Clean up E0263 explanation #5
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@bors r+ rollup |
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Did you create the pr on your own fork? 🤣 |
GuillaumeGomez
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Jun 25, 2020
update from origin 2020-06-19
GuillaumeGomez
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Oct 9, 2020
This is a combination of 18 commits. Commit #2: Additional examples and some small improvements. Commit #3: fixed mir-opt non-mir extensions and spanview title elements Corrected a fairly recent assumption in runtest.rs that all MIR dump files end in .mir. (It was appending .mir to the graphviz .dot and spanview .html file names when generating blessed output files. That also left outdated files in the baseline alongside the files with the incorrect names, which I've now removed.) Updated spanview HTML title elements to match their content, replacing a hardcoded and incorrect name that was left in accidentally when originally submitted. Commit #4: added more test examples also improved Makefiles with support for non-zero exit status and to force validation of tests unless a specific test overrides it with a specific comment. Commit #5: Fixed rare issues after testing on real-world crate Commit #6: Addressed PR feedback, and removed temporary -Zexperimental-coverage -Zinstrument-coverage once again supports the latest capabilities of LLVM instrprof coverage instrumentation. Also fixed a bug in spanview. Commit #7: Fix closure handling, add tests for closures and inner items And cleaned up other tests for consistency, and to make it more clear where spans start/end by breaking up lines. Commit #8: renamed "typical" test results "expected" Now that the `llvm-cov show` tests are improved to normally expect matching actuals, and to allow individual tests to override that expectation. Commit #9: test coverage of inline generic struct function Commit #10: Addressed review feedback * Removed unnecessary Unreachable filter. * Replaced a match wildcard with remining variants. * Added more comments to help clarify the role of successors() in the CFG traversal Commit #11: refactoring based on feedback * refactored `fn coverage_spans()`. * changed the way I expand an empty coverage span to improve performance * fixed a typo that I had accidently left in, in visit.rs Commit #12: Optimized use of SourceMap and SourceFile Commit #13: Fixed a regression, and synched with upstream Some generated test file names changed due to some new change upstream. Commit rust-lang#14: Stripping out crate disambiguators from demangled names These can vary depending on the test platform. Commit rust-lang#15: Ignore llvm-cov show diff on test with generics, expand IO error message Tests with generics produce llvm-cov show results with demangled names that can include an unstable "crate disambiguator" (hex value). The value changes when run in the Rust CI Windows environment. I added a sed filter to strip them out (in a prior commit), but sed also appears to fail in the same environment. Until I can figure out a workaround, I'm just going to ignore this specific test result. I added a FIXME to follow up later, but it's not that critical. I also saw an error with Windows GNU, but the IO error did not specify a path for the directory or file that triggered the error. I updated the error messages to provide more info for next, time but also noticed some other tests with similar steps did not fail. Looks spurious. Commit rust-lang#16: Modify rust-demangler to strip disambiguators by default Commit rust-lang#17: Remove std::process::exit from coverage tests Due to Issue rust-lang#77553, programs that call std::process::exit() do not generate coverage results on Windows MSVC. Commit rust-lang#18: fix: test file paths exceeding Windows max path len
GuillaumeGomez
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Dec 1, 2020
Don't run `resolve_vars_if_possible` in `normalize_erasing_regions` Neither `@eddyb` nor I could figure out what this was for. I changed it to `assert_eq!(normalized_value, infcx.resolve_vars_if_possible(&normalized_value));` and it passed the UI test suite. <details><summary> Outdated, I figured out the issue - `needs_infer()` needs to come _after_ erasing the lifetimes </summary> Strangely, if I change it to `assert!(!normalized_value.needs_infer())` it panics almost immediately: ``` query stack during panic: #0 [normalize_generic_arg_after_erasing_regions] normalizing `<str::IsWhitespace as str::pattern::Pattern>::Searcher` #1 [needs_drop_raw] computing whether `str::iter::Split<str::IsWhitespace>` needs drop #2 [mir_built] building MIR for `str::<impl str>::split_whitespace` #3 [unsafety_check_result] unsafety-checking `str::<impl str>::split_whitespace` #4 [mir_const] processing MIR for `str::<impl str>::split_whitespace` #5 [mir_promoted] processing `str::<impl str>::split_whitespace` #6 [mir_borrowck] borrow-checking `str::<impl str>::split_whitespace` #7 [analysis] running analysis passes on this crate end of query stack ``` I'm not entirely sure what's going on - maybe the two disagree? </details> For context, this came up while reviewing rust-lang#77467 (cc `@lcnr).` Possibly this needs a crater run? r? `@nikomatsakis` cc `@matthewjasper`
