Tag all format-like macros with #[clippy::format_args]

[nyurik]

Help needed

Is there a workaround for #98291 ? The build errors here seem to be triggered by that issue.

Description

Since 1.85, Clippy supports attribute-based discovery of the format!-compatible macros, i.e. macros whose trailing arguments can be passed to format_args! as is.

Tagging core library with the same attribute will allow clippy to stop maintaining a separate list of format-like macros - allowing Clippy to validate macro usage for all lints that work on format arguments. See also rust-lang/rust-clippy#14267

[rustbot]

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[tbu-]

I think the attribute shouldn't be clippy-specific — other tools might be able to use that as well.

[nyurik]

@tbu- not sure i understand. Anyone can use this attribute, but it would be quiet a challenge to introduce a new attribute namespace to the whole ecosystem, especially because now clippy utils is published as a crate, and can be reused by others... so it already expects this namespace.

[rust-log-analyzer]

The job x86_64-gnu-llvm-18 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#22 exporting to docker image format
#22 sending tarball 28.8s done
#22 DONE 31.8s
##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-18]
debug: `DISABLE_CI_RUSTC_IF_INCOMPATIBLE` configured.
---
sccache: Listening on address 127.0.0.1:4226
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-18', '--enable-llvm-link-shared', '--set', 'rust.randomize-layout=true', '--set', 'rust.thin-lto-import-instr-limit=10', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--set', 'rust.lld=false', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-18/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.randomize-layout := True
configure: rust.thin-lto-import-instr-limit := 10
---
   Compiling compiler_builtins v0.1.146
error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
    --> library/core/src/macros/mod.rs:64:114
     |
42   | / macro_rules! assert_eq {
43   | |     ($left:expr, $right:expr $(,)?) => {
44   | |         match (&$left, &$right) {
45   | |             (left_val, right_val) => {
...    |
64   | |                     $crate::panicking::assert_failed(kind, &*left_val, &*right_val, $crate::option::Option::Some($crate::format_args!($($...
...    |
68   | |     };
69   | | }
     | |_- in this expansion of `assert_eq!`
     | |_- in this expansion of `assert_eq!`
     |
    ::: library/core/src/mem/maybe_uninit.rs:1400:9
     |
1400 |           assert_eq!(self.len(), src.len(), "destination and source slices have different lengths");
     |
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1096:5
     |
1096 | /     macro_rules! format_args {
1097 | |         ($fmt:expr) => {{ /* compiler built-in */ }};
1098 | |         ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
     | |_____^
     = note: `#[deny(macro_expanded_macro_exports_accessed_by_absolute_paths)]` on by default

error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
---
     |
    ::: library/core/src/num/bignum.rs:34:1
     |
34   | / macro_rules! impl_full_ops {
35   | |     ($($ty:ty: add($addfn:path), mul/div($bigty:ident);)*) => (
36   | |         $(
37   | |             impl FullOps for $ty {
...    |
47   | |                     debug_assert!(borrow < other);
...    |
56   | | }
     | |_- in this expansion of `impl_full_ops!` (#1)
57   |
57   |
58   | / impl_full_ops! {
59   | |     u8:  add(intrinsics::u8_add_with_overflow),  mul/div(u16);
60   | |     u16: add(intrinsics::u16_add_with_overflow), mul/div(u32);
61   | |     u32: add(intrinsics::u32_add_with_overflow), mul/div(u64);
64   | | }
     | |_- in this macro invocation (#1)
     |
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1682:5
     |
1682 | /     macro_rules! assert {
1683 | |         ($cond:expr $(,)?) => {{ /* compiler built-in */ }};
1684 | |         ($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }};
     | |_____^

error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
   --> library/core/src/macros/mod.rs:430:13
---
432 | |     };
433 | | }
    | |_- in this expansion of `debug_assert_eq!`
    |
   ::: library/core/src/num/flt2dec/strategy/grisu.rs:202:5
    |
202 |       debug_assert_eq!(plus.e, minus.e);
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
note: the macro is defined here
   --> library/core/src/macros/mod.rs:42:1
    |
42  | / macro_rules! assert_eq {
43  | |     ($left:expr, $right:expr $(,)?) => {
44  | |         match (&$left, &$right) {
45  | |             (left_val, right_val) => {
68  | |     };
69  | | }
    | |_^


