{"ast_node_type":"other","tokens":[{"end":55,"kind":"keyword","start":0,"text":"BorrowedContentSource::DerefMutableRef"}]}
            BorrowedContentSource::DerefMutableRef => {
            BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
                bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")