attr-bounds

一个指定边界的属性宏。

该属性将边界应用于结构体、枚举、联合、特质、函数和impl块。

use attr_bounds::bounds;

#[bounds(T: Copy)]
pub struct Wrapper<T>(T);

let var = Wrapper(42);

使用说明

基本上，该属性是为了条件编译而设计的，否则您不需要该属性。

use attr_bounds::bounds;

#[cfg(feature = "unstable_feature_a")]
pub trait UnstableA {}
#[cfg(feature = "unstable_feature_b")]
pub trait UnstableB {}

#[cfg_attr(feature = "unstable_feature_a", bounds(Self: UnstableA))]
#[cfg_attr(feature = "unstable_feature_b", bounds(Self: UnstableB))]
pub trait Trait {}

#[cfg(feature = "unstable_feature_a")]
impl UnstableA for () {}
#[cfg(feature = "unstable_feature_b")]
impl UnstableB for () {}

impl Trait for () {}

lib.rs:

一个指定边界的属性宏。

该属性将边界应用于结构体、枚举、联合、特质、函数、关联类型和impl块。

use attr_bounds::bounds;

#[bounds(T: Copy)]
pub struct Wrapper<T>(T);

let var = Wrapper(42);

use attr_bounds::bounds;

#[bounds(T: Copy)]
pub struct Wrapper<T>(T);

let var = Wrapper(Vec::<i32>::new());
//                ^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `Vec<i32>`

使用说明

基本上，该属性是为了条件编译而设计的，否则您不需要该属性。

use attr_bounds::bounds;

#[cfg(feature = "unstable_feature_a")]
pub trait UnstableA {}
#[cfg(feature = "unstable_feature_b")]
pub trait UnstableB {}

#[cfg_attr(feature = "unstable_feature_a", bounds(Self: UnstableA))]
#[cfg_attr(feature = "unstable_feature_b", bounds(Self: UnstableB))]
pub trait Trait {}

#[cfg(feature = "unstable_feature_a")]
impl UnstableA for () {}
#[cfg(feature = "unstable_feature_b")]
impl UnstableB for () {}

impl Trait for () {}