反映：是否有可能获取基础类型类型信息？

Question

I'm porting a program from go/ast to reflect. In order to pass the tests I need to get not only the top type information but also the underlying type if the underlying type is not built-in.

In the example below, is it possible for a program to know that the underlying type of main.T is main.TT?

package main

import "fmt"
import "reflect"

func main() {
    type TT int
    type T TT

    x := T(0)
    fmt.Println(reflect.TypeOf(x))
}

Output:

 main.T

Answer 1

The underlying type of main.T is int, not main.TT. The reflect package has no knowledge that main.T was declared with main.TT.

Here's what the specification has to say about underlying types:

Each type T has an underlying type: If T is one of the predeclared boolean, numeric, or string types, or a type literal, the corresponding underlying type is T itself. Otherwise, T's underlying type is the underlying type of the type to which T refers in its type declaration.

type T1 string
type T2 T1
type T3 []T1
type T4 T3

The underlying type of string, T1, and T2 is string. The underlying type of []T1, T3, and T4 is []T1.