Optimize `rustc_lexer`
The `cursor.first()` method in `rustc_lexer` now calls the `chars.next()` method instead of `chars.nth_char(0)`.
This allows LLVM to optimize the code better. The biggest win is that `eat_while()` is now fully inlined and generates better assembly. This improves the lexer's performance by 35% in a micro-benchmark I made (Lexing all 18MB of code in the compiler directory). But lexing is only a small part of the overall compilation time, so I don't know how significant it is.
Big thanks to criterion and `cargo asm`.
Make `array::{try_from_fn, try_map}` and `Iterator::try_find` generic over `Try`
Fixes#85115
This only updates unstable functions.
`array::try_map` didn't actually exist before; this adds it under the still-open tracking issue #79711 from the old PR #79713.
Tracking issue for the new trait: #91285
This would also solve the return type question in for the proposed `Iterator::try_reduce` in #87054
Rollup of 10 pull requests
Successful merges:
- #88906 (Implement write() method for Box<MaybeUninit<T>>)
- #90269 (Make `Option::expect` unstably const)
- #90854 (Type can be unsized and uninhabited)
- #91170 (rustdoc: preload fonts)
- #91273 (Fix ICE #91268 by checking that the snippet ends with a `)`)
- #91381 (Android: -ldl must appear after -lgcc when linking)
- #91453 (Document Windows TLS drop behaviour)
- #91462 (Use try_normalize_erasing_regions in needs_drop)
- #91474 (suppress warning about set_errno being unused on DragonFly)
- #91483 (Sync rustfmt subtree)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
suppress warning about set_errno being unused on DragonFly
Other targets allow this function to be unused, DragonFly just misses out due to providing a specialization.
This fixes a build error for DragonFly.
Android: -ldl must appear after -lgcc when linking
#90846 accidentally broke Android builds because it causes the standard library to no longer use `dlsym` on Android. This results in `libdl` being ignored by the linker since no symbols are needed from it. However, we later import `libgcc` for unwinding which *does* depend on `libdl` for `dl_iterate_phdr`. Since linkers don't revisit previous libraries when resolving symbols, this causes a linker error due to an undefined reference to `dl_iterate_phdr`.
This is resolved by adding a second `-ldl` after `-lgcc` in the linker command-line.
Fix ICE #91268 by checking that the snippet ends with a `)`
Fix#91268
Previously it was assumed that the last character of `snippet` will be a `)`, so using `snippet.len() - 1` as an index should be safe. However as we see in the test, it is possible to enter that branch without a closing `)`, and it will trigger the panic if the last character happens to be multibyte.
The fix is to ensure that the snippet ends with `)`, and skip the suggestion otherwise.
rustdoc: preload fonts
Follow-up from #82315.
I noticed that font loading was so slow that even when loading from local disk, we get a flash of unstyled text (FOUT) followed by a reflow when the fonts load. With this change, we reliably get the appropriate fonts in the first render pass when loading locally, and we get it some of the time when loading from a website.
This only preloads woff2 versions. According to https://caniuse.com/?search=preload and https://caniuse.com/?search=woff2, all browsers that support preload also support woff2, so this is fine; we will never load two copies of a font.
Don't preload italic font faces because they aren't used on all pages.
Demo: https://rustdoc.crud.net/jsha/preload-fonts/std/string/struct.String.html
Implement write() method for Box<MaybeUninit<T>>
This adds method similar to `MaybeUninit::write` main difference being
it returns owned `Box`. This can be used to elide copy from stack
safely, however it's not currently tested that the optimization actually
occurs.
Analogous methods are not provided for `Rc` and `Arc` as those need to
handle the possibility of sharing. Some version of them may be added in
the future.
This was discussed in #63291 which this change extends.
Remove unnecessary check in VecDeque::grow
All callers already check that the buffer is full before calling
`grow()`. This is where it makes the most sense, since `grow()` is
`inline(never)` and we don't want to pay for a function call just for
that check.
It could also be argued that it would be correct to call `grow()` even
if the buffer wasn't full yet.
This change breaks no code since `grow()` is not `pub`.
