Tracking issue for RFC 2565, "Attributes in formal function parameter position" #60406

Centril · 2019-04-30T10:09:24Z

This is a tracking issue for the RFC "Attributes in formal function parameter position" (rust-lang/rfcs#2565).

Steps:

Implement the RFC – Allow attributes in formal function parameters #60669
Adjust documentation (Add reference for attributes in function parameters reference#657)
Stabilization PR (Stabilize param_attrs in Rust 1.39.0 #64010)
Fixing Lint attributes on function args have no effect #61238

Unresolved questions:

None.

This issue has been assigned to @c410-f3r via this comment.

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

c410-f3r · 2019-05-01T14:59:56Z

Wow! I've always wanted to contribute to Rustc itself and this is a nice opportunity. I will try to implement this feature with some mentoring.

Centril · 2019-05-02T01:38:17Z

@petrochenkov You are familiar with most of this, right? Could you perhaps write up some instructions?

Allow attributes in formal function parameters Implements #60406. This is my first contribution to the compiler and since this is a large and complex project, I am not fully aware of the consequences of the changes I have made. **TODO** - [x] Forbid some built-in attributes. - [x] Expand cfg/cfg_attr

Centril · 2019-06-12T14:27:12Z

Partial implementation completed as of 2019-06-12. Implementation was done in #60669 by @c410-f3r and the PR was reviewed by @petrochenkov and @Centril.

#61238 still needs to be done for a full implementation.

Chapter for `param_attrs` Most the information was taken from the RFC. cc rust-lang#60406

Lint attributes on function arguments Fixes rust-lang#61238. cc rust-lang#60406

Centril · 2019-07-29T00:19:18Z

#61238 was fixed on the 2019-07-29 in #61856. The PR was written by @c410-f3r and reviewed by @matthewjasper, @petrochenkov, and @oli-obk.

The RFC is now fully implemented.

Setting the earliest date for a stabilization report to 6 weeks from now which is on 2019-09-09.

@petrochenkov

…twco Pretty print attributes in `print_arg` Fixes rust-lang#63210. cc rust-lang#60406 r? @petrochenkov

Centril · 2019-08-03T07:58:38Z

A bug #63210 was filed on 2019-08-02 wherein the attributes on formal parameters would not be passed to macros. The issue was forgetting to call the relevant method in fn print_arg in the pretty printer. In #63212, written by @Centril on 2019-08-02 and reviewed by @davidtwco, the issue aforementioned was fixed.

theduke · 2019-08-18T12:16:14Z

Would love for this feature to hit stable in 1.39.

With a stabilization report at the beginning of September, that should be possible, @Centril ?
(Assuming the documentation is taken care of in time)

Centril · 2019-08-18T12:21:50Z

Seems plausible; 1.39 branches on the 26th; - 10 days for FCP - some time to write a report.

c410-f3r · 2019-08-18T21:12:15Z

If possible, I would like to write the report, as well as the stabilization PR and remaining documentation

Centril · 2019-08-18T21:17:03Z

@c410-f3r Sure. Here's a report you can use as a template: #61682 (comment). I'd like to review and vet the report first however before it is published on a stabilization PR.

nikomatsakis · 2019-08-29T18:50:25Z

@rustbot assign @c410-f3r

Centril · 2019-08-29T19:27:01Z

We discussed this on the language team meeting and found that we should indeed move ahead with stabilizing it.

Centril · 2019-08-29T23:45:30Z

The stabilization proposal is up: #64010.

@nikomatsakis

… r=nikomatsakis Harden `param_attrs` test wrt. usage of a proc macro `#[attr]` The `param-attrs-builtin-attrs.rs` test file uses the `#[test]` attribute which should cover this but `#[test]` isn't a proc macro attribute so we add another test to be on the safe side. This intends to address rust-lang#64010 (comment). r? @nikomatsakis cc @c410-f3r @petrochenkov cc rust-lang#60406

@nikomatsakis

… r=nikomatsakis Harden `param_attrs` test wrt. usage of a proc macro `#[attr]` The `param-attrs-builtin-attrs.rs` test file uses the `#[test]` attribute which should cover this but `#[test]` isn't a proc macro attribute so we add another test to be on the safe side. This intends to address rust-lang#64010 (comment). r? @nikomatsakis cc @c410-f3r @petrochenkov cc rust-lang#60406

