can't use unexported struct fields when converting using gno2go

[thehowl]

This happens mostly when doing a "gonative" call, such as is the case for (testing.T).Log, or more generally fmt.Sprintf.

package main

import "fmt"

type X struct {
        v string
}

func main() {
        fmt.Printf("test %#v", X{v: "a"})
}

$ gno run a.gno
panic running expression main(): reflect: reflect.Value.SetString using value obtained using unexported field

My opinion is that in the long run we should aim to drop all the gonative opcodes and code; it appears to me that gonative is mostly especially useful for "bootstrapping" functions in Gno, and is currently still useful mostly for functions like fmt.Sprintf, which would need to rely on reflection to work as expected.

However, to support use cases (such as mine, where I was trying to simply t.Log a struct) we may add a temporary fix to the problem.

On the patch/gnochess branch, I changed this line to make the struct field exported. This is a dirty trick, but it does the job:

$ gno run a.gno
test struct { Xv string }{Xv:"a"}%

Should a fix like this one be added to the main branch?