范围中的类型重新声明顺序是否应受外部范围影响？

Question

I got a strange error message cannot use []feed literal (type []feed) as type []feed in field value and after some fiddling and minimizing the source I figured out that this situation seems to produce the error:

type user struct {
    Feeds []feed
}
type feed struct{}

func fn() {
    type user struct {
        Feeds []feed // seems to refer to the outer feed type
    }
    type feed struct{}

    _ = user{
        // "cannot use []feed literal (type []feed) as type []feed in field value"
        Feeds: []feed{},
    }
}

http://play.golang.org/p/gNIGhPwAgl

Is this the intended behaviour or a bug? I've spend some time reading the language specification but can't find anything explicitly stating how type declaration order in scopes should work. It's a bit unintuitive that order does not matter in the outer scope but does in the inner.

Answer 1

This is so by the language spec.

Quoting the relevant part: Declarations and scope:

The scope of a type identifier declared inside a function begins at the identifier in the TypeSpec and ends at the end of the innermost containing block.

Types declared inside a function are only in scope from the type identifier (being declared). Before that they are not.

type user struct {
    Feeds []feed // This can only be the outer feed type
}

type feed struct{} // new feed type is in scope from this line