Import the 2021 prelude in the core crate
The `core` crate currently imports the v1 prelude
b3df0d7e5e/library/core/src/lib.rs (L285-L287)
This recently caused an issue when updating the `portable-simd` subtree since it was using a trait that was added to the 2021 prelude: https://github.com/rust-lang/rust/pull/122905#discussion_r1536228822
To make it easier to have a consistent build environment for subtrees and submodules that get included in `core`, we will now import the 2021 prelude into `core`.
Fixes#122912
r? `@Nilstrieb`
warning: casting raw pointers to the same type and constness is unnecessary (`*mut V` -> `*mut V`)
--> library\alloc\src\collections\btree\map\entry.rs:357:31
|
357 | let val_ptr = root.borrow_mut().push(self.key, value) as *mut V;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `root.borrow_mut().push
(self.key, value)`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\alloc\src\ffi\c_str.rs:411:56
|
411 | let slice = slice::from_raw_parts_mut(ptr, len as usize);
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*mut T` -> `*mut T`)
--> library\alloc\src\slice.rs:516:25
|
516 | (buf.as_mut_ptr() as *mut T).add(buf.len()),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `buf.as_mut_ptr()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*mut T` -> `*mut T`)
--> library\alloc\src\slice.rs:537:21
|
537 | (buf.as_mut_ptr() as *mut T).add(buf.len()),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `buf.as_mut_ptr()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*const ()` -> `*const ()`)
--> library\alloc\src\task.rs:151:13
|
151 | waker as *const (),
| ^^^^^^^^^^^^^^^^^^ help: try: `waker`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*const ()` -> `*const ()`)
--> library\alloc\src\task.rs:323:13
|
323 | waker as *const (),
| ^^^^^^^^^^^^^^^^^^ help: try: `waker`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\std\src\sys_common\net.rs:110:21
|
110 | assert!(len as usize >= mem::size_of::<c::sockaddr_in>());
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\std\src\sys_common\net.rs:116:21
|
116 | assert!(len as usize >= mem::size_of::<c::sockaddr_in6>());
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
Clarify transmute example
The example claims using an iterator will copy the entire vector, but this is not true in practice thanks to internal specializations in the stdlib (see https://godbolt.org/z/cnxo3MYs5 for confirmation that this doesn't reallocate nor iterate over the vec's elements). Since neither the copy nor the optimization is guaranteed I opted for saying that they _may_ happen.
This saves some debug and scope metadata in every single function that calls it.
Normally wouldn't be worth it, but with the derives there's *so* many of these.
std:🧵 refine available_parallelism for solaris/illumos.
Rather than the system-wide available cpus fallback solution, we fetch the cpus bound to the current process.
panic-in-panic-hook: formatting a message that's just a string is risk-free
This slightly improves the output in the 'panic while processing panic' case if the panic message does not involve any formatting. Follow-up to https://github.com/rust-lang/rust/pull/122930.
r? ``@Amanieu``
Rename `Arguments::as_const_str` to `as_statically_known_str`
While `const` has a particular meaning about language guarantees, here
we need a fuzzier notion like whether constant propagation was
effective, and `statically_known` is the best term we have for now.
r? ``@RalfJung``
Fix compile of wasm64-unknown-unknown target
This target is a Tier 3 target so it's not tested on CI, and it's broken since last used so this commit fixes a small unwind-related issue that cropped up in the meantime.
While `const` has a particular meaning about language guarantees, here
we need a fuzzier notion like whether constant propagation was
effective, and `statically_known` is the best term we have for now.
Rollup of 9 pull requests
Successful merges:
- #121281 (regression test for #103626)
- #122168 (Fix validation on substituted callee bodies in MIR inliner)
- #122217 (Handle str literals written with `'` lexed as lifetime)
- #122379 (transmute: caution against int2ptr transmutation)
- #122840 (`rustdoc --test`: Prevent reaching the maximum size of command-line by using files for arguments if there are too many)
- #122907 (Uniquify `ReError` on input mode in canonicalizer)
- #122942 (Add test in higher ranked subtype)
- #122943 (add a couple more ice tests)
- #122963 (core/panicking: fix outdated comment)
r? `@ghost`
`@rustbot` modify labels: rollup
transmute: caution against int2ptr transmutation
This came up in https://github.com/rust-lang/rust/pull/121282.
Cc ```@saethlin``` ```@scottmcm```
Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
refactor check_{lang,library}_ub: use a single intrinsic
This enacts the plan I laid out [here](https://github.com/rust-lang/rust/pull/122282#issuecomment-1996917998): use a single intrinsic, called `ub_checks` (in aniticpation of https://github.com/rust-lang/compiler-team/issues/725), that just exposes the value of `debug_assertions` (consistently implemented in both codegen and the interpreter). Put the language vs library UB logic into the library.
This makes it easier to do something like https://github.com/rust-lang/rust/pull/122282 in the future: that just slightly alters the semantics of `ub_checks` (making it more approximating when crates built with different flags are mixed), but it no longer affects whether these checks can happen in Miri or compile-time.
The first commit just moves things around; I don't think these macros and functions belong into `intrinsics.rs` as they are not intrinsics.
r? `@saethlin`
Rollup of 11 pull requests
Successful merges:
- #120577 (Stabilize slice_split_at_unchecked)
- #122698 (Cancel `cargo update` job if there's no updates)
- #122780 (Rename `hir::Local` into `hir::LetStmt`)
- #122915 (Delay a bug if no RPITITs were found)
- #122916 (docs(sync): normalize dot in fn summaries)
- #122921 (Enable more mir-opt tests in debug builds)
- #122922 (-Zprint-type-sizes: print the types of awaitees and unnamed coroutine locals.)
- #122927 (Change an ICE regression test to use the original reproducer)
- #122930 (add panic location to 'panicked while processing panic')
- #122931 (Fix some typos in the pin.rs)
- #122933 (tag_for_variant follow-ups)
r? `@ghost`
`@rustbot` modify labels: rollup
Stabilize slice_split_at_unchecked
Greetings!
I took the opportunity, and I tried to stabilize the `slice_split_at_unchecked` feature. I followed the guidelines, and I hope everything was done correctly 🤞 .
