Tracking issue for RFC 2383, "Lint Reasons RFC" #54503

Centril · 2018-09-23T13:12:47Z

This is a tracking issue for the RFC "Lint Reasons RFC" (rust-lang/rfcs#2383).

Steps:

Implement the RFC (cc @rust-lang/compiler -- can anyone write up mentoring instructions?)
- Implement reason = lint reasons (RFC 2383, part 1) #54683
- Implement #[expect(lint)] -- see Implement expect attribute from RFC 2383, "Lint Reasons RFC" #85549
Adjust documentation (see instructions on forge)
Stabilization PR (see instructions on forge)

Unresolved questions:

The use sites of the reason parameter.

The text was updated successfully, but these errors were encountered:

zackmdavis · 2018-09-24T05:02:24Z

I started looking at this tonight. (Briefly; I regret that my time is limited.)

The example output in the RFC puts a reason: line immediately below the top-level error: line, but from a consilience-with-the-existing-implementation perspective, I'm inclined to think it would make more sense to use an ordinary note: (just as the existing "#[level(lint)] on by default" messages and must-use rationales do).

The reason should probably be stored as a third field inside of LintSource::Node.

zackmdavis · 2018-09-30T02:00:15Z

PR for reason = is #54683.

Unresolved questions:

The use sites of the reason parameter.

@myrrlyn I'm not sure what "use sites" means in this context?

This is just for the `reason =` name-value meta-item; the `#[expect(lint)]` attribute also described in the RFC is a problem for another day. The place where we were directly calling `emit()` on a match block (whose arms returned a mutable reference to a diagnostic-builder) was admittedly cute, but no longer plausibly natural after adding the if-let to the end of the `LintSource::Node` arm. This regards rust-lang#54503.

zackmdavis · 2018-12-15T22:08:08Z

It's a little bit sad/awkward that reason comments are most useful in practice for allow (rather than warn, deny, or forbid, which authors are more likely to regard as self-explanatory), and yet allow is the only case for which the new reason = functionality doesn't actually do anything. 😿

(This observation prompted by my thought that we should be able to dogfood reason = in this repo now that that functionality is in the beta bootstrap compiler, but ag '//.*\n\w*#\[(warn|deny|forbid|allow)' --ignore tools --ignore test only turns up instances of allow.)

oli-obk · 2018-12-17T08:26:38Z

We could add a lint that suggests turning allow with reason into expect because $reasons

myrrlyn · 2019-07-08T15:22:08Z

I apologize for my absence on this issue.

I'm not sure what "use sites" means in this context?

My standing question was "how should the reason value be used in the diagnostic", and it appears that the simplest answer is the one you provided: "put it in a note item". I have no firm attachment to rendering it as reason: User text here, and if prior art exists for note: User text here, then that is perfectly fine.

JohnTitor · 2020-03-19T21:46:53Z

Here's the initial work of expect lint level: https://github.com/JohnTitor/rust/tree/lint-expect

The remaining thing is to trigger the expectation_missing lint but I have no idea how to implement. If someone could do, feel free to steal something from there. Or I'm happy to continue the work if someone could mentor me :)

xFrednet · 2021-05-20T17:52:00Z

Hello everyone,
I would like to work on the expect attribute and move this issue towards stabilization.

Is there someone here who could mentor me? My contributions so far have only focussed on Clippy. If not I would most likely ask on Zulip for help 🙃.

nikomatsakis · 2021-05-21T14:24:34Z

@xFrednet I would happily mentor you on this! Let me start by opening an issue dedicated to jus the implementaton, since I dislike using the tracking issue for that sort of thing. I'll assign it to you.

xFrednet · 2021-05-31T20:35:44Z

Issue #55112 is related to the implementation of the reason field. The current implementation apparently allows the usage of an attribute with only a reason #[allow(reason = "foo")]. Source:

// FIXME (#55112): issue unused-attributes lint if we thereby
// don't have any lint names (`#[level(reason = "foo")]`)

Noted as a FIXME in the LintsLevelBilder

Just to keep track that this also has to be fixed before stabilization.

