为什么 Go 编译器不能推断出一个结构实现了一个接口

Question

运行下面的代码会导致编译错误：

cannot use authors (type []Person) as type []Namer in return argument

为什么Go编译不了？

type Namer interface {
    Name() string
}

type Person struct {
    name string
}

func (r Person) Name() string {
    return r.name
}

func Authors() []Namer {
    // One or the other is used - both are not good:
    authors := make([]Person, 10)
    var authors []Person

    ...

    return authors

将 authors 声明为 authors := make([]Namer, 10) 或 var authors []Namer 会很好，但我不明白为什么编译器不能推断 Person 是 Namer .

Answer 1

因为 []Person 不是 []Namer。让我们将您的示例更进一步：

type Namer interface {
    Name() string
}

type Person struct {
    name string
}

func (r Person) Name() string {
    return r.name
}

type Thing struct {
    name string
}

func (t Thing) Name() string {
    return r.name
}

func Authors() []Namer {
    authors := make([]Person, 10)
    return authors
}

func main() {
    namers := Authors()
    // Great! This gives me a []Namer, according to the return type, I'll use it that way!
    thing := Thing{}
    namers := append(namers, thing)
    // This *should* work, because it's supposed to be a []Namer, and Thing is a Namer.
    // But you can't put a Thing in a []Person, because that's a concrete type.
}

如果代码希望收到 []Namer，那就是它必须得到的。不是 []ConcreteTypeThatImplementsNamer - 它们不可互换。

为什么 Go 编译器不能推断出一个结构实现了一个接口

Why can't Go compiler deduce that a struct implements an interface

interface

go