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

Hexilee · 2019-08-02T04:44:04Z

This is the example proc-macro:

extern crate proc_macro;
use proc_macro::TokenStream;

#[proc_macro_attribute]
pub fn rename_params(_args: TokenStream, input: TokenStream) -> TokenStream {
    println!("{}", &input);
    input
}

This is the test:

#![feature(param_attrs)]
use params_attribute_example::rename_params;

#[rename_params]
fn hello(a: i32, #[val] b: i32) {}

Run cargo expand --test rename-params，both of println result and expand result are:

fn hello(a: i32, b: i32) {}

Formal parameter attributes disappear in proc-macro.

Toolchain: nightly-x86_64-apple-darwin(8a58268b5 2019-07-31)

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

Centril · 2019-08-02T04:59:21Z

cc @c410-f3r @petrochenkov #60406

Centril · 2019-08-02T07:38:01Z

I have a fix in #63212.

@petrochenkov

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

@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.

Hexilee mentioned this issue Aug 2, 2019

Formal function attributes is still unsupported? dtolnay/syn#685

Closed

Centril self-assigned this Aug 2, 2019

Centril mentioned this issue Aug 2, 2019

Pretty print attributes in print_arg #63212

Merged

Centril added the requires-nightly This issue requires a nightly compiler in some way. label Aug 2, 2019

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

bors closed this as completed in #63212 Aug 3, 2019

Centril mentioned this issue Aug 3, 2019

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

Closed

4 tasks

This was referenced Aug 27, 2019

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

Closed

Stabilize param_attrs in Rust 1.39.0 #64010

Merged

bbqsrc mentioned this issue Sep 8, 2019

Regression of #63210 param attributes not showing in proc-macro TokenStream #64282

Closed

ehuss mentioned this issue Sep 30, 2019

Add reference for attributes in function parameters rust-lang/reference#657

Merged

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

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

Hexilee commented Aug 2, 2019 •

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Centril commented Aug 2, 2019

Centril commented Aug 2, 2019

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

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

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Hexilee commented Aug 2, 2019 • edited Loading

Centril commented Aug 2, 2019

Centril commented Aug 2, 2019

Hexilee commented Aug 2, 2019 •

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