{"ast_node_type":"other","tokens":[{"end":66,"kind":"keyword","start":0,"text":"///"}]}
///    or `#[cfg_attr]`, we replace the entire inner AST node with
///    `#[derive]` attribute, when we parse a nested AST node that has `#[cfg]`
///    `FlatToken::AttrsTarget`. This lets us perform eager cfg-expansion on an