`using _: T` fields will now have their members unmarshalled to their
parent types reflecting the new behaviour of json.marshall.
Example:
```go
A :: struct {
using _: B,
}
B :: struct {
field: string,
}
data := `{"field": "Hello World"}`
a: A
json.unmarshal_string(data, &a)
```
marshalled directly into the parent type without an '"_":{ ... }'.
This seems like desirable behavior to me, since you can't access the
fields with 'Parent_Type._.field' either.
Franz Hoeltermann