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Stabilize proc macros generating `macro_rules` items #64035

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merged 2 commits into from Oct 15, 2019

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petrochenkov commented Aug 31, 2019

Fn-like and attribute proc macros can now generate macro_rules items.

cc #54727

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rust-highfive commented Aug 31, 2019

r? @eddyb

(rust_highfive has picked a reviewer for you, use r? to override)

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JohnCSimon commented Sep 7, 2019

Ping from triage - @petrochenkov this has sat idle for 7 days, can you please post the status of this PR?

thank you!

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petrochenkov commented Sep 7, 2019

Busy week, I'll get to it ~next weekend.

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JohnTitor commented Sep 15, 2019

Ping from triage: @petrochenkov any updates on this?

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JohnCSimon commented Sep 21, 2019

Ping from triage.
@petrochenkov Just letting you know, this has sat idle for the last three weeks.
Thank you.

@petrochenkov petrochenkov force-pushed the petrochenkov:stabmacgen branch 2 times, most recently from 92aa55c to 2cb35b0 Sep 21, 2019
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petrochenkov commented Sep 22, 2019

Stabilization report

Function-like macros and attribute macros can now generate macro_rules items.

For historical reasons this feature was never gated for derive macros (which were stabilized much earlier than other macro kinds).
So if people need to generate macro_rules, they usually just generate derives expanding to macro_rules instead of generating macro_rules directly.
As a result, the feature is de-facto stable and is actively relied upon by the ecosystem, at least through the proc_macro_hack crate.

Stable proc macros can only use transparent "call-site" hygiene, so in the basic case of a macro_rules item generated by a transparent macro, the item will behave as if it was copy-pasted into the call site.
So, names produced by expanding that macro_rules item will behave as if the item was written directly - local variables and labels will be hygienic, other names will be unhygienic and $crate will refer to the crate containing the macro_rules item, not to the proc macro crate.
This behavior is pretty intuitive and we didn't receive reports of bugs or unexpected behavior in this area, AFAIK.
If you want some specific cases tested, please leave a comment.

If some hygiene rules change in the future, they will most probably affect corner cases with some complex nesting and interactions between various kinds of hygiene mixed.
It will affect people to the same extent whether we stabilize macro_rules-generating fn-like and attribute macros or not, because they will affect derives anyway.

@petrochenkov petrochenkov changed the title [WIP] Stabilize proc macros generating `macro_rules` items Stabilize proc macros generating `macro_rules` items Sep 22, 2019
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This is a pretty straight-forward stabilization, r=me once the decision has been taken.

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Centril commented Sep 26, 2019

@rust-highfive rust-highfive assigned pnkfelix and unassigned eddyb Sep 26, 2019
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rfcbot commented Oct 5, 2019

🔔 This is now entering its final comment period, as per the review above. 🔔

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rfcbot commented Oct 15, 2019

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

The RFC will be merged soon.

@petrochenkov petrochenkov force-pushed the petrochenkov:stabmacgen branch from 2cb35b0 to d80be3b Oct 15, 2019
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petrochenkov commented Oct 15, 2019

@bors r=eddyb

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bors commented Oct 15, 2019

📌 Commit d80be3b has been approved by eddyb

Centril added a commit to Centril/rust that referenced this pull request Oct 15, 2019
Stabilize proc macros generating `macro_rules` items

Fn-like and attribute proc macros can now generate `macro_rules` items.

cc rust-lang#54727
bors added a commit that referenced this pull request Oct 15, 2019
Rollup of 4 pull requests

Successful merges:

 - #64035 (Stabilize proc macros generating `macro_rules` items)
 - #65376 (syntax: misc extractions)
 - #65425 (Optimize `BitIter`)
 - #65428 (Refactor: Rename `db` locals to `diag`)

Failed merges:

r? @ghost
Centril added a commit to Centril/rust that referenced this pull request Oct 15, 2019
Stabilize proc macros generating `macro_rules` items

Fn-like and attribute proc macros can now generate `macro_rules` items.

cc rust-lang#54727
bors added a commit that referenced this pull request Oct 15, 2019
Rollup of 4 pull requests