GuillaumeGomez
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Feb 15, 2021
HWAddressSanitizer support # Motivation Compared to regular ASan, HWASan has a [smaller overhead](https://source.android.com/devices/tech/debug/hwasan). The difference in practice is that HWASan'ed code is more usable, e.g. Android device compiled with HWASan can be used as a daily driver. # Example ``` fn main() { let xs = vec![0, 1, 2, 3]; let _y = unsafe { *xs.as_ptr().offset(4) }; } ``` ``` ==223==ERROR: HWAddressSanitizer: tag-mismatch on address 0xefdeffff0050 at pc 0xaaaad00b3468 READ of size 4 at 0xefdeffff0050 tags: e5/00 (ptr/mem) in thread T0 #0 0xaaaad00b3464 (/root/main+0x53464) #1 0xaaaad00b39b4 (/root/main+0x539b4) #2 0xaaaad00b3dd0 (/root/main+0x53dd0) #3 0xaaaad00b61dc (/root/main+0x561dc) #4 0xaaaad00c0574 (/root/main+0x60574) #5 0xaaaad00b6290 (/root/main+0x56290) #6 0xaaaad00b6170 (/root/main+0x56170) #7 0xaaaad00b3578 (/root/main+0x53578) #8 0xffff81345e70 (/lib64/libc.so.6+0x20e70) #9 0xaaaad0096310 (/root/main+0x36310) [0xefdeffff0040,0xefdeffff0060) is a small allocated heap chunk; size: 32 offset: 16 0xefdeffff0050 is located 0 bytes to the right of 16-byte region [0xefdeffff0040,0xefdeffff0050) allocated here: #0 0xaaaad009bcdc (/root/main+0x3bcdc) #1 0xaaaad00b1eb0 (/root/main+0x51eb0) #2 0xaaaad00b20d4 (/root/main+0x520d4) #3 0xaaaad00b2800 (/root/main+0x52800) #4 0xaaaad00b1cf4 (/root/main+0x51cf4) #5 0xaaaad00b33d4 (/root/main+0x533d4) #6 0xaaaad00b39b4 (/root/main+0x539b4) #7 0xaaaad00b61dc (/root/main+0x561dc) #8 0xaaaad00b3578 (/root/main+0x53578) #9 0xaaaad0096310 (/root/main+0x36310) Thread: T0 0xeffe00002000 stack: [0xffffc0590000,0xffffc0d90000) sz: 8388608 tls: [0xffff81521020,0xffff815217d0) Memory tags around the buggy address (one tag corresponds to 16 bytes): 0xfefcefffef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffef90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefa0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffefe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefcefffeff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 =>0xfefceffff000: a2 a2 05 00 e5 [00] 00 00 00 00 00 00 00 00 00 00 0xfefceffff010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff070: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0xfefceffff080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Tags for short granules around the buggy address (one tag corresponds to 16 bytes): 0xfefcefffeff0: .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. =>0xfefceffff000: .. .. c5 .. .. [..] .. .. .. .. .. .. .. .. .. .. 0xfefceffff010: .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. See https://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html#short-granules for a description of short granule tags Registers where the failure occurred (pc 0xaaaad00b3468): x0 e500efdeffff0050 x1 0000000000000004 x2 0000ffffc0d8f5a0 x3 0200efff00000000 x4 0000ffffc0d8f4c0 x5 000000000000004f x6 00000ffffc0d8f36 x7 0000efff00000000 x8 e500efdeffff0050 x9 0200efff00000000 x10 0000000000000000 x11 0200efff00000000 x12 0200effe000006b0 x13 0200effe000006b0 x14 0000000000000008 x15 00000000c00000cf x16 0000aaaad00a0afc x17 0000000000000003 x18 0000000000000001 x19 0000ffffc0d8f718 x20 ba00ffffc0d8f7a0 x21 0000aaaad00962e0 x22 0000000000000000 x23 0000000000000000 x24 0000000000000000 x25 0000000000000000 x26 0000000000000000 x27 0000000000000000 x28 0000000000000000 x29 0000ffffc0d8f650 x30 0000aaaad00b3468 ``` # Comments/Caveats * HWASan is only supported on arm64. * I'm not sure if I should add a feature gate or piggyback on the existing one for sanitizers. * HWASan requires `-C target-feature=+tagged-globals`. That flag should probably be set transparently to the user. Not sure how to go about that. # TODO * Need more tests. * Update documentation. * Fix symbolization. * Integrate with CI
GuillaumeGomez
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Apr 12, 2023
Added the `[unnecessary_box_returns]` lint fixes #5 I'm not confident in the name of this lint. Let me know if you can think of something better --- changelog: New lint: ``[`unnecessary_box_returns`]`` [rust-lang#9102](rust-lang/rust-clippy#9102) <!-- changelog_checked -->
GuillaumeGomez
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May 10, 2023
…t, r=tmiasko Encode def span for foreign return-position `impl Trait` in trait Fixes rust-lang#111031, yet another def-span encoding issue :/ Includes a smaller repro than the issue, but I can confirm it ICEs: ``` query stack during panic: #0 [def_span] looking up span for `rpitit::Foo::bar::{opaque#0}` #1 [object_safety_violations] determining object safety of trait `rpitit::Foo` #2 [check_is_object_safe] checking if trait `rpitit::Foo` is object safe #3 [typeck] type-checking `main` #4 [used_trait_imports] finding used_trait_imports `main` #5 [analysis] running analysis passes on this crate ``` Luckily since this only affects nightly, this desn't need to be backported.