PR: #94580

In Rust, it is possible to `allow` particular warnings (diagnostics, lints) locally, making the compiler ignore instances of a given warning within a given function, module, block, etc. It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C: #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-function" static void f(void) {} #pragma GCC diagnostic pop But way less verbose: #[allow(dead_code)] fn f() {} By that virtue, it makes it possible to comfortably enable more diagnostics by default (i.e. outside `W=` levels) that may have some false positives but that are otherwise quite useful to keep enabled to catch potential mistakes. The `#[expect(...)]` attribute [1] takes this further, and makes the compiler warn if the diagnostic was _not_ produced. For instance, the following will ensure that, when `f()` is called somewhere, we will have to remove the attribute: #[expect(dead_code)] fn f() {} If we do not, we get a warning from the compiler: warning: this lint expectation is unfulfilled --> x.rs:3:10 | 3 | #[expect(dead_code)] | ^^^^^^^^^ | = note: `#[warn(unfulfilled_lint_expectations)]` on by default This means that `expect`s do not get forgotten when they are not needed. See the next commit for more details, nuances on its usage and documentation on the feature. The attribute requires the `lint_reasons` [2] unstable feature, but it is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has already been useful to clean things up in this patch series, finding cases where the `allow`s should not have been there. Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s where possible. This feature was also an example of the ongoing collaboration between Rust and the kernel -- we tested it in the kernel early on and found an issue that was quickly resolved [3]. Cc: Fridtjof Stoldt <xfrednet@gmail.com> Cc: Urgau <urgau@numericable.fr> Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1] Link: rust-lang/rust#54503 [2] Link: rust-lang/rust#114557 [3] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Require rust 1.81 rust-analyzer doesn't build on 1.80 because we use `#[expect(lint)]`: ``` error[E0658]: the `#[expect]` attribute is an experimental feature --> crates/hir-expand/src/prettify_macro_expansion_.rs:11:1 | 11 | #[expect(deprecated)] | ^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #54503 <rust-lang/rust#54503> for more information ```

In Rust, it is possible to `allow` particular warnings (diagnostics, lints) locally, making the compiler ignore instances of a given warning within a given function, module, block, etc. It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C: #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-function" static void f(void) {} #pragma GCC diagnostic pop But way less verbose: #[allow(dead_code)] fn f() {} By that virtue, it makes it possible to comfortably enable more diagnostics by default (i.e. outside `W=` levels) that may have some false positives but that are otherwise quite useful to keep enabled to catch potential mistakes. The `#[expect(...)]` attribute [1] takes this further, and makes the compiler warn if the diagnostic was _not_ produced. For instance, the following will ensure that, when `f()` is called somewhere, we will have to remove the attribute: #[expect(dead_code)] fn f() {} If we do not, we get a warning from the compiler: warning: this lint expectation is unfulfilled --> x.rs:3:10 | 3 | #[expect(dead_code)] | ^^^^^^^^^ | = note: `#[warn(unfulfilled_lint_expectations)]` on by default This means that `expect`s do not get forgotten when they are not needed. See the next commit for more details, nuances on its usage and documentation on the feature. The attribute requires the `lint_reasons` [2] unstable feature, but it is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has already been useful to clean things up in this patch series, finding cases where the `allow`s should not have been there. Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s where possible. This feature was also an example of the ongoing collaboration between Rust and the kernel -- we tested it in the kernel early on and found an issue that was quickly resolved [3]. Cc: Fridtjof Stoldt <xfrednet@gmail.com> Cc: Urgau <urgau@numericable.fr> Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1] Link: rust-lang/rust#54503 [2] Link: rust-lang/rust#114557 [3] Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Tested-by: Gary Guo <gary@garyguo.net> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Require rust 1.81 rust-analyzer doesn't build on 1.80 because we use `#[expect(lint)]`: ``` error[E0658]: the `#[expect]` attribute is an experimental feature --> crates/hir-expand/src/prettify_macro_expansion_.rs:11:1 | 11 | #[expect(deprecated)] | ^^^^^^^^^^^^^^^^^^^^^ | = note: see issue rust-lang#54503 <rust-lang#54503> for more information ```

ismailarilik · 2024-10-29T06:22:51Z

Is there any attempt to make use of this awesome feature for existing allow statements? I think every allow needs a reason.

xFrednet · 2024-10-29T10:39:49Z

@ismailarilik Do you mean in rustc or in general?

External projects can use clippy::allow_attributes_without_reason to enforce the specification of reasons.

