Rollup of 10 pull requests #120335

matthiaskrgr · 2024-01-25T07:39:46Z

Successful merges:

Add AsyncFn family of traits #119305 (Add AsyncFn family of traits)
Provide more context on recursive impl evaluation overflow #119389 (Provide more context on recursive impl evaluation overflow)
Remove track_errors entirely #119895 (Remove track_errors entirely)
Assert that a single scope is passed to for_scope #120230 (Assert that a single scope is passed to for_scope)
Remove --fatal-warnings on wasm targets #120278 (Remove --fatal-warnings on wasm targets)
coverage: Dismantle Instrumentor and flatten span refinement #120292 (coverage: Dismantle Instrumentor and flatten span refinement)
On E0308 involving dyn Trait, mention trait objects #120315 (On E0308 involving dyn Trait, mention trait objects)
pattern_analysis: Let ctor_sub_tys return any Iterator they want #120317 (pattern_analysis: Let ctor_sub_tys return any Iterator they want)
pattern_analysis: Reuse most of the DeconstructedPat Debug impl #120318 (pattern_analysis: Reuse most of the DeconstructedPat Debug impl)
rustc_data_structures: use either instead of itertools #120325 (rustc_data_structures: use either instead of itertools)

r? @ghost
@rustbot modify labels: rollup

When an associated type `Self::Assoc` is part of a `where` clause, we end up unable to evaluate the requirement and emit a E0275. We now point at the associated type if specified in the `impl`. If so, we also suggest using that type instead of `Self::Assoc`. Otherwise, we explain that these are not allowed. ``` error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _` --> $DIR/impl-wf-cycle-1.rs:15:1 | LL | / impl<T: Grault> Grault for (T,) LL | | LL | | where LL | | Self::A: Baz, LL | | Self::B: Fiz, | |_________________^ LL | { LL | type A = (); | ------ associated type `<(T,) as Grault>::A` is specified here | note: required for `(T,)` to implement `Grault` --> $DIR/impl-wf-cycle-1.rs:15:17 | LL | impl<T: Grault> Grault for (T,) | ^^^^^^ ^^^^ ... LL | Self::A: Baz, | --- unsatisfied trait bound introduced here = note: 1 redundant requirement hidden = note: required for `(T,)` to implement `Grault` help: associated type for the current `impl` cannot be restricted in `where` clauses, remove this bound | LL - Self::A: Baz, LL + , | ``` ``` error[E0275]: overflow evaluating the requirement `<T as B>::Type == <T as B>::Type` --> $DIR/impl-wf-cycle-3.rs:7:1 | LL | / impl<T> B for T LL | | where LL | | T: A<Self::Type>, | |_____________________^ LL | { LL | type Type = bool; | --------- associated type `<T as B>::Type` is specified here | note: required for `T` to implement `B` --> $DIR/impl-wf-cycle-3.rs:7:9 | LL | impl<T> B for T | ^ ^ LL | where LL | T: A<Self::Type>, | ------------- unsatisfied trait bound introduced here help: replace the associated type with the type specified in this `impl` | LL | T: A<bool>, | ~~~~ ``` ``` error[E0275]: overflow evaluating the requirement `<T as Filter>::ToMatch == <T as Filter>::ToMatch` --> $DIR/impl-wf-cycle-4.rs:5:1 | LL | / impl<T> Filter for T LL | | where LL | | T: Fn(Self::ToMatch), | |_________________________^ | note: required for `T` to implement `Filter` --> $DIR/impl-wf-cycle-4.rs:5:9 | LL | impl<T> Filter for T | ^^^^^^ ^ LL | where LL | T: Fn(Self::ToMatch), | ----------------- unsatisfied trait bound introduced here note: associated types for the current `impl` cannot be restricted in `where` clauses --> $DIR/impl-wf-cycle-4.rs:7:11 | LL | T: Fn(Self::ToMatch), | ^^^^^^^^^^^^^ ``` Fix rust-lang#116925

These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag.