GuillaumeGomez
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Oct 14, 2023
…jackh726 Stabilize `async fn` and return-position `impl Trait` in trait # Stabilization report This report proposes the stabilization of `#![feature(return_position_impl_trait_in_trait)]` ([RPITIT][RFC 3425]) and `#![feature(async_fn_in_trait)]` ([AFIT][RFC 3185]). These are both long awaited features that increase the expressiveness of the Rust language and trait system. Closes rust-lang#91611 [RFC 3185]: https://rust-lang.github.io/rfcs/3185-static-async-fn-in-trait.html [RFC 3425]: https://rust-lang.github.io/rfcs/3425-return-position-impl-trait-in-traits.html ## Updates from thread The thread has covered two major concerns: * [Given that we don't have RTN, what should we stabilize?](rust-lang#115822 (comment)) -- proposed resolution is [adding a lint](rust-lang#115822 (comment)) and [careful messaging](rust-lang#115822 (comment)) * [Interaction between outlives bounds and capture semantics](rust-lang#115822 (comment)) -- This is fixable in a forwards-compatible way via rust-lang#116040, and also eventually via ATPIT. ## Stabilization Summary This stabilization allows the following examples to work. ### Example of return-position `impl Trait` in trait definition ```rust trait Bar { fn bar(self) -> impl Send; } ``` This declares a trait method that returns *some* type that implements `Send`. It's similar to writing the following using an associated type, except that the associated type is anonymous. ```rust trait Bar { type _0: Send; fn bar(self) -> Self::_0; } ``` ### Example of return-position `impl Trait` in trait implementation ```rust impl Bar for () { fn bar(self) -> impl Send {} } ``` This defines a method implementation that returns an opaque type, just like [RPIT][RFC 1522] does, except that all in-scope lifetimes are captured in the opaque type (as is already true for `async fn` and as is expected to be true for RPIT in Rust Edition 2024), as described below. [RFC 1522]: https://rust-lang.github.io/rfcs/1522-conservative-impl-trait.html ### Example of `async fn` in trait ```rust trait Bar { async fn bar(self); } impl Bar for () { async fn bar(self) {} } ``` This declares a trait method that returns *some* [`Future`](https://doc.rust-lang.org/core/future/trait.Future.html) and a corresponding method implementation. This is equivalent to writing the following using RPITIT. ```rust use core::future::Future; trait Bar { fn bar(self) -> impl Future<Output = ()>; } impl Bar for () { fn bar(self) -> impl Future<Output = ()> { async {} } } ``` The desirability of this desugaring being available is part of why RPITIT and AFIT are being proposed for stabilization at the same time. ## Motivation Long ago, Rust added [RPIT][RFC 1522] and [`async`/`await`][RFC 2394]. These are major features that are widely used in the ecosystem. However, until now, these feature could not be used in *traits* and trait implementations. This left traits as a kind of second-class citizen of the language. This stabilization fixes that. [RFC 2394]: https://rust-lang.github.io/rfcs/2394-async_await.html ### `async fn` in trait Async/await allows users to write asynchronous code much easier than they could before. However, it doesn't play nice with other core language features that make Rust the great language it is, like traits. Support for `async fn` in traits has been long anticipated and was not added before due to limitations in the compiler that have now been lifted. `async fn` in traits will unblock a lot of work in the ecosystem and the standard library. It is not currently possible to write a trait that is implemented using `async fn`. The workarounds that exist are undesirable because they require allocation and dynamic dispatch, and any trait that uses them will become obsolete once native `async fn` in trait is stabilized. We also have ample evidence that there is demand for this feature from the [`async-trait` crate][async-trait], which emulates the feature using dynamic dispatch. The async-trait crate is currently the #5 async crate on crates.io ranked by recent downloads, receiving over 78M all-time downloads. According to a [recent analysis][async-trait-analysis], 4% of all crates use the `#[async_trait]` macro it provides, representing 7% of all function and method signatures in trait definitions on crates.io. We think this is a *lower bound* on demand for the feature, because users are unlikely to use `#[async_trait]` on public traits on crates.io for the reasons already given. [async-trait]: https://crates.io/crates/async-trait [async-trait-analysis]: https://rust-lang.zulipchat.com/#narrow/stream/315482-t-compiler.2Fetc.2Fopaque-types/topic/RPIT.20capture.20rules.20.28capturing.20everything.29/near/389496292 ### Return-position `impl Trait` in trait `async fn` always desugars to a function that returns `impl Future`. ```rust! async fn foo() -> i32 { 100 } // Equivalent to: fn foo() -> impl Future<Output = i32> { async { 100 } } ``` All `async fn`s today can be rewritten this way. This is useful because it allows adding behavior that runs at the time of the function call, before the first `.await` on the returned future. In the spirit of supporting the same set of features on `async fn` in traits that we do outside of traits, it makes sense to stabilize this as well. As described by the [RPITIT RFC][rpitit-rfc], this includes the ability to mix and match the equivalent forms in traits and their corresponding impls: ```rust! trait Foo { async fn foo(self) -> i32; } // Can be implemented as: impl Foo for MyType { fn foo(self) -> impl Future<Output = i32> { async { 100 } } } ``` Return-position `impl Trait` in trait is useful for cases beyond async, just as regular RPIT is. As a simple example, the RFC showed an alternative way of writing the `IntoIterator` trait with one fewer associated type. ```rust! trait NewIntoIterator { type Item; fn new_into_iter(self) -> impl Iterator<Item = Self::Item>; } impl<T> NewIntoIterator for Vec<T> { type Item = T; fn new_into_iter(self) -> impl Iterator<Item = T> { self.into_iter() } } ``` [rpitit-rfc]: https://rust-lang.github.io/rfcs/3425-return-position-impl-trait-in-traits.html ## Major design decisions This section describes the major design decisions that were reached after the RFC was accepted: - EDIT: Lint against async fn in trait definitions - Until the [send bound problem](https://smallcultfollowing.com/babysteps/blog/2023/02/01/async-trait-send-bounds-part-1-intro/) is resolved, the use of `async fn` in trait definitions could lead to a bad experience for people using work-stealing executors (by far the most popular choice). However, there are significant use cases for which the current support is all that is needed (single-threaded executors, such as those used in embedded use cases, as well as thread-per-core setups). We are prioritizing serving users well over protecting people from misuse, and therefore, we opt to stabilize the full range of functionality; however, to help steer people correctly, we are will issue a warning