go - Custom type passed to function as a parameter

Question

When I define a custom type, it seems that the type of the underlying type makes a difference about whether I can pass it to a function as is or I need to convert it.

Question is: Why does RuneFunc and StringMap work, but not Integer?

https://play.golang.org/p/buKNkrg5y-

package main


type RuneFunc func(rune) rune
type Integer int
type StringMap map[string]string

func main() {
    //m := make(StringMap)
    //mf(m)


    var i Integer = 5
    nf(i)


    //var f func(rune) rune
    //ff(f) 

}

func mf(i map[string]string) {

}
func ff(i func(rune)rune) {

}
func nf(i int) {

}

Here, when I run this function called nf with Integer it complains although int is the underlying type. But when I call mf or ff they run successfully.

Answer 1

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