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rustc_on_unimplemented: introduce format specifiers#156161

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mejrs wants to merge 1 commit intorust-lang:mainfrom
mejrs:this_formatargs
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rustc_on_unimplemented: introduce format specifiers#156161
mejrs wants to merge 1 commit intorust-lang:mainfrom
mejrs:this_formatargs

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@mejrs mejrs commented May 4, 2026

...as printing options for the annotated item.

See also the test and dev guide prose. This only affects rustc_on_unimplemented, not (yet) the other diagnostic attributes. I plan to do that in some later PR.

#![feature(rustc_attrs)]

#[rustc_on_unimplemented(
    message = "normal: {This}, path: {This:path},  resolved: {This:resolved}"
)]
pub trait Trait<'lifetime, const CONST_GENERIC: usize, A, B> where A: Send {}

will do:

normal: Trait, path: Trait<'lifetime, CONST_GENERIC, A, B>,  resolved: Trait<'_, 6, u8, _>

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rustbot commented May 4, 2026

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

The rustc-dev-guide subtree was changed. If this PR only touches the dev guide consider submitting a PR directly to rust-lang/rustc-dev-guide otherwise thank you for updating the dev guide with your changes.

cc @BoxyUwU, @tshepang

Some changes occurred in compiler/rustc_hir/src/attrs

cc @jdonszelmann, @JonathanBrouwer

@rustbot rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) A-rustc-dev-guide Area: rustc-dev-guide S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels May 4, 2026
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rustbot commented May 4, 2026

r? @dingxiangfei2009

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@mejrs mejrs removed the T-libs Relevant to the library team, which will review and decide on the PR/issue. label May 4, 2026
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@mejrs mejrs force-pushed the this_formatargs branch from d3030bc to 008ea3a Compare May 5, 2026 16:26
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A-attributes Area: Attributes (`#[…]`, `#![…]`) A-rustc-dev-guide Area: rustc-dev-guide S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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