on the use of `async fn` in trait definitions that advises users about the limitations. (See [this summary comment](rust-lang#115822 (comment)) for the details of the concern, and [this comment](rust-lang#115822 (comment)) for more details about the reasoning that led to this conclusion.) - Capture rules: - The RFC's initial capture rules for lifetimes in impls/traits were found to be imprecisely precise and to introduce various inconsistencies. After much discussion, the decision was reached to make `-> impl Trait` in traits/impls capture *all* in-scope parameters, including both lifetimes and types. This is a departure from the behavior of RPITs in other contexts; an RFC is currently being authored to change the behavior of RPITs in other contexts in a future edition. - Major discussion links: - [Lang team design meeting from 2023-07-26](https://hackmd.io/sFaSIMJOQcuwCdnUvCxtuQ?view) - Refinement: - The [refinement RFC] initially proposed that impl signatures that are more specific than their trait are not allowed unless the `#[refine]` attribute was included, but left it as an open question how to implement this. The stabilized proposal is that it is not a hard error to omit `#[refine]`, but there is a lint which fires if the impl's return type is more precise than the trait. This greatly simplified the desugaring and implementation while still achieving the original goal of ensuring that users do not accidentally commit to a more specific return type than they intended. - Major discussion links: - [Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/.60.23.5Brefine.5D.60.20as.20a.20lint) [refinement RFC]: https://rust-lang.github.io/rfcs/3245-refined-impls.html ## What is stabilized ### Async functions in traits and trait implementations * `async fn` are now supported in traits and trait implementations. * Associated functions in traits that are `async` may have default bodies. ### Return-position impl trait in traits and trait implementations * Return-position `impl Trait`s are now supported in traits and trait implementations. * Return-position `impl Trait` in implementations are treated like regular return-position `impl Trait`s, and therefore behave according to the same inference rules for hidden type inference and well-formedness. * Associated functions in traits that name return-position `impl Trait`s may have default bodies. * Implementations may provide either concrete types or `impl Trait` for each corresponding `impl Trait` in the trait method signature. For a detailed exploration of the technical implementation of return-position `impl Trait` in traits, see [the dev guide](https://rustc-dev-guide.rust-lang.org/return-position-impl-trait-in-trait.html). ### Mixing `async fn` in trait and return-position `impl Trait` in trait A trait function declaration that is `async fn ..() -> T` may be satisfied by an implementation function that returns `impl Future<Output = T>`, or vice versa. ```rust trait Async { async fn hello(); } impl Async for () { fn hello() -> impl Future<Output = ()> { async {} } } trait RPIT { fn hello() -> impl Future<Output = String>; } impl RPIT for () { async fn hello() -> String { "hello".to_string() } } ``` ### Return-position `impl Trait` in traits and trait implementations capture all in-scope lifetimes Described above in "major design decisions". ### Return-position `impl Trait` in traits are "always revealing" When a trait uses `-> impl Trait` in return position, it logically desugars to an associated type that represents the return (the actual implementation in the compiler is different, as described below). The value of this associated type is determined by the actual return type written in the impl; if the impl also uses `-> impl Trait` as the return type, then the value of the associated type is an opaque type scoped to the impl method (similar to what you would get when calling an inherent function returning `-> impl Trait`). As with any associated type, the value of this special associated type can be revealed by the compiler if the compiler can figure out what impl is being used. For example, given this trait: ```rust trait AsDebug { fn as_debug(&self) -> impl Debug; } ``` A function working with the trait generically is only able to see that the return value is `Debug`: ```rust fn foo<T: AsDebug>(t: &T) { let u = t.as_debug(); println!("{}", u); // ERROR: `u` is not known to implement `Display` } ``` But if a function calls `as_debug` on a known type (say, `u32`), it may be able to resolve the return type more specifically, if that implementation specifies a concrete type as well: ```rust impl AsDebug for u32 { fn as_debug(&self) -> u32 { *self } } fn foo(t: &u32) { let u: u32 = t.as_debug(); // OK! println!("{}", t.as_debug()); // ALSO OK (since `u32: Display`). } ``` The return type used in the impl therefore represents a **semver binding** promise from the impl author that the return type of `<u32 as AsDebug>::as_debug` will not change. This could come as a surprise to users, who might expect that they are free to change the return type to any other type that implements `Debug`. To address this, we include a [`refining_impl_trait` lint](rust-lang#115582) that warns if the impl uses a specific type -- the `impl AsDebug for u32` above, for example, would toggle the lint. The lint message explains what is going on and encourages users to `allow` the lint to indicate that they meant to refine the return type: ```rust impl AsDebug for u32 { #[allow(refining_impl_trait)] fn as_debug(&self) -> u32 { *self } } ``` [RFC rust-lang#3245](rust-lang/rfcs#3245) proposed a new attribute, `#[refine]`, that could also be used to "opt-in" to refinements like this (and which would then silence the lint). That RFC is not currently implemented -- the `#[refine]` attribute is also expected to reveal other details from the signature and has not yet been fully implemented. ### Return-position `impl Trait` and `async fn` in traits are opted-out of object safety checks when the parent function has `Self: Sized` ```rust trait IsObjectSafe { fn rpit() -> impl Sized where Self: Sized; async fn afit() where Self: Sized; } ``` Traits that mention return-position `impl Trait` or `async fn` in trait when the associated function includes a `Self: Sized` bound will remain object safe. That is because the associated function that defines them will be opted-out of the vtable of the trait, and the associated types will be unnameable from any trait object. This can alternatively be seen as a consequence of rust-lang#112319 (comment) and the desugaring of return-position `impl Trait` in traits to associated types which inherit the where-clauses of the associated function that defines them. ## What isn't stabilized (aka, potential future work) ### Dynamic dispatch As stabilized, traits containing RPITIT and AFIT are **not dyn compatible**. This means that you cannot create `dyn Trait` objects from them and can only use static dispatch. The reason for this limitation is that dynamic dispatch support for RPITIT and AFIT is more