Generic `core::ops` for `Simd<T, _>`
In order to maintain type soundness, we need to be sure we only implement an operation for `Simd<T, _> where T: SimdElement`... and also valid for that operation in general. While we could do this purely parametrically, it is more sound to implement the operators directly for the base scalar type arguments and then use type parameters to extend the operators to the "higher order" operations.
This implements that strategy and cleans up `simd::ops` into a few submodules:
- assign.rs: `core::ops::*Assign`
- deref.rs: `core::ops` impls which "deref" borrowed versions of the arguments
- unary.rs: encloses the logic for unary operators on `Simd`, as unary ops are much simpler
This is possible since everything need not be nested in a single maze of macros anymore. The result simplifies the logic and allows reasoning about what operators are valid based on the expressed trait bounds, and also reduces the size of the trait implementation output in rustdoc, for a huge win of 4 MB off the size of `struct.Simd.html`! This addresses a common user complaint, as the original was over 5.5 MB and capable of crashing browsers!
This also carries a fix for a type-inference-related breakage, by removing the autosplatting (vector + scalar binop) impls, as unfortunately the presence of autosplatting was capable of busting type inference. We will likely need to see results from a Crater run before we can understand how to re-land autosplatting.
Looks like Generator drop shims already have `post_borrowck_cleanup` run
on them. That's a bit surprising, since it means they're getting const-
and maybe borrow-checked? This merits further investigation, but for now
just preserve the status quo.
Escape backslash in single_char_pattern.rs
Escape backslash in single_char_pattern.
Previously, the proposed clippy fix for a single backslash in raw strings ```r"\"``` or ```r#"\"#``` was also only an unescaped, *single* ```'\'```:
```shell
warning: single-character string constant used as pattern
2 | let s = r#"abc\xyz/"#.find(r"\");
| ^^^^ help: try using a `char` instead: `'\'`
|
= note: `#[warn(clippy::single_char_pattern)]` on by default
```
This PR corrects this to a properly escaped *double* backslash ```'\\'```.
I haven't come up with any other problematic cases, a single quote was already handled.
Closes: #8060
changelog: Escape backslash in ``[`single_char_pattern`]``
Rollup of 12 pull requests
Successful merges:
- #89954 (Fix legacy_const_generic doc arguments display)
- #91321 (Handle placeholder regions in NLL type outlive constraints)
- #91329 (Fix incorrect usage of `EvaluatedToOk` when evaluating `TypeOutlives`)
- #91364 (Improve error message for incorrect field accesses through raw pointers)
- #91387 (Clarify and tidy up explanation of E0038)
- #91410 (Move `#![feature(const_precise_live_drops)]` checks earlier in the pipeline)
- #91435 (Improve diagnostic for missing half of binary operator in `if` condition)
- #91444 (disable tests in Miri that take too long)
- #91457 (Add additional test from rust issue number 91068)
- #91460 (Document how `last_os_error` should be used)
- #91464 (Document file path case sensitivity)
- #91466 (Improve the comments in `Symbol::interner`.)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Document how `last_os_error` should be used
It should be made clear that the state of the last OS error could change if another function call is made before the call to `Error::last_os_error()`.
Fixes: #53155
disable tests in Miri that take too long
Comparing slices of length `usize::MAX` diverges in Miri. In fact these tests even diverge in rustc unless `-O` is passed. I tried this code to check that:
```rust
#![feature(slice_take)]
const EMPTY_MAX: &'static [()] = &[(); usize::MAX];
fn main() {
let mut slice: &[_] = &[(); usize::MAX];
println!("1");
assert_eq!(Some(&[] as _), slice.take(usize::MAX..));
println!("2");
let remaining: &[_] = EMPTY_MAX;
println!("3");
assert_eq!(remaining, slice);
println!("4");
}
```
So, disable these tests in Miri for now.
Improve diagnostic for missing half of binary operator in `if` condition
Fixes#91421. I've also changed it so that it doesn't consume the `else` token in the error case, because it will try to consume it again afterwards, leading to this incorrect error message (where the `else` reported as missing is actually there):
```
error: expected one of `.`, `;`, `?`, `else`, or an operator, found `{`
--> src/main.rs:4:12
|
4 | } else { 4 };
| ^ expected one of `.`, `;`, `?`, `else`, or an operator
```
r? `@lcnr`
Move `#![feature(const_precise_live_drops)]` checks earlier in the pipeline
Should mitigate the issues found during MCP on #73255.
