特质可以有一个由泛型参数化的超特质吗? [英] Can a trait have a supertrait that is parameterized by a generic?
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问题描述
你能在 Rust 中做这样的事情吗?
Can you do something like this in Rust?
trait A : forall<T> B<T> { ... }
也就是说,如果我们想要:
That is, if we want:
impl A for D { ... }
首先要实现:
impl<T> B<T> for D { ... }
推荐答案
没有.Rust 的类型系统目前不支持任何涉及更高级类型的特性.但是,它确实支持与您所描述的类似的构造,但仅限于生命周期参数.例如:
No. Rust's type system doesn't currently support any features involving higher kinded types. It does, however, support a similar construction to what you described, but limited to lifetime parameters. For example:
trait B<'a> {}
trait A: for<'a> B<'a> {}
struct D;
impl A for D { }
这是一个错误:
error[E0277]: the trait bound `for<'a> D: B<'a>` is not satisfied
--> src/lib.rs:7:6
|
7 | impl A for D { }
| ^ the trait `for<'a> B<'a>` is not implemented for `D`
直到您添加一揽子实现:
Until you add the blanket implementation:
impl<'a> B<'a> for D { }
<小时>
Rust 最终也会为类型添加类似的功能并非不可能,但我预计不会很快.
It's not impossible that Rust will eventually add similar functionality for types too, but I wouldn't expect it any time soon.
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