Macro throw_invalid_attr 

macro_rules! throw_invalid_attr {
    ($attr:expr) => { ... };
    ($attr:expr, $f:expr) => { ... };
}

Emit an error diagnostic for an invalid attribute (optionally performing additional decoration using the FnOnce passed in diag) and return Err(ErrorHandled).

For methods that return a Result<_, DiagnosticDeriveError>: