What version of Go are you using (go version)?

go1.18.3

Does this issue reproduce with the latest release?

Unknown

What operating system and processor architecture are you using (go env)?

darwin/arm64

What did you do?

type ConstantValue struct {
Value constant.Value
}

func EnocdeDecodeRoundtrip(value ConstantValue) {
var b bytes.Buffer
e := gob.NewEncoder(&b)
if err := e.Encode(&value); err != nil {
panic(err)
}
var decodedValue ConstantValue
d := gob.NewDecoder(&b)
if err := d.Decode(&decodedValue); err != nil {
panic(err)
}
if value.Value.ExactString() != decodedValue.Value.ExactString() {
err := fmt.Errorf("Decoded value not the same as original. Expected %s, but got %s",
value.Value.ExactString(), decodedValue.Value.ExactString())
panic(err)
}
}

func TestConstantValueGobEncoding(t *testing.T) {
field := ConstantValue{constant.Make(int64(1))}
EnocdeDecodeRoundtrip(field)
}

What did you expect to see?

Expected to be able to encode and decode constant.Value

What did you see instead?

panic: gob: type not registered for interface: constant.int64Val

Workaround

I'm able to workaround the issue by creating a custom encoder, but it's a bit painful