X-id is an identifier with no context-dependent meaning (e.g. qualified-id).
X-id is an identifier with no context-dependent meaning (e.g. qualified-id).
某标识表示上下文无关的标识符（比如限定标识）。
X-id is an identifier with no context-dependent meaning (e.g. qualified-id).
某标识表示上下文无关的标识符（比如限定标识）。