Consolidating this code into flatter functions reduces the amount of pointer-chasing required to read and modify it.

Since we always clone and allocate the types somewhere else ourselves, no need to ask for `Cx` to do the allocation.

When encountering a type mismatch error involving `dyn Trait`, mention the existence of boxed trait objects if the other type involved implements `Trait`. Partially addresses rust-lang#102629.

…=oli-obk Add `AsyncFn` family of traits I'm proposing to add a new family of `async`hronous `Fn`-like traits to the standard library for experimentation purposes. ## Why do we need new traits? On the user side, it is useful to be able to express `AsyncFn` trait bounds natively via the parenthesized sugar syntax, i.e. `x: impl AsyncFn(&str) -> String` when experimenting with async-closure code. This also does not preclude `AsyncFn` becoming something else like a trait alias if a more fundamental desugaring (which can take many[^1] different[^2] forms) comes around. I think we should be able to play around with `AsyncFn` well before that, though. I'm also not proposing stabilization of these trait names any time soon (we may even want to instead express them via new syntax, like `async Fn() -> ..`), but I also don't think we need to introduce an obtuse bikeshedding name, since `AsyncFn` just makes sense. ## The lending problem: why not add a more fundamental primitive of `LendingFn`/`LendingFnMut`? Firstly, for `async` closures to be as flexible as possible, they must be allowed to return futures which borrow from the async closure's captures. This can be done by introducing `LendingFn`/`LendingFnMut` traits, or (equivalently) by adding a new generic associated type to `FnMut` which allows the return type to capture lifetimes from the `&mut self` argument of the trait. This was proposed in one of [Niko's blog posts](https://smallcultfollowing.com/babysteps/blog/2023/05/09/giving-lending-and-async-closures/). Upon further experimentation, for the purposes of closure type- and borrow-checking, I've come to the conclusion that it's significantly harder to teach the compiler how to handle *general* lending closures which may borrow from their captures. This is, because unlike `Fn`/`FnMut`, the `LendingFn`/`LendingFnMut` traits don't form a simple "inheritance" hierarchy whose top trait is `FnOnce`. ```mermaid flowchart LR Fn FnMut FnOnce LendingFn LendingFnMut Fn -- isa --> FnMut FnMut -- isa --> FnOnce LendingFn -- isa --> LendingFnMut Fn -- isa --> LendingFn FnMut -- isa --> LendingFnMut ``` For example: ``` fn main() { let s = String::from("hello, world"); let f = move || &s; let x = f(); // This borrows `f` for some lifetime `'1` and returns `&'1 String`. ``` That trait hierarchy means that in general for "lending" closures, like `f` above, there's not really a meaningful return type for `<typeof(f) as FnOnce>::Output` -- it can't return `&'static str`, for example. ### Special-casing this problem: By splitting out these traits manually, and making sure that each trait has its own associated future type, we side-step the issue of having to answer the questions of a general `LendingFn`/`LendingFnMut` implementation, since the compiler knows how to generate built-in implementations for first-class constructs like async closures, including the required future types for the (by-move) `AsyncFnOnce` and (by-ref) `AsyncFnMut`/`AsyncFn` trait implementations. [^1]: For example, with trait transformers, we may eventually be able to write: `trait AsyncFn = async Fn;` [^2]: For example, via the introduction of a more fundamental "`LendingFn`" trait, plus a [special desugaring with augmented trait aliases](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Lending.20closures.20and.20Fn*.28.29.20-.3E.20impl.20Trait/near/408471480).

