Function rustc_interface::callbacks::track_diagnostic

fn track_diagnostic<R>(
    diagnostic: DiagInner,
    f: &mut dyn FnMut(DiagInner) -> R,
) -> R

This is a callback from rustc_errors as it cannot access the implicit state in rustc_middle otherwise. It is used when diagnostic messages are emitted and stores them in the current query, if there is one.