Closes#76014
Let codegen decide when to `mem::swap` with immediates
Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea.
Thus this PR introduces a new `typed_swap` intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs.
r? oli-obk
Replaces #111744, and means we'll never need more libs PRs like #111803 or #107140
This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting binary.
Remove SpecOptionPartialEq
With the recent LLVM bump, the specialization for Option::partial_eq on types with niches is no longer necessary. I kept the manual implementation as it still gives us better codegen than the derive (will look at this seperately).
Also implemented PartialOrd/Ord by hand as it _somewhat_ improves codegen for #49892: https://godbolt.org/z/vx5Y6oW4Y
Doc Guarantee: BTree(Set|Map): `IntoIter` Iterate in Sorted by key Order
This Doc-only PR adds text to the IntoIterator implementation and IntoIter type for both BTreeMap and BTreeSet that states that the returned items will be in sorted-by-key order, this is a guarantee that is made by the iter() and iter_mut() methods of BTreeMap/Set and BTreeMap respectively, but not on into_iter methods or types.
I don't know how the IntoIter iteration would not be sorted by key, and I would like to rely on that behavior for my prefix_array crate.
The text appended to IntoIter documentation is based on each types respective iter() method documentation, as is the text used in the IntoIterator documentation; they are slightly inconsistent between Set/Map, but they are consistent within their own types documentation.
select Vec::from_iter impls in a const block to optimize compile times
Ignoring whitespace diffs should make this easier to review.
This relies on the trick from #122301
Split out from #120682
Make `type_ascribe!` not a built-in
The only weird thing is the macro expansion note. I wonder if we should suppress these 🤔
r? ````@fmease```` since you told me about builtin# lol
Add `usize::MAX` arg tests for Vec
Tests to prevent recurrence of the UB from the rust-lang/rust#122760 issue.
I skipped the `with_capacity`, `drain`, `reserve`, etc. APIs because they actually had a good assortment of tests earlier in the same file.
r? Nilstrieb
Relax SeqCst ordering in standard library.
Every single SeqCst in the standard library is unnecessary. In all cases, Relaxed or Release+Acquire was sufficient.
As I [wrote](https://marabos.nl/atomics/memory-ordering.html#common-misconceptions) in my book on atomics:
> [..] when reading code, SeqCst basically tells the reader: "this operation depends on the total order of every single SeqCst operation in the program," which is an incredibly far-reaching claim. The same code would likely be easier to review and verify if it used weaker memory ordering instead, if possible. For example, Release effectively tells the reader: "this relates to an acquire operation on the same variable," which involves far fewer considerations when forming an understanding of the code.
>
> It is advisable to see SeqCst as a warning sign. Seeing it in the wild often means that either something complicated is going on, or simply that the author did not take the time to analyze their memory ordering related assumptions, both of which are reasons for extra scrutiny.
r? ````@Amanieu```` ````@joboet````
This target is a Tier 3 target so it's not tested on CI, and it's broken
since last used so this commit fixes a small unwind-related issue that
cropped up in the meantime.
fix OOB pointer formed in Vec::index
Move the length check to before using `index` with `ptr::add` to prevent an out of bounds pointer from being formed.
Fixes#122760
For async closures, cap closure kind, get rid of `by_mut_body`
Right now we have three `AsyncFn*` traits, and three corresponding futures that are returned by the `call_*` functions for them. This is fine, but it is a bit excessive, since the future returned by `AsyncFn` and `AsyncFnMut` are identical. Really, the only distinction we need to make with these bodies is "by ref" and "by move".
This PR removes `AsyncFn::CallFuture` and renames `AsyncFnMut::CallMutFuture` to `AsyncFnMut::CallRefFuture`. This simplifies MIR building for async closures, since we don't need to build an extra "by mut" body, but just a "by move" body which is materially different.
We need to do a bit of delicate handling of the ClosureKind for async closures, since we need to "cap" it to `AsyncFnMut` in some cases when we only care about what body we're looking for.
This also fixes a bug where `<{async closure} as Fn>::call` was returning a body that takes the async-closure receiver *by move*.
This also helps align the `AsyncFn` traits to the `LendingFn` traits' eventual designs.
Expose `ucred::peer_cred` on QNX targets to enable dist builds
After following https://doc.rust-lang.org/rustc/platform-support/nto-qnx.html I attempted to run the following `x.py` command:
```bash
export build_env='
CC_aarch64-unknown-nto-qnx710=qcc
CFLAGS_aarch64-unknown-nto-qnx710=-Vgcc_ntoaarch64le_cxx
CXX_aarch64-unknown-nto-qnx710=qcc
AR_aarch64_unknown_nto_qnx710=ntoaarch64-ar
CC_x86_64-pc-nto-qnx710=qcc
CFLAGS_x86_64-pc-nto-qnx710=-Vgcc_ntox86_64_cxx
CXX_x86_64-pc-nto-qnx710=qcc
AR_x86_64_pc_nto_qnx710=ntox86_64-ar'
env $build_env ./x.py --stage 2 dist rust-std --target aarch64-unknown-nto-qnx710,x86_64-pc-nto-qnx710,x86_64-unknown-linux-gnu
```
The result was the following error:
```
Compiling object v0.32.2
Compiling std_detect v0.1.5 (/home/ana/git/rust-lang/rust/library/stdarch/crates/std_detect)
Compiling addr2line v0.21.0
error: function `peer_cred` is never used
--> library/std/src/os/unix/net/ucred.rs:89:12
|
89 | pub fn peer_cred(socket: &UnixStream) -> io::Result<UCred> {
| ^^^^^^^^^
|
= note: `-D dead-code` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(dead_code)]`
error: could not compile `std` (lib) due to 1 previous error
Build completed unsuccessfully in 0:06:25
```
I contacted `@flba-eb` and `@gh-tr` over email and we confirmed that `peer_cred` here should be flagged on `nto` targets. This should enable the clean `x.py --stage 2 dist rust-std` command on these platforms.
various clippy fixes
We need to keep the order of the given clippy lint rules before passing them.
Since clap doesn't offer any useful interface for this purpose out of the box,
we have to handle it manually.
