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Stabilize param_attrs
in Rust 1.39.0
#64010
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r? @Centril |
Dear language team and the community at large. The above report gives an overview of the @rfcbot merge |
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Team member @Centril has proposed to merge this. The next step is review by the rest of the tagged team members: Concerns:
Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
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r=me on the code changes itself when FCP completes.
Been waiting for this 🎉
How does that work? Was it a deliberate decision somewhere in the code or a coincidental result of the implementation? I'm just asking to find out if there's something we should be aware of with tool lints in Clippy. |
Question for @Centril and @c410-f3r -- You mention that procedural macros are not stabilized. Is there a test showing what happens when a procedural macro is applied? I presume that it generates a feature gate? Or is it considered an error? Similarly, is there a test for lints that are intended to be disallowed? |
(Also, I should add, thanks for all your work on this. ❤️ ) |
According to the RFC, this reduced number of allowed lint was initially proposed to be part of a minimum viable product. Nevertheless, more lints can be added in future releases. Currently, the compiler shows the |
https://github.com/rust-lang/rust/blob/master/src/test/ui/rfc-2565-param-attrs/param-attrs-builtin-attrs.rs sorta addresses this by using
The RFC does not specify a specific list of lints that should or should not be allowed but the two lints that are tested and accounted for seemed the most important. We'd need to do a deeper audit of all the lints to see which others could be relevant and that's probably not worth the time at the moment. |
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.
💥 Test timed out |
@bors retry |
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.
Rollup of 9 pull requests Successful merges: - #64010 (Stabilize `param_attrs` in Rust 1.39.0) - #64136 (Document From trait for LhsExpr in parser) - #64342 (factor out pluralisation remains after #64280) - #64347 (Add long error explanation for E0312) - #64621 (Add Compatibility Notes to RELEASES.md for 1.38.0) - #64632 (remove the extra comma after the match arm) - #64640 (No home directory on vxWorks) - #64641 (Exempt extern "Rust" from improper_ctypes) - #64642 (Fix the span used to suggest avoiding for-loop moves) Failed merges: r? @ghost
Pkgsrc changes: * Remove patch which no longer applies (but what about RPATH?) * Adapt a few patches to changed files upstream. Upstream changes: Version 1.39.0 (2019-11-07) =========================== Language -------- - [You can now create `async` functions and blocks with `async fn`, `async move {}`, and `async {}` respectively, and you can now call `.await` on async expressions.][63209] - [You can now use certain attributes on function, closure, and function pointer parameters.][64010] These attributes include `cfg`, `cfg_attr`, `allow`, `warn`, `deny`, `forbid` as well as inert helper attributes used by procedural macro attributes applied to items. e.g. ```rust fn len( #[cfg(windows)] slice: &[u16], #[cfg(not(windows))] slice: &[u8], ) -> usize { slice.len() } ``` - [You can now take shared references to bind-by-move patterns in the `if` guards of `match` arms.][63118] e.g. ```rust fn main() { let array: Box<[u8; 4]> = Box::new([1, 2, 3, 4]); match array { nums // ---- `nums` is bound by move. if nums.iter().sum::<u8>() == 10 // ^------ `.iter()` implicitly takes a reference to `nums`. => { drop(nums); // ----------- Legal as `nums` was bound by move and so we have ownership. } _ => unreachable!(), } } ``` Compiler -------- - [Added tier 3\* support for the `i686-unknown-uefi` target.][64334] - [Added tier 3 support for the `sparc64-unknown-openbsd` target.][63595] - [rustc will now trim code snippets in diagnostics to fit in your terminal.] [63402] **Note** Cargo currently doesn't use this feature. Refer to [cargo#7315][cargo/7315] to track this feature's progress. - [You can now pass `--show-output` argument to test binaries to print the output of successful tests.][62600] \* Refer to Rust's [platform support page][forge-platform-support] for more information on Rust's tiered platform support. Libraries --------- - [`Vec::new` and `String::new` are now `const` functions.][64028] - [`LinkedList::new` is now a `const` function.][63684] - [`str::len`, `[T]::len` and `str::as_bytes` are now `const` functions.][63770] - [The `abs`, `wrapping_abs`, and `overflowing_abs` numeric functions are now `const`.][63786] Stabilized APIs --------------- - [`Pin::into_inner`] - [`Instant::checked_duration_since`] - [`Instant::saturating_duration_since`] Cargo ----- - [You can now publish git dependencies if supplied with a `version`.] [cargo/7237] - [The `--all` flag has been renamed to `--workspace`.][cargo/7241] Using `--all` is now deprecated. Misc ---- - [You can now pass `-Clinker` to rustdoc to control the linker used for compiling doctests.][63834] Compatibility Notes ------------------- - [Code that was previously accepted by the old borrow checker, but rejected by the NLL borrow checker is now a hard error in Rust 2018.][63565] This was previously a warning, and will also become a hard error in the Rust 2015 edition in the 1.40.0 release. - [`rustdoc` now requires `rustc` to be installed and in the same directory to run tests.][63827] This should improve performance when running a large amount of doctests. - [The `try!