[1/2] Implement macro meta-variable expressions #94368

c410-f3r · 2022-02-25T19:11:05Z

The logic behind length, index and count was removed but the parsing code is still present, i.e., everything is simply ignored like ignored.

r? @petrochenkov

cc #83527

src/test/ui/macros/rfc-3086-metavar-expr/dollar-dollar-has-correct-behavior.rs

compiler/rustc_expand/src/mbe/metavar_expr.rs

c410-f3r · 2022-03-06T22:28:30Z

Thanks again for the review, @petrochenkov.

I addressed everything but #94368 (comment) so let me know your thoughts.

@rustbot label +S-waiting-on-review -S-waiting-on-author

rustbot · 2022-03-06T22:31:39Z

Error: Label review can only be set by Rust team members

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compiler/rustc_expand/src/mbe/metavar_expr.rs

c410-f3r · 2022-03-09T13:54:07Z

I guess this is it

@rustbot label +S-waiting-on-review -S-waiting-on-author

compiler/rustc_expand/src/mbe/quoted.rs

petrochenkov · 2022-03-09T14:39:21Z

@bors r+

bors · 2022-03-09T14:39:23Z

📌 Commit 04b781175e653574c0d6665bf1d09e5ebb8090f8 has been approved by petrochenkov

bors · 2022-03-09T18:51:01Z

⌛ Testing commit 04b781175e653574c0d6665bf1d09e5ebb8090f8 with merge a47a581b8c5f5342dc59e31854c85f531edb3c94...

bors · 2022-03-09T19:25:46Z

💔 Test failed - checks-actions

c410-f3r · 2022-03-09T19:40:55Z

CI is broken -> #94774 (comment)

petrochenkov · 2022-03-09T20:03:53Z

@bors r+

bors · 2022-03-09T20:03:55Z

📌 Commit 8073a88 has been approved by petrochenkov

bors · 2022-03-09T20:03:56Z

🌲 The tree is currently closed for pull requests below priority 50. This pull request will be tested once the tree is reopened.

…aaaa, r=petrochenkov [1/2] Implement macro meta-variable expressions See rust-lang#93545 (comment) The logic behind `length`, `index` and `count` was removed but the parsing code is still present, i.e., everything is simply ignored like `ignored`. r? `@petrochenkov`

c410-f3r · 2022-03-10T10:32:22Z

2022-03-09T19:24:39.6807544Z /checkout/src/test/rustdoc-gui/mobile.goml mobile... FAILED
2022-03-09T19:24:39.6808635Z [ERROR] (line 27) Error: Evaluation failed: assert didn't fail: for command compare-elements-position-near-false: ("#preferred-light-theme .setting-name", "#preferred-light-theme .choice", {"y": 16})

Unrelated error

…aaaa, r=petrochenkov [1/2] Implement macro meta-variable expressions See rust-lang#93545 (comment) The logic behind `length`, `index` and `count` was removed but the parsing code is still present, i.e., everything is simply ignored like `ignored`. r? `@petrochenkov`

Rollup of 7 pull requests Successful merges: - rust-lang#93950 (Use modern formatting for format! macros) - rust-lang#94274 (Treat unstable lints as unknown) - rust-lang#94368 ([1/2] Implement macro meta-variable expressions) - rust-lang#94719 (Statically compile libstdc++ everywhere if asked) - rust-lang#94728 (Only emit pointer-like metadata for `Box<T, A>` when `A` is ZST) - rust-lang#94790 (enable portable-simd doctests in Miri) - rust-lang#94811 (Update browser-ui-test version) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

compiler/rustc_expand/src/mbe/macro_parser.rs

…lett Stabilize `$$` in Rust 1.63.0 # Stabilization proposal This PR proposes the stabilization of a subset of `#![feature(macro_metavar_expr)]` or more specifically, the stabilization of dollar-dollar (`$$`). Tracking issue: rust-lang#83527 Version: 1.63 (2022-06-28 => beta, 2022-08-11 => stable). ## What is stabilized ```rust macro_rules! foo { () => { macro_rules! bar { ( $$( $$any:tt )* ) => { $$( $$any )* }; } }; } fn main() { foo!(); } ``` ## Motivation For more examples, see the [RFC](https://github.com/markbt/rfcs/blob/macro_metavar_expr/text/0000-macro-metavar-expr.md). Users must currently resort to a tricky and not so well-known hack to declare nested macros with repetitions. ```rust macro_rules! foo { ($dollar:tt) => { macro_rules! bar { ( $dollar ( $any:tt )* ) => { $dollar ( $any )* }; } }; } fn main() { foo!($); } ``` As seen above, such hack is fragile and makes work with declarative macros much more unpleasant. Dollar-dollar (`$$`), on the other hand, makes nested macros more intuitive. ## What isn't stabilized `count`, `ignore`, `index` and `length` are not being stabilized due to the lack of consensus. ## History * 2021-02-22, [RFC: Declarative macro metavariable expressions](rust-lang/rfcs#3086) * 2021-03-26, [Tracking Issue for RFC 3086: macro metavariable expressions](rust-lang#83527) * 2022-02-01, [Implement macro meta-variable expressions](rust-lang#93545) * 2022-02-25, [[1/2] Implement macro meta-variable expressions](rust-lang#94368) * 2022-03-11, [[2/2] Implement macro meta-variable expressions](rust-lang#94833) * 2022-03-12, [Fix remaining meta-variable expression TODOs](rust-lang#94884) * 2019-03-21, [[macro-metavar-expr] Fix generated tokens hygiene](rust-lang#95188) * 2022-04-07, [Kickstart the inner usage of macro_metavar_expr](rust-lang#95761) * 2022-04-07, [[macro_metavar_expr] Add tests to ensure the feature requirement](rust-lang#95764) ## Non-stabilized expressions rust-lang#83527 lists several concerns about some characteristics of `count`, `index` and `length` that effectively make their stabilization unfeasible. `$$` and `ignore`, however, are not part of any discussion and thus are suitable for stabilization. It is not in the scope of this PR to detail each concern or suggest any possible converging solution. Such thing should be restrained in this tracking issue. ## Tests This list is a subset of https://github.com/rust-lang/rust/tree/master/src/test/ui/macros/rfc-3086-metavar-expr * [Ensures that nested macros have correct behavior](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/dollar-dollar-has-correct-behavior.rs) * [Compares produced tokens to assert expected outputs](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/feature-gate-macro_metavar_expr.rs) * [Checks the declarations of the feature](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/required-feature.rs) * [Verifies all possible errors that can occur due to incorrect user input](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/syntax-errors.rs) ## Possible future work Once consensus is achieved, other nightly expressions can be stabilized. Thanks `@markbt` for creating the RFC and thanks to `@petrochenkov` and `@mark-i-m` for reviewing the implementations.