Additionally, this PR makes `-D` rules work as expected. Previously, lint rules were limited to `-W`. By enabling `-D`, clippy began to complain numerous lines in the tree, all of which have been resolved in this PR as well.
Fixes#121481
cc `@matthiaskrgr`
Makes the iterator 2*usize larger, but I doubt that matters much.
In exchange, we save a lot on instruction count.
In the absence of delegation syntax,
we must forward all the specialized impls manually…
Stabilize associated type bounds (RFC 2289)
This PR stabilizes associated type bounds, which were laid out in [RFC 2289]. This gives us a shorthand to express nested type bounds that would otherwise need to be expressed with nested `impl Trait` or broken into several `where` clauses.
### What are we stabilizing?
We're stabilizing the associated item bounds syntax, which allows us to put bounds in associated type position within other bounds, i.e. `T: Trait<Assoc: Bounds...>`. See [RFC 2289] for motivation.
In all position, the associated type bound syntax expands into a set of two (or more) bounds, and never anything else (see "How does this differ[...]" section for more info).
Associated type bounds are stabilized in four positions:
* **`where` clauses (and APIT)** - This is equivalent to breaking up the bound into two (or more) `where` clauses. For example, `where T: Trait<Assoc: Bound>` is equivalent to `where T: Trait, <T as Trait>::Assoc: Bound`.
* **Supertraits** - Similar to above, `trait CopyIterator: Iterator<Item: Copy> {}`. This is almost equivalent to breaking up the bound into two (or more) `where` clauses; however, the bound on the associated item is implied whenever the trait is used. See #112573/#112629.
* **Associated type item bounds** - This allows constraining the *nested* rigid projections that are associated with a trait's associated types. e.g. `trait Trait { type Assoc: Trait2<Assoc2: Copy>; }`.
* **opaque item bounds (RPIT, TAIT)** - This allows constraining associated types that are associated with the opaque without having to *name* the opaque. For example, `impl Iterator<Item: Copy>` defines an iterator whose item is `Copy` without having to actually name that item bound.
The latter three are not expressible in surface Rust (though for associated type item bounds, this will change in #120752, which I don't believe should block this PR), so this does represent a slight expansion of what can be expressed in trait bounds.
### How does this differ from the RFC?
Compared to the RFC, the current implementation *always* desugars associated type bounds to sets of `ty::Clause`s internally. Specifically, it does *not* introduce a position-dependent desugaring as laid out in [RFC 2289], and in particular:
* It does *not* desugar to anonymous associated items in associated type item bounds.
* It does *not* desugar to nested RPITs in RPIT bounds, nor nested TAITs in TAIT bounds.
This position-dependent desugaring laid out in the RFC existed simply to side-step limitations of the trait solver, which have mostly been fixed in #120584. The desugaring laid out in the RFC also added unnecessary complication to the design of the feature, and introduces its own limitations to, for example:
* Conditionally lowering to nested `impl Trait` in certain positions such as RPIT and TAIT means that we inherit the limitations of RPIT/TAIT, namely lack of support for higher-ranked opaque inference. See this code example: https://github.com/rust-lang/rust/pull/120752#issuecomment-1979412531.
* Introducing anonymous associated types makes traits no longer object safe, since anonymous associated types are not nameable, and all associated types must be named in `dyn` types.
This last point motivates why this PR is *not* stabilizing support for associated type bounds in `dyn` types, e.g, `dyn Assoc<Item: Bound>`. Why? Because `dyn` types need to have *concrete* types for all associated items, this would necessitate a distinct lowering for associated type bounds, which seems both complicated and unnecessary compared to just requiring the user to write `impl Trait` themselves. See #120719.
### Implementation history:
Limited to the significant behavioral changes and fixes and relevant PRs, ping me if I left something out--
* #57428
* #108063
* #110512
* #112629
* #120719
* #120584Closes#52662
[RFC 2289]: https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html
core: document default attribute stabilization
As of now, the first release which stabilized the `#[default]` macro for the deriving the `Default` trait for enus is not documented.
I have had to search the [`RELEASES.md`](https://github.com/rust-lang/rust/blob/master/RELEASES.md) when making sure my code would be accepted by an older Rust compiler.
I just added a line in the doc comment since, as far as I know, there's no option to pass to the `#[stable()]` attribute.
I am open to improvements in the wording.
Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea.
So introduce a new `typed_swap` intrinsic with a fallback body, but replace that implementation for immediates and scalar pairs.
Add as_(mut_)ptr and as_(mut_)slice to raw array pointers
Hey, first time contributing to the standard libraries so not completely sure about the process.
These functions are complementary to the ones being added in #74265 . I found them missing on array pointers.
See also:
- ACP: https://github.com/rust-lang/libs-team/issues/321
- Tracking issue: #119834
Optimize `ptr::replace`
#83022 optimized `mem::replace` to reduce the number of `memcpy`s. `ptr::replace`, which is [documented to behave just like `mem::replace`](https://doc.rust-lang.org/nightly/std/ptr/fn.replace.html), was not optimized however, leading to [worse code](https://godbolt.org/z/T3hdEEdfe) and missed optimizations. This PR simply forwards `ptr::replace` to `mem::replace` to take advantage of the better implementation.
Use `UnsafeCell` for fast constant thread locals
This uses `UnsafeCell` instead of `static mut` for fast constant thread locals. This changes the type of the TLS shims to return `&UnsafeCell<T>` instead of `*mut T` which means they are always non-null so LLVM can optimize away the check for `Some` in `LocalKey::with` if `T` has no destructor.
LLVM is currently unable to do this optimization as we lose the fact that `__getit` always returns `Some` as it gets optimized to just returning the value of the TLS shim.
Bump windows-bindgen to 0.55.0
windows-bindgen is the crate used to generate std's Windows API bindings.
Not many changes for us, it's mostly just simplifying the generate code (e.g. no more `-> ()`). The one substantial change is some structs now use `i8` byte arrays instead of `u8`. However, this only impacts one test.
Mention labelled blocks in `break` docs
`break` doesn't require a loop, so note this in the docs. This is covered in the linked sections of the rust reference, but this page implied that `break` is only for loops.