complex than static dispatch, as described on the [async fundamentals page](https://rust-lang.github.io/async-fundamentals-initiative/evaluation/challenges/dyn_traits.html). The primary challenge to using `dyn Trait` in today's Rust is that **`dyn Trait` today must list the values of all associated types**. This means you would have to write `dyn for<'s> Trait<Foo<'s> = XXX>` where `XXX` is the future type defined by the impl, such as `F_A`. This is not only verbose (or impossible), it also uniquely ties the `dyn Trait` to a particular impl, defeating the whole point of `dyn Trait`. The precise design for handling dynamic dispatch is not yet determined. Top candidates include: - [callee site selection][], in which we permit unsized return values so that the return type for an `-> impl Foo` method be can be `dyn Foo`, but then users must specify the type of wide pointer at the call-site in some fashion. - [`dyn*`][], where we create a built-in encapsulation of a "wide pointer" and map the associated type corresponding to an RPITIT to the corresponding `dyn*` type (`dyn*` itself is not exposed to users as a type in this proposal, though that could be a future extension). [callee site selection]: https://smallcultfollowing.com/babysteps/blog/2022/09/21/dyn-async-traits-part-9-callee-site-selection/ [`dyn*`]: https://smallcultfollowing.com/babysteps/blog/2022/03/29/dyn-can-we-make-dyn-sized/ ### Where-clause bounds on return-position `impl Trait` in traits or async futures (RTN/ART) One limitation of async fn in traits and RPITIT as stabilized is that there is no way for users to write code that adds additional bounds beyond those listed in the `-> impl Trait`. The most common example is wanting to write a generic function that requires that the future returned from an `async fn` be `Send`: ```rust trait Greet { async fn greet(&self); } fn greet_in_parallel<G: Greet>(g: &G) { runtime::spawn(async move { g.greet().await; //~ ERROR: future returned by `greet` may not be `Send` }) } ``` Currently, since the associated types added for the return type are anonymous, there is no where-clause that could be added to make this code compile. There have been various proposals for how to address this problem (e.g., [return type notation][rtn] or having an annotation to give a name to the associated type), but we leave the selection of one of those mechanisms to future work. [rtn]: https://smallcultfollowing.com/babysteps/blog/2023/02/13/return-type-notation-send-bounds-part-2/ In the meantime, there are workarounds that one can use to address this problem, listed below. #### Require all futures to be `Send` For many users, the trait may only ever be used with `Send` futures, in which case one can write an explicit `impl Future + Send`: ```rust trait Greet { fn greet(&self) -> impl Future<Output = ()> + Send; } ``` The nice thing about this is that it is still compatible with using `async fn` in the trait impl. In the async working group case studies, we found that this could work for the [builder provider API](https://rust-lang.github.io/async-fundamentals-initiative/evaluation/case-studies/builder-provider-api.html). This is also the default approach used by the `#[async_trait]` crate which, as we have noted, has seen widespread adoption. #### Avoid generics This problem only applies when the `Self` type is generic. If the `Self` type is known, then the precise return type from an `async fn` is revealed, and the `Send` bound can be inferred thanks to auto-trait leakage. Even in cases where generics may appear to be required, it is sometimes possible to rewrite the code to avoid them. The [socket handler refactor](https://rust-lang.github.io/async-fundamentals-initiative/evaluation/case-studies/socket-handler.html) case study provides one such example. ### Unify capture behavior for `-> impl Trait` in inherent methods and traits As stabilized, the capture behavior for `-> impl Trait` in a trait (whether as part of an async fn or a RPITIT) captures all types and lifetimes, whereas the existing behavior for inherent methods only captures types and lifetimes that are explicitly referenced. Capturing all lifetimes in traits was necessary to avoid various surprising inconsistencies; the expressed intent of the lang team is to extend that behavior so that we also capture all lifetimes in inherent methods, which would create more consistency and also address a common source of user confusion, but that will have to happen over the 2024 edition. The RFC is in progress. Should we opt not to accept that RFC, we can bring the capture behavior for `-> impl Trait` into alignment in other ways as part of the 2024 edition. ### `impl_trait_projections` Orthgonal to `async_fn_in_trait` and `return_position_impl_trait_in_trait`, since it can be triggered on stable code. This will be stabilized separately in [rust-lang#115659](rust-lang#115659). <details> If we try to write this code without `impl_trait_projections`, we will get an error: ```rust #![feature(async_fn_in_trait)] trait Foo { type Error; async fn foo(&mut self) -> Result<(), Self::Error>; } impl<T: Foo> Foo for &mut T { type Error = T::Error; async fn foo(&mut self) -> Result<(), Self::Error> { T::foo(self).await } } ``` The error relates to the use of `Self` in a trait impl when the self type has a lifetime. It can be worked around by rewriting the impl not to use `Self`: ```rust #![feature(async_fn_in_trait)] trait Foo { type Error; async fn foo(&mut self) -> Result<(), Self::Error>; } impl<T: Foo> Foo for &mut T { type Error = T::Error; async fn foo(&mut self) -> Result<(), <&mut T as Foo>::Error> { T::foo(self).await } } ``` </details> ## Tests Tests are generally organized between return-position `impl Trait` and `async fn` in trait, when the distinction matters. * RPITIT: https://github.com/rust-lang/rust/tree/master/tests/ui/impl-trait/in-trait * AFIT: https://github.com/rust-lang/rust/tree/master/tests/ui/async-await/in-trait ## Remaining bugs and open issues * rust-lang#112047: Indirection introduced by `async fn` and return-position `impl Trait` in traits may hide cycles in opaque types, causing overflow errors that can only be discovered by monomorphization. * rust-lang#111105 - `async fn` in trait is susceptible to issues with checking auto traits on futures' generators, like regular `async`. This is a manifestation of rust-lang#110338. * This was deemed not blocking because fixing it is forwards-compatible, and regular `async` is subject to the same issues. * rust-lang#104689: `async fn` and return-position `impl Trait` in trait requires the late-bound lifetimes in a trait and impl function signature to be equal. * This can be relaxed in the future with a smarter lexical region resolution algorithm. * rust-lang#102527: Nesting return-position `impl Trait` in trait deeply may result in slow compile times. * This has only been reported once, and can be fixed in the future. * rust-lang#108362: Inference between return types and generics of a function may have difficulties when there's an `.await`. * This isn't