Macro note 

macro_rules! note {
    ($($args:tt)+) => { ... };
}

Emit a note of kind NoteKind::Note with a formatted message.

Notes are meant to be attached to diagnostics, so one should be sure that a diagnostic (e.g., an error) has been emitted before emitting a note. Notes are used to provide additional information, possibly attached to different source spans, to a previously emitted diagnostic.

Example:

error!(span, "unable to parse identifier: {}", ident);
note!(span, "it seems to be a number instead");