`break` doesn't require a loop, so note this in the docs.
This is covered in the linked sections of the rust reference,
but this page implied that `break` is only for loops.
Cursor.rs documentation fix
Reason:
I've been learning Rust std library and got confused. Seek trait documentation clearly states that negative indexes will cause an error. And the code in the Cursor example uses negative index. I found myself trying to understand what am I missing until I've actually executed the code and got error. I decided to submit small fix to the documentation.
Rollup of 10 pull requests
Successful merges:
- #117118 ([AIX] Remove AixLinker's debuginfo() implementation)
- #121650 (change std::process to drop supplementary groups based on CAP_SETGID)
- #121764 (Make incremental sessions identity no longer depend on the crate names provided by source code)
- #122212 (Copy byval argument to alloca if alignment is insufficient)
- #122322 (coverage: Initial support for branch coverage instrumentation)
- #122373 (Fix the conflict problem between the diagnostics fixes of lint `unnecessary_qualification` and `unused_imports`)
- #122479 (Implement `Duration::as_millis_{f64,f32}`)
- #122487 (Rename `StmtKind::Local` variant into `StmtKind::Let`)
- #122498 (Update version of cc crate)
- #122503 (Make `SubdiagMessageOp` well-formed)
r? `@ghost`
`@rustbot` modify labels: rollup
Update version of cc crate
Reason:
In order to build the Windows version of the Rust toolchain for the Android platform, the following patch to the cc is crate is required to avoid incorrectly determining that we are building with the Android NDK: 57853c4bf8
This patch is present in version 1.0.80 and newer versions of the cc crate. The rustc source distribution currently has 3 different versions of cc in the vendor directory, only one of which has the necessary fix.
We (the Android Rust toolchain) are currently maintaining local patches to upgrade the cc crate dependency versions, which we would like to upstream.
Implement `Duration::as_millis_{f64,f32}`
Implementation of #122451.
Linked const-unstability to #72440, so the post there should probably be updated to mentions the 2 new methods when/if this PR is merged.
change std::process to drop supplementary groups based on CAP_SETGID
A trivial rebase of #95982
Should fix#39186 (from what I can tell)
Original description:
> Fixes#88716
>
> * Before this change, when a process was given a uid via `std::os::unix::process::CommandExt.uid`, there would be a `setgroups` call (when the process runs) to clear supplementary groups for the child **if the parent was root** (to remove potentially unwanted permissions).
> * After this change, supplementary groups are cleared if we have permission to do so, that is, if we have the CAP_SETGID capability.
>
> This new behavior was agreed upon in #88716 but there was a bit of uncertainty from `@Amanieu` here: [#88716 (comment)](https://github.com/rust-lang/rust/issues/88716#issuecomment-973366600)
>
> > I agree with this change, but is it really necessary to ignore an EPERM from setgroups? If you have permissions to change UID then you should also have permissions to change groups. I would feel more comfortable if we documented set_uid as requiring both UID and GID changing permissions.
>
> The way I've currently written it, we ignore an EPERM as that's what #88716 originally suggested. I'm not at all an expert in any of this so I'd appreciate feedback on whether that was the right way to go.
Reason:
In order to build the Windows version of the Rust toolchain for the Android platform, the following patch to the cc is crate is required to avoid incorrectly determining that we are building with the Android NDK: 57853c4bf8
This patch is present in version 1.0.80 and newer versions of the cc crate. The rustc source distribution currently has 3 different versions of cc in the vendor directory, only one of which has the necessary fix.
We (the Android Rust toolchain) are currently maintaining local patches to upgrade the cc crate dependency versions, which we would like to upstream.
Avoid closing invalid handles
Documentation for [`HandleOrInvalid`] has this note:
> If holds a handle other than `INVALID_HANDLE_VALUE`, it will close the handle on drop.
Documentation for [`HandleOrNull`] has this note:
> If this holds a non-null handle, it will close the handle on drop.
Currently, both will call `CloseHandle` on their invalid handles as a result of using `OwnedHandle` internally, contradicting the above paragraphs. This PR adds destructors that match the documentation.
```@rustbot``` label A-io O-windows T-libs
[`HandleOrInvalid`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrInvalid.html
[`HandleOrNull`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrNull.html
Rollup of 9 pull requests
Successful merges:
- #104353 (Add CStr::bytes iterator)
- #119676 (rustdoc-search: search types by higher-order functions)
- #120699 (Document `TRACK_DIAGNOSTIC` calls.)
- #121899 (Document how removing a type's field can be bad and what to do instead)
- #122405 (Add methods to create StableMIR constant)
- #122416 (Various style improvements to `rustc_lint::levels`)
- #122421 (Improve `Step` docs)
- #122440 (const-eval: organize and extend tests for required-consts)
- #122461 (fix unsoundness in Step::forward_unchecked for signed integers)
Failed merges:
- #122397 (Various cleanups around the const eval query providers)
r? `@ghost`
`@rustbot` modify labels: rollup
fix unsoundness in Step::forward_unchecked for signed integers
Fixes#122420
```rust
pub fn foo(a: i8, b: u8) -> i8 {
unsafe { a.checked_add_unsigned(b).unwrap_unchecked() }
}
```
still compiles down to a single arithmetic instruction ([godbolt](https://rust.godbolt.org/z/qsd3xYWfE)).
But we may be losing some loop optimizations if llvm can no longer easily derive that it's a finite counted loop from the no-wrapping flags.
Improve `Step` docs
It [came up on urlo](https://users.rust-lang.org/t/implement-trait-step-in-1-76-0/108204?u=cad97) that the unstable reason string isn't helpful, so just remove it; there's nothing meaningful to add here.
Also makes a couple drive-by improvements to the method docs -- removes incorrect references, changes `forward_checked`'s invariant formulation to match `backward_checked`'s, and adds a helpful corollary that `step_unchecked(a, 0)` is always safe.
Add CStr::bytes iterator
See rust-lang/libs-team#135 for an ACP.
