T.43: Prefer using over typedef for defining aliases
T.43: 定义别名时，using比typedef更好
Reason（原因）
Improved readability: With using, the new name comes first rather than being embedded somewhere in a declaration. Generality: using can be used for template aliases, whereas typedefs can't easily be templates. Uniformity: using is syntactically similar to auto.
提高可读性：使用using，新名称最先出现，而不是嵌入在声明的某个地方。通用性：using可以用于模板别名，然而typedef无法简单地用于模板。统一性：using在句法上和auto相似。
Example（示例）
代码语言：javascript复制typedef int (*PFI)(int); // OK, but convoluted
using PFI2 = int (*)(int); // OK, preferred
template<typename T>
typedef int (*PFT)(T); // error
template<typename T>
using PFT2 = int (*)(T); // OK
Enforcement（实施建议）
- Flag uses of typedef. This will give a lot of "hits" :-(
- 标记使用typedef的地方。会有发现大量使用typedef的代码:-(
原文链接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#t42-use-template-aliases-to-simplify-notation-and-hide-implementation-details
