如何强制特征的两个关联类型参数相等? [英] How can I enforce equality of two associated type parameters of traits?

问题描述

我有一个函数f，它接受两个相同类型的参数，一个函数g，它接受两个不同类型的参数，但是两种类型都必须存储相同的值，以便g可以调用f，其值包含在f的参数中.我目前实现了这样的内容:

I have a function f which takes two arguments of the same type, and a function g which takes two arguments of different types, but both types have to store the same value, so that g can call f with the values contained in the arguments to f. I currently implemented something like this:

fn f<T>(a: T, b: T) {}

trait A {
    type A;
    fn getter(&self) -> Self::A;
}

fn g<T: A, U: A>(a: T, b: U) {
    f(a.getter(), b.getter())
}

要使g的定义生效，我必须添加什么?

What do I have to add to the definition of g to make it work?

推荐答案

一个where子句可以正常工作:

A where clause works fine:

fn g<T, U>(a: T, b: U)
where
    T: A,
    U: A<A = T::A>, // where T::A is equal to B::A
{
    f(a.getter(), b.getter())
}

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