…lett Stabilize `$$` in Rust 1.63.0 # Stabilization proposal This PR proposes the stabilization of a subset of `#![feature(macro_metavar_expr)]` or more specifically, the stabilization of dollar-dollar (`$$`). Tracking issue: rust-lang#83527 Version: 1.63 (2022-06-28 => beta, 2022-08-11 => stable). ## What is stabilized ```rust macro_rules! foo { () => { macro_rules! bar { ( $$( $$any:tt )* ) => { $$( $$any )* }; } }; } fn main() { foo!(); } ``` ## Motivation For more examples, see the [RFC](https://github.com/markbt/rfcs/blob/macro_metavar_expr/text/0000-macro-metavar-expr.md). Users must currently resort to a tricky and not so well-known hack to declare nested macros with repetitions. ```rust macro_rules! foo { ($dollar:tt) => { macro_rules! bar { ( $dollar ( $any:tt )* ) => { $dollar ( $any )* }; } }; } fn main() { foo!($); } ``` As seen above, such hack is fragile and makes work with declarative macros much more unpleasant. Dollar-dollar (`$$`), on the other hand, makes nested macros more intuitive. ## What isn't stabilized `count`, `ignore`, `index` and `length` are not being stabilized due to the lack of consensus. ## History * 2021-02-22, [RFC: Declarative macro metavariable expressions](rust-lang/rfcs#3086) * 2021-03-26, [Tracking Issue for RFC 3086: macro metavariable expressions](rust-lang#83527) * 2022-02-01, [Implement macro meta-variable expressions](rust-lang#93545) * 2022-02-25, [[1/2] Implement macro meta-variable expressions](rust-lang#94368) * 2022-03-11, [[2/2] Implement macro meta-variable expressions](rust-lang#94833) * 2022-03-12, [Fix remaining meta-variable expression TODOs](rust-lang#94884) * 2019-03-21, [[macro-metavar-expr] Fix generated tokens hygiene](rust-lang#95188) * 2022-04-07, [Kickstart the inner usage of macro_metavar_expr](rust-lang#95761) * 2022-04-07, [[macro_metavar_expr] Add tests to ensure the feature requirement](rust-lang#95764) ## Non-stabilized expressions rust-lang#83527 lists several concerns about some characteristics of `count`, `index` and `length` that effectively make their stabilization unfeasible. `$$` and `ignore`, however, are not part of any discussion and thus are suitable for stabilization. It is not in the scope of this PR to detail each concern or suggest any possible converging solution. Such thing should be restrained in this tracking issue. ## Tests This list is a subset of https://github.com/rust-lang/rust/tree/master/src/test/ui/macros/rfc-3086-metavar-expr * [Ensures that nested macros have correct behavior](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/dollar-dollar-has-correct-behavior.rs) * [Compares produced tokens to assert expected outputs](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/feature-gate-macro_metavar_expr.rs) * [Checks the declarations of the feature](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/required-feature.rs) * [Verifies all possible errors that can occur due to incorrect user input](https://github.com/rust-lang/rust/blob/master/src/test/ui/macros/rfc-3086-metavar-expr/syntax-errors.rs) ## Possible future work Once consensus is achieved, other nightly expressions can be stabilized. Thanks ``@markbt`` for creating the RFC and thanks to ``@petrochenkov`` and ``@mark-i-m`` for reviewing the implementations.

rust-highfive assigned petrochenkov Feb 25, 2022

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Implement macro meta-variable expressions #93545

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Implement macro meta-variable expressions

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Rollup of 16 pull requests #94784

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Rollup of 7 pull requests #94807

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Rollup of 7 pull requests #94824

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bors merged commit 634a6b0 into rust-lang:master Mar 11, 2022

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Revert/meta #95078

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Stabilize $$ in Rust 1.63.0 #95860

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Stabilize count, ignore, index, and len (macro_metavar_expr) #122808

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[1/2] Implement macro meta-variable expressions #94368

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[1/2] Implement macro meta-variable expressions #94368

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