go - Go 1.18 中的 "any"类型是什么？

Question

在 Visual Studio Code 中，自动完成工具(我猜是 gopls？)提供以下模板:

m.Range(func(key, value any) bool {
    
})

其中 m 是一个 sync.Map。类型 any 无法识别，但会放在那里。

什么是any？我可以放我想要的类型并希望 Go 1.18 为我做隐式类型转换吗？例如:

m.Range(func(k, v string) { ... })

这将在回调中将 k、v 作为字符串，而无需自己进行类型转换？

Answer 1

any 是一个新的 predeclared identifier和 interface{} 的类型别名。

来自issue 49884 , CL 368254和 commit 2580d0e .

问题提到了关于interface{}/any:

It's not a special design, but a logical consequence of Go's type declaration syntax.

You can use anonymous interfaces with more than zero methods:

func f(a interface{Foo(); Bar()}) {
   a.Foo()
   a.Bar()
}

Analogous to how you can use anonymous structs anywhere a type is expected:

func f(a struct{Foo int; Bar string}) {
   fmt.Println(a.Foo)
   fmt.Println(a.Bar)
}

An empty interface just happens to match all types because all types have at least zero methods.
Removing interface{} would mean removing all interface functionality from the language if you want to stay consistent / don't want to introduce a special case.