To add it to the style guide of rustc, it would probably require a proposal to the compiler-team

In Rust, it is possible to `allow` particular warnings (diagnostics, lints) locally, making the compiler ignore instances of a given warning within a given function, module, block, etc. It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C: #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-function" static void f(void) {} #pragma GCC diagnostic pop But way less verbose: #[allow(dead_code)] fn f() {} By that virtue, it makes it possible to comfortably enable more diagnostics by default (i.e. outside `W=` levels) that may have some false positives but that are otherwise quite useful to keep enabled to catch potential mistakes. The `#[expect(...)]` attribute [1] takes this further, and makes the compiler warn if the diagnostic was _not_ produced. For instance, the following will ensure that, when `f()` is called somewhere, we will have to remove the attribute: #[expect(dead_code)] fn f() {} If we do not, we get a warning from the compiler: warning: this lint expectation is unfulfilled --> x.rs:3:10 | 3 | #[expect(dead_code)] | ^^^^^^^^^ | = note: `#[warn(unfulfilled_lint_expectations)]` on by default This means that `expect`s do not get forgotten when they are not needed. See the next commit for more details, nuances on its usage and documentation on the feature. The attribute requires the `lint_reasons` [2] unstable feature, but it is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has already been useful to clean things up in this patch series, finding cases where the `allow`s should not have been there. Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s where possible. This feature was also an example of the ongoing collaboration between Rust and the kernel -- we tested it in the kernel early on and found an issue that was quickly resolved [3]. Cc: Fridtjof Stoldt <xfrednet@gmail.com> Cc: Urgau <urgau@numericable.fr> Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1] Link: rust-lang/rust#54503 [2] Link: rust-lang/rust#114557 [3] Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Tested-by: Gary Guo <gary@garyguo.net> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

In Rust, it is possible to `allow` particular warnings (diagnostics, lints) locally, making the compiler ignore instances of a given warning within a given function, module, block, etc. It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C: #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-function" static void f(void) {} #pragma GCC diagnostic pop But way less verbose: #[allow(dead_code)] fn f() {} By that virtue, it makes it possible to comfortably enable more diagnostics by default (i.e. outside `W=` levels) that may have some false positives but that are otherwise quite useful to keep enabled to catch potential mistakes. The `#[expect(...)]` attribute [1] takes this further, and makes the compiler warn if the diagnostic was _not_ produced. For instance, the following will ensure that, when `f()` is called somewhere, we will have to remove the attribute: #[expect(dead_code)] fn f() {} If we do not, we get a warning from the compiler: warning: this lint expectation is unfulfilled --> x.rs:3:10 | 3 | #[expect(dead_code)] | ^^^^^^^^^ | = note: `#[warn(unfulfilled_lint_expectations)]` on by default This means that `expect`s do not get forgotten when they are not needed. See the next commit for more details, nuances on its usage and documentation on the feature. The attribute requires the `lint_reasons` [2] unstable feature, but it is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has already been useful to clean things up in this patch series, finding cases where the `allow`s should not have been there. Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s where possible. This feature was also an example of the ongoing collaboration between Rust and the kernel -- we tested it in the kernel early on and found an issue that was quickly resolved [3]. Cc: Fridtjof Stoldt <xfrednet@gmail.com> Cc: Urgau <urgau@numericable.fr> Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1] Link: rust-lang/rust#54503 [2] Link: rust-lang/rust#114557 [3] Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Tested-by: Gary Guo <gary@garyguo.net> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org> (cherry picked from commit 1f9ed172545687e5c04c77490a45896be6d2e459) [pinned_init: sync ui tests with new expanded code. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

In Rust, it is possible to `allow` particular warnings (diagnostics, lints) locally, making the compiler ignore instances of a given warning within a given function, module, block, etc. It is similar to `#pragma GCC diagnostic push` + `ignored` + `pop` in C: #pragma GCC diagnostic push #pragma GCC diagnostic ignored "-Wunused-function" static void f(void) {} #pragma GCC diagnostic pop But way less verbose: #[allow(dead_code)] fn f() {} By that virtue, it makes it possible to comfortably enable more diagnostics by default (i.e. outside `W=` levels) that may have some false positives but that are otherwise quite useful to keep enabled to catch potential mistakes. The `#[expect(...)]` attribute [1] takes this further, and makes the compiler warn if the diagnostic was _not_ produced. For instance, the following will ensure that, when `f()` is called somewhere, we will have to remove the attribute: #[expect(dead_code)] fn f() {} If we do not, we get a warning from the compiler: warning: this lint expectation is unfulfilled --> x.rs:3:10 | 3 | #[expect(dead_code)] | ^^^^^^^^^ | = note: `#[warn(unfulfilled_lint_expectations)]` on by default This means that `expect`s do not get forgotten when they are not needed. See the next commit for more details, nuances on its usage and documentation on the feature. The attribute requires the `lint_reasons` [2] unstable feature, but it is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has already been useful to clean things up in this patch series, finding cases where the `allow`s should not have been there. Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s where possible. This feature was also an example of the ongoing collaboration between Rust and the kernel -- we tested it in the kernel early on and found an issue that was quickly resolved [3]. Cc: Fridtjof Stoldt <xfrednet@gmail.com> Cc: Urgau <urgau@numericable.fr> Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1] Link: rust-lang/rust#54503 [2] Link: rust-lang/rust#114557 [3] Reviewed-by: Alice Ryhl <aliceryhl@google.com> Reviewed-by: Trevor Gross <tmgross@umich.edu> Tested-by: Gary Guo <gary@garyguo.net> Reviewed-by: Gary Guo <gary@garyguo.net> Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