Provide more context on recursive `impl` evaluation overflow When an associated type `Self::Assoc` is part of a `where` clause, we end up unable to evaluate the requirement and emit a E0275. We now point at the associated type if specified in the `impl`. If so, we also suggest using that type instead of `Self::Assoc`. Otherwise, we explain that these are not allowed. ``` error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _` --> $DIR/impl-wf-cycle-1.rs:15:1 | LL | / impl<T: Grault> Grault for (T,) LL | | LL | | where LL | | Self::A: Baz, LL | | Self::B: Fiz, | |_________________^ LL | { LL | type A = (); | ------ associated type `<(T,) as Grault>::A` is specified here | note: required for `(T,)` to implement `Grault` --> $DIR/impl-wf-cycle-1.rs:15:17 | LL | impl<T: Grault> Grault for (T,) | ^^^^^^ ^^^^ ... LL | Self::A: Baz, | --- unsatisfied trait bound introduced here = note: 1 redundant requirement hidden = note: required for `(T,)` to implement `Grault` help: associated type for the current `impl` cannot be restricted in `where` clauses, remove this bound | LL - Self::A: Baz, | ``` ``` error[E0275]: overflow evaluating the requirement `<T as B>::Type == <T as B>::Type` --> $DIR/impl-wf-cycle-3.rs:7:1 | LL | / impl<T> B for T LL | | where LL | | T: A<Self::Type>, | |_____________________^ LL | { LL | type Type = bool; | --------- associated type `<T as B>::Type` is specified here | note: required for `T` to implement `B` --> $DIR/impl-wf-cycle-3.rs:7:9 | LL | impl<T> B for T | ^ ^ LL | where LL | T: A<Self::Type>, | ------------- unsatisfied trait bound introduced here help: replace the associated type with the type specified in this `impl` | LL | T: A<bool>, | ~~~~ ``` ``` error[E0275]: overflow evaluating the requirement `<T as Filter>::ToMatch == <T as Filter>::ToMatch` --> $DIR/impl-wf-cycle-4.rs:5:1 | LL | / impl<T> Filter for T LL | | where LL | | T: Fn(Self::ToMatch), | |_________________________^ | note: required for `T` to implement `Filter` --> $DIR/impl-wf-cycle-4.rs:5:9 | LL | impl<T> Filter for T | ^^^^^^ ^ LL | where LL | T: Fn(Self::ToMatch), | ----------------- unsatisfied trait bound introduced here note: associated types for the current `impl` cannot be restricted in `where` clauses --> $DIR/impl-wf-cycle-4.rs:7:11 | LL | T: Fn(Self::ToMatch), | ^^^^^^^^^^^^^ ``` Fix rust-lang#116925

…asper Remove `track_errors` entirely follow up to rust-lang#119869 r? `@matthewjasper` There are some diagnostic changes adding new diagnostics or not emitting some anymore. We can improve upon that in follow-up work imo.

…chaelwoerister Assert that a single scope is passed to `for_scope` Addresses rust-lang#118518 (comment) r? ``@michaelwoerister``

…sm, r=oli-obk Remove --fatal-warnings on wasm targets These were added with good intentions, but a recent change in LLVM 18 emits a warning while examining .rmeta sections in .rlib files. Since this flag is a nice-to-have and users can update their LLVM linker independently of rustc's LLVM version, we can just omit the flag. See [this comment on wasm targets' uses of `--fatal-warnings`](llvm/llvm-project#78658 (comment)).

coverage: Dismantle `Instrumentor` and flatten span refinement This is a combination of two refactorings that are unrelated, but would otherwise have a merge conflict. No functional changes, other than a small tweak to debug logging as part of rearranging some functions. Ignoring whitespace is highly recommended, since most of the modified lines have just been reindented. --- The first change is to dismantle `Instrumentor` into ordinary functions. This is one of those cases where encapsulating several values into a struct ultimately hurts more than it helps. With everything stored as local variables in one main function, and passed explicitly into helper functions, it's easier to see what is used where, and make changes as necessary. --- The second change is to flatten the functions for extracting/refining coverage spans. Consolidating this code into flatter functions reduces the amount of pointer-chasing required to read and modify it.

…iser On E0308 involving `dyn Trait`, mention trait objects When encountering a type mismatch error involving `dyn Trait`, mention the existence of boxed trait objects if the other type involved implements `Trait`. Fix rust-lang#102629.

