Type Alias IDBoundAlloc 

pub type IDBoundAlloc<I> = EntityAlloc<<I as IPoliciedID>::ObjectT, <I as IPoliciedID>::PolicyT>;

Alias for EntityAlloc specialized to the object and policy types of an ID.

常用作函数签名中把 ID 与对应的 EntityAlloc 进行绑定，避免每次都写出复杂的关联类型。

Aliased Type

pub struct IDBoundAlloc<I> { /* private fields */ }