This increases MSRV since ruzstd 0.8 uses `#[expect]` attribute stabilized in Rust 1.81 and exclusive range patterns stabilized in Rust 1.80. ``` error[E0658]: the `#[expect]` attribute is an experimental feature --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ruzstd-0.8.0/src/decoding/frame.rs:116:5 | 116 | #[expect(dead_code)] | ^^^^^^^^^^^^^^^^^^^^ | = note: see issue #54503 <rust-lang/rust#54503> for more information error[E0658]: exclusive range pattern syntax is experimental --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ruzstd-0.8.0/src/encoding/blocks/compressed.rs:209:9 | 209 | 0..6 => (0b00u8, 10), | ^^^^ | = note: see issue #37854 <rust-lang/rust#37854> for more information error[E0658]: exclusive range pattern syntax is experimental --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ruzstd-0.8.0/src/encoding/blocks/compressed.rs:210:9 | 210 | 6..1024 => (0b01, 10), | ^^^^^^^ | = note: see issue #37854 <rust-lang/rust#37854> for more information error[E0658]: exclusive range pattern syntax is experimental --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ruzstd-0.8.0/src/encoding/blocks/compressed.rs:211:9 | 211 | 1024..16384 => (0b10, 14), | ^^^^^^^^^^^ | = note: see issue #37854 <rust-lang/rust#37854> for more information error[E0658]: exclusive range pattern syntax is experimental --> /home/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/ruzstd-0.8.0/src/encoding/blocks/compressed.rs:212:9 | 212 | 16384..262144 => (0b11, 18), | ^^^^^^^^^^^^^ | = note: see issue #37854 <rust-lang/rust#37854> for more information ```

Centril added B-RFC-approved Blocker: Approved by a merged RFC but not yet implemented. T-lang Relevant to the language team, which will review and decide on the PR/issue. C-tracking-issue Category: An issue tracking the progress of sth. like the implementation of an RFC labels Sep 23, 2018

Centril mentioned this issue Sep 23, 2018

Lint Reasons RFC rust-lang/rfcs#2383

Merged

flip1995 mentioned this issue Oct 7, 2019

Lint error when needlessly supressing a lint rust-lang/rust-clippy#4636

Closed

jonas-schievink added the A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. label Jan 31, 2020

oli-obk mentioned this issue Sep 26, 2020

Remove unused #[allow(...)] statements from compiler/ #77211

Merged

flip1995 mentioned this issue Feb 28, 2021

[Roadmap] Lint groups rust-lang/rust-clippy#6626

Open

7 tasks

nikomatsakis mentioned this issue May 11, 2021

Allow unused variables with todo! #79850

Closed

nikomatsakis mentioned this issue May 21, 2021

Implement expect attribute from RFC 2383, "Lint Reasons RFC" #85549

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9 tasks

xFrednet mentioned this issue Jun 5, 2021

Adding the expect attribute (RFC 2383) #86024

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4 tasks

xFrednet mentioned this issue Aug 7, 2021

Implementation of the expect attribute (RFC 2383) #87835

Merged

xFrednet mentioned this issue Nov 4, 2021

lint unused (clippy) allow attributes rust-lang/rust-clippy#3122

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ojeda mentioned this issue Nov 18, 2024

Rust unstable features needed for the kernel Rust-for-Linux/linux#2

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89 tasks

fmease added A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. and removed A-lints Area: Lints (warnings about flaws in source code) such as unused_mut. labels Dec 21, 2024

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Tracking issue for RFC 2383, "Lint Reasons RFC" #54503

Tracking issue for RFC 2383, "Lint Reasons RFC" #54503

Centril commented Sep 23, 2018 •

edited by xFrednet

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oli-obk commented Dec 17, 2018

myrrlyn commented Jul 8, 2019

JohnTitor commented Mar 19, 2020

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xFrednet commented May 31, 2021 •

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ismailarilik commented Oct 29, 2024

xFrednet commented Oct 29, 2024

Tracking issue for RFC 2383, "Lint Reasons RFC" #54503

Tracking issue for RFC 2383, "Lint Reasons RFC" #54503

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Centril commented Sep 23, 2018 • edited by xFrednet Loading

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