…r=compiler-errors pattern_analysis: Let `ctor_sub_tys` return any Iterator they want I noticed that we always `.cloned()` and allocate the output of `TypeCx::ctor_sub_tys` now, so there was no need to force it to return a slice. `ExactSizeIterator` is not super important but saves some manual counting. r? `@compiler-errors`

…iler-errors pattern_analysis: Reuse most of the `DeconstructedPat` `Debug` impl The `DeconstructedPat: Debug` is best-effort because we'd need `tcx` to get things like field names etc. Since rust-analyzer has a similar constraint, this PR moves most the impl to be shared between the two. While I was at it I also fixed a nit in the `IntRange: Debug` impl. r? `@compiler-errors`

…rors rustc_data_structures: use either instead of itertools `itertools::Either` is a re-export from `either`, so we might as well use the source. This flattens the compiler build tree a little, but I don't really expect it to make much difference overall.

matthiaskrgr · 2024-01-25T07:39:58Z

@bors r+ rollup=never p=10

bors · 2024-01-25T07:40:01Z

📌 Commit 8c1ba59 has been approved by matthiaskrgr

It is now in the queue for this repository.

bors · 2024-01-25T09:20:26Z

⌛ Testing commit 8c1ba59 with merge 5bd5d21...

bors · 2024-01-25T11:17:16Z

☀️ Test successful - checks-actions
Approved by: matthiaskrgr
Pushing 5bd5d21 to master...

rust-timer · 2024-01-25T11:20:05Z

📌 Perf builds for each rolled up PR:

PR#	Message	Perf Build Sha
#119305	Add `AsyncFn` family of traits	`63f0a7ab790b955f3357990ea0c51d4104d8e596` (link)
#119389	Provide more context on recursive `impl` evaluation overflow	`271a91eae0f70ccf935e694f61986a1649291d99` (link)
#119895	Remove `track_errors` entirely	`b59ed7ba885756350a897224eb47a3d9cf1da52b` (link)
#120230	Assert that a single scope is passed to `for_scope`	`662b32b7be18d2206acf94d3869fa4c6c24b7cdc` (link)
#120278	Remove --fatal-warnings on wasm targets	`c47044b229b2ab0f603546a2863a9c540c2fdb29` (link)
#120292	coverage: Dismantle `Instrumentor` and flatten span refinem…	`30b22dcfec5c14a9c46d57c6e743954654f744e4` (link)
#120315	On E0308 involving `dyn Trait`, mention trait objects	`d9dd2b1c8c5acf9abef2c0e475b2a41f3587796b` (link)
#120317	pattern_analysis: Let `ctor_sub_tys` return any Iterator th…	`638bbbbc285a46b9f6a2a93fb653213d72779eb3` (link)
#120318	pattern_analysis: Reuse most of the `DeconstructedPat` `Deb…	`edc7e62c9abba02b4aeb11bb22e3121616506f83` (link)
#120325	rustc_data_structures: use either instead of itertools	`4349a1f8916c5e3b363e93bb34fd66a586f0479c` (link)

previous master: d93feccb35

In the case of a perf regression, run the following command for each PR you suspect might be the cause: @rust-timer build $SHA

rust-timer · 2024-01-25T12:33:04Z

Finished benchmarking commit (5bd5d21): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.3%, 0.8%]	9
Regressions ❌ (secondary)	0.7%	[0.6%, 0.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.7%, -0.7%]	1
All ❌✅ (primary)	0.4%	[0.3%, 0.8%]	9

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.0%]	1
Regressions ❌ (secondary)	3.4%	[1.9%, 5.3%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.0%	[-2.2%, -1.7%]	2
All ❌✅ (primary)	1.0%	[1.0%, 1.0%]	1

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.5%, 2.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	7

Bootstrap: 662.638s -> 664.45s (0.27%)
Artifact size: 308.19 MiB -> 308.12 MiB (-0.02%)

Kobzol · 2024-01-25T18:14:18Z

Looks like doc regressions in evaluate_obligation.

