Unexpected undefined result and evaluation error

[tsandall]

Minimal example policy:

package ex

a = "a"
b = "b"

x = "x"
y = "y"

o[a] = {
    x: "foo"
}

o[b] = {
    y: "bar"
}

Queries:

# OK
> data.ex.o
{
  "a": {
    "x": "foo"
  },
  "b": {
    "y": "bar"
  }
}

#OK
> data.ex.o.a
{
  "x": "foo"
}

#Should be "foo"
> data.ex.o.a.x
undefined

#OK
> data.ex.o[i]
+-----+--------------+
|  i  | data.ex.o[i] |
+-----+--------------+
| "a" | {"x":"foo"}  |
| "b" | {"y":"bar"}  |
+-----+--------------+

#Unexpected error
> data.ex.o[i][j]
value requires evaluation (ast.Var)