| warning: crate-level attribute should be an inner attribute: add an exclamation mark: `#![foo]` | 
 |   --> $DIR/linker-warning.rs:7:1 | 
 |    | | 
 | LL | #[allow(linker_messages)] | 
 |    | ^^^^^^^^^^^^^^^^^^^^^^^^^ | 
 |    | | 
 | note: the lint level is defined here | 
 |   --> $DIR/linker-warning.rs:3:9 | 
 |    | | 
 | LL | #![warn(unused_attributes)] | 
 |    |         ^^^^^^^^^^^^^^^^^ | 
 |  | 
 | warning: unused attribute | 
 |   --> $DIR/linker-warning.rs:4:1 | 
 |    | | 
 | LL | #![allow(linker_messages)] | 
 |    | ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove this attribute | 
 |    | | 
 |    = note: the `linker_messages` lint can only be controlled at the root of a crate that needs to be linked | 
 |  | 
 | warning: 2 warnings emitted | 
 |  |