@Robbepop

Stabilize `param_attrs` in Rust 1.39.0 # Stabilization proposal I propose that we stabilize `#![feature(param_attrs)]`. Tracking issue: #60406 Version: 1.39 (2019-09-26 => beta, 2019-11-07 => stable). ## What is stabilized It is now possible to add outer attributes like `#[cfg(..)]` on formal parameters of functions, closures, and function pointer types. For example: ```rust fn len( #[cfg(windows)] slice: &[u16], #[cfg(not(windows))] slice: &[u8], ) -> usize { slice.len() } ``` ## What isn't stabilized * Documentation comments like `/// Doc` on parameters. * Code expansion of a user-defined `#[proc_macro_attribute]` macro used on parameters. * Built-in attributes other than `cfg`, `cfg_attr`, `allow`, `warn`, `deny`, and `forbid`. Currently, only the lints `unused_variables` and `unused_mut` have effect and may be controlled on parameters. ## Motivation The chief motivations for stabilizing `param_attrs` include: * Finer conditional compilation with `#[cfg(..)]` and linting control of variables. * Richer macro DSLs created by users. * External tools and compiler internals can take advantage of the additional information that the parameters provide. For more examples, see the [RFC][rfc motivation]. ## Reference guide In the grammar of function and function pointer, the grammar of variadic tails (`...`) and parameters are changed respectively from: ```rust FnParam = { pat:Pat ":" }? ty:Type; VaradicTail = "..."; ``` into: ```rust FnParam = OuterAttr* { pat:Pat ":" }? ty:Type; VaradicTail = OuterAttr* "..."; ``` The grammar of a closure parameter is changed from: ```rust ClosureParam = pat:Pat { ":" ty:Type }?; ``` into: ```rust ClosureParam = OuterAttr* pat:Pat { ":" ty:Type }?; ``` More generally, where there's a list of formal (value) parameters separated or terminated by `,` and delimited by `(` and `)`. Each parameter in that list may optionally be prefixed by `OuterAttr+`. Note that in all cases, `OuterAttr*` applies to the whole parameter and not just the pattern. This distinction matters in pretty printing and in turn for macros. ## History * On 2018-10-15, @Robbepop proposes [RFC 2565][rfc], "Attributes in formal function parameter position". * On 2019-04-30, [RFC 2565][rfc] is merged and the tracking issue is made. * On 2019-06-12, a partial implementation was completed. The implementation was done in [#60669][60669] by @c410-f3r and the PR was reviewed by @petrochenkov and @Centril. * On 2019-07-29, [#61238][61238] was fixed in [#61856][61856]. The issue fixed was that lint attributes on function args had no effect. The PR was written by @c410-f3r and reviewed by @matthewjasper, @petrochenkov, and @oli-obk. * On 2019-08-02, a bug [#63210][63210] was filed wherein the attributes on formal parameters would not be passed to macros. The issue was about forgetting to call the relevant method in `fn print_arg` in the pretty printer. In [#63212][63212], written by @Centril on 2019-08-02 and reviewed by @davidtwco, the issue aforementioned was fixed. * This PR stabilizes `param_attrs`. ## Tests * [On Rust 2018, attributes aren't permitted on function parameters without a pattern in trait definitions.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-2018.rs) * [All attributes that should be allowed. This includes `cfg`, `cfg_attr`, and lints check attributes.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-allowed.rs) * [Built-in attributes, which should be forbidden, e.g., `#[test]`, are.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs) * [`cfg` and `cfg_attr` are properly evaluated.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-cfg.rs) * [`unused_mut`](https://github.com/rust-lang/rust/blob/46f405ec4d7c6bf16fc2eaafe7541019f1da2996/src/test/ui/rfc-2565-param-attrs/param-attrs-cfg.rs) and [`unused_variables`](https://github.com/rust-lang/rust/blob/master/src/test/ui/lint/lint-unused-variables.rs) are correctly applied to parameter patterns. * [Pretty printing takes formal parameter attributes into account.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-pretty.rs) ## Possible future work * Custom attributes inside function parameters aren't currently supported but it is something being worked on internally. * Since documentation comments are syntactic sugar for `#[doc(...)]`, it is possible to allow literal `/// Foo` comments on function parameters. [rfc motivation]: https://github.com/rust-lang/rfcs/blob/master/text/2565-formal-function-parameter-attributes.md#motivation [rfc]: rust-lang/rfcs#2565 [60669]: #60669 [61856]: #61856 [63210]: #63210 [61238]: #61238 [63212]: #63212 This report is a collaborative work with @Centril.