related to AFIT (rust-lang#108362 (comment)) -- using traits does mean that there's possibly easier ways to hit it. * rust-lang#112626: Because `async fn` and return-position `impl Trait` in traits lower to associated types, users may encounter strange behaviors when implementing circularly dependent traits. * This is not specific to RPITIT, and is a limitation of associated types: rust-lang#112626 (comment) * **(Nightly)** rust-lang#108309: `async fn` and return-position `impl Trait` in trait do not support specialization. This was deemed not blocking, since it can be fixed in the future (e.g. rust-lang#108321) and specialization is a nightly feature. #### (Nightly) Return type notation bugs RTN is not being stabilized here, but there are some interesting outstanding bugs. None of them are blockers for AFIT/RPITIT, but I'm noting them for completeness. <details> * rust-lang#109924 is a bug that occurs when a higher-ranked trait bound has both inference variables and associated types. This is pre-existing -- RTN just gives you a more convenient way of producing them. This should be fixed by the new trait solver. * rust-lang#109924 is a manifestation of a more general issue with `async` and auto-trait bounds: rust-lang#110338. RTN does not cause this issue, just allows us to put `Send` bounds on the anonymous futures that we have in traits. * rust-lang#112569 is a bug similar to associated type bounds, where nested bounds are not implied correctly. </details> ## Alternatives ### Do nothing We could choose not to stabilize these features. Users that can use the `#[async_trait]` macro would continue to do so. Library maintainers would continue to avoid async functions in traits, potentially blocking the stable release of many useful crates. ### Stabilize `impl Trait` in associated type instead AFIT and RPITIT solve the problem of returning unnameable types from trait methods. It is also possible to solve this by using another unstable feature, `impl Trait` in an associated type. Users would need to define an associated type in both the trait and trait impl: ```rust! trait Foo { type Fut<'a>: Future<Output = i32> where Self: 'a; fn foo(&self) -> Self::Fut<'_>; } impl Foo for MyType { type Fut<'a> where Self: 'a = impl Future<Output = i32>; fn foo(&self) -> Self::Fut<'_> { async { 42 } } } ``` This also has the advantage of allowing generic code to bound the associated type. However, it is substantially less ergonomic than either `async fn` or `-> impl Future`, and users still expect to be able to use those features in traits. **Even if this feature were stable, we would still want to stabilize AFIT and RPITIT.** That said, we can have both. `impl Trait` in associated types is desireable because it can be used in existing traits with explicit associated types, among other reasons. We *should* stabilize this feature once it is ready, but that's outside the scope of this proposal. ### Use the old capture semantics for RPITIT We could choose to make the capture rules for RPITIT consistent with the existing rules for RPIT. However, there was strong consensus in a recent [lang team meeting](https://hackmd.io/sFaSIMJOQcuwCdnUvCxtuQ?view) that we should *change* these rules, and furthermore that new features should adopt the new rules. This is consistent with the tenet in RFC 3085 of favoring ["Uniform behavior across editions"](https://rust-lang.github.io/rfcs/3085-edition-2021.html#uniform-behavior-across-editions) when possible. It greatly reduces the complexity of the feature by not requiring us to answer, or implement, the design questions that arise out of the interaction between the current capture rules and traits. This reduction in complexity – and eventual technical debt – is exactly in line with the motivation listed in the aforementioned RFC. ### Make refinement a hard error Refinement (`refining_impl_trait`) is only a concern for library authors, and therefore doesn't really warrant making into a deny-by-default warning or an error. Additionally, refinement is currently checked via a lint that compares bounds in the `impl Trait`s in the trait and impl syntactically. This is good enough for a warning that can be opted-out, but not if this were a hard error, which would ideally be implemented using fully semantic, implicational logic. This was implemented (rust-lang#111931), but also is an unnecessary burden on the type system for little pay-off. ## History - Dec 7, 2021: [RFC rust-lang#3185: Static async fn in traits](https://rust-lang.github.io/rfcs/3185-static-async-fn-in-trait.html) merged - Sep 9, 2022: [Initial implementation](rust-lang#101224) of AFIT and RPITIT landed - Jun 13, 2023: [RFC rust-lang#3425: Return position `impl Trait` in traits](https://rust-lang.github.io/rfcs/3425-return-position-impl-trait-in-traits.html) merged <!--These will render pretty when pasted into github--> Non-exhaustive list of PRs that are particularly relevant to the implementation: - rust-lang#101224 - rust-lang#103491 - rust-lang#104592 - rust-lang#108141 - rust-lang#108319 - rust-lang#108672 - rust-lang#112988 - rust-lang#113182 (later made redundant by rust-lang#114489) - rust-lang#113215 - rust-lang#114489 - rust-lang#115467 - rust-lang#115582 Doc co-authored by `@nikomatsakis,` `@tmandry,` `@traviscross.` Thanks also to `@spastorino,` `@cjgillot` (for changes to opaque captures!), `@oli-obk` for many reviews, and many other contributors and issue-filers. Apologies if I left your name off 😺
GuillaumeGomez
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Dec 8, 2023
Change prefetch to avoid deadlock Was abled to reproduce the deadlock in rust-lang#118205 and created a coredump when it happen. When looking at the backtraces I noticed that the prefetch of exported_symbols (Thread 17 frame 4) started after the "actual" exported_symbols (Thread 2 frame 18) but it also is working on some of the collect_crate_mono_items (Thread 17 frame12 ) that Thread 2 is blocked on resulting in a deadlock. This PR results in less parallell work that can be done at the same time but from what I can find we do not call the query exported_symbols from multiple places in the same join call any more. ``` Thread 17 (Thread 0x7f87b6299700 (LWP 11370)): #0 syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38 #1 0x00007f87be5166a9 in <parking_lot::condvar::Condvar>::wait_until_internal () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #2 0x00007f87be12d854 in <rustc_query_system::query::job::QueryLatch>::wait_on () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #3 0x00007f87bd27d16f in rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::CrateNum, rustc_middle::query::erase::Erased<[u8; 16]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #4 0x00007f87bd0b5b6a in rustc_query_impl::query_impl::exported_symbols::get_query_non_incr::__rust_end_short_backtrace () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #5 0x00007f87bdaebb0a in rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}::{closure#1} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #6 