@rust-timer build 271a91e

(Testing #119389).

Kobzol · 2024-01-25T20:30:32Z

@rust-timer build b59ed7b

#119895

Kobzol · 2024-01-25T22:50:56Z

@rust-timer build 662b32b

#120230

Kobzol · 2024-01-26T08:32:44Z

@rust-timer build 63f0a7a

#119305

rust-timer · 2024-01-26T10:28:03Z

Finished benchmarking commit (63f0a7a): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.3%, 0.9%]	9
Regressions ❌ (secondary)	0.7%	[0.7%, 0.8%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.7%, -0.7%]	1
All ❌✅ (primary)	0.5%	[0.3%, 0.9%]	9

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.2%	[1.9%, 4.6%]	5
Improvements ✅ (primary)	-2.5%	[-2.5%, -2.5%]	1
Improvements ✅ (secondary)	-1.5%	[-1.9%, -1.3%]	3
All ❌✅ (primary)	-2.5%	[-2.5%, -2.5%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	7
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[0.0%, 0.0%]	7

Bootstrap: 662.638s -> 662.122s (-0.08%)
Artifact size: 308.19 MiB -> 308.16 MiB (-0.01%)

Kobzol · 2024-01-26T10:31:37Z

Looks like #119305 is the source of the doc regressions. I assume that it's just because a few new things were added to stdlib, and therefore we don't need to delve deeper into this @compiler-errors?

compiler-errors and others added 28 commits December 25, 2023 20:31

Add AsyncFn family of traits

0e6f7c6

We do not need impl_trait_in_assoc_ty

fde86e5

select AsyncFn traits during overloaded call op

17b4333

Account for trailing comma in removal suggestion

c85bb27

Account for single where bound being removed

29bdf9e

Remove track_errors entirely

db7cd57

coverage: Dismantle Instrumentor into ordinary functions

83ef18c

coverage: Flatten the functions for extracting/refining coverage spans

572d7e9

Consolidating this code into flatter functions reduces the amount of pointer-chasing required to read and modify it.

Assert that a single scope is passed to for_scope

64f590a

Correctly explain ensure_forwards_result_if_red

cc34dc2

Let ctor_sub_tys return any Iterator they want

e088016

Since we always clone and allocate the types somewhere else ourselves, no need to ask for `Cx` to do the allocation.

On E0308 involving dyn Trait, mention trait objects

d992d9c

When encountering a type mismatch error involving `dyn Trait`, mention the existence of boxed trait objects if the other type involved implements `Trait`. Partially addresses rust-lang#102629.

Account for expected dyn Trait found impl Trait

796814d

Most of the DeconstructedPat Debug impl is reusable

bdab213

Improve Range: Debug impl

354b45f

rustc_data_structures: use either instead of itertools

8f3af4c

Rollup merge of rust-lang#120230 - Urgau:for_scope-single-scope, r=mi…

55d5ea3

…chaelwoerister Assert that a single scope is passed to `for_scope` Addresses rust-lang#118518 (comment) r? ``@michaelwoerister``

rustbot added A-query-system Area: The rustc query system (https://rustc-dev-guide.rust-lang.org/query.html) S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 25, 2024

rustbot added the rollup A PR which is a rollup label Jan 25, 2024

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 25, 2024

bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 25, 2024

bors merged commit 5bd5d21 into rust-lang:master Jan 25, 2024
12 checks passed

rustbot added this to the 1.77.0 milestone Jan 25, 2024

This was referenced Jan 25, 2024

Replace DefineOpaqueTypes::No => DefineOpaqueTypes::Yes #117348

Closed

pattern_analysis: cleanup the contexts #120321

Merged

On E0277 be clearer about implicit Sized bounds on type params and assoc types #120323

Merged

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Rollup of 10 pull requests #120335

Rollup of 10 pull requests #120335

matthiaskrgr commented Jan 25, 2024

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Rollup of 10 pull requests #120335

Rollup of 10 pull requests #120335

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Kobzol commented Jan 26, 2024