust from source
```
and then displays command suggestions, depending on which profile was chosen. However [the mapping between chosen profile](9cba260df0/src/bootstrap/setup.rs (L75-L85)) and [suggestion](9cba260df0/src/bootstrap/setup.rs (L42-L47)) isn't exact, leading to suggestions not being shown if the user presses `c` or `d`. (because "c" is translated to "llvm" and "d" to "maintainer", but suggestions trigger for "codegen" and "user" respectively)
A more thorough refactor would stop using "strings-as-type" to make sure this kind of error doesn't happen, but it may be overkill for that kind of "script" program?
Tagging the setup command author: @jyn514
Support static linking with glibc and target-feature=+crt-static
With this change, it's possible to build on a linux-gnu target and pass
RUSTFLAGS='-C target-feature=+crt-static' or the equivalent via a
`.cargo/config.toml` file, and get a statically linked executable.
Update to libc 0.2.78, which adds support for static linking with glibc.
Add `crt_static_respected` to the `linux_base` target spec.
Update `android_base` and `linux_musl_base` accordingly. Avoid enabling
crt_static_respected on Android platforms, since that hasn't been
tested.
Closes https://github.com/rust-lang/rust/issues/65447.
Add a command to install a git hook to automatically run `x.py test tidy --bless`
Some folks (such as myself) would probably find a lot of convenience in a pre-commit hook that automatically runs tidy before committing, to avoid burning CI time learning that your commit wasn't tidy.
I'm absolutely positive I have missed some stuff. I basically just got this to where you can run `./x.py run install-git-hook` and then clicked the commit button. Please let me know what else you'd like me to add before this can be merged!
[rustc-dev-guide companion PR](https://github.com/rust-lang/rustc-dev-guide/pull/848)
Sometimes, a backend may need to emit warnings, errors, or otherwise
need to know the span of the current item in a basic block. So, add a
set_span method to give the backend that information.
Separate projection bounds and predicates
Follow up to #72788.
- Rename `projection_predicates` to `item_bounds`
- Separate bounds on associated types (the things after the `:` in `type X: ...`) and opaque types (the things after `impl`) from predicates.
- Projection candidates now have the correct nested obligations
- Trait object candidates now check that the associated types on the trait object satisfy their bounds as nested obligations
- Type alias impl trait types are now checked (#73035)
- `feature(generic_associated_types)` no longer changes how we handle bounds (#73816)
Opening for a perf and crater runs.
r? `@nikomatsakis`
Only check the own predicates of associated types when confirming
projection candidates.
Also consider implied bounds when comparing trait and impl methods.
Normalizing `<dyn Iterator<Item = ()> as Iterator>::Item` no longer
requires selecting `dyn Iterator<Item = ()>: Iterator`. This was
previously worked around by using a special type-folder to normalize
things.