@Robbepop

Stabilize `param_attrs` in Rust 1.39.0 # Stabilization proposal I propose that we stabilize `#![feature(param_attrs)]`. Tracking issue: rust-lang#60406 Version: 1.39 (2019-09-26 => beta, 2019-11-07 => stable). ## What is stabilized It is now possible to add outer attributes like `#[cfg(..)]` on formal parameters of functions, closures, and function pointer types. For example: ```rust fn len( #[cfg(windows)] slice: &[u16], #[cfg(not(windows))] slice: &[u8], ) -> usize { slice.len() } ``` ## What isn't stabilized * Documentation comments like `/// Doc` on parameters. * Code expansion of a user-defined `#[proc_macro_attribute]` macro used on parameters. * Built-in attributes other than `cfg`, `cfg_attr`, `allow`, `warn`, `deny`, and `forbid`. Currently, only the lints `unused_variables` and `unused_mut` have effect and may be controlled on parameters. ## Motivation The chief motivations for stabilizing `param_attrs` include: * Finer conditional compilation with `#[cfg(..)]` and linting control of variables. * Richer macro DSLs created by users. * External tools and compiler internals can take advantage of the additional information that the parameters provide. For more examples, see the [RFC][rfc motivation]. ## Reference guide In the grammar of function and function pointer, the grammar of variadic tails (`...`) and parameters are changed respectively from: ```rust FnParam = { pat:Pat ":" }? ty:Type; VaradicTail = "..."; ``` into: ```rust FnParam = OuterAttr* { pat:Pat ":" }? ty:Type; VaradicTail = OuterAttr* "..."; ``` The grammar of a closure parameter is changed from: ```rust ClosureParam = pat:Pat { ":" ty:Type }?; ``` into: ```rust ClosureParam = OuterAttr* pat:Pat { ":" ty:Type }?; ``` More generally, where there's a list of formal (value) parameters separated or terminated by `,` and delimited by `(` and `)`. Each parameter in that list may optionally be prefixed by `OuterAttr+`. Note that in all cases, `OuterAttr*` applies to the whole parameter and not just the pattern. This distinction matters in pretty printing and in turn for macros. ## History * On 2018-10-15, @Robbepop proposes [RFC 2565][rfc], "Attributes in formal function parameter position". * On 2019-04-30, [RFC 2565][rfc] is merged and the tracking issue is made. * On 2019-06-12, a partial implementation was completed. The implementation was done in [rust-lang#60669][60669] by @c410-f3r and the PR was reviewed by @petrochenkov and @Centril. * On 2019-07-29, [rust-lang#61238][61238] was fixed in [rust-lang#61856][61856]. The issue fixed was that lint attributes on function args had no effect. The PR was written by @c410-f3r and reviewed by @matthewjasper, @petrochenkov, and @oli-obk. * On 2019-08-02, a bug [rust-lang#63210][63210] was filed wherein the attributes on formal parameters would not be passed to macros. The issue was about forgetting to call the relevant method in `fn print_arg` in the pretty printer. In [rust-lang#63212][63212], written by @Centril on 2019-08-02 and reviewed by @davidtwco, the issue aforementioned was fixed. * This PR stabilizes `param_attrs`. ## Tests * [On Rust 2018, attributes aren't permitted on function parameters without a pattern in trait definitions.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-2018.rs) * [All attributes that should be allowed. This includes `cfg`, `cfg_attr`, and lints check attributes.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-allowed.rs) * [Built-in attributes, which should be forbidden, e.g., `#[test]`, are.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs) * [`cfg` and `cfg_attr` are properly evaluated.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-cfg.rs) * [`unused_mut`](https://github.com/rust-lang/rust/blob/46f405ec4d7c6bf16fc2eaafe7541019f1da2996/src/test/ui/rfc-2565-param-attrs/param-attrs-cfg.rs) and [`unused_variables`](https://github.com/rust-lang/rust/blob/master/src/test/ui/lint/lint-unused-variables.rs) are correctly applied to parameter patterns. * [Pretty printing takes formal parameter attributes into account.](https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-pretty.rs) ## Possible future work * Custom attributes inside function parameters aren't currently supported but it is something being worked on internally. * Since documentation comments are syntactic sugar for `#[doc(...)]`, it is possible to allow literal `/// Foo` comments on function parameters. [rfc motivation]: https://github.com/rust-lang/rfcs/blob/master/text/2565-formal-function-parameter-attributes.md#motivation [rfc]: rust-lang/rfcs#2565 [60669]: rust-lang#60669 [61856]: rust-lang#61856 [63210]: rust-lang#63210 [61238]: rust-lang#61238 [63212]: rust-lang#63212 This report is a collaborative work with @Centril.

