Rust error E0788: #### Note: this error code is no longer emitted by the compiler

The compiler team's explanation

Note: this error code is no longer emitted by the compiler.

A #[coverage(off|on)] attribute was found in a position where it is not allowed.

Coverage attributes can be applied to:

• Function and method declarations that have a body, including trait methods that have a default implementation.
• Closure expressions, in situations where attributes can be applied to expressions.
• impl blocks (inherent or trait), and modules.

Example of erroneous code:

unsafe extern "C" {
    #[coverage(off)]
    fn foreign_fn();
}

When using the -C instrument-coverage flag, coverage attributes act as a hint to the compiler that it should instrument or not instrument the corresponding function or enclosed functions. The precise effect of applying a coverage attribute is not guaranteed and may change in future compiler versions.

From rustc --explain E0788 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.