Since rust-lang/libs-team#134 was also accepted, this type is now `core::ffi::c_str::Bytes` instead of `core::ffi::CStrBytes`.
unix time module now return result
First try to fix#108277 without break anything.
if anyone who read this know tips to be able to check compilation for different target I could use some help. So far I installed many target with rustup but `./x check --all-targets` doesn't seem to use them.
TODO:
- [x] better error
- [ ] test, how ?
`@rustbot` label -S-waiting-on-author +S-waiting-on-review
This commit provides a component model intrinsic in the standard library
by default on the `wasm32-wasip2` target. This intrinsic is not
required by the component model itself but is quite common to use, for
example it's needed if a wasm module receives a string or a list.
The intention of this commit is to provide an overridable definition in
the standard library through a weak definition of this function. That
means that downstream crates can provide their own customized and more
specific versions if they'd like, but the standard library's version
should suffice for general-purpose use.
The ordering of targets in `pal/mod.rs` did not end up using the wasip2
implementation, so after reordering that I've edited the implementation
to compile correctly.
Use `min_exhaustive_patterns` in core & std
[`min_exhaustive_patterns`](https://github.com/rust-lang/rust/issues/119612) provides a subset of the functionality of [`exhaustive_patterns`](https://github.com/rust-lang/rust/issues/51085) which is likely to be stabilized much earlier than the full feature.
The subset covers all the compiler and std use cases. `compiler/` [already uses it](9dd6eda778); this PR switches `std` over.
The dead_code lint was previously eroneously missing this dead code.
Since this lint bug has been fixed, the unused field need
to be removed or marked as `#[allow(dead_code)]`.
These structures API is common to all platforms so the code cannot be
removed and is hence marked allow(dead_code).
The dead_code lint was previously eroneously missing this dead code.
Since this lint bug has been fixed, the unused field need
to be removed or marked as `#[allow(dead_code)]`.
Given the nature of this code, I don't feel confident removing the field
so it is only marked as allow(dead_code).
Test wasm32-wasip1 in CI, not wasm32-unknown-unknown
This commit changes CI to no longer test the `wasm32-unknown-unknown` target and instead test the `wasm32-wasip1` target. There was some discussion of this in a [Zulip thread], and the motivations for this PR are:
* Runtime failures on `wasm32-unknown-unknown` print nothing, meaning all you get is "something failed". In contrast `wasm32-wasip1` can print to stdout/stderr.
* The unknown-unknown target is missing lots of pieces of libstd, and while `wasm32-wasip1` is also missing some pieces (e.g. threads) it's missing fewer pieces. This means that many more tests can be run.
Overall my hope is to improve the debuggability of wasm failures on CI and ideally be a bit less of a maintenance burden.
This commit specifically removes the testing of `wasm32-unknown-unknown` and replaces it with testing of `wasm32-wasip1`. Along the way there were a number of other archiectural changes made as well, including:
* A new `target.*.runtool` option can now be specified in `config.toml` which is passed as `--runtool` to `compiletest`. This is used to reimplement execution of WebAssembly in a less-wasm-specific fashion.
* The default value for `runtool` is an ambiently located WebAssembly runtime found on the system, if any. I've implemented logic for Wasmtime.
* Existing testing support for `wasm32-unknown-unknown` and Emscripten has been removed. I'm not aware of Emscripten testing being run any time recently and otherwise `wasm32-wasip1` is in theory the focus now.
* I've added a new `//@ needs-threads` directive for `compiletest` and classified a bunch of wasm-ignored tests as needing threads. In theory these tests can run on `wasm32-wasi-preview1-threads`, for example.
* I've tried to audit all existing tests that are either `ignore-emscripten` or `ignore-wasm*`. Many now run on `wasm32-wasip1` due to being able to emit error messages, for example. Many are updated with comments as to why they can't run as well.
* The `compiletest` output matching for `wasm32-wasip1` automatically uses "match a subset" mode implemented in `compiletest`. This is because WebAssembly runtimes often add extra information on failure, such as the `unreachable` instruction in `panic!`, which isn't able to be matched against the golden output from native platforms.
* I've ported most existing `run-make` tests that use custom Node.js wrapper scripts to the new run-make-based-in-Rust infrastructure. To do this I added `wasmparser` as a dependency of `run-make-support` for the various wasm tests to use that parse wasm files. The one test that executed WebAssembly now uses `wasmtime`-the-CLI to execute the test instead. I have not ported over an exception-handling test as Wasmtime doesn't implement this yet.
* I've updated the `test` crate to print out timing information for WASI targets as it can do that (gets a previously ignored test now passing).
* The `test-various` image now builds a WASI sysroot for the WASI target and additionally downloads a fixed release of Wasmtime, currently the latest one at 18.0.2, and uses that for testing.
[Zulip thread]: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Have.20wasm.20tests.20ever.20caused.20problems.20on.20CI.3F/near/424317944
This commit updates the libtest conditionals to use `std::time::Instant`
on WASI targets where it's implemented. Previously all wasm targets
wouldn't use this type.
std support for wasm32 panic=unwind
Tracking issue: #118168
This adds std support for `-Cpanic=unwind` on wasm, and with it slightly more fleshed out rustc support. Now, the stable default is still panic=abort without exception-handling, but if you `-Zbuild-std` with `RUSTFLAGS=-Cpanic=unwind`, you get wasm exception-handling try/catch blocks in the binary:
```rust
#[no_mangle]
pub fn foo_bar(x: bool) -> *mut u8 {
let s = Box::<str>::from("hello");
maybe_panic(x);
Box::into_raw(s).cast()
}
#[inline(never)]
#[no_mangle]
fn maybe_panic(x: bool) {
if x {
panic!("AAAAA");
}
}
```
```wat
;; snip...
(try $label$5
(do
(call $maybe_panic
(local.get $0)
)
(br $label$1)
)
(catch_all
(global.set $__stack_pointer
(local.get $1)
)
(call $__rust_dealloc
(local.get $2)
(i32.const 5)
(i32.const 1)
)
(rethrow $label$5)
)
)
;; snip...
```
std::threads: revisit stack address calculation on netbsd.
like older linux glibc versions, we need to get the guard size
and increasing the stack's bottom address accordingly.
