Context: I'm generating code (from a macro) that spits out new types. Of course, I don't have access to type information in my macro. I want my typeNewStruct(which I've generated) to implement a trait (sayCondition) if and only ifStruct(which passed as argument to the macro)...
fnmain() {//Drops immediately; 立即Droplet_= String::from("Not bind to anything");//Copy types; 整型实现了Copy traitleta=10;//implicitly cloned; 隐式clonedletb= a;//explicitly cloned; 显式clonedletc= b.clone();//This code wouldn't compile if they were move types//如果是move类型的...
Trait 项是指包含于 trait 声明中的任意项。 Self Self总是指代实现类型。 traitTrait{// always returns i32fnreturns_num()->i32;// returns implementing typefnreturns_self()->Self; }structSomeType;structOtherType;implTraitforSomeType{fnreturns_num()->i32{5}// Self == SomeTypefnreturns_self()...
("{}", s);// | ^ value used here after move// |// = note: move occurs because `s` has type `std::string::String`, which does not// implement the `Copy` trait 这种直接赋值的方式在大多数语言中非常常见,但是在Rust中不行。因为它需要保证全程只有一个变量引用这块内存。 所有权还有一个...
("{}", s);// | ^ value used here after move// |// = note: move occurs because `s` has type `std::string::String`, which does not// implement the `Copy` trait 这种直接赋值的方式在大多数语言中非常常见,但是在Rust中不行。因为它需要保证全程只有一个变量引用这块内存。
let number = if flag { 5 } else { "six" }; // 错误:不匹配的类型 } 解决方案:确保所有的分支返回相同的类型。 let number = if flag { 5 } else { 6 }; 忘记导入trait: use std::io::Write; // 因为 Write trait 已导入 fn main() { ...
I don't want to implement theCommonFunctionalityfor every actual struct that I write. So I had the idea using a super-trait in a library. Every actual struct implementation that implementsSpecialFunctionality1orSpecialFunctionality2could get theCommonFunctionalitywithout any additional code. Unfortunately...
("{0}, in binary: {0:b}, in hexadecimal: {0:x}", 11);// debug trait (very useful to print anything)// if you try to print the array directly, you will get an error// because an array is not a string or number typeprintln!("{:?}", [11, 22, 33]);}运行代码查看输出：...
= help: the following other types implement trait `Add<Rhs>`: `&'a i8` implements `Add<i8>` `&i8` implements `Add<&i8>` `i8` implements `Add<&i8>` `i8` implements `Add` 很好!实际上,这个错误消息意味着 Rust 不理解如何添加i8和Option<i8>,因为它们是不同的类型。当我们在 Rust 中有...
I guess this feature should be implemented based onTyCtxt::type_implements_trait. But I have some trouble to get the DefId of a trait from a string. Only "function call" and "method call" pattern are implemented in the condition;