TODO: l4 should be allowed

-- in.cue --
#def1: l1: ["l2"]: {l3: int, l4: 26}
#special1: #def1     & {l1: l2: l3: <100}
instance:  #special1 & {l1: l2: l3: 34}
-- out/eval --
(struct){
  #def1: (#struct){
    l1: (#struct){
    }
  }
  #special1: (#struct){
    l1: (#struct){
      l2: (#struct){
        l3: (int){ &(<100, int) }
        l4: (int){ 26 }
      }
    }
  }
  instance: (#struct){
    l1: (#struct){
      l2: (#struct){
        l3: (int){ 34 }
        l4: (int){ 26 }
      }
    }
  }
}
-- out/compile --
--- in.cue
{
  #def1: {
    l1: {
      ["l2"]: {
        l3: int
        l4: 26
      }
    }
  }
  #special1: (〈0;#def1〉 & {
    l1: {
      l2: {
        l3: <100
      }
    }
  })
  instance: (〈0;#special1〉 & {
    l1: {
      l2: {
        l3: 34
      }
    }
  })
}