* `B` is a type meeting the requirements of [*Body]. * `m` is a value of type `message<b,B,F>` where `b` is a `bool` value
* `B` is a type meeting the requirements of [*Body]. * `m` is a value of type是一个满足 [*Body] 要求的类型。 * `m` 是类型为 `message<b,B,F>` where的值,其中 `b` is a为 `bool` value类型的值。
* `m` is a value of type `message<b,B,F>` where `b` is a `bool` value
is a type meeting the requirements of [*Body].是一个满足 [*Body] 要求的类型。* `m` is a value of type
* `m` 是类型为 `message<b,B,F>`
where的值,其中 `b`is a为 `bool`value类型的值。