error[E0121]: the placeholder `_` is not allowed within types on item signatures for constants --> $DIR/issue-104768.rs:1:10 | LL | const A: &_ = 0_u32; | ^^ | | | not allowed in type signatures | help: replace with the correct type: `u32` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0121`.