Expose the Freeze trait again (unstably) and forbid implementing it manually
non-emoji version of https://github.com/rust-lang/rust/pull/121501
cc #60715
This trait is useful for generic constants (associated consts of generic traits). See the test (`tests/ui/associated-consts/freeze.rs`) added in this PR for a usage example. The builtin `Freeze` trait is the only way to do it, users cannot work around this issue.
It's also a useful trait for building some very specific abstrations, as shown by the usage by the `zerocopy` crate: https://github.com/google/zerocopy/issues/941
cc ```@RalfJung```
T-lang signed off on reexposing this unstably: https://github.com/rust-lang/rust/pull/121501#issuecomment-1969827742
Win10: Use `GetSystemTimePreciseAsFileTime` directly
On Windows 10 we can use `GetSystemTimePreciseAsFileTime` directly instead of lazy loading it (with a fallback).
Add slice::try_range
This adds a fallible version of the unstable `slice::range` (tracking: #76393) which is highly requested in the tracking issue.
Hoping this can slide by without an ACP (since the feature is already being tracked), but let me know otherwise.
Convert `Unix{Datagram,Stream}::{set_}passcred()` to per-OS traits
These methods are the pre-stabilized API for obtaining peer credentials from an `AF_UNIX` socket, part of the `unix_socket_ancillary_data` feature.
Their current behavior is to get/set one of the `SO_PASSCRED` (Linux), `LOCAL_CREDS_PERSISTENT` (FreeBSD), or `LOCAL_CREDS` (NetBSD) socket options. On other targets the `{set_}passcred()` methods do not exist.
There are two problems with this approach:
1. Having public methods only exist for certain targets isn't permitted in a stable `std` API.
2. These options have generally similar purposes, but they are non-POSIX and their details can differ in subtle and surprising ways (such as whether they continue to be set after the next call to `recvmsg()`).
Splitting into OS-specific extension traits is the preferred solution to both problems.
Rollup of 9 pull requests
Successful merges:
- #122275 (disable OOM test in Miri)
- #122276 (io::Read trait: make it more clear when we are adressing implementations vs callers)
- #122277 (BorrowedCursor docs clarification)
- #122286 (use Instance::expect_resolve() instead of unwraping Instance::resolve())
- #122290 (MIR printing: print the path of uneval'd const)
- #122293 (diagnostics: Do not suggest using `#[unix_sigpipe]` without a value)
- #122297 (bootstrap: document what the triples in 'Build' mean)
- #122302 (docs: Correct ptr/ref verbiage in SliceIndex docs.)
- #122304 (fix metadata for dyn-star in new solver)
r? `@ghost`
`@rustbot` modify labels: rollup
BorrowedCursor docs clarification
If one reads the `BorrowedCursor` docs without having seen `BorrowedBuf` before, it is quite easy to assume that "unfilled" and "uninit" are synonyms.
io::Read trait: make it more clear when we are adressing implementations vs callers
Inspired by [this](https://github.com/rust-lang/rust/issues/72186#issuecomment-1987076295) comment.
For some reason we only have that `buf` warning in `read` and `read_exact`, even though it affects a bunch of other functions of this trait as well. It doesn't seem worth copy-pasting the same text everywhere though so I did not change this.
Fix legacy numeric constant diag items
- missed syms for usize/isize
- missed diag items on unsigned integers
For rust-lang/rust-clippy#12312
r? ```@Nilstrieb```
Follow-up to #121272, #121361, #121667
This should be the last one 🤞 Sorry!
Dynamically size sigaltstk in std
On modern Linux with Intel AMX and 1KiB matrices,
Arm SVE with potentially 2KiB vectors,
and RISCV Vectors with up to 16KiB vectors,
we must handle dynamic signal stack sizes.
We can do so unconditionally by using getauxval,
but assuming it may return 0 as an answer,
thus falling back to the old constant if needed.
Fixes https://github.com/rust-lang/rust/issues/107795
Distinguish between library and lang UB in assert_unsafe_precondition
As described in https://github.com/rust-lang/rust/pull/121583#issuecomment-1963168186, `assert_unsafe_precondition` now explicitly distinguishes between language UB (conditions we explicitly optimize on) and library UB (things we document you shouldn't do, and maybe some library internals assume you don't do).
`debug_assert_nounwind` was originally added to avoid the "only at runtime" aspect of `assert_unsafe_precondition`. Since then the difference between the macros has gotten muddied. This totally revamps the situation.
Now _all_ preconditions shall be checked with `assert_unsafe_precondition`. If you have a precondition that's only checkable at runtime, do a `const_eval_select` hack, as done in this PR.
r? RalfJung
Implement junction_point
Implements https://github.com/rust-lang/rust/issues/121709
We already had a private implementation that we use for tests so we could just make that public. Except it was very hacky as it was only ever intended for use in testing. I've made an improved version that at least handles path conversion correctly and has less need for things like the `Align8` hack. There's still room for further improvement though.
impl From<TryReserveError> for io::Error
There's an obvious mapping between these two errors, and it makes I/O code less noisy.
I've chosen to use simple `ErrorKind::OutOfMemory` `io::Error`, without keeping `TryReserveError` for the `source()`, because:
* It matches current uses in libstd,
* `ErrorData::Custom` allocates, which is a risky proposition for handling OOM errors specifically.
* Currently `TryReserveError` has no public fields/methods, so it's usefulness is limited. How allocators should report errors, especially custom and verbose ones is still an open question.
Just in case I've added note in the doccomment that this may change.
The compiler forced me to declare stability of this impl. I think this implementation is simple enough that it doesn't need full-blown stabilization period, and I've marked it for the next release, but of course I can adjust the attribute if needed.
Vec::try_with_capacity
Related to #91913
Implements try_with_capacity for `Vec`, `VecDeque`, and `String`. I can follow it up with more collections if desired.
`Vec::try_with_capacity()` is functionally equivalent to the current stable:
```rust
let mut v = Vec::new();
v.try_reserve_exact(n)?
```
However, `try_reserve` calls non-inlined `finish_grow`, which requires old and new `Layout`, and is designed to reallocate memory. There is benefit to using `try_with_capacity`, besides syntax convenience, because it generates much smaller code at the call site with a direct call to the allocator. There's codegen test included.