error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
    --> library/core/src/macros/mod.rs:715:24
     |
713  | / macro_rules! write {
714  | |     ($dst:expr, $($arg:tt)*) => {
     | |                        ^^^^^^^^^^^^^^^^^^^
716  | |     };
717  | | }
     | |_- in this expansion of `write!` (#2)
     | |_- in this expansion of `write!` (#2)
     |
    ::: library/core/src/num/bignum.rs:70:1
     |
70   | / macro_rules! define_bignum {
71   | |     ($name:ident: type=$ty:ty, n=$n:expr) => {
72   | |         /// Stack-allocated arbitrary-precision (up to certain limit) integer.
...    |
...    |
413  | |                 write!(f, "{:#x}", self.base[sz - 1])?;
...    |
420  | |     };
421  | | }
421  | | }
     | |_- in this expansion of `define_bignum!` (#1)
...
426  |   define_bignum!(Big32x40: type=Digit32, n=40);
     |
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1096:5
     |
1096 | /     macro_rules! format_args {
1097 | |         ($fmt:expr) => {{ /* compiler built-in */ }};
1098 | |         ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
     | |_____^

error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
    --> library/core/src/prelude/v1.rs:64:5
    --> library/core/src/prelude/v1.rs:64:5
     |
64   |     assert, cfg, column, compile_error, concat, concat_idents, env, file, format_args,
     |
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1682:5
     |
1682 | /     macro_rules! assert {
1683 | |         ($cond:expr $(,)?) => {{ /* compiler built-in */ }};
1684 | |         ($cond:expr, $($arg:tt)+) => {{ /* compiler built-in */ }};
     | |_____^

error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
    --> library/core/src/prelude/v1.rs:64:75
    --> library/core/src/prelude/v1.rs:64:75
     |
64   |     assert, cfg, column, compile_error, concat, concat_idents, env, file, format_args,
     |
     = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
     = note: for more information, see issue #52234 <https://github.com/rust-lang/rust/issues/52234>
note: the macro is defined here
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1096:5
     |
1096 | /     macro_rules! format_args {
1097 | |         ($fmt:expr) => {{ /* compiler built-in */ }};
1098 | |         ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
     | |_____^

error: macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths
     |
---
137  | / pub macro unreachable_2021 {
138  | |     () => (
139  | |         $crate::panicking::panic("internal error: entered unreachable code")
140  | |     ),
141  | |     ($($t:tt)+) => (
142  | |         $crate::panic!("internal error: entered unreachable code: {}", $crate::format_args!($($t)+))
143  | |     ),
144  | | }
     | |_- in this expansion of `$crate::panic::unreachable_2021!` (#2)
     |
---
note: the macro is defined here
    --> library/core/src/macros/mod.rs:1096:5
     |
1096 | /     macro_rules! format_args {
1097 | |         ($fmt:expr) => {{ /* compiler built-in */ }};
1098 | |         ($fmt:expr, $($args:tt)*) => {{ /* compiler built-in */ }};
     | |_____^

error: could not compile `core` (lib) due to 7 previous errors
Build completed unsuccessfully in 0:00:22

[blyxyas]

We need to benchmark this in Clippy, it may add way more work for the CPU than it's worth.

I'll benchmark it in the coming days :)

[joboet]

Is there a reason why this one is not gated on cfg(test) but all others are?

[nyurik]

TBH, I do not think any usage of the clippy attribute should be gated on anything - e.g. if its a test, clippy should still do the format-related lints. The bigger issue is the #98291 - which blocks many crates as well as stdlib from usign this feature, and I have no idea if there is a workaround for it...

[joboet]

I don't feel qualified to review this.

r? @m-ou-se
as Iirc, you've worked on formatting-related lints in clippy before

[bors]

☔ The latest upstream changes (presumably #138208) made this pull request unmergeable. Please resolve the merge conflicts.