{"ast_node_type":"function","tokens":[{"end":72,"kind":"keyword","start":0,"text":"fn"}]}
    fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>) {
impl Subdiagnostic for TypeMismatchFruTypo {
        diag.arg("expr", self.expr.as_deref().unwrap_or("NONE"));