no_mangle_const_items: const -> pub static suggestion causes syntax error #149511
Description
Using the following flags
--force-warn no_mangle_const_items
this code:
//! Test that nonsense bounds prevent consts from being evaluated at all. //@ check-pass #![feature(generic_const_items)] #![allow(incomplete_features)] trait Trait { const ASSOC: u32; } // rustfmt eats the where bound #[unsafe(no_mangle)] const ASSOC: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait; fn main() {}caused the following diagnostics:
Checking _23d74b92f51a14cefeb40f5cad7a397b39971b5d v0.1.0 (/tmp/icemaker_global_tempdir.fzTw1TOrsbiL/icemaker_clippyfix_tempdir.xP3b20GgdVBR/_23d74b92f51a14cefeb40f5cad7a397b39971b5d) warning: const items should never be `#[no_mangle]` --> src/main.rs:12:1 | 12 | const ASSOC: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait; | -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | | | help: try a static value: `pub static` | = note: requested on the command line with `--force-warn no-mangle-const-items` warning: `_23d74b92f51a14cefeb40f5cad7a397b39971b5d` (bin "_23d74b92f51a14cefeb40f5cad7a397b39971b5d") generated 1 warning (run `cargo clippy --fix --bin "_23d74b92f51a14cefeb40f5cad7a397b39971b5d" -p _23d74b92f51a14cefeb40f5cad7a397b39971b5d` to apply 1 suggestion) Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.21s However after applying these diagnostics, the resulting code:
//! Test that nonsense bounds prevent consts from being evaluated at all. //@ check-pass #![feature(generic_const_items)] #![allow(incomplete_features)] trait Trait { const ASSOC: u32; } // rustfmt eats the where bound #[unsafe(no_mangle)] pub static ASSOC: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait; fn main() {}no longer compiled:
Checking _23d74b92f51a14cefeb40f5cad7a397b39971b5d v0.1.0 (/tmp/icemaker_global_tempdir.fzTw1TOrsbiL/icemaker_clippyfix_tempdir.xP3b20GgdVBR/_23d74b92f51a14cefeb40f5cad7a397b39971b5d) error: expected one of `!`, `.`, `::`, `;`, `?`, `{`, or an operator, found keyword `where` --> src/main.rs:12:46 | 12 | pub static ASSOC: u32 = <&'static ()>::ASSOC where for<'a> &'a (): Trait; | ^^^^^ expected one of 7 possible tokens error: could not compile `_23d74b92f51a14cefeb40f5cad7a397b39971b5d` (bin "_23d74b92f51a14cefeb40f5cad7a397b39971b5d") due to 1 previous error warning: build failed, waiting for other jobs to finish... error: could not compile `_23d74b92f51a14cefeb40f5cad7a397b39971b5d` (bin "_23d74b92f51a14cefeb40f5cad7a397b39971b5d" test) due to 1 previous error Version:
rustc 1.93.0-nightly (f40a70d2b 2025-11-30) binary: rustc commit-hash: f40a70d2bcd830a4f1f8c7ca1a7f93f1d9d703d6 commit-date: 2025-11-30 host: x86_64-unknown-linux-gnu release: 1.93.0-nightly LLVM version: 21.1.5 Metadata
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Area: Messages for errors, warnings, and lintsArea: Suggestions generated by the compiler applied by `cargo fix`Diagnostics: A structured suggestion resulting in incorrect code.Call for participation: Easy difficulty. Experience needed to fix: Not much. Good first issue.`#![feature(generic_const_items)]`Relevant to the compiler team, which will review and decide on the PR/issue.