附：关键字列表 关键字：https://doc.rust-lang.org/reference/keywords.html
! const
- 常量名一般使用大写字母。
- 常量的定义关键字是 const，而不是let。
- 定义常量的时候必须指定数据类型。
- 不允许有同名的常量。
- variable 可以被 shadowing，constant 不能被 shadowing。
! trait
特性（trait）概念接近于Java中的接口（Interface），但两者不完全相同。trait与interface相同的地方在于它们都是一种行为规范，可以用于标识哪些类有哪些方法。
当前在用的关键字
as - perform primitive casting, disambiguate the specific trait containing an item, or rename items in use and extern crate statements async - return a Future instead of blocking the current thread await - suspend execution until the result of a Future is ready break - exit a loop immediately const - define constant items or constant raw pointers continue - continue to the next loop iteration crate - link an external crate or a macro variable representing the crate in which the macro is defined dyn - dynamic dispatch to a trait object else - fallback for if and if let control flow constructs enum - define an enumeration extern - link an external crate, function, or variable false - Boolean false literal fn - define a function or the function pointer type for - loop over items from an iterator, implement a trait, or specify a higher-ranked lifetime if - branch based on the result of a conditional expression impl - implement inherent or trait functionality in - part of for loop syntax let - bind a variable loop - loop unconditionally match - match a value to patterns mod - define a module move - make a closure take ownership of all its captures mut - denote mutability in references, raw pointers, or pattern bindings pub - denote public visibility in struct fields, impl blocks, or modules ref - bind by reference return - return from function Self - a type alias for the type we are defining or implementing self - method subject or current module static - global variable or lifetime lasting the entire program execution struct - define a structure super - parent module of the current module trait - define a trait true - Boolean true literal type - define a type alias or associated type union - define a union and is only a keyword when used in a union declaration unsafe - denote unsafe code, functions, traits, or implementations use - bring symbols into scope where - denote clauses that constrain a type while - loop conditionally based on the result of an expression
将来要用的关键字 abstract become box do final macro override priv try typeof unsized virtual yield