It's also a very desirable functionality for users of `no_global_oom_handling` (Rust-for-Linux), since it makes a very commonly used function available in that environment (`with_capacity` is used much more frequently than all `(try_)reserve(_exact)`).
fix `close_read_wakes_up` test
On windows, `shutdown` does not interrupt `read`, even though we document that it does (see https://github.com/rust-lang/rust/issues/121594).
The `close_read_wakes_up` test has a race condition and only passes on windows if the `shutdown` happens before the `read`. This PR ignores the test on windows adds a sleep to make it more likely that the `read` happens before the `shutdown` and the test actually tests what it is supposed to test on other platforms.
I'm submitting this before any docs changes, so that we can find out on what platforms `shutdown` actually works as documented.
r? `@ChrisDenton`
align_offset, align_to: no longer allow implementations to spuriously fail to align
For a long time, we have allowed `align_offset` to fail to compute a properly aligned offset, and `align_to` to return a smaller-than-maximal "middle slice". This was done to cover the implementation of `align_offset` in const-eval and Miri. See https://github.com/rust-lang/rust/issues/62420 for more background. For about the same amount of time, this has caused confusion and surprise, where people didn't realize they have to write their code to be defensive against `align_offset` failures.
Another way to put this is: the specification is effectively non-deterministic, and non-determinism is hard to test for -- in particular if the implementation everyone uses to test always produces the same reliable result, and nobody expects it to be non-deterministic to begin with.
With https://github.com/rust-lang/rust/pull/117840, Miri has stopped making use of this liberty in the spec; it now always behaves like rustc. That only leaves const-eval as potential motivation for this behavior. I do not think this is sufficient motivation. Currently, none of the relevant functions are stably const: `align_offset` is unstably const, `align_to` is not const at all. I propose that if we ever want to make these const-stable, we just accept the fact that they can behave differently at compile-time vs at run-time. This is not the end of the world, and it seems to be much less surprising to programmers than unexpected non-determinism. (Related: https://github.com/rust-lang/rfcs/pull/3352.)
`@thomcc` has repeatedly made it clear that they strongly dislike the non-determinism in align_offset, so I expect they will support this. `@oli-obk,` what do you think? Also, whom else should we involve? The primary team responsible is clearly libs-api, so I will nominate this for them. However, allowing const-evaluated code to behave different from run-time code is t-lang territory. The thing is, this is not stabilizing anything t-lang-worthy immediately, but it still does make a decision we will be bound to: if we accept this change, then
- either `align_offset`/`align_to` can never be called in const fn,
- or we allow compile-time behavior to differ from run-time behavior.
So I will nominate for t-lang as well, with the question being: are you okay with accepting either of these outcomes (without committing to which one, just accepting that it has to be one of them)? This closes the door to "have `align_offset` and `align_to` at compile-time and also always have compile-time behavior match run-time behavior".
Closes https://github.com/rust-lang/rust/issues/62420
Add `#[inline]` to `BTreeMap::new` constructor
This PR add the `#[inline]` attribute to `BTreeMap::new` constructor as to make it eligible for inlining.
<details>
For some context: I was profiling `rustc --check-cfg` with callgrind and due to the way we currently setup all the targets and we end-up calling `BTreeMap::new` multiple times for (nearly) all the targets. Adding the `#[inline]` attribute reduced the number of instructions needed.
</details>
Fix quadratic behavior of repeated vectored writes
Some implementations of `Write::write_vectored` in the standard library (`BufWriter`, `LineWriter`, `Stdout`, `Stderr`) check all buffers to calculate the total length. This is O(n) over the number of buffers.
It's common that only a limited number of buffers is written at a time (e.g. 1024 for `writev(2)`). `write_vectored_all` will then call `write_vectored` repeatedly, leading to a runtime of O(n²) over the number of buffers.
This fix is to only calculate as much as needed if it's needed.
Here's a test program:
```rust
#![feature(write_all_vectored)]
use std::fs::File;
use std::io::{BufWriter, IoSlice, Write};
use std::time::Instant;
fn main() {
let buf = vec![b'\0'; 100_000_000];
let mut slices: Vec<IoSlice<'_>> = buf.chunks(100).map(IoSlice::new).collect();
let mut writer = BufWriter::new(File::create("/dev/null").unwrap());
let start = Instant::now();
write_smart(&slices, &mut writer);
println!("write_smart(): {:?}", start.elapsed());
let start = Instant::now();
writer.write_all_vectored(&mut slices).unwrap();
println!("write_all_vectored(): {:?}", start.elapsed());
}
fn write_smart(mut slices: &[IoSlice<'_>], writer: &mut impl Write) {
while !slices.is_empty() {
// Only try to write as many slices as can be written
let res = writer
.write_vectored(slices.get(..1024).unwrap_or(slices))
.unwrap();
slices = &slices[(res / 100)..];
}
}
```
Before this change:
```
write_smart(): 6.666952ms
write_all_vectored(): 498.437092ms
```
After this change:
```
write_smart(): 6.377158ms
write_all_vectored(): 6.923412ms
```
`LineWriter` (and by extension `Stdout`) isn't fully repaired by this because it looks for newlines. I could open an issue for that after this is merged, I think it's fixable but not trivially.
Improve std::fs::read_to_string example
Resolves [#118621](https://github.com/rust-lang/rust/issues/118621)
For the original code to succeed it requires address.txt to contain a socketaddress, however it is much easier to follow if this is just any strong - eg address could be a street address or just text.
Also changed the variable name from "foo" to something more meaningful as cargo clippy warns you against using foo as a placeholder.
```
$ cat main.rs
use std::fs;
use std::error::Error;
fn main() -> Result<(), Box<dyn Error>> {
let addr: String = fs::read_to_string("address.txt")?.parse()?;
println!("{}", addr);
Ok(())
}
$ cat address.txt
123 rusty lane
san francisco 94999
$ cargo run
Finished dev [unoptimized + debuginfo] target(s) in 0.00s
Running `/home/haydon/workspace/rust-test-pr/tester/target/debug/tester`
123 rusty lane
san francisco 94999
```
Make `std::os::unix::ucred` module private
Tracking issue: #42839
Currently, this unstable module exists: [`std::os::unix::ucred`](https://doc.rust-lang.org/stable/std/os/unix/ucred/index.html).
