Format core and std macro rules, removing needless surrounding blocks by dtolnay · Pull Request #94868 · rust-lang/rust (original) (raw)

Many of the asserting and printing macros in core and std are written with prehistoric-looking formatting, like this:

In modern Rust style this would conventionally be written as follows instead, always using braces and a trailing semicolon on the macro arms:

Getting rid of the unneeded braces inside the expansion reduces extraneous indentation in macro-expanded code. For example:

println!("repro {}", true);

// before:

{ ::std::io::_print( ::core::fmt::Arguments::new_v1( &["repro ", "\n"], &[::core::fmt::ArgumentV1::new_display(&true)], ), ); };

// after:

::std::io::_print( ::core::fmt::Arguments::new_v1( &["repro ", "\n"], &[::core::fmt::ArgumentV1::new_display(&true)], ), );

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Mar 11, 2022

r? @yaahc

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📌 Commit af53809 has been approved by Dylan-DPC

bors added S-waiting-on-bors

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and removed S-waiting-on-review

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Mar 13, 2022

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Mar 13, 2022

Format core and std macro rules, removing needless surrounding blocks

Many of the asserting and printing macros in core and std are written with prehistoric-looking formatting, like this:

https://github.com/rust-lang/rust/blob/335ffbfa547df94ac236f5c56130cecf99c8d82b/library/std/src/macros.rs#L96-L101

In modern Rust style this would conventionally be written as follows instead, always using braces and a trailing semicolon on the macro arms:

https://github.com/rust-lang/rust/blob/af53809c874e0afb7be966df4d3cfcaa05277c53/library/std/src/macros.rs#L98-L105

Getting rid of the unneeded braces inside the expansion reduces extraneous indentation in macro-expanded code. For example:

println!("repro {}", true);

// before:

{
    ::std::io::_print(
        ::core::fmt::Arguments::new_v1(
            &["repro ", "\n"],
            &[::core::fmt::ArgumentV1::new_display(&true)],
        ),
    );
};

// after:

::std::io::_print(
    ::core::fmt::Arguments::new_v1(
        &["repro ", "\n"],
        &[::core::fmt::ArgumentV1::new_display(&true)],
    ),
);

⌛ Testing commit af53809 with merge 28838f68c28e8f45725d715555a73c55dbd9323d...

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Mar 13, 2022

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I don't know how to reproduce the run-make-fulldeps/coverage-reports failure on aarch64-gnu, but I noticed this snippet in the logs which looks relevant, so I will try to make the change that it shows.

--- expected_show_coverage.closure.txt 2022-03-13 10:25:55.192734369 +0000 +++ /checkout/obj/build/aarch64-unknown-linux-gnu/test/run-make-fulldeps/coverage-reports/coverage-reports/actual_show_coverage.closure.txt 2022-03-13 11:10:50.435023772 +0000 @@ -116,8 +116,8 @@ 116| 1| 117| 1| let 118| 1| _unused_closure

• 119| | =
• 120| | |

• 119| 1| =
• 120| 1| | 121| | mut countdown 122| | | 123| 0| { @@ -173,7 +173,7 @@ 169| | ; 170| | 171| 1| let short_used_not_covered_closure_line_break_no_block_embedded_branch =

• 172| | | _unused_arg: u8 |

• 172| 1| | _unused_arg: u8 | 173| 0| println!( 174| 0| "not called: {}", 175| 0| if is_true { "check" } else { "me" } @@ -191,7 +191,7 @@ 187| | ; 188| | 189| 1| let short_used_covered_closure_line_break_no_block_embedded_branch =

• 190| 1| | _unused_arg: u8 |

• 190| | | _unused_arg: u8 | 191| 1| println!( 192| 1| "not called: {}", 193| 1| if is_true { "check" } else { "me" }

📌 Commit ac5c657 has been approved by Dylan-DPC

bors added S-waiting-on-bors

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Mar 16, 2022

bors added a commit to rust-lang-ci/rust that referenced this pull request

Mar 16, 2022

Rollup of 5 pull requests

Successful merges:

• rust-lang#94868 (Format core and std macro rules, removing needless surrounding blocks)
• rust-lang#94951 (Extend the irrefutable_let_patterns lint to let chains)
• rust-lang#94955 (Refactor: Use format_args_capture in some parts of rustc_parse)
• rust-lang#94957 (Improve the explanation about the behaviour of read_line)
• rust-lang#94974 (Ensure that let_else does not interact with let_chains)

Failed merges:

r? @ghost @rustbot modify labels: rollup

This was referenced

Apr 26, 2022

bors added a commit to rust-lang-ci/rust that referenced this pull request

May 1, 2022

…lacrum

Make [e]println macros eagerly drop temporaries (for backport)

This PR extracts the subset of rust-lang#96455 which is only the parts necessary for fixing the 1.61-beta regressions in rust-lang#96434.

