Explicitly export core and std macros #139493
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r? @ChrisDenton rustbot has assigned @ChrisDenton. Use |
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r? @Amanieu |
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Amanieu
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Apr 7, 2025
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@Amanieu the tidy issue highlights an annoying and unforeseen side-effect of this change. The fn xx(i: vec::IntoIter<i32>) {
let _ = i.as_slice();
}
fn main() {}that currently doesn't compile on stable would now compile. Initially I thought this would cause name collisions if users define their own |
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There's an issue for this change - #53977. |
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@Voultapher, avoiding the vec module re-export can be done like this: #[macro_export]
macro_rules! myvec {
() => {};
}
pub mod myvec {
pub struct Vec;
}
pub mod prelude {
// Bad: re-exports both macro and type namespace
// pub use crate::myvec;
mod vec_macro_only {
#[allow(hidden_glob_reexports)]
mod myvec {}
pub use crate::*;
}
pub use self::vec_macro_only::myvec;
}
fn main() {
prelude::myvec!();
let _: prelude::myvec::Vec; // error
} |
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@Voultapher Based on the CI failure I think that a try build would fail now. |
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Ok, I'll try to get the CI passing first. |
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@petrochenkov I went through all macros and searched the docs and |
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@Amanieu this program previously worked: use std::*;
fn main() {
panic!("panic works")
}and now runs into: I don't see how we can resolve that without changing language import rules and or special casing the prelude import. |
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@petrochenkov Do you have any ideas about that? |
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Could you add a test making sure that the modules |
The ambiguity wouldn't happen if it was the same panic in std root and in the stdlib prelude. Previously |
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I'll try to get to it next week. |
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#![feature(custom_inner_attributes)]
#![rustfmt::skip]
use std::fmt::Debug;
fn in_parameters(_: impl Debug) { todo!() }
fn main() {}
EDIT: This is likely a red herring for another issue. Ignore it for now. |
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☔ The latest upstream changes (presumably #143057) made this pull request unmergeable. Please resolve the merge conflicts. |
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There was another issue with the alloctests, that I managed to resolve, the where-allowed and potentially unrelated |
Currently all core and std macros are automatically added to the prelude via #[macro_use]. However a situation arose where we want to add a new macro `assert_matches` but don't want to pull it into the standard prelude for compatibility reasons. By explicitly exporting the macros found in the core and std crates we get to decide on a per macro basis and can later add them via the rust_20xx preludes.
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Missing `#[doc(no_inline)]` for ambiguous_macro_only_std resulted in new and broken doc html files.
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cc @Amanieu, @folkertdev, @sayantn |
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The job Click to see the possible cause of the failure (guessed by this bot) |
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☔ The latest upstream changes (presumably #143357) made this pull request unmergeable. Please resolve the merge conflicts. |
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Currently all core and std macros are automatically added to the prelude via #[macro_use]. However a situation arose where we want to add a new macro
assert_matchesbut don't want to pull it into the standard prelude for compatibility reasons. By explicitly exporting the macros found in the core and std crates we get to decide on a per macro basis and can later add them via the rust_20xx preludes.Closes #53977
Unlocks #137487