All it does is provide `UCred` (which is also available from `std::os::unix::net`), `impl_*` (which is probably a mishap and should be private) and `peer_cred` (which is undocumented but has a documented counterpart at `std::os::unix::net::UnixStream::peer_cred`).
This PR makes the entire `ucred` module private and moves it into `net`, because that's where it is used.
I hope it's fine to simply remove it without a deprecation phase. Otherwise, I can add back a deprecated reexport module `std::os::unix::ucred`.
`@rustbot` label: -T-libs +T-libs-api
Stabilize the `#[diagnostic]` namespace and `#[diagnostic::on_unimplemented]` attribute
This PR stabilizes the `#[diagnostic]` attribute namespace and a minimal option of the `#[diagnostic::on_unimplemented]` attribute.
The `#[diagnostic]` attribute namespace is meant to provide a home for attributes that allow users to influence error messages emitted by the compiler. The compiler is not guaranteed to use any of this hints, however it should accept any (non-)existing attribute in this namespace and potentially emit lint-warnings for unused attributes and options. This is meant to allow discarding certain attributes/options in the future to allow fundamental changes to the compiler without the need to keep then non-meaningful options working.
The `#[diagnostic::on_unimplemented]` attribute is allowed to appear on a trait definition. This allows crate authors to hint the compiler to emit a specific error message if a certain trait is not implemented. For the `#[diagnostic::on_unimplemented]` attribute the following options are implemented:
* `message` which provides the text for the top level error message
* `label` which provides the text for the label shown inline in the broken code in the error message
* `note` which provides additional notes.
The `note` option can appear several times, which results in several note messages being emitted. If any of the other options appears several times the first occurrence of the relevant option specifies the actually used value. Any other occurrence generates an lint warning. For any other non-existing option a lint-warning is generated.
All three options accept a text as argument. This text is allowed to contain format parameters referring to generic argument or `Self` by name via the `{Self}` or `{NameOfGenericArgument}` syntax. For any non-existing argument a lint warning is generated.
This allows to have a trait definition like:
```rust
#[diagnostic::on_unimplemented(
message = "My Message for `ImportantTrait<{A}>` is not implemented for `{Self}`",
label = "My Label",
note = "Note 1",
note = "Note 2"
)]
trait ImportantTrait<A> {}
```
which then generates for the following code
```rust
fn use_my_trait(_: impl ImportantTrait<i32>) {}
fn main() {
use_my_trait(String::new());
}
```
this error message:
```
error[E0277]: My Message for `ImportantTrait<i32>` is not implemented for `String`
--> src/main.rs:14:18
|
14 | use_my_trait(String::new());
| ------------ ^^^^^^^^^^^^^ My Label
| |
| required by a bound introduced by this call
|
= help: the trait `ImportantTrait<i32>` is not implemented for `String`
= note: Note 1
= note: Note 2
```
[Playground with the unstable feature](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=05133acce8e1d163d481e97631f17536)
Fixes#111996
Rollup of 9 pull requests
Successful merges:
- #121958 (Fix redundant import errors for preload extern crate)
- #121976 (Add an option to have an external download/bootstrap cache)
- #122022 (loongarch: add frecipe and relax target feature)
- #122026 (Do not try to format removed files)
- #122027 (Uplift some feeding out of `associated_type_for_impl_trait_in_impl` and into queries)
- #122063 (Make the lowering of `thir::ExprKind::If` easier to follow)
- #122074 (Add missing PartialOrd trait implementation doc for array)
- #122082 (remove outdated fixme comment)
- #122091 (Note why we're using a new thread in `test_get_os_named_thread`)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove unnecessary fixme on new thread stack size
As the FIXME itself notes, there's nothing to fix here.
And as the documentation for [`CreateThread`] says of `dwStackSize`, the value is rounded up to the nearest page. A 4kb stack is very small but perfectly usable if you're careful. Of course it will be very limited but there's no reason to add artificial limits. We don't know what the user is doing.
[`CreateThread`]: https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createthread
Refer to "slice" instead of "vector" in Ord and PartialOrd trait impl of slices
The trait implementation comments of Ord and PartialOrd for slice incorrectly mention "vectors" instead of "slices".
This PR fixes those two comments as requested in #122071.
Note why we're using a new thread in `test_get_os_named_thread`
``@RalfJung`` expressed some "surprise and confusion" about why we're spawning a new thread in this test. Hopefully this comment will help future readers.
Add missing PartialOrd trait implementation doc for array
Analogously to vectors and slices, this PR documents the lexicographic sorting of PartialOrd as rustdoc comment on the trait implementation of PartialOrd for arrays.
Associated issue: #122073.
bootstrap/libtest: print test name eagerly on failure even with `verbose-tests=false` / `--quiet`
Previously, libtest would wait until all tests finished running to print the progress, which made it
annoying to run many tests at once (since you don't know which have failed). Change it to print the
names as soon as they fail.
This makes it much easier to know which test failed without having to wait for compiletest to completely finish running. Before:
```
Testing stage0 compiletest suite=ui mode=ui (x86_64-unknown-linux-gnu)
running 15274 tests
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 88/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 176/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 264/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 352/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 440/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 528/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiFFiiiiiii
...
```
After:
```
Testing stage0 compiletest suite=ui mode=ui (x86_64-unknown-linux-gnu)
running 15274 tests
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 88/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 176/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 264/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 352/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 440/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii 528/15274
iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii
[ui] tests/ui/associated-type-bounds/implied-in-supertrait.rs ... F
[ui] tests/ui/associated-type-bounds/return-type-notation/basic.rs#next_with ... F
iiiiiiiiiiiii
...
```
This serves a similar use case to the existing RUSTC_TEST_FAIL_FAST, but is on by default and as a result much more discoverable. We should consider unifying RUSTC_TEST_FAIL_FAST with the `--no-fail-fast` flag in the future for consistency and discoverability.