Once this is done, we should clean up the queries a bit, since I think `mir_drops_elaborated_and_const_checked` can be merged back into `mir_promoted`.
Fixes#90770.
cc ``@rust-lang/wg-const-eval``
r? ``@nikomatsakis`` (since they reviewed #71824)
Clarify and tidy up explanation of E0038
I ran into E0038 (specifically the `Self:Sized` constraint on object-safety) the other day and it seemed to me that the explanations I found floating around the internet were a bit .. wrong. Like they didn't make sense. And then I went and checked the official explanation here and it didn't make sense either.
As far as I can tell (reading through the history of the RFCs), two totally different aspects of object-safety have got tangled up in much of the writing on the subject:
- Object-safety related to "not even theoretically possible" issues. This includes things like "methods that take or return Self by value", which obviously will never work for an unsized type in a world with fixed-size stack frames (and it'd be an opaque type anyways, which, ugh). This sort of thing was originally decided method-by-method, with non-object-safe methods stripped from objects; but in [RFC 0255](https://rust-lang.github.io/rfcs/0255-object-safety.html) this sort of per-impossible-method reasoning was made into a per-trait safety property (with the escape hatch left in where users could mark methods `where Self:Sized` to have them stripped before the trait's object safety is considered).
- Object-safety related to "totally possible but ergonomically a little awkward" issues. Specifically in a trait with `Trait:Sized`, there's no a priori reason why this constraint makes the trait impossible to make into an object -- imagine it had nothing but harmless `&self`-taking methods. No problem! Who cares if the Trait requires its implementing types to be sized? As far as I can tell reading the history here, in both RFC 0255 and then later in [RFC 0546](https://rust-lang.github.io/rfcs/0546-Self-not-sized-by-default.html) it seems that the motivation for making `Trait:Sized` be non-object-safe has _nothing to do_ with the impossibility of making objects out of such types, and everything to do with enabling "[a trait object SomeTrait to implement the trait SomeTrait](https://rust-lang.github.io/rfcs/0546-Self-not-sized-by-default.html#motivation)". That is, since `dyn Trait` is unsized, if `Trait:Sized` then you can never have the automatic (and reasonable) ergonomic implicit `impl Trait for dyn Trait`. And the authors of that RFC really wanted that automatic implicit implementation of `Trait` for `dyn Trait`. So they just defined `Trait:Sized` as non-object safe -- no `dyn Trait` can ever exist that the compiler can't synthesize such an impl for. Well enough!
However, I noticed in my reading-and-reconstruction that lots of documentation on the internet, including forum and Q&A site answers and (most worrying) the compiler explanation all kinda grasp at something like the first ("not theoretically possible") explanation, and fail to mention the second ("just an ergonomic constraint") explanation. So I figured I'd clean up the docs to clarify, maybe confuse the next person less (unless of course I'm misreading the history here and misunderstanding motives -- please let me know if so!)
While here I also did some cleanups:
- Rewrote the preamble, trying to help the user get a little better oriented (I found the existing preamble a bit scattered).
- Modernized notation (using `dyn Trait`)
- Changed the section headings to all be written with the same logical sense: to all be written as "conditions that violate object safety" rather than a mix of that and the negated form "conditions that must not happen in order to ensure object safety".
I think there's a fair bit more to clean up in this doc -- the later sections get a bit rambly and I suspect there should be a completely separated-out section covering the `where Self:Sized` escape hatch for instructing the compiler to "do the old thing" and strip methods off traits when turning them into objects (it's a bit buried as a digression in the individual sub-error sections). But I did what I had time for now.
Fix incorrect usage of `EvaluatedToOk` when evaluating `TypeOutlives`
A global predicate is not guarnatenteed to outlive all regions.
If the predicate involves late-bound regions, then it may fail
to outlive other regions (e.g. `for<'b> &'b bool: 'static` does not
hold)
We now only produce `EvaluatedToOk` when a global predicate has no
late-bound regions - in that case, the ony region that can be present
in the type is 'static
