问题描述
限时送ChatGPT账号..此代码:
pub type Foo<T: Read> = fn(bar: T);
产生 错误 E0122(在较新版本的Rust,这只是一个警告):
yields error E0122 (in newer versions of Rust, it is only a warning):
已尝试向类型别名添加通用约束.这个约束完全被忽略.为了向后兼容,Rust仍然允许此警告.考虑以下示例:
An attempt was made to add a generic constraint to a type alias. This constraint is entirely ignored. For backwards compatibility, Rust still allows this with a warning. Consider the example below:
trait Foo {}
type MyType<R: Foo> = (R, ());
fn main() {
let t: MyType<u32>;
}
我们可以声明一个 MyType
类型的变量,尽管事实上u32
没有实现 Foo
.因此,应避免使用与类型别名一致的通用约束.
We're able to declare a variable of type MyType<u32>
, despite the fact
that u32
does not implement Foo
. As a result, one should avoid using
generic constraints in concert with type aliases.
是否可以创建一个包含对函数指针的特征要求的类型别名?显然,编译器告诉我没有类型,但不知道是否还有其他我没有想到的函数选项.
Is it possible to create a type alias that contains trait requirements on a function pointer? Obviously the compiler is telling me no for types, but didn't know if there was another option for functions that I wasn't thinking of.
推荐答案
目前看来不可能,也没有解决方法.
At this time, it does not seem to be possible and no workarounds exist.
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