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Stuart Cook
1987b15908
compiler: Forward attributes to eii-expanded macros Since https://github.com/rust-lang/rust/pull/150592 is quite complicated to reason about I figured it would be good to split it up in smaller pieces that are easier to digest. Here is the attribute fix in isolation. ## The Problem With this eii in **library/std/src/io/mod.rs**: ```rs /// Foo #[eii(on_broken_pipe)] #[unstable(feature = "on_broken_pipe", issue = "150588")] pub fn on_broken_pipe() -> OnBrokenPipe { OnBrokenPipe::BackwardsCompatible } ``` you currently get this compilation error: ``` error: attribute macro has missing stability attribute --> library/std/src/io/mod.rs:2269:1 | 2269 | #[eii(on_broken_pipe)] | ^^^^^^^^^^^^^^^^^^^^-- | | | in this attribute macro expansion | ::: library/core/src/macros/mod.rs:1899:5 | 1899 | pub macro eii($item:item) { | ------------- in this expansion of `#[eii]` ``` because with ` MAGIC_EXTRA_RUSTFLAGS=-Zunpretty=expanded ./x build library/std` we can see that a pub item in the expanded code is indeed missing that attribute: ```rs const _: () = { #[on_broken_pipe] fn on_broken_pipe() -> OnBrokenPipe { OnBrokenPipe::BackwardsCompatible } }; unsafe extern "Rust" { /// Foo #[unstable(feature = "on_broken_pipe", issue = "150588")] #[rustc_eii_extern_item] pub safe fn on_broken_pipe() -> OnBrokenPipe; } #[rustc_builtin_macro(eii_shared_macro)] #[eii_extern_target(on_broken_pipe)] pub macro on_broken_pipe { () => {} } ``` ## The Solution With the fix, that error goes away because we get this expanded code instead: ```rs const _: () = { #[on_broken_pipe] fn on_broken_pipe() -> OnBrokenPipe { OnBrokenPipe::BackwardsCompatible } }; unsafe extern "Rust" { /// Foo #[unstable(feature = "on_broken_pipe", issue = "150588")] #[rustc_eii_extern_item] pub safe fn on_broken_pipe() -> OnBrokenPipe; } /// Foo #[unstable(feature = "on_broken_pipe", issue = "150588")] #[rustc_builtin_macro(eii_shared_macro)] #[eii_extern_target(on_broken_pipe)] pub macro on_broken_pipe { () => {} } ``` Note that we also need to forward the docs, otherwise get get (fatal) warnings like these: ``` warning: missing documentation for an attribute macro --> library/std/src/io/mod.rs:2269:1 ``` r? @jdonszelmann Tracking issues: - https://github.com/rust-lang/rust/issues/125418 - https://github.com/rust-lang/rust/issues/150588 ### What about a test? https://github.com/rust-lang/rust/pull/150591 will prevent regressions once it lands since it does not build without this fix. I think it is overkill to add a temporary eii to std before that.