Successful merges:

 - #64035 (Stabilize proc macros generating `macro_rules` items)
 - #65376 (syntax: misc extractions)
 - #65426 (Remove custom `PartialEq` impls for `LocalInternedString`.)
 - #65428 (Refactor: Rename `db` locals to `diag`)

Failed merges:

r? @ghost
@bors bors merged commit d80be3b into rust-lang:master Oct 15, 2019
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@hobofan hobofan mentioned this pull request Nov 19, 2019
@la10736 la10736 mentioned this pull request Dec 28, 2019
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 6, 2020
Version 1.40.0 (2019-12-19)
===========================

Language
--------
- [You can now use tuple `struct`s and tuple `enum` variant's constructors in
  `const` contexts.][65188] e.g.

  ```rust
  pub struct Point(i32, i32);

  const ORIGIN: Point = {
      let constructor = Point;

      constructor(0, 0)
  };
  ```

- [You can now mark `struct`s, `enum`s, and `enum` variants with the `#[non_exhaustive]` attribute to
  indicate that there may be variants or fields added in the future.][64639]
  For example this requires adding a wild-card branch (`_ => {}`) to any match
  statements on a non-exhaustive `enum`. [(RFC 2008)]
- [You can now use function-like procedural macros in `extern` blocks and in
  type positions.][63931] e.g. `type Generated = macro!();`
- [Function-like and attribute procedural macros can now emit
  `macro_rules!` items, so you can now have your macros generate macros.][64035]
- [The `meta` pattern matcher in `macro_rules!` now correctly matches the modern
  attribute syntax.][63674] For example `(#[$m:meta])` now matches `#[attr]`,
  `#[attr{tokens}]`, `#[attr[tokens]]`, and `#[attr(tokens)]`.

Compiler
--------
- [Added tier 3 support\* for the
  `thumbv7neon-unknown-linux-musleabihf` target.][66103]
- [Added tier 3 support for the
  `aarch64-unknown-none-softfloat` target.][64589]
- [Added tier 3 support for the `mips64-unknown-linux-muslabi64`, and
  `mips64el-unknown-linux-muslabi64` targets.][65843]

\* Refer to Rust's [platform support page][forge-platform-support] for more
  information on Rust's tiered platform support.

Libraries
---------
- [The `is_power_of_two` method on unsigned numeric types is now a `const` function.][65092]

Stabilized APIs
---------------
- [`BTreeMap::get_key_value`]
- [`HashMap::get_key_value`]
- [`Option::as_deref_mut`]
- [`Option::as_deref`]
- [`Option::flatten`]
- [`UdpSocket::peer_addr`]
- [`f32::to_be_bytes`]
- [`f32::to_le_bytes`]
- [`f32::to_ne_bytes`]
- [`f64::to_be_bytes`]
- [`f64::to_le_bytes`]
- [`f64::to_ne_bytes`]
- [`f32::from_be_bytes`]
- [`f32::from_le_bytes`]
- [`f32::from_ne_bytes`]
- [`f64::from_be_bytes`]
- [`f64::from_le_bytes`]
- [`f64::from_ne_bytes`]
- [`mem::take`]
- [`slice::repeat`]
- [`todo!`]

Cargo
-----
- [Cargo will now always display warnings, rather than only on
  fresh builds.][cargo/7450]
- [Feature flags (except `--all-features`) passed to a virtual workspace will
  now produce an error.][cargo/7507] Previously these flags were ignored.
- [You can now publish `dev-dependencies` without including
  a `version`.][cargo/7333]

Misc
----
- [You can now specify the `#[cfg(doctest)]` attribute to include an item only
  when running documentation tests with `rustdoc`.][63803]

Compatibility Notes
-------------------
- [As previously announced, any previous NLL warnings in the 2015 edition are
  now hard errors.][64221]
- [The `include!` macro will now warn if it failed to include the
  entire file.][64284] The `include!` macro unintentionally only includes the
  first _expression_ in a file, and this can be unintuitive. This will become
  either a hard error in a future release, or the behavior may be fixed to include all expressions as expected.
- [Using `#[inline]` on function prototypes and consts now emits a warning under
  `unused_attribute` lint.][65294] Using `#[inline]` anywhere else inside traits
  or `extern` blocks now correctly emits a hard error.