0x00007f87bdae1509 in rayon_core::join::join_context::call_b::<core::option::Option<rustc_data_structures::marker::FromDyn<&[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>>, rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<&[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}::{closure#1}, (), &[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>::{closure#0}::{closure#1}>::{closure#0}>::{closure#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #7 0x00007f87bdae32ff in <rayon_core::job::StackJob<rayon_core::latch::SpinLatch, rayon_core::join::join_context::call_b<core::option::Option<rustc_data_structures::marker::FromDyn<&[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>>, rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<&[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}::{closure#1}, (), &[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>::{closure#0}::{closure#1}>::{closure#0}>::{closure#0}, core::option::Option<rustc_data_structures::marker::FromDyn<&[(rustc_middle::middle::exported_symbols::ExportedSymbol, rustc_middle::middle::exported_symbols::SymbolExportInfo)]>>> as rayon_core::job::Job>::execute () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #8 0x00007f87b8338823 in <rayon_core::registry::WorkerThread>::wait_until_cold () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #9 0x00007f87bc2edbaf in rayon_core::join::join_context::<rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#0}, rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#1}, (), ()>::{closure#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #10 0x00007f87bc2ed313 in rayon_core::registry::in_worker::<rayon_core::join::join_context<rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#0}, rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#1}, (), ()>::{closure#0}, ((), ())> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #11 0x00007f87bc2db2a4 in rayon::iter::plumbing::bridge_producer_consumer::helper::<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #12 0x00007f87bc2eead2 in <rayon_core::job::StackJob<rayon_core::latch::SpinLatch, rayon_core::join::join_context::call_b<(), rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#1}>::{closure#0}, ()> as rayon_core::job::Job>::execute () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #13 0x00007f87b8338823 in <rayon_core::registry::WorkerThread>::wait_until_cold () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#14 0x00007f87be52d1f9 in <rayon_core::registry::ThreadBuilder>::run () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#15 0x00007f87b8461c57 in <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}::{closure#0}, ()> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#16 0x00007f87b846e465 in rustc_span::set_session_globals_then::<(), rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}::{closure#0}> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#17 0x00007f87b844f282 in <<crossbeam_utils::thread::ScopedThreadBuilder>::spawn<<rayon_core::ThreadPoolBuilder>::build_scoped<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}, rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}, ()>::{closure#0} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#18 0x00007f87b846af58 in <<std::thread::Builder>::spawn_unchecked_<alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output = ()> + core::marker::Send>, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#19 0x00007f87b7898e85 in std::sys::unix::thread::Thread::new::thread_start () from /home/andjo403/.rustup/toolchains/stage1/lib/libstd-d570b0650d35d951.so rust-lang#20 0x00007f87b7615609 in start_thread (arg=<optimized out>) at pthread_create.c:477 rust-lang#21 0x00007f87b7755133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 Thread 2 (Thread 0x7f87b729b700 (LWP 11368)): #0 syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38 #1 0x00007f87b7887b51 in std::sys::unix::locks::futex_condvar::Condvar::wait () from /home/andjo403/.rustup/toolchains/stage1/lib/libstd-d570b0650d35d951.so #2 0x00007f87b8339478 in <rayon_core::sleep::Sleep>::sleep () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #3 0x00007f87b83387c3 in <rayon_core::registry::WorkerThread>::wait_until_cold () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #4 0x00007f87bc2edbaf in rayon_core::join::join_context::<rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#0}, rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#1}, (), ()>::{closure#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #5 0x00007f87bc2ed313 in rayon_core::registry::in_worker::<rayon_core::join::join_context<rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#0}, rayon::iter::plumbing::bridge_producer_consumer::helper<rayon::vec::DrainProducer<rustc_middle::mir::mono::MonoItem>, rayon::iter::for_each::ForEachConsumer<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}>>::{closure#1}, (), ()>::{closure#0}, ((), ())> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #6 0x00007f87bc2db50c in <rayon::vec::IntoIter<rustc_middle::mir::mono::MonoItem> as rayon::iter::ParallelIterator>::for_each::<rustc_data_structures::sync::parallel::enabled::par_for_each_in<rustc_middle::mir::mono::MonoItem, alloc::vec::Vec<rustc_middle::mir::mono::MonoItem>, rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}::{closure#0}>::{closure#0}::{closure#0}> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #7 0x00007f87bc2e8cd7 in <rustc_session::session::Session>::time::<(), rustc_monomorphize::collector::collect_crate_mono_items::{closure#1}> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #8 0x00007f87bc2b8f2c in rustc_monomorphize::collector::collect_crate_mono_items () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #9 0x00007f87bc2c30d9 in rustc_monomorphize::partitioning::collect_and_partition_mono_items () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #10 0x00007f87bcf2cde6 in rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 24]>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #11 0x00007f87bd156a3c in <rustc_query_impl::query_impl::collect_and_partition_mono_items::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, ())>>::call_once () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #12 0x00007f87bd1c6a7d in rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::SingleCache<rustc_middle::query::erase::Erased<[u8; 24]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so #13 0x00007f87bd15df40 in rustc_query_impl::query_impl::collect_and_partition_mono_items::get_query_non_incr::__rust_end_short_backtrace () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#14 0x00007f87bd7a0ad9 in rustc_codegen_ssa::back::symbol_export::exported_symbols_provider_local () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#15 0x00007f87bcf29acb in rustc_query_impl::plumbing::__rust_begin_short_backtrace::<rustc_query_impl::query_impl::exported_symbols::dynamic_query::{closure#2}::{closure#0}, rustc_middle::query::erase::Erased<[u8; 16]>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#16 