Rust 元组类型索引

提供了一个特性 TypeAt，允许在编译时查询 Rust 元组的第 n 个类型。

示例：简单

use type_at::TypeAt;

let _: i8  = <(i8, i16, i32, i64) as TypeAt<0>>::Type::default();
let _: i16 = <(i8, i16, i32, i64) as TypeAt<1>>::Type::default();
let _: i32 = <(i8, i16, i32, i64) as TypeAt<2>>::Type::default();
let _: i64 = <(i8, i16, i32, i64) as TypeAt<3>>::Type::default();

示例：嵌套

use type_at::TypeAt;

let _: i64 = <<<<(i8, (i16, (i32, (i64,))))
    as TypeAt<1>>::Type // (i16, (i32, (i64,)))
    as TypeAt<1>>::Type // (i32, (i64,))
    as TypeAt<1>>::Type // (i64,)
    as TypeAt<0>>::Type::default();

示例：派生

#[derive(TypeAt)]
pub struct TupleStruct(i8, i16, i32);

let _: i8   = <TupleStruct as TypeAt<0>>::Type::default();
let _: i16  = <TupleStruct as TypeAt<1>>::Type::default();
let _: i32  = <TupleStruct as TypeAt<2>>::Type::default();

#[derive(TypeAt)]
pub struct Struct { a: i8, b: i16, c: i32 }

let _: i8   = <Struct as TypeAt<0>>::Type::default();
let _: i16  = <Struct as TypeAt<1>>::Type::default();
let _: i32  = <Struct as TypeAt<2>>::Type::default();

许可协议

许可协议为以下之一

• Apache 许可证，版本 2.0，(LICENSE-APACHE 或 https://apache.ac.cn/licenses/LICENSE-2.0)
• MIT 许可证 (LICENSE-MIT 或 http://opensource.org/licenses/MIT)

由您选择。

双许可：[![徽章][license-mit-badge]][license-mit-badge] ![徽章][license-apache-badge] ![徽章][license-apache-badge]

贡献

除非您明确声明，否则任何有意提交以包含在作品中的贡献，根据 Apache-2.0 许可证定义，将按以下方式双许可，没有任何额外的条款或条件。