[65294]: rust-lang/rust#65294
[66103]: rust-lang/rust#66103
[65843]: rust-lang/rust#65843
[65188]: rust-lang/rust#65188
[65092]: rust-lang/rust#65092
[64589]: rust-lang/rust#64589
[64639]: rust-lang/rust#64639
[64221]: rust-lang/rust#64221
[64284]: rust-lang/rust#64284
[63931]: rust-lang/rust#63931
[64035]: rust-lang/rust#64035
[63674]: rust-lang/rust#63674
[63803]: rust-lang/rust#63803
[cargo/7450]: rust-lang/cargo#7450
[cargo/7507]: rust-lang/cargo#7507
[cargo/7525]: rust-lang/cargo#7525
[cargo/7333]: rust-lang/cargo#7333
[(rfc 2008)]: https://rust-lang.github.io/rfcs/2008-non-exhaustive.html
[`f32::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_be_bytes
[`f32::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_le_bytes
[`f32::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_ne_bytes
[`f64::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_be_bytes
[`f64::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_le_bytes
[`f64::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_ne_bytes
[`f32::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_be_bytes
[`f32::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_le_bytes
[`f32::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_ne_bytes
[`f64::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_be_bytes
[`f64::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_le_bytes
[`f64::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_ne_bytes
[`option::flatten`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.flatten
[`option::as_deref`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref
[`option::as_deref_mut`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref_mut
[`hashmap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.get_key_value
[`btreemap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.get_key_value
[`slice::repeat`]: https://doc.rust-lang.org/std/primitive.slice.html#method.repeat
[`mem::take`]: https://doc.rust-lang.org/std/mem/fn.take.html
[`udpsocket::peer_addr`]: https://doc.rust-lang.org/std/net/struct.UdpSocket.html#method.peer_addr
[`todo!`]: https://doc.rust-lang.org/std/macro.todo.html
netbsd-srcmastr pushed a commit to NetBSD/pkgsrc that referenced this pull request Jan 14, 2020
Version 1.40.0 (2019-12-19)
===========================

Language
--------
- [You can now use tuple `struct`s and tuple `enum` variant's constructors in
  `const` contexts.][65188] e.g.

  ```rust
  pub struct Point(i32, i32);

  const ORIGIN: Point = {
      let constructor = Point;

      constructor(0, 0)
  };
  ```

- [You can now mark `struct`s, `enum`s, and `enum` variants with the `#[non_exhaustive]` attribute to
  indicate that there may be variants or fields added in the future.][64639]
  For example this requires adding a wild-card branch (`_ => {}`) to any match
  statements on a non-exhaustive `enum`. [(RFC 2008)]
- [You can now use function-like procedural macros in `extern` blocks and in
  type positions.][63931] e.g. `type Generated = macro!();`
- [Function-like and attribute procedural macros can now emit
  `macro_rules!` items, so you can now have your macros generate macros.][64035]
- [The `meta` pattern matcher in `macro_rules!` now correctly matches the modern
  attribute syntax.][63674] For example `(#[$m:meta])` now matches `#[attr]`,
  `#[attr{tokens}]`, `#[attr[tokens]]`, and `#[attr(tokens)]`.

Compiler
--------
- [Added tier 3 support\* for the
  `thumbv7neon-unknown-linux-musleabihf` target.][66103]
- [Added tier 3 support for the
  `aarch64-unknown-none-softfloat` target.][64589]
- [Added tier 3 support for the `mips64-unknown-linux-muslabi64`, and
  `mips64el-unknown-linux-muslabi64` targets.][65843]

\* Refer to Rust's [platform support page][forge-platform-support] for more
  information on Rust's tiered platform support.

