{"ast_node_type":"other","tokens":[{"end":74,"kind":"keyword","start":0,"text":"///"}]}
    /// but this hook allows e.g. codegen to return only `&FnAbi` from its
    /// Most `impl`s, which propagate `FnAbiError`s, should simply return `err`,
    /// `cx.fn_abi_of_*(...)`, without any `Result<...>` around it to deal with