` macro will now issue a deprecation warning.][62672] It is recommended to use the `?` operator instead. - [`asinh(-0.0)` now correctly returns `-0.0`.][63698] Previously this returned `0.0`. [62600]: rust-lang/rust#62600 [62672]: rust-lang/rust#62672 [63118]: rust-lang/rust#63118 [63209]: rust-lang/rust#63209 [63402]: rust-lang/rust#63402 [63565]: rust-lang/rust#63565 [63595]: rust-lang/rust#63595 [63684]: rust-lang/rust#63684 [63698]: rust-lang/rust#63698 [63770]: rust-lang/rust#63770 [63786]: rust-lang/rust#63786 [63827]: rust-lang/rust#63827 [63834]: rust-lang/rust#63834 [63927]: rust-lang/rust#63927 [63933]: rust-lang/rust#63933 [63934]: rust-lang/rust#63934 [63938]: rust-lang/rust#63938 [63940]: rust-lang/rust#63940 [63941]: rust-lang/rust#63941 [63945]: rust-lang/rust#63945 [64010]: rust-lang/rust#64010 [64028]: rust-lang/rust#64028 [64334]: rust-lang/rust#64334 [cargo/7237]: rust-lang/cargo#7237 [cargo/7241]: rust-lang/cargo#7241 [cargo/7315]: rust-lang/cargo#7315 [`Pin::into_inner`]: https://doc.rust-lang.org/std/pin/struct.Pin.html#method.into_inner [`Instant::checked_duration_since`]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.checked_duration_since [`Instant::saturating_duration_since`]: https://doc.rust-lang.org/std/time/struct.Instant.html#method.saturating_duration_since
When Custom attributes inside function parameters available? Is there a plan? |
It is currently possible to parse custom attributes using procedural macros but they can't be present in the final |
Thanks for your reply, i don't quite understand "they can't be present in the final #[post("/path/{id}")]
async fn post_data(data: &PostData, #[path_varible("id")]id: i32, #[header("token")] token: String) -> Result<String, Error> {} Is this possible? |
Taking into consideration that
Take a look at https://doc.rust-lang.org/reference/procedural-macros.html to learn more about procedural macros, use the |
Thank you very much, i have already implemented #[post], and can not find examples used on function parameters, i will try later, thanks again |
Formally implement let chains ## Let chains My longest and hardest contribution since rust-lang#64010. Thanks to `@Centril` for creating the RFC and special thanks to `@matthewjasper` for helping me since the beginning of this journey. In fact, `@matthewjasper` did much of the complicated MIR stuff so it's true to say that this feature wouldn't be possible without him. Thanks again `@matthewjasper!` With the changes proposed in this PR, it will be possible to chain let expressions along side local variable declarations or ordinary conditional expressions. In other words, do much of what the `if_chain` crate already does. ## Other considerations * `if let guard` and `let ... else` features need special care and should be handled in a following PR. * Irrefutable patterns are allowed within a let chain context * ~~Three Clippy lints were already converted to start dogfooding and help detect possible corner cases~~ cc rust-lang#53667
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: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
, andforbid
. Currently, only the lintsunused_variables
andunused_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.
Reference guide
In the grammar of function and function pointer, the grammar of variadic tails (
...
) and parameters are changed respectively from:into:
The grammar of a closure parameter is changed from:
into:
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 byOuterAttr+
.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, "Attributes in formal function parameter position".
On 2019-04-30, RFC 2565 is merged and the tracking issue is made.
On 2019-06-12, a partial implementation was completed. The implementation was done in #60669 by @c410-f3r and the PR was reviewed by @petrochenkov and @Centril.
On 2019-07-29, #61238 was fixed in #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 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, 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.
All attributes that should be allowed. This includes
cfg
,cfg_attr
, and lints check attributes.Built-in attributes, which should be forbidden, e.g.,
#[test]
, are.cfg
andcfg_attr
are properly evaluated.unused_mut
andunused_variables
are correctly applied to parameter patterns.Pretty printing takes formal parameter attributes into account.
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.This report is a collaborative work with @Centril.