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?

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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