YANG parser generates invalid code for compound data structures

[alexandergall]

Consider the schema

module yang-afi {
  namespace foo;
  prefix foo;
  
  import ietf-inet-types { prefix inet; }
  
  container address-families {
    presence "foo";
    container ipv4 {
      leaf address {
        type inet:ipv4-address;
        mandatory true;
      }
      leaf next-hop {
        type inet:ipv4-address;
        mandatory true;
      }
    }
    container ipv6 {
      presence "foo";
      leaf address {
        type inet:ipv6-address;
        mandatory true;
      }
      leaf next-hop {
        type inet:ipv6-address;
        mandatory true;
      }
    }
  }
}

This should create a container with two optional sub-containers which each contain two mandatory leafs (without presence, the ipv4 and ipv6 containers would be mandatory due to the mandatory ancestors).

Application of the schema to the data

address-families {
  ipv4 {
    address "10.0.0.1";
    next-hop "10.0.0.2";
  }
}

with

local yang = require("lib.yang.yang")

yang.add_schema_file("yang-afi.yang")
local config = yang.load_configuration("yang-afi.config", {  schema_name = "yang-afi" })

produces an internal error

ERROR: While parsing type:
ERROR:   struct { struct { struct { uint32_t address; uint32_t next_hop; } ipv4; struct { uint8_t address ipv6 address_families[16]; uint8_t next_hop[16]; }; }; }
ERROR:                                                                                                                                                         ^
ERROR: bad member name

Clearly, there should be the member name ipv6 included in this ctype definition.

I also suspect that even if the member name is produced correctly, this will actually create a parser for which both containers are mandatory, but I'm not sure about that.