Libraries
---------
- [The `is_power_of_two` method on unsigned numeric types is now a `const` function.][65092]

Stabilized APIs
---------------
- [`BTreeMap::get_key_value`]
- [`HashMap::get_key_value`]
- [`Option::as_deref_mut`]
- [`Option::as_deref`]
- [`Option::flatten`]
- [`UdpSocket::peer_addr`]
- [`f32::to_be_bytes`]
- [`f32::to_le_bytes`]
- [`f32::to_ne_bytes`]
- [`f64::to_be_bytes`]
- [`f64::to_le_bytes`]
- [`f64::to_ne_bytes`]
- [`f32::from_be_bytes`]
- [`f32::from_le_bytes`]
- [`f32::from_ne_bytes`]
- [`f64::from_be_bytes`]
- [`f64::from_le_bytes`]
- [`f64::from_ne_bytes`]
- [`mem::take`]
- [`slice::repeat`]
- [`todo!`]

Cargo
-----
- [Cargo will now always display warnings, rather than only on
  fresh builds.][cargo/7450]
- [Feature flags (except `--all-features`) passed to a virtual workspace will
  now produce an error.][cargo/7507] Previously these flags were ignored.
- [You can now publish `dev-dependencies` without including
  a `version`.][cargo/7333]

Misc
----
- [You can now specify the `#[cfg(doctest)]` attribute to include an item only
  when running documentation tests with `rustdoc`.][63803]

Compatibility Notes
-------------------
- [As previously announced, any previous NLL warnings in the 2015 edition are
  now hard errors.][64221]
- [The `include!` macro will now warn if it failed to include the
  entire file.][64284] The `include!` macro unintentionally only includes the
  first _expression_ in a file, and this can be unintuitive. This will become
  either a hard error in a future release, or the behavior may be fixed to include all expressions as expected.
- [Using `#[inline]` on function prototypes and consts now emits a warning under
  `unused_attribute` lint.][65294] Using `#[inline]` anywhere else inside traits
  or `extern` blocks now correctly emits a hard error.

[65294]: rust-lang/rust#65294
[66103]: rust-lang/rust#66103
[65843]: rust-lang/rust#65843
[65188]: rust-lang/rust#65188
[65092]: rust-lang/rust#65092
[64589]: rust-lang/rust#64589
[64639]: rust-lang/rust#64639
[64221]: rust-lang/rust#64221
[64284]: rust-lang/rust#64284
[63931]: rust-lang/rust#63931
[64035]: rust-lang/rust#64035
[63674]: rust-lang/rust#63674
[63803]: rust-lang/rust#63803
[cargo/7450]: rust-lang/cargo#7450
[cargo/7507]: rust-lang/cargo#7507
[cargo/7525]: rust-lang/cargo#7525
[cargo/7333]: rust-lang/cargo#7333
[(rfc 2008)]: https://rust-lang.github.io/rfcs/2008-non-exhaustive.html
[`f32::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_be_bytes
[`f32::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_le_bytes
[`f32::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.to_ne_bytes
[`f64::to_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_be_bytes
[`f64::to_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_le_bytes
[`f64::to_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.to_ne_bytes
[`f32::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_be_bytes
[`f32::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_le_bytes
[`f32::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f32.html#method.from_ne_bytes
[`f64::from_be_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_be_bytes
[`f64::from_le_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_le_bytes
[`f64::from_ne_bytes`]: https://doc.rust-lang.org/std/primitive.f64.html#method.from_ne_bytes
[`option::flatten`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.flatten
[`option::as_deref`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref
[`option::as_deref_mut`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.as_deref_mut
[`hashmap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.HashMap.html#method.get_key_value
[`btreemap::get_key_value`]: https://doc.rust-lang.org/std/collections/struct.BTreeMap.html#method.get_key_value
[`slice::repeat`]: https://doc.rust-lang.org/std/primitive.slice.html#method.repeat
[`mem::take`]: https://doc.rust-lang.org/std/mem/fn.take.html
[`udpsocket::peer_addr`]: https://doc.rust-lang.org/std/net/struct.UdpSocket.html#method.peer_addr
[`todo!`]: https://doc.rust-lang.org/std/macro.todo.html
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