Fixes #55 This isn't complete yet. This patch currently removes support for having descriptions on field arguments. That is because getting those to work [requires funky stuff][funky] in the juniper proc macro invocation. While it could totally be made to work I would rather wait since it requires a bit of refactoring and since it should work seamlessly once [RFC 2564](rust-lang/rust#60406) is stable, which seems to happen in 1.39. [funky]: https://docs.rs/juniper_codegen/0.13.2/juniper_codegen/attr.object.html#customization-documentation-renaming-

Centril · 2019-09-21T18:15:51Z

Stabilization is done; documentation will be done in the reference. Closing as nothing remains to do.

c410-f3r · 2019-09-21T19:13:28Z

It was a long journey and I would like to thank @Robbepop for the RFC and all the PR reviewers, specially @petrochenkov and @Centril.

theduke · 2019-09-21T19:18:13Z

Also thanks from me, this is much needed for improving proc macro ergonomics in juniper

Centril added B-RFC-approved Blocker: Approved by a merged RFC but not yet implemented. T-lang Relevant to the language team C-tracking-issue Category: An issue tracking the progress of sth. like the implementation of an RFC labels Apr 30, 2019

Centril mentioned this issue Apr 30, 2019

RFC: Attributes in formal function parameter position rust-lang/rfcs#2565

Merged

theduke mentioned this issue May 7, 2019

Graphql object proc macro graphql-rust/juniper#333

Merged

Centril mentioned this issue May 9, 2019

Allow attributes in formal function parameters #60669

Merged

2 tasks

Centril mentioned this issue May 27, 2019

Lint attributes on function args have no effect #61238

Closed

Centril added B-RFC-implemented Blocker: Approved by a merged RFC and implemented but not stabilized. B-unstable Blocker: Implemented in the nightly compiler and unstable. labels Jun 12, 2019

c410-f3r mentioned this issue Jun 15, 2019

Lint attributes on function arguments #61856

Merged

Centril mentioned this issue Jul 1, 2019

#[proptest] Attribute Macro proptest-rs/proptest#153

Open

la10736 mentioned this issue Jul 2, 2019

Use just [rstest] to generate test. la10736/rstest#42

Closed

c410-f3r mentioned this issue Jul 15, 2019

Chapter for param_attrs #62683

Merged

Mark-Simulacrum added a commit to Mark-Simulacrum/rust that referenced this issue Jul 16, 2019

Rollup merge of rust-lang#62683 - c410-f3r:fn-attrs-doc, r=Centril

c9be624

Chapter for `param_attrs` Most the information was taken from the RFC. cc rust-lang#60406

Centril added a commit to Centril/rust that referenced this issue Jul 28, 2019

Rollup merge of rust-lang#61856 - c410-f3r:attrs-fn, r=matthewjasper

a4cd2ec

Lint attributes on function arguments Fixes rust-lang#61238. cc rust-lang#60406

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Centril added the F-param_attrs `#![feature(param_attrs)]` label Aug 2, 2019

This was referenced Aug 2, 2019

Formal parameter attributes won't be passed into proc-macro #63210

Closed

Pretty print attributes in print_arg #63212

Merged

Centril added a commit to Centril/rust that referenced this issue Aug 2, 2019

Rollup merge of rust-lang#63212 - Centril:param-attrs-pretty, r=david…

f6d8977

…twco Pretty print attributes in `print_arg` Fixes rust-lang#63210. cc rust-lang#60406 r? @petrochenkov

Centril mentioned this issue Aug 5, 2019

Function arguments in trait functions are "unused" if unused in default impl #55070

Closed

c410-f3r mentioned this issue Aug 22, 2019

Stabilize param_attrs in Rust 1.39.0 c410-f3r/rust#1

Closed

Centril added the I-nominated label Aug 26, 2019

rustbot self-assigned this Aug 29, 2019

theduke mentioned this issue Aug 29, 2019

Refactor object proc macro attributes to support parameter attributes graphql-rust/juniper#421

Closed

c410-f3r mentioned this issue Aug 29, 2019

Stabilize param_attrs in Rust 1.39.0 #64010

Merged

Centril removed the I-nominated label Aug 29, 2019

Centril mentioned this issue Aug 31, 2019

Harden param_attrs test wrt. usage of a proc macro #[attr] #64031

Merged

davidpdrsn mentioned this issue Sep 21, 2019

Remove use of deprecated juniper::graphql_object! davidpdrsn/juniper-from-schema#74

Closed

Centril closed this as completed Sep 21, 2019

davidpdrsn mentioned this issue Sep 21, 2019

Support descriptions with param_attrs on field arguments with proc-macro graphql-rust/juniper#428

Closed

Boscop mentioned this issue Jul 10, 2021

Switch to attribute-like macros xiaoniu-578fa6bff964d005/duang#2

Open

ambiguousname mentioned this issue Jul 3, 2024

Attributes for Param, SelfParam, and StructField types rust-diplomat/diplomat#521

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Tracking issue for RFC 2565, "Attributes in formal function parameter position" #60406

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