My larger PR rust-lang#96455 contains a few other changes relative to the pre-rust-lang#94868 behavior; those are not necessary to backport into 1.61.

ehuss pushed a commit to ehuss/rust that referenced this pull request

May 4, 2022

…lacrum

Make [e]println macros eagerly drop temporaries (for backport)

This PR extracts the subset of rust-lang#96455 which is only the parts necessary for fixing the 1.61-beta regressions in rust-lang#96434.

My larger PR rust-lang#96455 contains a few other changes relative to the pre-rust-lang#94868 behavior; those are not necessary to backport into 1.61.

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request

May 12, 2022

Make write/print macros eagerly drop temporaries

This PR fixes the 2 regressions in rust-lang#96434 (println and eprintln) and changes all the other similar macros (write, writeln, print, eprint) to match the old pre-rust-lang#94868 behavior of println and eprintln.

Example of code that is affected by this change:

use std::sync::Mutex;

fn main() {
    let mutex = Mutex::new(0);
    print!("{}", mutex.lock().unwrap()) /* no semicolon */
}

You can see several real-world examples like this in the Crater links at the top of rust-lang#96434. This code failed to compile prior to this PR as follows, but works after this PR.

error[E0597]: `mutex` does not live long enough
 --> src/main.rs:5:18
  |
5 |     print!("{}", mutex.lock().unwrap()) /* no semicolon */
  |                  ^^^^^^^^^^^^---------
  |                  |
  |                  borrowed value does not live long enough
  |                  a temporary with access to the borrow is created here ...
6 | }
  | -
  | |
  | `mutex` dropped here while still borrowed
  | ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `MutexGuard`

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request

May 14, 2022

Make write/print macros eagerly drop temporaries

This PR fixes the 2 regressions in rust-lang#96434 (println and eprintln) and changes all the other similar macros (write, writeln, print, eprint) to match the old pre-rust-lang#94868 behavior of println and eprintln.

Example of code that is affected by this change:

use std::sync::Mutex;

fn main() {
    let mutex = Mutex::new(0);
    print!("{}", mutex.lock().unwrap()) /* no semicolon */
}

You can see several real-world examples like this in the Crater links at the top of rust-lang#96434. This code failed to compile prior to this PR as follows, but works after this PR.

error[E0597]: `mutex` does not live long enough
 --> src/main.rs:5:18
  |
5 |     print!("{}", mutex.lock().unwrap()) /* no semicolon */
  |                  ^^^^^^^^^^^^---------
  |                  |
  |                  borrowed value does not live long enough
  |                  a temporary with access to the borrow is created here ...
6 | }
  | -
  | |
  | `mutex` dropped here while still borrowed
  | ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `MutexGuard`

MabezDev pushed a commit to esp-rs/rust that referenced this pull request

May 17, 2022

…lacrum

Make [e]println macros eagerly drop temporaries (for backport)

This PR extracts the subset of rust-lang#96455 which is only the parts necessary for fixing the 1.61-beta regressions in rust-lang#96434.

My larger PR rust-lang#96455 contains a few other changes relative to the pre-rust-lang#94868 behavior; those are not necessary to backport into 1.61.

bors added a commit to rust-lang-ci/rust that referenced this pull request

May 23, 2022

Make write/print macros eagerly drop temporaries

This PR fixes the 2 regressions in rust-lang#96434 (println and eprintln) and changes all the other similar macros (write, writeln, print, eprint) to match the old pre-rust-lang#94868 behavior of println and eprintln.

Example of code that is affected by this change:

use std::sync::Mutex;

fn main() {
    let mutex = Mutex::new(0);
    print!("{}", mutex.lock().unwrap()) /* no semicolon */
}

You can see several real-world examples like this in the Crater links at the top of rust-lang#96434. This code failed to compile prior to this PR as follows, but works after this PR.

error[E0597]: `mutex` does not live long enough
 --> src/main.rs:5:18
  |
5 |     print!("{}", mutex.lock().unwrap()) /* no semicolon */
  |                  ^^^^^^^^^^^^---------
  |                  |
  |                  borrowed value does not live long enough
  |                  a temporary with access to the borrow is created here ...
6 | }
  | -
  | |
  | `mutex` dropped here while still borrowed
  | ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `MutexGuard`

Dylan-DPC added a commit to Dylan-DPC/rust that referenced this pull request

Jul 28, 2022

Revert write! and writeln! to late drop temporaries

Closes (on master, but not on beta) rust-lang#99684 by reverting the write! and writeln! parts of rust-lang#96455.

"Late drop" refers to dropping temporaries at the nearest semicolon outside of the macro invocation.

"Early drop" refers to dropping temporaries inside of the macro invocation.

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Jan 14, 2025