Golang 泛型：[type T]，为啥要用中括号呢。。。

传送门： https://blog.golang.org/generics-next-step

官方示例：

package main

import (
	"fmt"
)

// The playground now supports parentheses or square brackets (only one at
// a time) for generic type and function declarations and instantiations.
// By default, parentheses are expected. To switch to square brackets,
// the first generic declaration in the source must use square brackets.

func Print[type T](s []T) {
	for _, v := range s {
		fmt.Print(v)
	}
}

func main() {
	Print([]string{"Hello, ", "playground\n"})
}

High Level Overview：

• Functions can have an additional type parameter list introduced by the keyword type: func F(type T)(p T) { ... }.
• These type parameters can be used by the regular parameters and in the function body.
• Types can also have a type parameter list: type M(type T) []T.
• Each type parameter can have an optional type constraint: func F(type T Constraint)(p T) { ... }
• Type constraints are interface types.
• Interface types used as type constraints can have a list of predeclared types; only types whose underlying type is - one of those types can implement the interface.
• Using a generic function or type requires passing type arguments.
• Type inference permits omitting the type arguments in common cases.
• If a type parameter has a type constraint its type argument must implement the interface.
• Generic functions may only use operations permitted by the type constraint.