0x00007f87bcfdb350 in <rustc_query_impl::query_impl::exported_symbols::dynamic_query::{closure#2} as core::ops::function::FnOnce<(rustc_middle::ty::context::TyCtxt, rustc_span::def_id::CrateNum)>>::call_once () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#17 0x00007f87bd27d64f in rustc_query_system::query::plumbing::try_execute_query::<rustc_query_impl::DynamicConfig<rustc_query_system::query::caches::VecCache<rustc_span::def_id::CrateNum, rustc_middle::query::erase::Erased<[u8; 16]>>, false, false, false>, rustc_query_impl::plumbing::QueryCtxt, false> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#18 0x00007f87bd0b5b6a in rustc_query_impl::query_impl::exported_symbols::get_query_non_incr::__rust_end_short_backtrace () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#19 0x00007f87bda927ce in rustc_middle::query::plumbing::query_get_at::<rustc_query_system::query::caches::VecCache<rustc_span::def_id::CrateNum, rustc_middle::query::erase::Erased<[u8; 16]>>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#20 0x00007f87bda9c93f in <rustc_metadata::rmeta::encoder::EncodeContext>::encode_crate_root () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#21 0x00007f87bdaa6ef7 in rustc_metadata::rmeta::encoder::encode_metadata_impl () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#22 0x00007f87bdae0b77 in rayon_core::join::join_context::<rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<()>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}, (), ()>::{closure#0}::{closure#0}>::{closure#0}, rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<()>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}, (), ()>::{closure#0}::{closure#1}>::{closure#0}, core::option::Option<rustc_data_structures::marker::FromDyn<()>>, core::option::Option<rustc_data_structures::marker::FromDyn<()>>>::{closure#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#23 0x00007f87bdaded2f in rayon_core::registry::in_worker::<rayon_core::join::join_context<rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<()>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}, (), ()>::{closure#0}::{closure#0}>::{closure#0}, rayon_core::join::join::call<core::option::Option<rustc_data_structures::marker::FromDyn<()>>, rustc_data_structures::sync::parallel::enabled::join<rustc_metadata::rmeta::encoder::encode_metadata::{closure#0}, rustc_metadata::rmeta::encoder::encode_metadata::{closure#1}, (), ()>::{closure#0}::{closure#1}>::{closure#0}, core::option::Option<rustc_data_structures::marker::FromDyn<()>>, core::option::Option<rustc_data_structures::marker::FromDyn<()>>>::{closure#0}, (core::option::Option<rustc_data_structures::marker::FromDyn<()>>, core::option::Option<rustc_data_structures::marker::FromDyn<()>>)> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#24 0x00007f87bdaa5a03 in rustc_metadata::rmeta::encoder::encode_metadata () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#25 0x00007f87bdaed628 in rustc_metadata::fs::encode_and_write_metadata () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#26 0x00007f87b86608be in rustc_interface::passes::start_codegen () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#27 0x00007f87b8664946 in <rustc_middle::ty::context::GlobalCtxt>::enter::<<rustc_interface::queries::Queries>::codegen_and_build_linker::{closure#0}, core::result::Result<rustc_interface::queries::Linker, rustc_span::ErrorGuaranteed>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#28 0x00007f87b864db00 in <rustc_interface::queries::Queries>::codegen_and_build_linker () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#29 0x00007f87b849400f in <rustc_interface::interface::Compiler>::enter::<rustc_driver_impl::run_compiler::{closure#0}::{closure#0}, core::result::Result<core::option::Option<rustc_interface::queries::Linker>, rustc_span::ErrorGuaranteed>> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#30 0x00007f87b846e067 in rustc_span::set_source_map::<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}::{closure#0}> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#31 0x00007f87b844dc13 in <rayon_core::thread_pool::ThreadPool>::install::<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#32 0x00007f87b84509a1 in <rayon_core::job::StackJob<rayon_core::latch::LatchRef<rayon_core::latch::LockLatch>, <rayon_core::registry::Registry>::in_worker_cold<<rayon_core::thread_pool::ThreadPool>::install<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>> as rayon_core::job::Job>::execute () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#33 0x00007f87b8338823 in <rayon_core::registry::WorkerThread>::wait_until_cold () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#34 0x00007f87be52d1f9 in <rayon_core::registry::ThreadBuilder>::run () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#35 0x00007f87b8461c57 in <scoped_tls::ScopedKey<rustc_span::SessionGlobals>>::set::<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}::{closure#0}, ()> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#36 0x00007f87b846e465 in rustc_span::set_session_globals_then::<(), rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}::{closure#0}> () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#37 0x00007f87b844f282 in <<crossbeam_utils::thread::ScopedThreadBuilder>::spawn<<rayon_core::ThreadPoolBuilder>::build_scoped<rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#0}, rustc_interface::util::run_in_thread_pool_with_globals<rustc_interface::interface::run_compiler<core::result::Result<(), rustc_span::ErrorGuaranteed>, rustc_driver_impl::run_compiler::{closure#0}>::{closure#0}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#3}::{closure#0}::{closure#1}, core::result::Result<(), rustc_span::ErrorGuaranteed>>::{closure#0}::{closure#0}::{closure#0}, ()>::{closure#0} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#38 0x00007f87b846af58 in <<std::thread::Builder>::spawn_unchecked_<alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output = ()> + core::marker::Send>, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0} () from /home/andjo403/.rustup/toolchains/stage1/lib/librustc_driver-70ddb84e8f7ce707.so rust-lang#39 0x00007f87b7898e85 in std::sys::unix::thread::Thread::new::thread_start () from /home/andjo403/.rustup/toolchains/stage1/lib/libstd-d570b0650d35d951.so rust-lang#40 0x00007f87b7615609 in start_thread (arg=<optimized out>) at pthread_create.c:477 rust-lang#41 0x00007f87b7755133 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:95 ``` fixes rust-lang#118205 fixes rust-lang#117759 from the latest logs it is the same query map as in rust-lang#118205 fixes rust-lang#118529 fixes rust-lang#117784 cc rust-lang#118206 r? `@SparrowLii`
GuillaumeGomez
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May 18, 2024
Some minor (English only) heroics are performed to print error messages like "5th rule of macro `m` is never used". The form "rule #5 of macro `m` is never used" is just as good and much simpler to implement.
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r? @Dylan-DPC